Lowered car - experiencing wear on center section of rear tires - any suggestions?
 

I have KWv3 coilovers and 19' wheels and just noticed that there is significantly more wear om the center section of my rear tires - any suggestions? In particular would appreciate any changes to my current settings that could help (eg increase/decrease any alignment parameters? increase ride height?)
Thanks

Are they by chance overinflated?

I would think they are overinflated as well. Lowering tire pressure by 5 PSI will improve grip and help with your wear issues.

Has to be over inflation. A lowered car usually tears up the inside edges.

thanks for the responses and glad to hear the solution may be as easy as dropping some pressure. I have been running them at 44psi but will bring them down as suggested. I had assumed that the 19s (315/15/19) should be inflated at the same pressure as the factory 18s but maybe not?

Wow, 44PSI?

That's what Porsche recommends?

with KW v3s , 19s and 44psi cold it has to ride very rough. I think you will be surprised what lowering the pressure will do.

I am pretty sure that 44psi is the factory recommended pressure.

And, yes it is a pretty rough ride despite my best efforts to play around with all suspension settings. I can't wait to lower the pressures and ride back home tonight!

By the way, for the fronts, I am running 36PSI which I also recall is the factory recommended pressure and wear pattern seems fine. Should I also lower the fronts? If this works, it is the easiest, cheapest solution I have ever seen for a porsche issue!

36 / 44 PSI is indeed the factory setting. I always wondered how different tire sizes affect this? When I went wider and lower profile on my other car, I actually increased the pressure bit.

Run 36/40 if you are running 18' wheels. If on 19's? I can't remember, but you're sacrificing handling for some misguided notion of bigger is better. but 36/44 is only good with some fat Germans in the back "seats".

Uneven tread wear, in the center, is to some extent normal.

But my experience is while the center of the tire wears faster than the edges the difference in wear is not that great.

Thus as others have suggested over-inflation needs to be considered.

Have to point out I think you need to read the tire inflation pressure fine print.

This subject came up today as I had my 03 Turbo in for a goofy tire problem and the techs told me 36/44 is for a fully loaded Turbo, based on what the tech told me: With 4 adults (!) in the car and full load of luggage. He was reading from the tire inflation decal stuck to the inside of the gas tank filler lid.

Otherwise the inflation pressures are (IIRC) 32/40psi. I'd double check but the car is at the dealer today. (Goofy tire problem fixed along with the squealing power steering valve.)

Sincerely,

Macster.

I checked the manual and the sticker on the car and everything says 36/44 with no further explanation....anyway, I lowered the pressures to 34/39 and the car felt a bit better. Maybe it was placebo effect but it did feel a little softer which is better. By the way, attached is a picture of "why 19s" - I got tired of the factory wheels and simply love the looks of these wheels.

A little lower than recommended is nice in spirited driving as well; you lose grip more gradually (not that this car loses grip easily :D )

That's quite a generalization. So everybody that runs 19" wheels has misguided notions that bigger is better? :confused:

Like the vast majority of people that run 19" wheels, I use them because they look better. And like most people that run them, especially knowledgeable people like you tend to find on this board, I know 18" wheels are lighter and thus generally give better acceleration and braking due to the lower rotational weight and location of that weight closer to the axis of rotation. Most of us also know suspension performance suffers due to the additional unsprung weight. And that the PSM tends to act up more with 19" than 18" wheels. That was a very condescending statement to make about the OP and a lot of other people on this board... :rolleyes:

I've never seen anything that specifies that pressure is for a certain loaded weight either, and in fact would seriously question the engineering rational behind that reasoning. I've never seen a loaded versus unloaded weight used in conjunction with different tire pressures on any car I've ever owned in fact.

The load capacity of a tire is not determined by the tire pressure, it's determined by the structure of a tire. The performance of a tire, especially under high performance conditions our Turbos often see, is definitely affected by the tire pressure. But that's very different than the load rating and relationship to tire pressure.

With respect to your problem OP, I'd also lean towards over-inflation causing it. There's really nothing else that can cause the center of the tire to wear more than the edges. What kind of pressure gauge are you using? I'm wondering if that's simply inaccurate. Have you ever tried measuring the pressure back-to-back with a different gauge to see if you get the same readings?