mtnman82

This isn't related to the Porsche, but for my '03 Mercedes c230. Background is I have the car sitting on some H&R springs and Bilstein shocks, so it's lowered from stock but the same height as the '05~'06 models (which came lowered from the factory).

My problem is my last set of ffront tires have worn completely bald on the inside ~inch or so. I had the alignment checked and it's within specs. There's not a lot you can adjust on the fron end, pretty much the only thing is toe-in. The castor is fixed at ~10 degrees, camber is just under a degree negative (-0.8 degrees).

So given that toe is the only thing you can adjust, would too much toe-in cause inside tire wear, or not enough toe-in?

The toe was almost 0, and the alignment guy added a tad more toe-in - just want to make sure we're going in the right direction...

pontifex4

They're going to wear completely bald eventually if you only drive in a straight line with any negative camber -- the question is how long they lasted.

Any toe (in or out) will increase the wear problem.

It might also be worth mentioning the tire pressures, sizes, age and tire model.

mtnman82

I understand they'll wear more on the inside with negative camber, but they should wear evenly across with a tad more wear on the inside. The problem is that the inside ~1" was completely bald, like almost to the belts bald, and the rest of the tires had plently of meat on them. Even the outside edge, which I would expect to wear out first, had good meat left. Tires had been maintained with proper pressure (32 psi), and are 225/45/17. They were Dunlop DZ101's and were about 1 1/2 years old, ~15K miles. If the insides wore like the rest of the tire I should have gotten another 5k-10K miles on them.

Bottom line is I'm wondering if adding a little toe-in will shift the wear from the inside of the tire?

docwyte

It's usually toe that kills tires. This past Friday I swapped the snow tires onto my Audi and noticed that the rear tires that were on the car basically had no tread from the center on over to the inside of the tire.

I had an alignment done the next morning and the rear toe was way out of whack...

mtnman82

Doc - so to correct did they add more toe-in or straighten them up?

Droops83

Your guy was correct to add a bit more toe-in. The front wheels on most RWD cars tend to toe-out while driving, so if your front toe is near zero static, the front wheels could actually be slightly toed-out while driving, which promotes inner edge wear. Excessive toe-in tends to scuff the outer edges of the tires.

Also, -0.8 degrees of front camber does not sound like much, especially to those of us who track our cars, but it is actually kind of a lot on a normally driven street car. Since it does not sound like front camber is adjustable, it sounds like you will have to live with this unless you go back to stock springs/ride height, unless there is some sort of aftermarket camber kit available.

docwyte

0.8 negative camber is nothing for a street car. My audi runs -1.5 and it doesn't eat tires. It's toe that eats tires. Try to get it set as close to zero as possible and your tire life will be fine.

944CS

I would check for worn control arm bushings that cause excessive toe or camber change while driving - if your camber was that low and toe was in spec, you won't see the kind of wear that you are describing.

Dave W.

How are you driving it? You'll see wear like that if you do a lot of hard cornering. When cornering hard the inside tire is lifted and tilted until only the inside edge meets the road, and it scrubs pretty hard. I've seen the exact same thing on EVO's that are tracked hard with stock suspension that tends to allow more body roll.

schip43

What he said! I run 1 degree neg up front and 1.5 on the rear of my 951 and 1 degree up front on my Tercel. No impact on tire life what so ever!

Control arm bushings if they are worn or damaged, moving around your toe will change, can't be set. Bad control arm bushings "will" destroy tires in short order!

mtnman82

Thanks for the feedback guys!

I do drive it pretty hard - it's not especially fast but handles & brakes very well from the upgrades I put on, and I tend to take advantage.

I actually did have the castor control arm bushings replaced when I had it aligned. They are a known weakness on this model year. But the old ones looked fine. The alignment guy checked the camber arm bushings and said they looked fine, but I suppose I could replace those too just in case.

I'm thinking I should get someone I trust to drive it around a corner repeatedly so I can get a good look... Glad to have you guys confirm adding the toe-in should help. I just had a chance to drive it out of town and think it drives a little better and also think I'm getting a bit better gas mileage.