push bike puncture query

helpimcrap

helpimcrap

helpimcrap

Soldato
Joined
13 Jan 2004
Posts
12,738
Location
Leicestershire
Hi guys,
Basically i have 2 innertubes which went down on me in seconds in after i ran over a couple of small stones after covering about 8miles.

Put old innertube in at road side and blew up with CO2 canister - no idea what pressure it blew up to but they are great!

Got to work and back again (roughly 15miles) and the one i put in is fine.

I tried to fix punctured innertubes - on one i did the test in a bowl of water (then dry and apply patch) but after the 5th one i think innertube is knackered - so tried the other one and got to the 2nd patch so figured that was the same.

My question is:-
Have these punctured because of too much pressure? My uncle put in 120psi as that's what he races at and hence he knows more about this than me. I said i read that 90-100psi was fine for the road.

Is the above what innertubes do when you have too much pressure in and it bursts/explodes as soon as i hit the stone?

Figured i need 2 new innertubes?
 
The way you have described it sounds a lot more like you had the tubes under-inflated.

Presumably the tubes haven't just exploded, as you wouldn't be able to try and fix them, plus you would have to put a lot of air in them to do so. Which is presumably possible with a gas canister when the tube isn't in the tyre.

What is likely to have happened is that when you hit the rocks, there was too much give in the tyre due to the under-inflation, it then compresses the inner tube against the rim and the tyre causing a snake bike puncture.

Such punctures often look like a snake bite. If it was something else you can usually find debris in the tyre itself.

Your own weight also plays into what you should have the tyres inflated to, along with the puncture resistance of the tyre and likelihood of the route you are on having something that might cause one.

If you have had to patch each tube with a number of patches, it probably makes sense just to fit new ones.
 
Definitely 120psi.

Hard as nails!

Have had a mountain bike for 10 years and i pump the tyres up to about 35psi if on road or down to about 20 if off road. Same innertubes as one of them (slime inside tyre) and have only ever had to pump it up a few times.....

Tyres look fine - innertubes look as though the rubber has burst as there is a number of holes all round the innertube.
 
Was there any debris in the tyre? Is its punctured by a sharp then it usually stays in the tyre and will more than likely cause more punctures. Running with lower pressures allows the tyre to deform around the sharp and means you should get fewer penetration punctures.

However, lower pressures increase the likelihood of pinch punctures when the tyre pinches the tube against the rim. This usually happens when you hit a pothole or similar and sounds like what you are describing.

Ideal pressure depends on a number of factors like tyre size, rim width, usage and weight.

I run 25mm road tyres on 19mm wide rims at 110psi rear and 100psi front and I weigh 160lbs. I also run 24mm road tyres on 23mm wide rims at 95psi rear and 90psi front.

It's a bit trial and error and finding what works best for you I'm afraid.
 
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