Crank type identification

[Namazu]

Hi, I'm new here so I'd like to start by saying hello and introducing myself, I'm John.

I restored my first MTB last year, a Giant Chicago. Recently the left crank arm started to loosen constantly and I guess, is damaged to the point where it won't stay tight for long. Being my first build and being somewhat of an amateur, I'm assuming I installed a crank type that was not compatible with the bottom bracket. I installed a JIS crankset and am wondering if my bottom bracket type is ISO? The square taper is 13mm at its narrowest and 14mm at its widest. I want to replace the crank/ crank arm but obviously do so correctly. Thanks!

 

[Double-E F]

Hi John,
Welcome to the site!
Do you have a pic of the crank arm too, especially of the part that goes onto the axle of the BB?
It could be that this part of the crank arm is worn.

 

[Namazu]

Hi John,
Welcome to the site!
Do you have a pic of the crank arm too, especially of the part that goes onto the axle of the BB?
It could be that this part of the crank arm is worn.

Thank you for the welcome and even more so for your response. The crank arm does have some visible damage and sits quite shallow on the BB.

 

[trailstar82]

Welcome in John, all I can say on the matter is “Let Sheldon guide you”
;-)

Square Taper Bottom Bracket Interchangeability

Dimensional standards for square-taper bicycle bottom-bracket spindles, and the limits of interchangeability among them.

www.sheldonbrown.com

 

[mdvineng]

There appears to be some surface galling on the axle. Clean thoroughly, including the arms then try again to the correct torque.

 

[Namazu]

There appears to be some surface galling on the axle. Clean thoroughly, including the arms then try again to the correct torque.

Thanks for the tip. Will clean it up and take a ride and see if it improves!

 

[Namazu]

Welcome in John, all I can say on the matter is “Let Sheldon guide you”
;-)

Square Taper Bottom Bracket Interchangeability

Dimensional standards for square-taper bicycle bottom-bracket spindles, and the limits of interchangeability among them.

www.sheldonbrown.com

I took a look at this article or one similar from him when deciding what crankset to purchase so thanks for sharing. Considering Giant produced in Asia it makes sense it's a J.I.S taper but it looks more like the ISO in the image hence my confusion

 

[trailstar82]

I took a look at this article or one similar from him when deciding what crankset to purchase so thanks for sharing. Considering Giant produced in Asia it makes sense it's a J.I.S taper but it looks more like the ISO in the image hence my confusion

Once the tapers are stretched, it’s only one way it can go sadly.

I would have said the same thing regarding the country of origin too. Have you removed the bottom bracket at all? Might be useful to know you can remove it if needed.

 

[Namazu]

Once the tapers are stretched, it’s only one way it can go sadly.

I would have said the same thing regarding the country of origin too. Have you removed the bottom bracket at all? Might be useful to know you can remove it if needed.

I tried to get it off with a friend but couldn't. Being an old bike it seemed to be seized. This is why I replaced just the crankset instead of upgrading the BB too. I though it'd be easier to keep but now I'm facing this issue.