Why are my tyres randomly deflating?

[All that jazz]

I changed the 15s on my Golf for some 16s end of December. The fitter commented that they had quite a bit of corrosion on them, on all sides including the bead area and it might take him a few attempts to get the bead the seal. That was indeed the case and one of the wheels took 3 attempts til it wouldn't leak. He also mentioned that I may have to come back to have them done again as more leaks can show up once the cars weight is on them.

So 3 weeks went by and I didn't have any bother with them at all. I checked the tyre pressures on a regular basis and they were all holding their pressure just fine and then one day one of them had deflated overnight to about 5 psi. Pumped it up again and it was fine for another 10 days then randomly deflated itself overnight to nothing. Pumped it up and it's been fine since, but now today I go out to use the car and one of the other tyres is completely deflated . Done about 80 miles on it today and checked the pressure again and it's holding okay.

Can anyone clued up on such matters tell me what the actual fk is going on and why please. Surely if I have leaky tyres then they would be deflated on a daily basis, not be fine for 3 weeks then deflate, then be fine for another 2 weeks? I did initially think that there was some tomfoolery going on but other than some foxes and cats there is nothing of interest on my motion sensor cam recordings.

[TheHeretic]

Someone is messing with you.

[randlemarcus]

Alloys or steels?

Might be porous alloys, or a slightly out of true wheel, that mostly seals, but sometimes doesn't, when the leaky bit is, for example, at the bottom.

I had one porous alloy that is now serving as a hose reel.

[andy-xr]

Had this with stty valves, got them revalved and they were fine

[All that jazz]

randlemarcus said:

Alloys or steels?

Might be porous alloys, or a slightly out of true wheel, that mostly seals, but sometimes doesn't, when the leaky bit is, for example, at the bottom.

I had one porous alloy that is now serving as a hose reel.

Alloys. But how can you have a "bottom" of a wheel??

@ Andy, the valves were buggered on all 4 wheels when I had them fitted and he replaced them all with new ones. I saw the bubble test for each and they were all fine after putting new valves in.

[themanwithnoname]

All that jazz said:

Alloys. But how can you have a "bottom" of a wheel??

@ Andy, the valves were buggered on all 4 wheels when I had them fitted and he replaced them all with new ones. I saw the bubble test for each and they were all fine after putting new valves in.

Tyres always go flat on the bottom of the wheel fella. Just one of those things that is completely unexplainable.

[TheHeretic]

themanwithnoname said:

Tyres always go flat on the bottom of the wheel fella. Just one of those things that is completely unexplainable.

Whenever I get a flat I just jack up the wheel, turn it 180 degrees, and continue on my journey.

Edited by TheHeretic on Saturday 9th February 18:53

[Spangles]

I'm guessing but perhaps when the pressure is on the tyre at a certain point on the rim it leaks? Next time it goes flat mark which bit of the rim is nearest the floor and don't park like that again.

[E30M3SE]

All that jazz said:

I changed the 15s on my Golf for some 16s end of December. The fitter commented that they had quite a bit of corrosion on them, on all sides including the bead area and it might take him a few attempts to get the bead the seal. That was indeed the case and one of the wheels took 3 attempts til it wouldn't leak. He also mentioned that I may have to come back to have them done again as more leaks can show up once the cars weight is on them.

There's your problem, either get the wheels fully refurb'd or get the tyres removed, wire brush the bead area and the get them bead sealed.

[Dominicc01]

Pretty simple really. The corrosion on your alloys is only in patches (or a single patch) around the inner rim. A parked car will exert more pressure on the bottom of the tyre, and slightly distend the sidewall at the bottom, and so if the damaged part of the alloy is at a particular place at the bottom where more pressure is being exerted and the sidewall is distended, air can escape. If the corrosion is at the top, all will be well and the tyre will not lose pressure.

HTH.

[lewisf182]

OP my bora is sxactly the same, had 15" steelies and switched to 16" montreal 2's... One of them is fine then after a certain amount of time it just goes suddenly flat over night! Not sure what it is, just pump it back up!

[A.J.M]

I changed my tyres 2 weeks ago, the fitter said all alloys had corrosion on the insides and the front left has a flat spot on it, but it's balanced out.
Checked the pressures yesterday, the front left was at 19 psi and the rest were at 38 psi.

Maybe you have something similar? Flat spot not getting a proper seal on the tyre.
I'm getting the fitter back out on tuesday to check the wheel and tyre to see what can be done.

Could be worth a try?

[mad4amanda]

E30M3SE said:

All that jazz said:

I changed the 15s on my Golf for some 16s end of December. The fitter commented that they had quite a bit of corrosion on them, on all sides including the bead area and it might take him a few attempts to get the bead the seal. That was indeed the case and one of the wheels took 3 attempts til it wouldn't leak. He also mentioned that I may have to come back to have them done again as more leaks can show up once the cars weight is on them.

There's your problem, either get the wheels fully refurb'd or get the tyres removed, wire brush the bead area and the get them bead sealed.

Fitter should have cleaned them up on the bead seal area before fitting tyres really that or told you to take them away and do it and bring them back a good wire brushing or a brush on a drill will do it , you can as others have said get a bead sealant too gorilla snot we used to call it as its black and sticky!
Also as someone else said valves should be replaced as a matter of course its false economy not too every time.

[E30M3SE]

He should have done, but did he?

[All that jazz]

He did indeed. He gave them a really good wire brushing in fact and gave them a good cleaning afterwards to remove the residue.

I didn't realise that there was more weight at the bottom. Well I did, but didn't like to mention it in case of ridicule here . I'd kinda assumed that the weight balanced itself out evenly as air pressure within the tyre so that no area of the wheel or tyre was under more "weight" than another, but I'm no expert in such matters. I do get the bit about the tyre obviously flexing where it contacts the road and air being able to leak from there though - I guess that's what is probably happening then?

@ Lewis, these are Montreal 2s as well!

[themanwithnoname]

TheHeretic said:

themanwithnoname said:

Tyres always go flat on the bottom of the wheel fella. Just one of those things that is completely unexplainable.

Whenever I get a flat I just jack up the wheel, turn it 180 degrees, and continue on my journey.

Edited by TheHeretic on Saturday 9th February 18:53

[fastcars_hardy]

i had this. there was a small crack in the alloy and when sat on the crack it would leak

[TheHeretic]

fastcars_hardy said:

i had this. there was a small crack in the alloy and when sat on the crack it would leak

I've leaked out of my crack when I've sat on it before.

[fastcars_hardy]

TheHeretic said:

I've leaked out of my crack when I've sat on it before.

i ment when the crack was at the bottom it would leak. good spot tho