Tyre pressure loss?
 

Just checked my tyre pressures , normally check weekly but been 2-3 weeks .
Normally use 33F/37R , front ok however rear down to 30 PSI

Have checked for nails etc can't see any .

Is there any normal reasons why a rear tyre can loose 7 psi in 3 weeks without tyre damage ?

Cheers Steve

Re: Tyre pressure lose
 

leaking valve possibly?

drop some washing up liquid in the valve and watch for slow bubbles

Re: Tyre pressure lose
 

have you got good o-ring sealed steel or ally valve caps?
in warmer weather the valves can leak a little as they expand and contract, the standard plastic ones just don't cut it IMHO

Re: Tyre pressure lose
 

Caps are the standard plastic ones , will check valve for leak tomorrow and maybe look into getting some decent caps for a couple of quid

Cheers Steve

Re: Tyre pressure lose
 

If pressure's getting out through the valve caps there's a problem with the valve core, possibly just needs tightening or may be ill seating or have crud in it. I'm 99% sure valve caps are just dust caps which is probably why they're usually plastic cheap things.

You could put a little fairy liquid around the bead and base of the valve to check for leaks too. If you do this give the base of the valve a tug from side to side and look for bubbles.

Hope you get it sorted!

Re: Tyre pressure lose
 

After pumping up last night did 50 mile journey , checked this morning pressure not moved :D.
Got some dirty looks by passers by this morning when spitting to check valve for leak ;) , no leak found :D .

Will keep an eye on it , also pushed the boat out by ordering some metal caps for 2.99

Will check pressures more regulary as have got lazy.

Cheers Steveg

Re: Tyre pressure lose
 

temp fluctuation can cause pressure loss - like going into the winter seasons drops the ambient temp and make tyres deflate too

(not the cause here though as its been lovely weather)

Re: Tyre pressure lose
 

My brother had a problem with his Mille that the front tyre would deflate as he was riding it. No punctures found or leaky valve detected.

in the end he narrowed it down to the valve core, it was a cheap/nasty jobby and at high speed would leak but not when stationary.

Re: Tyre pressure lose
 

Check the valve internals are in properly other than that. 3 weeks sounds about right to me to loose 7 psi? Anyone else?

Re: Tyre pressure lose
 

Don't use metal valve caps. They sieze to the valve threads and are generally a pain in the rse.

Plastic caps are fine, and more importantly don't look at all chavvy.

Re: Tyre pressure lose
 

had a simular problem mine was loosing it after riting at speed on the motoway, tyre place tracked it down to caps told me it was down to centalfudrick force (sorry cant spell that) anyway caps was changed problem solved oh by the way had metal ones they changed them to normal plastic ones

Re: Tyre pressure loss?
 

Nah, teriyaki is right. The valve does the sealing not the valve cap. The cap is there to keep cr*p out.

If the valves are faulty just replace them with good ones. Its a bout a 5 minute job in a tyre garage (that includes making a cuppa).

Re: Tyre pressure loss?
 

Took bike to tyre place , they took wheel off and tested in water bath for leaks , no leaks , replaced tyre values . still leaking about 1-2 psi a day ...
Never has this kind of problem with a tyre before
Rear storm has about 4.5k & is about half worn , don't want to replace tyre yet , thinking about trying some ultra seal tyre stuff any one got any ideas ?
cheers

Re: Tyre pressure loss?
 

Did they replace the valve stem too or just the valve core? Leaks around the base of the stem or the tyre bead are also a common cause of slow (undetectable) leaks.

Cheers

Re: Tyre pressure loss?
 

Also, next time the tyre is off, try to get a peek at the rim. The rim might need a thorough clean.
Some tyre fitters (at least in my part of the world) tend to use soap flakes (Lux laundry soap with enough water to make it a mush - they call it elephant c**) which contains a small amount of free caustic. The caustic causes corrosion problems between tyre & bead on ally wheels and ultimately leaks.

Cheers

Re: Tyre pressure loss?
 

Good morning all.

