TwoFourOne

Alex ID19 rims, 32-spokes (F & R), Formula quick-release hubs

Long story short, my friend crashed my bike and untrued my rear wheel. I fixed it up as much as I could and let it be. It kept getting more and more out of true over time, and I realized that the rim is probably bent. The spoke tensions became very unequal and it got to the point where some driveside spokes were REALLY tight and some NDS spokes were REALLY loose, but the rim was still pulled towards the NDS. Also, (obviously), the overall spoke tensions became very unequal.

After reading for a while, I figured I'd completely de-tension the wheel to 1) see if the rim is bent, and 2) re-tension the spokes correctly (or, at least more correct than they were before).

So, I un-tensioned every spoke. I loosened them all the same amount, so the thread on the spoke is JUST covered up by the nipple (as recommended by Sheldon Brown).

Now, how do I determine if the rim is actually bent? I'm not sure.

I don't think I should just start adding tension to the spokes and just hoping the rim isn't bent. If it IS bent, I want to bend it back into shape. I've read that some people disagree with this method while it works for others....well, I don't have the money for a new rim/build/wheel, so I'm all for bending it back into shape.

So, my questions (right now) are....

How do you determine if a rim is bent (once you've completely de-tensioned it)?
and
How do you fix the bent rim?

Thanks in advance.

EDIT: As I turn the wheel, it does appear that the rim is bent. But I can't tell for sure if/where it's bent, because the rim moves pretty freely from side-to-side, because the spoke tensions are so low.

Airburst

To determine whether a rim is bent, I lie it on a flat surface, which makes it pretty obvious if it's bent.

If the rim is bent, bending it back into shape over something solid (I use a block of wood) is the method I use.

Wil Davis

Personally, I'd disassemble the whole wheel and check the rim on a flat surface. I don't know of any other way of checking a rim for damage (apart from the obvious, such as dings, kinks, cracks, twists and flattening), but I'll follow this thread to learn how other folk would deal with it!

- Wil

TwoFourOne

Thanks for the replies!

Since I haven't unlaced the wheel (the hub and spokes are still on the rim), the only way to do this is to find a flat surface with a hole in the middle (for the hub).

Is there an easier way to do this?

cny-bikeman

You've already determined that the rim itself is bent. " ...it got to the point where some driveside spokes were REALLY tight and some NDS spokes were REALLY loose, but the rim was still pulled towards the NDS." It's very simple - spokes only pull, they can't push. There's only one thing that would cause the rim to go toward loose spokes, and that is that the rim is bent in that direction. Delacing the entire rim is only necessary when you suspect a very mild bend because there is some variation in the spoke tension.
It is possible to physically straighten it, but doing so is not always very successful, and the method is different depending on the type of bend. As for how to straighten it, best to just Google straigten bent bicycle wheel. You have to of course know first how and where it's bent. Decide after you've read a bit if you want to tackle it. You've already mostly disasembled the wheel, so you could build on a new one - much easier and more reliable than straightening, or just buy a new one.

p.s. You have to know of course where and how the rim is bent. You can delace but in 20 years of repair I straightend hundreds of rims and never delaced to do so. It's quite possible to determine the location and type of bend by retensioning all the spokes an equal amount of turns until none are rattling. The variation will then be almost entirely due to variations in the rim. U and S bends are treated differently.

TwoFourOne

I don't want to buy a new rim or a new wheel, because I don't have the money for that right now. And it's more fun to fix it by yourself

So I should equally tension all of the spokes a bit more until they are tight enough to not rattle, and then use a flat surface to determine where the bend is? I didn't even know that there were names for the different types of bends!

Wil Davis

If you want to check the rim for flatness, then it makes sense to have nothing (spokes, hub) in the way. I don't know a way of doing the check without removing the spokes and hub. OK, amaze me, and show me a way which does not involve any dis-assembly!

