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A few days ago I took a fall going down hill after hitting a large pothole. I fell on my right side, which if you didn't know is the side that contains the chain and gears on most bikes. Looking at my bike today, I noticed that when spinning the pedal the chain on the crankset makes contact with the shifter at a certain point in the rotation in both 3rd and second gear. furthermore when running the pedals in reverse the chain seems to slip at a certain spot.

So here's the question. I am having trouble identify the problem with my bike, I originally believed that it may be a bent crankset but due to the problem affecting multiple gears on my bike I am not sure that that is the case. The only other possible cause of the problem in my mind is a bent bottom bracket or frame and am hoping that you guys could walk me through identifying the problem and repairing it if possible.

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    Photos would help a lot - as a new user you can add two photos to your question with the Edit link. – Criggie Jun 6 '17 at 5:17
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    So recalling the fall - a bike on its right side generally will touch down on flat ground with the wheels, the right pedal, saddle and right end of handlebars. Can you describe if the chainring hit the ground ? – Criggie Jun 6 '17 at 5:19
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    Looking visually at the chainring, unhitch the chain and drop it off one side. Apply a straightedge across whereever you can and see if the chainring is bent. Then refit the chain and eyeball from above at the front derailleur. The cage part around the chain should be parallel to the chain, not slightly crooked. – Criggie Jun 6 '17 at 5:21
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    I would guess that the crank arm is bent. That causes the large sprocket to wobble back and forth. The chainring (that sprocket) would not normally hit the ground in a simple fall, and so would be unlikely to be bent on its own. But from the description of your symptoms, operation can likely be improved somewhat by adjusting the front derailer. – Daniel R Hicks Jun 6 '17 at 11:25
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    @Criggie I don't think the chainring actually made contact with the ground. But a few teeth are bent which I believe is likely due to the chain pulling the teeth. I'll try and upload some photos when I get home after school. But I think that the problem is likely either a bent frame or bottom bracket – Mohammad Ali Jun 6 '17 at 14:32
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I would start by trying to align the front derailleur. If the problem persists, drop your chain and check the chain rings to ensure they are straight and no teeth are bent. With your chain off, you can also check your bottom bracket/cranks. Make sure there is no wiggle in your cranks towards and away form your frame. This could be a sign of a few things. If the wobble is only on one crank, make sure it is tight. If the wobble goes through from one crank to another (if you pull the top of one crank away from your frame and the other moves towards your frame) you have more than likely blown up your bottom bracket.

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