I’m ignorant of this kind of stuff but can I easily-ish build a 4 speed freewheel? My Legnano originally had a 4 speed freewheel and the 5 speed on it now doesn’t allow the chain to go to the smallest cog because of frame interference. I could “possibly” space the axle but I’m wondering if going to 1 less cog would be more elegant than having an unusable cog whirling away.

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four speed gear blocks were quite common from the 1930's through the 1950's

one thing you might wish to verify before making any further changes is whether or not you have a drive train for 1/8" dentition or one for 3/32"

appreciate this may sound a bit odd but Italy did do five speed 1/8" drive trains at least as late as the early 1970's. Regina produced gear blocks for them. unsure if Everest/CAIMI did as well...

four speed gear blocks are readily available online

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I looked for 4 speed clusters on the ‘bay but all were old and unknown condition. Expanding my search....

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if you check the euro bays you should find a good selection

if you are open to purchasing from there you could also check the site subito.it

and no language barrier if you wish to communicate with Hilary Stone

https://www.hilarystone.com/

two other UK purveyors of vintage parts:

https://www.vintagevelo.co.uk/

https://www.isambards.co.uk/components/vintage

all best wishes with the Leggy


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Remove the smallest cog and Bob's yer uncle.

And in reality, that was Regina's mo back in the day.

Also, a 4 speed has a 114mm spacing. If your bike is 120, it should fit a 5.

Those Regina G.S. Corse 5-speed freewheels were built on a 4-speed body, with the fifth sprocket piggy-backed onto the fourth sprocket rather than threaded onto the freewheel body itself. Remove the smallest sprocket, and you're left with a 4-speed block.

Other options include using a 5 speed Atom and 5 speed Maillard freewheels which thread the smallest sprocket onto the second smallest which in turn threads to the body.

SunTour Perfect 5-speed freewheels also thread the last two cogs and should still be available. I have several. Lose the smallest and ride.

I don't believe a Perfect or ProCompe 5 speed body would work to create the OP's 4 speed freewheel. The two smallest sprockets both thread to the body. Thus the body is as "tall" as the entire stack of sprockets. This is also the case for early Shimano 5 speed freewheels.

From left to right: Perfect/ProCompe 6 speed standard body, 6 speed Ultra Spaced body, 5 speed body. It can be seen that in the case of the 6 speed versions the added sprocket is a splined and not threaded version.

That's what I tell my sons, because my brother's name is Robert.

Y’all are a wealth of knowledge! My concern was width relative to frame spacing. I’ve been wrenching on several bikes lately and the Leggy isn’t in front of me but I think it is 115mm spacing. I’ll check the existing FW and see if I can work with it.

Again, thx all!

Bob, here's a photo (2nd attempt, I am a horrible photographer) of a 4-speed freewheel I grabbed from the parts boxes; I used it in my 1st attempt to use a 543, back in the 1970's. Maybe just enough miles to remove some cog paint It was NIB when I got it. I see the outer removable race is flush with the outer cog, but the removal-tool boss projects a good 1/8" beyond that. Maybe it would fit James' bike... no idea of threading, but it's a 14-to-20T, best suited for rides that are all various grades of downhill. Unsure if anyone could rework it to "sane" tooth count. Anyway, here it is.

tiger1964 that looks like an Atom freewheel, but I could be mistaken. The flange on the inner body where the removal tool fits might be too tall for the spacing, but it is worth a try. If an Atom, Regina sprockets should be swappable.

Aye, that it is; an Atom. However, no model/threading markings. I found SGDG markings but a quick search reveals it is just French for "Brevetti", so no help there. I would certainly ""donate" the freewheel "to the cause" but if there is no one to re-cog it...??? Who, for crying out loud, wants a 20T low cog?

Is it possible to make up a 3-speed traditional British


threaded freewheel with a much larger low speed cog than the 24T I am seeing? Were there compact (Ultra-spacing) 4-speed freewheels made that fit on traditional space 3 speed bodies?
The bicycle in question is a 3-speed 1948 Gillott usingt a Simplex bell crank changer.

3-speed freewheels are for a 1/8 chain and are typically for a 114mm rear spacing. 4-speed freewheels are for a 3/32 chain (same as 5-8 speeds) and are also typically for a 114mm rear spacing. There is no such thing as a compact, ultra-spacing 4-speed freewheel.

As for the question, can you put 4-speed cogs on to a 3-speed freewheel body? For Italian freewheels like Regina and Caimi, no, you cannot. I can't say for other manufacturers.

As for putting a larger than 24 cog, probably yes, but depends entirely on the rear derailleur used for how much larger than 24 you can go. I have no clue how much larger your Simplex can go.

I needed lower gearing than the 14-20t and 50/47t on my early-50's E. Christophe, and as the original chainset was fully amenable to use with a narrow, modern chain, I cobbled up an Ultra-5 freewheel based on a (slightly modified) Shimano UG Z-series 5s freewheel.

This gave me five speeds within the travel range of the original Simplex 4s Tour de France derailer.

The body modification as I recall involved a slight shortening of the large-form cog interface on the outer body, where the largest three cogs spline onto. I did this on an as-needed basis (to get the 2-3 position spacer to move inward), no precision lathe cutting but just using a grinder and Dremel.
I probably could have more-easily just expanded one of the steel, small-form spacers from a Dura-Ace 7s freewheel over the full large-form spline, but which would have left a large open gap in the spacer, which wouldn't really have been an issue.
Note that the "2-3" spacer I refer to is the one between the second and third smallest cogs.

I got the TDF derailer to play quite nice with my bigger, 14-24t "U-5" freewheel. The UG cog teeth really help with smooth shifting (keeping the shifting response decently "early" even using the flexible modern 7s chain).

Note that many 4s freewheels to be found these days will have French threading.

I presume THAT is not said often...

And don't forget my bike's "small" 47t chainring.

Relative to our foothills topography, not very small!