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Dented Tubeless MTB wheel - what to do?


Stumpyrider
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I managed to severely dent my American Classic rear wheel on a rocky descent during the MTN Cullinan Marathon yesterday. It happened late in the race, so I took the decision to just stop ocassionally and top up the slow puncture as and when needed - hoping that the Stans would eventually find its way in there. This decision was regretted as the race wore on - the leak became worse and the stops annoyingly frequent - to the point where putting in a tube within 5km of the finish became an option!

 

Where do i get this fixed? Can my LBS sort me out, or is this is a specialised problem? Will they just send it away somewhere and charge a comm - and if so, where do they send it?

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try straighten it yourself. Use a pliers/ vice grips and something to protect the rim from getting scratched. I had a couple of minor dents in my AC rims (didnt leak air tho) and I just straightened them out with a mallet :D

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try straighten it yourself. Use a pliers/ vice grips and something to protect the rim from getting scratched. I had a couple of minor dents in my AC rims (didnt leak air tho) and I just straightened them out with a mallet :D

 

Thanx - will give it a try, but the leak is telling me that the sealing tape on the inside has been damaged - will take the tire off and get a closer look.

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Its possible that it damaged the tape, but it might have just pushed it away to the side so that the seal is broken. The rimstrips dont seal nicely if everything isn't 100% straight.

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Dont attempt to undo the dent with a pair of pliers, shifting spanner or similar. This will simply add some very sharp and localised dents. Tools like that cannot reach deep enough to undo the dent. If you just do a mock attempt with one of these tools you'll see what I mean. This requires some more specialised surgery. If you are in Jhb, contact me and I'll sort it out for you.

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Actually, the AMC Tubeless has a VERY low rim hook just like Stans... so no need to reach anywhere deep.

 

Take a small shifting spanner and cover the rim hook with a thick piece of cloth, or folded/cut plastic ice cream container lid, between the shifting's jaws to protect the rim from indentations. The AMC Tubeless has a built in bead hook and THAT'S actually where the sealing takes place. The bent rim hook now prevents the tyre from snapping onto the bead hook and that's why it's leaking there.

 

VERY carefully start straightening it moving along the rim edge.

 

DON'T try to bend it all the way at the first go. Little by little.

 

I have experience bending American Classics and specially the new Tubeless type. I have completely flattened a rim hook for almost 5cm and managed to save the rim.

 

A word of warning before attempting to bend:

 

They are VERY soft. You'll be shocked at how easily they bend.

 

The rim sidewall is very very thin and if the dent has folded the rim hook double/flat, a full bend to 90 deg straight might crack the rim sidewall. In that case, rather bend it until the tyre seals again, but once it seals, don't bend it further as the rim might crack.

 

You want to get the rim hook far enough outwards so the tyre snaps onto the bead hook properly.

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This thread is putting doubts in to my mind about getting a set of new American Classic 26 tubeless disc rims. The price of the rims, considering their weight is arguably the best value for money from what I've seen. Compared to XTR's, Crossmax SLR's etc. But if they fold like a tin can, that's no use! :blink:

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I recently performed the same procedure as described by Brighter-Lights on my dented Stans Flow rim.

Doing this may leave a small stress crack in the rim afterwards as aluminium does not like being bent and straightened again.

Even with a small stress crack you can still ride, obviously if you hit that exact same spot hard again on a rock or solid object the rim could be toast.

I have also straightened my Mavic 819 UST rim this way.

There is probably a better procedure out there but I am no panelbeater.

I am happy to learn from the experts...

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This thread is putting doubts in to my mind about getting a set of new American Classic 26 tubeless disc rims. The price of the rims, considering their weight is arguably the best value for money from what I've seen. Compared to XTR's, Crossmax SLR's etc. But if they fold like a tin can, that's no use! :blink:

 

They are fine. I've put a couple 1000km's on mine. I dented my rear when running low pressure and pinched the sidewall in a race when I hit a rocky section too fast... after that, I couldn't get the tyre so seal again and got a further 2 pinch flats.

 

I'm 68kg, I ran Panaracer Speedblasters 1.95 which is more like a 1.8 at 2 bar on a full suspension and no problems, I'm just a bit more careful over big rocks. With a large volume like a Race king 2.2 or a Crossmark 2.1, you shouldn't have a problem. I use Crossmark 2.1's for training @ 1.8 bar and they're fine.

 

BUT they are very soft... I was shocked at how easily I straightened the sidewall when I go that hard hit... much softer than any rim I've bent before...

 

So too low pressure and a hard hit could cost you some...

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This thread is putting doubts in to my mind about getting a set of new American Classic 26 tubeless disc rims. The price of the rims, considering their weight is arguably the best value for money from what I've seen. Compared to XTR's, Crossmax SLR's etc. But if they fold like a tin can, that's no use! :blink:

 

No need to make your decision based on this incident. It is quite common for that type of rim damage when the wheel bottoms out. I see it on beefy DH rims and X-country rims of all brands.

 

They're all made of aluminium and at that scale, the type of aluminium is almost irrelevant. Most rim companies use 6000 series, Stans uses 7000. Yet the difference is not noticeable since the beads are so thin that the difference between damage is a matter of a few kgs. When you're bombing downhill, those kgs are easily generated by your speed and impact.

 

A better rule of thumb than anecdotal evidence would be to choose he heaviest rim. The heavier, the more metal. However, heavy is a swear word around here. I'm sure admin will put it on his censor list after this post.

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A better rule of thumb than anecdotal evidence would be to choose he heaviest rim. The heavier, the more metal. However, heavy is a swear word around here. I'm sure admin will put it on his censor list after this post.

 

LOL, well said Johan

 

My most durable rims ever were Sun Ditch Witch...now these were heavy, wide mothers but allowed me to ride over stuff that I should have gone around on my old hardtail.....

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Thanx Guys - some very useful stuff here.

 

I fully deflated the tire and found that the sealing tape has got a 1cm tear/nick in it approximately 1mm from the top of the rim.

 

I did manage to get the dent out with a pair of pliers - it's not perfect, but once the tape is fixed, it should be ok? Do I need to replace the tape or is there a way to fix it?

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Get your shifting and pliers out !!! It is a 10 minute job and your rim will seal as it always has . Do it on my XT rims often and have also had to do the ZTR rim once . But if the lip of the rim has curled around take it to Johan as that will need special tools and knowledge .

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My mate and his son have had similar problems with their AC MTB rims, son is 9yrs old, and has put nice dents in them doing 20km races.

Yes, they are light....but way too soft.

Have been using XT's now for 2yrs with no problems.

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Maybe I should explain a bit better why I don't recommend the shifting spanner trick. It will work and it will bend the ridge back. However, when I said its reach is not enough, I wasn't talking about the inside of the rim. It's the outside, where the short reach (essentially determined by how far the spanner can move in on the inside) tends to put fresh dents on the outside of the rim just underneat the first inside wall. These little dents are therefore in a hollow section and it is impossible to reach behind and get them out again.

 

Brighter Lights described a method that will no doubt avoid the problem of secondary dents - that of cushioning the fulcrum end of the spanner.

 

I find that hammering the dent out is a far more effective way of getting it almost perfect. However, don't take hammer to rim quite yet, I'll take some photos and show the technique in a separate posting in Tech Q&A. You'll need only three tools and with some understanding and patience anyone can fix a rim. In fact, this skill is a very useful one to have if you ride over rocks.

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