- Wil

pierce

borrow a straight rim from somewhere, and hold it up to your detensioned rim.

TwoFourOne

Is the rim really that bent? It's certainly not straight, but it's not as bent as other ones I've seen in threads that came up in searches. Here's a video of it. I can take a better video if anyone needs it.

.be
Also, cny-bikeman: could I tighten all of the spokes (equally) enough to where they don't rattle, and then find where a bend is, and then straighten it by putting my foot on the rim and pushing as I'm pulling with my hands?

I found a thread that describes putting the rim in a doorframe and pushing really hard, but the picture in that thread showed a REALLY warped rim. Mine isn't that bad, I think.

bobotech

I also was going to suggest using another rim placed up against the problem rim to see if it is bent.

I have then used things like a wood sawhorse or even the wood frame of a doorway as a anvil to bend the rim back into shape. Others use things like the end of the couch and so on.

bobotech

The video doesn't show us much of anything. If you loosened up the spokes to the point of no-tension, even a brand new rim laced up with zero tension will respond nearly the same when spun in a bike. You need to hold it up to something flat to really tell like another rim.

TwoFourOne

Ah, okay.

Holding the wheel up to a wall where a portion of the rim touches the wall (and the hub doesn't touch), I can see that there is one spot on the rim where it is not completely flat.

Horrible drawing, but I hope this helps. I held the wheel like that, and kept turning it. There's one spot where the rim touches the wall while making another part of the rim unable to touch the wall.

How exactly would I go about bending this part of the rim back into shape? As far as I can tell, it's only one spot of the rim. It's not 'taco'ed. Not sure though.

TiHabanero

It is unfortunate you de-tensioned the wheel before determining where the bend was. Well, next time just look at the thing and it will immediately show you the bend, blocks of wood on the floor supporting the unbent portion, and a force in the correct direction will do it. Now, for roundness...well that ain't happening.

TwoFourOne

So I should tension the spokes enough to where I determine where the bend is, then just bend it back using this method? I guess I'll do that.

cny-bikeman

You do not need a flat surface. I guess I should have said "the variation when rotated will then be...

If the spokes now have tension as I described just put the wheel into your frame as you show in the video and rotate it to see where the bends are. You can mark the furthest point on each side with a magic marker or similar. If you have a single, symmetric bend you will usually have three marks - one on one side and two in either direction from that one on the other.

It's best to loosen the spokes back up a bit to straighten. Be aware that watching videos does not necessarily give you the experience or the touch to do it properly. If the spokes were already fairly tensioned in the video it will be almost impossible to fix those multiple bends, but at this point if you don't want to replace anything you might as well try.

pierce

that video seems to show it has multiple wobbles in it, hard to say. if its so loose that it can flop back and forth, spinning it like that is nearly useless.

my experience has been, once a rim has been bent significantly, its never going to be straight again, any attempt at unbending it will result in higher frequency kinks elsewhere.

bobotech

I would just take the whole wheel apart at this point. Just make sure you keep the drive side spokes separate from the non-drive side spokes. This is a rear wheel, right?

Once its taken apart, then you place it against a flat surface and really tell if the rim is bent. Then it will be much easier to attempt to straighten the rim as well. I just use my body and strength to put "english" on the rim in the right places when leaning the bent portion on the doorway frame or whatever.

You will be surprised at how much effort it needed to bend the rim back.

When you get it close enough, you will be able to rebuild the wheel and it should work better.

pierce

fixed that for you. hope that helps!

bobotech

LOL
You would be amazed at the stuff that we manage to get adequately working at the bike co-op that I work at. I have straightened rims that had 1/2 to 3/4 inch of lateral runout. Sure, they weren't perfect by any means but we got them back to "good enough for a cheap bike that some poor person would be happy to use".

When you aren't looking for perfection, good enough is plenty good enough.

TwoFourOne

In the video, the spokes were very loose. I haven't touched them since I made that video. Every spoke is loosened up to the point where it's juuuust barely covering the threads on the spoke.

