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Consider:

Enter image description here

I was riding my local trails today, got a flat tire (due to not riding tubeless) and before I realized it, I hit a jump with too little air in the tire and I bent my rear rim.

Is it is fixable? If so, how? Or do I need to buy a new one? I would really like to avoid spending money as my wallet is kind of low now.

Rim is aluminum.

Thanks for the help, guys. I don’t care about the looks; I was just concerned about the safety. I will try to carefully straighten it a little. I also washed the bike, so I have better detailed picture of the rim.

Enter image description here

Enter image description here

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    Someone with the right skills should be able to straighten it out, but there is a danger that the metal has been strained to the point of becoming fragile.
    – Daniel R Hicks
    Nov 26, 2022 at 22:25
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    Likely a shop would (reasonably) refuse to attempt to straighten it and insist the only satisfactory repair is a new rim. The risk of unhappy customer and liability would make attempting a repair too risky.
    – mattnz
    Nov 26, 2022 at 22:34
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    Only tangentially related but the statement "got a flat tire(due to not riding tubeless)" is a bit extreme. Even people who ride their MTB tires tubeless still get flats at times (and consequently bend their rims if unlucky...). While I happily ride tubeless I am writing this comment to somewhat balance the narrative of "you absolutely have to ride tubeless to enjoy MTBing" that seems to have taken over the internet.
    – user2705196
    Nov 27, 2022 at 15:29
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    @user2705196 hey, I didnt mean for people to take that statement this way, I didnt properly explain it. Im happily riding tubes for the last 9 months, since I got this bike. In the morning before the ride I was fixing a leak on that tube but after 2 hours it started loosing air again which I didn´t realize until I smashed my rim, thats where the statement came from, I understand why it got missunderstood.
    – Andreas Patrik Lukáč
    Nov 27, 2022 at 20:48
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    With the added photos showing the crack, you should replace the rim. If money is a big problem and you need the bike for commuting or something, I suppose you could extract a few more rides out of the thing until it truly fails, but in my opinion that would generally be a poor risk-reward judgement. Oh, and it's not just a paint crack. The sort of "crunchy" texture you see is pretty indicative of overly strained aluminum.
    – MaplePanda
    Nov 27, 2022 at 21:48

2 Answers 2

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UPDATE That aluminium rim is cracked. You should scrap it immediately. The crack is a weak point and if you try and straighten it, the crack will widen.

The air pressure in the tyre will lengthen that crack over time to the point the whole lip peels off. Sorry not what you want to hear, but:

That rim is dead, replace.

ORIGINAL (based on first photo only) I suspect you could make it better by removing the tyre and careful/gentle application of a hammer via a block of wood.

The main risk is that aluminium does not un-bend very well, and is prone to letting-go suddenly as you try and straighten it. Once a chunk is broken out, it becomes utterly unsafe to ride and you need a new one.

Since the tyre is holding air right now (because of the tube probably) and because you have a disk brake not a rim brake, the wheel seems to be rideable as-is.

It all comes down to your comfort level for risk. A second landing like the one that dented your rim will do more damage again in the same spot, and you can't reasonably control what part of your rim hits the ground.

This tyre will probably not seal well enough to this rim for tubeless use ever again. Also, that spot won't be doing the bead any favours; it will wear on the tyre's sidewall and accelerate wear.

If it were my personal bike, I'd try reducing the bend with hammer and spreader, with the clear realisation that if it cracks it's done and I need to buy a new rim. I'd aim for "better" and not push for "straight"

If it were someone else's bike, I'd explain the risks and support whichever they choose. If you do pop for a new rim, you get the fun experience of building a wheel too.

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    I'd search out a similar-profile rim, and learn the mysterious arts of wheel-building by transferring all the spokes/hub/tyre over to the new rim. You could salvage a used-but-okay rim off a wheel with a damaged hub etc. Could be cheaper than buying a whole new wheel or a new rim and paying for the rebuild.
    – Criggie ♦
    Nov 27, 2022 at 21:27
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When dealing with dents like in the first photo only…

I get dents like this all the time. I straighten them out with a crescent (adjustable) wrench.

Start with small movements to get a feel for how the metal responds. Don’t make any big corrections in a single area. Small corrections over the length of the dent. Rinse and repeat.

It’ll never be perfect, but it won’t have to be. I’ve never had to throw away a rim and I’ve always been able to get the tubeless tires to seal again.

Here's a photo for the first dent I ever fixed:

enter image description here

Good luck and go slow.

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    +1 on this. An adjustable wrench is the way to go.
    – MaplePanda
    Nov 27, 2022 at 4:26
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    It’ll never be perfect, but it won’t have to be. Well, it'll likely never work with a tubeless tire ever again. But I'll echo @MaplePanda here: an adjustable wrench works here. FWIW, I've done the same with rim-brake road rims with 23s and it worked there with just a bit of barely-noticeable brake shudder. With a 2"+ tire or similar on a disc-brake wheel, any rim imperfection won't be noticed at all.
    – Andrew Henle
    Nov 27, 2022 at 16:17
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    Based on the new photos showing the crack, would your answer be the same ?
    – Criggie ♦
    Nov 27, 2022 at 21:27
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    @Criggie yeah. That second dent is pushing my comfort to its limits.
    – Paul H
    Nov 27, 2022 at 23:56
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    @AndrewHenle prior to seeing the second, much worse dent, I would have fully expected a dent like to have maintained an acceptable seal. Like I said, I get dents like the first one all the time and I’ve never had issue maintaining a seal prior to or after fixing them.
    – Paul H
    Nov 28, 2022 at 0:03

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