On Sat, 05 Nov 2005 09:21:56 -0500, Mike Romain <romainm@sympatico.ca>
wrote:

[snip]
>
>I also think your gas mileage is 'way' off. This is likely due to the
>oversized tires giving you incorrect speedometer readings. The larger
>tires travel farther every revolution than the speedometer thinks. I

Um, which also means..I'm traveling ...FASTER? than the speedo say I
am... right?
(And what's with these 85 MPH speedo's ? ...BAH!) ;-)

>use a GPS to check my 'real' speed with the dash speed. We get over 24
>mpg in our Cherokee on the highway with about 18 combined city/highway.
>
>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!
>Aug./05 http://www.imagestation.com/album/in...?id=2120343242
>(More Off Road album links at bottom of the view page)
>

....

 

That's right, watch for speed traps, the cops don't care if you only
'think' you are doing 68 mph as they clock you zipping along at 75....

What size are the tires? When we went to P235x75's on our 88 Cherokee,
the GPS says the speedometer gear is exact for them. I was a bit
surprised because they are one size larger than any the factory chart
says they put on them.

I lucked out on my CJ7. Someone had changed the gear or t-case. The
speedo was low when I got it with 31's on it. I went to 33's and the
speedometer is now right on.

Mike

noneyabusiness wrote:
>
> On Sat, 05 Nov 2005 09:21:56 -0500, Mike Romain <romainm@sympatico.ca>
> wrote:
>
> [snip]
> >
> >I also think your gas mileage is 'way' off. This is likely due to the
> >oversized tires giving you incorrect speedometer readings. The larger
> >tires travel farther every revolution than the speedometer thinks. I
>
> Um, which also means..I'm traveling ...FASTER? than the speedo say I
> am... right?
> (And what's with these 85 MPH speedo's ? ...BAH!) ;-)
>
> >use a GPS to check my 'real' speed with the dash speed. We get over 24
> >mpg in our Cherokee on the highway with about 18 combined city/highway.
> >
> >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!
> >Aug./05 http://www.imagestation.com/album/in...?id=2120343242
> >(More Off Road album links at bottom of the view page)
> >
>
> ...

 

That's right, watch for speed traps, the cops don't care if you only
'think' you are doing 68 mph as they clock you zipping along at 75....

What size are the tires? When we went to P235x75's on our 88 Cherokee,
the GPS says the speedometer gear is exact for them. I was a bit
surprised because they are one size larger than any the factory chart
says they put on them.

I lucked out on my CJ7. Someone had changed the gear or t-case. The
speedo was low when I got it with 31's on it. I went to 33's and the
speedometer is now right on.

Mike

noneyabusiness wrote:
>
> On Sat, 05 Nov 2005 09:21:56 -0500, Mike Romain <romainm@sympatico.ca>
> wrote:
>
> [snip]
> >
> >I also think your gas mileage is 'way' off. This is likely due to the
> >oversized tires giving you incorrect speedometer readings. The larger
> >tires travel farther every revolution than the speedometer thinks. I
>
> Um, which also means..I'm traveling ...FASTER? than the speedo say I
> am... right?
> (And what's with these 85 MPH speedo's ? ...BAH!) ;-)
>
> >use a GPS to check my 'real' speed with the dash speed. We get over 24
> >mpg in our Cherokee on the highway with about 18 combined city/highway.
> >
> >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!
> >Aug./05 http://www.imagestation.com/album/in...?id=2120343242
> >(More Off Road album links at bottom of the view page)
> >
>
> ...

 

That's right, watch for speed traps, the cops don't care if you only
'think' you are doing 68 mph as they clock you zipping along at 75....

What size are the tires? When we went to P235x75's on our 88 Cherokee,
the GPS says the speedometer gear is exact for them. I was a bit
surprised because they are one size larger than any the factory chart
says they put on them.

I lucked out on my CJ7. Someone had changed the gear or t-case. The
speedo was low when I got it with 31's on it. I went to 33's and the
speedometer is now right on.

