UTMC

so, ive decided to convert a donated mountain bike to single speed. its actually kind of a nice bike, an early 2000's gary fisher mamba. the rear derailer was missing when i got it, and ive always wanted to learn more about tinkering with pedal bikes, so this type of project seeems like a good primer.

i got a bmx freehub for the rear, knowing i'd have to play with spacing on the rear axle and redishing the wheel. any suggestions here would be appreciated.

also, i'd like to be able to replace the front sprocket (chainwheel?), but i *think* i might have to replace the crankset to be able to. the present ones are riveted on and have a 77(ish)mm bolt circle, which i'm not really finding much in the aftermarket for.

thanx

adam

Please allow me to introduce you to yuor new best friend.
The late, great, Sheldon Brown.

http://www.sheldonbrown.com/singlespeed.html

Everything you need to know, and then some.

+1 to what my colleage Picinni said, I converted an old Raleigh road frame to a fixie/swap freehub years ago (in fact it was just stolen two weeks ago) with parts from Sheldon Brown. Don't read the poetry, though.
Anyway, the first thing to look at is the type of rear axle dropout your frame has. If the dropout is vertical or nearly so, don't waste your time. Mtnbike frames are typically vertical, sorry if that's what you've got. You need to have a horizontal dropout (or very nearly horizontal) so you can move the axle forward and back to adjust chain tension, something that on a multispeed is normally handled by the springs in the derailler. As to your second point, unless you are concerned about cool-factor, I wouldn't worry about the front chainring, just use the larger ring and leave the assembly riveted together. If after riding it for a while you enjoy it enough to want to go further, THEN swap out for a single-speed crank.
Good luck, singles/fixties are great fun and a hell of a workout.

piccini9 wrote:Please allow me to introduce you to yuor new best friend.
The late, great, Sheldon Brown.

http://www.sheldonbrown.com/singlespeed.html

Everything you need to know, and then some.

Link badassery! Good stuff!

That is some very good and helpful info there. Good link.

Bigshankhank wrote: Anyway, the first thing to look at is the type of rear axle dropout your frame has. If the dropout is vertical or nearly so, don't waste your time.

Not true, if you are doing single speed (freewheel) this item will keep the chain tensed.



Pattio is a long time fixie guru, I'm sure he will chime in.

One of the funny things about getting into fixed gear or single-speed bikes is that you make the argument that you are all about simplicity, and you don't need all those gears (or brakes) diluting your pure experience, maaan. You then get to obsess about every remaining nut and bolt on the bike to an even greater extent.

If you just want to get a non-moving bike moving again, but don't want to get into speccing out a complete single-speed setup at first, just hack the original drivetrain so only one gear works. The chain tensioners MATPOC pictured do the same job that a derailler does- which is to say, any old derailler can do the same job. If you have the bike's original wheel and gear cluster, just use it and don't worry about re-dishing at first.

If you get the bike working and are enjoying it, then you can start looking at making your bike a 'pure' single speed, by choosing a single-ring crank (with replaceable rings), setting up a single-speed wheel with appropriate dishing, etc. As has been pointed out, a bike with horizontal dropouts makes for a cleaner setup with no need for a chain-tensioner. Watch the economies carefully- you can buy a complete single-speed bike for pretty short money these days, and approach that cost pretty easily just by buying a rear wheel and drivetrain to upgrade an older bike, so there's no need to go big on that stuff.

thanx guys. i'm hip to the sheldon brown, almost to much info, thats why i asked for a lil input.

the problem with the bike is that the derailer is all mangled, so last night at my local bike shop i, coincidently, bought the surly piece that matpoc showed. later last night, if not by divine intervention, i found a single speed crank (http://aebike.com/page.cfm?action=detai ... SKU=CR8156) for low bucks on craigs list, prolly gonna go get it tonite.

after all that, all i should need is a chain and some tuning!

i would like to get a rigid fork for it, as the bike has a real low end suspended fork inplace. we'll see.

thanx again.

Ive been waiting on misc parts for the single speed, in the mean i've been riding a 25 year old trek "race" bike almost every day for the last week; i think i've done almost 100 miles.

I've never ridden a bike with drop bars for any significant distance in the past and, its sorta weird, so there's been a bit a lil bit of sore honeymoon between me and the ole' girl.

BUT, and this is a big but, the bike is quicker than anything i've spent time on and handles fast and crisp. A little intimidating.

i'm hoping it doesn't snow a whole lot this year so i can continue to peddal the narrow ass tires.

http://i891.photobucket.com/albums/ac11 ... 1259601280

( i cant make the image thingy work today, i blame it on me. i brokethe screen off my mac laptop and now have to use a bullshit PC. fuck windows.)

Dood you need to re-adjust those handlebars. Rotate them back towards you so the bottom part of the drops is parallel with the ground, or perhaps 1 or 2 degrees up from there. Then move the brake levers down until the tips of the levers touch the plane of the handlebar bottom. Then adjust your seat so that it is parallel with the ground, but slide it straight forward a little bit as well. Finally, those tires look original, which is to say they are old enough to vote. Make sure they are not dry-rotted or fraying. This stuff is important, and jumps out on a pretty sweet bike.

That reminds me of my Diamondback race bike. I still dig downtube shifters.
Yes, new tires/tubes, probably replace the chain, too. Otherwise it looks good.

thanx pattio, bars/levers/seat remedied and the magical UPS tracking goodness tells me that my new tires will arrive soonly!

If you like riding this bike, I would suggest riding it all winter long. Make note of what gear you like to be in most of the time, and when the time comes that the drivetrain is all gunky and worn out, that bike would be an excellent candidate for fixed-gear conversion. I myself prefer fixed with skinny cyclocross knobbies in winter conditions, because I believe they 'dig in' while chubby mountain-bike tires tend to 'float', at least imho. But if the bike is riding sweet and shifting sweet, ride out that buttery Japanese drivetrain for all it's worth before you consider the change.

That is a sweet bike! A bit tall for you it seems, but that never stopped me before, in fact most of my bikes are too tall for me.

+100 on the tires, they are paper thin and when they blow they BLOW!