sleepy

I don't know if this should be in the mechanic sub-forum, but is it possible to build up a six speed cluster as a cassette to be used with Index downtube shifters? Are there spacers that would match up as in a freewheeL?
Anyone ever do that?

rccardr 

Sure.
Yes.
Easiest way to do it is to contact eBay seller "mtbtools" and tell him what you want to do. He'll cut a set of spacers for you, just tell him you want the biggest ring spaced out 4.5 mm from the back of the freehub. Put on the 4.5 spacer, the biggest cog, then spacer/cog/spacer/cog until you have all six mounted, then use the final spacer and the HG lockring. Indexing works fine and the chainline should be correct.

It's also possible to do this with a 7 speed 126old rear hub, but would have to measure the correct backside spacer size.

pastorbobnlnh 

Yes. There are 6 speed Uniglide Cassettes. You kind of need a Uniglide hub to make it work. However with some rear spacers, it could work on a modern Hyperglide hub. With a bit of grinding on the large tab on the Hyperglide sprockets, you can build a new cassette that uses 5 Hyperglide sprockets and the original UG thread on small sprocket.

mtnbke

Doesn't Jan Heine sell 126mm and 120mm cassette free hubs for 5-speed and 6-speed cassettes?

mountaindave 

+1 What has been said above.

RobbieTunes

No clue. I read this thread to find out.

pastorbobnlnh 

He does, but they are basically for the special built SunXD cassette hubs.

@sleepy, we need to know more about the hub you are running that you want to install a 6 speed cassette on.

thinktubes 

LeicaLad 

I have a 120mm rear spaced bike that has been spread over time to about 122-123mm.

I found a nice Shimano 5-speed freehub (see: VeloBase.com - Component: Shimano 600 Uniglide, 600EX (5sp) Freehub). This hub was produced with the 120mm axle only a short time, and then it appeared as 124mm declared a 6-speed.

I also found the Shimano 5-speed uniglide cluster for it. I ran it for a while as 5-speed. Then, playing around, I used 9-speed spacers and a 9-speed chain to bring my 122mm spaced hub (remove smallest axle spacers) up to 6-speed. It resembles Ultra spacing, but works very nicely.

Much depends on which hub you are working with, and what spacing you bike can handle. You can spread the bike, if you wish, but some bikes I don't.

ymmv.

sleepy

I was just wondering. I was hoping that you could put the sprockets with the appropriate sized spacer on a modern hub.

mountaindave 

With a ~4.5mm spacer, you can likely fit a 6s cassette onto a 130 OLD hub intended for 8/9/10 speed cassettes. I've done it for 7s cassettes and they were on a nearly identical freehub as the 6s cassettes (same 126 OLD). You will likely need to have an assortment of spacers to test fit which works best.

A slight digression: there are likely many among us here who use 6s cassettes in a half-step arrangement to get tight, non-overlapping gear ratios.

sleepy

Thank you.

nfmisso

It is pricey:
https://www.compasscycle.com/shop/co...-cassette-hub/

https://www.compasscycle.com/shop/co...peed-cassette/

https://janheine.wordpress.com/2013/...cassette-hubs/


The six speed version uses 7 (or 8 depending on which source....) speed spacing - meaning you'd need 7 (or 8) speed indexed shifters or friction shifters to work correctly. The cassettes are twice the cost of a Shimano 7 or 8 speed cassette - which they are made from.....

See: Sheldon Brown's Bicycle Frame and Cassette Spacing Crib Sheet

netto99

But how would you actually do it?

I have a similar problem to OP. I'm planning to make a wheel with the aforementioned SunXCD 120mm freehub, and I was wondering what cassettes can I use as donors for a 6 speed build for the hub.

The Grand Bois staff is ready made, but I was wondering if one could make something cheaper and maybe even higher quality

ThermionicScott 

There's nothing special about the Compass/Grand Bois cassettes. All they do is buy regular 13-30 "G" and 14-32 "F" 7-speed cassettes, grind off the rivet heads so that they can be punched out, and then sell 5 or 6 of those loose cogs along with 3.65mm spacers. Much of the cost is in the labor to do all that, not the original cassette.

netto99

What is the maximum cassette width that could fit on 120mm hub? Because 6 cogs 1.85mm each and 5 spacers 3.65mm would total to 29.35mm, which is way above regular 5 speed width of 24mm.

And what are "G" and "F" designations?

Thank you in advance.

ThermionicScott 

You've worked out why hubs needed to get wider to fit more sprockets.

Each Shimano cassette has a letter code, and since I more or less live in 7-speed world, I like to use them as an additional reference: Shimano and Shimano-compatible 7-speed cassettes The 13-21 "J" was nice and tight, but no longer in production, whereas the 13-34 "K" is pretty wide.

Exact specs on the SunXCD rear hubs are hard to find. I'm tempted to wonder if they are the same as the Grand Bois hubs with a few aesthetic differences, but would not want to assume it. Compass says that you can fit either their 5-speed or 6-speed cassette on the same 120mm hub, so I'm tempted to think that the 5-speed cassettes use 5.5mm spacing and the 6-speed cassettes 5.0mm "Ultra" spacing. That gets us to a width difference of 3mm, which is probably workable as long as the lockring has enough threads on it.

You can see how the 6-speed cassette sticks out a little more:

netto99

I see now. Relics of the past

I've read somewhere that Grand Bois had their hand in design of the SunXCD hubs, but don't quote me on it.

As for cassette, I'll try to buy PG 850 and take of two biggest cogs.

mountaindave 

The OP was interested in indexed shifting. If you didn't care and went friction, a guy could get some 3mm 8s spacers and get an overall cassette width down to 26.1mm. Go a bit farther with 2.56mm 9s spacers and get it down to 23.9mm... You wouldn't have much room for error when shifting. I'm using an 8s setup in friction and am not a fan. I can do 5 or 6 speed in friction, but for 7s and above I like indexing.

ThermionicScott 

Same here. I ran 7-speed in friction mode on my rando bike for a couple of years with no real issues (got the set of 6-speed DT shifters for a steal ), but I'm much happier now that it's back in indexed mode.

dddd

I've found that when friction shifting on a 7s freewheel that I can get back some of that 5s/6s goodness by using the next-narrower (9s) chain.

That, and using a shift lever with relatively longer lever and smaller "spool" diameter, perhaps together with a derailer like Campy Ergo with a lower actuation ratio.

The retrofriction levers help noticeably even more.

So it is possible to have a super-slick shifting setup with a 7s freewheel. And the B-tension adjustment can contribute to even better 7s friction shifting, but the adjustments can have a compromising effect on shifting at one end of the freewheel versus the other end.

mountaindave 

Good to know about the chain - it would probably be required if sprocket spacing went down considerably. I was going to mention that Retrofrictions would likely help, but I haven't personally experienced them on a 7s setup - only 5s. Love them BTW, but that's another thread...

netto99

I plan on going indexed as well, once I get enough money for it.

I'll go for SunXCD shifters and derailers. Rear shifter is 9/10 speed and derailer is indexed to 7/8 speeds. So in theory should index nicely with 8s cassette leftovers.

DarkSqrBishop

An example here: 8 speed standard Shimano cassette (11-12-14-16-18-21-26-32):




Some custom cassette choices:
11-14-16-21-26-32


11-14-16-18-21-26



11-12-14-16-18-21



Any of those should work, how wide is that sunxcd short hub?