I bought an old Subrosa Tiro and overhauled it, repainted it, and wanted to put on a sprocket from this century. But when I was taking the bike apart, the previous owner had welded the crank arm to the crank arm.
I broke it off and there was a 1/2″ nub there, so I hack sawed that off and I’m left with this. I was thinking of drilling a new hole and tapping it (I have a tap and dye set I’ve used like…once) but then I thought it might be really difficult to get it perfectly level with the sprocket attached, and I don’t have a drill press.
This is a bike I’m gonna sell for under $200 CAD so I’m not keen on buying new crank arms. I tried fitting the cranks from the basketcase FB Marketplace bike but it’s too big. The spindle seems to be 20mm which tapers at the splines. The crank arms also don’t swap over because the spline shape is square VS the rounded ones on the Subrusa spindle.
Would you take a chance and try to drill this shit out since it’s basically fucked anyway? Will I need some kind of washer/spacer between the arm and the sprocket?
by o2G2o
9 Comments
“…had welded the crank arm to the **sprocket**.”
(Can you really not edit posts in here?)
Does the other crank have a sprocket hole? The easiest fix would be to swap the drive side. Provided you have a wheel to do that, you could also flip the pawls on your current hub if you wanted to get really ghetto
Drill & tap… you can add washers to offset any difference in the mounting plane
Drill an re-tap
That’s a cheap crankset with a stud instead of a threaded hole. The sproket just weebo wobbles with those. The welding was 100% a “Dad fix” to keep the chain tension consistent.
Shave more off, get a good bolt from the hardware store. Make a jig out of scrap to hold the new “stud” in place and carefully mig weld it on. + it has threads so you can clamp the sproket with a nut. Grind the excess to prevent interference with the frame.
Re weld it if you got a welder if not tap it but don’t use zip ties they don’t work…at least for a long time
New Cranks!
You could use and extractor or you could weld a bolt onto it to get the bolt out. Both methods work and require special tools.
Mission cranks are like 40 bucks at Dan’s comp
https://www.danscomp.com/mission-transit-v2-cranks-black-170mm-mn5701blk/p1132563