Jeep Toad
09-08-2006, 06:26 PM
#231
Guest
Posts: n/a
Re: Jeep Toad
That is so.... WRONG it's overwhelming! So I'll just eliminate the
maxies, for the others that may believe in this group, They use air
pressure to release the parking brakes they are not used in stopping! I
think that most people could tell by the number of gauges we have to
monitor that if a part like disk brakes could be used safely we would
have them on our half a million dollar tractors:
http://www.----------.com/kenworthdash.jpg
God Bless America, Bill O|||||||O
mailto:--------------------
Simon Juncal wrote:
>
> mabar wrote:
> > So far in this thread, nobody has answered Jeff's question: Why do
> > semi-trucks use drum brakes?
> >
> > I also am curious - why do they use drums rather than disks?
>
> This is one of those questions that has a bunch of answers which are all
> more or less true.
>
> Because the industry is traditional and doesn't like change, because
> drums perform on Semi's pretty well in an overall sense, because
> changing to discs requires a lot of new technology and new untested (in
> trucking) systems which can fail until the bugs are worked out causing
> law suits. In short because the industry is cheap and as stubborn as
> Bill about adapting to new stuff.
>
> Probably the major reason (and long winded one) though is mechanical;
> Because air brake systems works backwards from how we are used to brakes
> working...
>
> The default state on a semi's brake system is LOCKED UP... Unlike
> hydrolic systems where a lack of fluid will result in NO BRAKES, a lack
> of air will result in total brakes. This is because air is used to push
> against the heavy springs that are ALWAYS trying to push the brake shoes
> against the drums. The air is used to compress these springs.
>
> The mechanical advantage here is that in emergencies Semi's have brakes
> even without a running motor OR air in the system. With no motor you can
> still lightly brake a Semi to a safe stop. With no air it will come to a
> more or less screeching halt, but at least it will stop.
>
> The same could certainly be done using discs but would require a system
> that is very different from our cars discs and thus lots of R&D dollars.
> Drums have almost no advantages over discs, they are FAR heavier, FAR
> less thermally efficient, they trap water, and heat, they have LESS
> friction surface until they are just about locked up. and they use WAY
> WAY more parts, they are manually adjusted (even automatic slack
> adjusters must be manually adjusted occasionally!)
>
> You asked :)
> --
> Simon
> "I may be wrong, but I'm not uncertain." -- Robert A. Heinlein
maxies, for the others that may believe in this group, They use air
pressure to release the parking brakes they are not used in stopping! I
think that most people could tell by the number of gauges we have to
monitor that if a part like disk brakes could be used safely we would
have them on our half a million dollar tractors:
http://www.----------.com/kenworthdash.jpg
God Bless America, Bill O|||||||O
mailto:--------------------
Simon Juncal wrote:
>
> mabar wrote:
> > So far in this thread, nobody has answered Jeff's question: Why do
> > semi-trucks use drum brakes?
> >
> > I also am curious - why do they use drums rather than disks?
>
> This is one of those questions that has a bunch of answers which are all
> more or less true.
>
> Because the industry is traditional and doesn't like change, because
> drums perform on Semi's pretty well in an overall sense, because
> changing to discs requires a lot of new technology and new untested (in
> trucking) systems which can fail until the bugs are worked out causing
> law suits. In short because the industry is cheap and as stubborn as
> Bill about adapting to new stuff.
>
> Probably the major reason (and long winded one) though is mechanical;
> Because air brake systems works backwards from how we are used to brakes
> working...
>
> The default state on a semi's brake system is LOCKED UP... Unlike
> hydrolic systems where a lack of fluid will result in NO BRAKES, a lack
> of air will result in total brakes. This is because air is used to push
> against the heavy springs that are ALWAYS trying to push the brake shoes
> against the drums. The air is used to compress these springs.
>
> The mechanical advantage here is that in emergencies Semi's have brakes
> even without a running motor OR air in the system. With no motor you can
> still lightly brake a Semi to a safe stop. With no air it will come to a
> more or less screeching halt, but at least it will stop.
>
> The same could certainly be done using discs but would require a system
> that is very different from our cars discs and thus lots of R&D dollars.
> Drums have almost no advantages over discs, they are FAR heavier, FAR
> less thermally efficient, they trap water, and heat, they have LESS
> friction surface until they are just about locked up. and they use WAY
> WAY more parts, they are manually adjusted (even automatic slack
> adjusters must be manually adjusted occasionally!)
>
> You asked :)
> --
> Simon
> "I may be wrong, but I'm not uncertain." -- Robert A. Heinlein
09-08-2006, 06:26 PM
#232
Guest
Posts: n/a
Re: Jeep Toad
That is so.... WRONG it's overwhelming! So I'll just eliminate the
maxies, for the others that may believe in this group, They use air
pressure to release the parking brakes they are not used in stopping! I
think that most people could tell by the number of gauges we have to
monitor that if a part like disk brakes could be used safely we would
have them on our half a million dollar tractors:
http://www.----------.com/kenworthdash.jpg
God Bless America, Bill O|||||||O
mailto:--------------------
Simon Juncal wrote:
>
> mabar wrote:
> > So far in this thread, nobody has answered Jeff's question: Why do
> > semi-trucks use drum brakes?
> >
> > I also am curious - why do they use drums rather than disks?
>
> This is one of those questions that has a bunch of answers which are all
> more or less true.
>
> Because the industry is traditional and doesn't like change, because
> drums perform on Semi's pretty well in an overall sense, because
> changing to discs requires a lot of new technology and new untested (in
> trucking) systems which can fail until the bugs are worked out causing
> law suits. In short because the industry is cheap and as stubborn as
> Bill about adapting to new stuff.
>
> Probably the major reason (and long winded one) though is mechanical;
> Because air brake systems works backwards from how we are used to brakes
> working...
>
> The default state on a semi's brake system is LOCKED UP... Unlike
> hydrolic systems where a lack of fluid will result in NO BRAKES, a lack
> of air will result in total brakes. This is because air is used to push
> against the heavy springs that are ALWAYS trying to push the brake shoes
> against the drums. The air is used to compress these springs.
>
> The mechanical advantage here is that in emergencies Semi's have brakes
> even without a running motor OR air in the system. With no motor you can
> still lightly brake a Semi to a safe stop. With no air it will come to a
> more or less screeching halt, but at least it will stop.
