Tire Presure For 335/35 17" & 275/40 17"

[LENSJADE]

What Would Be A Good Tire Presure To Run On The Tire For The Street They Are Mich Tires

[ROUSHAC]

Try 24 psi to start with.

Assuming you have rims that are the correct width for the tires try this. Rub some chalk across the tread and after driving a short distance in a straight line (like the length of your driveway) see if the chalk wore off evenly or left some areas with chalk on them. If there is chalk in the middle, you are too low on pressure. If there is chalk at the edges, you are too high.

Lower pressures will give you a more "comfortable" ride on rough roads, but you don't want to go really low on the psi or the tire will overheat and possibly come off the rim or cause a blowout. For "spirited" driving most folks go a bit higher than the 24 psi.

On the street, I run 24 psi with similar size tires, others run 22, still others run 30. For drag racing I go as low as 18 psi. It's a judgement call on what compromise is best for your driving habits.

[DonC]

I'm running 27 in my 315/35/17 and 275/40/17's and the wear pattern looks good after 16+ thousand.
DonC

[CJ428CJ]

I run 28 psi in the front and 26 in the rear. That seems to work well for my car. The tires have worn perfectly after 18,000 miles.

[jamvan]

I run with both 17" and 15" on my Cobra. Was also concerned which pressures to run as well. Figured would check with the expert, HRE Motors. Billy advised me if running my 17" tires (335 Rear and 255 Front) to go with 32in the Front and 34 in the rear Rear (in warmer weather) or 30 in the Front and 32 in the Rear (in colder weather). As to my 15" (295 Rear and 235 Front), I run 26 Front and 28 Rear.

Based upon the larger 17" tires was told you must run a little more pressure. Good luck.

Jim

[Mulv]

You do not say which car you have and weight is a factor. The consensus seems to be about 24 pounds per 17" tire on a Cobra. Forget about 30 or more, you will wear out the center of the tire. There is no way one of these cars will load that tire to make it sit flat on the contact patch. I have a 6400 pound Suburban with low aspect ratio tires that are only 265 wide and it calls for 30 pounds on the pressure sticker.

If you have a FFR car, their are lots of them in the Bay Area, go to breakfast and ask. I had a SPF car with 15 inch tires and I had 18 pounds in each with 60 ratio TA's. I used 22 at the track. As these cars are virtually perfect 50/50 weight, you want the same pressure in all four tires. Unless you like the "Drifting" style of driving. All of the tires do the same amount of work whilst cornering with equal weight distribution.

You need slightly more in a 17 due to the decreased sidewall height. The best way to check is with a pyrometer after driving the car and not through the opinions of others, myself included. You want more or less even temps across the tire. You can get a pyrometer from here:
http://www.raytek-northamerica.com/c...ekNorthAmerica

They have them at NAPA as well. They are $80- , not a lot compared to the Cobra cost or a set of tires. It is the only way to be absolutely sure you have it right.

If you post the make of car, however, there will be lots of people who have a feel for it and will help you.

Now there will be all sorts of experts to follow to say that you need over 30 in each tire, stay tuned

Here is a photo of my car at Thunderhill with 21 pounds of air in the tires. I am turning through the esses at about 85 mph. Notice that there is basically no tire deflection at all. These cars are not heavy enough to push the tires out from the perpendicular. There is some rear squat as the car had a 427 FE and my foot is at wot.



Mulv - the guy who owned 3 Firestone stores just to get lower priced tires for the Firehawk Series. I'm not cheap, I'm thrifty....