lectraplayer

After having my last bike stolen out of the back of my truck one day, I promptly bought me a replacement for the same price as the hot bike (all of $30), and it's a nicer bike. However, it uses linear pull brakes, which seem to be more succeptable to bent rims. The rims on this bike are not bad, but do interfere with the brakes, making the bike stiff when I adjust the brakes in, or a correct ride with the brakes just bottoming when they make contact. What is the best way to make the minor tweaks to my rim to get it arrow straight, or at least to where the brakes can be used like I like them--within tight tolerances?

brandonsdad02

Find the bent spot in the rim and on the opposite side of the bend, turn the spoke about a quarter turn. Keep doing this all the way around til the rim is straight as you can get it. I have had luck with my rims by doing this.

Mentor58

The thing that will get you is that you actually turn the spoke wrench OPPOSITE to what your common sense tells you. Turning it to the right (what you usually think of as TIGHTENING) actually loosens the spoke, moving the rim AWAY from that side. Turning Left (Counter-Clockwise) actually tightens the spoke, pulling the rim TOWARD that side. It's because you're not actually turning the spoke, you are turning the nipple, so it's backward from what your mechanical brain tells you. After you mess it up once or twice (or in my case a few extra times) it will become ingrained

Do it in little bits, take your time, and you will be surprised at how true you can get the wheel in just a few minutes.

M58

lectraplayer

My problem isn't radial, but in a side to side direction. Will adjusting the spokes help this? (I don't think so)

R88

yes this will adjust side to side. It also adjusts radially but if you keep it to small adjustments you shouldn't have a problem with the radial adjustments getting out of hand. Just give it try, if you keep it to quarter turns you can always go back and undo what you've done.

Mentor58

It sure will... If you tighten the spokes on BOTH sides of the rim, it will pull it in toward the hub, Loosen the spokes on both sides it will move it away from the hub (ok, technically it allows the rim the lose some tension and move out, but hey, we're friends here)

If you TIGHTEN the spokes on ONE side side of the rim, and loosen their partners on the other side, the rim will move Laterally (Side to Side). If you image the spokes as ropes, with the rim tied to each of them, what you are in effect doing is feeding out a little rope from one side, and the other team (spokes) is pulling in a little rope. Whatever is attached to the rope moves along left or right.

Give it a try, just do a 1/4 turn on each side, and see the difference. As you get closer, it's usually just a little 'tich' of a turn to make it just right.

Hope this clarifies it for ya.

M58

lectraplayer

Appreciate it. I guess I'll need to get me a spoke wrench then. How would be the best way to approach this? Start from the center of the wobble and go out, matching tension across the diameter of the rim?

bubbagrannygear

Think of the nipples as nuts on a bolt with the spoke being the bolt. You want to tighten the nipples on the side of the rim that you want to move the rim toward, and loosen the nipples the same amount on the side of the rim that you want to move away from. Read what Sheldon has to say - https://sheldonbrown.com/gloss_tp-z.html#true

zacster

Yes, start at the center, and do turn the most at the center and slightly less as you move away. I always used the tighten one side, loosen the other method.

Mentor58

I usually do this, find the worst place on the rim (you can do this watching it move in and out in relation to the brake pads. Next I will usually adjust the pair of spokes at the worst point in the warp by about a 1/4 turn (turning one in, the other out to move the rim side to side), then the pairs of spokes just to their left and right each get about an 1/8 turn or so. This helps ease the rim into true. Then I spin it back and forth a few times, see if I need anymore adjustments on that spot. (with practice you get pretty good at getting it about right the first time). One thing that you may find helpful, on the spokes that your are making tighter, overturn them just a bit (maybe an 1/8th turn or so), then back them off that extra amount you put in. This helps eliminate any 'twist' that can form in the spoke, helps them hold their adjustment.

Spin the wheel again, watch for the next worst spot, correct that, repeat as needed. Don't worry at this point about getting it 100 percent dead true, just get it within a couple of MMs or two and you'll be fine.

M58

StephenH

When I bought a spoke wrench, I discovered they make different sizes. Take a wheel with you if in doubt!

blamp28

I always start one spoke beyond the defect on each side and make smaller adgustments to those spokes.

BarracksSi

Or think of it like you're putting a screwdriver through the tire into the end of the nipple, then habitually go "righty-tighty lefty-loosey". If the nipple is at the hub, put the imaginary screwdriver through the hub.

It took me some mental gymnastics to figure it out so that it's simpler for me to remember. Clockwise vs. counterclockwise changes (at least to me) depending on if the nipple is facing me or if it's on the far side of the wheel. The comment about thinking of the nipple as a nut is a good one, too.

Now -- who wants to talk about dishing?

lectraplayer

You can do that or you can do as I done, I bought a universal wrench today. Here in a few minutes, I intend to try it out.

Also, I guess we can discuss dishing if it's on topic with my bent rims. I'd kinda like to know what it is now.

dabac

If you look at a wheel you'll notice that the spokes aren't exactly flat, but sloping from the rim towards the hub, like a very shallow cone. This cone shape is what's referred to as dish. Main issue and reason to discuss dish are rear wheels with derailer gears. Because of the sprockets all stuck on one side the dish is different too, which makes for uneven spoke tension and a bunch of unhappy compromises.
Disc brake wheels are also unevenly dished, bu that difference is so small that it doesn't really mean anything.

lectraplayer

OK, I knew the spokes went at an angle as they go in toward the hub, but didn't know what it was called. Now I know. I'd even bet just about anything that the dishing would work to my advantage in this little project.

flanso 

I made a cradle for a Sharpie marker and clamped it to the fork so that it pointed to the center of the portion of the rim that was swept by the brake pad. I adjusted the pen so it barely cleared the "good" portion of the rim. When I spun the wheel, the Sharpie left a mark on the rim where it was "high." I adjusted spokes on the marked portion of the rim starting with one spoke before the mark and going through one spoke after the mark. Primitive, but it got me back on the road.

BarracksSi

You can see really pronounced dish on the rear wheel of most bikes. The axle ends are equally spaced from the centerline of the tire, but the hub flange on the drive side is farther inboard to make room for the gear cluster. The center between the hub's left & right spoke flanges is offset from the centerline of the complete wheel. That means that the spokes on the drive side have to go at a straighter angle, and a slightly shorter distance, to meet the rim than the spokes on the non-drive side.

BarracksSi

Oh, cool; I hadn't thought to do that.

airosen

Only on BF.

lectraplayer

Thanks guys, this technique helped quite a bit. While my rim isn't straight yet, it's a lot straighter than it was, to the point to where my brakes work fairly well without having to have massive amounts of play. I'll continue to tweak it for some time, but it's got me riding happily again.