Mike

noneyabusiness wrote:
>
> On Sat, 05 Nov 2005 09:21:56 -0500, Mike Romain <romainm@sympatico.ca>
> wrote:
>
> [snip]
> >
> >I also think your gas mileage is 'way' off. This is likely due to the
> >oversized tires giving you incorrect speedometer readings. The larger
> >tires travel farther every revolution than the speedometer thinks. I
>
> Um, which also means..I'm traveling ...FASTER? than the speedo say I
> am... right?
> (And what's with these 85 MPH speedo's ? ...BAH!) ;-)
>
> >use a GPS to check my 'real' speed with the dash speed. We get over 24
> >mpg in our Cherokee on the highway with about 18 combined city/highway.
> >
> >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!
> >Aug./05 http://www.imagestation.com/album/in...?id=2120343242
> >(More Off Road album links at bottom of the view page)
> >
>
> ...

 

Because you drive at traffic speeds, 75-80 in Southern California
when it's not a parking lot.
God Bless America, Bill O|||||||O
mailto:-------------------- http://www.----------.com/

noneyabusiness wrote:
>
> Um, ...what Snow said ... ;-)
> But I get nowhere near 20 mpg :(
> (..."AW4" ??)
>
> ...

 

Because you drive at traffic speeds, 75-80 in Southern California
when it's not a parking lot.
God Bless America, Bill O|||||||O
mailto:-------------------- http://www.----------.com/

noneyabusiness wrote:
>
> Um, ...what Snow said ... ;-)
> But I get nowhere near 20 mpg :(
> (..."AW4" ??)
>
> ...

 

Because you drive at traffic speeds, 75-80 in Southern California
when it's not a parking lot.
God Bless America, Bill O|||||||O
mailto:-------------------- http://www.----------.com/

noneyabusiness wrote:
>
> Um, ...what Snow said ... ;-)
> But I get nowhere near 20 mpg :(
> (..."AW4" ??)
>
> ...

 

Billy Ray wrote:
> As Bill mentioned the answer is that you should not drive on pavement with
> your part time (Select-Trac) engaged.
>
> The reason is that when part time 4 wheel drive is engaged the front and
> real axles are locked together and therefore turn at the same speed.
>
> If you were only to drive in a straight line this would be no problem as the
> front and rear tires would all be traveling at the same speed.
>
> However, as you recall from driving in the snow or rain, in a turn the tires
> stop following two parallel tracks and start following 4 separate tracks and
> each track had the tires traveling different distances at different speeds.
>
> This leads to the tires being dragged either in relative acceleration or
> deceleration which scrubs the tires and puts additional strain on the
> driveline and suspension components.
>
> There is a nice picture that shows the problems at:
> http://auto.howstuffworks.com/framed...bc.com/4WD101/

A truly well designed 4WD vehicle would have a center diff or viscous
coupling which could be llocked when necessary.

 

Billy Ray wrote:
> As Bill mentioned the answer is that you should not drive on pavement with
> your part time (Select-Trac) engaged.
>
> The reason is that when part time 4 wheel drive is engaged the front and
> real axles are locked together and therefore turn at the same speed.
>
> If you were only to drive in a straight line this would be no problem as the
> front and rear tires would all be traveling at the same speed.
>
> However, as you recall from driving in the snow or rain, in a turn the tires
> stop following two parallel tracks and start following 4 separate tracks and
> each track had the tires traveling different distances at different speeds.
>
> This leads to the tires being dragged either in relative acceleration or
> deceleration which scrubs the tires and puts additional strain on the
> driveline and suspension components.
>
> There is a nice picture that shows the problems at:
> http://auto.howstuffworks.com/framed...bc.com/4WD101/

A truly well designed 4WD vehicle would have a center diff or viscous
coupling which could be llocked when necessary.

 

Billy Ray wrote:
> As Bill mentioned the answer is that you should not drive on pavement with
> your part time (Select-Trac) engaged.
>
> The reason is that when part time 4 wheel drive is engaged the front and
> real axles are locked together and therefore turn at the same speed.
>
> If you were only to drive in a straight line this would be no problem as the
> front and rear tires would all be traveling at the same speed.
>
> However, as you recall from driving in the snow or rain, in a turn the tires
> stop following two parallel tracks and start following 4 separate tracks and
> each track had the tires traveling different distances at different speeds.
>
> This leads to the tires being dragged either in relative acceleration or
> deceleration which scrubs the tires and puts additional strain on the
> driveline and suspension components.
>
> There is a nice picture that shows the problems at:
> http://auto.howstuffworks.com/framed...bc.com/4WD101/

A truly well designed 4WD vehicle would have a center diff or viscous
coupling which could be llocked when necessary.