One Piece Cranks

[SirMike1983]

Are all 24 tpi one piece cranks the compatible? I've been trying to find a one piece crank to fit right into my Columbia balloon tire; where do you guys get cranks when the ones you have are bent?

 

[SirMike1983]

Also I'm curious about this- are the bottom bracket cups removable on a balloon tire bicycle usually or not? I've never tried putting new ones in, but the suggestions I've heard is that if you replace the crank set you want to replace the cups too. If so, how do you remove them?

 

[rjs5700]

Unless the cups are worn bad I wouldn't replace them. If you decide to just take an old screwdriver and hammer and knock them out from the inside. They are like headset cups and just pressed in.

 

[37fleetwood]

this is a great question and there are several aspects to it. first not all are 24tpi. I havent quite nailed it down yet but there are definitely a couple thread pitches. next most makers had their own cranks and they vary in design a bit though they are all basically the same size. if you want to be correct you should track down a Columbia crank, if not any will likely do. there are different arm lengths though. next is that if you are using skip tooth sprockets there is no washer between the sprocket and the race, if you are using a 1/2" pitch chain there should be a washer there. if you don't put the washer in you will have clearance problems with the sprocket. and the cups are as stated by John just pressed in very like a head set race. if you go to the local bike shop and get a bottom bracket kit it will come with the cups and while you are there and if you ride much nice new cups make a difference so I change them. also what you are looking for at the bike shop is a bottom bracket for one piece cranks, and should be the same as a BMX bike. finally ebay or here are great resources for a crank.
Scott

 

[Parker]

A lot of the columbias had cups that had no outer flared edge, most new cups do have the flared edge. that makes it easier to install, but might mess with clearance of the covers. I think there are 26 TPI cranks out there. Then there are 9/16" and 1/2" pedal holes.

 

[SirMike1983]

Interesting-- I've got a bottom bracket kit I've been working with. The only thing I haven't replaced at this point are the cups (I couldn't seem to get them to move ever with hammer and screw driver, though I'll admit I didn't give them a really hard whack either). I'd been trying to mix and match crank set parts in order to get the original look (double dust cap) but with new innards. What I kept noticing was sort of a cyclic "hiccup"-- when the right arm would get near the bottom of its travel I'd feel just a little "bump" with my feet. I figured the source was mixing and matching the parts, so now I've gone over completely to the new set, except for the cups.

When you say there should be a washer between the sprocket and the races, you mean I take the washer that came with the kit and: slide the sprocket onto the crank, then slide the washer over that and then tighten the cone down on top of that, then put the bearings on top of that and slide it into the bottom bracket? When you talk about "clearance" issues, do you mean that the sprocket will catch on the frame or bottom bracket? I installed it without the washer in this last attempt, though using the washer left the chain line looking a bit weird.

The equipment I'm using is this "tange" bottom bracket kit that I got from a bicycle shop. It seems to be quite generic, though the parts seem generally to match what the original stuff was.

 

[Parker]

On mine right to left it goes:
crank-sprocket-cover-cone-bearing-cup-frame-cup-bearing-cone-cover with alignment tooth-washer with tooth-nut

do you feel the bump in both feet or just one. Most likely a pedal if only felt in one foot