I just bought what I believe is either an Exage or RSX rear hub and it's my first freehub. Going onto what is currently a 6 speed frame, will I have any problems with a 7 speed cassette? From what I've read the freehub has capacity for it and I know the spacing is 126 which is correct for my frame. Basically I lack the understanding of how you can fit an extra cog in the same space with the same width chain (current chain is like new and 3/32 wide.).

Additionally, if anyone could point me towards a 13-26/28 cassette I'd appreciate it. I've seen 14-28 HG online and I might do that rather than paying vintage prices on eBay for UG.

Thanks

13-28t 7s was a popular choice, as were 13-26t and 12-28t, all in 7s (narrower-spaced) format.

7s spacing requires use of "narrow" chain, 7.3mm max.
The older (standard-spaced) 6s freewheels used wider chain, roughly 8mm wide.

The 7s freehub adjusts all of the dimensions to accomodate the wider 7s cassette, and can still (with the 7s cassette) easily be narrowed to 124mm just by removing a 1mm washer from each end of the axle assembly. The resulting 124mm hub fits without much effort into older 120 and 121mm frames (my old 5/10s Peugeots measure 121mm).

You need to look up the model of the hub on Velobase before you buy a cassette. HG and UG do work together. If it is UG, your best option is to buy a 7 speed HG freehub body and put it on the freehub, then purchase a cassette. There is lot of info on this site as well as the web on how to do that.

Careful shopping, any Shimano 14-28 7-speed you see online is likely to be a freewheel, not a cassette. This 12-28 should work (I think RSX was Hyperglide-only): https://www.amazon.com/SHIMANO-Speed...dp/B007Y5HFWU/

Unfortunately, Shimano has stopped making upper-level 7-speed cassettes, so you're not likely to find much except for inexpensive 11-28/12-28/12-32 unless you search for old stock.

I'll be sure to avoid a freewheel.
This hub takes both Hyperglide and Uniglide. I thought RSX had a version that accepted both but maybe not. That could make it an RX-100 then. Thanks for the link.

I think you're right -- it's been a while since I've had the cassette off the RSX hub in my collection, but it may be threaded for Uniglide as well.

As I recall, the RSX cassette hub was from the beginning a Hyperglide-C (compact drive) -compatible freehub with stepped-down freehub body for 11t cogs.

As such, it should not have any external threading.

And at this late hour, few would be hoping for their cassette hub to be compatible with Uniglide cassettes, though I for one will use up those I have because of their friction-friendly shifting action.

Using a 6-speed cassette in a modern freehub is still entirely possible if a suitable lockring and spacers are used to compress the un-threaded cassette cogs, but a splined smallest cog would still need to be a part of the picture.

This will go on a bike with friction shifters. Is that not a great idea for hyperglide? I've got no problem experimenting with trial and error .

A picture can be worth far more than a thousand words and an ounce of knowledge is worth a pound of guesses.

Sheldon Brown RIP created one of the best sources of information on cassettes on the web. It has lots of pictures with easy to understand explanations plus work arounds. I used this when I put together my first cassette hub back in 2007. I put a 7 speed cassette on a 6 speed freehub by changing the spacers. (yes, I'm a late adapter and a retrogrouch)

https://www.sheldonbrown.com/k7.html

One note, I call the UG (Uniglide) sprockets "twist tooth". When Shimano introduced them they offered an improvement in shifting of previous tooth designs but HG (Hyperglide) sprockets shift so much better.

One problem that I've run across with the twist tooth UG sprockets is that on a hard shift with a worn out upper derailleur pulley I've had chains bend to the angle of the twisted teeth.

Most modern replacement chains for older bikes are designed to work on 6-7-8 speed freewheels and cassettes. 9 tooth and up cassettes definitely need narrower chains. That's why chains for 9, 10 and 11 cassettes are available.

When Shimano introduced their SIS indexing system in the mid 80's they started making upper pulleys with some side to side lateral movement. This allows the chain to self center on the sprocket which is key to effective index shifting. Worn out upper pulleys can be rocked back and forth at an angle as well as side to side. They need top be replaced.

BTW, RDs made for indexing work GREAT with friction shifters. The side to side float of the upper pulley pretty much eliminates trimming the lever after shifting.

verktyg

1st generation RSX (1995-1998) was both Uniglide and Hyperglide compatible. You can see the threading for the outer cog in the atttached 1995 catalog scan. It also shows a Hyperglide cassette as standard. The 2nd generation, introduced in 1999 was 8 speed and Hyperglide only.

Hyperglide cogs improve shifting under load whether it's friction or indexed. I always go with Hyperglide, where possible.

One caution is that while 6 and 7 speeds hubs have the same OLD (Over Locknut Dimension), the 7 speed cassette/freewheels are slightly wider, with the outer cog typically sitting closer to the dropout. Consequently, the cogs and/or chain will sometimes interfere with the stays on frames designed for 6 speed if they not been relieved on the inside surface. This can generally be solved by using a 1-2mm washer under the drive side locknut, though the axle should be re-centred to ensure equal protrusion beyond the locknut on both sides.

Thanks T-Mar. That scan is one of the pictures I saw that lead me to believe this was an RSX. Your comment about 7 speed width is the main concern I had about going to 7 instead of 6. Right now my 6 speed freewheel has no interference but the frame was made for that size. I don't think there is any indent on the seat stays but I'd have to double check. Worst case scenario if a 7 speed is too wide I'll just shift some axle spacers and re-dish if I need to.

