Cheapo Conversion?

[Cedric]

Hi!

I've posted this in "technical" before realising that there was SS/Fixie forum. I've got an old Raleigh Boulder (don't laugh) MTB lying about. The gears are knackerd, but it was always a decent enough bike. I'm only going to use it on the flat(ish) going to the local shops and I thought that I might do away with the gears.

Being impecunious at the moment I thought about just leaving the chain on the middle chainring and using a kit to convert the rear hub to a single speed. The bike has horizontal drops, so I was wondering if I could just shorten the chain and adjust the rear wheel placement to fine tune the tension on the chain, thus dispensing with a jockey wheel (?) tensioner. I'm sure I'm being naive here, but most of the bikes I rode as a kid had no gears and no tensioner, do you actually need one with horizontal drops?

PS, Apologies to anyone who read this thinking that I'd found a cheap way to convert a multi-speed.

 

[tyred]

With Horizontal drops and single speed, you won't need a chain tensioner. You could do this on the cheap by just using the rear freewheel/cassette with whichever sprocket lines up with the middle chain ring. If it's a thread on freewheel, you could replace with a BMX type single speed sprocket for a few quid but you'll almost certainly have to work on the axle spacing, wheel dish to sort out a decent chainline. A conversion kit to convert a cassette hub to singlespeed is available with all the spacers needed. Using your existing freewheel block will work okay if it gives you a suitable gear ratio. It may slip the chain occasionally but shouldn't do it that often. You could even dismantle the freewheel or cassette, remove the sprockets you don't need and replace with spacers. A bit of 1 1/4" plastic waste pipe cut carfeully to size would work.

 

[Amanda P]

Tyred is right.

Just use the middle ring and a middling sprocket, shorten the chain to suit and adjust the chain tension by moving the wheel forward or back in the drop-outs. Remove and discared both derailleurs, their cables and shifters. Job done.

I was lurking by a road junction near a timber depot in South Africa for half-an-hour recently*. During that time maybe a hundred timber workers came through the junction on bikes, and most of them had their bikes set up this way.

* Nothing sinister; I was minding our bikes while Mrs Uncle Phil went shopping.

 

[Cedric]

Cheers for responding. I'm at this....

...stage right now. Does this set up look safe?

 

[tyred]

If the chainline is straight, that should be fine.

 

[Cedric]

Tyred, thanks! Got on the bike today and it was running well, not bad at all, however, I ignored the advice to get a new chain, the old one had spent about three years outdoors. Guess what happened when I accelerated up a steep track? Chain snapped!

Is this just because I'm using an old chain, or should I be using a stronger chain? I've heard that BMX chains are the best for SS.

 

[hubgearfreak]

I've heard that BMX chains are the best for SS.

they may be, but they're 1/8th of an inch thick, whilst doing a single speed with 3/32nds dérailleur chainwheels & sprockets as you have done means that it probably wouldn't fit between the rear sprockets. a new chain of the 3/32nd variety would be plenty strong enough

 

[Cedric]

Thanks HGF, so just a new chain, normal multi gear type should do the trick? The old chain was a bit abused I must say. What kind of chains do people on real SSs use BTW?

 

[hubgearfreak]

What kind of chains do people on real SSs use BTW?

my LBS also caters for skaters, BMXers & etc. he had in a 1/8th BMX chain and that's what i used.

it wouldn't matter if the chain is wider than the sprockets, but is there enough space for it without hitting the ones either side?

 

[Cedric]

Hi HGF, That looks good and solid. I doubt there'd be enough room for a BMX chain, will just a new chain be ok do you think?

 

[Amanda P]

A new chain will be fine - ask for an 8-speed one (slightly stonger than 9 or ten-speed chains).

Part of the rationale for fitting 1/8 chains to fixies is that on a fixie, you really can't afford to have the chain break. It's less critical on a single speed. As HGF says, there's a risk that a 1/8 BMX type chain would drag on the unused sprockets and chainrings, or might be wide enough not to mesh with any single rear sprocket at all.

If you already have a 1/8 chain, try and let us know what happens! If not, buy an eight-speed derailleur chain.

 

[Greenbank]

For 1/8" I use SRAM PC1-N. £10 a chain and lasts for over 5000 miles.

 

[Cedric]

Phil, GB, thanks? I've already ordered one off ebay. It's supposed to be haevy duty and suitable for BMXs and 5/6/7/8 speed MTBs. It's made by Massi. Hope I haven't stuffed up.