ricrose

I'm sure this has been covered, but, hey, I missed it.
Those of you with runflats... do you follow the recommendations in the manual that suggest that the tire pressure sensor should read 30psi after 15 minutes, or do you use a good old tire gauge and inflate to 40 - 44psi as suggested on the tire?

goldman

I thought the recommended was 30 PSI when COLD.
I've compared my sensors with a gauge & they're very accurate.

40-44 is definately too much!!!

barryscott

Hey Now:
Go out and buy yourself a good digital tire gauge and inflate the tires to 30psi cold. Your pressure on the DIC should be within a few pounds. The 40psi on the tirewall is the maxium pressure you could run. :yesnod:

Smoke-N-Shot

I set my tire pressure depending on what time of year we are in... The objective is to set the pressure so that it will read 32 PSI after your tires get hot from driving... For example, this time of year mine are set cold to 27-28 PSI... when heated from driving they get to 32 +/- 1lb. During the colder weather, I set them to about 31 lbs and they get to 32 most of the time. IMHO, you just can't run the same PSI year round...:chevy

Nick :cool:

Jim 47

A very intelligent and excellent answer to a probing question, Nick. Keep up the good work and advice.

Jim Helm, Pewter 2000 FRC :yesnod:

silversport

30PSI Cold (before ANY driving)
40PSI on sidewall is MAXIMUM pressure
Higher PSI BOOM/CRASH/DEATH/MAYHEM/SWARMS OF LOCUSTS/BAAAD!!
:chevy

MDT

ricrose,

As stated above the 44 lbs on the side wall is maximum pressure.......don't inflate to that #. :eek:

I inflate mine to 32 lbs cold. As they heat up in driving that will increas by 2 or 3 lbs.

Pressure should be corrected seasonally. The rule of thumb is: 1 lb increase in pressure for each 10 degree increase in temperature and conversely.

The decal on the door jamb recommends 30 lb cold inflation pressure. I personally think that a couple of extra lbs helps prevent shoulder "scalloping" without causing proportionate wear in the center area of the tread, but I know others will disagree with that, so it comes down to personal choice.

Good luck.
Mark

vette2001c5

Mine start out about 27-28 cold and get up to 30-31 when warm.

rcwalters

I don't agree with this. If it is winter, say 30F, then you would need to put more air in to reach 30psi cold. Then when you drive, the rolling resistance, etc will raise the temp a certain number of degrees above ambient, thus raising the pressure a few degrees. If it is summer, say 90F, then you would need to let some air out to acheive 30psi cold. Then when you drive, the rolling resistance is still the same, so it would raise the temp the same relative to ambient as in the wintertime. So no, you should run the same cold pressure regardless of season, because the psi at ambient temp already accounts for the temp differences.

Evil-Twin

try measureing the road surface temp on a black top road on a 95+ day.. the road temp can get to 160/180F.
on a winters day the road temp can be as low as 27F. You acually think that makes no difference???? gezzzzzzzzzz I cant touch my tires , they're so hot in the summer..... in the winter its a completley different story..Hot air expands increasing pressure.. Go to a balloon shop in the winter..take them outside in 30 dregree weather... they loose half their pressure.. bring them in the house at 80 dregrees and they are all blown up ful again... sorry I am so freekin long winded.. My apologise to the forum..

rcwalters

Hmmm, road temp. I was only considering the ambient temp difference, which would make no difference.

MDT

Each time you check the cold pressure, adjust it to 30# or whaterver # you decide to run.

If you run 30# on cold pressure when abient is 100 degrees, then when the ambient falls to 20 degrees in winter the pressure will drop to aproximately 22#. This is true even if the car is just sitting in the driveway.

There is reduced molecular activity associated with the air in the tires because of the reduced temp. The example with the balloons above is a good one.

I think everyone may be saying the same thing in a different way.

In summary......use the same cold inflation pressure year round....it will change within the tire seasonally.

More tires are ruined from under inflation than over inflation. Regular tires have more flex in the side walls, thus generating heat, which can lead to blowouts.

There is little sidwall flexing in the Run Flats.....everyone knows those side walls are made of solid oak.

Mark


[Modified by MDT, 12:04 AM 8/12/2001]

ricrose

Thanks for the help, everyone. Gee, this is a great forum.
Now, if I can only figure out which exhaust to get... :hat


[Modified by ricrose, 3:48 PM 8/12/2001]

darkmercury

Cold at about 28-30... Driving during this time of the year goes to 32-34...

Fronts are always 1 psi lower than the rears...

Get a digital gauge because it really does help!!! :cool: :cool:

Chopper Larry

FWIW; I'm getting ready to replace the rears (I'm on my second set of tires, replaced both at 25K, now at 49K); I kept 32 (psi stone cold) all the way around and the front did fine; the rears wore prematurely in the centers, so I'm going with 28-30max(stone cold) in the rear. Always check the pressure before startup.

Evil-Twin

I would suggest you check tire pressure after the tires are warm.. cause thats the pressure they see most of the time.. if it get above 32 psi you run the risk of wearing the centers.. I run 30 psi max.. when they are hot..at running temp..

Smoke-N-Shot

Your response is not quite clear to me sorry... You start to say> "If it is winter, say 30F, then you would need to put more air in to reach 30psi cold" (OK that is what I am saying...)

Then you go on> "Then when you drive, the rolling resistance, etc will raise the temp a certain number of degrees above ambient, thus raising the pressure a few degrees. If it were summer, say 90F, then you would need to let some air out to achieve 30psi cold. " (Ok, that is what I am saying...)

Then you go on to say> "Then when you drive, the rolling resistance is still the same, so it would raise the temp the same relative to ambient as in the wintertime. So no, you should run the same cold pressure regardless of season, because the psi at ambient temp already accounts for the temp differences." (I respectfully disagree for you are not taking into account road surface temperature, which will be the biggest variable in your tire pressure. Yes, rolling resistance will be the same but road surface temperatures could reach some extremely high temps due to heat absorption from the sun. With this high road surface temperature in the hot weather VS cold weather, it's like night and day... simple physics...)

Nick :cool:

I don't agree with this. If it is winter, say 30F, then you would need to put more air in to reach 30psi cold. Then when you drive, the rolling resistance, etc will raise the temp a certain number of degrees above ambient, thus raising the pressure a few degrees. If it is summer, say 90F, then you would need to let some air out to acheive 30psi cold. Then when you drive, the rolling resistance is still the same, so it would raise the temp the same relative to ambient as in the wintertime. So no, you should run the same cold pressure regardless of season, because the psi at ambient temp already accounts for the temp differences.[/QUOTE]


[Modified by Smoke-N-Shot, 9:31 AM 8/16/2001]

Smoke-N-Shot

Thank you for your compliment...

Nick :cool:

Chopper Larry

Run the same pressure each season, but you do need to add or remove air each season to maintain that same pressure. This sounds like double talk. LOL.

Len16

I suggest you try several pressures and see what ride you like. There isn't any exact "right" pressure.

Set the pressure on a weekend and drive it for a week. Re-adjust the following weekend as necessary.

My final preference was 30 psi operating (hot) pressure. This corresponds to about 28 psi cold (depends on the time of the year).

The 30 psi pressure gave me the best combination of handling, comfort and tracking.


[Modified by Len16, 9:04 PM 8/17/2001]