>
> The same could certainly be done using discs but would require a system
> that is very different from our cars discs and thus lots of R&D dollars.
> Drums have almost no advantages over discs, they are FAR heavier, FAR
> less thermally efficient, they trap water, and heat, they have LESS
> friction surface until they are just about locked up. and they use WAY
> WAY more parts, they are manually adjusted (even automatic slack
> adjusters must be manually adjusted occasionally!)
>
> You asked :)
> --
> Simon
> "I may be wrong, but I'm not uncertain." -- Robert A. Heinlein
maxies, for the others that may believe in this group, They use air
pressure to release the parking brakes they are not used in stopping! I
think that most people could tell by the number of gauges we have to
monitor that if a part like disk brakes could be used safely we would
have them on our half a million dollar tractors:
http://www.----------.com/kenworthdash.jpg
God Bless America, Bill O|||||||O
mailto:--------------------
Simon Juncal wrote:
>
> mabar wrote:
> > So far in this thread, nobody has answered Jeff's question: Why do
> > semi-trucks use drum brakes?
> >
> > I also am curious - why do they use drums rather than disks?
>
> This is one of those questions that has a bunch of answers which are all
> more or less true.
>
> Because the industry is traditional and doesn't like change, because
> drums perform on Semi's pretty well in an overall sense, because
> changing to discs requires a lot of new technology and new untested (in
> trucking) systems which can fail until the bugs are worked out causing
> law suits. In short because the industry is cheap and as stubborn as
> Bill about adapting to new stuff.
>
> Probably the major reason (and long winded one) though is mechanical;
> Because air brake systems works backwards from how we are used to brakes
> working...
>
> The default state on a semi's brake system is LOCKED UP... Unlike
> hydrolic systems where a lack of fluid will result in NO BRAKES, a lack
> of air will result in total brakes. This is because air is used to push
> against the heavy springs that are ALWAYS trying to push the brake shoes
> against the drums. The air is used to compress these springs.
>
> The mechanical advantage here is that in emergencies Semi's have brakes
> even without a running motor OR air in the system. With no motor you can
> still lightly brake a Semi to a safe stop. With no air it will come to a
> more or less screeching halt, but at least it will stop.
>
> The same could certainly be done using discs but would require a system
> that is very different from our cars discs and thus lots of R&D dollars.
> Drums have almost no advantages over discs, they are FAR heavier, FAR
> less thermally efficient, they trap water, and heat, they have LESS
> friction surface until they are just about locked up. and they use WAY
> WAY more parts, they are manually adjusted (even automatic slack
> adjusters must be manually adjusted occasionally!)
>
> You asked :)
> --
> Simon
> "I may be wrong, but I'm not uncertain." -- Robert A. Heinlein
09-08-2006, 06:58 PM
#233
Guest
Posts: n/a
Re: Jeep Toad
Will Honea wrote:
> On Fri, 8 Sep 2006 01:13:36 UTC Jeffrey DeWitt <JeffDeWitt@nc.rr.com>
> wrote:
>
>
>>Tom Greening wrote:
>>
>>>mabar wrote:
>>>
>>>
>>>>So far in this thread, nobody has answered Jeff's question: Why do
>>>>semi-trucks use drum brakes?
>>>>
>>>>I also am curious - why do they use drums rather than disks?
>>>>
>>>>Tom
>>>>
>>>>"L.W.(Bill) ------ III" <----------@***.net> wrote in message
>>>>news:4500AE71.EFC59D0F@***.net...
>>>>
>>>>
>>>>> Coils: "sophisticated and compact suspension design" True, most
>>>>>often used in subcompact front wheel drive rice burners. "more
>>>>>suspension travel" FALSE, their limited four inches of travel makes the
>>>>>libby useless on dirt roads:
>>>>>http://www.----------.com/temp/LibertyAndTraction.mpeg
>>>>> Trucks use drums to stop. Period!
>>>>> God Bless America, Bill O|||||||O
>>>>>mailto:--------------------
>>>>>
>>>>
>>>>
>>>
>>>Hazarding a guess I'd say it's because the drums actually offer more
>>>stopping power and are less susceptible to brake fade. Disks are
>>>lighter but not as powerful. For us they also handle mud better than
>>>drums do, which isn't really a consideration for the average tractor.
>>>
>>>Of course the real FACTS may completely different than the guess I
>>>hazard. :)
>>
>>Well... drums are MORE susceptible to fade, that's one of the advantages
>>of disks. When a drum gets hot it will expand away from the shoes,
>>while when a disk gets hot it will get closer to the shoes.
>>
>>I think all other things being equal disks are going to be more powerful
>>too, because it's easier to squeeze things together than apart.
>>
>>However with the drums you can get more swept area, so all other things
>>AREN'T equal.
>
>
> Minor correction, Jeff. Disc brakes require MORE pressure to operate
> - a lot more. Check the size of the pistons in the front calipers
> versus the size of the pistons in the rear cylinders (or try stopping
> with discs and no power assist <g>). Also, with drums, you can (and
> most modern systems do) get a mechanical boost that increases the
> braking pressure on a drum/shoe where you can't on discs.
I'm not sure sure about how much pressure it takes to operate disks. I
imagine the pistons in drum brakes are smaller because they have to be
to fit inside the drums, with disks there is no such limitation. The
bigger the piston the more leverage (or something like that) and so the
more pressure on the pads for less pressure on the pedal.
As a matter of fact my Studebaker Lark has non power (after market) disk
brakes and its brakes are excellent... stops at least as well as my Jeep.
Most every car these days has power brakes because the Imperial Federal
Government issued a decree that limits the amount of pedal pressure, and
of course if you have power brakes and the booster isn't working then
it's going to be a REAL challenge to stop, which may be what your
thinking of.
Jeff DeWitt
>
> Where you got it dead on is the heat issue. Disc brakes are much less
> suceptable to fade. They also handle water better due the the extra
> pressure, a larger open surface, and the wiping action of the pads.
>
> Then there is the real reason: disc brake assemblies are lighter and
> cheaper for given braking power.
