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Old 09-30-12, 12:43 PM   #1
pstake
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126mm hub w/ 5 spd in 120mm frame (is this okay?)

I've been running a specialized sealed 126mm hub in my 75 Raleigh Grand Prix frame. This is my beater bike and the wheels are the most valuable thing on it, but I had them and they were not in use. My goal has been to maintain this bike without buying parts (except chains).

So, to do this, I mounted a 5 speed freewheel that I had available, and I'm running miss-matched friction shifters on the downtube.


My question is: Am I doing long-term damage to my hub by running the 126 spacing in a 120 frame? Does the 5 speed freewheel instead of 6 speed, matter?
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Old 09-30-12, 12:50 PM   #2
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You can reduce the over lock-nut width of the wheel, modify it.
or spread the frame wider , and still mod the hub and go up to #6 standard space.

or #7 a narrower space.. freewheel..

fixing a flat + having a struggle fitting the wheel back in is a PIA,
when the frame has to be pried apart, as well ..

frame is likely well over 35 years old so is already lucky to survive un-damaged this long ..

non parallel dropouts do cause an added stress on the axle and
may add to other stresses , and axle may break, but the axle can be replaced.

'speeds' is just how many cogs are there... It's the Ratio,
in combination with the chainrings that matter.

so count teeth numbers and do some math
to divide front by rear tooth numbers.
like 52)14 = 3.71428.. or 3.714:1

Last edited by fietsbob; 09-30-12 at 01:03 PM.
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Old 09-30-12, 12:53 PM   #3
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If I change the spacing, e.g. the over lock-nut width, wouldn't I need to re-dish?

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You can reduce the over lock-nut width of the wheel, modify it.
or spread the frame wider , and still mod the hub and go up to #6 standard space.

or #7 a narrower space.. freewheel..

fixing a flat + having a struggle fitting the wheel back in is a PIA,
when the frame has to be pried apart, as well ..

frame is likely over 20 years old so is already lucky to survive un-damaged this long
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Old 09-30-12, 01:50 PM   #4
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Just cold set the frame. It's steel and only 6mm. Then realign your dropouts if they need it.
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Old 09-30-12, 01:52 PM   #5
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I'd spread the frame and tweak the dropouts.

Or at the very least tweak the dropouts so they're parallel when you jam the wheel in. Which will make it slightly harder to jam the wheel in, but meh
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Old 09-30-12, 01:56 PM   #6
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Just cold set the frame. It's steel and only 6mm. Then realign your dropouts if they need it.
How can I tell if the dropouts need realigned? I realize they need to be parallel but is there a trick to it? Just use a square?

Thanks for the advice ... I don't mind cold-setting. It's a tough frame.
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Old 09-30-12, 01:58 PM   #7
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If I change the spacing, e.g. the over lock-nut width, wouldn't I need to re-dish?
Not if you reduce the same amount on each end of the axle. But you may have to cut the axle down too.
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Old 09-30-12, 02:04 PM   #8
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How can I tell if the dropouts need realigned? I realize they need to be parallel but is there a trick to it? Just use a square?
I use a big ole adjustable wrench and guess. It's like a couple of degrees or so; tweak it a little and it'll be happier.

I guess if you had a spare axle, you could clamp some bits onto it with locknuts to magnify any bend that showed when you clamped it in the frame...
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Old 09-30-12, 02:11 PM   #9
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This tool can be used, but if you know how it works I'm sure you could make your own. I have access to one because my dad use to own a bike shop and it is one of the tools he kept


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Old 09-30-12, 02:22 PM   #10
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...adjustable wrench and guess. It's like a couple of degrees or so
...
A couple degrees? I figure 6mm is about a quarter inch. So each side is being moved out only one eighth inch. And the chainstay is 15 inches long. So arctangent ( .125/15) = 0.5 degrees. Only one half of one degree.
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Old 09-30-12, 02:23 PM   #11
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Ride as is - but have the dropout alignments checked...

OR

Cold spread to 126mm and then check dropout alignments again...


...and yes, changing hub spacing will require re-dishing. Trying to wing it by removing even amounts may result in:

1. Possible chain line disturbance - or making poor chain line even worse. (In your case however you may end up making it better...)
2. Chain clearance issues with the seat stay while in the lowest cog. (Kinda doubt it though with a 5-speed on 6/7 freewheel spaced hub...)


If you are going to modify the hub for classic 120mm and 5-speed spacing:

A = Freewheel stop to end of drive side lock nut.

You want A = 29.00 Get this part right.

C = Outside lock nut to outside lock nut.

You want C = 120.00 - 122.00 Use the non-drive side to finish this spec - doesn't have to be perfect.


