I’ve a 3×9 Cannondale Badboy 700 and the chain set is well past its sell by date. New chain, cassette, jockey wheels and chain rings required. So, I’m considering doing the conversion to a 1×9 as I’m buying new bits anyway. I only ever use the middle ring and the longer ratio 2/3rd of the cassette. Just going for a new but equivalent cassette and a slightly smaller chain ring than what i have on the middle ring at the moment – currently 36 tooth.
I’ve a Shimano Deore triple / crankset upfront so what do i need to convert other than a new chain ring? Do i need special bolts?

You will need either shorter (ssp) bolts, or 2mm spacers to take up the space left by the large chainring. The spacers would also allow you to push the chainring in a bit for a more suitable chainline.

You will also need a chainguide (I have used a PS Chainspy 2) – the chain will skip off the chainring without one, even with a single speed specific ring. Haven’t tried a narrow-wide one, mainly because I couldn’t find one with 40T – you could try the On-One Ringmaster if you are ok with 34T.

Shorter bolts. You can get them from Charlie The Bikemonger.

Get a Surly SS chainring at the same time. It will last a lot longer than an alloy one. Works fine with 9 speed.

Leave the front mech on instead of a chain guide. Adjust the stops and remove the shifter and cable.

I ran a 1×9 commuting for 10 years, never dropped a chain.

Just get an narrow wide chainring. Even without a clutch mech I’d have thought it would be enough to stop you dropping your chain while comuting, unless you comute down rocky paths!

Going to go for a 38T or 40T i think…. Do i really need a chain guide if its a road commute? Just the odd bump or two? Its not a clutch mech.
Final daft question – Shimano Deore (from 2009) triple has 104mm bolt circle right?

You won’t need it until you drop the chain :). I initially rode my commuter without one, but after a couple of incidents I got fed up.

Yes, 104 BCD.

Cheers otsdr. Think I’ll get a chain guide. Some of the roads i cycle are very traffic congested and and small chain incident could lead to horribleness in the extreme.

otsdr – what chain guide did you get? Any recommendations?

Don’t bother with shorter bolts – just get a chainguard – basically a chainring with no teeth (or if you’re bored/tight then just file off the teeth on your outer chainring if they’re already goosed) and you won’t need the shorter versions.

I have an SRAM X-7 rear deraillieur…. Is the X-9 equivalent clutched? If so, then narrow/wide chain ring, shorter bolts and I’m sorted?

I have used the ProblemSolvers’ ChainSpy, the direct mount version (plus direct mount adapter); the clamp one seems to have a set screw, which is not a very rigid solution. http://problemsolversbike.com/products/chainspy

I successfully used spare bits from spd cleats to space the bolts on my commuter

The bit in the top right with 2 holes in it had the right diameter hole and was the right thickness and most importantly sat in my toolbox at the time

I ran a front mech as a chain guide on my commuter and it worked fine, no dropped chain.

Not sure I’d bother with a specific guide when an old front mech works perfectly well.

You will need some sort of guide though. Potholes and 20mph plus can easily bounce off a chain

Ive been running 1×9 commuting for a few years using SLX/XT off my MTB and I’ve never dropped a chain (I’m sure it’ll happen tonight now I’ve typed that)