>
> On Fri, 8 Sep 2006 01:13:36 UTC Jeffrey DeWitt <JeffDeWitt@nc.rr.com>
> wrote:
>
>
>>Tom Greening wrote:
>>
>>>mabar wrote:
>>>
>>>
>>>>So far in this thread, nobody has answered Jeff's question: Why do
>>>>semi-trucks use drum brakes?
>>>>
>>>>I also am curious - why do they use drums rather than disks?
>>>>
>>>>Tom
>>>>
>>>>"L.W.(Bill) ------ III" <----------@***.net> wrote in message
>>>>news:4500AE71.EFC59D0F@***.net...
>>>>
>>>>
>>>>> Coils: "sophisticated and compact suspension design" True, most
>>>>>often used in subcompact front wheel drive rice burners. "more
>>>>>suspension travel" FALSE, their limited four inches of travel makes the
>>>>>libby useless on dirt roads:
>>>>>http://www.----------.com/temp/LibertyAndTraction.mpeg
>>>>> Trucks use drums to stop. Period!
>>>>> God Bless America, Bill O|||||||O
>>>>>mailto:--------------------
>>>>>
>>>>
>>>>
>>>
>>>Hazarding a guess I'd say it's because the drums actually offer more
>>>stopping power and are less susceptible to brake fade. Disks are
>>>lighter but not as powerful. For us they also handle mud better than
>>>drums do, which isn't really a consideration for the average tractor.
>>>
>>>Of course the real FACTS may completely different than the guess I
>>>hazard. :)
>>
>>Well... drums are MORE susceptible to fade, that's one of the advantages
>>of disks. When a drum gets hot it will expand away from the shoes,
>>while when a disk gets hot it will get closer to the shoes.
>>
>>I think all other things being equal disks are going to be more powerful
>>too, because it's easier to squeeze things together than apart.
>>
>>However with the drums you can get more swept area, so all other things
>>AREN'T equal.
>
>
> Minor correction, Jeff. Disc brakes require MORE pressure to operate
> - a lot more. Check the size of the pistons in the front calipers
> versus the size of the pistons in the rear cylinders (or try stopping
> with discs and no power assist <g>). Also, with drums, you can (and
> most modern systems do) get a mechanical boost that increases the
> braking pressure on a drum/shoe where you can't on discs.
I'm not sure sure about how much pressure it takes to operate disks. I
imagine the pistons in drum brakes are smaller because they have to be
to fit inside the drums, with disks there is no such limitation. The
bigger the piston the more leverage (or something like that) and so the
more pressure on the pads for less pressure on the pedal.
As a matter of fact my Studebaker Lark has non power (after market) disk
brakes and its brakes are excellent... stops at least as well as my Jeep.
Most every car these days has power brakes because the Imperial Federal
Government issued a decree that limits the amount of pedal pressure, and
of course if you have power brakes and the booster isn't working then
it's going to be a REAL challenge to stop, which may be what your
thinking of.
Jeff DeWitt
>
> Where you got it dead on is the heat issue. Disc brakes are much less
> suceptable to fade. They also handle water better due the the extra
> pressure, a larger open surface, and the wiping action of the pads.
>
> Then there is the real reason: disc brake assemblies are lighter and
> cheaper for given braking power.
>
09-08-2006, 06:58 PM
#234
Guest
Posts: n/a
Re: Jeep Toad
Will Honea wrote:
> On Fri, 8 Sep 2006 01:13:36 UTC Jeffrey DeWitt <JeffDeWitt@nc.rr.com>
> wrote:
>
>
>>Tom Greening wrote:
>>
>>>mabar wrote:
>>>
>>>
>>>>So far in this thread, nobody has answered Jeff's question: Why do
>>>>semi-trucks use drum brakes?
>>>>
>>>>I also am curious - why do they use drums rather than disks?
>>>>
>>>>Tom
>>>>
>>>>"L.W.(Bill) ------ III" <----------@***.net> wrote in message
>>>>news:4500AE71.EFC59D0F@***.net...
>>>>
>>>>
>>>>> Coils: "sophisticated and compact suspension design" True, most
>>>>>often used in subcompact front wheel drive rice burners. "more
>>>>>suspension travel" FALSE, their limited four inches of travel makes the
>>>>>libby useless on dirt roads:
>>>>>http://www.----------.com/temp/LibertyAndTraction.mpeg
>>>>> Trucks use drums to stop. Period!
>>>>> God Bless America, Bill O|||||||O
>>>>>mailto:--------------------
>>>>>
>>>>
>>>>
>>>
>>>Hazarding a guess I'd say it's because the drums actually offer more
>>>stopping power and are less susceptible to brake fade. Disks are
>>>lighter but not as powerful. For us they also handle mud better than
>>>drums do, which isn't really a consideration for the average tractor.
>>>
>>>Of course the real FACTS may completely different than the guess I
>>>hazard. :)
>>
>>Well... drums are MORE susceptible to fade, that's one of the advantages
>>of disks. When a drum gets hot it will expand away from the shoes,
>>while when a disk gets hot it will get closer to the shoes.
>>
>>I think all other things being equal disks are going to be more powerful
>>too, because it's easier to squeeze things together than apart.
>>
>>However with the drums you can get more swept area, so all other things
>>AREN'T equal.
>
>
> Minor correction, Jeff. Disc brakes require MORE pressure to operate
> - a lot more. Check the size of the pistons in the front calipers
> versus the size of the pistons in the rear cylinders (or try stopping
> with discs and no power assist <g>). Also, with drums, you can (and
> most modern systems do) get a mechanical boost that increases the
> braking pressure on a drum/shoe where you can't on discs.
I'm not sure sure about how much pressure it takes to operate disks. I
imagine the pistons in drum brakes are smaller because they have to be
to fit inside the drums, with disks there is no such limitation. The
bigger the piston the more leverage (or something like that) and so the
more pressure on the pads for less pressure on the pedal.
As a matter of fact my Studebaker Lark has non power (after market) disk
brakes and its brakes are excellent... stops at least as well as my Jeep.
Most every car these days has power brakes because the Imperial Federal
Government issued a decree that limits the amount of pedal pressure, and
of course if you have power brakes and the booster isn't working then
it's going to be a REAL challenge to stop, which may be what your
thinking of.
Jeff DeWitt
>
> Where you got it dead on is the heat issue. Disc brakes are much less
> suceptable to fade. They also handle water better due the the extra
> pressure, a larger open surface, and the wiping action of the pads.