To mark with a magic marker, should I add a bit of tension to the spokes, or no? I can see where the rim is further to the right (laterally) as I rotate it on my bike. So is it necessary?

EDIT: It looks as if there are only 2 spots where the rim goes to the left, not 3.

pierce

I donate all my leftovers and 'used' parts to the local coop, the Santa Cruz Bike Church. you should have seen the counter guy's eyes pop at an old pair of dinged wheels (both rims had tacos from a bad pothole at speed) with duraace ultraglide 6 speed hubs. those went straight behind the counter me, I didn't want to deal with the unobtanium DA-UG stuff anymore. a whole box of flatbar brake levers with road rash and bent tips, no problem, they work adequately. my box of discarded 'used' cables? 90% servicable. my 1/2 worn tires and tubes with 18 patches ? slightly bent riser bars? awesome. collection of 7-8 speed cassettes with ratios I didn't want? no problem. I've also brought several old kids bikes that my spawn and their friends had outgrown. bikes were used when we got them, I'd fixed them for my guys, they out grew them, so I pass them on...

cny-bikeman

OK, you need to think a bit before proceeding. If the spokes are not tensioned the rim wanders back and forth randomly and tells you nothing. You are adding tension back to the spokes (by gradually turning the same number of turns on every spoke) so that they are all of the same effective length. If the spokes all are of the same length they should hold a straight rim pretty much true. Therefore any large variation is in the rim itself. The magic marker is just an example to make things easier - you could use a bit of masking tape instead, or do without. The point is to be able to confirm the pattern of out-of-true portions.

Again, with a single, symmetric bend you typically have - left, right, then left again. That is the three variations to which I referred.

It's true that some people have managed to straighten bent rims - I have done so as well. But I'm not sure you understand how the stresses in a wheel work with and against each other. Without that understanding you will be very challenged in being able to end up with a stable wheel at the end even if you can get the rim itself straight - which takes experience and a good touch. On top of it you indicate that you rode the wheel a fair amount after the rim was bent and kept retensioning the spokes. At this point you may have introduced other stresses and the rim has had an opportunity to "set" to it's current bent position.

What people who have done it don't tell you is that it does not work every time, and many of them took a few tries before they got one to work well. Truing a damaged, used rim is one of the more difficult mechanical tasks, and you are adding trying to get the rim into decent shape first. Good luck

TwoFourOne

Thanks for the replies, everyone!

Just to clarify a bit more - I'm going to attempt to straighten the rim. Currently, all of the spokes are de-tensioned.

I took a marker and marked out the places where there was a 'dip': when the wheel was mounted the frame, I marked out the spots where the wheel moved over significantly to the right side (NDS) towards the brake pads. Here's a diagram showing this. In this picture, the NDS is facing you, and the red spots are the spots where the rim moves IN towards you.



What's the best way to take the bend out of this rim? Can someone link me to some videos?

I'm getting the impression that I should put the rim on top of two pieces of wood so that the wood is on the non-bent parts, and then put a LOT of force on the bent parts to bend them back to normal. Is this right?

FBinNY 

Yes, but you need another rim, which BTW is the easiest way.

However if it's really bent you can tell by eyeballing it straight across edgewise. A straight rim will appear as a straight line with the far side hiding behind the near side. A bent rim may appear the same way, but if you look from a few angles you'll find the area where the frontdoesn't hidethe back. With a number of views you should be able to localize the bend and can begin to straighten it.

I've found that I get the best control holding it on either side and bending it against my knee. This technique works as well if you only slacken the problem area, bend and recover it.

TwoFourOne

Thank you for the help, really, it means a lot. I'm trying to understand this all.

So this means that I need to add tension to the rim BEFORE figuring out where the bends are, correct?

Buying another rim is out of the question as long as there's a possibility that this one is ride-able.