126mm rear spacing

[justinf]

This is kind of a newbie old-frame question, but what drivetrain parts do you guys use who buy the nice old steel frames with 126mm spacing? Lightly used or NOS stock off the 'bay? Or, am I missing something here?

thx, j

[coylifut]

the NOS stuff is really expensive. I just spread the rear triangle ala cold set

[gdw]

Are you going to build it up as a 1980's reto roadbike or do you want to modernize it? If you want to run older components, buy slightly used parts on Ebay. There are plenty of lightly used parts being sold at very reasonable prices. If you want to run modern components on it you have two options. You can have the rear spread to 130mm and buy whatever you want or you can pick up an older 7 speed 126mm Shimano wheelset and build it up with 9 speed Shimano components. You can fit 8 cogs of a 9 speed cassett on a 7 speed freehub. Throw out the smallest, 12, and your nine speed shifter will handle the new 8 speed rear with no problems.

[weisan]

Throw out the smallest, 12, and your nine speed shifter will handle the new 8 speed rear with no problems.

Hmm....that's interesting...gotta try it tonight. :rolleyes:

[JasonF]

I just spread the rear triangle ala cold set

Is it dangerous from a fatigue standpoint to keep forcing the rear triangle apart? I take off my rear wheel (10 speed) to put the bike in my car for Sunday rides and then put the wheel back on when I'm ready to roll. I wonder if I should just send the frame out for a cold set (especially since I don't want to do it myself).

[Ken Robb]

I think eRichie said he thought bending or cold-settting a frame was a BAD idea. He knows more about it than I do.

[gdw]

Weisen,
Here's a link to some basic info on the conversion:
http://sheldonbrown.com/k7.html#up7
I've done it with a Shimano Frankenbike and barcons and everything worked perfectly.

[justinf]

Thanks for the info. . . the bike in question is a 80's Mercian that I just picked up for my wife. Ideally I will replace the drivetrain with newer 105 stuff (or similar) at some point for STI and triple crank purposes. I would like to hear a builder's perspective on the related frame wear and tear from a cold set. cheers

[coylifut]

I would not be afraid in the least. Sacha White cold set Christophs Spectrum and he certainly has no reservations about riding it. I have a 1980 steel Trek that I cold set years ago and then bent it the other way to accomodate a track hub.

I've been riding that bike for 25 years now and I'll be riding it a lot more.

[shinomaster]

is cold setting permanent? Or does it go back when the wheel comes out?

[Louis]

Is it dangerous from a fatigue standpoint to keep forcing the rear triangle apart?

Caveat: I am not a Strength engineer, but I do work with lots of them, I'm not completely ignorant of the subject, and I have discussed this with a Strength engineer who is a cyclist. The upshot of our conversation:

1) Assuming you don't have to apply a "large" load to spread the dropouts (and most times you don't, take a 130mm hub and experiment).

2) Assuming the frame is not very very marginal to begin with.

Then, you'll most likely be OK, just put the 130mm hub in there and go.

The bulk of the fatigue damage is done by cyclic loads. The number of cycles you put on by spreading the dropout is very small compared to the number of cycles applied by riding. (And likely smaller in magnitude also.) The constant static stress induced by the wider hub does affect the fatigue a bit, but that's kind of complicated (R ratio and all that stuff).

Finally, 1) don't sue us if this doesn't work, and 2) e-Richie knows a bunch more than I do about frames.

Louis

[palincss]

is cold setting permanent? Or does it go back when the wheel comes out?

If you bend the triangle enough for the stretch to be permanent, that's cold setting. It is possible, though, to flex a frame apart enough to get a few extra mm of clearance. Rivendell has several frames that are set to 132.5, so you can use either a 130 or a 135mm hub, and back in 1991 Tom Kellog was building Spectrums with a rear spread halfway between 127 and 130, so you could use wheels of either dimension. Steel and titanium both allow this much spreading with no harm or difficulty for users.

[Fixed]

the NOS stuff is really expensive. I just spread the rear triangle ala cold set
I agree works fine with steel bro. cherrs :beer:

[justinf]

How is a cold set done?

[Jeremy]

How is a cold set done?

Hi,

"Cold setting" is the less scary way of telling a customer that you are going to bend the frame. In most cases, cold setting a steel frame is easy and will not fatigue the metal enough to have any significant effect on the durability of the frame.

I am assuming that you don't have access to a frame jig and specialty tools. The easiest way to cold set a frame is to grab the dropouts and pull them apart. On older steel frames you will be amazed at how easily they bend. However, this method is not particularly accurate and often results in only one of the chainstays bending and thus you have a misaligned rear triangle. You can isolate each side by having someone help you. Place the frame on the floor and protect all of the contact points with towels, rags, etc... Elevate the rear end of the frame by supporting the seat tube and bottom bracket with riser blocks of some kind. Make sure to protect the contact points on the frame. Have your friend hold the head tube solidly to the floor while you push down on the lower dropout until you get the deflection that you need. Flip the frame over and repeat.

You can check the alignment by taking some thin stretch cord and running it around the head tube, through the dropouts and tieing it off. Measure the distance between the cord and the seat tube. Make sure that the cord is symetrically aligned when you take this measurement. The measurement should be equal on both sides.

Another thing to consider is that the dropouts will be slightly canted after cold setting the rear triangle. This is usually so small that it doesn't matter, but if you want to make that right you really do need to use dropout alignment tools.

Lastly, a little history. When Shimano introduced 8sp at 130mm OLD, the industry standard was 126mm OLD. Their solution was to use dramatically beveled locknuts on both sides of the rear hub. This simply forced the rear triangle to expand as the wheel was pulled into the dropouts. This was not cold setting because the frame would spring back to 126mm when the wheel was removed. However, it took at least a year for frame specs to catch up with the 130mm OLD. So there were quite a few bikes using a 130mm hub in a 126mm frame.

Jeremy

[Fixed]

bro that Jeremy is one smart cat a 130 will fit in a 126 most times with a little tug i.m.h.o. Cheers :beer:

[flydhest]

Before anyone else goes quoting e-richie, however, one should look at what he actually wrote. I seem to recall this coming up a while ago. I believe he made it clear that he doesn't do that sort of work but was unwilling to say that the practice was "bad" somehow.

[justinf]

that is some good advice jeremy, thanks, especially the alignment-by-string check. I'll give it a shot. . .