Chain Ring Wobble

[kscheel]

I am in the process of assembling my 1948 Roadmaster Luxury Liner and I'm finding that there is some troubling wobble in the chain ring. About 1/4 left to right movement.

I did remove the bearing cups when working on the frame, but they did not appear to be bent. Currently booth appear to be fully seated into the bottom bracket. How can you really tell though?

The bearings are original. When the wobble is occurring the bottom bracket is tight, no slop or looseness anywhere.

What's the deal here? Is the chain ring bent? If it's not the chain ring what could be the culprit?

Thanks

 

[B607]

Take off your chain and chain guard. Get a large Crescent wrench and adjust to thickness of chain ring. Rotate crank and bend ring where needed with wrench to make it straight. Bend it a small amount at a time, rotate and check. Gary

 

[Bicycle808]

Yep, like Gary said, but I want to really emphasize the small amount at a time part, as well as frequently checking your work. Too much enthusiasm, and you may do more harm than good. Patience, Grasshopper.

 

[kscheel]

As it turns out, the chain ring is fine. The problem is the bent crank. I've gotten the crank bent back and sure enough the wobble went away.

 

[B607]

Bending a crank back is difficult! I've never had any success at it. Make sure you check the crank for cracks where the bend was. Gary

 

[kscheel]

It was no easy chore and the bend was really more of a twist. The center forging line between the two arms had a pretty good curve in it rather than being straight. It took four sessions of trial and error with a big pipe and the bench vise. It isn't 100% perfect but it is close enough that it shouldn't cause any problems. It's definitely something I'm not looking forward to ever having to do again.