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  1. Is my rim cracked?
  2. Do I need to replace my rim?
  3. Do I need to replace my wheel? (See left/first picture).
  4. If either 2 or 3 is Yes, what's the most frugal way to go about it?

Picture 1Picture 2

Notes

This is the rear rim.
The "cracks" feel very shallow.
The cracks are at different locations on the rim (180 degrees apart).
I bought this bicycle used (2017 Trek FX7.3) last week, and everything else is working perfectly. The seller said that he just had it tuned, and I believe him because the brakes, the shifting, and wheel truing felt perfect. Also, it was very clean. I did not get into any crashes nor drove into potholes. Honestly, I spent 10 minutes looking over the bike before buying it, but I can't remember if the "cracks" were there. I might have ignored them because I was blinded of how perfect everything else felt.

Update 1

I just checked 180 degrees opposite the valve, and I did see a joint on both sides of the rim. Those were more subtle than the damage found in the 2 pictures.
Referring to the 1st picture, there is a similar damage to the exact opposite side of the rim.
New picture (picture 3) shows the depth of the cut of picture 1.

enter image description here

Update 2

  1. Searching the serial number on BikeIndex.org, I found out that the bike was stolen 6 months ago from someone's apartment, and the U-Lock was cut. Good job folks on the investigation!
  2. Before selling it to me, the seller told me that he bought it 2nd hand during the beginning of summer (around 6 months ago)
  3. The seller is on offer up and I know his home address. He is still replying to my messages though, and he seemed very friendly.
  4. The price was good but not amazing ($460), that's why I assumed no theft. And the user profile showed no other sales of bicycles.
  5. How do I proceed?

Update 3

The seller provided me with the original offerup link with the original seller of the bike to him. He bought the bike 40 days after the bike was reported as stolen on BikeIndex.org. The original seller was a woman, so was the person from whom the bike was stolen. I still did not contact the original seller, nor I told my direct seller that the bike he sold to me was stolen. I also did not contact the police nor the original owner yet.

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  • 2
    The top picture shows the joint where the rim the rim has been assembled at the factory, all metal rims have them, often opposite the valve. But the second one makes no sense and the irregular shape of the line worries. Contact the seller and ask for explanations.
    – Carel
    Jan 17 at 16:32
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    @Carel it looks straight but the damage to the tyre sidewall above, in the first photo suggests its a gouge too.
    – Criggie
    Jan 17 at 18:44
  • 1
    @Carel High end aluminum rims have welded joints which can’t be loosened like this.
    – MaplePanda
    Jan 17 at 19:31
  • 2
    @Carel: I just checked 180 degrees opposite the valve, and I did see a joint on both sides of the rim. Those were more subtle than the damage found in the 2 pictures (The pictures are taken at different locations than the assembly joint.) Jan 17 at 23:33
  • 2
    It seems pretty obvious that something gouged the rim and tire. Could have been from hanging it on a poorly-conceived bike rack/hanger, could have been a poorly-chosen bike lock, could have been intentional damage by someone. Jan 18 at 2:28
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I will be the suspicious person, and I will wander a bit off-topic. No offense intended, I will only describe a worst-case scenario.

I make one assumption: did you buy it second-hand because the price was a very good one (given the general condition you could see from the picture)?

The bike was very clean:

  • recently bought? that would explain it.
  • cleaned thoroughly to fool buyers to cover up possible damages? that could explain it

The cut you show in the first picture is quite straight and it hits the tire as well:

  • was the bike released from a lock by using an angle grinder? A mishap with the grinder can explain both the cut on the tire, on the rim, as well as the bike having a good price and being very clean.

So yes, the rim has been cracked by an external force. If you have a proper receipt for the bicycle, you can contact the shop and ask for a replacement, maybe there is some sort of warranty, maybe they will be happy to assist you.

EDIT after UPDATE #2

Contact a lawyer. I am a pragmatic guy (if you are an optimist, you would consider me a pessimist).

  • You have no written proof you bought the bike second hand, you may be identified as the thief;
  • buying and selling stolen goods is a crime, depending on the country where you live/concluded the transaction you would have to prove (during a trial, with lawyers and all the bandwagon) that you genuinely thought the seller was legally selling something he owned.

Sure, you think you know where the seller lives, but it may be faking to be someone else (a flat mate?). A minimum that may not save your ass, but still spare you some troubles, would be getting a receipt from the seller. You can be the nice guy bringing back home the stolen bike, but remember a lot of nice persons get jail time and/or hefty fines.

Again, get in touch with a lawyer. If you think you cannot afford a lawyer, you may find some legal help through your school/universities/local NGOs...

Finally, a last suggestion: get in touch with a lawyer.

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    Along those lines, if this is in the US, you can check the serial number at bikeindex.org
    – Armand
    Jan 18 at 8:26
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    The lines look too narrow to be the work of an angle grinder. Maybe a hacksaw or something.
    – MaplePanda
    Jan 18 at 8:56
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    I'd have guessed Dremel, actually. You'd have to have a hell of a slip with a hacksaw to achieve that kind of gouge. Jan 18 at 9:21
  • 1
    @MaplePanda If you are cutting the rim with the grinder, yes, but such a narrow line can be obtained if the cutting disk hit the rim at an angle, and only for short time (like it slipped from the hand of the operator). Or a Dremel, like said in the other comment.
    – EarlGrey
    Jan 18 at 9:37
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    @Armand! Thank you! 1) The bike was stolen 6 months ago from someone's apartment, and the U-Lock was cut. Good job folks on the investigation! 2) Before selling it to me, the seller told me that he bought it 2nd hand during the beginning of summer. 3) The seller is on offer up and I know his home address. He is still replying to my messages though, and he seemed very friendly. 4) The price was good but not amazing ($460), that's why I assumed no theft. and the user profile showed no other sales of bicycles. 5) How do I proceed? Jan 18 at 16:01
5

It does not look like a crack, but a very very deep gouge from a rock or something.

