Rear spacing problem
 

Evening,

I am working on my Motobecane GR project, and am stumped. I spread the rear from 120 MM to accommodate a 126 MM Campy SR hub w a 7 speed Regina freewheel. Things were working OK. Then, I swapped out the Regina freewheel with a Sachs 7 speed to get some easier gearing for my hilly area. The Sachs seems to be a bit wider than the Regina, and when I am in the smallest gear, the chain rubs against the seat stay, right where it connects to the dropout. So, I tried moving the hub cones over a bit, to shift everything towards the other side, and make room for the wider freewheel. Still rubs, and the axle length does not allow me to move it over any more. The axle is 134 MM. In case it matters, I have a Campy SR RD. So, I'm out of ideas and need some help. Thanks

Picture would help.
What was the smallest gear before? I am betting a 14.
Now what is the smallest?

You also might have too short of an axle. The rule of thumb is 10mm longer than your rear spacing. But as OFG says, a 2mm spacer and a redish are likely called for.

Neal

Or a narrower freewheel.

Shifting cones around won't help you because the overall distance between the locknuts is still the same. Like OFG said, you need to increase the amount of spacing on the driveside to move the locknut farther from the freewheel (and then a re-dish) or you need a freewheel spaced more like the old Regina.

What are the overall width measurements of both freewheels?

Old Fat Guy;12083360]You need a spacer on the drive side, and a wheel redish.

I figured I would need a redish. The problem I have with spacers is that I don't have enough axle to work with. I was just looking around and found a 141 MM axle w Campy threads at Harris Cyclery. That would give me enough axle to move things around or add spacers, but might be close to being too much axle to fit between the dropouts. I guess if worse came to worse, I could grind off a MM or two. With the existing 134 MM axle, I just don't have enough room to do much, and still have a little axle to go into the dropouts. Am I on the right track with this idea? Do you know of a source of Campy axles? In the perfect world, I would find a 10MMx137 MM x 26 TPI axle. Harris only has that length in a 9.5 MM diameter. Thanks for the advice.

The original freewheel had a 12 tooth smallest gear, the new Sachs is a 13. The new freewheel is 1.5 MM wider.

So you need a 1.5 mm spacer for the right side, assuming the axle was properly set up for the old freewheel. (Actually what you need is 3 mm of clearance between the outer face of the smallest cog and the face of the locknut. Use that as your benchmark.) Then don't forget to remove 1.5 mm worth of spacers from the left side to keep your OLD at 126 mm. Even if your OLD has to increase to 127 or so (because sometimes you don't have enough spacers of the right combination of sizes to make it come out exactly right), that will still give you 3.5 mm of axle sticking out beyond the end of each locknut. This is loads -- more than enough. You will need to re-centre the rim.

If you really feel you need 5 mm of axle at each end, buy the 141 mm and cut it down to 136 or 137. I've done this with really long axles to build tandem wheels, which need 145 mm OLD, out of single-bike hubs -- it works fine.

Be aware that if your axle is too long it can stick out beyond the DO edge(s) so much that the QR skewer won't be able to contact the dropout or derailleur claw. The nominal axle length for 126mm DO spacing is 137mm. You may have to re-position the bearing races to accommodate either a claw or an integral RD hanger. If you're going to be shifting spacers from left to right anyway this is the time to get this right.

Or maybe you knew this already, in which case you can just ignore this note.

This is one of those problems that just gets more confusing as the answers come in. So, most of you have made suggestions as to how I can space this axle/cone setup to fit a 126 MM spread, and work in a frame spacing of same. However, I have two cones, two lock nuts, two thin washers and a fairly wide spacer in place on the existing setup, which takes me to 128 MM total. Now, that worked with the former Regina freewheel, with not much axle left to spare. So, say I add a 3 MM spacer to make it work with the new, wider Sachs freewheel. Now I am at 131 MM spread, which is a tough fit for the frame, and I need a longer axle. I have already spread the frame from 120 MM to 128 MM. I would prefer not to spread it more. In looking at the lock nuts, they strike me as overly wide. They are about 7 MM wide, and have an adjustment slot for a cone wrench. It seems like I could get by with a much thinner lock nut, and do not need one with a slot for a cone wrench. Looking at various axle setups on ebay, velobase, etc. I see thinner nuts out there, but I have only found them for front axles. I've checked numerous bike shop web sites, and can only find the 9.5 MM front axle nuts. Does anyone know of a source where I can find a 10 MM 26 TPI lock nut thinner than 7 MM? Anyone have any loose ones in their spare parts bin?

It all seemed so simple when I started. All I wanted was a new freewheel with a couple more teeth.........

You're right, don't spread beyond the 128mm. Are you sure the Sachs is not an 8 speed? I know, hard thing to overlook, but I've done it in the past!

So, if I understand correctly, the Regina was set-up to work with 128mm OLD? Now the wider Sachs require more room, but your wide locknuts don't allow the hub to move any further left? Those nuts are standard issue on all those old Campy hubs, BTW. Ditching the Sachs for a narrower 7 speed freewheel might be the most sensible thing to do.

This may sound like an incredibly dumb question but... since these are probably semi-horizontal drop-outs, can you move the axle forward in the drop outs at all? That would effectively lower the center of the axle and perhaps move your chain into a wider area in the seat stays.

You say you have spacers on both sides? Is it the kind of situation that might be solved by moving one or both of those spacers from the left side to the right side, therefore not changing the overall spacing, but getting more clearance on the drive side? Or do you need the room on the other side to keep it from rubbing too? Then a slight re-dish if the wheel ends up noticeably off center (which it probably will).

