removing flat spot in vintage Super Champion rim
03-07-21, 11:49 PM
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removing flat spot in vintage Super Champion rim
I have been trying to true an old Super Champion rim off of a early 80's Peugeot. I am a novice at wheel work so maybe I am missing something but there is a flat spot on the rim and even though I have completely loosened the spokes around the flat area the flat spot remains.
If I de tensioned all the spokes completely would the rim regain its original round shape?
The thought occurred to me that there might be a tool that would push the rim back in shape. Has anyone ever seen such a tool?
If I removed all the spokes is there any way to remove the flat spot? My guess is that the aluminum is fairly soft and should be malleable.
At what point is such a rim no longer usable?
If I de tensioned all the spokes completely would the rim regain its original round shape?
The thought occurred to me that there might be a tool that would push the rim back in shape. Has anyone ever seen such a tool?
If I removed all the spokes is there any way to remove the flat spot? My guess is that the aluminum is fairly soft and should be malleable.
At what point is such a rim no longer usable?
03-08-21, 07:06 AM
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If you have released the tension of the spokes in the are and the flat spot remains then the only choices left are to find some way of removing that flat spot or replacing the rim. The aluminium has a certain pliability, such as to absorb whatever impact created your flat spot, but I don't know how safe your wheel is today at around 40 years old.
03-08-21, 07:19 AM
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Overland used to offer a tool to help with this. Results are seldom perfect, but may be an improvement. Perhaps an established shop in your area might have one?
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03-08-21, 07:39 AM
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I tend to saw up some old chipboard to create a positive and negative form, and use my vise and an incantation (wifie calls it swearing, but I insist).
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03-08-21, 07:49 AM
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03-08-21, 07:54 AM
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The only issue with aluminum and bending cycles is fatigue and introducing brittleness with work. If the flat spot is severe enough to risk destroying the rim, go for it. Sheldon Brown posted a roadside wheel fix involving a pole, a hank of rope, and a spoke wrench. He did specify that it's not an ideal fix, but enough to get to a bike shop, or home.
03-08-21, 08:27 AM
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I think a previous member(FB-something?) said that some old rims were so soft that you could unlace the flat-spotted section, insert your foot and simply pull the rim out into round(ish).
I’ve never had any luck with that, but I have gotten good results using a wooden cradle and a C-clamp.
I’ve never had any luck with that, but I have gotten good results using a wooden cradle and a C-clamp.
03-08-21, 02:45 PM
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...in case you are interested, there are still a couple of tools being made and sold to the European market that will help you work on flat spots in a rim. Back when I bought them, you had to order from a Euro supplier, like Hollandbikeshop.com We had a number of tools to work on older rims at the co-op here. From my experiences doing that over there and at home, it's pretty difficult to work out a flat spot in a box section rim...easier in a single wall rim.
If it's a Super Champion rim, make sure it has a bead hook before you waste any time on it.
At this point in my life, a rim needs to be pretty special to waste much time straightening it. It's almost always quicker to just build with a new rim, and the new rims are usually lighter and stronger.
https://hollandbikeshop.com/fietsger...slag-werktuig/
...in case you are interested, there are still a couple of tools being made and sold to the European market that will help you work on flat spots in a rim. Back when I bought them, you had to order from a Euro supplier, like Hollandbikeshop.com We had a number of tools to work on older rims at the co-op here. From my experiences doing that over there and at home, it's pretty difficult to work out a flat spot in a box section rim...easier in a single wall rim.
If it's a Super Champion rim, make sure it has a bead hook before you waste any time on it.
At this point in my life, a rim needs to be pretty special to waste much time straightening it. It's almost always quicker to just build with a new rim, and the new rims are usually lighter and stronger.
https://hollandbikeshop.com/fietsger...slag-werktuig/
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03-09-21, 02:58 AM
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I suppose MDF would do, I just have a free and limitless supply of chipboard, AKA particle board 
03-10-21, 08:24 PM
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I've used the same method on an old Mavic rim. i didn't even take the tire off. A C-clamp provided the necessary motivation.
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03-11-21, 01:24 AM
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I flat-spotted a single-wall Sun rim "back in the day." (I hadn't learned the importance of avoiding 'target fixation' yet!)
Anyway, I had the same issue, so I figured since the rim's considered "toast" at that point, why not get creative?
So I removed about six spokes from around the flat spot and grabbed some wooden blocks and a hammer. I supported the rim on the floor with wood blocks on either end of the flat spot. Then placed a block over the worst part of the flat spot and hammered it back to round. Tensioned up the spokes, trued the wheel and it was like new. (It obviously wasn't.) So I rode that wheel for about five years thereafter. Never had problems or broke a spoke. But a frame failure and subsequent warranty necessitated a new rear wheel, so it has been in storage ever since.
Given your description, I'd use the tool suggested. Can't believe I've never seen that one before. (learn something new every day) But be careful, I assume that rim's aluminum is VERY soft. Bend with care! But I'm guessing you'll fix it just fine. If you do use wooden blocks, I'd shape them to fit the curvature of the rim (on both axes) to ensure you don't just end up denting the rim locally and not actually pushing out the flat spot.
Good luck!
Anyway, I had the same issue, so I figured since the rim's considered "toast" at that point, why not get creative?
So I removed about six spokes from around the flat spot and grabbed some wooden blocks and a hammer. I supported the rim on the floor with wood blocks on either end of the flat spot. Then placed a block over the worst part of the flat spot and hammered it back to round. Tensioned up the spokes, trued the wheel and it was like new. (It obviously wasn't.) So I rode that wheel for about five years thereafter. Never had problems or broke a spoke. But a frame failure and subsequent warranty necessitated a new rear wheel, so it has been in storage ever since.
Given your description, I'd use the tool suggested. Can't believe I've never seen that one before. (learn something new every day) But be careful, I assume that rim's aluminum is VERY soft. Bend with care! But I'm guessing you'll fix it just fine. If you do use wooden blocks, I'd shape them to fit the curvature of the rim (on both axes) to ensure you don't just end up denting the rim locally and not actually pushing out the flat spot.
Good luck!
03-11-21, 11:37 AM
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There's also the old belt trick. You loosen the spokes and you grab a old belt and sling it over a strong rafter and then tie up the belt over the flat spot. Then you simply pull down. I've also seen people use a post and tie it up and pull on it /pull down. Tie down straps also work good like this.
03-11-21, 02:31 PM
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1. English wood vise.
2. Blocks of wood.
3. Use English wood vise as a hydraulic press.
That's what I do now...works like a charm.
=8-)
2. Blocks of wood.
3. Use English wood vise as a hydraulic press.
That's what I do now...works like a charm.
=8-)
__________________
5000+ wheels built since 1984...
Disclaimer:
1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:
Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life
5000+ wheels built since 1984...
Disclaimer:
1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:
Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life
03-12-21, 01:35 PM
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Cyclus makes another tool for pushing out flat spots
https://www.bike24.com/p292610.html
https://www.bike24.com/p292610.html
