Tire Pressures and Wear

[ehljags]

What presures are being used?

I have 18" Contisports and run 29# front and 36# rear (cold).

How often should the pressures be checked? My dealer-mechanic advises every week or gas fill-up. I have notieced if I lag a couple of weeks, the rears drop around 6 #s and the fronts around 3-5 #.

I have around 10,000 miles -- what life should I expect? I am a relatively aggressive ( ) driver.

Also, am not sure what tires I will get next. Thinking about Yoko-AVS, Contisport II, or P-0. Alternatively, I might lighten the expenses and go with Khumos. Any recommendations?

[JT]

As with most performance tires, the rubber is really soft. Thus, the life of the tire will be much shorter than regular driving tires. I have heard that you should get about 25k out of your tires. Cant really say since my car only had 4800 miles on it.

JT

[donv]

Is there any rule of thumb for adjusting the tire pressures for different driving conditions?

I raised the pressure in the tires before winter storage and the "flat spot" problem was much better this year (not perceptible). So much so, that I forgot to let the pressure down and have been driving around with ~40# (just below the MAX pressure on the sidewall) in both F/R since.

The steering seems crisper, but the ride is definitely harsher. I know the manual recommends 29# F / 36# R, which I expect is for "general" driving. It seems there's a Boxster "Hack" for everything - are there some accepted different values for tire pressure for improved handling, or reduced treat wear, etc.?

[ehljags]

Tire pressures are a personal thing. As you stated, increased pressure will give a harder wide - especially with 18" wheels. You will also notice more internal wear (center of tire). Similar, under inflation will wear tires on the outsides (both inside and outside). I have played around with pressures and have found 29/36 seem optimal for handling and wear. I just changed tires at 16,000 miles (P-Zero Rossos)

[mjbliemel]

I have been running my 17 " Bridgestone Potenza SO3s with 32 in the front, 34 in the back. I am thinking about going back to the standard recommended 29/36 tire pressures though after reading these posts.

I was having some serious alignment issues which I finally got taken care of recently. Now the car rides much better after having an alignment done, but as a result of ignoring the alignment problems I wore out the rear tires (as you may recall I was getting some extreme scuffing and abrasion on the rears) after only about 6000 miles.

Put on a set of new rears, then had the alignment done and all is well. The SO3s on the front with about 6000 miles look almost like new, they seem to be wearing really well. I really like the ride and handling of these tires, can't recommend them enough.

I also had them balanced last week on the Hunter GSP 9700. The balance is still not right though, need to take them back and have them checked again. At high speeds I get way too much steering wheel shimmy and vibration. I know it could be something besides the tire balancing, but will have them recheck that before I look at other possible causes.

[jfmillr]

I have spent the better part of this last year riding on BF Goodrich GForce T/A 's and after playing with pressure in the front and back tires I like the factory recommendation of 36 in the back.
36 in the rear gives a strong rear stance and gives little play when hard accelrating from a stop. But in the front I like it a little softer and have lozered it to 28 instead of 29(factory recommended). I am a fairly aggressive driver and like the added response a little less pressure gives the little additional comfort in the front end on some bumpy roads.I am running on 18" with 235/40/18 in the front and have gone to 275/35/18 in the back.
As for checking air pressure, I recommend carying a good gauge in your vehicle and check your air visually everytime you fill up your car, and checking it with a gauge every other time I fill up. I dont have any leaks but find when I drive a little hard on the vehicle from time to time one or two tires at a time car change slightly and your Porsche doesnt like riding with a different Psi and can ultimatly cause bad tread wear.

[ehljags]

Excellent idea with "fueling" and "pressure-checks." One item of importance: tire pressure mesurements will change significantly with temperature: Recommendations are to check the pressure cold and not at operating temperature(hot rubber). I have found as much as 4-5 psi increase on hot tires.

Mike -- be sure and have your tires balanced at very high speeds. Most tire stores balance around 60-70 mph. Need to have themn get the machine spinning at much higher (maybe 140-150-ish, hee hee)

[mjbliemel]

Had the tires rebalanced yesterday, now I am pretty content with how the car is riding and handling. Had it briefly up to about 110 yesterday on the ride home, it felt really good and solid on the road. Top down, nice warm Southern California day. I have gone back to 29/36 tire pressures for now. Gotta say the SO3s are great tires, I really love them. There was another AS/Blk/Blk Boxster in the bay yesterday when I went to have the tires rebalanced. Owner was apparently not around, so didn't have a chance to chat.

[red*farm]

here is a good article

http://www.rennlist.org/996_faq/b.htm

[donv]

That link is a good one, thanks!