Tire Pressures

[33fromSD]

I know this topic is discussed from time to time, and it is most likely my user error on the search function of this forum but I don't seem to find a lot of info (or at least info I'm envisioning), so I apologize in advance if this has been beaten to death.

i'm running Mickey Thompson Street Comp Tires with 245/40R18s on the front and 305/35R20s on the rear for tire size with FFR's Bonneville rims.

I'm debating in my mind what a good starting point for air pressure is and wondering what other folks have done.

Im guessing with the full fenders/running boards, belly pan, engine side covers and hood I'm ~200-250# heavier than most folks who typically don't run full fenders, side covers, hood or belly panel so last I weighed the car I was ~2600 lbs. The ~200-250#s heavier is only a guess though since I'm also running a SBF 302 which is not overly heavily so other may be heavier i the front with the larger engines they are running.

I've seen a few tire air pressure charts on google which suggest a range anywhere from 25 - 36 lbs given my vehicle weight but I know weight is just a minor factor for figuring this. Tire footprint (surface contact) is more important (Inner - Center - Outer).

I can fine tune as I go but I'm looking for a ball park starting point for pressures for front and rear.

For some reason, everything thing I've seen, and my gut is telling me #28-30 on the front and ~24-26 on the rears would be a decent starting point.

Thoughts?

Any insight or help would be appreciated.

Jim

[NAZ]

Jim, you'll get a lot of varying opinions on tire pressures. Most people guess or try to relate the pressure recommendation from a OEM car with similar tires. But what if there was a way to really determine the optimum pressure for your particular application, would you use it? This short video is the simplest explanation of how to establish the proper inflation for your car that I could find. https://www.youtube.com/watch?v=WGm_dvrJd2E

On the size tires you have I would start at 20 PSI and adjust from there based on tire temps after running a few miles of relatively straight interstate highway at 75 MPH. I find a safe place to pull off the highway and quickly check the temps across the face of the tire. No guessing about it, the tire temps will tell you when the pressure is creating an even loading across the tread. Instead of tread temp some use shoe polish or paint on the tread and look for the wear pattern but I use the temp method.

[RoadRacer]

Thanks for the link NAZ, havent seen that one.

FWIW, I'm running 20psi and get consistent temps across my 285/35 tires.