Inyoury

Hi all. I have 20" wheels and Pirelli P zero Summers on my car. I have noticed that the tire pressure on all four tires have gone down a lot lower than I would like. I set the fronts 39 psi and the rear 37 psi. But after a few days of driving around, I noticed that they lose some air pressure and go back down to 33 front and 34 rear. It has happened more recently (the past 1000 miles). I have kept refilling the tires, but keeps happening a few days later. I haven't noticed the pressure to drop below the 33 and 34 psi. Has this happened to anyone?
Thanks

KevinGary

When you filled them up were the tires hot? When you measured them later were they cold?

Inyoury

I tried them cold and hot. I followed the tirerack tire pressure guide. All the same results

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=147

superswiss

I would say your tires leak somewhere. It's quite a coincidence that all four tires leak, but get them checked. Have them check if your wheels are bent. Did you drive over something? Maybe they were just improperly mounted.

Barrels41

Try several pressure gauges.

tenspeed

I've heard of porous tires, porous rims, bead and valve stem leaks. The only thing that should be changing and is common to all four tires is the ambient temperature.

Make up a soapy solution in a spray bottle, spray the valve stem and beads and look for bubbles.

snagitseven

The other thing that could be common to multiple tire air loss is bent rims. I had my A6 in for my 35k service and to check my wheels. I was experiencing some hi speed vibrations so expected at least one bent wheel when placed on the machine. They confirmed three bent rims.

I decided to order new tires, they straightened my wheels and mounted and balanced my Tire Rack Conti DWS 06 - all is good again.

Point of the story is it's possible to have multiple bent rims which could result in some air loss.

Inyoury

I checked the wheels to see if the wheels were bent, but I couldn't notice anything (but the dealer would be able to know better. I don't think there is a leak since the pressure doesn't seem to go below what I mentioned even after over night. Also I don't think I hit any unusually large bump or pot holes. Just wanted to check on the forum to see if anyone had the same issues.
Just need to make another trip to the dealers...

snagitseven

Most bent or out of round rims cannot be detected by eye. They need to be placed on a wheel balancer. Sometimes even then, it won't show up until checked on a Hunter machine.

335i

U might have some cracks or bends. Bends dont usually leak air that much but cracks do what you are describing. Are they replica wheels do you live in a area with poor roads?