Aldo Ross wrote:
> What are the repair options for a bottom bracket shell which
> has become slightly oversized and ovalized. It's not
> unusable, but the bottom bracket cups do not fit very
> securely. The bike, a '52 Learco Guerra, is otherwise in
> good mechanical condition and my favorite vintage ride.
> Thanks for any advice or suggestions.
Mark Bulgier replied:
>Method One is to simply hammer the shell back to round - this can bring the diameter back down too, but not much, it's mostly to fix an out-of-round condition. The side opposite where you're hammering should be supported by a V- or half-round block. The hammer can be a hard-plastic-faced mallet (the steel of the BB shell is rather soft), but a rubber mallet probably won't do. Many blows around the circumference will be needed as you slowly blacksmith it back to shape. Sometimes squeezing in a vise helps if the main problem is ovalization. This is all done cold, by the way. It will damage the paint, probably flaking it all off in the hammered area. You will almost certainly need to chase the threads after, with a BB tap.<
Aldo and Mark, I have successfully used Mark's method a number of times. Since the races will thread in, another variation is to install the races (without the axle and bearings) and tap with the hammer while supporting the shell on a V-block. The bb shell is softer than the races, and this may help the situation by forming the bb shell steel around and into the race threads. It wouldn't hurt to use a spare set of races just in case, and slow and easy are the key words here.