tbone

So I've had the new car since October and just got the tire low warning the other day. Checked the pressure and they were way low. The Conti's say 51 psi max, so I inflated to 45 all the way around, but now the ride seems a little harsh.

I'm thinking of dropping back to 40. What's the general consensus?

I'm driving form Phoenix to San Diego tomorrow so I'd like to dial it in.

Thanks.

EBMCS03

Check the door jam.

Richard in NC

I always do a few more than what the door post sticker shows. I think mine are set to 35/38 f/r or something like that. Unfortunately I can't check them since I'm out of town without the car but the manual shows 32/33 min, 32/38 max loads, and 35/42 max loads and speeds over 100 mph.

BMWSTL

I run 32 front, 38 rear. The car handles and rides well for me.

Lou

monacobmw

I think that 45 psi is way to high. The 51 psi is meant to be the maximum pressure for a safe drive (so the tire will not explode).

Everything comes down to feel. Lower pressure means more flex on the sidewalls to remove the harshness. On the other hand, it can feel sluggish as the same flex means more rubber contact with the road, and your fuel economy goes down.

Most people here go between 32psi and 40psi. If you were going on a long trip, you would want to go to the higher end of the range as you do not need to worry about the feel so much on highways. On the other hand, if you are in the city, a lower psi setting may be better.

I am not so sure of the staggered setting that many have here. The manufacturer also recommends the staggerred setting, but I am not sure of why some use 6psi differences and others use 2psi differences.

Air pressure is one of those nice things that you can do by trial and error at low cost. Good luck with the issues. Oh yeah, I use 36psi in the rear and 34psi in the front. I will probably go a little higher as most of my driving is mixed highway/city.

iversonm

I ran the max (over 100mph) pressures in my old E46, which were 39F/45R. These pressures noticeably improved the steering feel, and probably saved me from a bent rim or two. Surprisingly, the difference in the ride was not significant.

I've hardly broken in my 19" tires on my e60 (as it is wearing snows right now) so I haven't formed an opinion on what I prefer.

Ray Hull

I have the thumpflat 18s but the issue is the same. I always instruct the dealer to inflate them to MINIMUM RECOMMENDED psi. (34/36 IIRC) That way, I don't get my teeth (not to mention dashboard, etc.) rattled over every crappy expansion joint.

Considering that you are in AZ, you don't have to worry about potholes, but rule of thumb here in the Great Northeast is to run winter tires higher to accommodate cold temps and psi contraction as well as protect those rims from potholes.
Cheers,
Ray Hull