Wheels with tyre pressure monitors

[Sloppysod]

The pressure drops in my rear tyre by about 0.5 bar over about 250 miles or a couple of weeks enough to show message "tyre deflated".
I changed the valve, and that did not solve the problem, therefore it must be a puncture. Now the tyre is about half worn so should be okay to repair.
My questions are, is there anything I should be aware of when taking it to my tyre shop for repair and/or will it do any harm filling it with tyre gunk?
Thanks
Stu

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[Hell Razor5543]

I would not use the gunk, as (according to what I have read) it can be awkward to clean out the tyre and rim of the stuff, and I would not like to know what it does to the TPM valve.

[GiveMeABreak]

Well not too sure if by 'gunk' you mean that tyre weld stuff Stu? - If so, as the TPMS sensor is attached onto the inner rim - and obviously monitors the pressure of the air within the tyre, I suppose it depends on whether there is an apperture within the sensor where the air pressure is forced into therefore where the gunk could get into, or whether the sensor has a sealed membrane that measures the pressure that way. Hard to say unless there's a TPMS guru here!

I currently have a similar issue on my front right tyre - slowly losing pressure to get the deflated warning. When I had it in the garage for the suspension pipe work today, they were going to replace the valve with the repair kit for me - but when they tried to take it off the valve itself was stuck. They didn't want to force it as they felt is would snap for sure, necessitating a new TPMS (all 4 are only 12 months old!). So they have put some penetrating oil on it and told me to pop down in a few weeks, where it should be easier to take off. I have 2 new tyres on the front and I was damn well hoping it wasn't a puncture - but they tested it when in the workshop and no leak from the tyre or the beading - so is going to be the internal valve.

[wheeler]

Not a fan of any of the 'gunk' type sealants but the Slime brand is safe for use on cars with TPMS valves & is also completely water soluble so washes off no problem, many tyre fitters however will tell you the tyre is scrap once you put it in.

[Sloppysod]

Thanks guys,
Marc yes I did mean "tyre sealant", I relised my erorr about 10 minutes after poasted the question that it may cause confusion, but was in no positon to edit it.
I will see if I can find the hole first -(pump the tyre upto about 50 psi and dunk it in the bath, when SWMBO is out shopping - of course!!). if I can find it I will possibly get it repaired, if I can not I will probably use the stuff wheeler mentioned, I like the fact that it can be removed easlily.

[daviemck2006]

My last slow "puncture" was the tyre leaking around d the rim. Tyre had to be removed and faces of the wheel and tyre cleaned then refitted. I don't know it the "gunk" would fix that. Would the centrefugal force of the wheel turning throw all the "gunk" around the back of the tread?

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[GiveMeABreak]

I think it is pretty much like that expanding foam you get from the builders merchants to fill in large gaps or holes. That's usually why the tyre is pretty much KO after use as is only meant to seal the puncture until you can get it replaced. As Wheeler says though, the water soluble one would be the better choice if you had to use it.

I've heard of people using this stuff in Run Flats! Which pretty much defeats the purpose of the design in the first place. Gunk not recommended at all for Run Flats.

[elma]

many tyre fitters however will tell you the tyre is scrap once you put it in.

This is a big issue with gunk/slime. Unless you know a tyre fitter well they are unlikely to repair a filled tyre weather it is water based or not.

[Sloppysod]

Hi All,
I decided to get a new tyre (+1) to sort out another issue I had, but thanks for your responses.
However, I was shocked at the price, according to my Tyre man 17" X7 tyres are 'specials' hence the price of £133 each!! (Michelin Primacy 3's), I was expecting just under £200 the pair ouch!!!!

[GiveMeABreak]

Could of got Falken, Kumho, Hankook tyres for about £70 each delivered.... in my experience the Premium tyres are no better than a mid range and last just as long. , but then that's another topic entirely!

[Mandrake]

On my Xantia I had a fast leak on one rear tyre that started a few months ago - no sign of a puncture that I could see, it would lose about 10psi per week so basically needed topping up weekly at least, even though the car is hardly driven.

One of the fronts was losing about 2 psi a week and the other two were OK. The tyres were all old and motley so not unexpected.

New tyres and valves all round - no more leaks. Checked them after a week and all four are bang on what I set them to. It might have been the valves but my suspicion is they start to leak around the rim.

[GiveMeABreak]

Update: The one front tyre that I recently had the punctured warning for continuously, despite being over then under-inflated, then back to normal pressure was eventually solved by getting it re-pregrammed at the dealer - however, soon after leaving, it happened again - but this time front left. So back into the workshop and the solution was that one sensor couldn't be programmed in isolation - they had to do the 4 at the same time. Problem now sorted. The Service Manager stated that the TPMS units have a tolerence of pressure variation - if they are inflated above this, it throws the programming off and needs to be reset (or all 4 need to be reset as in this case). I had suspected a slow leak - but the pressures were always correct - now we know why.

So lesson here is don't over-inflate your tyres by too much - as it can cause the TPMS sensors to need reprogramming.

[Paul-R]

What is "too much"? I upped the rears to the high speed / heavy weight value prior to setting off on holiday. How much tolerance is there I wonder?

[GiveMeABreak]

He just said there was a tolerance - so would assume it would have to be well above the recommended fully loaded pressures on the vehicle pillar label. I suspected I had a faulty sensor as I knew the tyre was holding pressure - it was me that over-inflated then under-inflated the tyre before pressurising it back to the recommended in order to try and get it to stabilise - but didn't work. The sensor was tested as fine - knowing that all 4 of these were brand new 2 years ago when I had them all replaced with the newer type after the whole thing shot out from one of the tyres! It may of been the tyre fitters over-inflating one of then by too much when I had the new Cross-Climates fitted last winter - come to think of it that's about when I noticed the problem - has been intermittent until getting them all re-programmed last week. All fine now!

[Mandrake]

A tyre pressure sensor that can't function properly if it has been temporarily subject to "excessive" pressure, until it is reprogrammed ?

Does the phrase "defective by design" seem fitting ?