>
> Then there is the real reason: disc brake assemblies are lighter and
> cheaper for given braking power.
>
> On Fri, 8 Sep 2006 01:13:36 UTC Jeffrey DeWitt <JeffDeWitt@nc.rr.com>
> wrote:
>
>
>>Tom Greening wrote:
>>
>>>mabar wrote:
>>>
>>>
>>>>So far in this thread, nobody has answered Jeff's question: Why do
>>>>semi-trucks use drum brakes?
>>>>
>>>>I also am curious - why do they use drums rather than disks?
>>>>
>>>>Tom
>>>>
>>>>"L.W.(Bill) ------ III" <----------@***.net> wrote in message
>>>>news:4500AE71.EFC59D0F@***.net...
>>>>
>>>>
>>>>> Coils: "sophisticated and compact suspension design" True, most
>>>>>often used in subcompact front wheel drive rice burners. "more
>>>>>suspension travel" FALSE, their limited four inches of travel makes the
>>>>>libby useless on dirt roads:
>>>>>http://www.----------.com/temp/LibertyAndTraction.mpeg
>>>>> Trucks use drums to stop. Period!
>>>>> God Bless America, Bill O|||||||O
>>>>>mailto:--------------------
>>>>>
>>>>
>>>>
>>>
>>>Hazarding a guess I'd say it's because the drums actually offer more
>>>stopping power and are less susceptible to brake fade. Disks are
>>>lighter but not as powerful. For us they also handle mud better than
>>>drums do, which isn't really a consideration for the average tractor.
>>>
>>>Of course the real FACTS may completely different than the guess I
>>>hazard. :)
>>
>>Well... drums are MORE susceptible to fade, that's one of the advantages
>>of disks. When a drum gets hot it will expand away from the shoes,
>>while when a disk gets hot it will get closer to the shoes.
>>
>>I think all other things being equal disks are going to be more powerful
>>too, because it's easier to squeeze things together than apart.
>>
>>However with the drums you can get more swept area, so all other things
>>AREN'T equal.
>
>
> Minor correction, Jeff. Disc brakes require MORE pressure to operate
> - a lot more. Check the size of the pistons in the front calipers
> versus the size of the pistons in the rear cylinders (or try stopping
> with discs and no power assist <g>). Also, with drums, you can (and
> most modern systems do) get a mechanical boost that increases the
> braking pressure on a drum/shoe where you can't on discs.
I'm not sure sure about how much pressure it takes to operate disks. I
imagine the pistons in drum brakes are smaller because they have to be
to fit inside the drums, with disks there is no such limitation. The
bigger the piston the more leverage (or something like that) and so the
more pressure on the pads for less pressure on the pedal.
As a matter of fact my Studebaker Lark has non power (after market) disk
brakes and its brakes are excellent... stops at least as well as my Jeep.
Most every car these days has power brakes because the Imperial Federal
Government issued a decree that limits the amount of pedal pressure, and
of course if you have power brakes and the booster isn't working then
it's going to be a REAL challenge to stop, which may be what your
thinking of.
Jeff DeWitt
>
> Where you got it dead on is the heat issue. Disc brakes are much less
> suceptable to fade. They also handle water better due the the extra
> pressure, a larger open surface, and the wiping action of the pads.
>
> Then there is the real reason: disc brake assemblies are lighter and
> cheaper for given braking power.
>
09-08-2006, 06:58 PM
#235
Guest
Posts: n/a
Re: Jeep Toad
Will Honea wrote:
> On Fri, 8 Sep 2006 01:13:36 UTC Jeffrey DeWitt <JeffDeWitt@nc.rr.com>
> wrote:
>
>
>>Tom Greening wrote:
>>
>>>mabar wrote:
>>>
>>>
>>>>So far in this thread, nobody has answered Jeff's question: Why do
>>>>semi-trucks use drum brakes?
>>>>
>>>>I also am curious - why do they use drums rather than disks?
>>>>
>>>>Tom
>>>>
>>>>"L.W.(Bill) ------ III" <----------@***.net> wrote in message
>>>>news:4500AE71.EFC59D0F@***.net...
>>>>
>>>>
>>>>> Coils: "sophisticated and compact suspension design" True, most
>>>>>often used in subcompact front wheel drive rice burners. "more
>>>>>suspension travel" FALSE, their limited four inches of travel makes the
>>>>>libby useless on dirt roads:
>>>>>http://www.----------.com/temp/LibertyAndTraction.mpeg
>>>>> Trucks use drums to stop. Period!
>>>>> God Bless America, Bill O|||||||O
>>>>>mailto:--------------------
>>>>>
>>>>
>>>>
>>>
>>>Hazarding a guess I'd say it's because the drums actually offer more
>>>stopping power and are less susceptible to brake fade. Disks are
>>>lighter but not as powerful. For us they also handle mud better than
>>>drums do, which isn't really a consideration for the average tractor.
>>>
>>>Of course the real FACTS may completely different than the guess I
>>>hazard. :)
>>
>>Well... drums are MORE susceptible to fade, that's one of the advantages
>>of disks. When a drum gets hot it will expand away from the shoes,
>>while when a disk gets hot it will get closer to the shoes.
>>
>>I think all other things being equal disks are going to be more powerful
>>too, because it's easier to squeeze things together than apart.
>>
>>However with the drums you can get more swept area, so all other things
>>AREN'T equal.
>
>
> Minor correction, Jeff. Disc brakes require MORE pressure to operate
> - a lot more. Check the size of the pistons in the front calipers
> versus the size of the pistons in the rear cylinders (or try stopping
> with discs and no power assist <g>). Also, with drums, you can (and
> most modern systems do) get a mechanical boost that increases the
> braking pressure on a drum/shoe where you can't on discs.
I'm not sure sure about how much pressure it takes to operate disks. I
imagine the pistons in drum brakes are smaller because they have to be
to fit inside the drums, with disks there is no such limitation. The
bigger the piston the more leverage (or something like that) and so the
more pressure on the pads for less pressure on the pedal.
As a matter of fact my Studebaker Lark has non power (after market) disk
brakes and its brakes are excellent... stops at least as well as my Jeep.
