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unfortunately I got hit by a car. I was on the main road, in the cycle way and the car had a stop sign coming out of a school. He did see me but got distracted by the kids. Anyway, I was wondering if you could help me out determine is my bike is safe to ride or I should do anything about it. The rear fork is a bit bent but not broken and it's aluminum. It's a Cube SL bike. Thanks in advance!

picture with bent

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    Did you get the driver's insurance details? This looks pretty damaged, so the insurance (or the driver) should be responsible for at least a new frame. – anderas Nov 7 at 12:27
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    @Maco I'd also recommend removing the rear wheel and checking for a bent axle. The left dropout doesn't look straight. You might also have problems with the rear brake disk. I'd also be in the market for a new frame. – Andrew Henle Nov 7 at 14:34
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    I would 100% do a police report, to get a record of the event. Even if it leads to nothing then you have something to reference in the future if making a claim on your own insurance. – Criggie Nov 7 at 19:30
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    Frankly, I would attempt to straighten the stay. Even though bending it back weakens it further, removing the bow will reduce the flex that will cause more weakening as you ride it. I'm thinking place planks of wood on both sides and clamp, or some such. – Daniel R Hicks Nov 7 at 20:03
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    It's work-hardened now. I'd leave it alone and adjust the wheel if necessary. – Mazura Nov 9 at 19:39
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Safe - probably yes. Good idea - no.

As Argenti Apparatus stated, the bike should not fail without some warning, but it probably will fail sooner or later. As people noted in the comments - the geometry seems to have been changed - the wheel seems to be pointing slightly to right, the drop-out seems out of plane etc. The hub axle might be bent, also the bent drop-out may be causing extra stress on the bearing - in that case the rear hub will fail pretty soon. The bicycle will not ride straight now, and some parts will likely not work right and die much faster (shifting might be off similar to bent hanger, disc brake may act up if it is misaligned).

If you ask frame maker they will tell you the frame is busted and you have to exchange it. You could try to find someone who can bend the seat stay back into correct position and weld some piece of aluminum to strengthen the damaged part, but your mileage with this kind of hack repairs may vary. My biggest fear would be, that after some time riding new weakened areas might show up, requiring additional welding. If you want to go that way, you should find a good bike service and ask them for recommendations - often these places know of aluminum welders (at least here, in Poland).

Also - welding aluminum (requires TIG) could be expensive and it might be cheaper to find new frame and swap everything from the old bike to new. Winter is coming™, and so you can find good deals on new frames. Couple of suggestions.

https://www.bike-discount.de/en/shop/aluminium-8675/l-24

https://www.chainreactioncycles.com/brand-x-rd-01-road-frame-and-carbon-fork-2019/rp-prod130456 (be careful - I think there is no disc brake mount on this frame).

Note that whatever you decide to do, you should not use the bike much in the meantime - the components increased wear will add up to whatever you have to spend on repairs.

  • Thanks man. Is there any reason why you recommend Brand X? Never heard of it, and the price is surprisingly low. – Maco Nov 7 at 16:43
  • Unless you really want a specific frame I'd just find one secondhand, You can usually get a higher quality frame for a lower price. It will be a bit more work on your end though, so up to you whether time or money is more important to you. – Turksarama Nov 7 at 22:22
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    Brand-X is an in house brand of Chain Reaction Cycles. Usually this kind of in-house brands are OK, but I don't have any first hand experience. Recommendation was based on price. Also note, that this particular frame seems not to have disc brake mount. You would have to run rim brake back, ant that may require replacing the rim on the wheel. – Feldmarshall Nov 8 at 13:47
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Aluminum alloy is weakened by being bent. The seat-stay is bowed in so that loads will tend to bend the stay more. The stay probably will not fail suddenly, but it will develop a crack where it's bent if you keep riding it.

It's probably OK to ride on temporarily, even if the stay does fail the other stay will support the wheel.

You say the bike is a Cube so presumably you are in Europe. The driver's insurance will cover the damage done to the bike, or you can sue the driver in some sort of small-claims court.

  • Thank you. There's a lot to improve regarding car insurance and road control in Ireland. The guy was a member of an outsider community. They don't get licences or insurance and there's almost no control for that. There was no scenario for me where I could have it replaced. – Maco Nov 7 at 13:31
  • Regarding your comment, I'm mostly concerned about my own safety. You think this can affect the bicycle's performance or balance? Thanks again – Maco Nov 7 at 13:32
  • @Maco the rear triangle must be distorted a little. As I said, it’s probably ok to ride on but the frame will very likely crack. Inspect that area often. – Argenti Apparatus Nov 7 at 13:53
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    The stay probably will not fail suddenly IMO the real problem is that when it does fail, there's a really good chance it takes out the rear wheel - and if that happens at speed, an "adventurous rapid reduction in velocity" will likely occur... – Andrew Henle Nov 7 at 14:37
  • I think I agree with @AndrewHenle. I can't confidently say the stay won't fail suddenly. We can say that damaged carbon can appear fine and later fail unexpectedly, whereas metal frames or components will tend to show obvious cracks or other damage (e.g. above) before failing. The thinner that aluminum is, the quicker it should fail. If that's a lower end bike, it may still last a while, but I agree I wouldn't ride it as I couldn't predict when it would go. – Weiwen Ng Nov 7 at 16:51
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Further data - a change in geometry like that can screw up the handling something awful.

I rode this damaged steel-frame bike for a while:

Own work

That photo was before I straightened it somewhat with clamps and cold pressure. Being steel that was much more acceptable than your bike where straightening will weaken the metal further.

The bike was "okay" but always a bit odd on fast descents. In later rides I wore out the wheels, so fitted a used pair with different rim shape. Immediately the hill handling got horrible, to the point I wondered if my wheels were faulty. Inspection showed they were fine.

On a trip with another rider, he commented that my rear wheel looked "buckled" while descending. It turned out the seat stay was flexing more on one side than the other, making the dropouts move relative to each other.

This also backed off the cone nuts over time, which didn't help.

Upshot? Frame's toast and should be replaced for peace of mind.

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