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[wtzouris]

It's 6 degrees in NYC, and everybody in my family is getting Tire pressure warnings...on Subarus, Toyotas, Fords, etc... I am running 33 psi in the front and 36 psi in the back of my 128i coupe. I check tire pressure in the morning after not driving the car for 6-8 hours. I would say I check it once a month.....Anyway, I've noticed all of the tires I've checked/filled in the family are 22-26 psi, which is setting off the warnings. (Because nobody else owns a gauge or does any maintenance!)

If I inflate the tires properly (say 34 psi for a Subaru Legacy AWD) while outside in 10 degree F weather (cold tire pressure), will the tire pressure go up when the weather warms up to 40 degrees? Will I need to bleed off some of the pressure then? I used to garage my car in the winters so I've never really though about the air temperature when inflating the tire.....

William

[AlienDNA]

Yes, you'll need to let some air out when the weather warms up. Living on Toronto can be a pain in the winter because one day it'll be -10 and the next it'll be +10 and you have adjust pressures on a daily basis. Not so much lately though - I guess this extended deep freeze does have one benefit...

[bimmer74]

I inflated the tires in my wife's Subaru Legacy to 34 PSI when it was around 50F. It was 0F here yesterday morning and no TPMS warning yet. It did trigger a warning before when the pressure dropped to about 25 PSI in lower temp.

[JME]

If you inflate the tires to proper temperature at 10 deg, they should still be ok at 40 deg (though you might start getting some uneven wear on the tread surface.) However, any warmer and you might want to consider bleeding it off. I'm not sure how much pressure you can put in that specific tire, and I don't want you to find out the hard way. But you should be good for a 30-40 deg temp change.

[ZIPNBYE]

Originally Posted by DanW

I inflated the tires in my wife's Subaru Legacy to 34 PSI when it was around 50F. It was 0F here yesterday morning and no TPMS warning yet. It did trigger a warning before when the pressure dropped to about 25 PSI in lower temp.

It triggered a warning not due to the absolute pressure, but a difference in pressure between the four tires.

The TPMS systems (sensors in the tires) only report warnings when there is a difference in pressure between one (or more) tire and the remaining (three or less) tires. You could have all four of your tires at 10psi, 20psi, 30psi, or what-have-you, and so long as they're all even, no warning will ever come on. If however, one is at 24 and three are at 25, you'll get a warning.

[bimmer74]

That depends on the TPMS type used. The Subaru (it's a 2008) has direct TPMS with radio sensors mounted in each wheel. The system monitors all the wheels and should be able to detect tire pressure decrease in any number of wheels, including in all four. The 1 series has this type of TPMS.

Some cars use indirect TPMS which compares rotational speed of all the wheels with the use of ABS sensors. Those systems obviously won't be able to detect uniform pressure decrease across all four tires. I believe the 06 3-series has this type of TPMS.

[Guildenstern]

I had a TPMS alert when all 4 of my tires went low during the first cold snap. They were all equaly low.

Are you confusing TPMS types? Tire Pressure Control (dohickys in the tire, RDC), and Tire Defect Indicator the DWS system (Uses ABS to detect an off speed and therefore low tire, aka RPA)

My understanding is that Canada did not mandate the In tire RDC system, where as the USA did. You may be comparing apples to goldfish.

[boxerdog]

I'm in Minneapolis and that was an issue for me also until I found a tire place that used nitro instead of air. I have that in my winter set and they haven't change at all.

[Guildenstern]

We gotta open this one up again?
http://www.1addicts.com/forums/showt...light=Nitrogen

[JME]

Oh god. Nitrogen. I hope you didn't spend too much money. And by too much money I mean "any" money, lol.

[Tom K.]

Originally Posted by JME

Oh god. Nitrogen. I hope you didn't spend too much money. And by too much money I mean "any" money, lol.

I always give my tire guy a generous tip for his special blend - which is 78% nitrogen.
Tom

[canlefty]

Originally Posted by Tom K.

I always give my tire guy a generous tip for his special blend - which is 78% nitrogen.
Tom

Damnit! beat me to it!

I always talked about opening my own line of tire filling machines marketed at 78% Nitrogen, then charging a price between what the "full" Nitrogen guys charge and a typically labeled air pump.

All I'd need to do is give a test unit to a typical (less-than-informed) "auto journalist" from the NYTimes and I'd be laughing all the way to the bank.... You'd think I would give most people the benefit of the doubt, but then again there are people still buying domestics, so the market is really already there :biggrin:

[Tom K.]

Originally Posted by Guildenstern

I had a TPMS alert when all 4 of my tires went low during the first cold snap. They were all equaly low.

Are you confusing TPMS types? Tire Pressure Control (dohickys in the tire, RDC), and Tire Defect Indicator the DWS system (Uses ABS to detect an off speed and therefore low tire, aka RPA)

My understanding is that Canada did not mandate the In tire RDC system, where as the USA did. You may be comparing apples to goldfish.

Incidentally, BMW speak for the two is TPM (Tire Pressure Monitor) for the separate in tire sensors, and FTM (Flat Tire Monitor) for the ABS sensor wheel speed comparison. The '08 U.S. 1er manual lists both with asterisks (optional equipment).

Tom