Most every car these days has power brakes because the Imperial Federal
Government issued a decree that limits the amount of pedal pressure, and
of course if you have power brakes and the booster isn't working then
it's going to be a REAL challenge to stop, which may be what your
thinking of.
Jeff DeWitt
>
> Where you got it dead on is the heat issue. Disc brakes are much less
> suceptable to fade. They also handle water better due the the extra
> pressure, a larger open surface, and the wiping action of the pads.
>
> Then there is the real reason: disc brake assemblies are lighter and
> cheaper for given braking power.
>
> On Fri, 8 Sep 2006 01:13:36 UTC Jeffrey DeWitt <JeffDeWitt@nc.rr.com>
> wrote:
>
>
>>Tom Greening wrote:
>>
>>>mabar wrote:
>>>
>>>
>>>>So far in this thread, nobody has answered Jeff's question: Why do
>>>>semi-trucks use drum brakes?
>>>>
>>>>I also am curious - why do they use drums rather than disks?
>>>>
>>>>Tom
>>>>
>>>>"L.W.(Bill) ------ III" <----------@***.net> wrote in message
>>>>news:4500AE71.EFC59D0F@***.net...
>>>>
>>>>
>>>>> Coils: "sophisticated and compact suspension design" True, most
>>>>>often used in subcompact front wheel drive rice burners. "more
>>>>>suspension travel" FALSE, their limited four inches of travel makes the
>>>>>libby useless on dirt roads:
>>>>>http://www.----------.com/temp/LibertyAndTraction.mpeg
>>>>> Trucks use drums to stop. Period!
>>>>> God Bless America, Bill O|||||||O
>>>>>mailto:--------------------
>>>>>
>>>>
>>>>
>>>
>>>Hazarding a guess I'd say it's because the drums actually offer more
>>>stopping power and are less susceptible to brake fade. Disks are
>>>lighter but not as powerful. For us they also handle mud better than
>>>drums do, which isn't really a consideration for the average tractor.
>>>
>>>Of course the real FACTS may completely different than the guess I
>>>hazard. :)
>>
>>Well... drums are MORE susceptible to fade, that's one of the advantages
>>of disks. When a drum gets hot it will expand away from the shoes,
>>while when a disk gets hot it will get closer to the shoes.
>>
>>I think all other things being equal disks are going to be more powerful
>>too, because it's easier to squeeze things together than apart.
>>
>>However with the drums you can get more swept area, so all other things
>>AREN'T equal.
>
>
> Minor correction, Jeff. Disc brakes require MORE pressure to operate
> - a lot more. Check the size of the pistons in the front calipers
> versus the size of the pistons in the rear cylinders (or try stopping
> with discs and no power assist <g>). Also, with drums, you can (and
> most modern systems do) get a mechanical boost that increases the
> braking pressure on a drum/shoe where you can't on discs.
I'm not sure sure about how much pressure it takes to operate disks. I
imagine the pistons in drum brakes are smaller because they have to be
to fit inside the drums, with disks there is no such limitation. The
bigger the piston the more leverage (or something like that) and so the
more pressure on the pads for less pressure on the pedal.
As a matter of fact my Studebaker Lark has non power (after market) disk
brakes and its brakes are excellent... stops at least as well as my Jeep.
Most every car these days has power brakes because the Imperial Federal
Government issued a decree that limits the amount of pedal pressure, and
of course if you have power brakes and the booster isn't working then
it's going to be a REAL challenge to stop, which may be what your
thinking of.
Jeff DeWitt
>
> Where you got it dead on is the heat issue. Disc brakes are much less
> suceptable to fade. They also handle water better due the the extra
> pressure, a larger open surface, and the wiping action of the pads.
>
> Then there is the real reason: disc brake assemblies are lighter and
> cheaper for given braking power.
>
09-09-2006, 12:16 PM
#236
Guest
Posts: n/a
Re: Jeep Toad
Jeffrey DeWitt wrote:
>
> Will Honea wrote:
> > On Fri, 8 Sep 2006 01:13:36 UTC Jeffrey DeWitt <JeffDeWitt@nc.rr.com>
> > wrote:
> >
> >
> >>Tom Greening wrote:
> >>
> >>>mabar wrote:
> >>>
> >>>
> >>>>So far in this thread, nobody has answered Jeff's question: Why do
> >>>>semi-trucks use drum brakes?
> >>>>
> >>>>I also am curious - why do they use drums rather than disks?
> >>>>
> >>>>Tom
> >>>>
> >>>>"L.W.(Bill) ------ III" <----------@***.net> wrote in message
> >>>>news:4500AE71.EFC59D0F@***.net...
> >>>>
> >>>>
> >>>>> Coils: "sophisticated and compact suspension design" True, most
> >>>>>often used in subcompact front wheel drive rice burners. "more
> >>>>>suspension travel" FALSE, their limited four inches of travel makes the
> >>>>>libby useless on dirt roads:
> >>>>>http://www.----------.com/temp/LibertyAndTraction.mpeg
> >>>>> Trucks use drums to stop. Period!
> >>>>> God Bless America, Bill O|||||||O
> >>>>>mailto:--------------------
> >>>>>
> >>>>
> >>>>
> >>>
> >>>Hazarding a guess I'd say it's because the drums actually offer more
> >>>stopping power and are less susceptible to brake fade. Disks are
> >>>lighter but not as powerful. For us they also handle mud better than
> >>>drums do, which isn't really a consideration for the average tractor.
> >>>
> >>>Of course the real FACTS may completely different than the guess I
> >>>hazard. :)
> >>
> >>Well... drums are MORE susceptible to fade, that's one of the advantages
> >>of disks. When a drum gets hot it will expand away from the shoes,
> >>while when a disk gets hot it will get closer to the shoes.
> >>
> >>I think all other things being equal disks are going to be more powerful
> >>too, because it's easier to squeeze things together than apart.
> >>
> >>However with the drums you can get more swept area, so all other things
> >>AREN'T equal.
> >
> >
> > Minor correction, Jeff. Disc brakes require MORE pressure to operate
> > - a lot more. Check the size of the pistons in the front calipers
> > versus the size of the pistons in the rear cylinders (or try stopping
> > with discs and no power assist <g>). Also, with drums, you can (and
> > most modern systems do) get a mechanical boost that increases the
> > braking pressure on a drum/shoe where you can't on discs.
