What's the correct tire pressure??
 

I'm confused on what the correct tire pressure should be. The sticker on the car says 35psi. Guy where I got my tires from said I should go by that no matter what tire is use. Max on my tires says 52psi. I know you should not run at the max psi but 35psi seams really low on my tires. I'm running 215/45/17 tires.


What psi should I run my tires.

I run mine at 35 as per MINI. No issues

Every car has a sticker on the driver's side door jam that shows tire sizes and front/rear tire pressures recommended by the factory.

For you 35 psi front and rear is correct. Tire shops will use this number as a safe starting point, from which you can adjust it a little. It is not too low.

Every tire has on it's sidewall a max tire pressure which is not to be exceeded, this is printed based on the tire itself and has nothing to do with your car.

The worse thing you can do is let tire pressures drop below the recommened level so in street use, try for 35+ psi cold. Once the sun comes out the tire pressures will rise. It is the cold pressure that you are setting. When you drive the tires heat up and pressure rises.

Some owners will put in a little extra pressure to lower rolling resistance but it will firm up the ride a bit.

Even though MINIs do come with runflat tires you can use the same tire pressures whether you switch to non runflats or not.

I run the same tires at 38 psi.

What minihune said is good advice, and 35 is not particularly low. I've had plenty of cars which recommend pressures around 30, 35 sounds quite high to me.

If you're really concerned about it, you can ask your tires, but it takes a bit of work. Each tire is different, so just saying 215/45-17 isn't specific enough, what brand and model of tire? For a recommended tire pressure of 33, I've found tires that liked 32.5, 37, 43 and 48.

The basic theory is that a tire is happiest when its evenly loaded. That will mean all parts of the tire grip the same giving the best grip and all parts of the tire will wear the same, giving the most even wear. If a tire is underinflated, it'll be riding more on its sidewalls. If a tire is overinflated it'll be riding more on its centre than its edges.

The tire tells you how well loaded it is by its temperature. If you havn't noticed, when you use a tire it heats up. The more you use a tire, the more it heats up. So any difference in the load a tire is carrying shows up as differences in temperature across the tire. The idea would be if the centre of the tire is hotter than the edges, its overinflated, if the edges are hotter, its underinflated. This is slightly complicated by the suspension which doesn't work all parts of the tire evenly, it'll tend to work the inside edge more. So usually you're happy if you find a pressure which produces a steady increase in temperature across the tire.

That's how I find out what pressure a tire likes, I have a temperaure probe and take temperature readings across the tire, and change the pressure until I'm happy with the results. This method will get you a good pressure for a particular size/brand/model or tire on a particular car and axle. If you change any one of those you need to find a new pressure the tires are happy with. This works on the road, on the track and for autocross.

I also monitor the tire wear and if the tires don't seem to be wearing evenly I might change the pressures a psi or so to even out the wear.

Thanks for the comments. Extremely helpfully. I'll keep an eye on them more often.

When I switched from run flats to "regular" tires I felt a bit of roll on turn-in, which I attributed to the softer sidewall. I increased tire pressure to 38 psi and have been very happy with the feel.

I ran 38 on the old Hankook Ventus Evo V12 (205/45/17) and currently on the Michelin Pilot Super Sports (215/45/17).

I switched to non runflats and found 38psi works great, still get a much softer ride but got back some of the snappiness with less roll on the initial turn in. A little less squirm on the grooved pavement too.

running michelin pilot super sports, sized 225/50R18 on my all4, i used a tire pyrometer and arrived at 42 psi front and 37 psi rear, both measured "cold" before driving

my winter tires, dunlop grandtrek sj6, sized 205/70R16 ended up at 40 psi front and 35 psi rear

I set all at 39 psi and it's a ton better. Thanks for the advice.

Bless you, your answer hit every question I had and was not finding the answer for! I knew the tire guy who told me 55 was wrong, but then the chart showed a max of 50 & opinions were pretty much confusing. What I didn't know was if switching to regular tires changed the PSI recommendations, so now I know it doesn't I should be good to go. I have always followed what the door indicates but this was the first time I had a car come with run flats (which I took off and put on regular performance summer tires and will use the all weather run flats for the 3 months of "winter" that we have here.
'"