Why are the tyres deflating?

[TVR MAN]

My Mum's tyres keep deflating on her '05 mk2.5 sport. They seem to hold pressure for a random amount of time before going completely flat. Also it seems to happen to all the wheels on a random basis.

We did consider vandals but thought this is unlikely given where we live.
I suppose it's possible all 4 tyres have punctures.

The wheels have bubbling on them but mostly around the centre. Is it possible this is causing the wheel not to seal to the tyre?

Any other possibilities?

[gforceg]

I'll be interested to hear the answer to this one too TVR MAN. Our Sport (so, same wheels as yours) has one that seems to lose pressure. It doesn't look damaged and the loss seems too slow to be a proper puncture.

G.

[vrsmxtb]

Unusual it happens to all four wheels. I'd start with getting the valves checked out, they might be leaking - have you had new tyres or new valves recently? I had a slow air leak after a tyre change and took it back, and it was a leaky valve which they fixed for free.

Only other real possibility is indeed corroded alloys, doesn't necessarily have to be visible/obvious for it to affect the seal round the tyre.

I'd take to a decent tyre fitter, explain the rpoblem and get them to re-seat the tyres, inspect the wheels as they do it and fit new valves and see what happens.

[Mr MXT]

Could someone (kids) be letting the tyres down?

[Munter]

Alloys. Ours corroded and it went from one going down, to all 4 in about a 6 month period. Tyre place sprayed a soapy solution around the wheel and you could see air bubbles slowly forming between the tyre and rim. Worse on the 1st one that started to go. Had the wheels refurbed and problem went away.

(Obviously could have been valves, but I can't see the tyre place waving me away saying it's a wheel problem if they thought they could make a few quid fitting new valves.)

[matts4]

Had this with my wheels until I replaced all the tyres.
A new seal on the rim has sorted the problem.

Cheers
Matt

[Eighteeteewhy]

Take it to a local tyre fitters, they usually have a big water tank that will hopefully solve the problem.

[GBDG]

I have the same problem, thanks for the tips

[TVR MAN]

Eighteeteewhy said:

Take it to a local tyre fitters, they usually have a big water tank that will hopefully solve the problem.

This seems like a good and cheap idea to begin with.

Hopefully it'll be the valves but I doubt it...

[DVandrews]

A friend of mine runs a tyre centre and my daughter had the same problem on her Mk2.5. He said it is a very common problem with leakage around the rim on MX5s, he used a rubberised solution around the inside rim of the wheesl before reseating the tyres, this fixed the problem on 3 of the 4 wheels, the 4th one required some hand rubbing down inside the rim where the bead of the tyre sits, now they are all leak free.

Dave

[dg45]

It's most likely corrosion/paint coming off inside the rim where the tyre sits ,tyres heating and cooling create moisture inside the tyre and eventual corrosion , had same problems myself , some not all tyre places have a wire brush on a grinder and clean this area up then use a different sealing soap to get a better seal , won't last forever though as the area will furr up with corrosion again eventualy , the only long time fix is to have the wheels re-furbished and painted .
Changed my tyres from old set of alloys that I was having re sealed every six months to a new set of wheels and have had no pressure drop since .

[car crazy]

TVR MAN said:

My Mum's tyres keep deflating on her '05 mk2.5 sport. They seem to hold pressure for a random amount of time before going completely flat. Also it seems to happen to all the wheels on a random basis.

We did consider vandals but thought this is unlikely given where we live.
I suppose it's possible all 4 tyres have punctures.

The wheels have bubbling on them but mostly around the centre. Is it possible this is causing the wheel not to seal to the tyre?

Any other possibilities?

I had this on one of the tyres on my old astra, turned out that it hadn't been sealed properly, took it back and they put some of that white paste on it and refitted it for free