SS Disc Hubs

Discussion in 'Fixed Gear and Single Speed' started by EasyPeez, 31 Oct 2017.

  1. OP

    EasyPeez Über Member

    I'm not sure if you or @Yellow Saddle will know, but my current stock rear hub is listed as
    Rear Hub KT-SY1F / KT-MX7R 6-Bolt Disc

    and rear sprocket as
    Cassette Shimano SF-MX30 18T

    Forgetting about a new wheel build for the moment, if I wanted to change the gearing on my current wheel, would my hub be one of the type you mention that are compatible with a screw on freewheel? And so something akin to the WI freewheel (or a cheaper alternative) would be the way forward in that respect?

  2. Pale Rider

    Pale Rider Guru

    Changing the gearing would bring the vexatious question of chain length and tension into play.

    Vexatious because almost inevitably shortening or lengthening the chain by a link - one inch - will be too much or too little.

    Your nice new mudguards mean you have limited axle movement in the dropouts, and in any case you don't want to have to realign the 'guard even if there is space because it's such a fiddly job.

    All this is leading to the fitting of a single speed chain tensioner.

    It's a shame to add something to what is a pared down bike, but a tensioner would allow you to experiment with gearing, and allow you to take up a bit of slack when the chain wears, all without messing around with mudguard and wheel alignment.
  3. OP

    EasyPeez Über Member

    Damn it. Nothing's ever simple with this 'creating the perfect bike' lark, is it? And this being supposedly one of the simplest of all forms of bike!
    Is there a simple way of working out what having two less teeth on the freewheel would mean in terms of necessary alteration to chain length?

    Forgive my ignorance, but I'm not sure what the tensioner would achieve that I can't currently manage by sliding my wheel backwards or forwards in the dropouts to alter chain tension and tightening up the little securing bolts that stop it pulling forward under force?

    That said, I do currently have my axle almost as far back in the dropouts as it will go so very little room for manoeuvre in that direction...
  4. Pale Rider

    Pale Rider Guru

    The chain tensioner has the same effect as moving the axle forwards and backwards - taking up slack in the chain - but the tensioner allows you a far greater range of movement than the drop outs.

    And as I mentioned, your axle movement is even more restricted because of the mudguard.

    I'm not aware of a method of calculating chain length when changing sprocket size.

    Another advantage of the chain tensioner is you wouldn't have to break or alter the chain to accommodate a range of sprocket sizes.

    You can run the chain above or below the pulley as well as swiveling the tensioner itself, which makes chain length not so critical - you can take up a lot of slack one way or another.
    EasyPeez and Threevok like this.
  5. OP

    EasyPeez Über Member

    Thanks for the explanation. I only see myself needing 2 sizes of rear sprocket and won't need to swap between them very often. I've yet to get my head around the ss chain and how ss split links work, but assuming they're as simple to break and refit as my 10 speed chains I'd rather do that from time to time than use one of those tensioners.

    I think a couple of people on here run the extra sprocket size I'm after so I'll enquire a bit more into it and see how they went about finding the right chain length.

    If it turns out a tensioner is the best solution then I'll go with one of those.

    Pale Rider likes this.
  6. Pale Rider

    Pale Rider Guru

    Hopefully you won't need a tensioner for two close sizes of sprocket, although you might be surprised how much difference one link makes.

    I had a similar problem changing a sprocket on an Alfine 11 hub gear bike, the chain was too short, but putting one link in made it way too long for the range available in the dropout.

    Which, of course, is why the bicycle gods created half-link chains.

    Another thought, assuming lengths can be made to work, is to have a chain with each sprocket.

    You then only have to break and join at each sprocket change rather than break, lengthen/shorten, and then join.
  7. Threevok

    Threevok Carpe Rotam

    South Wales
    Just to throw a spanner in the works (or rather an additional chaining) there's always the option of a "Ghost Ring" as an alternative to a tensioner.

    This sometimes works for road SS although I wouldn't recommend it for off road use (although some have done it)

    It also has the added benefit of confusing the hell out of anyone who sees it.


  8. OP

    EasyPeez Über Member

    This is my preferred option. Then presumably the chain and sprocket should wear in tandem too, so avoiding mismatched components.

    Aren't these crap though? The internet tells me that they are mostly for posers, weigh a ton and wear out very quickly.

