[ledfoot]

Hi All,

I had a set of Pirelli PZero Nero M&S (non-RF) tires mounted on my wife's '06 330i at about two years ago @ 25K miles and had a 4 wheel alignment done at the same time.

After approximately 26K miles on the Pirelli's, the fronts seem to still have an even 50% tread left but I was surprised to find the rear tires are severely worn on the very inside (about 3/4" from the inboard sidewalls). The center and outside of the tires look to have about 50% tread left, but the badly worn inner section requires that I change out both rears tires prematurely.

It's very odd wear, where you can feel a 25 to 30 degree angle all of a sudden when you reach towards the inside of the tire with your hand, while the rest of the tire seems to be wearing evenly.

I originally chose the Pirelli PZero Nero's because they have a fairly stiff sidewall and higher load rating to ensure they were similar in stiffness to the original Bridgestone Runflats (which I didn't love). The original rear tires did wear completely even both front and rear, with the rears giving up a bit before the fronts.

Could this simply be an alignment (camber and/or toe) or an issue exacerbated by the stiff sidewalls and possibly a tire pressure problem? I would have assumed if tire pressure was the problem, the wear would have been down the center, or close to it, not on the inside edge.

I'm running the stock tire size for the E90 330i sport package rim:
P225/40ZR-18 at the front
P255/35ZR-18 at the rear
I run 32psi at all four corners (cold).

Anybody else seen this same issue?

[200Duece]

inside rear tire wear is normal on our cars as you know. the lower pressure that you run is a contributing factor. the lower the pressure the more the edges of the tire wear. the higher the pressure the more the middle will wear. you could have the rear camber lessened to help a little also.

When you say you got a four wheel alignment did you have it set to the factory specs or to zero out the rear camber?

[ledfoot]

The four wheel alignment put the camber back to factory specs (which includes a bunch of camber .

I may try more air next time, in addition to checking the alignment.

[200Duece]

more air, less neg camber

[DESI4life10]

I believe that BMW run a bigger negative camber in the back for increased handling.

When I got my alignment, the backs were about -1.5 degree in camber and that was in spec.

I am not sure how much thread wear a -1.5 camber does on a tire.

[chaz58]

I have to congratulate you for noticing this. Most people would be oblivious until they are down to chords!

But yes, more air, less negative camber would help the tire wear. I can't tell very well from the picture, but it looks like you are getting a decent amount of wear on the outside treadblocks, which tells me you could stand more pressure. If I'm wrong, and there is an even increas in tread depth from inside to outside, then pressure won't help much. And yes, Toe could be a factor here too.

[chaz58]

I'll have to dig up the specs somewhere.

1.5 camber on the rear can cause noticeable tire wear. Anything over that could get extreme.

I don't know the BMW specs, but on my Miata I run -1.0 up front, and -1.5 in the rear. This is set up for aggressive street driving, and is a bit mild for the track (and a good compromise for me).

Will less rear camber kill your handling? If you are running staggered tires on a stock suspension you have a bit of understeer dialed into the car. less negative camber will remove some of the understeer.

While this may not be good for the average driver, it will be a good thing for someone looking for more performance.

Originally Posted by DESI4life10

I believe that BMW run a bigger negative camber in the back for increased handling.

When I got my alignment, the backs were about -1.5 degree in camber and that was in spec.

I am not sure how much thread wear a -1.5 camber does on a tire.

[DESI4life10]

Yea I just looked at my recent alignment sheet ( 2 months back) to check the specs.

For the rear, the OEM spec is set at -1.5 degree camber. The fronts are set at -.5 degree with an upper limit of -.8 degrees.

I know that the rear will have premature wear, I am curious to see how fast it will happen

[mike-y]

-1.5 should be fine for a street car - as long as your toe is set properly, and you run enough pressure. My car specs pressure to be higher in the rear fwiw. I normally run 1-2psi more all around because it increases turn in response (33/36psi f/r).

I've run up to -2 degrees camber up front on a street car and got minimal uneven tire wear, if any with the toe zeroed out. By the time the inside tread was bald, the outsides had 1/16" or less. BMW specs more camber in the rear to increase understeer and make the car easier to handle for average drivers. I'd imagine there is a bit of toe-in spec'd for the rear too (common on rwd cars). Toe causes more wear than camber does, but people still blame it on camber because you can see it easier.

imo, -1 degree is very mild, and you will wear the outsides of the tire if you like to throw the car around in the corners.

[chaz58]

Here are the BMW specs (from Harold). Nothing too unusual for a RWD car although personally I would be happy with a smaller difference between front/rear camber (i.e. more negative camber up front). For the average joe, it does make the car a little safer having a big camber spread front/rear.

Front:
Toe: 0 14' + or - 10'
Camber: -33' + or - 20'
caster is not adjustable
Rear:
Toe: 0 18' + or - 6'
Camber: -1 50' + or - 15'