Is it possible to turn an old(80s) rigid mtb with 130mm rear spacing into a 1xWhatever without cold setting? Any parts suggestions? Tips and/or tricks? Haven't stumbled across a thread discussing this type of thing, so maybe this will help some adventurous tinkerers. Figured, before one starts down the rabbit hole, BF is the resource. I'm looking for a non-disc, 130mm bolt on 9-11 speed rear hub.

1/xx

Put wheel in bike with casette you want
Remove unwanted chainrings
Remove unwanted derailleur
Remove unwanted shifter
Use chain appropriate for cassette
??Profit

135 will fit in 130 frame with a bit of muscle, new wide narrow chainring or keeper if you drop chains.

Thanks Germany_chris

I forgot to mention that the current hub I'm working with has a 7-speed freewheel attached. It is an old 3x7 that I'm running 1x7 for now with a narrow-wide chainring up front. FD and shifter are currently at peace in the parts bin. Wish it were easy as swapping a cassette.

Assuming steel frame, I’d just squeeze the 135 hub in there. I’ve used 130 mm spaced rear hubs on 126 mm rear spaced frames without cold setting, although a few people frown upon this. I’ve been riding my Merckx Century a few years this way. You can also consider just using a 130 mm road hub.

A couple of thoughts -

If you choose to use a 135 hub without cold setting (and realigning the dropouts afterwards) the dropout faces will be slightly misaligned and engagement of the QRs and locknuts will suffer as a result. With horizontal dropouts, the wheel can slip forward under load. This happened to me on my ‘87 High Sierra, which was spaced 130 from the factory for a 6 speed hub, but came to me with a cheap 135 replacement wheel. I was standing and grinding uphill when it happened. The bike came to a dead stop, and the wheel went up into my fender and bent it a little. Fortunately I was able to dismount without incident, but it could have been messy. I am over 200 pounds which didn’t help any.

That said, it will be much easier to find a 135 26” wheel with the freehub you want, unless you’re going to lace the wheel yourself. Many 135 spaced wheels can be respaced to 130 by shortening or replacing the axle and losing some spacers. The rim will have to be re-dished if you go this route.

Cold setting the frame is pretty straight forward, you should use clamps to hold the stays onto the brake and chains stay bridges when you bend the rear triangle wider so the force of bending the stays isn't taken by the welds/brazing.

https://www.sheldonbrown.com/frame-spacing.html

lace a 26" rim to a new shimano road hub.

If the 7-speed hub is Shimano, you may be able to just swap the freehub body. I've done this and it was pretty easy, though it may have involved a slight redishing of the wheel.

Otherwise, I'd build/have built a wheel with a road hub as others have suggested. Shimano road hubs are dirt cheap and extremely reliable.