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Old 11-09-08, 10:10 AM   #1
idegen
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Steel frame alignment problem

A while back, I respaced the rear dropouts on a steel frame from 120mm to 130mm following Sheldon's instructions. This year I decided to use the bike on my trainer, and I noticed that the bike very noticeably leans to the left in the trainer, which causes my right sitbone to get sore. To get the saddle level, I have to put almost an inch of stuff under the left trainer foot. My other bikes are level in the trainer, so I am pretty sure it is this bike.

I have been going kind of crazy trying to fix the problem. I tested the alignment using Sheldon's string test and made some small adjustments, but with no luck. Using that test, the alignment is within a millimeter. As the frame has semi-horizontal dropouts, I thought that it might be caused by the rear wheel not being properly dished, causing me to misalign it. I redished the wheel and made sure the axle was seated in the same location in the dropout on both sides, again with no luck.

I am sort of at a loss of where else the problem may lie. Again, the trainer seems fine and the floor is level. Any suggestions?
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Old 11-09-08, 10:16 AM   #2
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Hmm. Sounds like you have done all the right things. From the way you described it, I predict you did it correctly, but might I suggest checking wheel dish again? It is easy to get that wrong.

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Old 11-09-08, 10:57 AM   #3
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I wonder if the rear dropouts are the same height.

I have an alignment tool that looks kind of like two mushrooms that bolts into the dropouts. It's threaded so you can move the mushrooms near to one another. When the mushrooms align perfectly, you know that the dropouts are even and parallel.
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Old 11-09-08, 11:20 AM   #4
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I can't imagine how wheel dish would make the bike lean when mounted on a trainer. It is attached at the quick release ends and the wheel is not involved. You can mount a bike in a trainer with no rim or spokes, just a hub.

It sounds to me like the frame is severely twisted and no amount of stay bending or wheel dishing is going to fix it. The headtube has to be in line with the seattube.
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Old 11-09-08, 12:02 PM   #5
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Quote:
Originally Posted by Dirtdrop View Post
I can't imagine how wheel dish would make the bike lean when mounted on a trainer. It is attached at the quick release ends and the wheel is not involved. You can mount a bike in a trainer with no rim or spokes, just a hub.

It sounds to me like the frame is severely twisted and no amount of stay bending or wheel dishing is going to fix it. The headtube has to be in line with the seattube.
What if, during the process of cold setting the rear triangle, he managed to somehow tweak the rear triangle. The dropout height wouldn't have to differ by very much to make the seat tube (and head tube) lean quite a bit.
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Old 11-09-08, 12:06 PM   #6
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Quote:
Originally Posted by idegen View Post
A while back, I respaced the rear dropouts on a steel frame from 120mm to 130mm following Sheldon's instructions. This year I decided to use the bike on my trainer, and I noticed that the bike very noticeably leans to the left in the trainer, which causes my right sitbone to get sore. To get the saddle level, I have to put almost an inch of stuff under the left trainer foot. My other bikes are level in the trainer, so I am pretty sure it is this bike.

I have been going kind of crazy trying to fix the problem. I tested the alignment using Sheldon's string test and made some small adjustments, but with no luck. Using that test, the alignment is within a millimeter. As the frame has semi-horizontal dropouts, I thought that it might be caused by the rear wheel not being properly dished, causing me to misalign it. I redished the wheel and made sure the axle was seated in the same location in the dropout on both sides, again with no luck.

I am sort of at a loss of where else the problem may lie. Again, the trainer seems fine and the floor is level. Any suggestions?
This is easy to diagnose, put another bike in the trainer.

If it's the bike, then issue goes away with new bike in trainer. If it's trainer/floor/alignment of the planets then it's obvious. I can't think of any thing that isn't severely, obviously wrong with your bike that would cause your issue.
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Old 11-09-08, 12:12 PM   #7
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What's the bike like out of the trainer? If it's normal when riding it ditch the trainer and use rollers
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Old 11-09-08, 02:24 PM   #8
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Thanks everyone for the feedback!

