The perils of 23 mm tyres …

[Samuel D]

I know most of you have more sense than to run 23 mm tyres, but I can’t seem to break the habit. My most recent excuse was that a friend was selling a pair of nearly new 23 mm Turbo Cotton tyres for cheap. (Specialized calls them 24 mm for marketing reasons.) I’d always wanted to try those.

Anyway, I was bombing along in a small group when I rode over a stone the size of a table-tennis ball and heard a loud whack. On a climb later I noticed the rear brake was dragging, which I thought a bit funny. I didn’t put two and two together. Instead I backed off the barrel adjuster from the saddle and thought no more about it.

At home I discovered this:









The three spokes nearest the damage were practically slack, hence the brake rub. In addition to the obvious dent, the rim was radially bent inward. The rim wall at the damage site was about 1.1 mm thick, which seemed too thin to be worth an uncertain repair effort, so I re-rimmed the wheel with the existing spokes and nipples and put the whole thing down to experience … though I could do with acquiring experience of this sort a bit slower.

A curious thing and the reason I post this with pictures is that this impact didn’t cause a puncture. There isn’t a mark on the latex tube, and I mean nothing. The tyre was fine too. Makes you wonder about recent trends, huh?

[fossala]

I've always been an advocate for bigger tyres but recently got a Bob Jackson made that only accepts 25mm with guards. What a revelation! It's not the speed that I'm enjoying, it's the cornering. When I'm jumping on my commuter (38mm) on a Monday after some long riding at the weekend I'm missing the narrower tyres and will likely go down to 28/32mm when this pair wear out.

[Mick F]

I was 23mm for years with Mercian.
Then I went to 25mm because I had a pinch puncture or two in fairly quick succession.

TBH, I miss the 23mm tyres. 25mm is fine, but not as fast maybe. Maybe not much difference perhaps, but I still have some part worn 23mm so I may re-fit them when the present 25mm wear out.
The bike won't take anything wider than 25mm and still retain mudguards ............ and brakes.

[NATURAL ANKLING]

Hi,
I have always used 23's on a road bike, a lot of wheels I pull from the skip are dented one way or another.
But I always keep my tyres well inflated even off road wider tyres, hence never seen the like but I am alone rider and there is not much else to do except stare at the road

You should be able to tap that dent out OK.

[Samuel D]

You should be able to tap that dent out OK.

You might be right and I’ll maybe give it a go before throwing it out. The radial bend will be harder to fix than the dent. However, the brake tracks are concave, so there’s not a lot lost if I can’t repair it.

As you mention, this kind of thing is easier to avoid when riding solo. I didn’t have much time to get the front wheel around the rock and I caught it pretty nicely with the back wheel. These things happen in a group although less so when I’m leading because I don’t have the popular fetish of passing obstacles at daredevil closeness.

I was surprised the tyre could hit the rim hard enough to do that damage without pinching holes in the tube, latex or not!

[mjr]

16mm rim tape? So 19mm rims? I usually use those with 37mm tyres! Ideally for 23mm tyres, I think it should be 13mm rims. So I'm not surprised at the rim damage but wouldn't blame the tyres.

[Samuel D]

The rim is a Mavic Open Pro C. Mavic suggests 18 mm rim tape for that rim, but I used what I had available.

[robc02]

I have managed to fix a radial dent (or flat) as follows:

1. Remove the spokes in the damaged area

2. Support the outer of the rim on blocks of wood either side of the flat section. I might have done this with the inflated tyres in place, if not some padding between the wood and rim would help spread the load.

3. Place another block of wood on the inside of the rim resting on the flat section. I used a length of 2x2 (or maybe 2x4) for this.

4. Whack the end of 2x2 with a large hammer.

5. Repeat stage 4 as required!

I was pleasantly surprised at how well this worked. As you can see, I did it with the rim built into a wheel. I am sure you could do it with the bare rim, but it would be harder to check the result as you couldn't spin the wheel to check it.

[Spinners]

I've ridden 25C's and wider for a while now but my current favourite ride had 23C's on when I bought it second-hand a few months ago. TBH there's not much difference although I have put 25C's on it but only because the old tyres looked a bit worn.

[thelawnet]

16mm rim tape? So 19mm rims? I usually use those with 37mm tyres! Ideally for 23mm tyres, I think it should be 13mm rims. So I'm not surprised at the rim damage but wouldn't blame the tyres.

I'm not so sure that these are 19mm rims, but fwiw 19mm rims are pretty much the standard nowadays, and 23mm are the narrowest recommended for this rim size, but probably 25mm would be more commonly fitted

[iandriver]

Looks like you had a bit of a side hit rather than straight on. Not convinced a bigger tyre would have 100% saved you. Unless you're running 2inch +.

It almost looks like it wrapped around and clattered the side of the rim.

[Brucey]

I posted a while back on how to get rid of long-pitch lateral rim deformations. That rim has three problems (in addition to one of those, presumably)

1) the dink in the braking surface
2) a long-pitch radial deformation
3) the brake surface is worn a bit thin.

To get rid of the dink, lay the wheel at an angle of about 15 degrees so that the dinked edge of the rim is supported on the far jaw of a smooth-jawed bench vice or on the edge of a length of 4x2" timber. Lay another piece of timber across the damaged part of the rim and give it increasingly sized whacks with a hammer until you see something happening. When the dink has come out, measure the rim width very carefully; chances are that it is now slightly wider where the damage was. If so, give that part of the rim a gentle squeeze in the (smooth-jawed) bench vice until it comes back again. If despite your efforts the rim is still not perfectly smooth, note that this rim is probably best used as a rear rim; brake judder (which may only be temporary) won't be such an issue by comparison with the front.

To get rid of the radial deformation, leave the wheel at full tension and remove the (~four) spokes near the damaged area. Then do as Rob suggests or you can , with care, on rims that are no greater than ~20mm depth, just hold the wheel up by hand (i.e. so that it isn't supported from beneath) and give the rim a smack directly using a soft-faced hammer; this requires some skill (in order not to hit the hub, the hammer head has to be swung so as to make a slightly glancing blow with the rim) and only works at all by virtue of the inertia of the wheel. With a rear wheel you can remove the freehub body so that you have a better swing at the rim.

I much prefer this method because I have found it is virtually impossible to support a wire-on rim in such a way that it isn't deformed at all by the supports. Once you have done a few rims you can gauge how hard you need to hit it to deform the rim. Note also that this method flies in the face of Brandt; he recommends that you detension the wheel before taking the damage on. I'd agree re lateral damage but in this case I have found it is better if you keept the tension in the wheel; it actually reduces the radial load required to reset the rim.

There's nothing much about 3) you can do; occasionally when dealing with 1), the rim splits, so I'd suggest that if the damage looks bad, try dealing with that first, otherwise your efforts elsewhere might be wasted.

cheers

[Samuel D]

Thanks, all. Are dented rims that don’t cause impact punctures reasonably common?

Mathieu van der Poel’s mechanic may need a few of the tips above after hitting a rock the other day.

[Brucey]

it happens... most tyres are vulnerable to damage in any event that deforms the rim though.

cheers

[andrew_s]

Not necessarily.

I had a pothole impact one time that took about an inch off the rim radius (at the middle of a 3 or 4 spoke flat spot), but there wasn't a pinch puncture or any apparent tyre damage, or any rim flange damage.
The rim was straight enough, but it wasn't possible to set the brake blocks so they neither braked on the tyre nor went in the spokes, so there was nothing to do but ride home (thump...thump...thump...), and rebuild with a new rim.

Probably 28 mm tyres, but long enough ago that they could have been 25.