cagthuzz2807

Hi, I just installed 20 inch wheels on my car yesterday that has been lowered with h&r sport spring..

What is the recommended pressure for those setups?

thanks! I appreciate it..

Tacklebury

I have 20' ACS Type 4's. 255/30/20 & 295/25/20. I use 40psi in the fronts and 45 psi in the rears.

BMW filled to these levels and i maintain them at that level. My tires are Michies PS2. They ware wearing brilliantly.

Glock-357

That seems a bit on the high side. I think when they are mounted the installers seem to always put too much air, probably to seat the bead good on the wheel.

Since I could not find that answer on any board or WWW search, I figure just follow the label on the inside of the door (even with different size tires).

Mine were set that high or higher (49 in the front?) and when I finally double checked them and realized this (gee that is why all the road noise). Now sitting at 38.5 all around and can probably go down to 36 (which it states on the door),but thinking that the label states those pressures for less than 100-mph and 41 and 46 (which I think are too high) for over 100-mph, 38.5 seems like a good compromise since it is a challenge to keep this car below that .

My recommendation FWIW would be to start at 38.5 and watch the tire wear. At the edge of the sidewall there are wear indicators. Set pressure, clean your tires, reset TPM or FTM, go for a spirirted ride and check. Ideally you want to be right at the edge to get the most from a handling persepctive or slightly less since you may drive even harder at times.

Less pressure = better ride and handling (within range)
Higher pressure = better MPG, more road noise and stiffer ride, apparently better for high speed??? (within range).

Too high or low of pressure could make it easier to damage the wheel. Too high = more impact on the wheel (i.e. potholes, etc.) Too low = possible direct wheel impact or even losing the seal at the bead if really low. I read one post where posters were increasing pressure at the track to prevent too much sidewall roll on 20's due to the lower profile tire.

38.5 seems ideal for now but still a little noisy and with some room on tread wear 36 might be fine.

Anybody else have any input, since the subject does not seem covered hear or anywhere else, now would be a good time...

*All of this is COLD tire PSI of course.

Tacklebury

Remember that 20's have very small profiles, hence the high pressure to help with potholes etc....

jbsapphire

Theres this Max Pressure-10% Theory. It states that use pressure less 10% of max allowable on the tyres side wall. Check this out http://www.carbibles.com/tyre_bible_pg2.html .It'll give you much more that just tyre pressure.

Tacklebury

Interesting read.

Working on the 10% rule seems to work for me, yes its a harder ride but the E60's suspension makes up for the loss. It still rides 10 time better than the misses Seat!

jbsapphire

Been using the 10% theory for sometime now. Works for me. Tacklebury: Glad you find it useful