Crank arm hitting frame

[BSA]

Recently my bike has developed a click once per rotation. I initially thought the BB was loose but it wasn't. Turns out to be my left crank arm has started to catch the frame. The back of the pedal catches the bit of the frame between th BB and back wheel.

Why would this start happening? Have I bent something (I cant see anything obvious) or can you adjust this somehow?

Any help greatfully appreciated

 

[NickM]

What sort of bottom bracket is it?

It sounds as though the crank has been ridden while loose on a square taper bottom bracket axle, deforming it until, when tightened, it pulls on too far. Either that, or the (square taper) bottom bracket fitted is simply too short.

 

[tyred]

If the bottom bracket is tight, it would almost have to be a loose crank. Is this the bike with the cottered cranks you were going to replace the BB on or have I mixed you up with someone else?

 

[BSA]

If the bottom bracket is tight, it would almost have to be a loose crank. Is this the bike with the cottered cranks you were going to replace the BB on or have I mixed you up with someone else?

It is the one and the same. The BB doesnt seem too bad but I did remove the cottered crank to try and tighten the bottom bracket previously. The click started before I removed the crank though but it has defintely got worse since. I will try and tighen it tonight to see if it makes a difference.

 

[tyred]

Is the cotter pin tight? I wouldn't have thought it would allow much lateral movement even if it wasn't. Tighten the nut, hit the other side with a hammer to drive it in further, tighten the nut again, hit with hammer again, reapeat until it stops coming loose when hit with the hammer.

I just realise you say it's the back of the pedal that's catching. Have you changed pedals recently? If the pedal threads are out past the crank arm, remove the pedal and fit a 9/16" washer between the pedal and the crank.

 

[BSA]

Is the cotter pin tight? I wouldn't have thought it would allow much lateral movement even if it wasn't. Tighten the nut, hit the other side with a hammer to drive it in further, tighten the nut again, hit with hammer again, reapeat until it stops coming loose when hit with the hammer.

I just realise you say it's the back of the pedal that's catching. Have you changed pedals recently? If the pedal threads are out past the crank arm, remove the pedal and fit a 9/16" washer between the pedal and the crank.

Just a quick update on my old bike.

Sorry for the delay, I havent had chance to take the bike out until today! I tried tightening the crank arm and it appeared to tighten a little. I took the bike for a spin and it seemed good.

This morning I set off for work and after the first mile "click click" the problem is back!

I will try to tighten again when I get home and see what happens, although im not convinved it will work.

 

[Steve Austin]

If its clonking the frame every revolution, I wouldn't be riding it. Its amazing how quickly a hole can be 'worn' through a frame with abrasion. Even a tyre rubbing will wear through a frame given time.

 

[zacklaws]

I had this problem on my old "racer" back in the 70's and it was caused by me falling off badly and putting a slight bend in the crank. And has been mentioned previously take heed, I did not take much notice to it till the day my bike became a bit wobbly and when I looked the crank had worn right through the frame making my wheel move in the remaining stays and the frame US.

 

[BSA]

If its clonking the frame every revolution, I wouldn't be riding it. Its amazing how quickly a hole can be 'worn' through a frame with abrasion. Even a tyre rubbing will wear through a frame given time.

I had a good look at the frame and you are right is wearing the frame quickly, so I will stop riding for now.

Im at a cross roads now because I think I need to replace bb and i would like to put cotterless cranks on but Im worried the cost wont be worth it. Should I look for another bike i wonder?

 

[tyred]

Is the threaded part of the pedal axle sticking out behind the crank?

 

[BSA]

Is the threaded part of the pedal axle sticking out behind the crank?

No its the actual crank that is hitting the frame. I did come off the bike in the winter and I wonder if i have bent something.

Is it worth giving thr crank a tap to see if I can bend it away from the frame slightly?