I think it would be wise to replace the rear tire either way based on the sidewall gash and cotton weave being cut there. Sidewall blowouts are hard to control after the tire fails.

I guess I have never seen damage to the rim track in that manner. Without seeing it in person, and knowing anything about the wheel, it is tough to say whether it is good to go.

The answer could range from lightly sand the rim track with sand paper to remove any burs and ride the wheel to that is going to be a weak point for the rim.

I lean a bit towards that will be a weak point that can fail down the road because there is not a ton of material in that area of the wheel. If it was me, I would reach out the manufacturer to see what they think and if they have a crash/damage discounted replacement price as some companies like Bontrager will work on a case by case basis to do the right thing by the customer even if it is not their fault. If it was me, I would keep that wheel for perhaps an indoor trainer and get a replacement to ride on the roads.

Sorry to say that as I know the feeling coming back from a ride and seeing a gash in $60 dollar tires, but it certainly stinks way more when it gets into the wheel. It also is worse when you just bought a bike from someone. You may want to ask the seller about it and see if they are willing to refund you some money for a new wheel as they almost certainly knew it was there from what you describe.

3

I think generally the consensus is that brake tracks (i.e. rim sidewalls) can safely be worn down to about 1mm of thickness. New rims have 1.5 – 2mm thickness. If the rim is new, the gouge less than 0.5mm deep and there is no other damage I wouldn’t worry at all. Sand with some sand paper to avoid stress concentration along the sharp edges.

If there is less material remaining it could be unsafe, but I think with brake tracks the problem is usually them bending outwards due to the tire pressure. The gouge wouldn’t really weaken it.

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    the gouge could prematurely wear brake pads as well.
    – Criggie
    Jan 17 at 19:32
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  1. EarlGrey is right. See a lawyer. In the US, lawyers will often give an initial half hour or hour of consultation free. Otherwise, even if you have to pay $50-100 for a basic initial evaluation and advice, that makes sense to me.
  2. Does OfferUp have a money-back guarantee if you are sold stolen goods or other illegal item? Looking at their terms and conditions might be useful.
  3. I find it unlikely that your direct seller didn't notice the cut marks. They may not be a trustworthy reporter of how they got the bike. Bike theft is often an organized ecosystem in the US these days. Even if they did get the bike six months ago, perhaps that person was a confederate, and as with stolen cars, they were letting the bike cool off before trying to sell it while trying to obscure its ownership trail.
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The first photo is just the rim’s seam as Carel mentioned. Of greater concern is the rip in the tire that’s directly above it. I would just patch it with a tire boot such as this one: https://www.parktool.com/product/emergency-tire-boot-tb-2 Flex Tape or a similar strong tape would work too.

The second photo looks worse. See that black line at the very top of the gash? I suspect that the rim has been cut all the way through. If that’s the case, the rim will be very susceptible to failing. To check, remove the tire and shine a flashlight on the damage. If you can see light going through to the other side, the rim is mortally damaged. In a pinch, you could use a very strong epoxy like JB Weld to reinforce the area, but there’s no guarantee this would be a permanent fix.

Edit: with the additional information that photo #1 is indeed not the rim’s seam, the rim is pretty much done for. I have no clue how that kind of damage could even happen, but it sure looks sketchy to me. You should definitely consult the person you bought it from for more info.

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    note the gash in the tyre above the 1st photo- straight gouge in the rim: probably not the rim joint on this occasion.
    – JoeK
    Jan 17 at 21:17
  • I'd just be cautious about boots as they really are only meant to get you back if stranded. I think anywhere other than the sidewall would make it a bit more ok to boot it or just let it be. I think it was GCN or parktools that even suggested stitching tears in the sidewall to reinforce the cotton plys in situations like this. Jan 17 at 22:02
  • @JoeK I’m not 100% sure what you mean by that comment. The gash in the first photo looks to be a pinch flat (tire was squeezed between rim and ground). I am positive that the line in that photo is the rim seam, which has slightly separated from the impact.
    – MaplePanda
    Jan 17 at 22:11
  • @TudeProductions MTB and hybrid tires are usually thicker and stronger than road tires, so it should be fine. The boot only needs to stop the tube from herniating out of the gash. I wouldn’t ride such a repair on my road bike (regular fast descents = no no), but I’d be perfectly happy to on my MTB where the consequences are minimal. It all depends on what OP’s risk/cost tolerance is I guess.
    – MaplePanda
    Jan 17 at 22:19
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    @MaplePanda OP has now clarified " (The pictures are taken at different locations than the assembly joint.)" So, two(!) cuts to the rim plus gouging, both not at the rim joint, and a cut in the tire in line with one of the rim cuts. This looks to me like it was done with a tool, not just a riding hit. I think the rim is toast (or a gift to your worst enemy).
    – Armand
    Jan 17 at 23:43

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