Uniglide and Hyperglide compatibility
I've been reading about how Shimano's 10-speed MTB rear derailleurs are not compatible with their 10-speed (STI) road shifters. This affects those of us who prefer to use lower gears on our road bikes rather than grind our way up hills. It reminded me of when I had a pair of wheels built in the early 90s for my touring bike. Shimano had just gone over to some fancy system on their cassettes called Hyperglide. Previously, their cassettes were called Uniglide. My wheels were built on a Shimano Deore DX hub with, it seems, a Uniglide compatible Hyperglide freehub. Apparently, such freehub bodies are hard to come by these days.
I'm not sure whether you would describe my 90s freehub body as backward-compatible or future-proof. Anyway, this is an account of how I am upgrading my touring bike from a seven speed Uniglide cassette to eight speed by using a nine speed Hyperglide cassette.
Note: the following refers to a bike using non-indexed downtube shifters.
Shimano freehub bodies
When I bought my Raleigh Road Ace in the 1980s it came with a six speed Unglide cassette and Uniglide freehub body. The picture below shows equally spaced ramps around the body. Uniglide sprockets could slide on the the freehub body in any position. The cassette was held in place by the smallest sprocket which threaded on to the body. You would place the chain on the smallest sprocket and press down on the pedals to tighten up the sprocket on the freehub body. (You could disassemble the cassette by removing the three long bolts that threaded in to the second smallest sprocket.)
Fast-forward to the present and the modern Shimano cassette uses the Hyperglide system. One ramp or spline on the freehub body is narrower than the others and this places all the sprockets in a predetermined position in relation to each other. This is to optimise the cassette – supposedly allowing the Hyperglide sprockets to provide smoother shifting than was possible with the design of their Uniglide predecessors. (To dismantle the cassette, perhaps to customise it to give your preferred ratios, you have to drill, tap out or grind down the heads of the rivets that hold the sprockets together.) Notice the thread inside the body of the freehub where the cassette lock ring fits.
Between these two distinct systems was a brief period during which Shimano produced a freehub body that was compatible with both Uniglide and Hyperglide cassettes. Thinking about it now I wonder if I was sold an outmoded type of cassette when I bought two Ultegra cassettes from the shop that built my wheels. No matter. At the very worst it means I have another barely worn cassette that I may be able to fit to my Raleigh Road Ace to lower the gears and let me get up the steeper hills some miles from where I live.
Notice that there is the one narrow spline and the internal thread to allow fitting of a Hyperglide cassette, but also the external thread that allows the smallest sprocket of a Uniglide cassette to be fitted.
Seven, eight, nine and 10-speed Shimano cassettes
All of this information can be found at – and is better expressed by – Sheldon Brown online, but I found out for myself by tinkering about in the garage and wondering "what if?", which is ultimately more rewarding, I reckon.
Six, seven and eight speed cassettes will work with the same type of chain (eg HG40 or HG50). Things get a little more complicated with nine speed. For all I know an eight speed cassette will fit on my freehub body. Or maybe not. I've got one in stock, but I didn't want to use it for two simple reasons: the gears are too high and the gaps between them too wide. Also, I have been thinking about swapping out the Shimano Biopace chain set that I bought over twenty years ago. It has been discredited since its production, although I have stuck with it and I do feel it helps at lower speeds on stiff climbs. But in the past I suffered with a niggle on the lateral aspect of my left knee when riding the bike on which the components I have detailed here – my Coventry Eagle Touristique – are fitted. I have always wondered if that niggle was down to the chainset. I've ridden several hundred miles on the bike this year without complaint but the doubt always, well, niggled.
So, when a Deore LX square taper NOS chainset became available on my preferred online store I had to have one. It had 44/32/22 chain rings and with a large rear sprocket would give me a bottom gear in the teens (18.4 inches to be precise).
Thinking about it now I'm not sure which idea came first – cassette or chainset – but whichever it was you can't have one without the other: if you fit a nine speed cassette you need a nine speed (eg HG53) chain and this in theory could slip between the chainrings of the Biopace chainset. And an 6/7/8 speed chain would be too wide for the Deore LX chainset I just had to have. (I've also plucked from my stockpile a NOS Deore LX rear derailleur that will replace the current one. I didn't want to do way with the one I have, but one of the limit screws had rounded out the thread in the derailleur's housing and an overshift would drop the chain – especially a narrow one – between the large sprocket and the spokes on the rear wheel.)
This all seems a rather costly way of upgrading my Touristique, and I suppose it is. But for £81 I have lower gears with a narrow range between each of them. The top end is about 91 inches with a 13T sprocket (98 inches with a 12T – I haven't quite decided), quite a bit lower than on my other bikes, but ample for a touring bike. After all, it's at the bottom end where the gearing really matters when you are climbing with panniers full of gear. (See also bicycle gear inch calculator.)
Just as importantly in my mind is that I can ride around at my normal cruising speed on the large chain ring. I prefer to spin a gear in the mid or lower sixties and this set up gives me a 65 inch gear on the 18T rear sprocket. Either side of this I have a 56 inch gear on the 21T sprocket and 74 inches on the 16T using an 11(12)-32 MTB cassette. The 11(13)-34 cassette gives larger gaps between ratios and the nearest sprockets straddle the cruising gear I prefer.