TexasLonghorns

Hi guys. I'm now starting to learn about self bicycle repairs. I have a quick question:

I currently have MTB Crank that's 22/32/42.
Can I replace the crank with 24/34/42.

I have a old beat-up Callas MTB so I'm refurbishing it with cheap parts since bicycle is old.
Thanks.

TexasLonghorns

Hi guys. I'm now starting to learn about self bicycle repairs. I have a quick question:

I currently have MTB Crank that's 22/32/42.
Can I replace the crank with 24/34/42.

I have a old beat-up Callas MTB so I'm refurbishing it with cheap parts since bicycle is old.
Thanks.

veganbikes

What is wrong with the current crank? You could replace but it depends on the bottom bracket needed so that might also need replacement and then some adjustment of the gear and I would probably also replace chain and cassette.

If it is the Callas from South Korea, I wouldn't put much time or especially money towards it, if it is something nicer than you could but first figure out what is wrong with the current cranks. A two teeth difference for two chainrings on a triple isn't a huge enough need to swap over at least not for me.

TexasLonghorns

Thanks for your reply. Current crank is rusted but still works. I'm currently station in Seoul South Korea at Camp Humprey's (US Army Base) so buying parts here isn't that simple. Mostly over-sea's shipping so I could only find 24/34/42 local shopping. Since it's a cheap bike, your right, not worth the money to buy all new matching expensive parts.
So the two teeth difference shouldn't be a problem once I order the new parts right? Problem meaning when I change gears, etc. I'm newbie to fixing up the bike & since its a cheap bike, not worth to take it to bicycle store since they over-charge.

Thanks again for the helpful info!

79pmooney

First question - are you swapping the whole crankset or just the two inner chainrings? If whole crankset do you know if the crankest you are looking at fits on the bottom bracket you have and in the same location; ie distance out from the bike frame? If you don't know, you are asking for a lot of extra work, quite possibly another bottom bracket. If you are just going to change the two chainrings, are the replacements identical with regard to the mounting holes.

The risk of cheap bikes is that they may well not be made to common standards. Going deep into modifying one to be the ride you want may be going into a very frustrating ordeal. Most there would say stay away from bikes that are not equipped by Shimano's Sora or MTB equivalent or better.

TexasLonghorns

Oh wow lol. I am just replacing the whole crankset since I don't know how to replace just the inner chainrings & the crankset seems rusted all around. And the whole crankset is only like $20 bucks. Is there a way I can tell if the bottom brackets fits the new 24/34/42 crankset? I googled but can't really figure out how. If I was back home in Texas, I would just go to local bicycle shop to ask questions but here in South Korea - nobody really speaks English at local bicycle store.

Thanks for the helpful info as I'm a complete newbie regarding how to fix bicycles, just watching from YouTube lol

SpedFast

The last time I swapped a crank set on a cheap bike they were square taper cranks and all I had to do was pull them off with a crank puller and put the larger cranks on and then swap my pedals. If your bike has square taper cranks you're in luck. If not, you might be opening a can of worms, especially if you're looking at one piece crank set. For the few tooth difference that you're considering you should get away with the same chain or at least the same length chain. Your stationed on an army post so I'm assuming this bike is just to get you around. Good luck and thank you for your service. Oh, welcome to the forums also. Are you sure you can't just remove the rust and use as is?

TexasLonghorns

Yeap its square taper cranks & same here, just replacing the cranks, cassettes & pedals only. Walking around military post & nearby Seoul area is the main use of the bicycle. I tried removing the rust from the cranks inner chainring but its an old 2017 MTB I bought off Craigslist for like $40 bucks so it has many rust on the bike.

Thanks & much appreciated for all the helpful info.

Arrowana

A quick search for Callas bikes only showed models that have square taper cranksets, so I am going to assume yours is as well.

If you have a crank puller, you can remove your current crankset, then you can measure the length of the bottom bracket spindle. If your crank arms are held on by bolts that thread into the spindle, simply measuring how long it is in millimeters will give you the length. If your spindle has threads that stick out and the crank arms are held on by a nut, then you don't include the threads when measuring the length. You should be looking for a number between 103mm and 127mm. Once you know how long it is, then you want to find a crankset that uses the same length of spindle. If the maker of the crankset has a website, that would be the best place to look. On a low cost bike like yours, you might be able to get away with a slight mismatch, if your new crankset is designed for a spindle that is <5mm shorter or longer than your current one, you might be able to make it work. Past 5mm, you are likely to run into issues like chainrings hitting the frame if it is too short, or chainline issues if it is too long.

If the crankset and cassette or freewheel are in need of replacement, you should grab a new chain as well. A worn chain on new chainrings and cogs will likely skip, and will wear down your new parts quickly.

veganbikes

I would get involved with the forums and then post photos once you get 10 posts that way we can see how bad it is. A little surface rust isn't so bad and can generally be cleaned or will be taken care of with a properly lubricated chain and some riding at least enough to not be a bother.

The big issue with replacing is knowing what crank you have and what crank you are replacing to as square taper cranks require different bottom brackets and there are of course some overlaps but we would need to know what you have and what you are getting. If the new crank is not square taper then you would need the proper bottom bracket for that crank but I have a feeling both are probably square taper. Shimano has tech docs for all their products going back a ways so you can get the info you will just be looking for an FC-______ mark on your cranks and then you can search that at si.shimano.com and that will get you set up.

Iride01 

This is the description for the subforum you are in...
Don't worry though you are in good company. This happens often enough with new members. And I too think the way they named the subforum is ambiguous. Especially for those of us that sail or are involved in the boating industry as fitting a boat means to install equipment, rigging and sails on it.

If they only would add the words "you to" and make it "Fitting You To Your Bike" then maybe it'd be more clear to noobs.

But to answer your question, you probably can if you can find that ring combo and the crank is the same BB or has a BB made to fit the BB shell of your bike. You also might just be able to change out the rings.

But the question is very much more suited for the Bicycle Mechanics subforum. Quite a few of the real bike mechanics and avid DIY'ers that might give you all sorts of varied thoughts and opinions don't ever come to this subforum.

You might can just press that red button with the exclamation mark and ask a moderator to move the thread for you. Even though it's not one of the things they say it should be used for, they have said in the past that they don't mind. Unless they are fighting a bunch of SPAM, things are generally slow for them... I think.

Welcome to BF!

cb400bill

Duplicate threads merged. Please do not cross post. Once is enough.

TexasLonghorns

Ah yes thank you. I first posted in the wrong section but there was no option to delete the original post. Maybe I couldn't find the option to delete that post but anyhow, thank you merging that thread.