FarHorizon

Not one but TWO of the last four tubes I've put on had to be discarded because of air leaks in the Presta valve mechanism! One of the two tubes was a "Slime" brand and the other I don't know.

What causes leaks in the valve seat, can I fix them myself, and what tubes are LEAST likely to suffer this problem?

Thanks!

2manybikes

Slime sometimes gets into the valves and plugs them up just like it would plug any other leak. Skip the slime tubes.

MudPie

Do they leak after you tighten the little valve?

Wow, I can honestly say that in 15 years of road and mountain riding, I never had a faulty presta valve. I even buy low-cost tubes ($20 for 10 at jensonusa.com) and never had a problem.

The presta valve is very simple, internal pressure forces the valve to close - no springs attached. When the external pressure is greater than the tube internal pressure (say when you're pumping the tire), the valve is open and air enters. I'd assume the sealing surface between the valve and valve seat is faulty (manufactuing defect, debris...). It's not worth trying to fix.

I've seen the slime tubes but never used them. Perhaps the slim compound gets around the valve seat and prevents a good seal? However, I'd imagine Slime folks thought of this already.

Maybe just statistics catching up with you? There's no law saying you cannot win the Lotto twice in a row.

Ronin

I've never used a slime presta,but have run slime schrader tubes before. I never had any trouble other than when filling sometimes you feel a bit of resistance then a pop as you blow the slime plug out of the stem when airing them up. On my presta tubes sometimes I accidently bend the little wire when airiing them up. I have considered drilling all my rims to shrader. My presta stuff seems to lose 10-15 lbs per week while my shraders seem to hold air much much longer.I do think the Giant and Bontrager tubes from my lbs seem a little better quality,but since Im frugal I usually run those ten for twentys at Jenson also. Good luck.

MudPie

Can you clarify the rate of leakage? I was assuming you meant the tube would lose its air pressure in a minute. Likewise, one can assume you're losing 10 psi per month.

FarHorizon

I tighten the retainer collar on my Presta valves after airing up. Despite this, leakage can be heard at the valve. Having checked the tube and valve under water, the air is NOT leaking from the rubber/brass interface - it is coming out of the valve core.

The leakage is such that about 30 minutes after filling the tube to 90 psig, the tire has leaked down to 60 psig. I finally replaced the tube.

I believe that the poster who hyphothesized slime fouling the valve seat is probably right, but I've no way to prove or disprove this. In fact, I suspect that the leakage is caused not by the slime itself but by some other impurity or trash that was entrained in the slime when the tube was filled. Any dirt, dust, metal, or solid of any sort that got into the tube could prevent the valve from seating despite the thread tension on the Presta nut.

I'll eschew Slime tubes for awhile and see if my average improves. Perhaps there was just a bad lot of Slimers from the factory and I happened to get two in a row...

teiaperigosa

use valve caps...that's what they are for(I think)

Al1943

Slime does not work well in a high pressure system, just don't.
A presta valve should hold just as well without tightening the nut, a valve cap won't help at all.

Al

seely

On Presta they don't make any difference.

Wil Davis

I read somewhere that originally the caps were used just to protect the tubes from the sharp pointy bit at the end of the screw which tends to dig into the tube when packed in the box.

- Wil

DnvrFox

Caps won't hold 120 psi.

FBinNY 

You had to dig up a seven year old thread just to add that useful? bit of wisdom?

DnvrFox

Oops!!

I was following another link and failed to check the post date.

Sorry - I don't do that often!! My face is red.

ImLikeWhoa

After three new inner tubes inside of a week, I believe I identified a new failure mode.


It's mid summer in Hyde Park, Chicago, and the bike shops are busy fixing flats. I go for years without getting a flat but somehow I had one now. The repairman quickly replaced the tube and fixed my flat. I went for a workout and all was well. But then a day later the tire was flat again. Again I went to the busy repair shop and got a new inner tube, after never really finding the cause of the flat. I asked for a new tire, but the repairman looked my tire over and said I didn't need one. As I left, I overheard another customer bringing back his bike after his flat didn't stay fixed. Again I went home happily, did a great workout and, and again had a flat two days later. What would cause the same odd kind of leak to happen twice? I thought I was going crazy! Then I did a simple thing and fixed the problem: a week later the tire is fine.


Did this ever happen to you? If so, read on to see my diagnosis. First, why did the tire repeatedly leak slowly when it had just been fixed. One possibility was a leak through the Presta valve. The plastic cap was on tight, so this kind of leak would be slow. But why would a new valve leak.....twice? I think it was because the repairman was cutting corners. When you install a new Presta tube, you are supposed to let some air out after you first fill it up, to clear any debris from inside the valve. Then you are supposed to screw the valve tight before putting on the cap. A repairman who is rushed for time might easily miss one or both of these steps. This would explain why another customer was having similar problems.


I pumped my tire up and let a big puff of air out, screwed the valve shut. The tire has been fine ever since

Sci-Fi

I had some Presta tubes with removable valve cores that weren't tightened correctly. Now I tighten/check every tube before installing. Majority of the Presta valves I have purchased have removable valve cores.

Only other problem I've seen is with the heavy duty or extra thick thorn resistant tubes with Presta valves. Valve separation or being torn off is more often to happen than with standard tubes.

With a bulk bundle buy, you expect a few tubes to be substandard/throwaway.

But without knowing why your tubes were leaking in the first place, it's a guessing game...especially over the Internet.

JanMM

And now it's a thirteen year old Zombie Thread!

2manybikes

Call Guinness book of world records !!

seedsbelize 

And the powers that be see no reason to return to the days of posting the date the thread was started.

ThermionicScott 

I know we've had older zombies around here. 2003 or 2004 is as far back as threads go, I think.

3alarmer 

...the old ways are the best.