Comments on Using Rubber Shims on Rag Washers

[Russ McClay]

Hi - Just built my first motorized bicycle. Standard 66cc "China Girl" motor bolted onto an old no-name mountain bike frame. I've already put about 5 miles on it, but I've got problems with the rear sprocket alignment. No matter how much I've tightened and loosened and tightened the bolts (9) I can't get the slight wobble out of it and today I saw why: one of the rag washers has a thick side. I have this one on the inside of the sprocket. Sprocket > washer-in-question > spokes > inside washer > the 3 plate brackets.

I was thinking I could cut up some strips of inner tubes or similar rubber and put pieces of them over three or four of the bolts in between the sprocket on the low side and the first washer to try to even things out. What do you think?

(Btw I am an American who lives in Taiwan, have no garage and only some basic tools, and don't have access to buying stuff cheaply from places like Bikeberry, Walmart...or other American stores...and it's just plain difficult to find anything DIY here.)

Thanks.

[maniac57]

Place the uneven rubber inside the rim and away from the sprocket so it sits flat, But spacers should help if thats the only way. You could also try cutting your own from old tires or something. A hole punch set is fairly cheap or you can make one from a sharpened bit of tubing. Even in the wilds this should be practical.

[bigbutterbean]

I would also suggest that perhaps you could file the thick spots flat on your rag mounts. If at all possible, I would look into getting a sprocket adapter like this one: http://www.piratecycles1.com/picycbspad.html This will eliminate the rag mount altogether, as well as eliminate the stress on the spokes and virtually guarantee a true sprocket mount.

[Russ McClay]

Originally Posted by maniac57

Place the uneven rubber inside the rim and away from the sprocket so it sits flat, But spacers should help if thats the only way. You could also try cutting your own from old tires or something. A hole punch set is fairly cheap or you can make one from a sharpened bit of tubing. Even in the wilds this should be practical.

Thanks maniac for the reply. I disassembled the rear sprocket and moved the inside rubber to the outside under the sprocket and then cut out a piece of inner double thickness to put under the inside rubber where it was thin (about a quarter of the disk). Then re-assembled and finally got it true! But then I saw I needed to flip the sprocket! Oh well, an hour and a half later it was done...and it is so great now! Took it for ten mile ride mostly uphill, no problems at all.

Chain/sprocket alignment has to be the most critical part of these motorized bikes.

[maniac57]

Originally Posted by Russ McClay

Thanks maniac for the reply. I disassembled the rear sprocket and moved the inside rubber to the outside under the sprocket and then cut out a piece of inner double thickness to put under the inside rubber where it was thin (about a quarter of the disk). Then re-assembled and finally got it true! But then I saw I needed to flip the sprocket! Oh well, an hour and a half later it was done...and it is so great now! Took it for ten mile ride mostly uphill, no problems at all.

Chain/sprocket alignment has to be the most critical part of these motorized bikes.

Great job! I agree with the chain being important to reliable service. I replace the stock junk chain and I have no issues at all.