Tube explodes, taking out rim - advice needed

[skupp]

Hi guys,

First post, but have been lurking on the site for a few weeks now.

Just started commuting to work, around a 30 mile round trip, but today as I was cycling into work (sun shining, birds singing), my inner tube exploded, taking out the side of my rim.

Tyre was inflated to 120psi, so not quite sure what happened to cause this damage...

Question is, do I just need a new rim, or should I buy a new wheel?

My bike is a Langster single speed, the damaged rim is my front wheel, mavic cxp 10, 622x13, quick release.

Any advise gratefully received, as I am a total newbie in regards to cycling.

Cheers!
Daniel.

 

[domtyler]

Never heard of that happening before and sounds like a severe manufacturing fault to me unless you have damaged the rims somehow?

Would you be able to post a picture? I'd be quite interested to see it.

 

[gbb]

I'd be inclined to think it's the rim that's failed...that in turn causing the tube to blow (once the rims gone, there's nothing to contain the tube then )
Old wheel ?, damaged, worn braking surface ?

As dom says...pics would be interesting.

 

[Tim Bennet.]

How old was the rim? If it was new then there was some sort of fault that needs pursuing. But if the brake surface was well worn, then that is what happens if you leave it too long!

You can get a new rim built into the wheel, but unless the hub is a good quality one and has been well maintained it may not be worth preserving, especially as perfectly good wheel sets seem to cost less and less these days.

 

[shades.5]

Hang on tight , sorry couldnt resist

 

[Steve Austin]

Some tyres and rims don't work too well together and can blow off quite easily at that sort of pressure. Was the inner tube too big? ie rated for a wider tyre?
and was the rim worn?
worn rim+big inner tube+big tyre+narrow rim=blown tyre ime

 

[Globalti]

If the tyre took a curl of rim off with it, the answer is that your braking surface had finally worn through or a small stone had got trapped in the brake block and carved a groove in the braking surface.

Maybe now is the time to learn to fit a new rim by taping new alongside old then moving the spokes over one by one? This is not as difficult as it sounds if you take your time and go systematically.

 

[skupp]

Hi, Thanks for the replies
Will upload pics tonight when I get back home. Ears have stopped ringing now, sounded like a gun shot when it blew....

Not sure how old the rim was, bought the bike secondhand, its a 2005 model, rims looked new, and had new tyres on (gators).

Tim - Dumb question here, but how do you know if the brake surface is well worn? (besides it spectaculary failing and giving the neighbourhood a wakeup call)

Shades - It happened near the bottom of the hill, going a reasonable rate of knots... Woke me up for sure...

Steve - I had done close to 800 miles on the same rim/tyre, will check inner tube size tonight...

Rigid Raider - Small stone in the brake block might be the culprit, as the curl (or lip) of the rim has been sheared off, 30 cms or so, along with a similar tear in the inner tube as well...

Will need a few puncture patches to fix this one I think
Cheers!
Daniel.

 

[dodgy]

Tim - Dumb question here, but how do you know if the brake surface is well worn? (besides it spectaculary failing and giving the neighbourhood a wakeup call)

Many rims have a small indented cross on the rim, this cross (x) starts to disappear as the rim wears.

Dave.

 

[Perry]

Answering your question, I'd say get a new wheel but also check the condition of the rear wheel too as you may need to buy a pair.

 

[skupp]

Pics as requested

Rim was sheared almost half the circumference of the wheel, same damage evident on the inner tube...

Now got to edumacate myself on wheels and such...

 

[Tharg2007]

try using the macro mode on ur camera, looks like a flower.

 

[andrew_s]

Dumb question here, but how do you know if the brake surface is well worn? (besides it spectaculary failing and giving the neighbourhood a wakeup call)

Most recent rims have some sort of wear indicator - they can't be sold in Germany otherwise. However patents mean that every brand has its own type of indicator. Generally, there's either an indentation in the braking surface that disappears once the rim is worn, or there's an internal cavity that shows as a hole in the braking surface once it's worn enough. It may say what to look for on the rim label.
Example of an internal cavity that's worn through (Rigida?)

If your rims are old versions, or you can't find what to watch for, you can either measure the thickness of the rim wall, or pressure-test it at intervals.
Pressure Test:
Take a track pump and inflate to something like 50% over what you usually use, and leave overnight. If it hasn't gone bang, and the rim walls haven't observably started to splay out, it's still OK. You may like to wear ear defenders, and delayed failure may give you a fright in the middle of the night.
Measurement - scrap if under about 0.5mm:
Not terribly easy because you have to get in under the hooked edge of the rim. A specific tool like this is easiest (I have seen cheap versions on eBay - you've just got to come up with the right search term), but otherwise you will have to do something like measure spoke+rim+spoke, and then subtract the two spokes.