Crank arm hitting the rear stay

[cwah]

Hello,

My bike crank worned out and I decided to buy a new one from Amazon:
http://www.amazon.co.uk/Cotterless-Steel-Crank-170MM-Black/dp/B0044RGEHS/ref=sr_1_2?ie=UTF8&qid=1434220493&sr=8-2&keywords=bike+left+crank

Once installed, I realised it touched the rear stay:

I initially decided to install it a bit more loose, but after a fall it resulted in a bent I think and now it is always touching it...

What's the best approach for me? the arm is steel, maybe I can hammer it right?

 

[selrahc1992]

Hello,

My bike crank worned out and I decided to buy a new one from Amazon:
http://www.amazon.co.uk/Cotterless-Steel-Crank-170MM-Black/dp/B0044RGEHS/ref=sr_1_2?ie=UTF8&qid=1434220493&sr=8-2&keywords=bike+left+crank

Once installed, I realised it touched the rear stay:

I initially decided to install it a bit more loose, but after a fall it resulted in a bent I think and now it is always touching it...

What's the best approach for me? the arm is steel, maybe I can hammer it right?

Just a thought,but could you have installedvitcwrong way round? I've done that before. Your crank end seems to protrude a lot and there's a distinct curve to the arm which may swing out other way round.

 

[SRS]

If it did not fit when new the you need one with more offset.

You cannot install loose as the thing sits on a taper and has to be fully home.

Bending it is not the answer either as the pedal axle would then be p*ssed.

Get to the bike shop and they'll sell you one that will fit.

 

[cwah]

I had a small hope that this could be the case and tried it but it doesn't seem to be the case :/

Before:

After:

And I can't put it the wrong way around on the pedal side:

 

[Cyclezee]

Hi cwah,

How exactly was your old crank arm worn out? If fitted correctly there is nothing that can wear.
The new one you fitted is the right way round, but clearly not the same pattern as the old one which did not hit the stay.

 

[cwah]

The thing is it was working well before I felt. So it must have been bent somewhere, somehow. But I can't see where

 

[cwah]

Hi cwah,

How exactly was your old crank arm worn out? If fitted correctly there is nothing that can wear.
The new one you fitted is the right way round, but clearly not the same pattern as the old one which did not hit the stay.

The thread to fit the pedal was worn. So pedal was getting loose as I was cycling and nothing I can do to tighten it up as thread was gone.
No other choice than buying a new one


As said, I think it may have been bent from my fall because it was working before, although I didn't tighten it completely..

 

[Cyclezee]

That would be it then, the crank arm must have bent when it fell.

Sorry, but you need a new crank arm as you would need to be Hercules to straighten the bent one.

 

[cwah]

What about hammer it straight? Maybe that could be done?

 

[trex]

you can try but if you don't get it right, it'll make your pedal wonky.

 

[Cyclezee]

What about hammer it straight? Maybe that could be done?

If it is only a mm or two and it is securely clamped in a vice maybe.

 

[cwah]

It's closer to 1cm than 1 mm... my main concern is that I'm not sure if the problem is with the crank arm, or if it's with the bottom bracket.

If I change the arm and I have the same issue it means the bottom bracket needs changing...

But trying to bent it back may cost me nothing and just fix it?

 

[trex]

if the pedals were right before and are still straight, you have not bent the crank arms during the fall. The solution then is to get a bottom bracket with a longer spindle. Take your BB out and measure it. Yours looks like 68mm x 110mm. Then get one longer, like 68mm x 122mm. The new BB has better ball bearings than your old one.

http://www.chainreactioncycles.com/shimano-un55-square-taper-bottom-bracket/rp-prod71369

 

[Deleted member 4366]

It's aluminium, not steel. You can bend it easily in a vice, but you have to heat it up to red hot first. You don't have to bend it while it's hot. When you try and bend it (after heating), it will move a little bit, then stop. You then have to heat it up to red hot again and you can bend it a bit more. Don't bend it more than you need to otherwise the pedal axle will be at the wrong angle, which will make the pedal feel wobbly when you pedal.

 

[cwah]

if the pedals were right before and are still straight, you have not bent the crank arms during the fall. The solution then is to get a bottom bracket with a longer spindle. Take your BB out and measure it. Yours looks like 68mm x 110mm. Then get one longer, like 68mm x 122mm. The new BB has better ball bearings than your old one.

http://www.chainreactioncycles.com/shimano-un55-square-taper-bottom-bracket/rp-prod71369

Excellent idea! Will do

 

[cwah]

It's aluminium, not steel. You can bend it easily in a vice, but you have to heat it up to red hot first. You don't have to bend it while it's hot. When you try and bend it (after heating), it will move a little bit, then stop. You then have to heat it up to red hot again and you can bend it a bit more. Don't bend it more than you need to otherwise the pedal axle will be at the wrong angle, which will make the pedal feel wobbly when you pedal.

On amazon it says steel. I should test it with a magnet.

I only have a small soldering torch:
http://www.amazon.co.uk/gp/aw/d/B004CLA01W/ref=mp_s_a_1_8?qid=1434227265&sr=8-8&pi=AC_SX110_SY165&keywords=soldering+torch&dpPl=1&dpID=41xXDxEx0HL&ref=plSrch

Because I have such limited space I can't afford to get bigger tools.

Would that be enough to make it red hot?

 

[Deleted member 4366]

No.

 

[selrahc1992]

On amazon it says steel. I should test it with a magnet.

I only have a small soldering torch:
http://www.amazon.co.uk/gp/aw/d/B004CLA01W/ref=mp_s_a_1_8?qid=1434227265&sr=8-8&pi=AC_SX110_SY165&keywords=soldering+torch&dpPl=1&dpID=41xXDxEx0HL&ref=plSrch

Because I have such limited space I can't afford to get bigger tools.

Would that be enough to make it red hot?

This thread is beginning to give "touching the void" a run for it's money, if I were in your shoes I'd just buy a new bb and crankarms on fleabay,its dirtcheap and easy to install. I'm not an engineer but the idea of jumping around on an ally crank i ve bent and heated would give me the heebyjeebies

 

[Kuorider]

Cwah, Please stop wasting your money and time ,get yourself and your bike to a proper bike shop and the man there will fix this in no time. Your talents lie elsewhere. Effort without knowledge is of no avail.

 

[the_killjoy]

How about a picture of the old and new cranks for comparison.