ML55CLA45

my 240 is sitting on 225/40/18 ps2... the maximum psi is 51. any recommendations as to how much i should fill them up? i have them all at 40 now, should i fill them up to 51?

-thanks
Carino

vadim

51 is the *maximum* allowable pressure beyond which the tire would disintegrate - why would you want to stress your tires that much? I imagine they would be bouncing off the pavement like basketballs inflated like that. Even 40 is way too high for a street use. Something around 30-35 should be fine - play with it and see what you like, paying attention at ride and handling.

markseven

Remember, as your tires warm up, the air pressure will increase as well. On top of that, add 1 pound of pressure for every 10 degree increase in ambient temperature. To keep that in perspective, during the summer months in SoCal, you can expect an increase of 3psi just from the rise in ambient temperature.

-Mark

tmak26b

look in the fuel filler lid, it tells you your recommended tire pressure

ML55CLA45

hey guys thanks for the input....


i know the recommmended tire pressure is inside the fuel door.... but am i safe to assume that those numbers are for the factory tires. the factory tires are 205/55/16 with a max. psi 44. the recommendation on the fuel door is 28 in the front and 32 in the rear... with my 18's should i use this recommended psi?

ML55CLA45

yeah... PV = nRT... with volume and moles held constant.... pressure and tempurature are directly proportional

thanks for the advice man-

amdeutsch

Yes. That would be your starting point. From there you vary it to your liking and driving characteristics (oversteer, understeer). Luke from the tirerack addressed this on various occassions in the tire forum. You might want to search there for additional info.

vadim

I would not run the *recommended* pressure in your case. Tires are less expensive than rims. 18" hi-performance tires have shorter side walls compared to the stock 16" all-season touring tires. This means that there is less buffering to protect your rims in case you hit a pothole or any other obstacle on the road. Plus, the recommended tire pressure is for the *average* driver, it is intended to provide a comfortable ride above all - clearly not the case with your 18" rims fitted with low-profile Z-rated tires. My advice would be to start with 36R/32F and play until you find a good balance between ride quality and handling. You are the only judge here. While at it, search the web on how varying tire pressure between the front and the back affects understeer/oversteer.