Rare parts and strange setup compatibility question
 

Hi guys,
I came across a Bridgestone City Limit, equipped with a 6-speed Hyperglide cassette.
Yes, 6-speed. Yes, Hyperglide, not Uni-glide. Splined lockring. No smallest threaded cog.
This is rare enough in it's own right, but looking at the shifter is where it gets real odd - the shifter has six clicks.
So what's up with that?
In a stock set-up, number of clicks in the shifter would be one less than the number of sprockets.
And if this is a 7-speed shifter, how come it's indexing nicely on the 6-speed cassette?
Does it use a shorter body than the 7-speed, just like 7- speed uses a shorter body than 8/9/10-speed?

Any experience would be appreciated.

Consult Sheldon Brown. The spacing between cogs on 6 and 7 spd freewheels and cassettes are pretty much the same within the same brand. If you try to mix Shimano and Suntour you'll run into issues, though. I've tried in the past. A lot of old indexed shifters are compatible with both 6 and 7 spd freewheels and cassettes. The limit screws on your derailer will define the range of motion that the shifters are allowed to operate within. A lot of old indexed shifters will have that hidden click at the end that will allow you to index 7 speeds. It's like finding that super secret hidden song at the end of the CD that isn't listed on the back of the CD case.

+1, I've used an 8s lever with a 7s setup for years with no issues. However 6s and 7s are different spacing, unless the 6s is what used to be called "ultra 6" or similar, namely a 6s cluster spaced the same as 7s to work with 120mm hubs. (I don't know if they did this with wider hubs).

Take quick measurement of the cassette overall width or the sprocket to sprocket spacing and the mystery will resolve.

In any case if it works, you shouldn't care about the extra click. With a bit of creativity, you might use it to advantage by making a chain hanger and using it to shift onto it for wheel removal a la the short lived Campagnolo system.

Probably right. I was thinking about my experience with a 7spd freehub setup in a frame with 126mm dropouts in the rear and various friction setups on other bikes. I ran with Suntour shifters with a Shimano cassette on my commuter for over a year. It was noisy only in a few of the gears but it was overall still very functional.

Had another poke around and is still intrigued. I took a 7-speed cassette and held it to the 6-speed.
If I line the cassettes up small-to-big(for easy visible comparison) by the time I reach the 5th sprocket, the 7-speed is entirely "inside" the 6-speed sprocket.
Can't imagine that this shifter + derailer would index cleanly on a 7-speed system on more than a few sprockets at a time. The specs - which state 5.5 vs 5.0 mm spacing - certainly match the visible impression.
It seems possible that a 7-speed standard Shimano cassette would fit the freehub body, although I haven't tried it. A 7-speed ought to be wider than a 6-speed, but I'm not seeing any obvious spacers taking up room on the freehub body.
The use of that extra click in the shifter still eludes me. Maybe a derailer with a different amount of pull would let it run a 7-speed cassette.
Or it's like that "ghost shift" bug/feature some DT shifters had.

Shimano's thumb shifters, early on, had a "spare" click after the low gear position. Some used this as a 7th index click in an attempt to have one more gear then designed. Like much of the mix and almost match home brewed systems it had debatable success. Andy.

I thin you've nailed it, as this is a thumb shifter.
Although, by the feel of the shifter, it's the 1st - the "high" gear position, that's a bit different from the rest. The detent feels shallower, if that makes any sense.

Detents wear, or at least they can get less distinctive with use. It's common for many bikes to be ridden in the rear small cog much of the time, if that was the case then MANY of the shifting was into or out of the high position. Also that ghost detent I referenced is less a detent then an over movement of the lever. Andy.