Boxter tire wear issues?

[pbxtr!]

I am surprised that my rear tires wore out in less that 6K miles! My dealer installed new Michelin Pilot Sports all around (OEM "Rib" originals) as part of the CPO inspection. The front tires have plenty of tread remaining, but the rear tires are worn completelly on the insides - while the outsides are just past the tread indicator.

Is this normal? Is mis-alignment causing the extreme wear rate- especially in the insides? I toss the car around from time to time but never raced it.

One thing I should note is that the original owner had lowered the suspension (Techart springs) and also did some sway bar upgrades. On top of that, the tires are lower profile than OEM spec. The rear tires are 265-35-18 vs OEM 265-40-18, up front they are 225-40-18 vs OEM 235-40-18. Not sure why but that's the way she came to me.

I am thinking of changing the rears with same tires for now and do an alignment. Longer term, as the fronts wear out, I would change all tires to PS2's of OEM spec sizes.

Any comments and suggestions? At $650+ a pair, they should last at least 12K!

Thanks ... .

[White987S]

Your right foot is also the tire-wear modulator!

6K is NOT unheard of. I have gotten 20K on a set of Pilot Sports (19"). 10-12K is pretty standard. You may need an alignment to extend tread life a little more. But, with the mods, that may not be possible.

What are your cold tire pressures?

[pbxtr!]

I have been aiming for 37psi on rear tires - checking and re-filling monthly. But I just checked them tonight and they were at 32-33 psi. Maybe weekly checks make more sense.

I will look into alignment possibility. Does rear axle have set camber?

Thanks for you reply ...

[geoff]

My '01 Boxster (986) came with Continental ContiSports and I got 27.5K miles out of the rear tires (18" wheels). Both the dealer and suspension shop I use have said the newer cars (i.e., 9x7 models) get better tire wear than the older ones (9x6). I replaced the Contis with Michelin Pilot Sport Ribs expecting to get less wear and was pleasantly surprised to get similar wear (new ones just went on last week). My car is lowered with the ROW M030 suspension and I do a lot of (not slow) canyon driving. The inside of the tires wear a little more than the outsides. I usually get a four wheel alignment every two years or so from someone knowledgeable with Porsches. I also get the tires checked every 6K miles and rebalanced when necessary. I check the air every few weeks (a compressor at home helps a lot). It sounds like your car is way out of alignment, possible due to the suspension mods

Depending on where you buy your tires, some places offer free inspections and rebalancing. I use America's Tire (same as Discount Tire in other parts of the country) and having the tires checked/rebalanced as needed seems to help tire wear a lot.

Did your selling dealer put the wrong size tires on your car to make it CPO? I thought dealers are supposed to follow the Porsche tire rules, including using N-rated tires!

You should also have someone knowledgeable look at your suspension setup to see if the springs match the shocks, since that could also cause excessive tire wear. Hopefully they got the right shocks, springs and sway bars on both front and rear!

[pbxtr!]

My '01 Boxster (986) came with Continental ContiSports and I got 27.5K miles out of the rear tires (18" wheels). Both the dealer and suspension shop I use have said the newer cars (i.e., 9x7 models) get better tire wear than the older ones (9x6). I replaced the Contis with Michelin Pilot Sport Ribs expecting to get less wear and was pleasantly surprised to get similar wear (new ones just went on last week). My car is lowered with the ROW M030 suspension and I do a lot of (not slow) canyon driving. The inside of the tires wear a little more than the outsides. I usually get a four wheel alignment every two years or so from someone knowledgeable with Porsches. I also get the tires checked every 6K miles and rebalanced when necessary. I check the air every few weeks (a compressor at home helps a lot). It sounds like your car is way out of alignment, possible due to the suspension mods

Depending on where you buy your tires, some places offer free inspections and rebalancing. I use America's Tire (same as Discount Tire in other parts of the country) and having the tires checked/rebalanced as needed seems to help tire wear a lot.

Did your selling dealer put the wrong size tires on your car to make it CPO? I thought dealers are supposed to follow the Porsche tire rules, including using N-rated tires!

You should also have someone knowledgeable look at your suspension setup to see if the springs match the shocks, since that could also cause excessive tire wear. Hopefully they got the right shocks, springs and sway bars on both front and rear!

My guess is that the previous owner installed the lower profile tires to make the car even lower - or to prevent rub (the wheels are aftermarket and slightly wider than stock). And the dealer just put the same back on. I noticed that the tires in my car are the 986 S recommended tires. So I can see how the dealer could have had them in inventory.

Based on this forum's comments, the alignment is the major issue here. I will align the 4 corners and get new rear tires. The next time around I hope to upgrade to 19" wheels with 987 approved tire sizes. I like the Carrera S style wheels they offered for the '05 987 (I believe they are called the Lobster claw style).

Anyways, thanks all for your constructive help. More later ....

[Bama]

I would think the dealer would have checked the alignment as part of the CPO program. You might check with them to see if they will help.

[renzop]

Everyone knows that the way you spell Boxster has a significant effect on tire wear. If you leave out the "S" you will get 78% of the wear that adding the "S" in your communications provides.

Seriously, though, Boxsters come from the factory with lots of rear negative camber. Have yours checked and try to get it set to the minimum (-1.4 degrees will be good). Also have the rear toe set to zero. Is your car lowered? Aftermarket lowered rear suspensions can add to the already high negative camber. Finally make sure your tire pressures are checked frequently and run factory or higher pressures.

And don't go to 19" wheels. Extra cost, poorer preformance, less resistance to damage.

Edited December 6, 2009 by renzop

[stef]

Everyone knows that the way you spell Boxster has a significant effect on tire wear. If you leave out the "S" you will get 78% of the wear that adding the "S" in your communications provides.

hahaha :D

op: 6k sounds way too low, but the wear should still be even. If it's not, there's an alignment or suspension issue. bad shocks can wear tires out really fast, too, but you'd probably feel it in a boxSter.

[DamageINC123]

It sounds like we have a similar set up. I have a 1997 with 30,000 miles. I am running 225/45/17 front 265/40/17 Michelin Sport rear on TechArt 3-piece rims with TechArt springs. My fronts are like brand new, but the rear tires have about 5/32nd on the outside of the tire and about 2/32nd on the inside. They are worn evenly accross. I have 8,000 on the tires and hope to get another 8,000 out of them but I am seeing similar tire wear as you described. Mine is not an everyday driver so when I do get it out I am hard on the gas!!

I will say, they are the best riding tire I have had on the car.

[mnc-i]

Reference tire wear on Boxsters.

I have a 1999 Boxster that I have had for three months and put only 1500 miles on it.

I just fitted a set of Sumitomo HRT Z IIs. I purhased this set because I knew before I bought the car that the negative camber in the rear plays havic on tires.

The rear tires (255/40ZR17) only cost me $81.00 a tire via TireRack and the front tires (205/50ZR17) were only $62.00 each.

MNC-I