[Cycle chat] Punctures

[8115]

I've had two punctures two days apart that were like massive noisy blowouts. There was nothing in the tyre for almost definite when I changed the first one, someone suggested today that it could be the wheel. What am I looking for when I change the second one? Like, anything jagged? I've never had a puncture like this before. I hope I don't need a new wheel. Thanks.

 

[Frumious B.]

You won't need a new wheel unless the rim wall has worn through because of lots of braking. Has it? Also feel all the inside surfaces of the rim with your fingertips. Could be a nick in the rim or some trapped grit or a shard of glass. Maybe a spoke end is poking through the rim tape. Maybe the rim tape has rotted. Remove it and check that the spoke ends are not sticking proud of the spoke holes. Also check the hole which the valve goes through, maybe the edge of the hole is a little rough.

 

[fredfelt]

As he said - but there's also chance you put the tube in badly. Perhaps it was folded inside the wheel - this can cause punctures.

Take note of where the blow out was - use this to help identify were any problem area on the wheel or tyre is.

 

[BigTom]

You won't need a new wheel unless the rim wall has worn through because of lots of braking. Has it?

Just to add to this, you can tell whether it's worn through by looking for a line on the rim. Some wheels have a line that gets rubbed out in places when the rim is worn, others don't have a line, but it starts to appear when the rim is worn.

So if there is either a solid line or none at all you're fine but if you've got a broken line you're not.

 

[Frumious B.]

As he said - but there's also chance you put the tube in badly. Perhaps it was folded inside the wheel - this can cause punctures.

Take note of where the blow out was - use this to help identify were any problem area on the wheel or tyre is.

Troo dat. That's known as a pinch flat and is quite common. To avoid it, don't fit a new tube when it's in its folded-flat-straight-out-of-the-box shape. Make it into a sausage shape by inflating it a teeny bit and letting most of the air out before you fit it. I hope that makes sense! There are probably lots of youtube tutorials which show it.

Another way you can get explosive punctures is when the tyre is so worn that it starts to split, but from what you say that can't be the case this time.

 

[maomao]

Check the inside of the tyre as well, can sometimes get a bit of shrapnel stuck inside or poking through the tyre that causes repeated punctures. No easy way to do that, just have to run your fingers round the inside of the tyre.

 

[DownwardDog]

Blu Tac around the inside of your tyre will find puncture causing objects that are hard to find by eye/finger.

 

[weltweit]

Checking where the puncture is will give a good idea if the failure was in the tyre (puncture will be on the topside of the tube) or the metal of the rim (puncture will be on the underside of the inner tube). If on the underside of the tube, indicating a problem on the rim, you can work out how far the puncture is from the valve and this will indicate where about the issue is on your rim.

 

[weltweit]

Next time, before you take the tyre off, chalk the tyre where the valve is. When you find out where the puncture in the inner tube is you can then go to that area of the tyre to investigate what caused it.

 

[Sigmund Fraud]

In a word, 'rimtape'.

 

[weepiper]

Catastrophic blowouts are usually a result of the tyre not having seated properly when you inflated it. When you pump it up after changing the tube and refitting, get it up to 20psi or so (soft but holding shape) then stop, take the pump off and spin the wheel. Look along the sidewall and see if the bead (in this picture it's what looks like a dotted line close to the rim) is an even distance from the rim all the way round. If there's any bits where it's rising up/making the wheel look wobbly, grab it with your hand and squeeze until the bead slips down to where it should be. Then pump it up another 20psi or so and check again. Some tyre and rim combinations just aren't very good together and you may find that you have to get a different brand of tyre.

 

[weepiper]

The other possibility is that the tyre sidewall has got frayed and there's a hole where the tube can bulge through, like this

 

[8115]

The prize for correct guess goes to weepiper (and others). New tyre time it is.