    @Threevok - do you have a chain for each sprocket, or use a tensioner or ghost ring? And is there a calculation to work out what length chain is best suited to a gearing combo (i.e if I want to run 42/16 can I tell in advance how many links I would want in my chain) or is it trial and error?
  9. Threevok

    Threevok Carpe Rotam

    South Wales
    I am lucky, whereas my bike has swapouts (drop outs that enable the bike to be converted between vertical to horizontal dropouts). So I use the the horizontal dropouts and the same size chain for all - I just move the wheel back and fore accordingly and use chain tugs where necessary. Obviously, there are some combos where my existing chain would be too long or short.

    For you however, that may not be possible, as I suspect you do not have horizontal dropouts.

    In which case, I suggest a wheel tensioner.

    Planet X do a good conversion kit and tensioners too

    What frame did you say you had ?

    PS : here's a good link calculator
    Last edited: 9 Nov 2017
  10. OP

    EasyPeez Über Member

    The frame is a steel Genesis Day One and I have horizontal dropouts -


    As you can see I can't go much further back with the axle. I assume dropping 2 teeth from the rear cog would mean needing to pull the axle back further to take up the extra chain slack, so if I can't do that then I guess I would need to use a shorter chain length.

    Which I'm happy to do. A chain per sprocket is fine by me, as I'll only be running 2 sprockets and changing them very rarely. I'm keen to avoid a tensioner if possible.

    Thanks for the link to the chain length calculator. I guess I need to select 'fixed/cocoa tin gears' (wtf?!) from the drop down options, even though I'm not running fixed? And measure the chainstay from the very end to where it meets the bottom bracket?
  11. dave r

    dave r Pedalling Pensioner

    Holbrooks Coventry
    I have one male/female half link in the chain on my fixed, it enables me to position the back wheel where I want it. I have my rear wheel a lot further forwards than the wheel in the picture in the post above.
  12. Threevok

    Threevok Carpe Rotam

    South Wales
    Ah yes

    A Dingle Speed

    Double front and back cogs. I've been meaning to toy with that

    to answer the OP's question

    It's best to place your back wheel as far forward as possible, cut the chain nearest damn it to the length required to take up most of the slack, then use your chain tugs to tighten as required.

    Should you then drop a tooth or two on the back, you should still (up to a point) have enough scope to take up the additional slack.

    As you get fitter, put a bigger front ring on, move the wheel forward and start again
    Last edited: 10 Nov 2017
    EasyPeez likes this.
  13. Elybazza61

    Elybazza61 Veteran

    Just get Hope hubs cos they are :becool:
  14. OP

    EasyPeez Über Member

    Interesting. I'd never heard of that. I don't think I'll go down that route though. The point of getting a SS was for its overall simplicity and ease of cleaning after a week of commuting in bad weather. I'm happy to have 2 chains and two sprockets, with just one sprocket on the bike at a time, as I won't need to change the gearing very often at all.

    back wheel?

    Thanks for explaining. When you say as far forward as possible - not all the way forward though, eh? As it's necessary to leave some room for sliding the axle further forward in order to slip the chain off when fixing punctures etc, right? My mudguard also limits how far forward I can slide the axle. Though granted I could def pull it forward quite a bit from where it is now, if the chain were shorter.

    That chain calculator tells me that for my new 16t sprocket I'll need either 49 or 50 links in my chain, depending on how accurately I've measured the chainstay. If you were me would you cut the new chain down to, say, 52 links (to leave room for error), try it out, and then take out an extra link or two if there's still too much slack?

    I likely will in the medium-long term, but I'm currently having some wheels built for my road bike (on Hope RS4s), so a second handbuilt set for the SS commuter are not on the cards right now. Meanwhile I'm spinning out at 19mph and the bearings in my stock Shimano freewheel are clunking, so I need to get a new sprocket and chain for now.

  15. Threevok

    Threevok Carpe Rotam

    South Wales
    Yes, sorry

    As I said, as far as possible

    Yes - but you don't really need a calculator

    Don't overthink it - it's trial and error (very little error)

    Install your chosen Chainring
    Install your largest chosen sprocket
    Put your rear wheel forward as far as you can
    Install your new chain, measuring as you go, to see how much to cut off

    Everything else (chainline and slack) is fine tuning
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