>
> I'm not sure sure about how much pressure it takes to operate disks. I
> imagine the pistons in drum brakes are smaller because they have to be
> to fit inside the drums, with disks there is no such limitation. The
> bigger the piston the more leverage (or something like that) and so the
> more pressure on the pads for less pressure on the pedal.
>
> As a matter of fact my Studebaker Lark has non power (after market) disk
> brakes and its brakes are excellent... stops at least as well as my Jeep.
>
> Most every car these days has power brakes because the Imperial Federal
> Government issued a decree that limits the amount of pedal pressure, and
> of course if you have power brakes and the booster isn't working then
> it's going to be a REAL challenge to stop, which may be what your
> thinking of.
>
> Jeff DeWitt
They have to use proportioning valves on Jeep and most other mixed brake
systems to make up for the extra push needed to run disks.
Without this valve, the rear drums will lock up way sooner than the
front disks will grab. This causes you to do 360's down the road. Not
a good thing....
With the valve in there, the rear brakes are prevented from locking up.
Only the front's should skid.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)
>
> Will Honea wrote:
> > On Fri, 8 Sep 2006 01:13:36 UTC Jeffrey DeWitt <JeffDeWitt@nc.rr.com>
> > wrote:
> >
> >
> >>Tom Greening wrote:
> >>
> >>>mabar wrote:
> >>>
> >>>
> >>>>So far in this thread, nobody has answered Jeff's question: Why do
> >>>>semi-trucks use drum brakes?
> >>>>
> >>>>I also am curious - why do they use drums rather than disks?
> >>>>
> >>>>Tom
> >>>>
> >>>>"L.W.(Bill) ------ III" <----------@***.net> wrote in message
> >>>>news:4500AE71.EFC59D0F@***.net...
> >>>>
> >>>>
> >>>>> Coils: "sophisticated and compact suspension design" True, most
> >>>>>often used in subcompact front wheel drive rice burners. "more
> >>>>>suspension travel" FALSE, their limited four inches of travel makes the
> >>>>>libby useless on dirt roads:
> >>>>>http://www.----------.com/temp/LibertyAndTraction.mpeg
> >>>>> Trucks use drums to stop. Period!
> >>>>> God Bless America, Bill O|||||||O
> >>>>>mailto:--------------------
> >>>>>
> >>>>
> >>>>
> >>>
> >>>Hazarding a guess I'd say it's because the drums actually offer more
> >>>stopping power and are less susceptible to brake fade. Disks are
> >>>lighter but not as powerful. For us they also handle mud better than
> >>>drums do, which isn't really a consideration for the average tractor.
> >>>
> >>>Of course the real FACTS may completely different than the guess I
> >>>hazard. :)
> >>
> >>Well... drums are MORE susceptible to fade, that's one of the advantages
> >>of disks. When a drum gets hot it will expand away from the shoes,
> >>while when a disk gets hot it will get closer to the shoes.
> >>
> >>I think all other things being equal disks are going to be more powerful
> >>too, because it's easier to squeeze things together than apart.
> >>
> >>However with the drums you can get more swept area, so all other things
> >>AREN'T equal.
> >
> >
> > Minor correction, Jeff. Disc brakes require MORE pressure to operate
> > - a lot more. Check the size of the pistons in the front calipers
> > versus the size of the pistons in the rear cylinders (or try stopping
> > with discs and no power assist <g>). Also, with drums, you can (and
> > most modern systems do) get a mechanical boost that increases the
> > braking pressure on a drum/shoe where you can't on discs.
>
> I'm not sure sure about how much pressure it takes to operate disks. I
> imagine the pistons in drum brakes are smaller because they have to be
> to fit inside the drums, with disks there is no such limitation. The
> bigger the piston the more leverage (or something like that) and so the
> more pressure on the pads for less pressure on the pedal.
>
> As a matter of fact my Studebaker Lark has non power (after market) disk
> brakes and its brakes are excellent... stops at least as well as my Jeep.
>
> Most every car these days has power brakes because the Imperial Federal
> Government issued a decree that limits the amount of pedal pressure, and
> of course if you have power brakes and the booster isn't working then
> it's going to be a REAL challenge to stop, which may be what your
> thinking of.
>
> Jeff DeWitt
They have to use proportioning valves on Jeep and most other mixed brake
systems to make up for the extra push needed to run disks.
Without this valve, the rear drums will lock up way sooner than the
front disks will grab. This causes you to do 360's down the road. Not
a good thing....
With the valve in there, the rear brakes are prevented from locking up.
Only the front's should skid.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)
09-09-2006, 12:16 PM
#237
Guest
Posts: n/a
Re: Jeep Toad
Jeffrey DeWitt wrote:
>
> Will Honea wrote:
> > On Fri, 8 Sep 2006 01:13:36 UTC Jeffrey DeWitt <JeffDeWitt@nc.rr.com>
> > wrote:
> >
> >
> >>Tom Greening wrote:
> >>
> >>>mabar wrote:
> >>>
> >>>
> >>>>So far in this thread, nobody has answered Jeff's question: Why do
> >>>>semi-trucks use drum brakes?
> >>>>
> >>>>I also am curious - why do they use drums rather than disks?
> >>>>
> >>>>Tom
> >>>>
> >>>>"L.W.(Bill) ------ III" <----------@***.net> wrote in message
> >>>>news:4500AE71.EFC59D0F@***.net...
> >>>>
> >>>>
> >>>>> Coils: "sophisticated and compact suspension design" True, most
> >>>>>often used in subcompact front wheel drive rice burners. "more
> >>>>>suspension travel" FALSE, their limited four inches of travel makes the
> >>>>>libby useless on dirt roads:
> >>>>>http://www.----------.com/temp/LibertyAndTraction.mpeg
> >>>>> Trucks use drums to stop. Period!
> >>>>> God Bless America, Bill O|||||||O
> >>>>>mailto:--------------------
> >>>>>
> >>>>
> >>>>
> >>>
> >>>Hazarding a guess I'd say it's because the drums actually offer more
> >>>stopping power and are less susceptible to brake fade. Disks are
> >>>lighter but not as powerful. For us they also handle mud better than
> >>>drums do, which isn't really a consideration for the average tractor.
