Got into my car yesterday (Saturday) morning (08 MCSA with 1500 miles on it, Conti runflats on 17 inch S-lites), started it up, and was presented with a RED tire pressure warning! Didn't drive it at all Friday, and my usual 25 miles or so on Thursday, nothing memorable.

A quick check with my (digital) tire pressure gauge showed 3 of 4 tires at either 36 or 36.5 PSI. Left front was 36.5 but the left rear was 30!

Couldn't feel or see anything amiss with the tire. Filled it to 36 PSI and went through the reset procedure. The red warning cleared immediately, and the yellow warning on the speedo cleared in half a mile or so of cautious driving.

Rechecked tire pressures when warm after some driving, and all were similar.

Checked again (cold) this morning, and left front is 36.5, left rear (the problem child) is still 36.

1500 miles, nothing palpable on the tire. Looks like pressure is holding.

One piece of information I don't have, is what the tire pressures were when I picked up the car.

One scenario is that I've got a slow leak of some kind.

The other scenario is that this tire has been low from the beginning, and just dropped below the trigger point.

I'll recheck tire pressure in the mornings -- any suggestions on other things to look for? Should I dismount the wheel and give it a bath?

 

Might be a valve stem...

We've got a similar "slow" leak on our '06 MC. One tire drops about 5-7 lbs in about 10-12 days. I've checked for objects in the tread and sidewall, but don't see anything. So, I assume it is a slow leak in/around the valve stem. I've noticed the stem hissing at times after checking pressure. I usually check pressures about every 7-10 days (just before the pressure drops to the threshold point of setting of the "flat tire" indicator) and set all to my usual running pressure and move on.

 

Keep an eye on it, but when my car was delivered it drove fine for a few days. Then when I was out in the middle of nowhere the tire pressure warning went off. I had a compressor with a cheap gague and checked all the tires. The front left was really high, and the other 3 were OK. Once I made them all similar and reset the warning indicator everything was fine, and still is. I did check and correct the tire pressure after cold later in the evening. After a year still no problem, so give it a few days and just keep an eye on it.
Greg

 

Thanks for the responses -- when I checked tire pressure this morning, both left front and rear were within measurement error of yesterday's readings, so if it's slow, it's s-l-o-w... I'll keep watching!

 

For those that have a leaky valve stem--there is a tool that costs like $1 from Autozone that will tighten the valve stem core. Takes a couple of turns to tighten it. Also if you have the tire Slime kit--it comes with a valve stem core remover--the plastic cap--you have to remove the valve so you can fill the tire with slime. You can use that cap to tighten the valve as well.

 

Thanks--

I'll check valve stems (along with tire pressures) tomorrow morning before I head off to the salt mines. And if I find something, I'll let you know!

 

A week later, another low-pressure warning, and damned if I can find anything!

This morning I went by my favorite tire place (Wheel Works) and had them take a look.

They found a small nail in the tire, removed it, and patched the tire.

 

I've had an experience with the tire pressure warning as well. Can someone confirm when is optimum to check pressure and how often? When tires are cold? After driving a bit? How long? I'm driving a '08 MCS.

 

i tend to do it once a week now, in the morning with tires cold, usually after cleaning the windshield.

 

Tire pressures should be checked at least twice a month. For us in the north when the change of seasons come in the fall as the temp drops, once a week is good. Inflation pressures are stated as a cold inflation pressure, less than 1 mile driven or or sitting for 4 hours after a long drive. The engineers know that the pressure will go up as the tire warms and is designed into the overall operation of the vehicle.

 

Maybe someone else can help me out. I decided not to go with the original size tires, ya know the dunlop ones that are tiny...seeing as they cost more because they are rare...lame, But i have an '03 R50 and i am struggling with tire pressure issues. I dont know to put in them exactly because i have 185 65 15. The sticker doesnt list what is needed for that size tire jsut one below and above it, so i took about middle for the other two 175 and 195. wich is i think about 32-33 psi. Well my front is looking kinda low and its been bothering me. I havent had any weird ware and tare. I like decent traction but not drag racing pressure or stiff; a nice medium feel.

help...any one

Thanks

 

I don't know about the R50, but the R53 MC has 33 psi for most situations and 36 psi for fully loaded driving over 100 mph (autobahn I assume). It doesn't matter whether the 175/65-15 through all sizes to 205/40-18.

The R56 MCS only varies from that with 17" and larger wheels.

I think you would be fine at 33 psi, unless there is some other factor that is different on the R50.

 

Hey thanks, i just needed someone else's opinion. I appreciate it. someone else told me i should use 38 PSI...seems kindof much but i guess illl try it and see. But again thanks, and im sure ill stick with my 33 psi for awhile. There shouldnt be anything different in the R50, nothing that will change that at least hahaa again thanks for helping me out

 

I too seem to have a slow leak. ABout every 14 days or so, I get a Pressure warning. Funny thing is that, it is never the same tire that is low. Well I will be having them check it out when I get my break in oil changed next week.

 

38psi is the recommended tire pressure on the door jam of my '08 MINI to go with the 17" Dunlop run-flats. It did seem high to me, too, but she rides fine.

 

Really!?! well then i may have to give it a try just to see what its like. Couldnt really hurt if i just try it out.
Thanks

 

Did anyone read last month's "speaking frankly" in Modern Mini Magazine about tire pressues? Frank (the ex JCW racing guy who wrote the column) said that there should be about a 5 to 6 PSI difference between the front and the rear (i.e. 30 PSI up front and 24 PSI rear for 16" wheels) Obviously the pressure goes up for lower-profile tires.

 

I didn't read the article, but do recognize that selecting a tire pressure can be quite a science problem. Did it mention what conditions that was for? One can reasonably run different pressure combinations depending on desired outcome (performance, cornering response, even tread wear, etc.) and conditions (heavy cargo/passenger combo, inclement weather, etc.).

 

Indeed he was referring to a more performance oriented set up. For the street, there's less science to it than there would be for the track (obviously). If you're on the street, just follow what the door panel says (unless you have aftermarket tires, in which case you ought to know what tire pressures are all about and be able to figure out the best ones).

If you're on the track, the tires heat up more and the pressure goes up. There's a fine line between too high and too low when you're on the track. That discussion is for another thread, however.

What I do on the street: Front: 32 PSI. Back: 29 PSI.