machina

Just out in the garage reinstalling my FVD mufflers after trying the muffler bypass pipes (will post in another thread)

So went for test drive and TPMS warning came on for left front wheel. Actually watched the pressure dropping like a countdown but got home around 16 lbs.

Jacked her up but no punctures so i checked the TPMS sensor valve stem and damn if it wasnt loose and leaking air.

I was able to tighten the outside nut and it seems fine now. The sensors have never been out of the wheel so i guess it just worked loose.

So go out there guys and check your valve stems.

LlBr

Thank you for the heads up. That's something you'd never think to check.

Don't want to create unnecessary concern, but I can't leave this unasked: are you sure you didn't create invisible damage to your tire? These tires are serious 100mph+ items with narrow sidewalls.

russo

Gotta love TPMS, it gave enough warning to get you home.

KeninBlaine

I'm surprised the stems don't loosen more often. They aren't supposed to be over-tightened, and there is no lock-nut arrangement, so there is no reason why they can't slowly loosen IMO. Good idea to check them regularly, especially those of us who don't have TPMS.

Edgy01

Suspect your tire shop!

machina

Right, but if i didnt have the TPMS stems, wouldnt have had the problem in the first place.

I love having it though. I am a tire pressure monitoring weenie now. I always have the psi readout on the dash. And its really useful at the track. Good way to measure tire psi changes when the tires get hot.

rijowysock

its the tire shop, their is a certain tq on the sensor bolt and a certain tq for the nut on the front of the stem... do those and shouldnt ever have a problem... mine are fine in both sets of wheels.

Steven B

Interesting post. Does anybody know the torque numbers of the nuts?

machina

i remember seeing the torque setting listed right on the sensor itself in Nm units.

If anyone has a sensor thats not mounted maybe they can check it out.

cviles

Just remember to consider instrumentation failures as well.

My TPMS was screaming at me a week ago that my right rear tire was flat. The tire was fine, only a pound or two low. So double check with a tire gauge. Like anything else that has a computer involved, sometimes they glitch.

machina

That was my first thought but the stem was so loose you could turn it by hand and when it wiggled you could hear the air escaping.

LlBr

Find the tire guy who was responsible and punch his face? Nah. Definitely let him know he messed you up though.

machina

Found the torque setting.

4 Nm
2.95 ft lb
35.4 in lb

Dont use your big torque wrench for your wheel lugs, not accurate enough at only 3 ft lbs. You need a smaller torque wrench calibrated in (in lbs.)

19_hole

I trust that you mean 2.95 lb-ft and 35.4 lb-in........