> >>>
> >>>Of course the real FACTS may completely different than the guess I
> >>>hazard. :)
> >>
> >>Well... drums are MORE susceptible to fade, that's one of the advantages
> >>of disks. When a drum gets hot it will expand away from the shoes,
> >>while when a disk gets hot it will get closer to the shoes.
> >>
> >>I think all other things being equal disks are going to be more powerful
> >>too, because it's easier to squeeze things together than apart.
> >>
> >>However with the drums you can get more swept area, so all other things
> >>AREN'T equal.
> >
> >
> > Minor correction, Jeff. Disc brakes require MORE pressure to operate
> > - a lot more. Check the size of the pistons in the front calipers
> > versus the size of the pistons in the rear cylinders (or try stopping
> > with discs and no power assist <g>). Also, with drums, you can (and
> > most modern systems do) get a mechanical boost that increases the
> > braking pressure on a drum/shoe where you can't on discs.
>
> I'm not sure sure about how much pressure it takes to operate disks. I
> imagine the pistons in drum brakes are smaller because they have to be
> to fit inside the drums, with disks there is no such limitation. The
> bigger the piston the more leverage (or something like that) and so the
> more pressure on the pads for less pressure on the pedal.
>
> As a matter of fact my Studebaker Lark has non power (after market) disk
> brakes and its brakes are excellent... stops at least as well as my Jeep.
>
> Most every car these days has power brakes because the Imperial Federal
> Government issued a decree that limits the amount of pedal pressure, and
> of course if you have power brakes and the booster isn't working then
> it's going to be a REAL challenge to stop, which may be what your
> thinking of.
>
> Jeff DeWitt
They have to use proportioning valves on Jeep and most other mixed brake
systems to make up for the extra push needed to run disks.
Without this valve, the rear drums will lock up way sooner than the
front disks will grab. This causes you to do 360's down the road. Not
a good thing....
With the valve in there, the rear brakes are prevented from locking up.
Only the front's should skid.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)
>
> Will Honea wrote:
> > On Fri, 8 Sep 2006 01:13:36 UTC Jeffrey DeWitt <JeffDeWitt@nc.rr.com>
> > wrote:
> >
> >
> >>Tom Greening wrote:
> >>
> >>>mabar wrote:
> >>>
> >>>
> >>>>So far in this thread, nobody has answered Jeff's question: Why do
> >>>>semi-trucks use drum brakes?
> >>>>
> >>>>I also am curious - why do they use drums rather than disks?
> >>>>
> >>>>Tom
> >>>>
> >>>>"L.W.(Bill) ------ III" <----------@***.net> wrote in message
> >>>>news:4500AE71.EFC59D0F@***.net...
> >>>>
> >>>>
> >>>>> Coils: "sophisticated and compact suspension design" True, most
> >>>>>often used in subcompact front wheel drive rice burners. "more
> >>>>>suspension travel" FALSE, their limited four inches of travel makes the
> >>>>>libby useless on dirt roads:
> >>>>>http://www.----------.com/temp/LibertyAndTraction.mpeg
> >>>>> Trucks use drums to stop. Period!
> >>>>> God Bless America, Bill O|||||||O
> >>>>>mailto:--------------------
> >>>>>
> >>>>
> >>>>
> >>>
> >>>Hazarding a guess I'd say it's because the drums actually offer more
> >>>stopping power and are less susceptible to brake fade. Disks are
> >>>lighter but not as powerful. For us they also handle mud better than
> >>>drums do, which isn't really a consideration for the average tractor.
> >>>
> >>>Of course the real FACTS may completely different than the guess I
> >>>hazard. :)
> >>
> >>Well... drums are MORE susceptible to fade, that's one of the advantages
> >>of disks. When a drum gets hot it will expand away from the shoes,
> >>while when a disk gets hot it will get closer to the shoes.
> >>
> >>I think all other things being equal disks are going to be more powerful
> >>too, because it's easier to squeeze things together than apart.
> >>
> >>However with the drums you can get more swept area, so all other things
> >>AREN'T equal.
> >
> >
> > Minor correction, Jeff. Disc brakes require MORE pressure to operate
> > - a lot more. Check the size of the pistons in the front calipers
> > versus the size of the pistons in the rear cylinders (or try stopping
> > with discs and no power assist <g>). Also, with drums, you can (and
> > most modern systems do) get a mechanical boost that increases the
> > braking pressure on a drum/shoe where you can't on discs.
>
> I'm not sure sure about how much pressure it takes to operate disks. I
> imagine the pistons in drum brakes are smaller because they have to be
> to fit inside the drums, with disks there is no such limitation. The
> bigger the piston the more leverage (or something like that) and so the
> more pressure on the pads for less pressure on the pedal.
>
> As a matter of fact my Studebaker Lark has non power (after market) disk
> brakes and its brakes are excellent... stops at least as well as my Jeep.
>
> Most every car these days has power brakes because the Imperial Federal
> Government issued a decree that limits the amount of pedal pressure, and
> of course if you have power brakes and the booster isn't working then
> it's going to be a REAL challenge to stop, which may be what your
> thinking of.
>
> Jeff DeWitt
They have to use proportioning valves on Jeep and most other mixed brake
systems to make up for the extra push needed to run disks.
Without this valve, the rear drums will lock up way sooner than the
front disks will grab. This causes you to do 360's down the road. Not
a good thing....
With the valve in there, the rear brakes are prevented from locking up.
Only the front's should skid.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)
09-09-2006, 12:16 PM
#238
Guest
Posts: n/a
Re: Jeep Toad
Jeffrey DeWitt wrote:
>
> Will Honea wrote:
> > On Fri, 8 Sep 2006 01:13:36 UTC Jeffrey DeWitt <JeffDeWitt@nc.rr.com>
> > wrote:
> >
> >
> >>Tom Greening wrote:
> >>
> >>>mabar wrote:
> >>>
> >>>
> >>>>So far in this thread, nobody has answered Jeff's question: Why do
> >>>>semi-trucks use drum brakes?
> >>>>
> >>>>I also am curious - why do they use drums rather than disks?
> >>>>
> >>>>Tom
> >>>>
> >>>>"L.W.(Bill) ------ III" <----------@***.net> wrote in message
> >>>>news:4500AE71.EFC59D0F@***.net...
