Tire Pressure?

There ARE "recommended tire pressures" and one would be unwise to deviate
greatly from them without careful consideration and expertise, particularly
in the downward direction.

In the case of the E39 sixes, the lower pressures posted on the door jam are
for normal driving, the higher for maximum rated load. Personally, I think
the "normal": settings are a little low if you run 45/40 or 35 series high
performance tires (particularly for the front) ... not much protection from
a pot hole hit that can ding the rim and puncture the sidewall.

The recommended settings also tend to emphasize the car's inherent (and
designed in) understeer and provide a reasonable compromise between handling
and ride. Bump the fronts up a couple PSI and you can dial a bit of the
understeer out ... a subtle but noticeable improvement IMO.

Bottom line. Check the pressures regularly. Make pressure adjustments
incrementally if you choose to deviate from what BMW recommends. Don't run
underinflated tires (a contributing factor in the Firestone/Explorer debacle
.... yes, the tires were flawed as well). Don't exceed the maximum pressure
on the sidewall.

This advise applies for the 90th percentile driver. For the track (Ala
tech27), all bets are off. Scuderia Ferrari often doesn't get the whole
suspension package (including tire pressures) "just right" and they throw
more at Bridgestone in a weekend than many of us invest in tires over a
lifetime.

R / John

"tech27" > wrote in message
o.verio.net...
> ONCE AGAIN, let's get this understood.
>
> There is NO SUCH THING as the "correct" tire pressure. The only tire
> pressure you need to be aware of is the MAX PRESSURE on the sidewall of
> your tires. Go above this and you risk a blow out.
>
> Other than that you are free to use any pressure you like, depending on
> whether you are looking to enhance handling, traction, tread life, ride
> comfort, etc. Do some research on how pressure affects tire
> wear/performance and you will have a very good understanding of what
> pressures you may want to try INITIALLY. I say initially because you are
> free to tweak the settings to your liking.
>
> While the settings are less critical on my 740, which I do not drive
> aggressively or on the track, they are critical on my M5 and M3. The M5
> sees some track time, while the M3 is strictly track. I adjust the M5
> tires before and during track runs every time I go out.
>
>
>
> "ppp-man" > wrote in message
> news:dJcLd.81920$Ob.72242@edtnps84...
>> Hi,
>>
>> My E39 528 has several tire pressure rating on the door panel. Which is
>> the right one?
>>
>> F/R
>> 33/41 for US/Can
>> 29/33 outside US/Can
>>
>> Does anyone know why is that? And which is really correct?
>>
>> Although it seems clear from the above, it is not so when Canadian
>> garages (BMW Service) insists the 33/41 is too high!
>>
>
>