I was thinking of building up a single speed bike but with all the hills in my area I'm wondering about 2-speed possibilities. I haven't found much info out there on it but it seems like I could keep my two chainrings up front and two gears in the back. Anyone do this? Is there a formula for gearing that keeps the chain the same length?

https://harriscyclery.net/itemdetails.cfm?ID=2466

just keep a 4 tooth difference between your chainrings

You have a few options available If you are running a tensioner go with the melvin and leave the front dérailleur on and two chainrings. or a regular tensioner, And leave to cogs on the back separate them with a spacer And you will have to get off and adjust the tensioner to switch cogs, with both options you will only have a few teeth's difference.

Lastly if you are not running a tensioner check out the white industries DOS eno freewheel

Or lastly man up and mash it

Thanks, I think I got it figured out now.

If you saw the hill I live on top of you would understand the need.

One word: Retrodirect!

just mash! you'll have legs like a real man in no time at all.

+ a billion

schlumpf dual drive BB

mash it

Surly has a writeup about it for their dinglecog. A former employee at the shop I work at has a sweet 2 speed using a dual freewheel from whiteindustries. +1billionty1 on the retrodirect, you'll learn about a whole new muscle group.

Not rated for fixed use

-Rob.

you beat me to it.
funny, this is on an Iseran.



(pic is flipped)

I want to do retro-direct so badly. With left-side-drive and kangaroo cranks just to make the whole thing really over the top.

I solved the two speed problem with a Fichtel & Sachs Torpedo Duomatic 2 speed kickback hub with a coaster brake.There is a 36% difference between the gears. It is mounted on my 1980 LeJuene Track Bike.
It is pictured here: https://www.bikeforums.net/showpost.p...ostcount=20010

Unfortunately they have not been made for almost 25 years. I found mine on an old used bike ten years ago. And just this week a dumpster diving bike friend found a discarded very old 20 inch wheel bike with another one of the F&S hubs in excellent condition. Time for another bike project. Maybe a 2spd 29er! Good luck hunting one of these hubs. You will need it.

Man, speaking of the kickback, I found one in a pile of NOS parts at our shop, I was pretty damn hyped until the owner said he'd been saving it for his own project. Someday though, someday...

I have no knowledge of retrodirect, but I do run a dual single speed bike. I have 2 different setups. I have a White Industries DOS ENO freewheel with a 16/18t combo and a 16/19t combo. I almost never use my 16/18 since my 16/19 gives me a much better combo. I run a 45/42t front road crank which gives me a nice crusing gear and a decent, but not that low climbing gear.

As long as you reduce/increase the number of teeth on your chainring by the same number as you reduce/increase the number of teeth on your freewheel/freehub your rear wheel will stay in the same position. The best way if you have real hills in your area is to run a freehub body and so you have endless options of cogs to run, as well as being able to dial in your chainline perfectly. If you want a cleaner look with a rear wheel with next to no dish, go with a DOS ENO/freewheel hub setup.

Pics of bike/gears/chainline are here:
https://bikeforums.net/showthread.php...light=langster

HTH

Isn't there some hack
for a Shimano internal hub to make it
fixed like an old ASC

Zombie thread but since things have changed a bit over the last 5 years and I have tried both of the current hubs in both Freewheeling and Coaster forms I figured I would write a review of them

Sturmey Archer S2 or S2C,

I rode a freewheeling S2 for nearly 2 years and I have to say it works quite well. Especially if you are a control freak it's really easy to know what gear you are in while rolling the high gear is much louder when you aren't pedaling. It takes a while to learn to how much of a kickback is enough but spend a few hours on it and you should be fine. I wanted to switch to a Coaster so I tried a friends and was not happy with it at all every, time you brake you change gears, not a probelm if you are in high but if you aren't you have to remember to shift again before you start up. If you plan on Freewheeling the SA S-2 is a viable choice if you want a Coaster I would look at the SRAM. The Sturmey Acher's are available in 32h and 36h and lots of pretty colors ( Black, Silver, Red, Gold, Purple, and Turquoise)

SRAM Automatix

I actually tried a free wheel version before I bought my Sturmey Archer S2, I liked it I just liked the S2 more, the downside of this hub is you have no control over when it shifts, it changes gears at a set speed but the advantage is the shifts are much cleaner and acceleration is a lot better. The Coaster version of the SRAM hub really shines, you don't have to worry about downshifting when you hit the brakes, if you slow down below 10mph then it downshifts otherwise it stays in the high gear. climbing its a lot easier to downshift you let off just a bit and it drops down and then you can pedal again. Much more precise than the Sturmey Archer, I have about 25 miles of riding time on the SRAM now though it took me a lot less time to adjust to it than I expected. The SRAM hub is only available as a 36h but in addition to Coaster freewheel chain and belt drive as well as disk brake versions are available.

Weight wise the Sram coaster is about a half pound lighter than the Sturmey Archer coaster, I think the Sram freewheel version is 1/4lbs lighter than the Sturmey Archer though neither of the hubs is what I would call featherweight. Both use the standard 3 speed cog that is held in place with a retaining ring. The Sturmey Archer can take cogs from 13T through 22T the SRAM is limited to 15T to 22T If you change cogs replace the ring it's a safety issue and given the cost not a big deal at all. In theory they are both unsealed hubs and I have cleaned my S2 but it really didn't need it, the SRAM is even tighter looking as long as you don't submerge them, are you are riding a lot at the beach or on nasty winter roads you should be OK.

RD hooked up to a brake lever- hold lever in for low gear, release for high gear.

Even better- a locking bmx lever from the hopping no handed like an idiot era.