All 4 tyres of my car seem to be losing pressure slowly. Why?

Every few months I get the warning light to check my tyre pressures. So today, after getting the warning again, I decided to record the current pressure of each tyre so I could confirm which one it was. However when it came to adding air to them all of them where several (5-7) psi off where they should be and none dramatically worse than the others.

I doubt I have a slow puncture on every single tyre. They're not even that old. The tread is fine on them all. The car passed a full MOT and Service back in July.

Any ideas?

[raging bull]

Have you alloy wheels?
Leakage from the rims.

[heero_yuy]

^^

Seconded. Leakage from the rims. Cure is to have the tyres removed and the rims cleaned up. Your local tyre specialist can advise.

Mmmm cheers. I'll take it to a tyre shop and see what they say.

[Taf]

Originally Posted by raging bull

Have you alloy wheels?
Leakage from the rims.

Thirded. I had all 4 alloy wheels stripped and recoated locally for under £200 last year. I've checked the pressures weekly and have not had to reinflate them at all since then.

[Hom3r]

Another option is to fill with nitrogen, the molecules are thicker the O2 ones, leak less

People at work fill their tyres with nitrogen.

The joys of filling plane tyres.

[peanut]

You could lose a bit of weight to balance it out.

Originally Posted by peanut

You could lose a bit of weight to balance it out.

Or put more on.

---------- Post added at 19:11 ---------- Previous post was at 19:11 ----------

Originally Posted by Taf

Thirded. I had all 4 alloy wheels stripped and recoated locally for under £200 last year. I've checked the pressures weekly and have not had to reinflate them at all since then.

Why would all 4 be dodgy though?

[Hom3r]

Originally Posted by Damien

Why would all 4 be dodgy though?

How old is the car?

Alloys do corrode especially if you clip the curb, stone chips etc.

Another thing could be valves are knackered.

[Taf]

Originally Posted by Damien

Or put more on.

---------- Post added at 19:11 ---------- Previous post was at 19:11 ----------



Why would all 4 be dodgy though?

1995 car, corrosion on all 4 rims where some daft pi11ock used knock-on balancing weights instead of stick-ons before I bought the car in 2000.

The valves were all changed (as per the norm I think) when the tyres were changed.

---------- Post added at 20:05 ---------- Previous post was at 20:03 ----------

My old Lada wheels drove mechanics to distraction as they just kept on slowly deflating. Then they found out why: the wheels were made of 2 castings joined back-to-back, with a thin rubber gasket between them. And Russian rubber doesn't last long.

[Ramrod]

Originally Posted by Taf

My old Lada wheels drove mechanics to distraction as they just kept on slowly deflating. Then they found out why: the wheels were made of 2 castings joined back-to-back, with a thin rubber gasket between them. And Russian rubber doesn't last long.

That figures

[idi banashapan]

Originally Posted by Damien

Why would all 4 be dodgy though?

Car was used as the getaway vehicle and ran over a stinger

[Mr K]

I had the alloy coroision / tyre pressure issue with an old car. Kept gradually reoccurring even though I kept getting it sorted at the garage.

[Taf]

Many tyre fitters will try applying a black, gooey gunk to the rims before refitting tyres. Sometimes it works, often it doesn't.

[heero_yuy]

Most alloy wheels, even silver ones, have a painted finish. Problems start when that paint is chipped, such as kerbing the rim or using clip-on weights. Corrosion then sneaks in under the paint often forming a path to the inside to allow a slow air leak.

Whilst a clean up of the tyre bead seating area and some goo will often provide a short term solution, the only real answer is to have the rims stripped, cleaned and re-painted.