Cycling UK Forum

I've discovered - after suffering a series of punctures all in precisely the same spot and with no corresponding tyre damage - that the rim joint on my front wheel (Fulcrum F7) is very slightly out of line - I can only tell this by running my finger along the inside of the rim. The offset is tiny - only a fraction of a mm - but I can feel it. Evidently enough to puncture the inner.

This may be due to a collision I was in a few weeks ago. Anyway, I'm going to scrap the wheel and have ordered a replacement. The hub is close to the end of its life too.

Bearing in mind the time of year, it may take a while for my order to arrive. Question: if I smooth down the joint with emery, would it be safe to continue using the old wheel until I get the new one? It would be only at low speeds on the level, and no sharp turns! There is no evidence of movement between the two 'ends' of the rim. Just this slight misalignment.

That's probably what I would do!

I'd suggest that smoothing it off, or applying a little tape over the bad bit would prevent it from causing any further trouble.

Do, of course, be sure that it isn't the rim tape that is at fault.

cheers

No, I checked over the tape carefully and it's perfectly positioned, no tears or snags. I've had rim tape problems before and this wasn't it...

I rubbed down the joint with emery, put the tyre back on and did my commute this morning, no probs. I think it simply sustained a bash and wasn't actually loosened in the crash. But I'll keep an eye on it.

It occurs to me that, with the tyre inflated, the rim is under compression, with a force tending to push the 'ends' together. So the risk of it coming apart there is highly unlikely. Much more dangerous is the risk of a rim side blowout due to excessive wear . I've been there! But this rim still has plenty of 'meat' on it.

The tyre pressure force may not be holding the joint together, and anyway is small in comparison to the spoke tension force. That is holding the rim joint together, with an estimated force of about 500kg across the joint.

cheers

As wheels get older the brake surface gets thinner and more concave and will eventually fail, often in an explosion of the tube, the rim splits and gets stuck in the fork crown area, the result would be similar to sticking a broom handle in your front wheel when riding along; not a happy momenty normally to say the least! In your case as it's an older wheel that you are looking to replace anyway then as long as the rim wall is thick enough and the hub has some life in it then no harm in getting every last mile out of it; rims often develop a sharp edge and smoothing down that sharp edge often cures the problem of repeated punctures.

You'll be amazed how many don't think to check their wheels rim thickness, not a bad habit to get into with old wheels especially in checking how concave the rim wall is getting; they are not exactly that thick to start with, don't forget to allow for the rim lip that grips the tyre bead, factor that out and it becomes more obvious how thin rims are when new let alone how fragile a grooved worn thin rim will become.

Paul

Paul Smith SRCC wrote:You'll be amazed how many don't think to check their wheels rim thickness, not a bad habit to get into with old wheels especially in checking how concave the rim wall is getting; they are not exactly that thick to start with, don't forget to allow for the rim lip that grips the tyre bead, factor that out and it becomes more obvious how thin rims are when new let alone how fragile a grooved worn thin rim will become.

Mea culpa . Been caught out twice that way: once, the wheel literally folded up beneath me - fortunately just as I was setting off from stationary so I didn't go down. The second time was going round a roundabout, the rim went with a spectacular BANG! alarming passersby all around me, but once again I managed to keep control - just!

And, to my infinite embarrassment, I once nearly finished off Mrs P that way. Thing is, I knew that her front rim was near the limit, I just thought it would last a few more days. Famous last words. I'd just pumped up her tyres. It didn't. She was about 1/2 mile ahead of me when she went down: by the time I reached her, anxious bystanders were gathered round and someone had called an ambulance. Fortunately she got away with minor cuts and bruises. The wheel and tyre, of course, were write-offs.

I've had my warning. I've been watching rims religiously, since then.

If you've got a vernier and a file, its not difficult to measure your rims' thickness.
I think its better to measure at several places round the circumference than to measure in one place very accurately.

531colin wrote:
If you've got a vernier and a file, its not difficult to measure your rims' thickness.
I think its better to measure at several places round the circumference than to measure in one place very accurately.

What a simple brilliant solution; love it

Thank you...

Or get one of these: http://www.ebay.co.uk/itm/BICYCLE-RIM-G ... 0581931984