What type of axle is this/What crankset do I need?

[harrymfb]

Trying to replace the crankset on an old mountain bike but not sure what will fit on the axle. Anyone able to help?

 

[Chris S]

It looks like a square taper. If your bike has Asian components then it will use the JIS but an ISO crank will probably work OK as well.
Scroll down to ISO/J.I.S. Interchangeability
https://www.sheldonbrown.com/bbtaper.html

 

[Ajax Bay]

Unless you are competent and confident to service the BB (after all these years with no love), I'd replace it with a UN-55 and all the old/used MTB cranksets with square taper will fit.

 

[harrymfb]

Unless you are competent and confident to service the BB (after all these years with no love), I'd replace it with a UN-55 and all the old/used MTB cranksets with square taper will fit.

Thanks for that, was thinking that might be best. Any idea how to remove the old one - any 'special' tools required?

 

[C R]

Unless you are competent and confident to service the BB (after all these years with no love), I'd replace it with a UN-55 and all the old/used MTB cranksets with square taper will fit.

Removing the fixed cup might not be straight forward, so it might be worth finding a bike mechanic to do the swap.

 

[Sharky]

Can I ask, what are your reasons for changing the crankset?
If planning to go down the DIY route, you'll have to remove pedals, remove the bottom bracket if needed etc and all need special tools. So it might work out dearer than you think.
Unless there is something specifically wrong with the crank set, perhaps start with a good clean, replace the chain first. See how it gets on with the cassette, then change the cassette. Next would be the brake/gear cables that might need attention or replacement.

Will be a nice project and good learning, but for some jobs, going to the LBS could be cheaper if you have to buy tools that you might not need again.
Good luck