Re-spacing the rear axle

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Anglian
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Re-spacing the rear axle

Postby Anglian » 12 Dec 2012, 10:37am

Hello,

I'm trying to replace the rear (26", solid-axle) wheel on a bike with 130mm rear dropout spacing (the bike uses a six-speed freewheel, and is a perfectly adequate workhorse, more-or-less a hack bike).

The replacement wheel has an over-locknut distance (OLD) of 135mm, so I can get it into the frame with (quite) a bit of a struggle, but this situation is not ideal. It makes changing tyres or repairing tubes no fun at all.

Examining the wheel, I realized that the over-locknut distance is governed by the axle spacer on each side, between the cone and the locknut. The drive side has a 14mm spacer, the idle (non-drive) side a 12mm spacer, giving a total spacing of 26mm. Each spacer has an outer diameter of 15mm, and an inner diameter of 10mm.

It strikes me that if I can reduce the total spacing to 21mm, then the over-locknut distance will fall to 130mm, and I'll be able to insert and remove the wheel with ease, making repairs much less of a chore.

I could move the 12mm spacer I have to the drive side, and insert 9mm of spacing on the idle side. This cuts 2mm off the drive side, and 3mm off the idle side, which slightly changes the symmetry of the wheel. Will that be a problem in practice? Would I do better to take 3mm off the drive side, and 2mm off the idle side? That would mean I couldn't reuse the 12mm spacer, so the cost would rise.

Spacers seem moderately hard to find (I imagine this kind of "conversion" isn't done that often). I see Practical Cycles currently has some on its eBay shop, and they seem to be marketed for people fitting 130mm hubs into 135mm frames (that's the opposite of what I'm doing). They're priced per spacer, with sizes from 1mm to 5mm, plus 0.5mm, for the true perfectionist.

If 12mm plus 9mm will work, then I'll only need to buy a 5mm and a 4mm. If I got for 11mm plus 10mm, then I'll need to buy three 5mm and one 1mm spacers. However, the (small) extra cost will be worth it if it means a better chainline.

Can anyone please advise me on this conversion? Am I worrying too much about a non-issue?

One colleague suggested simple hacksawing off part of the 14mm spacer, but I'm not sure I can achieve the necessary accuracy, and I don't really have the tools. In any case, that would leave me with no easy way to return the wheel to 135mm spacing in the future, in the case where a 135mm-spaced frame is purchased.

I've read Sheldon Brown's page on cold-setting a frame, but why go to all that trouble and risk if I can just respace the over-locknut distance?

Many thanks.

Reference info: http://sheldonbrown.com/frame-spacing.html
Last edited by Anglian on 12 Dec 2012, 2:32pm, edited 1 time in total.

reohn2
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Re: Re-spacing the rear axle

Postby reohn2 » 12 Dec 2012, 11:02am

B&Q or hardware shops have a good selection of washers.Replace the 12mm on the none driveside with the appropriate number of washers to give 130mm spacing.Alternatively cut or grind 5mm off the 12mm spacer on the none driveside.
You may need to redish the wheel which is easily done with the wheel in the frame by slacking off the spokes on one side and tightening the other in half turn increments until the wheel is central in the frame.
The othe way is if the frame is steel,you can widen the OLN spacing perminently by a length of threaded rod,nuts and washers between the dropouts and winding out until the relaxed width is 135mm,you may need to widen the OLN to around 140mm to get the desired 135mm when not under tension.
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meic
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Re: Re-spacing the rear axle

Postby meic » 12 Dec 2012, 11:04am

I assume the new axle is also solid otherwise there could be axle length problems.

Does your drive side have enough clearance for a chain which is changing gear onto the smallest sprocket or driving that sprocket and the frame for you to reduce the drive side spacers?

