How can you get out flat spots from a rim?

CRASH · Feb 25, 2016

I have a pretty rare rim. It's met a curb two or three times and lost. I don't want to lace it and find out that it has flat spots I can't true out. So...

How can I check for round?

How can I make it round again?

RustySprockets · Feb 26, 2016

You could secure the rim to a large, flat surface (like a big piece of cardboard) then run a length of string from the centerpoint to the edge. Mark the string then use it to check consistency around the entire perimeter and you'll soon know if it's out-of-round.

This is the "proper" antique tool for curing a flat spot. You're a resourceful fellow, so I'm confident you can rig a gizmo that achieves the same result. Clamping between two properly curved chunks of wood, maybe?

us56456712 · Feb 27, 2016

I rebuilt my friends 1957 Schwinn. It had a bad hop in the rear wheel. I took all the spokes out so I could submerge the Bendix 2 speed in auto trans fluid and acetone to free it up. After it was free I re laced the rim (had to start over as I started out 3 cross and found out it was 4 cross, dah). After it was re laced I trued it side to side as well as I could then loosened and removed some some of the spokes on the low side. I put a small 1 ton hydraulic jack between the hub and the low spot on the rim and cranked it up. This was a bad flat spot but by moving the jack around and putting soft wood on the rim I was able to remove it. Schwinn's had very heavy steel rims and that probably helped it spring back. Worth trying if you have or can borrow a small jack.

RustySprockets · Feb 27, 2016

Here's the "other" specialty tool that only removes flat spots on assembled wheels--same as us5646712 suggests.

This problem has haunted my thoughts for the past couple of days and I believe a straightening jig could be built using little more than scrap wood and a cheap Harbor Freight squeeze clamp. Let me know if you're interested and I'll draw up a diagram.

us56456712 · Feb 27, 2016

RustySprockets said:
Here's the "other" specialty tool that only removes flat spots on assembled wheels--same as us5646712 suggests.

This problem has haunted my thoughts for the past couple of days and I believe a straightening jig could be built using little more than scrap wood and a cheap Harbor Freight squeeze clamp. Let me know if you're interested and I'll draw up a diagram.

Draw it up if you have time, the jack worked well but perhaps you coul;d come up with a more controlled way.

RustySprockets · Feb 27, 2016

Okay...here's how I'd try it. Use some hardwood scraps to make a spine and two wedge-shaped chocks, then mount them to a small panel of plywood or masonite to create a rigid jig. Use a common quick-release squeeze clamp, Pony pipe clamp, or even a large C-clamp to apply gentle force where the arrows are pointing. Go slow and check your progress often. (A circle drawn on a large piece of cardboard provides an adequate standard.)

Depending on one's woodworking skill, the jig could be improved with curved, adjustable chocks and a matching wooden buck to protect the inner curve of the rim. But, what I've drawn here is probably enough to prove the concept.

If you build it, practice on a discarded rim FIRST! Just sayin'

us56456712 · Feb 27, 2016

RustySprockets said:
Okay...here's how I'd try it. Use some hardwood scraps to make a spine and two wedge-shaped chocks, then mount them to a small panel of plywood or masonite to create a rigid jig. Use a common quick-release squeeze clamp, Pony pipe clamp, or even a large C-clamp to apply gentle force where the arrows are pointing. Go slow and check your progress often. (A circle drawn on a large piece of cardboard provides an adequate standard.)

Depending on one's woodworking skill, the jig could be improved with curved, adjustable chocks and a matching wooden buck to protect the inner curve of the rim. But, what I've drawn here is probably enough to prove the concept.
View attachment 18437

If you build it, practice on a discarded rim FIRST! Just sayin'

I like it. I have a lot of hardwood flooring scrap. I think this is a better solution, thanks

CRASH · Mar 1, 2016

Fv2 · Mar 1, 2016

A new guy started at work and I just found out he has an extensive collection of bikes. So if you can't get this figured out @CRASH, I'll ask him if he has the proper rim.

Whether he's a willing seller or not I don't know yet.

How can you get out flat spots from a rim?

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How can you get out flat spots from a rim?

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