Lapping - Front Tire outer edge wear - suspension fix?

[V10 ICBM]

Hi all:

I do a lot of lapping days in the frozen North during our brief spring, summer and fall. My buddys' 2002 ACRs exhibit very even wear on the front Pilots - very flat accross the width of the tire.
I on the other hand, have pronounced outer edge wear on the fronts and some on the rear - I am thinking of first going to a stiffer front sway bar - which is supposed to reduce understeer as well - OR in addition, go to stiffer springs (eibach or hyper coil).

I drive a stock suspension 2000 GTS with stock Pilots @ 36 LBs/front , 32 lbs/rear -

Not trying to get ultimate track performance, just better tire (even) wear. i like putting most of my $ into seat time.

What d'ya all think?

2000 GTS, Steel Grey, Ballanger headers, chrome smooth tubes, Random tech Metal Cats, Corsa cat back, 4 Wheel Stoptech system.

 

[Janni]

Need more negative camber...... get a decent track alignment.

 

[JonB]

For starters, Your alignment *****.

But have you had the 998-999 rack/frame recalls performed? If not, You MAY have a problem! [ The Year Matters ]

For max tire wear get aligned to OE specs after recall.

For max handling performance get a corner-weighted-track-alignment that will ending up using more of your INBSIDE shoulders, not outside. AMAZING difference in handling.

 

[V10 ICBM]

Hi Jon - thanks for all the parts last year - the diffrence on the back staright at mosport and downshifting is very impressive - to my ACR buddies.

Yes - had the recall done - steering box gussets - alignment done as well.

Think I am going with more track camber and re-alignment - still these ACR's have better tire wear with stock alignment - must be their stiff springs?

J

 

[Fast Viper Dan]

Pull the sport shims out and give it a try.

 

[jrkermode]

What do you mean by "outer edge wear"? It is normal for the tires to be scuffed over the shoulder of the tread. Look for the little Michelin man molded into the shoulder. You should just wipe out his head.

Be careful about comparing your car with your buddy's. Differences in spring rates, alignment, tire pressure and driving style could all explain differences in tire wear.

I recommend against the stiffer front swaybar or springs. That will INCREASE understeer. As a very general rule, stiffer suspension decreases grip. I know it sounds crazy, but it's true.

 

[V10 ICBM]

jrkermode:

Thanks - yes my buddies have much stiffer springs with their ACRs - I think 2x stiffer springs than a GTS. Likely explains differenece. FYI they are running stock air press 29 lbs all around.

I thought GTS and ACR factory alignments were same - True?

Swaybar issue - yes stiffer front than rear bias would incr push - I was thinking of an adj swaybar - possibly Woodhouse's - comes with stiffer rear swaybar bushings - read thread that setting front swaybar at softer setting and also installing stiffer rear swaybar bushings effectively causes pressure on rear swaybar earlier (ie bushings compress less) so result is same as a bigger=stiffer rear swaybar (Woodhouse says its equal to about 35% stiffer rear swaybar with these bushings). The adj front New swaybar is set to a softer setting - by adjusting front to rear bias, push is reduced.
I thought that with my stock GTS springs (which work well) and the new sway bar and bushings, I would get good practical road holding with softer springs, but better turn in and less push (slow speed esp) with the Woodhouse swaybar set-up.

Step 1: I also will try first either removing sport shims (How do ya do it?) then, perhaps a track-street alignment as per previous threads by snake experts.

Decent plan?

 

[jrkermode]

I don't know the ACR alignment specs.

I recommend you start with adjusting your shocks. 1/2 turn from full stiff seems to be an OK setting for a car that is primarily street driven. They are usually full soft from the factory.

To remove the sport shims, pull off the front wheel. Loosen the nuts retaining the upper control arm. Pull out the shims. Tighten up the control arm. You will get a little toe out and a little negative camber.

 

[Frank Parise]

Check that there are no mechanical issues with your front suspension. You can get this kind of unusual tire wear if you have a bad hub/bearing assembly (very common for Vipers after certain periods of track use, especially if you like to hit the apex and corner exit curbing), or if you have a tie rod (toe link) end that needs to be replaced.

If the above checks out to be OK, I would focus on your alignment, especially for track events. Outside tire wear indicates not enough negative camber on that tire, especially if your pyrometer readings are showing that the outer portion of the tread is running hotter than the middle or the inside. The easiest way to add more negative camber is to remove the sport shims from your upper control arms. This will add approximately 0.5 degrees additional negative camber. You will also end up with more toe out, which isn't necessarily bad and it is easy to adjust.

It's quite possible that you are driving your car alot harder in the corners than your buddy is. If this is the case, you may very well need more negative camber than he does. He also has a huge advantage because of his adjustable shock absorbers.

I definitely wouldn't screw with the sway bar at this point. Most of the most highly modified Viper racecars in the VRL have never changed the factory sway bars, although they have changed the shocks, springs, control arm bushings, ride heights, alignment settings, air pressures, etc.

Good luck, hope this helps.

 

[Fast Viper Dan]

Frank might be right about driving harder than your buddy.
What I mean is if you go into the corner hotter, you will be grinding your front tire going in and you'll be a little slower coming out.
Go for a ride, if you haven't already to see how your friend drives the corners.
Simply pulling the sport shims changed my car from rounding the outer edges to wearing the inner surface, not just the edge but the whole surface of the tire. I would not recommend driving your car on the street with the sport shims out. This will lead to premature tire wear. Also the car will wander on the freeway from lack of toe in. Removing the shims takes about a 1/2 hr. Ask some one to show you how to do this. It's easy.
Good Luck!