I think that most people would not even notice that their rear wheel was 2mm off centre, while riding it.
If it is a cheap wheel then you probably will not make the wheel any worse by an amateurish re-dishing, just adjust every spoke on one side by the same amount, tightening will probably be best, until it is roughly central in the frame.
Yma o Hyd

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531colin
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Re: Re-spacing the rear axle

Postby 531colin » 12 Dec 2012, 11:45am

You have 3 things to consider...
Chain line
Wheel dish
indexing

Least wheel dish = strongest wheel, and happens when the top gear sprocket is as close as possible to the dropout
Chainline is usually best when the top sprocket is as close as possible to the dropout
Neither of the 2 above are millimeter-critical, and I wouldn't re-dish a wheel for the sake of a millimeter error with axle spacing.

Gear indexing is millimeter critical, but you are going to have to adjust that anyway.

If you are recognised as a regular customer at your LBS, the usual arrangement is you can scrounge a couple of spacers from the scrap bits box in exchange for 2 packets of chocolate biscuits... :wink:

Ayesha
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Re: Re-spacing the rear axle

Postby Ayesha » 12 Dec 2012, 12:28pm

The important distance is the inside face of the dropout to the shoulder where the freewheel or cassette closes up to on the hub. It should be such so a factory built replacement wheel with the same freewheel or cassette fits straight in and the rear mechanism does not need adjusting.

I rebuilt a Maillard Normandy rear hub, increasing it to 135 in order to fit a six speed freewheel. The bike's frame is still 130.
All I needed to know is the dimension described above, so my rebuilt hub was interchangable with a std hub of 135 width.

I also needed to develop a strong pair of thumbs to pull the rear triangle when slipping the 135 hub in.
Last edited by Ayesha on 12 Dec 2012, 12:34pm, edited 1 time in total.

Brucey
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Re: Re-spacing the rear axle

Postby Brucey » 12 Dec 2012, 12:33pm

Ayesha wrote:The important distance is the inside face of the dropout to the shoulder where the freewheel or cassette closes up to on the hub. It should be such so a factory built replacement wheel with the same freewheel or cassette fits straight in and the rear mechanism does not need adjusting.


in a dream World, yeah, maybe.... in the real World, unlikely. I wonder how many six speed 130mm OLN 'standard' wheels there are out there...

Its not as if all freewheels sit the same on the same hub even.

cheers
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breakwellmz
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Re: Re-spacing the rear axle

Postby breakwellmz » 12 Dec 2012, 12:59pm

HI.

Surely it LESS faff to spread the frame,non?

Ayesha
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Re: Re-spacing the rear axle

Postby Ayesha » 12 Dec 2012, 1:04pm

The aim is to build a wheel which is ‘as standard’, not a unique example.
Build the hub to the dimensions of a Standard wheel. Then you can borrow a wheel off your mate if you have a mishap.

The only time you need to juggle with washers is when replacement cones are different from the original cones.
Last edited by Ayesha on 12 Dec 2012, 1:06pm, edited 1 time in total.

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breakwellmz
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Re: Re-spacing the rear axle

Postby breakwellmz » 12 Dec 2012, 1:05pm

In the time since my last post,i`ve gone out to the shed,found a bit of timber and widened the back end of a frame i use as a wheel jig.

It really is that easy! :D

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georgew
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Re: Re-spacing the rear axle

Postby georgew » 12 Dec 2012, 1:35pm

breakwellmz wrote:In the time since my last post,i`ve gone out to the shed,found a bit of timber and widened the back end of a frame i use as a wheel jig.

It really is that easy! :D


OK. And has each drop-out been moved out by exactly the same amount?

If not then the wheel will not be equidistant in the drop-outs. When cold-setting a frame it's important that the frame is then checked for trueness.

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meic
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Re: Re-spacing the rear axle

Postby meic » 12 Dec 2012, 1:38pm

georgew wrote:
breakwellmz wrote:In the time since my last post,i`ve gone out to the shed,found a bit of timber and widened the back end of a frame i use as a wheel jig.

It really is that easy! :D


OK. And has each drop-out been moved out by exactly the same amount?

If not then the wheel will not be equidistant in the drop-outs. When cold-setting a frame it's important that the frame is then checked for trueness.