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Old 09-30-12, 02:49 PM   #12
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Quote:
Originally Posted by mike6024 View Post
A couple degrees? I figure 6mm is about a quarter inch. So each side is being moved out only one eighth inch. And the chainstay is 15 inches long. So arctangent ( .125/15) = 0.5 degrees. Only one half of one degree.
Trigonometry's a fine thing

But I'd say my guess of how many degrees we're talking is a lot worse than how I'd eye it up.
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Old 09-30-12, 05:26 PM   #13
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Quote:
Originally Posted by pstake View Post
How can I tell if the dropouts need realigned? I realize they need to be parallel but is there a trick to it? Just use a square?

Thanks for the advice ... I don't mind cold-setting. It's a tough frame.
The best way is to bring the frame to your LBS and let them use their dropout alignment tools:

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Old 09-30-12, 09:08 PM   #14
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If the dropouts are not parallel, they are close enough that I can't readily perceive it by looking.

So is a .5-degree change enough to damage my hubs?

It's not terribly difficult to get the wheel in and out. I've put 130 hubs in 126 frames before, which required more effort.

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A couple degrees? I figure 6mm is about a quarter inch. So each side is being moved out only one eighth inch. And the chainstay is 15 inches long. So arctangent ( .125/15) = 0.5 degrees. Only one half of one degree.
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Old 09-30-12, 09:15 PM   #15
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I wouldn't recommend it... but I've dropped a 130 wheel in a frame to cold set it o 126...
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Old 10-01-12, 12:18 AM   #16
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If the dropouts are not parallel, they are close enough that I can't readily perceive it by looking.
Yes, a half of one degree is just about nothing as far as I'm concerned. I have no bike mechanic credentials. You would not even consider just trying to bend it with wrench to correct it because you would bend it too far in the other direction. Cannot perceive it in the first place as you noted. Uneven paint thickness on the dropout probably would cause more than a half degree. Doubt a shop could guarantee accuracy of alignment of less than half a degree with special tolls, but you could ask them because I really don't know.

BTW I have done just what you have done with no problem. Had a 15 speed Univega with 120mm and 5 speed freewheel. Hub was cracking around spoke holes. Bought a new hubs (Campy!) to build myself new set of wheels. Didn't even realize it was longer (126mm) till after I bought them as I was not very aware of those type issues being new to working on bikes. Just have to pull a bit every time I have to put the wheel back on after changing a flat. No big deal.

I removed 3mm spacers from the freewheel side and added those 3mm to the other side. You can cut the spacers on the freewheel side if you are going to use a 5 speed on a 126mm hub because those are meant for 6 speed freewheels. Better thing to have done would have been to remove those 3mm from the freewheel side and NOT add them to the other side, and instead cut 3mm off the axle, then you would have a 123mm hub, so you would be spreading the chainstays almost not at all. I think that's what I would have done if I had been thinking more clearly.
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Old 10-01-12, 12:41 AM   #17
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Yes, a half of one degree is just about nothing as far as I'm concerned. I have no bike mechanic credentials. You would not even consider just trying to bend it with wrench to correct it because you would bend it too far in the other direction. Cannot perceive it in the first place as you noted. Uneven paint thickness on the dropout probably would cause more than a half degree. Doubt a shop could guarantee accuracy of alignment of less than half a degree with special tolls, but you could ask them because I really don't know.

BTW I have done just what you have done with no problem. Had a 15 speed Univega with 120mm and 5 speed freewheel. Hub was cracking around spoke holes. Bought a new hubs (Campy!) to build myself new set of wheels. Didn't even realize it was longer (126mm) till after I bought them as I was not very aware of those type issues being new to working on bikes. Just have to pull a bit every time I have to put the wheel back on after changing a flat. No big deal.

I removed 3mm spacers from the freewheel side and added those 3mm to the other side. You can cut the spacers on the freewheel side if you are going to use a 5 speed on a 126mm hub because those are meant for 6 speed freewheels. Better thing to have done would have been to remove those 3mm from the freewheel side and NOT add them to the other side, and instead cut 3mm off the axle, then you would have a 123mm hub, so you would be spreading the chainstays almost not at all. I think that's what I would have done if I had been thinking more clearly.
See post #11

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Old 10-01-12, 12:56 AM   #18
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From post #11
"If you are going to modify the hub for classic 120mm and 5-speed spacing:

A = Freewheel stop to end of drive side lock nut.

You want A = 29.00 Get this part right.

C = Outside lock nut to outside lock nut.

You want C = 120.00 - 122.00 Use the non-drive side to finish this spec - doesn't have to be perfect."

Well I think I have built about 4 wheels total in my lifetime thus far so you have built about 3000 more than I at his point.

