Jicafold

So I have this rear wheel with a vintage Ambrosio rim in a laced with 36 butted spokes to a Suntour hub. Came on a used bike I bought. I have built a few wheels and trued many sets...however, I hate working with hops. So this wheel has a 3mm - 4mm hop spanning 2 or 3 spokes. It's looking too big to get out with spoke tension alone. So what other methods are there? I read elsewhere on the forum that I could loosen all the spokes and then hang the wheel over a beam or something at that spot and pull a bit to get it close. Are there any other methods for the home mechanic to true these larger hops? Thank you.

daverup 

I think the usual recommendation is to get a bike shop to straighten your rim with a proper tool. However, I have taken out flat spots with a strap and a vertical post. I loosened the spokes and strapped the rim at the flat spot to the post. This is described somewhere online, but I didn't find it.

Steelman54 

Is the hop at the joint or elsewhere. If at the joint, there may not be much you can do, although 3 or 4 mm seems like a lot to be out. Also, you suggest pulling on rim to get the hop out, is the hop on outside or is it a flat spot on pushed inside the OD. If a flat spot, Daverup's suggestion as has worked for me.

JohnDThompson 

There used to be a tool for this, the "Overland Rim-True." AFAIK, it's been out of production for a long time, but you may still be able to find one, or fabricate a functional copy:

Jicafold

That seems like a good idea. I was thinking of putting the low spot centered between 2 pieces of 2 x 4 on the ground and then using like a broomstick or something pressing outwards. But I don't want to dent it.

grizzly59

Aluminum is funny, everything looks good as you straighten whatever piece you're working with, then all of a sudden it just gives way permanently too far the other way. Steel is predictable, Al not so much. Confession of a ham-fisted halfwit.

Steelman54 

OK, so it is a flat spot, right. Daverup's suggestion seems good to me.

Yes, Aluminum does not have the ductility of steel, so you can move it only a bit before it cracks. Keep in mind, you may still be buying a new rim.

cjenrick

do people check rims for roundness before they lace them up?

Bill Kapaun

Is the "hop" directly across from the valve hole?
Often the joint has a flat spot.

deacon mark

I had a kinlin xc 279 that had hop was out maybe that far could feel in riding. Rim was rideable and worked fine but drive me nuts. I quit fighting bought new rim. Big out of round is hard to fix better to get another.