Singlespeed & Fixed Gear - Fixed Gear/Singlespeed Conversion on the Cheap
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05-27-10, 07:31 PM
After riding my new MTB for a few days I realised that I only really use three out of the 15 speeds, and two of them are for off-roading- which got me thinking about singlespeed bikes. With my luck there was a budget surplus from my MTB project so I can start this one soon.
I want something that is durable, no maintenance, has good all-weather performance, and is (optional) fairly lightweight. I'm not in it for the "purist" vibe, so it doesn't need to be a fixie- singlespeed, or even internal three-speed is okay. The only things on it, apart from the bicycle standards themselves, will be a small headlamp and a small tool bag.
I really want to try this out, if only for the experience of it, but must do so on the cheap, meaning $50 or less. For reference I have racks, brakes, lights, etc in terms of upgrades already in my storage supplies so the budget would go to chains, tires, wheels etc.
Now this would mean scanning craigslist or the local goodwills for a decent looking bicycle, and then converting it to a singlespeed- that's where I need some help.
Now say I pick up a mountain bike, vintage bike, or even road bike with derailer gears. What would need to be done, all in all, to convert it to a singlespeed, or alternatively, if I find an old three-speed, how to make it fulfill the requirements of durability and versatility?
Thanks, this forum has been very helpful already. :thumb:
05-27-10, 07:39 PM
Well you could just buy this.
It converts your cassette hub into a singlespeed, nothing too fancy.
If you were to pick up an old bike, mtb or vintage or whatever, all you need to do is just to strip off the derailleur cables and shifters and derailleurs, also remove one chain ring from your crankset. You'll need new chain ring bolts for a having a single ring on your crankset. If you happened to pick up an old 10 speed with a freewheel hub, you could just remove that freewheel cluster and put on a single speed freewheel and you're done.
05-27-10, 08:29 PM
Also, forgot to ask in the previous post- what's a good gear ratio (expressed in sprocket teeth, please)? I will be doing mainly road riding with some occasional light-to-mid trail riding and light-to-mid gradients to traverse, but no 90 degree hills or riding through tall grass, etc. I will be doing a winter commute on it though, so if I visit a colder state that means snow. I would like to maintain about 12-15 mph at a reasonable rpm. I also don't mind swapping rear sprockets, but I can only carry one spare sprocket in the tool clip I found for the bike.
Different for everyone.
If you are running SS it's less critical than Fixed because the downhills won't matter as much.
Easier to express in Gear inches: 60's is very casual 70's is casual still but fast, 80's is harder probably best for flats, 90+ mostly for track and show-offs.
So something likes 44-18 would be in the 60's, 44-16 would be in the 70's, etc etc...
if u're only using 3 out of ur 15spds, then just figure out which speed u usually stick to, count the teeth of whatever u decided on, and u're done
05-28-10, 09:05 AM
How do you change/adjust your gear ratio? Do you need pick up a new crankset/chainring? Is it the back cog?
05-28-10, 03:47 PM
^The gear ratio is the ratio between the number of teeth on the front cog and the rear cog. So if you have a 32 on the front and 16 on the rear, that means the front has two times as many teeth, hence 2:1.
Anyway- could a Walmart bike be converted to a single speed? Yes, yes I know they're sh*tty and will break on the first trail ride, etc etc. Walmart has an aluminum-framed, well equipped bike, a hardtail with front shocks, horizontal dropouts, and a disc brake for $150. I could tear off the shifters, cables, controls etc, having never needed to use them, and get some of my money back to pay for lighting and a tool bag.
I don't have any bike-specific tools (like a freewheel remover, etc) anymore; would a bike shop charge a ridiculous amount of money to do some of the mods required to get a singlespeed cog on the rear wheel? From what I remember all that would require special tools is removing the freewheel, threading it on shouldn't require tools. Taking off the front chainrings could be done with allen keys, and a chain tensioner wouldn't be necessary because of the horizontal dropouts.
Any flaws in my logic here?
05-28-10, 03:52 PM
I'd say if you're trying to keep it on the cheap, try and find a bike co-op or something like that to use their tools and do it yourself.
05-28-10, 10:26 PM
Hmm, just had another idea- I could get two workable speeds by reversing gear ratios. For reference, this would be on a frame with horizontal dropouts.
Say I have a 2-chainring crank. And I align two rear sprockets with each of them, that both use the same chain length, but with the gear ratios reversed.
So one front chainring/rear chainring ratio would be 32:16, and the other would be 16:32, giving me a low and high gear. They could be switched manually by loosening the rear wheel (Thereby loosening the chain as there are no shifters or derailers), moving the chain to the other gearset, and then retightening the wheel. With an onboard tool bag and experience at wrenching it could be done in as little as a minute for easy trail riding.
05-28-10, 10:33 PM
You want a cog that has 32 teeth...
The biggest cog on the market is a 23. Also, you're going to spin A LOTTTTTTTTTTTTTTT for a short distance.
16:32 has the ratio of 0.5, which is quite pointless.
Unless you are on a 29er, 32:16 is really really low, might want to consider a taller gear.
05-28-10, 10:39 PM
Nah, that was just an example-- I was really thinking something like a 44:16 front/rear.
EDIT: You're still right- no one will sell a 44t rear cog for proper reversal. Damn.
05-28-10, 10:46 PM
You can buy a wheel with flip flop hub, have a 16 on one side and 17 on the other, you might be able to even use a 18.
This will lower your ratio quite a bit.
44/16 - 2.75
44/17 - 2.59
44/18 - 2.44
05-28-10, 11:10 PM
That might work, depends on what bike I pick up. Something new or good quality would deserve the price of a flip/flop, something cheap, keep it cheap.
This gear ratio debacle is what's killing me... I love everything else about the singlespeed ideal. How good is a 2:1 for offroading? And more importantly about what cadence would be necessary to pull 12-15mph on the street? What I really need is a bike that'll do at least 10mph at a reasonable cadence but still go offroad without being ridiculously slow/torturous. Obviously rock-climbs and impossible hills would involve pushing, but it would be nice if it could do a moderately difficult trail.
05-28-10, 11:29 PM
If you are going go with a 29er, 32:16 sounds reasonable but I have don't have much knowledge about mtbs.
Depending on the wheel size, but for a 29" wheel, you will have to spin 80-90 rpm to go about 14-16mph...
Play around wit this calculator.
Gear ratios are just bunch of numbers, just like what ichitz said, test the various combo with your own bike first. Figure out the gear ratio you like and go from there.
What size wheels are you planning to use?
Cheap = single speed, remove deraileurs, shorten your chain for the length that you need to pass it in the gears you selected and you're done, no need to remove the rear cassette or anything, when you have some money to spend (later on) you can do a complete conversion, in the meantime this way will cost you 0$ and will give you a good idea of if you like riding SS or not
05-29-10, 06:09 AM
The trick to converting a cheap single speed is frame selection. You want to find a bike that has a freeweel, bolt-on rear hub and horizontal dropouts.
1. Take off the multi-speed freewheel and replace it with a BMX freewheel - you'll also need a new wider chain.
2. Take off the extra front chainrings. The middle chainring on a triple or the inner ring on a double will generally yield a pretty good chainline and also the most appropriate gearing.
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