Singlespeed Query

For discussions about bikes and equipment.
Ontherivet77
Posts: 253
Joined: 3 Jun 2009, 3:20pm
Location: Lancashire

Singlespeed Query

Postby Ontherivet77 » 28 Sep 2009, 3:58pm

I've got some spare Mavic Aksium wheels with 9 speed cassette and am looking to mate these with a second hand frame and set up as a singlespeed. Please can anyone offer some advice on the best way to go about this, ie do I need to redish the wheel and what does this entail. Also, apart from chain length what other issues are there as my technical knowledge is pretty weak as you can see. :?:

User avatar
MLJ
Posts: 536
Joined: 15 Jan 2007, 11:48am
Location: Rugby

Re: Singlespeed Query

Postby MLJ » 28 Sep 2009, 4:07pm

You will need to change the hub of your wheel, as well as the chain type and length: single speed wheels have either a double screw or single to which a freewheel sprocket or fixed is screwed. Often the double is chosen so that each side can have a different sprocket to allow the wheel to be flipped over for a different gearing. The chain for the sprocket will either be a 1/8" or 3/32", the latter is used for 7 or 8 speed systems. Your 9 speed chain is narrower. You will need to discuss with your LBS, or else with Spa Cycles or SJSC.

User avatar
Si
Moderator
Posts: 15148
Joined: 5 Jan 2007, 7:37pm

Re: Singlespeed Query

Postby Si » 28 Sep 2009, 4:13pm

For singlespeed, as opposed to fixed....

If they are shimano type cassette hubs then you just need to remove the cassette, and add a sprocket of your required size with old cassette spacers, chopped up plumbing pipe, etc to hold it in position - obviously you want to space it so that it's in line with the chain ring and gives a straight chain line. If it's a campag then I dunno 'cos I've never converted one of them.

This shouldn't require re-dishing the wheel.

Chain tension is the other issue - if you have horizontalish drop outs then you are OK. If not then you can get a chain tensioner for under a tenner if you shop around (there are other things that you can do such as magic gears, half links, etc but a tensioner is , IMHO, the least faff).

The third thing is the chain ring bolts - if you are converting a triple or double chain set to a single then you'll probably need shorter chainring bolts (or some washers) again, these are pretty cheap and available from most good bike shops - go for steel not Alu.

Also, remember that a bike with a free wheel rather than fixed still needs both brakes to be legal.

If you decide to go for fixed instead then you'll probably need a new hub unless you are good with a welder, plus, under no circumstances should a chain tensioner be used with a fixed wheel!

Ontherivet77
Posts: 253
Joined: 3 Jun 2009, 3:20pm
Location: Lancashire

Re: Singlespeed Query

Postby Ontherivet77 » 28 Sep 2009, 4:25pm

Cheers,

The cassette is a Shimano 9 speed. Could I just select the 16/18 sprocket and tension the chain with the cassette still on or am I being stupid?

User avatar
rootes
Posts: 605
Joined: 27 Jul 2008, 6:44pm
Location: Woking, Surrey

Re: Singlespeed Query

Postby rootes » 28 Sep 2009, 4:31pm

Ontherivet77 wrote:Cheers,

The cassette is a Shimano 9 speed. Could I just select the 16/18 sprocket and tension the chain with the cassette still on or am I being stupid?


yep

you can get freehun to singlespeed converter kist that look a bit neater.. and yu can get the best alignment - also surly make a freehub compatible spingdle speed sprocket that has a thicker base so it does not eat the freehub body

see http://www.chainreactioncycles.com/Mode ... elID=17776

http://www.chainreactioncycles.com/Mode ... elID=17775

http://shop.ebay.co.uk/i.html?_nkw=sing ... rom=&_ipg=

Ontherivet77
Posts: 253
Joined: 3 Jun 2009, 3:20pm
Location: Lancashire

Re: Singlespeed Query

Postby Ontherivet77 » 28 Sep 2009, 4:48pm

Thanks, I'll check these links out.

bensonboo
Posts: 268
Joined: 29 Jun 2009, 7:28pm

Re: Singlespeed Query

Postby bensonboo » 28 Sep 2009, 9:35pm

You may not need a tensioner even if you get lucky and find the right size rear sprocket to do away with one, I did and I don't have horizontal drop-outs.
My bike is pictured on this thread.
http://forum.ctc.org.uk/viewtopic.php?f=5&t=28619

