Bicycle Mechanics - Changing Frame Spacing??

I have and old custom 531 frame with 120mm spacing and a freewheel type rear hub (campy NR). I am considering opening it up to 126mm to allow the use of a 7 speed freewheel. I have read Sheldon Brown's instructions on cold bending the stays but I am still a little confused. It stated that the added space was required on the right side but further down it indicates that both stays need be be moved equally. Do I move the right stay 6mm or move each 3mm?

I would even consider opening to 130mm but I not currently prepared to buy a new rear wheel to go to a cassete type hub. I am also concerned about damaging the frame by the extra movement. Any comments on this would also be appreciated.

thanks

ditz

You move them both out the same. Ideally, the lock nuts will each be the same lateral distance from the center of the seat tube, and the rim will be in the same plane as the seat tube.

You will most likely need a longer axle.
If it will go 126 it will also go 130.
When you're all through the wheel rim should be centered between the chainstays and the seatstays. And if you reverse the wheel it should still be centered.

Al

Sounds easy enough. I am assuming that I will need a 6mm spacer for the left side for the frame to snug up against when clamping the quick release.

Thanks for the help.

ditz

It's done in two stages. Flex it out on one side so you gain 3 mm of spacing and then do the other side to sneak up on the final spacing of 126 by flexing the other side 3 mm.

To use your present wheel you'll need two 3 mm spacers. Of if you're changing to a 6 speed freewheel then a 6 mm spacer on the freewheel side and adjust the spokes to alter the wheel dish so the rim is moved 3mm to the drive side so it gets centered in the stays again.

You can also leave the frame as-is, and just spread the dropouts open a bit when inserting your 126 mm wheel.

You can also leave the frame as-is, and just spread the dropouts open a bit when inserting your 126 mm wheel.
A 6 mm mis-match will require a lot of force to make the rear wheel fit. You often hear that a 130 mm hub can be forced into a 126 mm spaced frame but that's only 4 mm and still a bit of a fight. I'd cold set the frame.

Sheldon has the procedure on his site with photos and it works well.

I've done this a couple times using a DIY tool, a long threaded rod, two nuts and large washers. Using this tool I increased the width 5mm at a time by turning the nuts an equal amount and made sure the rear drop outs were aligned with the frame by measuring the spacing between the guy line and the seatpost tube. I took some pics. Have a look at the album below. Hopefully you will get an idea how to do it.

http://www.kodakgallery.com/ShareLandingSignin.jsp?Uc=d2vwqjh.bcmpn3z9&Uy=-zgpt7c&Upost_signin=Slideshow.jsp%3Fmode%3Dfromshare&Ux=0&UV=500384483686_682820517605&localeid=en_US

Did you have to go past your desired end point to account for "spring back", for lack of a better term? I really need to take a frame from 126 to 135 and just get semi ill when I think of taking a 2X4 to a hand built English frame, lol.

I like the idea of a controlled and measurable approach.


I've done this a couple times using a DIY tool, a long open ended nut, two bolts and large washers. Using this tool I increased the width 5mm at a time by turning the bolts an equal amount and made sure the rear drop outs were aligned with the frame by measuring the spacing between the guy line and the seatpost tube. I took some pics. Have a look at the album below. Hopefully you will get an idea how to do it.

http://www.kodakgallery.com/ShareLandingSignin.jsp?Uc=d2vwqjh.bcmpn3z9&Uy=-zgpt7c&Upost_signin=Slideshow.jsp%3Fmode%3Dfromshare&Ux=0&UV=500384483686_682820517605&localeid=en_US

I've done this a couple times using a DIY tool, a long open ended nut, two bolts and large washers. Using this tool I increased the width 5mm at a time by turning the bolts an equal amount and made sure the rear drop outs were aligned with the frame by measuring the spacing between the guy line and the seatpost tube. I took some pics. Have a look at the album below. Hopefully you will get an idea how to do it.

It looks like a threaded rod, two nuts and two washers to me. A rig like that can throw a frame out of alignment because it puts equal pressure on both sides at the same time and the stays won't necessarily bend equally, especially if the drive side outer chainstay is crimped. The Sheldon Brown method bends each side individually and allows you to correct alignment while you're at it. I've used the Sheldon Brown method a few times and the threaded rod method just once and I had to use the Sheldon Brown method to correct the alignment of that frame.

Did you have to go past your desired end point to account for "spring back", for lack of a better term? I really need to take a frame from 126 to 135 and just get semi ill when I think of taking a 2X4 to a hand built English frame, lol.

I like the idea of a controlled and measurable approach.
Yes, you have to go significantly past the desired width to account for the elasticity of the steel. I've used the long all-thread rod, two washer and two nuts tool to expand a 126 mm steel frame to 130 mm and it works very well. You increase the width gradually, keeping track of how wide it is and how much you had to go beyond the current width so you can slowly approach the correct final width.

Even though it seems crude I like the Sheldon approach where only one side is done at a time. By keeping the other side unbent you can safely measure the spacing as it grows and set it to 1/2 of the desired new size for the first side and then use THAT side as your measuring base to flex the other side out to reach the final goal.

Now what would be super sweet would be to combine the screw jack setup but with the idea of the one sided bending. In other words fis up a frame of 2x4's that uses the threaded rod jack but still has a slot or space to measure from the unbending dropout to the one being jacked out. That way you could count the turns on the nut and quickly sneak up on just the right bend without overbending and having to bend back. After all the less bending you can do the better the steel will like it.

I may have to work on that concept a little......

A 6 mm mis-match will require a lot of force to make the rear wheel fit. You often hear that a 130 mm hub can be forced into a 126 mm spaced frame but that's only 4 mm and still a bit of a fight. I'd cold set the frame.

Yes, it will require a little bit extra to get the wheel in - no big deal. But it's not something one does everyday - just when you get a flat for most people. So if the OP doesn't feel confident to cold set, or want to pay the $$, leaving it as-is is another option.

When I felt one side of the drop outs were being stretched more than the other side I corrected it by turning the nuts (not bolts, I've corrected my earlier post, sorry about that) on the opposite side a few times more. I had to do this only once towards the end to get it perfect. FYI, I was re-spacing a Burley Tandem from 135mm to 145mm and had to stretch it upto 170mm to get it to settle at 145mm due to the spring effect of the rear triangle.

I agree that doing one side at a time like Mr Sheldon Brown suggests is better. If I was working on a single and not a tandem I would have done it that way. I was afraid of bending the longer top tube of the tandem if I were to floor it with 2x4s. I tried using 2x4s with the tandem on the work stand but did not have enough leverage or strength to stretch it far enough.

I've done it with several frames - the Sheldon method works great. I've heard mixed reviews about the threaded rod. Sheldon's seems so simple that it may be inexact, but I found it to work great.

I want to thank you all for your help. I think I will order a 7 speed freewheel and give it a try. Many years ago my gearing evolved to 14-16-18-21-24 while riding in slightly rolling country. I now live in quite hilly country and targeting the same geariing with 2 larger cogs to help these old legs up the hills. Here in south,central TN it seems that I am either climbing or coasting. There are not many flat runs here.

Thanks

ditz