I'm going to make another suggestion, have you made sure of the following:

1) The rear triangle is square, it's easy when bending things to end up a few mm out of square.
2) Are the dropouts square to each other sometimes when you spread the stays out, the dropouts end up angled slightly out, so they are not square.
3) Is the RD hanger square to the freewheel, while with friction shifting it can cause fewer problems then with indexed shifting, it can still cause problems.

Any of these can do funky things to your drive train....

Can I throw another wrench into this machine? I recently did just this very thing to my Raleigh. As luck would have it, I had a 2mm spacer and everything went together fine (I had to pull kinda hard on the seatstays to get the new, really long combo in there).
My concern is this, how much axle needs to show outside the locknuts? In other words, what's the minimum amount of axle that needs to stick out into the dropouts?

+1 I'm very curious about this as well, attempting to get my old Raleigh up and running in the snow, this not riding thing can drive a man insane.

I do not have any spacers on the non drive side. When I spread the frame I did an alignment check and it was right on the money. Did not notice if the dropouts where bent. Nothing noticeable at least. Will check that when I get back in town Friday. And yes, the new Sachs freewheel is 7 speed. Counted it twice in an effort to cut down on the more obvious stupid mistakes.

I would say that is too much. I recently went through these very issues converting my Raleigh Gran Sport to a 6-speed with some new old hubs I picked up. First, a 137mm axle is fine for a conventional 126mm 6-speed. With a claw the axle has to be positioned asymmetrically to the right on the hub. The reason is because the non-forged dropouts are thinner but the extra length on the right is taken up by the claw thickness.

If you have much more than a mm or so sticking out past the outer edge of the DO on either side the QR acorn on that side won't lock down. The reason is that the space under the acorn has to accommodate the spring. That's why the acorn has a ridge sticking up around the inner edge. The spring is a spiraling helix so that it compresses flat into a single layer of wire. If you have too much axle sticking out past the edge of the DO that axle length plus the spring thickness will exceed the depth of the cavity under the acorn. When you clamp the QR lever down it will seem to get tight but will tightened against the axle on that side instead of against the DO.

One more thing. The reason those "new old" hubs were a problem is that someone had moved a spacer from the right to the left while re-packing the bearings. I can only guess why, maybe to get less dish while using a 5-speed freewheel in 6-speed spacing. Anyway, I had to move the spacer back. You never know what a previous owner might have done.

Once you spread the stays, the drop-outs will not be parallel. the rear will be further apart than the front. You can correct this (difficult, but doable) or you can ignore it. If you ignore it, you run the risk of breaking the rear axle, as the clamping of the axle between non-parallel drop-outs introduces a bending force. Going from 120mm to 126mm may not be a problem, but any more and you are likely to have the axle break over time, especially with a cluster hub, whose bearings are closer together than a cassette hub.

The amount of axle that sticks out past the lock nut is not critical. If there is enough to keep the hub centered in the slot, but not so much that it protrudes past the outside vertical face of the drop-out, it'll work fine. The clamping force of the QR is what resists the forces trying to move the wheel relative to the frame: not the contact between the axle and drop-outs.

I also changed freewheels to get lower gearing on a 1988 Bianchi with 126 mm Campy Chorus hubs. Although an IRD 7 speed 13-32T freewheel JUST fit, when the chain was on the 13 tooth cog, the chain pins were was so close to the stays that I'm not sure I could have gotten a sheet of paper between chain and frame. In contrast, a 6 speed Shimano hyperglide freewheel (14-34T) had less overall width than the 7 speed freewheel, gave comfortable clearance from the frame, provided a lower overall gear, and also shifted better than a 7 speed freewheel with the original Campy Chorus derailleur. I now stick with 6 speed, standard spaced freewheels if I am trying to get low gearing on 126 mm hubs.

Among my loose bits I have one (just one) old-fashioned Campy locknut that is 3.5 mm thick and two Shimano locknuts that are 4.5 and 5 mm thick. All these have six hex wrench flats, not the two-slot cone-wrench type that you have now (and that I have in my hubs in service.) The Shimano nuts are 1-mm thread pitch, not the 26 TPI that Campy uses but they will thread onto a Campy axle without binding because only 4-5 threads are engaged. (I just checked.) Note that Shimano cones, being thicker, will NOT thread on. I can mail them to you if you like, gratis, just p.m. me. With the three thinner locknuts to mix and match with your own 7-mm ones you might be able to put something together. For 7 speeds, you should really try to make it fit in 126 mm. It really helps if you have a drawer full of hub spacers salvaged from years of working on bikes -- you'd be welcome to come over and paw through mine to find a combo that will fit but it is a trial-and-error process for sure.

To help understand why you're having trouble with what seems like a standard Campy hub, I'd like to see a photo of your hub (showing all the spacers installed) and freewheel side by side....but I'll still send you the locknuts anyway.

Ok. I surrender, and will go back to my 12-24 Regina 7 speed instead of the new Sachs. That said, I've learned I need to square up my dropouts after spreading the forks to avoid stress on the axle. But the question I still have is this.....is there a source of 10mm x 26 tpi locknuts of a thickness less than 7 mm? I understand that the existing locknuts are typical of this vintage hub, but my issues would be solved w a skinnier locknut. Do they exist? Does anyone know where they can be purchased? Thanks.

To Conspiratemus,

I am a junior member, and do not have PM rights yet. I do not know how to contact you offline, and do not want to violate any protocols by just posting my email address here. I sure would like to take you up on your offer of a skinny locknut. Thanks.

Hi Lakeboy: e-mail sent as you requested. Cheers.

Thank you
 

My sincere thanks to conspiratemus1 who dug into his spare parts bin and found not one but 3 narrow Campy lock nuts, and mailed them to me as a goodwill gesture. That did the trick, and my spacing problem is a thing of the past. Thank you, thank you.

You're most welcome. So glad it worked.
And thank you for the public thanks.
Best wishes.