Sponsored by The Tire Rack

[BMW_335I]

I am confused on what is the correct pressure to use. The manual give 4 differnt options, the door panel has two different options.

Door panel says up to 100mph f 31 r 32 or somthing like that
Door panel says f 38 r 45 or close to that

Basically, a 2001 335I sedan with sport package on stock 162 wheels, with stock runflat tires.

[sleepyx637]

Originally Posted by BMW_335I

I am confused on what is the correct pressure to use. The manual give 4 differnt options, the door panel has two different options.

Door panel says up to 100mph f 31 r 32 or somthing like that
Door panel says f 38 r 45 or close to that

Basically, a 2001 335I sedan with sport package on stock 162 wheels, with stock runflat tires.

If driving under 100mph, use: "Door panel says up to 100mph f 31 r 32 or somthing like that"

If you'll be driving regularly over 100mph (e.g., you're going on the autobahn), use: "Door panel says f 38 r 45 or close to that"

[BMW_335I]

I was thinking if a vehicle is traveling excess of 100 mph, low tire pressure is a must since the tires will heat up and increase on their own. If the door lable says f 38 r 45 for excess of 100 mph, wouldn't that be wrong?

[sleepyx637]

read the manual and dont question it -- it's not that hard ot figure out.

tire pressures for 100mph+ are higher than for <100mph.

[surprise]

Originally Posted by BMW_335I

I was thinking if a vehicle is traveling excess of 100 mph, low tire pressure is a must since the tires will heat up and increase on their own. If the door lable says f 38 r 45 for excess of 100 mph, wouldn't that be wrong?

Low tire pressure causes the tire to deflect(flex) more with each rotation. When a tire deflects the bending action creates heat, the higher the rpm the more bending and the more heat is generated. Therefore, to reduce heat at high rpm's the tire need to deflect as little as possible=higher tire pressure. Trust German autobahn engineering experience, they know high speed driving.

Take a look at the following article: http://www.tirerack.com/tires/tirete....jsp?techid=72

[sleepyx637]

Originally Posted by surprise

Low tire pressure causes the tire to deflect(flex) more with each rotation. When a tire deflects the bending action creates heat, the higher the rpm the more bending and the more heat is generated. Therefore, to reduce heat at high rpm's the tire need to deflect as little as possible=higher tire pressure. Trust German autobahn engineering experience, they know high speed driving.

Take a look at the following article: http://www.tirerack.com/tires/tirete....jsp?techid=72

+1. Much better stated than my "don't question the manual" crap.

[Gary@TireRack]

Originally Posted by sleepyx637

read the manual and dont question it -- it's not that hard ot figure out.

tire pressures for 100mph+ are higher than for <100mph.

+1