bohaiboy

My regular mechanic said my valve stem is leaking on my doughnut spare. My tire guy says it needs a special valve stem. I didn't think the spare had a TPMS system in them? Is he just mistaken? I know the four regular tires do. 2010 S 550, 134k

DaleB

BOTUS

UK cars don't get a fifth TPMS sensor, its just a normal stem even if you get a full size wheel

the risk with a fifth sensor is the car will pick up the wrong one.... and anyway the car only understands 4 unique codes (it doesn't care which is on which location), but its only coded to see the 4 its got, so unless you duplicate one of the car's other 4 sensors it would do nothing and then if a different one had a puncture it will be running the same code in two places and throw its teddies anyway

not sure how they handle winter tyres.... on BM you can have set a and set b

dlafever

This is the one. Also known as TR438. It's a special smaller diameter valve stem made just for space-saver spares.

lkchris

The valve stem for the donut spare wheel is indeed a unique item ... obtain from Mercedes dealer.

This is an item that’s a good idea to have on hand “just in case.”

Popo Here

When I replaced my factory wheels on MY2013 S550, I took the cargo tray off the trunk and put the full size factory wheel as a spare. It has tpms and I've never had any problems with reading the sensors. That was in 2013 and it's still in the trunk

BOTUS

its dependant upon what wakes it up

my bike wakes up by spinning (above 30mph) although a later one any large shock would wake it. So if its remains asleep all good. but how does the car know its unique Bluetooth code.... my car has 4 sensors coded to the vehicle each one has an independent code (and displays the pressure at each location on the cluster (TMPS high line)