Ghrumpy

The constraint is not the freewheel. It's the rear derailleur. Y'all might not have noticed that he's using a Juy 543. That's not likely to be usable with a 6s ultra, as they are about 2mm wider than a 5s. The 543 derailleur's not like parallelogram derailleurs where you can just turn a screw and get more travel, its travel is limited by the traverse rod and can't be made longer (without some surgery, which I doubt anyone would do to a 543.) 2mm ain't much but it might be too much.

Unless someone can verify they've successfully made a 543 work with a 6s ultra, I'd stick with a 5s freewheel.

ThermionicScott 

Maybe he could disassemble the freewheel and thin down the spacers a little to make an ultra-ultra-6.

tiger1964 

Didn't know that; glad I start this topic. Might be a good idea to procure one of each. At least I could report back and other users would at least know.

The derailleur stays even if I have to jettison one cog.

pastorbobnlnh 

Hahaha! Then you'd need to thin the chain, and in most cases extend the threads on the freewheel body, and lower the height, and/or build up the bottom base if the sprockets are splined, thin the chain rings and the sprockets, and on and on it goes! It would be quite the challenge, even for a master machinist!

@tiger1964, I've sent you a PM about the freewheels.

tiger1964 

indeed!

But wouldn't one of those chains intended for 7 or 8 speed freewheels or cassettes do the job? I'm running those on two bikes now, with 5-speed freewheels, and with original chainrings.

dddd

I wanted to stay with a 5s freewheel on my old Steyr because the Phil-hubbed wheelset I wanted to use wouldn't even come close to accepting an Ultra-6 freewheel, so I built up a 5s Uniglide as 13-15-17-20-24t to go with it's 52-36t cottered chainset.
It has a near-perfect spread of ratios for sporting riding here in the foothills, so is a great minimalist setup for me.

tiger1964 

Looks like a nice color match between the paint and the derailleur pulleys!

CliffordK

It would seem like you could snag one off of E-Bay easily enough:

Shimano 5s (oops 6s), 13-24 BIN $20 + 5

Regina Oro 6s, 13-24 ITALIAN, Auction, $20 + $8.75

NOS Suntour Winner Pro, 5s, 13-22, BIN $19+$9.75

Cami Castano 5s 13-23, ITALIAN, BIN $24.50 +$5

Suntour, 6s, listed as 12-24, but I count 13T, $9.99/$16 + $10.79 Auction/BIN

Sachs 7s 12-24 BIN $28 + $0

Thanks @dddd for catching the Shimano was 6s.

I suppose that brings us back to mostly 6s freewheels. Still potentially possible for the OP's bike, but a bit tighter of a fit. And, the one Italian 13/23 which would probably be fine, but with one less tooth than the OP had hoped for.

dddd

Beware of that Ebay "5s" Shimano Uniglide 13-24t freewheel, picture shows it's actually a 6s freewheel!


EDIT: Yeah, I would have been tempted to buy it, then saw that it was a 6-speed.
Perhaps not that hard though to build up the same one that I have using a couple of commonly-available Shimano freewheels, but I had loose cogs at hand so it was easy.

pastorbobnlnh 

As a point of information about stack height between a Shimano 5 speed and an Atom 77 Compact 6 speed: They are identical. I have a Shimano 600 UG five speed on hand to compare to the Atom 77 Compact 6 speed and there is no difference between the widths.

tiger1964 

Thanks and that's good news, I feared needing to ask myself if I had the courage to Dremel the derailleur to try to buy a couple more mm of "throw"