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03-28-2002, 02:43 PM
Ok, on delivery the car had 33/33. At 1200 mile service the tech juiced it up to like 42/42. Trying to read the label in the door is like reading chinese. I never have more that two people in the car and like to run the car hard I think like 37/ 37 would be ok. Whats your average.

03-28-2002, 02:53 PM

03-28-2002, 03:05 PM
I ran out to Pittsburg the other week-end: three up with moderate luggage and I went 40/45 psi (I think the specified rating was something like 42/47 when it's four up with full luggage). I liked it, cruising at 80 - 105 mph (still in break-in, mind you). After the trip, I moved pressure down to 35/35. Your 37/37 should do no harm. Keep in mind that if you are driving aggressively, a few more pounds in the front over the rear might smooth out the M3 understeer. You might try 37/35. In fact I might keep 35 in the front and drop the rear to 32 psi.

If you're in an area where outside temperatures are varying greatly, keep a close eye on tire pressure. In the Phila. area this week, we'll see a low of 29 and a high near 60. Outside temps affect tire pressure, too.

The old racing rule of thumb for tire pressure was that hot temperature (tires fully warmed up) should exceed cold temperature (which is when you should do your tire pressure guage readings) by 10% and no more. I don't know if that is still true, but something like that must still be the rule: note at races (like F1) the tire technicians constantly taking tire pressures and, even, tread temperatures.

For most of us on the street, I am afraid the differences between 35 and 37 psi, is moot.

03-28-2002, 04:03 PM
Just a little FYI for you. Those rims ride very badly on low pressure, that's why the service tech probably upped them for you. I know I was riding around with 35 for many days, then one morning on the road to work, flat!

The inside of the tire was shredded up and the service guy told me if was because of low tire pressure (I just had the car serviced 1200 mille check up 2 weeks ago, you would think the service guys would check the tire pressure). I hope the service guys didn't lower the pressure, then i ride for 2 weeks, only to pay THEM for a new tire. Sucks, don't it?

Tip: Make sure you always check the tire pressure after ANY type of service.

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