jyl

Another wheel truing topic. Sometimes I find a wide spot on a rim, where the rim touches both arms of the caliper (or both brake pads, if truing in the frame). Does anyone have a good technique for squeezing these wide spots to be the same width as the rest of the rim? Or do you use sandpaper to knock down the high spots?

Also, I usually attribute these wide spots to having hit a pothole etc with an underinflated tire. Myth? In the current situation, it is in a well used set of Mavic Open Pros, so I don't think it is just sloppy manufacture of a new rim.

The extra width is maybe a couple tenths of a mm.

dabac

My favourite approach is to cut a piece of wood to exact fit between the rim sidewalls, then use a wooden mallet to knock the flared-out section back in line. An alternate approach kinda-sorta requires three hands. I set adjustable wrenches to the width of the sidewall - not the rim, put one on each side of the bulge. Then, I bend the flared section in while holding the normal section in position.

Merely squeezing the flared spot inwards can cause the rim to undulate giving worse brake pulsing than before.

I wouldn't sand. Rim brake rims do wear out eventually anyhow. Unless it's a grabby seam or gouge, I wouldn't sand. Better keep the material for the pads to rub against.

FBinNY 

It depends on the nature of the problem but here's how I handle the dents and blips caused by the edge of a pothole.

I place a cone wrench (stiff flat piece of steel) against the good side to spread load, and use a pair of pump pliers (channellocks) to squeeze the dent back into line. If it's dented on two sides, I do one at a time.

This kind of work doesn't have to be perfect, brake track wear will finish the job, or you can touch up with a sanding block.

Andrew R Stewart 

The question I would ask the OP is whether the wide points snag on the brake pads during their use, can you feel it when stopping? If so then I'd try to squeeze in the wide points with a Bicycle Research rim blimp pliers. Or a pair of channel locks and a couple of strips of thin wood (popsicle sticks). If I don't feel the wide spots when stopping then I'd leave good enough alone. Andy.

cny-bikeman

I usually use FB's method, but you need to make sure that there is not also a flat spot where the problem occurs, especially if the rim sides are tapered in.

Jicafold

If you dont have the cash for specialty tools, you could simply use a C clamps to squeeze it out as well.

Bill Kapaun

Your problem is one that is missed by many people that use the brake pads or "one finger" truing stands.
I know it "bit" me when I tried that method on beat up wheels for my CL flippers, tightening one side and then the other until I had a horrible hop.
After I figured out what was happening, I now use an adjustable wrench as a makeshift caliper and slide it around used rims, checking to see if there are "wallowed out" spots.
I'll "fix" the worst of them with my anvil, 4 lb. hammer and various blocks of wood.

jyl

No, I don't actually feel the wide spots when braking. They just interfere with my ability to true the wheel to 0.00000001 mm :-)

Bill Kapaun

If you check out some of those $50 wheels found online, you'll find they can easily vary +/- .75mm.

FBinNY 

Then rule No. 17 applies. A "problem" that doesn't cause real world issues when riding isn't a problem.

In your case, if the brakes don't pulse, the rim doesn't have bulges.

However, many rims aren't uniformly wide. Distortion at the joint, or the effects of hard use can cause local bulging. The extent of the bulge determines the limits of what you can do. BITD, light rims always had distortion at the joint. A wheel was considered true if the rim joint was the worst problem.

fietsbob

thats more Porsche engine level Of German tolerances to sweat, not so big a deal in bike wheel rims.

miamijim

I clamp them in a bench vice...