I already tried two other bikes in the trainer and both were fine.

I am also pretty sure it is not the dish. Although with semi-horizontal dropouts I could theoretically misalign the wheel in the dropout, I checked ot make sure the axle was placed in the same location in the both the right and left dropouts, so it shouldn't be that.

The bike rides ok off the trainer. I don't notice a pull to either side or anything like that.

If the frame were twisted, it would have to be twisted between the seat tube and the dropout, given that the seat tube is slanted towards the left. (If it was between the seat tube and the head tube, I would expect the seat tube to be at a 90 degree angle with the ground but the head tube to be slanted left.) I don't see anything obvious, but I suppose it is possible that somehow the stays got bent so badly. Besides being respaced, the bike has been shipped by FedEx quite a few time and they haven't always been as gentle as one would hope.

Is there any way to cheaply make an alignment tool like the one Retro Grouch has? If the issue was that the stays were twisted, would be feasible for me to repair it anyway? Any other recommendations?
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Old 11-09-08, 08:57 PM   #9
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T ake it to a framebuilder and have him put it on his alignment jigs. Then you'll know for sure.
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Old 11-09-08, 11:40 PM   #10
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The string is good for checking so you don't get side tracking,but that's it.

Short of having a granite plate or some known reference point like a jig of some kind,you can check for twist between the head tube and seat tube with a level by laying the frame on it's side,level the the seat tube,then check the head tube.Both should be the same.You can check for twist in the rear triangle with the same level.Set the bike upright/upsidedown,put your level across the chainstays as close to the seat tube as you can,level the bike,slide the level as far back as you can towards the dropouts,read level.Both should be the same.That will eliminate everything but the dropouts themselves.You would need a known straightedge or known reference that clamped into the dropouts in order to include them in your level measurements,or any measurements for that matter.

I don't know how bikes fit into trainers but is the front wheel on it?If the front wheel is off and clamped into something,that will come into play also.

The mushroom things will not check for frame twist,they will align the dropouts straight and parallel with each other,but without reference to anything else.They can be aligned perfectly and still not be parallel with the BB or front axle.The headtube could be twisted 90',those won't find it,as an extreme example.I think we all know that.

Just seems strange that that bike would track correctly when riding normally if there was any twist in anything.From what I'm reading,it seems like it's setup in the trainer somehow.

Last edited by Booger1; 11-10-08 at 12:10 AM.
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Old 11-10-08, 03:53 AM   #11
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It just sounds to me like the wheel isn't fitted to the trainer properly. Side to side wheel alignment will have no effect.

I put my bikes in the trainer as a work stand and I've noticed that bolt on wheels don't sit properly in the ends and the bike has a tendency to lean to one side when you put weight on it. If its a quick release wheel then make sure you are using the same skewer as the bikes that fit properly. It may just be the type of skewer your using. Also are the other bikes spaced at 130mm or are they possibly spaced at 135mm?

If its not in tight enough it will lean.

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Old 11-10-08, 07:33 AM   #12
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I will have to play around with the trainer-bike interface again. Everything seems tight, but I should try things like reversing the skewer or trying a skewer from a different bike. The other bikes are spaced at 135mm, but I adjusted the trainer for this bike. Thanks for the suggestions.
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Old 11-11-08, 08:58 AM   #13
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I tried tightening the stand and changing skewers with no luck. I guess it is probably something with the frame.
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Old 11-11-08, 06:29 PM   #14
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Is the threaded end of the skewer sticking out past the nut? When I first set up an old 6 spd in the trainer with the skewer provided, the longer skewer extending past the nut prevented the trainer from clamping properly.
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Old 11-11-08, 07:42 PM   #15
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If the rear triangle is out of alignment the wheel will noticeably cant to one side. Try flipping the wheel.
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