Tyre pressure loss?

[steveg]

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

[flymo]

leaking valve possibly?

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

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

[steveg]

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

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!

[steveg]

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

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

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)

[timwilky]

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.

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

[yorkie_chris]

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.