Tyre Pressure Drop

[2Rack]

Hi

My first post and a really 'strange' one -- I hope you can help.

On all the tyres on my 2002 T Sport the pressure keep dropping by 2 or 3 PSI, over about a week, from 30 to 27 ish and then stay there -- so not a slow puncher. They are the original alloy rims with 4 year old Toyos fitted, only do about 5000 a year and still decent tread on them.

I've had new valves fitted and the white gunk slapped around where the bead fits but it still happens. A real pain having to go the the air pump everytime I fill up - now often 50p or a quid a time ( money for old air!!!)

Anyone else had/seen this and found a cure?

Cheers

[Rayburn]

Quote “from 30 to 27 ish and then stay there”

Well 2Rack,

If I were you....

I would get a new Digital tyre gauge (eBay £5-6) and check them myself.

Next fill the bath with water and place wheel in bath.

Look for air bubbles these will be (may be)very small. May then need tyres re-sealing on the rims, or you might have a leaky rim.

Start off first with correct pressures apprx 32psi? Your handbook should tell you.

Let us know how you get on.

R

[Madasafish]

If your tyres are 4 years old, the rim which seals may be growing hard and leaking.

Or the wheels may have corrosion.. or the valve seats may be damaged.

I would have thought any semi competent wheel and tyre place could do the investigation and find it for you.. Resealing grotty wheels/hardening tyres is not going to work.

I find it hard to believe all four tyres are affected though - which perhaps suggests the people who last took the tyres off perhaps ruined them.

[stantheman1]

Over time the inner faces where the tyre seals on alloy rims become pitted due to corrosion caused by condesation (when the wheel becomes hot then cools down again). The only permanant solution I'm afraid would be to remove the corrosion by sanding down the area then reseal using suitable paints/fillers.This can be done at the next tyre change by the fitters but often they don't spend enough time on prepping the surface due to time constraints.

[avensis57tr]

You may find its the fall in temperatures if you checked them last week when it was 12 -15 degrees then checked them today when it was 3 - 6 degrees that will make a big difference. Topped up the tyres on Fabia and Yaris this morning when it was cold and both were down several psi and they had been spot on when checked last sat so 3-4 psi on all tyres in space of 5 day defo temperature related.

[Cyker]

Yeah, I was about to post that too

The temps have dropped quite a lot recently and I too have had to give the tyre pressures a boost.

I normally run 38F/35B but they were at 33F/30B when I checked them last Saturday morning.

The fact that they dropped, but stopped dropping, is a good indication; Usually if it's a leak, it will continue to drop...

[2Rack]

Hi

Thanks for replies - the readings were taken from my own digital guage so at least were consistant

I haven't thought about the air temp, certainly not several psi change. always tried to inflate them as soon after starting out as possible but will check again over this week now its a cold autumn.

Then I'll have to find a decent tyre fitter and get the tyres off and look at the bead seal area and the bead themselves. Last time explained the problem to the fitter who changed the valves, and they just got on with it, didn't show me the wheels or say there was corrosion, and took the money!!! -- that also took two trips as they'd not replaced one valve the first time!!!

If its corrosion causing a poor seal, which goes away as the tyres sags on to the rims, will the alloy need re-painting after cleaning? Do general alloy wheel refurbishers do that sort of work? or very specialist people? Any recommendations in Wiltshire?

Hopefully its either corrosion or knacker tyres and not both, that'd would be a big ouch

Cheers