The loss of a couple of PSI per week is normal. Hence checking ones tyre pressures weekly or every 200 miles is a good idea.
Obviously tyres & wheels are made to tolerances, & it is possible to get a wheel/tyre combination where each are at opposite ends of their specified tolerance, then the loss is normally greater.

Another thing is that contributes to pressure loss, is when there's a build up of dried 'gunk' on the inside of the wheel rims, left over from previous tyres. It's not a bad idea when having new tyres fitted, to ask the fitter to give your rims a good brushing to remove the aforementioned 'gunk'.

As said, check your pressures weekly, or every 200 miles.


Cheers.

Re: Tyre pressure loss?
 

Just the valve stem , if valve core was leaking would this not show when totally emerged in water ?
My bike could described as a bit gunky

The rear has been on for 3 months & 4500 K miles and never really lost much pressure on weekly check occasional 1psi , now loses 1-2 psi a day ?

Thanks for the replies

Cheers Steveg

Re: Tyre pressure loss?
 

Hmmm... don't know if we are on the same page
Valve Stem = the bit that goes into the rim and the valve core screws into.
Valve Core = the guts of the valve and screws into the stem.

Anyway... Some leaks (like 1-2psi) can be damned near undetectable, so the answer to your question is "no".

There is an alternative solution, but I am loathe to suggest it... I hate the stuff for the mess that it makes of everything (I change my own tyres) but a small amount of slime (or some similar product) will cure it. FWIW, I reckon this type of leak is the best use for such products.

Cheers

Re: Tyre pressure loss?
 

Hi ,

It was the valve core that was replaced , will see how it goes as I do a fair amount of miles , tyre should be replaced with another couple of months so might live with it , if not drop some ultra seal it it.

thanks for the replies

Cheers Steve

Re: Tyre pressure loss?
 

if you suspect the valve is at fault get yourself some washing up liquid plastered around and in it. If you have a pump inflate the tyre higher than normal, say 40/45 psi and watch.

If you have a leak, even slight then it should show up over the course of a cuppa. Otherwise I think its SpannerMans suggestion of crap around the rim where the tyre is mounted. Only way to resolve that is to remove, clean and remount it.

I wouldnt go squirting any ultra seal around unless its an emergency get you home or you'll end up with a worse mess to clean up.

Re: Tyre pressure loss?
 

I don't agree with this statement. The current tyres on my 03 thou are holding a steady 36psi for months on end. I hardly ever have to pump up the tyres on my car either.

There is a leak somewhere, albeit a slow one.

Puncture
Leaking valve core
Leaking valve
Leak between tyre and rim
Porous rim

Re: Tyre pressure loss?
 

Well you must be the lucky one then :D Or perhaps I should have been more specific & said 'could be considered normal'
After all why does one think that manufacturers specify that you should check your tyre pressures weekly, or every 200 miles?....Cue for some 'handbag flinging':D

Check 'em weekly folks we can't all be as lucky as Rocket!:D


Cheers.

Re: Tyre pressure loss?
 

Mine hardly ever lose more than a PSi or so here and there (atmospheric changes probably) but I always check them before every ride! That one time I don't check may be the time I ride off with damage picked up from the last ride that's already dropped the pressure to half the recommended...

Re: Tyre pressure loss?
 

We used to always lose pressure, both on the SV and then on the Duke............until we used a different tyre fitter. Now we can go weeks with no loss of pressure. What the new fitter is doing different to the old one, I don't know, but the difference is very apparent.

Re: Tyre pressure loss?
 

Soap or new valve cores maybe.

Re: Tyre pressure loss?
 

Perhaps he is a little nicer to the bead area... I am no tyre fitter but I get to fit and balance all of my own bike, car, truck tyres (less of the latter two) and learned the hard way that reasonable care needs to be taken with the beads.

Re: Tyre pressure loss?
 

Totally agree MattCo. Fitting tyres is one of things that only needs doing once if you do it properly. If the rims are cleaned properly and the tyre is soaped before fitting you should get a pretty good seal on a straight rim.

I fit all my own race tyres, the only issue I've ever had with pressure loss has been a faulty valve core once.