> >>>>
> >>>>
> >>>>> Coils: "sophisticated and compact suspension design" True, most
> >>>>>often used in subcompact front wheel drive rice burners. "more
> >>>>>suspension travel" FALSE, their limited four inches of travel makes the
> >>>>>libby useless on dirt roads:
> >>>>>http://www.----------.com/temp/LibertyAndTraction.mpeg
> >>>>> Trucks use drums to stop. Period!
> >>>>> God Bless America, Bill O|||||||O
> >>>>>mailto:--------------------
> >>>>>
> >>>>
> >>>>
> >>>
> >>>Hazarding a guess I'd say it's because the drums actually offer more
> >>>stopping power and are less susceptible to brake fade. Disks are
> >>>lighter but not as powerful. For us they also handle mud better than
> >>>drums do, which isn't really a consideration for the average tractor.
> >>>
> >>>Of course the real FACTS may completely different than the guess I
> >>>hazard. :)
> >>
> >>Well... drums are MORE susceptible to fade, that's one of the advantages
> >>of disks. When a drum gets hot it will expand away from the shoes,
> >>while when a disk gets hot it will get closer to the shoes.
> >>
> >>I think all other things being equal disks are going to be more powerful
> >>too, because it's easier to squeeze things together than apart.
> >>
> >>However with the drums you can get more swept area, so all other things
> >>AREN'T equal.
> >
> >
> > Minor correction, Jeff. Disc brakes require MORE pressure to operate
> > - a lot more. Check the size of the pistons in the front calipers
> > versus the size of the pistons in the rear cylinders (or try stopping
> > with discs and no power assist <g>). Also, with drums, you can (and
> > most modern systems do) get a mechanical boost that increases the
> > braking pressure on a drum/shoe where you can't on discs.
>
> I'm not sure sure about how much pressure it takes to operate disks. I
> imagine the pistons in drum brakes are smaller because they have to be
> to fit inside the drums, with disks there is no such limitation. The
> bigger the piston the more leverage (or something like that) and so the
> more pressure on the pads for less pressure on the pedal.
>
> As a matter of fact my Studebaker Lark has non power (after market) disk
> brakes and its brakes are excellent... stops at least as well as my Jeep.
>
> Most every car these days has power brakes because the Imperial Federal
> Government issued a decree that limits the amount of pedal pressure, and
> of course if you have power brakes and the booster isn't working then
> it's going to be a REAL challenge to stop, which may be what your
> thinking of.
>
> Jeff DeWitt
They have to use proportioning valves on Jeep and most other mixed brake
systems to make up for the extra push needed to run disks.
Without this valve, the rear drums will lock up way sooner than the
front disks will grab. This causes you to do 360's down the road. Not
a good thing....
With the valve in there, the rear brakes are prevented from locking up.
Only the front's should skid.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)
>
> Will Honea wrote:
> > On Fri, 8 Sep 2006 01:13:36 UTC Jeffrey DeWitt <JeffDeWitt@nc.rr.com>
> > wrote:
> >
> >
> >>Tom Greening wrote:
> >>
> >>>mabar wrote:
> >>>
> >>>
> >>>>So far in this thread, nobody has answered Jeff's question: Why do
> >>>>semi-trucks use drum brakes?
> >>>>
> >>>>I also am curious - why do they use drums rather than disks?
> >>>>
> >>>>Tom
> >>>>
> >>>>"L.W.(Bill) ------ III" <----------@***.net> wrote in message
> >>>>news:4500AE71.EFC59D0F@***.net...
> >>>>
> >>>>
> >>>>> Coils: "sophisticated and compact suspension design" True, most
> >>>>>often used in subcompact front wheel drive rice burners. "more
> >>>>>suspension travel" FALSE, their limited four inches of travel makes the
> >>>>>libby useless on dirt roads:
> >>>>>http://www.----------.com/temp/LibertyAndTraction.mpeg
> >>>>> Trucks use drums to stop. Period!
> >>>>> God Bless America, Bill O|||||||O
> >>>>>mailto:--------------------
> >>>>>
> >>>>
> >>>>
> >>>
> >>>Hazarding a guess I'd say it's because the drums actually offer more
> >>>stopping power and are less susceptible to brake fade. Disks are
> >>>lighter but not as powerful. For us they also handle mud better than
> >>>drums do, which isn't really a consideration for the average tractor.
> >>>
> >>>Of course the real FACTS may completely different than the guess I
> >>>hazard. :)
> >>
> >>Well... drums are MORE susceptible to fade, that's one of the advantages
> >>of disks. When a drum gets hot it will expand away from the shoes,
> >>while when a disk gets hot it will get closer to the shoes.
> >>
> >>I think all other things being equal disks are going to be more powerful
> >>too, because it's easier to squeeze things together than apart.
> >>
> >>However with the drums you can get more swept area, so all other things
> >>AREN'T equal.
> >
> >
> > Minor correction, Jeff. Disc brakes require MORE pressure to operate
> > - a lot more. Check the size of the pistons in the front calipers
> > versus the size of the pistons in the rear cylinders (or try stopping
> > with discs and no power assist <g>). Also, with drums, you can (and
> > most modern systems do) get a mechanical boost that increases the
> > braking pressure on a drum/shoe where you can't on discs.
>
> I'm not sure sure about how much pressure it takes to operate disks. I
> imagine the pistons in drum brakes are smaller because they have to be
> to fit inside the drums, with disks there is no such limitation. The
> bigger the piston the more leverage (or something like that) and so the
> more pressure on the pads for less pressure on the pedal.
>
> As a matter of fact my Studebaker Lark has non power (after market) disk
> brakes and its brakes are excellent... stops at least as well as my Jeep.
>
> Most every car these days has power brakes because the Imperial Federal
> Government issued a decree that limits the amount of pedal pressure, and
> of course if you have power brakes and the booster isn't working then
> it's going to be a REAL challenge to stop, which may be what your
> thinking of.
>
> Jeff DeWitt
They have to use proportioning valves on Jeep and most other mixed brake
systems to make up for the extra push needed to run disks.
Without this valve, the rear drums will lock up way sooner than the
front disks will grab. This causes you to do 360's down the road. Not
a good thing....
With the valve in there, the rear brakes are prevented from locking up.
Only the front's should skid.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)