bicycle rim bent?

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  #1  
Old 04-27-09, 08:14 PM
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bicycle rim bent?

This is a bicycle question, posted here because I don't see a forum listed specifically for bicycles.
I acquired an old fixer-upper 25-speed Peugeut bicycle, and when you turn it upside down and crank the pedals and watch the rear tire though the rear fork, it is very noticeable uneven spacing between the tire and the fork as the wheel turns around, as though the rim might be bent. And of course it rubs back and forth in an uneven manner on the brake pads the wheel turns around. But looking at at the tire/rim with the naked eye it doesn't really look bent, but it's hard to tell. Is there a way to check whether it is actually bent without taking the whole rim/tire off the bike? Is there something that might just be out of adjustment or is the wheel probably bent if it's acting as I described? I have no experience taking rear wheels off these multi-geared type bikes, and looks like a lot of trouble trying to get the wheel separated away from the chain and deraileur and all that.
 
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Old 04-27-09, 08:56 PM
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You have some spokes out of adjustment. Going to take a good bit of time and patience (and a spoke wrench) to true it up, but it usually is do-able.

If you Google "trueing a bicycle wheel" or "adjusting bicycle wheel spokes" or something similar you will get a good bit of info on how to tackle it.
 
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Old 04-27-09, 10:22 PM
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Thanks Tow Guy. I Googled and came up with an excellent description of how to true a bicycle wheel by adjusting the spokes: How to True a Wobbly Wheel

Glad to know I don't have a bent rim.

But now I need to Google some more and find out how hard it is to take the dang rear wheel off too, because I need to put on a new rear tire. Probably gotta take the derraileur off and stuff?, hope its not too involved for somebody who's never tried it...
 
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Old 04-28-09, 06:15 PM
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It's not really as hard as it might seem, but it's a bit of a PITA. Take some digital pics before you start. While I was checking the availability of the rim trueing info I noticed some stuff on deraileur work, etc, so shouldn't be hard to find enough info.
 
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Old 04-28-09, 06:30 PM
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To remove the rear wheel, start with the chain/gear selection on the small sprockets front and rear. You won't have to remove the deraileur, as the chain will have enough slack to allow you to pull it back out of the way. When you re-install, just tighten a bit at a time from each side.

As for a bent rim or not, it is hard to tell with some tight and some loose spokes. If you are not happy with your efforts and want to continue, just post back and I will walk you through it. I've built many wheels and fixed them by the thousands.

One tip is to apply some oil to the spoke at the top of the nipple and get a spoke wrench that fits well. The nipples are made of brass and are easily damaged. When done, use a cleaner to remove any excess oil.

GL
Bud
 
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Old 04-28-09, 09:33 PM
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Bad news, the rim is actually bent. I stopped in the local bike shop to look at some new tires and get a spoke wrench. While there, I showed my rims to the bike mechanic there. He said my rear wheel was bent, "unfixable". Said something drastic happened to it. I asked him how much a new wheel cost and he said about forty bucks.

I'm hoping I might be able to find a used wheel for cheap from somebody who might have one they don't need. Otherwise, can I just buy a new rim (rim only, without the spokes and hub and gears) and "build" myself a new wheel using the same old spokes and hub and gears? Any advice appreciated, I don't mind doing a little work if I have to, although I've never tried to build a wheel or fix such a problem before. Also I'm tight on money, want to spend nothing if possible, or bare minimum of expense.
 
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Old 04-29-09, 06:29 AM
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Not to be critical about the mechanic, but a dented rim is easy to see, where a bent rim has to have all of the tension released before you can see what shape the rim is in. And even if bent, to a certain degree it can be straightened, you just do that before you tighten the spokes.

First, what size and type rim is it. Steel or aluminum (use a magnet if necessary). What size is the tire?

To start, I loosen all nipples two full turns, even the loose ones. That reference means that when I want to start tightening back up I tighten each two turns and I'm back where I started. You will be watching two things, true (side to side) and hop (up and down). Too much tightening in one area will create a hop, thus a little at a time all the way around keeps the hub centered.

After all spokes are loose, now examine the rim. If it is indeed bent, you will see it. On a goor work bench you can extend the rim over the edge and apply pressure and straighten it back to near normal. Bending it over the edge of a bench does take some thought and a very gentle approach.

