Re: Advice on 1999 Jeep Cherokee vs. 2001 Jeep Cherokee
 

Jerry Bransford wrote:
> "DougW" <post.replies@invalid.address> wrote in message
> news:d0i%a.9108$Ij4.1850@news2.central.cox.net...
>> 85 is a bit low. spec should be 95-105. At any rate, trust the book.
>> What prevents warpage is having all the lugs properly torqued.
>
> 85 ft-lbs. is what my MOPAR FSM says for the low-end of the allowable torque
> range.

Yea. I just checked, your correct. I use 95 for almost every wheel except for
mags or lugs with flat surfaces. Wonder if using the low side would be better?

Re: Advice on 1999 Jeep Cherokee vs. 2001 Jeep Cherokee
 

On Sat, 16 Aug 2003 04:01:13 GMT, "DougW" <post.replies@invalid.address>
wrote:

>Jim Hunter wrote:
>> I have a 2001 Grand Cherokee which I bought used 1 year ago with 25k miles
>> on the odometer. The first thing I did after purchasing was to take it my
>> dealer and complain about brake pedal pulsing (a sign o warped rotors). The
>> fix was new improved frt calipers, new rotors, new pads...all covered under
>> warranty. I beleive the problem is NOT the rotors, but a design defect in
>> the calipers. I have put 25k miles more miles on this new front brake setup,
>> with NO brake rotor warping, no problems. Also, I suggest that you take the
>> time to use a torque wrench to tighten each of the lug nuts to 85 lbs/in.
>> That helps prevent warpage, I think.
>
>85 is a bit low. spec should be 95-105. At any rate, trust the book.
>What prevents warpage is having all the lugs properly torqued.

That's odd... just had new BFG All Terrains put on my '98 XJ and
according to Costco, the manufacturers torque rating was 115lbs. I have
been doing 90lbs. myself....


--
Taylor

'89 Audi 200
'03 Audi S6 Avant
'98 Jeep Cherokee Sport

Re: Advice on 1999 Jeep Cherokee vs. 2001 Jeep Cherokee
 

Ken Stoorza wrote:
> The '96 T&C has gone through a couple of "warped rotor" events in it's 130K
> lifetime. I am a wheel lug nut torque fanatic and not only set them properly
> but 1. Do so using a few tightening iterations in a "criss cross" pattern
> and 2. Re-torque them myself each and every time someone else does it as
> soon as I get home (yes, I loosen them first).
>
> After alot of years and a lot of different cars, I am convinced that proper
> lug nut torque provides no assurance that the rotors will not warp.
> Something else is going on that dominates the tendency to warp and it is not
> lug nut torque.

There are several.

1) heat soak
When you use the brakes a lot then sit there at the light with your foot
on the brake. The pads hold heat in the rotor and that difference affects
the material and can lead to warping.
2) drenching
When you get the brakes real hot then stick them in water (like a stream
crossing).
3) Worn caliper mounting bolts
As these things age the brake pads don't always back off and sometimes one
side of the pad will ride against the rotor. Always check pad thickness.
If one pad is thinner than the other you have this problem.
4) Worn piston
If the piston doesn't retract properly the brakes will rub and get hot
5) Defective rotors
DC stock rotors/two piece/ el-cheapo
6) Improper turning of rotors/surfacing of rotors
Midas (for example) and some other chains use the old milling machines
with one blade, not the multiblade rotary milling machines. What was good
for gramp's vehicle isn't good for modern rotors.
7) Probably should be up higher.... Impropper break-in of new rotors/pads
If you don't break in rotors properly they will not wear well.
The procedure is fairly easy.. stillen has it on the website last I checked.

That's just a few.

--
rbg

Re: Advice on 1999 Jeep Cherokee vs. 2001 Jeep Cherokee
 

DougW wrote:
>
> There are several.
>
> 1) heat soak
> When you use the brakes a lot then sit there at the light with your foot
> on the brake. The pads hold heat in the rotor and that difference affects
> the material and can lead to warping.
> 2) drenching
> When you get the brakes real hot then stick them in water (like a stream
> crossing).
> 3) Worn caliper mounting bolts
> As these things age the brake pads don't always back off and sometimes one
> side of the pad will ride against the rotor. Always check pad thickness.
> If one pad is thinner than the other you have this problem.
> 4) Worn piston
> If the piston doesn't retract properly the brakes will rub and get hot
> 5) Defective rotors
> DC stock rotors/two piece/ el-cheapo
> 6) Improper turning of rotors/surfacing of rotors
> Midas (for example) and some other chains use the old milling machines
> with one blade, not the multiblade rotary milling machines. What was good
> for gramp's vehicle isn't good for modern rotors.
> 7) Probably should be up higher.... Impropper break-in of new rotors/pads
> If you don't break in rotors properly they will not wear well.
> The procedure is fairly easy.. stillen has it on the website last I checked.
>
> That's just a few.
>
> --
> rbg

