Loss of Tyre Pressure?

[magycks]

Hi All,

Recently got 4 new tyres on my MY14 DB9. One of the tyres appears to have a slow loss of pressure even though the car has hardly been driven and has no obvious puncture (tyres were changed right before the social distancing rules so all i've done is a handful of miles to the supermarket and back). It's worth pointing out i thought I had a 'slow burn' puncture with the previous tyre on the very same wheel (but it was pretty much on the wear indicators so I just replaced it rather than going down the repair route)

Some initial reading points towards a valve in the TPMS (tyre pressure monitring sensor). Any thoughts?

[Speculatore]

magycks said:

Hi All,

Recently got 4 new tyres on my MY14 DB9. One of the tyres appears to have a slow loss of pressure even though the car has hardly been driven and has no obvious puncture (tyres were changed right before the social distancing rules so all i've done is a handful of miles to the supermarket and back). It's worth pointing out i thought I had a 'slow burn' puncture with the previous tyre on the very same wheel (but it was pretty much on the wear indicators so I just replaced it rather than going down the repair route)

Some initial reading points towards a valve in the TPMS (tyre pressure monitring sensor). Any thoughts?

The wheel could need refurbishing as they sometimes cause a poor seal due to age and deterioration with the alloy.

[rog007]

Had this in my last XC90 after new tyres were fitted; they hadn’t replaced the valves and one was leaking. New valves sorted it. I usually have new valves every time I ever have new tyres; I’m sure I asked and was billed for them, but they clearly forgot...

[magycks]

rog007 said:

Had this in my last XC90 after new tyres were fitted; they hadn’t replaced the valves and one was leaking. New valves sorted it. I usually have new valves every time I ever have new tyres; I’m sure I asked and was billed for them, but they clearly forgot...

My invoice states "4x Rubber Car Valve - Normal" @£0 so perhaps this is something they 'forgot'. Would make sense given the outgoing tyre had the same issue (i just topped it up at the petrol station once a week as knew all 4 tyres were due replacement anyway)

[Graze01]

I'd be surprised if this was the case but the wheel could be porous - I have a mini lite copy wheel on my TR4 which is and the tyres loses about 1psi per day

Take the wheel off and get your tyre shop to immerse it in water and you will soon know where the leak is from

Graeme

[the tribester]

Take the wheel off, pump it up, leave the valve cap off, slosh some water with washing up liquid mixed in, around the valve and bead and lookout for tiny bubbles.

[4x4sche]

There is an insert inside what people call "the valve" that is the actual valve. This can easily be tested. Take off the cap. Place a bubble of spit across the face of the valve and watch for it to get bigger. If if does the Schrader insert is leaking. Get a valve tool to remove this (needle nose pliers will work) and replace it.

[4x4sche]

Further to my prior comment.... before changing the insert... jack up the car so the weight of the car on the deflated tyre does not cause the tire to separate from the rim. Reinflate the tyre.

[8Tech]

Many tyre fitters are very cautious when touching tyre pressure sensors so they may have either not replaced the insert or, not tightened it correctly. The invoice is probably a simple "template" used for all fitting and they simply put the tyre cost in the template.

However, the most likely cause is a leak on the bead seal and any tyre fitting business should check and rectify this FOC considering you purchased the tyres from them.

There is a black sticky gel type rubber sealant they can apply between the tyre and rim should you not wish to go to the expense of having the wheels refurbished.

Let it dry, and then simply peel off any excess once dry. Its a regular problem on my old 20 year old BMW with lacquer peeling alloys that simply are not worth refurbishing.