Simple question really, stock sizes on an FD ask for 32psi. If I'm using 255/35ZR18 and 285/30ZR18, should I run more or less pressure? I'm trying to find the right pressure to run.

I need to generate a little more over-steer as well so how low can tire pressure go before the tire wear funny?

 

From my experience DD'ing a Cavalier with bike tires, anything over 8-10 psi will wear the center of the tire quicker than the edges. I was running 45psi front, 40psi rear on 195/70R14 tire to minimize tire roll and it took 8-10k miles to measure a sizeable difference (1/32").

I would try raising the rear pressure, but I doubt that will fix the handling problem. From experience racing an idiot friend's E46 328i with staggered tires (235/255), you aren't going to make the car neutral without either taking away grip from the rear (essentially making the car slower), or making enough power that you get throttle-on oversteer.

 

It's a simple question but finding the answer is not.

The stock FD pressure is based on vehicle weight and wheel size. Mostly vehicle weight. So 32psi is a very good starting point.

To get the perfect tire pressure you should get a temperature gauge and adjust pressure until you get a consistent tire temperature across the width of the tire. Depending on camber it may run hotter on the inside, but you want a smooth progression of temp. Too cool in the center, run more pressure. Hottest in the center, run less. Yes, it's a pain in the rear for a street car but if you don't get to it, then run 32.

 

usually it's 1psi for every 100lb.

 

That would make sense seeing how the FD's gross weight is 3200, therefore 32psi.

Is it really that difficult to get a neutral setup while staggered? Because if a staggered setup is supposed to understeer a little then that saves me the useless trouble of hunting for neutral.

 

I've good results following Howard Coleman's recommendation for those size tires.

F = 30 psi / Rear 28 psi

Jack

 

I do 33.5 front, 31.5 rear

I have 17s though. When i first got my wheels, they came with 39 all around and it felt harsh.

 

Pressure varies by the internal air space which is affected by width and radius.
Smaller tires need more pressure and larger less for the same load.

If you go from a 225/50-16 to a 235/50-16, the pressure should be less.
But a 225/50-16 to 235/45-16 might require more or the same.

Best to call the tire manufacturer tech section and talk to them.

Yokohama suggested 34psi for my 245/40-17 fronts and 26psi for my 275/40-17 rears.
And they have done great with that recommendation.

 

hmm i have the same rear width size tires, gonna bump the rears down to 27 then and see how it drives.

Thanks for the advice.

 

i definitely think it all depends on your driving style, what kind of tire temps you're seeing on a regular basis.

A lot of this is dependent on the climate and so forth.

Do you have coilovers?

Also keep in mind that tires with stiffer sidewalls tend to have higher pressure tolerances as well.

So I would ask you:

1. Are you setting this up for Daily Driving?
2. What kind of temps do you see during the day when driving?
3. What tire model are you using?

4. Why not adjust suspension to get it to do what you want?

I would setup tire pressures based on feedback via a pyrometer, as mentioned above.

Rishie