Is important really the right word to use here?
I would have said preferable. It is not as if anything major is going to happen if it is wrong.
Yma o Hyd

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531colin
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Re: Re-spacing the rear axle

Postby 531colin » 12 Dec 2012, 1:59pm

Ayesha wrote:The aim is to build a wheel which is ‘as standard’, not a unique example.
Build the hub to the dimensions of a Standard wheel. Then you can borrow a wheel off your mate if you have a mishap..........


Except its a 6 speed screw on 130mm 26" wheel.....I don't have one in my shed, who does?

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meic
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Re: Re-spacing the rear axle

Postby meic » 12 Dec 2012, 2:05pm

I have quite a few 6 speed, 130mm, 26" wheels in my garage, they are cassette type but no reason why they should not be interchangeable, except that I do have to adjust the rear dérailleur when I swap them around as I have not bothered shimming the cassettes.
As the three hubs were identical I am "pretty" certain it is the cassettes themselves to blame.
Yma o Hyd

Anglian
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Re: Re-spacing the rear axle

Postby Anglian » 12 Dec 2012, 2:10pm

reohn2 wrote:B&Q or hardware shops have a good selection of washers.Replace the 12mm on the none driveside with the appropriate number of washers to give 130mm spacing.Alternatively cut or grind 5mm off the 12mm spacer on the none driveside.
You may need to redish the wheel which is easily done with the wheel in the frame by slacking off the spokes on one side and tightening the other in half turn increments until the wheel is central in the frame.


Hello reohn2,

Thanks, that was quite a thought-provoking reply.

Currently, the 5mm-too-wide wheel is pushing out the rear triangles, presumably by approximately the same displacement each side (since they're roughtly the same strength). If the wheel is centred in the frame in this situation, then removing 2.5mm of spacing from each side (down to 130mm) would mean it should still be centred.

However, you're suggesting removing 5mm from one side only, which presumably moves the centre of the hub about 2.5mm away from its previous position, closer to the non-drive side dropout, meaning the wheel needs to be re-dished, so that the rim is moved away from the non-drive side to compensate for the shift in the hub's position. The sprockets, on the drive side of the wheel, will now also be displaced towards the non-drive side, meaning that the chain-line changes slightly.

I'm inferring (and perhaps I'm wrong) that you're suggesting this approach because you want to maintain the distance between the sprockets and the drive-side drop-out. I can see that it's important to have enough clearance here, but if there's enough clearance after removing 2.5mm (or 2mm, since I'm proposing swapping the 14mm spacer on the drive side for the 12mm one from the idle side) of spacing, then (approximately) symmetrical removal of spacing seems to be a technique which involes less work and adjustment (no re-dishing, minimal derailer adjustment).

Did I overlook something about your assymmetrical spacing-change proposal?

Anglian
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Re: Re-spacing the rear axle

Postby Anglian » 12 Dec 2012, 2:28pm

breakwellmz wrote:Surely it LESS faff to spread the frame,non?


Hello breakwellmz,

I don't think so.

Although I'm having to think about the consequences of respacing, and understand how various aspects of the bike's geometry will be affected, if it can be done this way, then I think it's not much work to unscrew the locknuts, replace the spacers with differently-sized ones, and refit the locknuts again. It just needs some appropriate wrenches.

The approach of cold-setting the bike frame to a wider spacing would require (if Sheldon Brown is to be believed) removing various bits of hardware from the bike frame (in particular the derailer), protecting the frame paintwork from scratching, then getting an appropriate lever, and applying force in a trial-and-error basis until the rear dropout distance is respaced (in a balanced way, same displacement on each side), then re-assembling. If I then needed to go back to the 130mm wheel which used to work on this frame, it would no longer fit.

The spacers seem to be on wheels so that the same hubs can be fitted to different frames, by changing them.

I appreciate that the situation for non-solid (that is, QR) axles is different, as meic pointed out above. in that case, axle length needs to be close to the dropout distance. However, for sold axles, and nutted wheels, it the OLD which counts, and the spacers offer an easy way to do that (presuming I can understand the geomterical consequences well enough).

Regards,
Anglian