Hey guys, i just checked my tires to see how im doing on tread before the rain comes. Anyways, on the back set in seems like there is alot more tread wear on the inner side vs it being even...why would this be? I understand why its that way on the front set but why the back?

 

Camber causes the wear on the inner side. This is very typical for the cars, the rears almost always wear out first on the inside. If this is not the case the alignment is probably off.

 

To add to Dharn55's answer...factory specs for a 996 call for nearly 1-1/2 degrees of negative camber, plus or minus 1/4 degree. This definitely helps keep the rear end planted (so that it does not try to swap positions with the front in a corner) but at the expense of premature inside rear tire wear. This higher wear is especially noticeable if the car is driven mostly on the highways and not tracked much.

The stock adjustment mechanism does not give a lot of rear camber adjustability, so you may find--as I did--that trying to hit the minimum factory camber spec, to increase tire life, may not be possible. (Note, I only considered doing this since my car sees no track time at the moment. You will need to make your own decision as to where you want your rear camber set.)

 

Normal for our cars, how many miles has it been?

Your front and rear tires will do this, with the stock setup, it is normal for your rear tires to wear out about twice as fast as the fronts

When I run my track, more aggressive setup, my rear tires only last me about 5k miles

 

Rear tires wear faster than front on 911s. But if you are seeing too much inside edge wear, it is an alignment issue. Usually it is camber or toe. If your car is lowered, it increases negative camber, meaning the wheel is not straight up and down - but "tilted" inward [looking at the top of the tire]. This means that the wear is not uniform across the tire. Rather, the bottom-inside edge is getting the abuse. Toe in means that your tire is not pointed straight ahead. Instead it it pointed a little to the middle of the car.

In my experience, too much toe in will eat tires faster than too much negative camber. If you haven't had your alignment checked in a while [like over a year], have the shop look at it.

-td

 

About 8k

 

What was your rear camber range?

My front camber has a tight range w/ little adjustability (0 to -0.75).
My rear camber has much more range and can be changed from -1 to -2.5. Mine is set to -1.0 for autox purposes, but it also helps improve street wear.

 

My alignment shop was only able to dial down RR camber to -1.6, LR to -1.4.

Thanks for sharing your experience at -1.0...I'll shoot for that (with new rear upper control arms probably) at my next rear tire replacement.

 

How often does everyone:
1) Check Tire pressure?
2) Rotate tires?

 

With new tires, I check pressures with a digital gauge every week until I know how they'll behave. Usually I see no more than 2-3 psi/month drop, in which case I'll check with the gauge at least every month when I top the tires up.

I do a visual inspection of all four tires before every drive, on any car I drive.

As for rotation, you can't do that most of the time. Front and rear tires are different sizes, and the tires are usually uni-directional (so you can't swap them left and right).

 

thanks. Happy driving.

I know it no Pcar, however my wife's Ford Expedition ate through a new tire in less than a year due to bad alignment. Real bummer, when some of those stock tire made it 60,000 miles.

 

What advantage is gained using -1.0 for autocross? Loosens up the rear end a little?

 

What's recommended specs for a lowered c4s with H&R springs? Just got the car lowered but haven't had a chance for alignment. Thx!

John

 

yup. on concrete with r-compounds, the front camber challenged 996 understeers badly. I reduced the camber in the rear to help it rotate. the rear engined 996 is very good at putting the power down, so i don't think i'm missing much rear grip.

if you autox on street tires or on asphalt lots the 996 can rotate easier and you can run higher camber in the rear or a less aggressive toe.

 

the recommendations for alignment are independent of springs, so search any alignment thread for your desired application (street, autox, DE, etc).

however, with lowered springs you will automatically make your camber range more severe (e.g. -1.5 instead of -0.5 in front, -2.5 instead of -1.5 in rear) which is good for autox and DE and bad for the street. since you want to run it on the street, my guess is you will have no trouble reducing the camber on the front, but will have trouble reducing the camber on the rear with lowered springs without a camber plate. gl