Posi traction?

[gajagfan]

Originally Posted by Comrando

You realize you are answering a post that is almost 4 years old?

It is not an option. V6 autos are all open rear ends.
The reason both tires spin is because of the IRS. With a live axle the torque from the driveshaft will cause the right side to lift, and spin.

I did not. I am glad I was able to be of no assistance!

[Quicksilver 1LE]

Originally Posted by MLL67RSSS

Easy way to tell:

Get the rear tires off the ground and put it in neutral. Spin the tire on one side. If the other side spins the same direction you have Posi/limited-slip etc. If the other tire spins the opposite way you have an "open" non-posi rear.

KISS... (KEEP IT SIMPLE STUPID) Now that's the best post on this subject yet! Won't cost you a thing and only takes a floor jack, jack stands, and your time.

[JR 1]

Originally Posted by gajagfan

I did not. I am glad I was able to be of no assistance!

Well you probably assisted someone, just not the OP

[gajagfan]

Originally Posted by JR 1

Well you probably assisted someone, just not the OP

Hope so!

[PalmerGA]

Originally Posted by Comrando

You realize you are answering a post that is almost 4 years old?

Why do people do that?

Originally Posted by wingnutt

Posi traction and Limited slip are not the same

Wingnutt - please explain your reason for digging up a nearly 4 year old thread? And you're wrong, by the way.

[Norm Peterson]

Originally Posted by Slvrrrr

If no then why don't I have only one tire spin it's not the first time a chart is wrong.

The fact that you have independent rear suspension takes away most of the reason that people with cars like mine always want to spin the right rear. Your car's driveshaft isn't trying to lift the RR (and make it easy to spin) because the U-joints in the half shafts won't let it.


Norm

[ka1]

Interesting. I have a manual SS and I have to replace my right rear tire now. The left rear looks almost like new.

[Norm Peterson]

You can still beat up the RR more if your car has more than 50% left-side weight (likely if you don't normally have a passenger aboard), the rear cradle bushings are still OE, or you're consistently harder on the throttle exiting driveways and side streets and turning to the right.

With IRS even a rear alignment issue could be contributing, since the right side and left side alignment settings are also independent of one another.


Norm

[jimlem]

Originally Posted by ka1

Interesting. I have a manual SS and I have to replace my right rear tire now. The left rear looks almost like new.

Just swap Rt to Lt and vice versa and wait for the Lt to wear dow no match the other then replace both. Get a qty discount. Ha!

[gajagfan]

Originally Posted by Norm Peterson

You can still beat up the RR more if your car has more than 50% left-side weight (likely if you don't normally have a passenger aboard), the rear cradle bushings are still OE, or you're consistently harder on the throttle exiting driveways and side streets and turning to the right.

With IRS even a rear alignment issue could be contributing, since the right side and left side alignment settings are also independent of one another.


Norm

Norm, we have talked this before, but I am thinking that the spring rate if not 100% linear can also cause excessive wear on the right rear. I get IRS, but it is still going to try to load that corner of the car, and thus if not linear, put additional down force on the right rear.

[gajagfan]

Originally Posted by jimlem

Just swap Rt to Lt and vice versa and wait for the Lt to wear dow no match the other then replace both. Get a qty discount. Ha!

Hard to do with directional tires.....Ha Ha!

[ZED SLED]

It's good when zombie threads still have value.

[Norm Peterson]

Originally Posted by gajagfan

Norm, we have talked this before, but I am thinking that the spring rate if not 100% linear can also cause excessive wear on the right rear. I get IRS, but it is still going to try to load that corner of the car, and thus if not linear, put additional down force on the right rear.

Rear tires wear unequally when one of them spins, slips, or slides more than the other one. This could be anything from a full-blown, smoky 1-wheel peel down to just a little scratching kind of thing when starting up from a complete stop while turning at the same time. Entering a moderately fast highway from a dead stop would be a very likely scenario here, where if you're turning a tight enough radius or using enough throttle the Posi is able to force the inside tire to spin up faster than it needs to be going to just roll along its arc.

