uneven tire wear. Need ideas!!!!

[Smurfskier]

So I brought my car in to the shop to have an inspection done and my pilot super sports I put on at the end of last season are totally worn down to the cords on the inside edge. We put the car on the alignment rack and everything looks good. Camber is -2.5. The outside and middle of the tires are like brand new. I only have about 6000 miles on these tires. The fronts are perfect. Just want to try and figure this out before I put a new pair of tires on the car. Oh and it is the rear tires I am having the issue with.

Any ideas appreciated.

oh and the car is a 2003 3.0 roadster with 109,000 miles. I have eibach springs with Koni shocks that are under a year old.

[aerobod]

Originally Posted by Smurfskier

So I brought my car in to the shop to have an inspection done and my pilot super sports I put on at the end of last season are totally worn down to the cords on the inside edge. We put the car on the alignment rack and everything looks good. Camber is -2.5. The outside and middle of the tires are like brand new. I only have about 6000 miles on these tires. The fronts are perfect. Just want to try and figure this out before I put a new pair of tires on the car. Oh and it is the rear tires I am having the issue with.

Any ideas appreciated.

oh and the car is a 2003 3.0 roadster with 109,000 miles. I have eibach springs with Koni shocks that are under a year old.

What was the rear toe and thrust angle value measured? Also, was that -2.5° camber value with 68kg of ballast in each seat, 14kg in the trunk and a full fuel tank? If ballast wasn't used, your rear camber will be about -3.0° when measured to BMW specs, about 1.0° too high, leading to higher wear than stock on the inside edges of the tyres.

[seank]

I am going to agree with Aerobod. 2.5 degrees of camber with a soft tire means you replace them every 6 months. Toe-in will also add to this.

I run them for 6 months and then flip them .

[Smurfskier]

they definitely did not weight the car down when doing the alignment. The machine gave them the specs for everything. I will have to get the printout to find the rear toe and thrust angle.

[Smurfskier]

the pilot super sports have a defined outside and inside not just a rolling direction so you cannot swap them to make the insides outsides. might have to switch to a different tire.

[blender]

You wrote "..the fronts are perfect..." so I surmise you are running -2.5 or more at the back. Why??

You might want to reconsider your target alignment specs before you burn through another set of Pilot $uper $port shoes....The factory alignment specs leave a lot to be desired. There are great alignment setups described on this board for different applications, For instance: going -2.5 at the *front* and -1.5 or so at the rear makes a great (mild track or canyon carver) setup.

Also - have your shop use ballast when aligning, or just sit in the car. The weight of the driver really does affect the result.

[v3.2mc]

^ the non-///m cars have more aggressive alignment than the ///m cars do. this is mostly due to the differences in rear suspension geometry, and BMW's attempt to get the standard z's to carry speed though a corner making up for a "lack" of acceleration (if you can call it lacking). running -2.5* in the rear is just fine for this application.

i agree on toe specs and proper ballast during allignment. a small amount of toe-in is a good thing though... the car won't turn as nice and it'll be a bit squirrelly at speed (as a DD) with 0 toe.

[davesz4mc]

Shocked noone has asked but what tire pressure you set in the rear tires? sounds like you need to let some air out to get some more rubber on the ground.

[Smurfskier]

not sure .... since they have already been removed. should have been 36 lbs