Yes, your mechanics fault. New cassette=new chain is the right path with only a few exceptions.

^ +1, a new chain or cassette often works well with a old chain or cassette even on the work stand. However, hand cranking under no load generates an insignificant amount of torque compared to what the drive system experiences on the road. Only a road test will reveal wear related incompatibility. Unfortunately, shop mechanics do not have the time to conduct road tests on repairs and even if they did, customers would rant over the extra cost. Consequently, a certain amount of repair returns are cost of doing business.

You'll never know until you try. You can get a rough idea based on the current lateral clearance between the stay and the chain, when it's on the small cog. If it's more than 5mm laterally, with your 6 speed set-up, it should work without need for spacers on 7 speed. However, most home mechanics neglect to consider that the chain moves vertically when derailing and shifting onto or off the small cog. They put the chain onto the small cog and install the wheel. Everything fits fine but the first time that they try to shift, the chain jams into the seat stay. You need the lateral clearance at a point above the small cog, so there's room for the chain to move vertically and clear the teeth of the cog when derailing. How high this clearance must extend depends on the size of the tooth jump between the smallest and 2nd smallest cog.

That seems odd that they'd still put threads on the outside of the freehub body so late in time. Uniglide was long-gone from their lineup already, and it was never Shimano's practice to use other than HG cogs with STI shifters.

Perhaps even more odd is that I bought a road bike having the early 7s version of RSX (with "compact triple"), and it had an 11-24t, 7s cassette.
So it remains a mystery how that compact cassette would even fit on that supposedly-threaded freehub body. Perhaps the shop ground it down (a standard shop modification at that time) or maybe just kluged a spacer under the "compact" 11-24t cassette(???).
Does anyone else here recall what cassette size came fitted with your RSX 7s gruppo?
I can't tell from T-Mar's catalog photo.
I didn't keep that bike long enough to ever have to remove the cassette, I'd actually just bought it for a friend to ride. It was a Diamondback Expert and I still recall how particularly poor that the bike's spoke tensioning was.

It'll be close. I have a little bit of room and the stays are notched a bit. I'll report back when I have it on.

I'm currently running a 9 speed SRAM HG cassette on my folding Dahon and friction shifting with 8 speed barends. No issues whatsoever.

If you are handy, take apart a 9 speed cassette and using the spacers from it, you should be able to squeeze 8 sprockets onto your 6/7 speed freehub.

I am handy! So basically I'd have 9 loose sprockets and I can just choose which 7 or 8 of them go on? But then I assume I'd also need a narrower chain. I will consider that in the future if not for this ride.

The fact of the matter is that I really won't benefit from more cogs. The way I ride and the area I'm in keeps me only on about 5 different ratios. My problem is that the 6 speed cassettes that I have found are all about one tooth bigger than what I ride normally. i.e. I'm usually in my 15 or 17 but I've only found 16/18. I'm not sure that would even make a big difference but it has been on my mind. But there are enough hills here that I'd like a 28t. Just can't go bigger than that without swapping the RD and I'd rather not do that.

[MENTION=315073]The_Joe[/MENTION], yes! That's the beauty of this approach, is that you can fine-tune the gearing that you want. Say you like really tight gearing and just need a bailout for the occasional tough hill. You could set this up as a 13-15-16-17-18-20-24-28, 8 speed. I'd use a 9 speed chain. In order to fine tune to the exact gearing you might need to purchase two 9 speed cassettes, possibly a SRAM 12-25 and an 11-28. Best of luck with your project.

Good to know. I'll see what the co-op has and weight my options. Thanks for the help.

Seeing what you can cobble together from to co-op on the cheap is an excellent idea. Make certain to check the spoke-side of each sprocket. Excessive wear becomes apparent on that side first. Some cassettes are riveted (which is easily ground off or have a screw or screws in which case you will need a very small hex wrench.

What do you look for as signs of wear in a cassette?

I have a cassette (a couple of them actually) that slip under heavy load. I'm thinking the teeth are worn down, but I'm open to the possibility of something else being the cause, like a RD adjustment or bad chain.

The pictured CS-HG70-7 cassette is 11-24T. Those "compact" 11T HG cogs do fit. However, the spline channels do not run the entire width of the cog like on a 12T. If they did, the cog would probably split because the material between the channels and tooth valleys would be too thin. Instead, the spline channels stop about 2mm from the outside face, leaving a reinforcing lip directly under the cog teeth. This results in the cog overhanging the end of the freehub body by ~2mm. However on the HG-C freehubs the splines are actually relieved at the end of the freehub, allowing the cog to sit further onto the body. The diameter at the top and bottom of the splines is the same for both HG and HG-C freehubs.

Regarding the longevity of the dual compatibility 7 speed freehub, that would be a combination of marketing and economics. HG debuted in 1989, as 7 speed. RSX was Shimano 5th level road group and it took 6 years to trickle down that far. I don't consider that excessive. If you trickle it down too fast, you lose sales to from the higher groups, which have more profit margin.The longer you can use old tooling and the more groups you can spread it over, the more profitable it is. I don't think that Shimano's road groups got a dedicated, HG only freehub until Dura-Ace went 9 speed in 1997.

I just got back from the co-op. Leaning towards fiscal responsibility I opted for just a standard 7 speed rather than mashing up two 9 speeds and getting a new chain.

The cassette is 13-28 which puts it right where I wanted it to be. A small adjustment on the limit screws and it shifts nicely on the stand anyways.

Also, can come firm that a Suntour Cyclone MK-II will shift onto a 28t without error on a 42t chain ring.