Fixed gear with 2 gears

Team Banana Spokesman

possible to have 2 chainrings + front mech?

possible to have a flip-flop hub with different size cogs?

Brindy

I dont think it would work as fixed chains need to be under same tension so would need a rear mech to make up the tension on the chain.

Tail end Charlie

The front mech wouldn't work but the different size cogs on the hub would as long as the cogs aren't too different in size and there is enough adjustment to take up the slack.

AidanR

2 solutions that I know of:

1. A flip-flop hub as you stated

2. A Schlumpf Speed Drive (internal 2 speed gearbox inside the BB shell instead of 2 chainrings and a front mech)


There's a third, but it's singlespeed and designed for mountain bikes:

3. White Industries Dos freewheel and chainset

N0bodyOfTheGoat

The Sturmey S3X, 3-speed fixed?

lae

Surly Dingle



IIRC you need about 3mm of dropout for each tooth, and the cogs are 3 teeth apart, so you need a 9mm long dropout plus the width of the axle - so quite a long dropout. You also need a 3/32 chain and therefore a 3/32 chainring. Chainline will be a bit off.

A good alternative to a flip-flop hub, and easier to change gear with it.

andrewgturnbull

Team Banana Spokesman wrote:

possible to have 2 chainrings + front mech?

possible to have a flip-flop hub with different size cogs?

Hi there.

Better to go with 2 different cogs, rather than chainrings. Each time you change the total number of teeth that the chain goes around you'll need to move the wheel in the dropout. A one tooth changes in the number of teeth in the cog will have more effect on your gearing than a one tooth change in your chainring.

Unless you run a really small gear!

Cheers, Andy

andrew_s

frinkmakesyouthink wrote:

Surly Dingle
IIRC you need about 3mm of dropout for each tooth, and the cogs are 3 teeth apart, so you need a 9mm long dropout plus the width of the axle - so quite a long dropout. You also need a 3/32 chain and therefore a 3/32 chainring. Chainline will be a bit off.

A good alternative to a flip-flop hub, and easier to change gear with it.

What some people do is pair a dingle (eg 14/16) with two chainrings (eg 44/42). You can then run the same chain on either the inner 42/16=70" or outer 44/14=84" runs, with no axle movement needed except as slack while moving the chain.

[edit]
They are actually available in 17/19, 17/20 or 17/21

lae

^ that's really bloody smart.

GarethPJ

Or if you happen to have your own machine shop...

http://sheldonbrown.com/awfixed.html

Always fancied a go, but I didn't find out about this until years after I stopped working in a machine shop.

As for the Dingle and two chainrings? Clever, but expensive. I prefer the old way of doing things. Back in the day a flip-flop hub with two separate sprockets was almost standard fitment for many. Obviously you need fore and aft adjustment, but most frames have pretty long slots. Even riders in le tour would use this setup, one gear for climbing and one for the rest. It must have been fun at the summits when they all stopped flip their wheels together.

andrew_s

GarethPJ wrote:

Or if you happen to have your own machine shop...
http://sheldonbrown.com/awfixed.html
Always fancied a go, but I didn't find out about this until years after I stopped working in a machine shop.

A Sturmey S3X would be cheaper than setting up a machine shop

GarethPJ

andrew_s wrote:

A Sturmey S3X would be cheaper than setting up a machine shop

I wasn't suggesting you set up a machine shop, just that if you happen to have access to the tools you could do it yourself. Back in my days as a petrolhead I worked in a machine shop which meant I could machine a lot of my own parts effectively for free. A lot cheaper than buying modified parts!

It may even be cost effective to get your local precision machinist to do the machining for you. Some shops will do little jobs like this incredibly cheaply if you're willing to wait for them to fit them in with another job.