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Removing Sturmey spacers: Internal gear hub for 157mm frame?

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Removing Sturmey spacers: Internal gear hub for 157mm frame?

Old 06-26-22, 08:48 PM
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Estuche
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Removing Sturmey spacers: Internal gear hub for 157mm frame?

Hello, I cannot find an IGH that will fit a 157mm frame. I noticed Sturmey Archer has a fatbike-specific hub:
https://www.sturmey-archer.com/en/pr.../detail/sx-rk3

It seems like I can adapt the fatbike hub to ~157mm. Based on the specs:
https://www.sturmey-archer.com/files...20IGH%20SX.pdf

That fatbike hub has a 170mm o.l.d., which is produced by the use of one 6.4mm and two 4.8mm cone lock-nuts:
https://www.sturmey-archer.com/files...3%20SX-RK3.pdf

If I remove the 6.4mm locknut, and replace the two 4.8mm ones with 2mm ones, that would get the disc hub down to ~158mm (170 - 6.4 - 5.6).

Do y'all see any risks of going through with this?
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Old 06-27-22, 05:01 PM
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I've added more and/or thicker nuts and sub in thinner ones to match a Sturmey's OLD to a bike's. But I've never done anything quite like this.

The thinnest Sturmey-Archer 13/32 x 26tpi axle nut I know of is the HMN132 that's 3.2mm thick.

A 2mm thick axle nut - real world - will have less than two full threads, which is below the old engineering rule of thumb.
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Old 06-27-22, 05:26 PM
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I may be way off base. So, feel free to discount or correct anything I have written here.

AFAIK the centering of the axle in the hub is critical to proper gear alignment. Whatever is done with axle spacers, cones, etc...the original position of the axle must be maintained. So you can not just pull a bunch of spacers & "move everything to the left" like on a standard non-IGH hub.

My next concern is proper pull-chain length and how the axle nut will be much more inboard than Sturmey Archers engineers have intended. Will you be able to see the yellow indicator witness mark? Will it even matter?

What about the disc rotor placement? You may very well pull the axle spacers to get the hub shell to fit in the frame. But, then find the rotor hits where it should not or be beyond the adjustment range of any brake mount or caliper.

This is just off the top of my head. I'm sure other more knowledgeable people will have better know-how.
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Old 06-30-22, 07:57 PM
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Very insightful, thank you both,
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