grahamtillotson

Hi all -- could use some thoughts and experience on cold setting the rear dropouts on an old Trek 850 mountain bike frame from 135 mm to 120 mm. The idea I'm after is to build a wheel with a Sturmey Archer 8-speed IGH and use the bike for commuting, but the spacing on the Sturmey Archer hub is 120 mm.

Is it possible to use the "threaded rod and bolt/washer" approach to compress the stays to get the spacing down to 120 mm? Just wondering if anyone has done this with a chromoly frame and if it has an impact on strength.

Graham

Andrew R Stewart 

Yes, cold setting works in both directions. It's just far more common to widen the rear end but narrowing it is actually easier, IMO. If anything the chance of a broken joint (unlikely on a well made frame anyway) is less.

Suggestions- Have the wheel built up and on hand to act as the gauge. Double check the axle's fit within the dropout slots WRT the anti rotation (tabbed) washers and axle nuts having enough engagement with the axle. I like to secure the frame in a big bench vice, better to fine tune who far you bend things. Installing a bare axle (or a length of all thread) in the drop outs but only clamping on one side will allow the amount of bending and spring back to be tracked as the free dropout will "slide" along the axle, masking tape works as an indicator of how far to go. Don't forget to realign the dropout surfaces WRT each other ("H" tools). And whatever you do DON"T hack off any der hanger as you might want to go back to a der geared set up sometime in the future. Andy

unterhausen

I rebuilt my SA hub with a wider axle.

grahamtillotson

Fantastic! Really appreciate the fast responses.

@unterhausen -- I'll be using a new 8-speed IGH (the model without a brake). Did you replace the axle on a new model, and if so where did you source it?

For this build I'll probably set the frame since it costs less than a new axle + shipping ;-).

Graham

zze86

Are the axles not long enough to just add spacers between the dropouts?

I have a bike with 135OLD dropouts using Nexus7 130OLD hub and some washers on either side. Don't know if your axles are long enough to accommodate a 15mm difference with enough threads to properly secure the wheel though.

grahamtillotson

Brilliant -- I'll give that a try first. The washer idea would also help adjust for the chain line if the axle is long enough.

Graham

zze86

Yep, exactly. Although with 15mm to make up for you may just want to add a nut to both sides then fine tune the chain line with washers.

unterhausen

I have a classic UK-built SA hub. Wasn't thinking about the fact that there is still a business calling themselves SA

Andrew R Stewart 

SA was bought by Sun Race (IIRC) and production moved to Asia. At first the products were rehashed AWs and such but these days the stuff is pretty current. I have a RX-RK5 built into a 559 rim for my next errand/night time bike. But in my usual over the top style it's my first disk frame and will have self made lugs. So that will take another year+ to finish. Andy

unterhausen

I have heard that the current SA has only a faint resemblance to the old SA -- because the new hubs actually work

My dad rode a 3 speed Hercules to work for many years. One day he came home having suffered a face plant. I was always impressed that he just ordered the rebuild parts from Montgomery Ward and fixed it himself.

Andrew R Stewart 

Eris- I take that you're being funny in suggesting that the new hubs "work" better then the old ones. The AW is one of the most proven bike component ever. How many millions have been produces with only tiny changes over the decades? From what I read of the new hubs and issues on line VS the numbers of them out in use makes me think the new ones are no where near what the old ones were. But that's one reason I wish to try one (and the chance to build a disk specific frame/fork). Andy

zze86

Don't know if you got to working on this but I just remembered a suggestion from @fietsbob: if there is enough axle and space in between the dropouts flip the centering/lock nut and put them inside of the dropouts, then fine tune with a couple washers.

grahamtillotson

Thanks all for the replies -- gave it a test this weekend and I can definitely space out the gaps with washers and fine tune it once I get the wheel built. Will post some photos when I have it all built out.

Graham

violini

I have the same problem with my Ti recumbent frame. It's a front wheel drive, but the frame builder made the rear drop outs opening 132 mm. I am using an old 700C rear wheel with free wheel removed.
I tried to compress the stays to 95mm, but it sprung back to the original upon releasing the pressure.

Andrew R Stewart 

TI is well known for it's significant spring back. But curious to more details about the rear wheel that you're wanting to use. Andy

Andrew R Stewart 

There have been cartridge bearinged hubs with common threaded axle. I would use one of them (and I suspect there's at least one US hub maker that could be a possible source of an one off). Respacing a threaded axle is simple and requires no non reversible actions. Andy