Tyres reluctant to inflate

[Ham]

(Posted this originally inside a thread by mistake!)

Help! - Got delivery of me new bike (Giant SCR 2008) t'other day and am having a problem with air pressure. The rear was already half inflated and assembled - the rear wheel I put on and pumped up - problem is (using a normal pump AND a cycleair pump) they dont seem to want to inflate above half/ 2/3rds pressure i.e. put a bit a weight on 'em and they are flat! - Is it dodgy valves?, (on both!) - any ideas?

 

[walker]

Have You Unscrewed The Valve Limiter?

 

[Mortiroloboy]

Have you got a track pump? if not get down to Lidl next week they are doing one for a fiver, or pop along to your LBS (support your LBS) and buy one there. Track pumps are the best way to get the correct amount of air into tyres, as Walker points out check that the valve limiters (the screwey in bits at the top of the valve) are fully open when inflating, and screwed down tight when your done, other than thay cannot really see what your problem will be, unlikely (I'd have thought) that you would have got two dodgy valves on a bike out of the shop!

 

[PatrickPending]

Have You Unscrewed The Valve Limiter?

for some pictures see here:-


http://www.sheldonbrown.com/gloss_p.html#presta


if they are open just push the middle bit in a bit to let a tiny bit of air out - this just makes sure the valve is free and not stuck

 

[pbar]

Have You Unscrewed The Valve Limiter?

It would most likely be a Schrader valve won't it? These don't have limiters do they?

 

[domtyler]

It would most likely be a Schrader valve won't it? These don't have limiters do they?

Schrader valves are found on low pressure tubes like in car tyres and maybe mountain bikes, certainly not high pressure road bike tubes.

 

[CopperBrompton]

In the UK at least, almost all the bike valves I've seen are Schraders - road, mountain, trike, whatever.

 

[Tynan]

got presta

 

[threefingerjoe]

Use of Presta valves has nothing to do with the pressure. The Presta valve can be accomodated by a narrower rim. Schrader valves are used in heavy truck tyres (120 psi in some cases) and also in air conditioning systems which can reach much higher pressures than bike tyres.

 

[pbar]

In the UK at least, almost all the bike valves I've seen are Schraders - road, mountain, trike, whatever.

Yes, that's what I thought, but started to doubt it after seeing the last couple of posts.
I've never seen anything other than the Schrader ones.

 

[domtyler]

I stand corrected

Presta vs. Schrader

Presta and Schrader valves are equally good at sealing in high pressures. Their chief differences are their outside dimensions, internal resistance to inflation and their reliability at sealing under low pressures.

Schrader valves used for bicycle tires have a greater diameter than Presta valves and the larger diameter hole required for a Schrader valve will weaken a narrow wheel rim. For this reason, Schrader valves are not used in the narrow wheel rims of racing bicycles. Another disadvantage of the Schrader valve is that, when inflating a tire, the pump has to overcome the internal resistance of the spring-loaded valve seal as well as the tire pressure. With racing bicycles using high pressure, added inflation resistance is especially undesirable. The Presta valve gives minimum resistance to inflation as it relies solely on internal air pressure—not a spring—to keep it shut (although it can be manually tightened after inflation). The advantage of the Schrader valve's spring is that, although air pressure helps it to stay shut, the pressure is not essential; the Schrader valve closes and stays shut even at very low pressure, making it ideal for low pressure tires.

A rim drilled for Presta valves may be converted to accept Schrader valves, by drilling it out with a 21/64" drill bit, but care must be taken to de-burr the resulting hole to prevent damage to the tire and inner tube.

http://en.wikipedia.org/wiki/Schrader_valve

 

[BentMikey]

I still see more presta than schrader valves, so I'm a bit surprised at the comments to the contrary.

As for inflating the tyres, the pot of elbow grease is thataway ---->

 

[CopperBrompton]

I got a track pump as it looked preferable to elbow grease. :-)

 

[Ham]

Sorted!

Thanks for the info guys - the problem was that I had not had any experience with this type (Presta) of valve before and was, indeed,, not releasing the the teeny tiny thingiemebob on the valve...we live and learn and, who knows? one day I may even be as mechanically adept as my dog!

 

[BentMikey]

Don't worry, I'm sure we've all forgotten to undo the release at least once!!!