Burst tyre

[Dan E]

I have just had my second inner tube burst on me in quick succession.

I have a hybrid bike which had 700c x 38 tyres on it. In order to get some extra speed I have replaced the tyres with 700c x 32 tyres with a slicker tread. Based on advice available on the web the tyre size should not be a problem for my rims.

After fitting the new tyres I pumped them up to the max (100psi) and about 5 minutes later the front tyre burst.

After doing some web research I felt I had probably pinched the inner tube between the rim and the tyre. So I got a new inner tube and carefully checked I was not pinching the tube when installing. This time I was more cautious in inflating it and only inflated to 80psi.

All was fine and I then went for a 7 mile ride and all still fine. Then an 11 mile ride. Still fine. So I then inflated to 100psi today and went out again. 2 minutes later - bang, the tube on the front tyre burst again.

Has anyone got any ideas what may be causing this? As I am within the recommended max tyre pressure surely I am not overinflating the tyres. If I am why was it the front tyre both times when both tyres were inflated the same - if anything the rear was inflated more.

I have checked the rim and tyre for any obvious debris / cause but I cannot see anything, and my thought is that anything like this would have caused a problem at 80psi as would a pinched tube.

Any help would be appreciated.

Thanks.

[Bill]

This is interesting as they are new and you say they are within limits of the maximum pressure. Dan this does not sound like your fault rather the manufacturers faulty product, maybe even a few of them. Try taking them (both that burst) back to the place of where you purchased them. Make them honor a return/exchange (different brand), or refund. I remember someone on here had a similiar experience in a different post but did find out it was a faulty line of tubes. Good luck

Bill
P.S. Wait to see if someone else comments on this.

[Dan E]

Thanks for that Bill.

I've possibly found the problem. I used my old 38 tubes when I changed the tyres to 32 so perhaps the width of the tubes pushed the tyre off the rim. I thought that change would not be a problem as it was only 6mm but maybe it is. Having just checked the replacement tube it seems like the bike shop gave me the wrong size. I explained I had changed from 38 to 32 and I got a tube for a 38 tyre - they clearly were only half listening! Obviously I should have checked so it's partly my own fault if that is the problem but that tube may go back to the shop. I've now ordered two correctly sized tubes from a different shop so I can change both and I'll see if that works. As it's a different shop and brand of tube that should rule out a defective batch of tubes. Oddly the rear tyre/tube is fine and I am using my old 38 tube still!

[Bill]

(05-18-2010, 05:54 PM)Dan E Wrote:  Thanks for that Bill.

I've possibly found the problem. I used my old 38 tubes when I changed the tyres to 32 so perhaps the width of the tubes pushed the tyre off the rim. I thought that change would not be a problem as it was only 6mm but maybe it is. Having just checked the replacement tube it seems like the bike shop gave me the wrong size. I explained I had changed from 38 to 32 and I got a tube for a 38 tyre - they clearly were only half listening! Obviously I should have checked so it's partly my own fault if that is the problem but that tube may go back to the shop. I've now ordered two correctly sized tubes from a different shop so I can change both and I'll see if that works. As it's a different shop and brand of tube that should rule out a defective batch of tubes. Oddly the rear tyre/tube is fine and I am using my old 38 tube still!

Something else you may want to do is go around the whole inner side of the wheel and tyre to check for burs (metal or other sharpies) just in case. I would recommend you do this with a cloth or something because you don't want to catch your hand on one. Glad I could be of help either directly or indirectly haha .

[Dan E]

(05-18-2010, 06:02 PM)Bill Wrote:  Something else you may want to do is go around the whole inner side of the wheel and tyre to check for burs (metal or other sharpies) just in case. I would recommend you do this with a cloth or something because you don't want to catch your hand on one. Glad I could be of help either directly or indirectly haha .

Cheers. I did look at that but I will double check as I'd imagine this could be something that is easy to miss.

[cyclerUK]

Dan,
Is the "100 psi max" stated on the tyre wall?
This seems a bit high to me compared with my own "slick" tires.
Mine say 55 psi but they are a cheap tyre. I do blow them up a bit more than that though.

[Dan E]

Yes they say 75-100 psi and I've not gone above 100. Looking at info elsewhere it seems the rule is never use an inner tube that is too large for the tyre. Slightly smaller widthwise is okay but not larger. I guess this increases the chance of the tyre being pushed off the rim especially at higher pressures. I think this is what happened with me so I'm going to try with the right tubes and will confirm once I'm roadtested in case this helps others.

[DaveM]

There is nothing per-se wrong with using too large a tube other than that it is harder to get it in straight and un-pinched. But you're more likely to get everything in correctly using the right size. 100 psi does sound high for a 32 tire, but maybe so. Note however, that listed pressures are just recommendations. Different tire and rim combinations fit differently. If the tire fits your particular rim pretty loosely, it might not be able to take 100 without slipping off even though the tire itself is capable of handling that pressure. But since the rear seems to be ok, I would check the rim and tire for problems. Go over the bead of the tire and sidewalls of the rim. Any rips, kinks, flat spots, etc. Finally, when you do install the tire, pump it up to 80 and check all the way around that it is seated correctly. Too far out is the common issue. But if the tire goes too far in in any one spot, it creates the chance for it to slip out on the opposite side.