User avatar
DaveP
Posts: 3291
Joined: 9 Mar 2007, 4:20pm
Location: W Mids

Re: Singlespeed Query

Postby DaveP » 28 Sep 2009, 10:22pm

There are drawbacks to using cassette sprockets in single speed setups. The teeth of cassette sprockets are designed to allow the chain to be displaced easily. If you have a derailleur fitted then this is not a problem because the same system that unseats the chain also feeds it onto the sprocket accurately and takes care of the tension - continually. If evrything is perfectly aligned and tensioned then there should be no problems - but this is the real world...
IMO its better to buy yourself a purpose made single speed sprocket. The teeth are much taller and the chain is much less likely to come off. You can get them from, for example, On-One bicycles. Spacers can be bought (nice and shiny), made from old pipe (cheap), or scavenged from old cassettes (some 10sp spacers are nice for fine adjustments). Tension device - up to you!
And if you decide to try fixed, then probably best to start with a new hub and dont even think of a tension device!
Trying to retain enough fitness to grow old disgracefully... That hasn't changed!

User avatar
quiksilver
Posts: 275
Joined: 13 Apr 2009, 9:38am
Location: Cornwall & London

Re: Singlespeed Query

Postby quiksilver » 1 Oct 2009, 5:56am

Check out Sheldons site or LondonFGSS.

fixer
Posts: 120
Joined: 14 Jun 2007, 8:00pm

Re: Singlespeed Query

Postby fixer » 1 Oct 2009, 9:53am

The teeth of cassette sprockets are designed to allow the chain to be displaced easily. If you have a derailleur fitted then this is not a problem because the same system that unseats the chain also feeds it onto the sprocket accurately and takes care of the tension - continually. If evrything is perfectly aligned and tensioned then there should be no problems - but this is the real world...


Ony if you're pedalling backwards. If the chain tensioner doesn't move sideways, I don't see why cassette sprockets would de-rail the chain anymore than plain sprockets.

As already mentioned, the easiest way is to just remove all the extra sprockets from the cassette and replace with spacers, and fit a chain tensiner if needed.

User avatar
Si
Moderator
Posts: 15148
Joined: 5 Jan 2007, 7:37pm

Re: Singlespeed Query

Postby Si » 1 Oct 2009, 12:01pm

Yep, i've been using sprockets from a cassette and never had trouble with the chain coming off while they are in good condition. However, they do wear a lot quicker than non-ramped ones, and this wear can cause chain slippage after some time, but then that's also the case with using the cassette in a multi-geared setup, just that it takes longer to wear then.

However, you can get non-ramped 3/32 sprockets to fit on a freehub body, e.g. the shimano DX BMX ones. Unramped, slightly thicker than cassette sprockets and steel, so they do last well. But I think that you are limited to 16t and 18t - it is possible to get a 17t from another maker but they cost a fair bit more when I last looked.

gilesjuk
Posts: 3270
Joined: 17 Mar 2008, 10:10pm

Re: Singlespeed Query

Postby gilesjuk » 1 Oct 2009, 1:27pm

Go for bigger cogs if you can, 32/16 is ok, but if you're using a push down tensioner there's little chain wrap.

Try 36/18, the cogs last longer as well.

Push up tensioner is the best if you can get one. An old mech can be bodgified to work as a tensioner, but a dedicated tension is tidier and less likely to get ripped off by rocks and tree stumps.

User avatar
DaveP
Posts: 3291
Joined: 9 Mar 2007, 4:20pm
Location: W Mids

Re: Singlespeed Query

Postby DaveP » 1 Oct 2009, 10:10pm

fixer wrote:I don't see why cassette sprockets would de-rail the chain anymore than plain sprockets.


I probably didnt do it very well but I was trying to make the point that a derailleur mechanism does quite a bit more than simply shift gears. It takes up any chain slack and it also guides the returning chain accurately onto a sprocket even if sprocket and chain ring are misaligned - which they usually are in a multi speed set up.
The problem that seems to me to be particularly intractable is the relationship between the axis of the rear wheel axle and that of the bottom bracket spindle. Theoretically they should be parallel. If the frame is less than perfect, and I'm afraid many are made just that way, then no amount of fiddling about with spacers is going to produce a spot on chain line and you have to ask yourself how secure the chain will be.
I realise that some folk use cassette sprockets in a single speed set up without encountering problems but IMO their success depends on having evrything near perfect, tension, chain line, everything. I tried it for myself and it didnt work too well for me. I found it difficult to set up, the chain seemed determined to leap off at every chance - and this was on the bench. One suggestion I came across was to sandwich the sprocket between two large (possibly home made) washers or even two larger sprockets. This struck me as a rather inelegant solution in that it defeated one of the objects of the exercise, easy cleaning for a winter bike. I bit the bullet and purchased a single speed sprocket with full height teeth. This was the only change I made and the improvement was immediate and confidence inspiring. No more toptube anxieties for me!
Trying to retain enough fitness to grow old disgracefully... That hasn't changed!