OBX, burnout box, unequal shafts= unequal tire heat buildup?

[powermaxx]

Not sure if this is the right area to post this question as it's more dragstrip related...

When I document my setups for run to run comparisons I always check the tire pressure before and after the run. This tells me that I did a consistant burnout (length, rpm, etc...) I'm just now sorting out this setup on my GLHS (555/520 hybrid 3.50 FD with an OBX running unequal axles and Hoosiers DOT 225-50-15) .

So the first thing I notice is that it pulls to the right when doing the burnout (2nd gear). After the run the tire pressure increases about 1 1/4lb on the driver side and only 3/4lb on the pass side. This is a very consistent difference in tire pressure ratio wise regardless of how good or bad the burnout was.

Not sure if this is the OBX/Quaife normal? Or do I need to stagger the tire pressure to compensate? Or possibly it's the corner weight bias (using some spring spacers in the left/rear but nothing else)?

All of the above??

BTW, now running consistent 12.7's. If I can get less "squat" on launch hhhmmmm.

[BadAssPerformance]

Interesting... What was the psi delta with the open diff?

[t3rse]

i took a turn really hard before i downed the car for mods, and the camber on my left front slipped in. after that, with the obx, the car pulled really hard to the left. i think it's becuase it's trying to equal out tire speed. point being, as these things tend to toe-in under power, i wonder if your toe angle is changing causing the difference in tire speed...

[turbovanman²]

Whats your 60ft times?

I run the equal length setup but according to others, they have found no difference between the 2. When doing the burnout, I do have to correct it but after that, when I launch, its straight as an arrow, heck, I could just use my pinky if I really wanted to,

[t3rse]

i don't have power steering and when the camber/toe were correct, i could do a burnout or steer under throttle one-handed and keep her straight under accel with one finger.

[powermaxx]

1) Last year I was running one of those spring loaded plates. Didn't seem to work. So I shimmed the swaybar, etc... but still only one legged burnouts (pass side). I would stagger the air pressure 18 drivers/16psi pass. Pass side would usually go up about 1 1/2psi

2) I have a little toe out to compensate for the launch. All mounts are poly bushings as are all the LCA stuff and sway bar.

3) My 60fts are 1.90's with a good burnout (still working on the setup).When I launch it seems to go styraight but every now and then it wants to torque steer and then straightens out.


My theory is due to the weight bias side to side that the drivers side works harder (trans, battery and the big driver don't help ). I'm going to try shimming the swaybar and more driver/rear spring stiffening for more preload on the passenger side. Been looking over some threads on traction and saw some simular thoughts on traction bars that I've been designing.

[turbovanman²]

Steve, let us know about the traction bars.

BTW, check out this thread on the diff, wondering if your noticing the same-

http://www.turbo-mopar.com/forums/showthread.php?t=4275

[BadAssPerformance]

...Been looking over some threads on traction and saw some simular thoughts on traction bars that I've been designing.

interesting...

[MiniMopar]

One thing about these diffs vs an LSD, it doesn't really care about wheel speed...just torque. Since the left side is heavier, it may be spinning that wheel faster because it is biasing torque towards the wheel with the most grip.

[Phreakish]

almost.

Equal torque = equal force at the tire.

Less weight (normal force) on the pass. side means less friction force (friction force = friction coefficient times normal force). Less friction force (traction) means higher wheel speeds during burnout = more pressure buildup. Same goes for the right-side pull.

Shim the swaybar, or put air shox in the rear and bias the pressure in each to get equal weight on the front tires. Make a run or 2 with a passenger maybe? or a couple sacks of concrete to put more weight on the pass. side and see if the difference decreases (beats turning bolts and then having to undo it, or do something else

[powermaxx]

almost.

Equal torque = equal force at the tire.

Less weight (normal force) on the pass. side means less friction force (friction force = friction coefficient times normal force). Less friction force (traction) means higher wheel speeds during burnout = more pressure buildup. Same goes for the right-side pull.

Shim the swaybar, or put air shox in the rear and bias the pressure in each to get equal weight on the front tires. Make a run or 2 with a passenger maybe? or a couple sacks of concrete to put more weight on the pass. side and see if the difference decreases (beats turning bolts and then having to undo it, or do something else

Pretty much what I was thinking. I have the front end up for hub replacement right now and was going to put the shims back in. As far as air shocks I haven't found anything that will fit an L body. I do have some spring spacers in the driver rear springs. Maybe I can fit some more in...

[Speedeuphoria]

Hey well if you want to get custom you can make something work for a rear air shock, like Russ did look here
it is the 5th pic from the bottom on the left

http://hometown.aol.com/russjerome/miscpics.html

[powermaxx]

Hey well if you want to get custom you can make something work for a rear air shock, like Russ did look here
it is the 5th pic from the bottom on the left

http://hometown.aol.com/russjerome/miscpics.html

It's a numbered car so no cutting allowed . I have original eng/trans (vin # stamped on them) tucked away .

But I do like the concept. I'm trying to find some of the hydraulic shocks like the "low rider" cars.

[Phreakish]

I just sold a pair of rear airshocks for an omni - so they're out there... just gotta find them

the NEON strut thread at TD.com I think has a listing for an application that is similar to ours for the rear, maybe there are airshocks for that application that are easier to find?

[gasketmaster]

It's probably in the corner weights but don't forget to measure the actual outside diameter of the tires at equal air pressure........it's surprising how much difference you can find sometimes

[powermaxx]

It's probably in the corner weights but don't forget to measure the actual outside diameter of the tires at equal air pressure........it's surprising how much difference you can find sometimes

Yep, used to that from my RWD slicks (31 x16 soon to be 33.5 x 17 ). I've had to send some back as they were off a lot!!!!

I've swapped these tires around on this one as they don't have as much circimference difference (less than an 1/2 inch). Just to see if there was any difference (maybe an old tire on the shelf and one is maybe fresh). Both seem new though.

Have shimmed the say bar again and will be trying to find airshocks for the rear (stilll haven't come across them).

THX

[powermaxx]

Shimming the sway bar back to last years setup and all is now good again. Burnout is equal in heat build up now and seems to stay straight in the box.

Now if my rear brakes were new I could do consistent burnouts .