Side note here - it's common for those who seriously autocross 1st through 4th gen F-bodies and most any pre-2015 Mustang to have to periodically rebuild their cars' limited slip diffs because forcing the inside tire to speed up creates lots of slip between the posi clutch plates while under considerable pressure and carrying lots of torque. R-compound tires only exaggerates this.

Assuming "identical" rear springs and upper/lower seat locations, rear spring rate or its linearity really doesn't come into the picture. I'm sure that the combination of a stiff linear-rate spring on one rear corner and a soft to medium-firm progressive spring on the other could lead to some odd behavior just under straight line acceleration.

Except maybe for negligible bearing friction effects in half-shaft U-joints, driveshaft torque comes out through the mounting bolts for the center section directly into the cradle and from there into the main chassis structure where it balances the engine's torque reaction (has to). Since d/s torque and engine torque reaction are nominally equal and opposite, and since they aren't going through the suspension, there's nothing left to unload the RR . . . save for the little friction effects and any bushing flexibilities between either the center section or main chassis, and the upper spring seats and chassis side sta-bar pickups on the cradle.


Norm

[gajagfan]

Originally Posted by Norm Peterson

Rear tires wear unequally when one of them spins, slips, or slides more than the other one. This could be anything from a full-blown, smoky 1-wheel peel down to just a little scratching kind of thing when starting up from a complete stop while turning at the same time. Entering a moderately fast highway from a dead stop would be a very likely scenario here, where if you're turning a tight enough radius or using enough throttle the Posi is able to force the inside tire to spin up faster than it needs to be going to just roll along its arc.

Side note here - it's common for those who seriously autocross 1st through 4th gen F-bodies and most any pre-2015 Mustang to have to periodically rebuild their cars' limited slip diffs because forcing the inside tire to speed up creates lots of slip between the posi clutch plates while under considerable pressure and carrying lots of torque. R-compound tires only exaggerates this.

Assuming "identical" rear springs and upper/lower seat locations, rear spring rate or its linearity really doesn't come into the picture. I'm sure that the combination of a stiff linear-rate spring on one rear corner and a soft to medium-firm progressive spring on the other could lead to some odd behavior just under straight line acceleration.

Except maybe for negligible bearing friction effects in half-shaft U-joints, driveshaft torque comes out through the mounting bolts for the center section directly into the cradle and from there into the main chassis structure where it balances the engine's torque reaction (has to). Since d/s torque and engine torque reaction are nominally equal and opposite, and since they aren't going through the suspension, there's nothing left to unload the RR . . . save for the little friction effects and any bushing flexibilities between either the center section or main chassis, and the upper spring seats and chassis side sta-bar pickups on the cradle.


Norm

Help me out then good sir. When we were young and stupid, there was a group of local street racers that produced true 9 second street cars. They were all GM based and chose a fair number of Camaros. These cars were never fitted with the NHRA safety equipment for cars of that speed, and since they were unibody cars, they were pretty "flimsy" for that kind of power. The chassis would only last for a short while, and on more than one occasion, the car actually twisted. These things would plant the right rear so hard and lift the front left that the car would twist after multiple passes and the evidence was a crease in the roof line. This twisting effect is real, and was common in even cars with proper roll bars / cages, though the added support prevented the damage to the chassis (and protected the driver of course).
I agree with your comments regarding the damage to the rear end, and also the fact that the right rear often is in a tighter bind due to a reduced radius on a right hand turn on the street opposed to the left hand rear on a left hand corner. I have felt the spinning of the right rear (a few turns) when turning tight under power, and also feel t is getting worse which supports your wearing of the rear end, but I guess I still feel that even with IRS, the right rear is being loaded under hard acceleration, and if spring rates in that corner are not linear, then it is experiencing a greater load, and this potentially seeing more wear.
Thanks as always for getting back with me. I always enjoy it.