My distance A probably is about 29.00 as you suggest but I would have to take the freewheel off to check it.

"Freewheel stop to end of drive side lock nut" is what I set to be equal to what the original hub I was replacing was, and i did that, best as I recall, by removing 3mm, so it might just be that I ended up with 29mm but it has been a while. I did not set it to 29, but I set it to be about what the original hub was, which, based on your comments, probably was about 29 being an original 120mm 5 speed.

Removing spacers from the drive side reduces dish and makes for a stronger wheel. Adding to the left does the same thing.
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Old 10-01-12, 01:20 AM   #19
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Quote:
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Yes, a half of one degree is just about nothing as far as I'm concerned. I have no bike mechanic credentials. You would not even consider just trying to bend it with wrench to correct it because you would bend it too far in the other direction. Cannot perceive it in the first place as you noted. Uneven paint thickness on the dropout probably would cause more than a half degree. Doubt a shop could guarantee accuracy of alignment of less than half a degree with special tolls, but you could ask them because I really don't know.
IMO all of that is wrong. 0.5 is more than you might imagine:

I can tweak that straighter by eye.

And the paint doesn't matter a damn because the knurling on locknuts bites right through it.
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Old 10-01-12, 07:31 AM   #20
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Re: having the dropout alignments checked ...

Does it sound bad to say that I don't trust any of the local bike shops to do this?

They seem usually more interested in telling me what's wrong with riding old bikes than in selling me parts or tools. Makes me a little paranoid that they won't do the simple repair (align dropouts, that I request)

Sad but true.

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See post #11

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Old 10-01-12, 09:10 AM   #21
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Lots of shop guys are just arrogant ****** who are only interested in parting you from your cash, sad to say... oh, and fraudulently posing as experts.

You'll know a cool shop and a real expert when you find one pretty quick, if you walk in with an interesting old bike.

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Old 10-01-12, 09:32 AM   #22
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You are being advised to make a big deal out of nothing. The quick release skewer puts the whole axle into compression. That is one of the main features of a hollow axle compare to a solid one. Tighten the skewer more if you are concerned. Tightening the skewer effectively strengthens the axle. Of course shops don't want to waste their time on nonsense like this. I have no axle problem as far a I know, doing the same thing you are and using the bike for many years. I would expect a bent axle if I got one to come from carrying weight on the rack and hitting sharp bumps in the road, not dropouts causing it.
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Old 10-01-12, 09:38 AM   #23
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Thanks, Mike.

I'm not so worried about breaking an axle. I am more worried that uneven pressure is being exerted on the cartridge bearings, causing them to wear out faster. I'm no engineer but it seems like it wouldn't take much unevenness to affect the bearings.

I think that, by nature of the design, cup and cone hubs would give more leeway in this situation.

Again, I'm not an engineer, so I'm just guessing. And I intend to keep these wheels, or at least the hubs, for a good long while ... so I don't want to trash them by being careless.

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You are being advised to make a big deal out of nothing. The quick release skewer puts the whole axle into compression. That is one of the main features of a hollow axle compare to a solid one. Tighten the skewer more if you are concerned. Tightening the skewer effectively strengthens the axle. Of course shops don't want to waste their time on nonsense like this. I have no axle problem as far a I know, doing the same thing you are and using the bike for many years. I would expect a bent axle if I got one to come from carrying weight on the rack and hitting sharp bumps in the road, not dropouts causing it.
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Old 10-01-12, 09:43 AM   #24
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I'm no engineer but it seems like it wouldn't take much unevenness to affect the bearings.

I think that, by nature of the design, cup and cone hubs would give more leeway in this situation.
This is why I think it's worth the minimal effort to sort it; even cup and cone bearings require precision to maximise durability. I've seen plenty of cones with an uneven groove worn into them from just this.

I wouldn't call one little tweak, once, to ensure it works as designed, a big deal.
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Old 10-01-12, 09:51 AM   #25
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Well ... it's a 1975 Nottingham (read: Raleigh proprietary) Grand Prix, with SR cotterless cranks, power-shifter on the right downtube, Lepree friction on the left, modern 105 front der, 300 ex rear der, cyclops brakes with homemade drop bolts and 700c wheels, and a knockoff brooks pleather saddle. All in blue, with a matching blue blackburn rear rack. (freewheel and rear der have been changed since this pic was taken; springs in the rear der were just too worn out)

But maybe it's not an interesting old bike?

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Lots of shop guys are just arrogant ****** who are only interested in parting you from your cash, sad to say... oh, and fraudulently posing as experts.

You'll know a cool shop and a real expert when you find one pretty quick, if you walk in with an interesting old bike.
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