Once straight, or reasonably straight, the spokes can do the rest and still give you a strong wheel.

What do you think?

If you decide to replace the rim only, let me know again as there is an easy way, well easier than taking it all apart and starting over.

Bud
 
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Old 04-29-09, 09:49 AM
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Originally Posted by Bud9051 View Post
What do you think?
Bud
Thanks Bud, I'll get specific answers for you as to wheel/tire size/type later today. I'd definitely like to be able to fix the "unfixable" if possible. I noticed on this bent rim that none of the spokes seems loose to me, in fact they all seem pretty tight...
 
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Old 04-29-09, 10:47 AM
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If they are currently tight, start with the oil, just makes the job a lot easier, and with a spoke wrench you can try to true the wheel. It will tell you if it is actually bent when the spokes you want to tighten are already too tight and the ones on the other side are not. Spokes on each side move the rim to that corresponding side. When you true a straight rim, you get a straight wheel with all of the spokes (theoretically) at the same tension and a strong wheel. When you true a bent rim, you can get a straight wheel, but the spokes on one side in a specific area will be too tight and the ones directly opposite will be too loose and you have a weak wheel.

When you are ready I will explain more.

Bud
 
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Old 05-01-09, 09:25 AM
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Originally Posted by Bud9051 View Post
First, what size and type rim is it. Steel or aluminum (use a magnet if necessary). What size is the tire?
The tire size is 26 x 1.95. Not sure if the rims are aluminum or steel (didn't have a magnet), but am assuming they're probably steel. The bike is an old Peugeot Orient Express mountain bike (apparently a late '80s model.) I'm not even sure how many speeds it has. Here's a couple of pictures of the rims sitting side by side next to eachother.
http://i207.photobucket.com/albums/b...ull1/rims1.jpg
http://i207.photobucket.com/albums/b...ull1/rims2.jpg
The rear wheel doesn't look bent in the photos or to the untrained eye, but it was way out of true when the bike mechanic spinned it and said it was unfixable.
 
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Old 05-01-09, 05:25 PM
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I would guess aluminum from the color, which is a lot easier to bend. Since you are probably not going to be jumping curbs and such I would start by simply tweaking a few spokes. Get your spoke wrench, and pop the wheel back into the rear stays. If necessary tie the chain out of the way, not around the sprockets. Rotate the wheel and decide what areas look good and what areas need to be moved left or right. Also note if the rim is moving up and down, not good. Lube spokes as mentioned before and then start at the valve hole and squeeze the spokes in pairs left and right to get a sense as to which areas are tight and which are loose. Now squeeze the spokes in the areas that need adjusting.

Added note: When turning the spoke nipple, decide the direction that moves it towards the hub, tighten, or away from the hub, loosen. As you rotate the nipple you need to feel if it is turning on the threads or just twisting the spoke. That's why we lubricate then as rusted nipples may not turn at all and will eventually break the spoke, again bad as the cluster side requires the freewheel to be removes, special tool. If you find any broken spokes to start, you will need a trip to the shop to get some spare spokes and possibly pull the sprocket.

Back to adjusting. As you squeeze a pair of spokes you should see the rim move to that side, thus as you tighten spokes on one side the rim moves the direction you want. Avoid over tightening one side and then the other back and forth as you will pull the rim towards the hub and create a hop. As the rim is getting close to where you want you need to judge if all of the spokes need to tighten up a bit. Test some while at the bike shop to get an idea. But if needed, start at the valve hole and go around to every spoke and give it 1/2 turn tightening.

Darn, the process becomes so automatic that is difficult to explain even in several paragraphs. Do your best and let me know how it goes.

Bud
 
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Old 05-02-09, 09:23 AM
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Thanks Bud for the explanation. I'll will be working on it soon and will post back here with progress report.
 
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Old 05-03-09, 08:53 PM
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Bud what do you think of this video about truing the rim? YouTube - Bicycle Wheel Truing Maintenance Video
And you describe where exactly I need to put the oil on the nipple? Is 3 in 1 oil an okay oil to use?
 

Last edited by sgull; 05-03-09 at 09:38 PM.
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