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achurch
03-14-2009, 12:40 PM
Am looking for some advice about fixing what I assume is an out of alignment rear triangle on a steel frame bike.

Novice diagnosis:
as I am not sure what I said above is technically correct let me share what I see...
Rear wheel is +/-3 mm off center at rear stays and barely visibly out of line with seat tube when looking carefully from behind.

It is a cross frame and I am only running 28s so a tire fits no problem and can set up the brakes fine--but it is definitely off center...

So questions:
Does it matter? (besides being annoying)
Can I bend the rear triangle back to center (it's a steel bike)
Can I shim the left side of the connection where the wheel and frame meet (<1mm of space here straightens the wheel right up so if I insert a shim voila--but not sure if that is safe?; but why would it not be?)

Thanks for any advice...

Andy

weaponsgrade
03-14-2009, 01:06 PM
are you sure the wheel is properly dished?

achurch
03-14-2009, 01:17 PM
I think it is not wheel dish because:
Have tried multiple wheels that fit other frames to rule this out and have the same problem.
Also wheel dish would not (i think) explain the seatpost tube / wheel angle.
When looking at the bike from the back you can notice that the wheel is ever so slightly out of parallel with the seatpost tube.

Louis
03-14-2009, 01:22 PM
Just take it to a good LBS. They'll have alignment gages and ought to be able to fix things without too much trouble.

Louis

achurch
03-14-2009, 01:52 PM
I like the satisfaction of doing my own bike maintenance work and especially enjoy troubleshooting / problem solving my way through new issues rather than having someone else do it for me.

Louis
03-14-2009, 02:10 PM
I like the satisfaction of doing my own bike maintenance work and especially enjoy troubleshooting / problem solving my way through new issues rather than having someone else do it for me.

I agree, I too do my own wrenching, but some things need to be done so infrequently that it's not worth 1) buying the tools, and 2) learning how to use them properly. Hopefully you won't be getting frames out of whack often enough for this to be the case for you. However, if you want to DIY then check out the Park Tool web site, get what you need and have at it.

Louis

David Kirk
03-14-2009, 02:34 PM
Would you have a photo of the rear dropouts?

dave

achurch
03-14-2009, 02:37 PM
with or without a wheel?
And will you send me an e-mail address so do not have to resize...

David Kirk
03-14-2009, 02:43 PM
FWIW this is pretty easy to check with a piece of string.

* take the rear wheel out
* take a piece of string and wrap it around the head tube and go back to the rear dropouts. Rig the string so it goes into the axle slot. It will depend on the design of the bike but usually its easiest if you have the string go on the outside of the dropout and into the axle slot.
* if a seat tube bottle cage gets of the way string, take it off.
* pull the string tight and make sure it's not hung up anywhere and makes a clean path from headtube to dropout and that both sides are running in the same way.
* pull the string tight and measure the distance from the string (where is passes by the seat tube) to the seat tube. If one side is significantly different than the other there is a good chance that the rear end is off to one side.

This is not super accurate but it is something you can do at home. If done carefully it's more than close enough.

dave

David Kirk
03-14-2009, 02:44 PM
with or without a wheel?
And will you send me an e-mail address so do not have to resize...

either - info@kirkframeworks.com


dave

achurch
03-14-2009, 03:16 PM
Cool measuring trick--thanks

drive side is 2/8 of an inch longer than other (as measured seat tube to drop out along string from head tube to drop out)

Peter B
03-14-2009, 03:34 PM
I was going to suggest taking the frame to a local builder when I read your initial post but it looks like the framebuilder came to you!

I think this is the measurement Dave's describing. Not clear to me from your last post if that's how you were doing it.

achurch
03-14-2009, 03:39 PM
That is not what I measured. I measured the distance from the seat tube to the dropout. Will do the correct measurement and repost:-)

achurch
03-14-2009, 03:47 PM
Okay, with some visuals to guide, I have remeasured and the distance is 2/8 of an inch more on the drive side between string and seat post.

Peter B
03-14-2009, 03:57 PM
As Dave said, just be sure the string runs true on both sides and isn't being deflected by a cable or boss, etc.

If it's off by 1/4" as you say, I'd suggest having it checked by a good framebuilder who can put it on an alignment table and give it a thorough look. Might be tweaked in another plane also.

Depending on what the frame is and what is out you may not want the local wrench just yanking on a chainstay.

achurch
03-14-2009, 04:24 PM
Have sent an e-mail to a local framebuilder in Montreal; will let you know what I learn...

K Bedford
03-14-2009, 07:29 PM
If after checking the side to side as Dave suggested you find that it close in this respect it will probably end up being a slight difference in the dropout slots.
This is not unusual in a raw frame before alignment but should be corrected in the final alignment process.
This is done by minor filing or grinding of the dropout slots.
This is also touchier to do than adjusting the side to side centering of the dropouts because once material is removed there's generally no putting it back.
This is best left to someone who's done this many times.