Weird gearing question... is this possible?
 

Im gonna start off by saying that Im totally new here(obviously) and new to singlespeed/fixed gear bikes as well. I've been riding BMX for 10 years, but never anything else.

A friend of mine is donating me his bike(an SE 700c Draft), and while I know it's a cheap, kinda crappy(or so it seems) bike, it's free and it would be sweet to have something to cruise around town and to/from work on so Im gonna ride it until I have some $$ to dump into something nicer.

I have a Profile cassette hub(9t) and a spare 25t sprocket. In theory I could lace this hub to a wheel and use the 25/9 gearing correct? My main concern is that the hub might be too wide for the frame...


Would this work?! My only real reason for wanting to try this is to make use of some parts I have laying around, and that it would look pretty sweet and I've never really seen it. Unless Im just living in the dark(totally possible). Or would there be any other way to run 25/9 gears?


Thanks!

even if it is possible you're not going to solve your "parts lying around" problem

just sayin!

Care to elaborate on that? lol What am I missing?

^ I think they were implying that you'd have to take parts off of the bike to put your parts on that you have laying around, thus leaving you with the same amount of parts laying around.

Also with chainring and cog that small, you're more likely to have chain slip and/or axle slip problems, not to mention wearing chains, cogs, and chain rings out more quickly.

LOL yeah, good point. I would still have parts laying around. But I wouldnt have GOOD parts laying around so it's not so bad.

Granted this was on a BMX bike, but I've put a TON of miles on this setup without any real wear problems so I dont think it would be much of an issue. It's not a freewheel though, so I would definitely have to lace this hub to a wheel(they're both 36h so that's easy). I dont know of anybody who makes a 9t freehweel. 13 is the smallest I've ever seen.

The spindle size on the cranks are an issue and unfortunately one I wont know until I pick up the bike from his house. Im sure if the spindle is smaller than the size of the chainwheel I can find an adapter(as long as its a common size).

Thanks everybody! Ill be sure to post some pictures of this Frankenstein if it works out.

I don't mean to sound rude, but I'm curious as to your goal here.

I understand going for a smaller cog in the back if you want more gear inches, or a smaller chainring in the front if you're going to be doing lots of hills, but relacing a wheel and replacing a chainring to get a smaller cog and smaller chainring seems like a great deal of work for minimal benefit.

Check the current hub. It's probably a flip-flop, in which case you currently have the option to run the bike as a fixed gear if you flip the wheel around (if it's not already in that position).

If you replace the hub with a cassette, you lose the chance to have a fixed gear at your disposal if you want it.

If it's currently run as a single-speed, it would probably be more fun and less work to unscrew the wheel and flip it and ride fixed, but you may have other goals in mind.

Is the 9 tooth a driver off a bmx hub or is it a cog off of a multi speed free hub cassette? If its off of a cassette, you can either lace that hub up to the rim you have on the bike now or if the cassette is already built up you can just put that on the bike. It will no longer be a fixed gear, but a singlespeed. I think it would look kinda cool if you could pull it off.

bigvegan- I understand your curiosity totally. There's nothing in particular I want to "accomplish" other than doing something unique and fun. I will lace the wheel myself and I love working on bikes so it's no big deal. From what I hear, the wheels on that bike are pretty bad stock, and the hub I have is amazingly smooth and WAY better quality. I dont mind losing the option of going fixed gear as Im not likely to ever want to go that route, and Im only going to be riding this bike until I can afford a nicer SS(hopefully this summer).

PistaRider311- It is a 9 tooth driver off of a profile race cassette. It's not on a wheel right now so I am just going to lace it to the stock rim and run with it. I think it will look cool too. Different at the least!

There's no way you can bolt a 25 tooth chainring to the stock cranks of the Dawes, it's simply too small. If the bike is a temporary measure, why not just ride it as is?

It's actually an SE draft? Same parts? I actually have a set of 3pc cranks with a Euro BB on an old bike that i know the chainring will bolt to. Like I said before, its more of a fun little project, just to see how it rides/looks.

What's the spacing between the dropouts? I think the main physical limitation here is whether the hub is going to be wide enough, given that you've got already got the euro bb sorted.

One thing to keep in mind is that 25/9 gearing is going to be a lot higher on 700c wheels than it is on a 20". We're talking like 74 gear inches vs 51 or so, which is a bit of a leap. There's going to be a lot more stress on the teeth than there was with the same gearing on the bmx (you might very well end up trashing the driver and/or sprocket the first time you need to haul up a hill). It'll also be hell on your legs going from 51 to 74.

Assuming the hub will fit in the dropouts, my suggestion would be to scrounge up a 22t sprocket and use that, if you're set on the 9t driver. 22/9 on 700c gives you about 65 gear inches, which is probably a better starting point coming from bmx. It's high enough that you won't be spinning out constantly (especially since you'd be used to coasting downhill anyway) but low enough that you'll be able to get rolling fairly easily and climb the odd hill or two.

Oh -- does that profile hub take a 14mm or 3/8 axle?

Thanks ascend. Im going to measure the space between the dropouts when I pick up the bike. He's out of town right now. The hub is Profile's race hub so its a 3/8 axle. I built up a race bike a long time ago and never really rode it much. Too light and not for me. So I sold most of the parts but still have rear wheel parts sitting around. I've got a 22t Animal chainwheel on my bmx bike right now. I may switch cogs on that wheel and run 25/9 on that and 22/9 on the SS.

Thanks for the help everyone!

I think you have you terms mixed up.

This is a driver for a bmx freecoaster hub:

http://www.customriders.com/prod_imgs/FWAL10606.jpg

This is a cog for a freehub cassette (which it sounds like you have):

http://www.ykkbikes.com/files/parts_prodcassetteCog.jpg

It's a driver like the one below. When I bought the hub it had a 13t cog. I replaced the entire driver to go down to 9t because they only sell cogs 12t and more.

http://i14.photobucket.com/albums/a3...mid_461110.gif

He has a 9t driver for a freehub/cassette hub. The 9t driver is one piece that completely replaces the freehub mechanism and the cog, which is what allows it to have such a low tooth count.

A freecoaster is an entirely different beast yet again -- it's similar to a coaster-brake without the brake, and allows you to coast both forwards and backwards without the wheel driving the pedals.

Read carefully, bmx parts are tricky. :P

LOL yes, ascend, they can be tricky. Like I said, typically most bmx cassettes only go down to 12 or 13 teeth. I did a 1 piece driver on this hub, as well as my Odyssey Hazard Lite that's on my my street bike(Macneil Heaton). I tried a freecoaster once... I couldnt get used to it. Shortly thereafter it broke. HA!

man i think a tarck bike with some micro gearing would be gangster!!!!! its going to make the over crooked pedal grinds easyer!

LOL I was thinking something more along the lines of some disasters on a huge concrete barrier. Im sure it will last a LONG time! :roflmao2:

haha ya disasters was the first thing i thought of.! Id say do it. i have a 32 11 set up hanging around thats going on my future polo bike. primo cranks with a hazard rear hub. WORD!