Converting to Single Speed?

[Irezumi aka Reuben]

Rather then buying yet another pushbike (or assorted parts to make in to one) I'm wondering whats the best way to convert and old ridgeback genesis roadbike to a SS?

Currently has an octalink (I'm pretty sure) 3 piece triple crank and 9 speed on the back, vertical drop outs. So whats the best way to go about it and what's a good idea for gearing? I'm a pretty keen cyclist (30 mile round commute 3-4 times a week) so have a fair bit of strength but I do have a reasonably hilly (for south London) route.

Thanks for any help.
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Pictorgraphicalfantastical

[Pete.]

This is easily done.

Don't change gear
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[stinkwheel]

You're going to need a chain tensioner (because vertical dropouts) and a single speed conversion kit to give you a cog on the rear.

You can use the existing derralieur as a tensioner (adjust the limit stop for alignment) or fit an aftermarket one. Surly make a good tough one I've used on single speed mountain bikes. I think deraleiurs look crap on a single speed and are heavier and more complex than you need.

You'll need an idea of what gearing you're going to want. Looks like your crank is a spider type with chainring bolts? You can leave it as-is and just use the middle ring OR you can remove the rings and use a single ring on the spider. You may need to get half-width chainring bolts to do this depending on the setup. Another option is to keep the middle ring and fit a bash-ring where the big one was.

Hopefully your existing ring is ok, but you can also buy single chainrings if you know the number of holes and bolt circle diameter.

At 9 speed, I'm presuming it's a casette hub. The conversion kits come with loads of spacers making it very simple to get the chain line bang-on.

It sometimes helps to use a half-link in the chain so the tensioner isn't doing so much work.

So. Decide on gearing, I'd suggest the existing middle ring plus your selection of rear cog (I run 46-17 on my single speed road bike). Fit chainring to spider with existing or half-width stack bolts depending on what fits. Fit single speed kit to hub, space to get straight chain-line. Fit tensioning device or modify deralieur. Grow beard.

I get a lot of specialist single speed bits from charliethebikemonger.co.uk They'll have tensioners, half-with stack bolts, SS kits, chain half-links etc.

I get a lot of advice from Sheldon Browns website:
https://www.sheldonbrown.com/singlespeed.html
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[stinkwheel]

Here's how I did my last MTB. Similar conversion to what you're proposing only I've used a spin-on freewheel (which is harder to get a good chainline with than a freehub cog kit.

The chain tensioner is a surly singleator.

I've actually used the small chainring here and cut the tabs for the larger chainring off the spider. There's a halflink in the chain on this to minimise chain sag for the singleator to take up. I also filed flats on the wheel spindle to give a little more adjustment.
https://i48.photobucket.com/albums/f216/stinkwheel/CIMG0984_zps08721baa.jpg

This is the drivetrain on my newer MTB (has fork-track ends so no need for a tensioner) I've used a 1990's suguino crank here with a 22 tooth ring on the inside and a bash ring on the outside.
https://i48.photobucket.com/albums/f216/stinkwheel/inbred/CIMG1591_zps305cb67b.jpg

You can also get purpose made, single ring cranks but if you've got a half-decent crank already, as I think you do, you may as well use that. Existing rings are generally fine. You can fit a heavier duty, SS specific one which looks cool and doesn't have "steps" built-in for shifting, making the most of your heavy-duty SS chain. You can find the BCD by measuring between two hole-centres then consulting the chart on https://www.charliethebikemonger.com/chainrings--bolts-202-c.asp
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Irezumi aka Reuben]

Thanks for all the help Stinkwheel, familiar with all the BCD etc as do all my own mechanics just never ventured in to SS territory. Building up another nice road bike which I may run with a SRAM 1x10 narrow wide chainring.

Speaking of which do you ever run chain catchers on your SS bikes?

For my SS road bike looking to run a 48x12 set up (I'm in London so not an issue with hills)

Thanks for the help, those MTB's look like theyd wheely pretty easily!
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Pictorgraphicalfantastical

[stinkwheel]

Shouldn't need a chain catcher if the chain line is straight and the tension is reasonable. Single speed chains have straight side plates, the sprockets have full height teeth all the way round and no little "ramps" to aid shifting. The chain doesn't WANT to come off, it's happy where it is.

Even when I stripped out the deralieur hanger thread so I had no tension on the chain on the red bike, it would tend to skip teeth rather than jump off and was still rideable as long as you kept in touch with the freewheel.

I'd suggest 48-12 is pretty steep. The idea is you spin more. You're going to have fun stopping/starting in traffic on that gearing. However, SS cogs for freehubs are less than a fiver so you can play around.

I may go lower still on the latest MTB gearing... Struggling to climb up over rocks.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Irezumi aka Reuben]

Thanks Stinkwheel, I live in London and am a reasonably good cyclist. May start with a 46 chainring to start with and work from there though.
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Pictorgraphicalfantastical

[stinkwheel]

[G]

You forgot the most important bit ...

https://www.google.com/search?q=stick+on+beard&tbm=isch