A coupla more ideas:
1) When you torque (re-torque) the lug nuts, it is best to have the
weight off the wheel thru the entire torqueing process (have someone
apply the brakes if necessary for the last stage of torqueing - probably
won't be necessary - parking pawl is generally sufficient - at least for
the fronts). If you let the weight down on the wheel during the
torqueing, not only a vertical force, but a tremendous side force is put
on the tire and wheel as the geometry of the suspension changes as the
springs settle from the vehicle weight and can result in residual
stresses in the installed wheel/hub assembly (one more factor that can
be eliminated).

2) For extra insurance against warping, especially on a problem vehicle,
you can have a new set of rotors cryogenically treated - will cost $75
plus shipping for treatment of a pair of rotors (based on: $1.50/pound
with min. job charge of $75 - a typical rotor would weigh in the
neighborhood of 15 to 21 pounds - rears are almost certainly not the
problem - only necessary to do the fronts). I recommend
www.300below.com. I had new rotors (fronts only) done on my '99
Concorde (LH cars are also plaqued by rotor warping) several months ago,
and the brakes are as smooth today as when I first put them on - and I
just spent a week vacation in the mountians of West Virginia with 3-mile
8 to 10% downhill grades braking from 55 mph to 15 mph for hairpin turns
- I think I just proved (to myself anyway) that there is something to
this cryo-treating). Side benefits: Rotor wear is decreased to 1/2 to
1/3 of non-treated rotors, pad wear decreased to 80% of normal; friction
coefficient somewhere between unchanged to slight increase.

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")


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Re: Advice on 1999 Jeep Cherokee vs. 2001 Jeep Cherokee
 

DougW wrote:
>
> There are several.
>
> 1) heat soak
> When you use the brakes a lot then sit there at the light with your foot
> on the brake. The pads hold heat in the rotor and that difference affects
> the material and can lead to warping.
> 2) drenching
> When you get the brakes real hot then stick them in water (like a stream
> crossing).
> 3) Worn caliper mounting bolts
> As these things age the brake pads don't always back off and sometimes one
> side of the pad will ride against the rotor. Always check pad thickness.
> If one pad is thinner than the other you have this problem.
> 4) Worn piston
> If the piston doesn't retract properly the brakes will rub and get hot
> 5) Defective rotors
> DC stock rotors/two piece/ el-cheapo
> 6) Improper turning of rotors/surfacing of rotors
> Midas (for example) and some other chains use the old milling machines
> with one blade, not the multiblade rotary milling machines. What was good
> for gramp's vehicle isn't good for modern rotors.
> 7) Probably should be up higher.... Impropper break-in of new rotors/pads
> If you don't break in rotors properly they will not wear well.
> The procedure is fairly easy.. stillen has it on the website last I checked.
>
> That's just a few.
>
> --
> rbg

A coupla more ideas:
1) When you torque (re-torque) the lug nuts, it is best to have the
weight off the wheel thru the entire torqueing process (have someone
apply the brakes if necessary for the last stage of torqueing - probably
won't be necessary - parking pawl is generally sufficient - at least for
the fronts). If you let the weight down on the wheel during the
torqueing, not only a vertical force, but a tremendous side force is put
on the tire and wheel as the geometry of the suspension changes as the
springs settle from the vehicle weight and can result in residual
stresses in the installed wheel/hub assembly (one more factor that can
be eliminated).

2) For extra insurance against warping, especially on a problem vehicle,
you can have a new set of rotors cryogenically treated - will cost $75
plus shipping for treatment of a pair of rotors (based on: $1.50/pound
with min. job charge of $75 - a typical rotor would weigh in the
neighborhood of 15 to 21 pounds - rears are almost certainly not the
problem - only necessary to do the fronts). I recommend
www.300below.com. I had new rotors (fronts only) done on my '99
Concorde (LH cars are also plaqued by rotor warping) several months ago,
and the brakes are as smooth today as when I first put them on - and I
just spent a week vacation in the mountians of West Virginia with 3-mile
8 to 10% downhill grades braking from 55 mph to 15 mph for hairpin turns
- I think I just proved (to myself anyway) that there is something to
this cryo-treating). Side benefits: Rotor wear is decreased to 1/2 to
1/3 of non-treated rotors, pad wear decreased to 80% of normal; friction
coefficient somewhere between unchanged to slight increase.

Bill Putney
(to reply by e-mail, replace the last letter of the alphabet in my
address with "x")


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