Quantcast

Gearbox bike questions

Damo

Damo

Short One Marshmallow
Sep 7, 2006
4,603
27
French Alps
I'm looking at building up a gearbox bike over the winter and have a few questions:

Do I need a single speed rear hub? Will a Hope ProII SS work?
What would be a good size chainring & sprocket?
Do I need SS specific chains?

Cheers
 
N

NoUseForAName

Monkey
Mar 26, 2008
481
0
Dont you want a fixed hub for the rear wheel? Ie no freewheel. Keep the spacing of the back end at 135 and you've no worries there, lots of cheap, sturdy options.
 
fluider

fluider

Monkey
Jun 25, 2008
440
9
Bratislava, Slovakia
Unfortunately, all current SS hubs (including fixies) come with either bolt-on axle or standard threaded axle. Maybe there're some QR ready ones. It depends on intended use of the bike but he may need thru-axle for stiffness.
 
Sandwich

Sandwich

Pig my fish!
Staff member
May 23, 2002
21,671
6,888
borcester rhymes
Depending on the gearbox, you can use either a fixed hub or freehub. I don't know which the gboxx has. I know that on the lahar, some riders complained about drivetrain lash because there are two freehubs, one in the hub and the other in the gearhub.

HaveFaith uses !zipties! to secure his freehub and turn it into a fixed gear. I think your best options are to either use a VERY fast engaging rear hub, like a Stealth roller, or to convert a freehub into fixed hub with something that can break free if the wrong sort of stress is applied.

Otherwise...you don't NEED a singlespeed hub, you can run just one cog with spacers. You want to run the fattest and strongest chain possible, while maintaining low weight...ie, skip the 9 speed but you don't need a BMX chain. I would try and keep the rear cog slightly smaller than the front, if at all possible, to prevent pro "squat" or whatever the flavor of the day is.
 
SuspectDevice

SuspectDevice

Turbo Monkey
Aug 23, 2002
4,204
429
Roanoke, VA
We are planning on spinning a batch of 150x12 fixed hubs over the winter for this application. If you use the Universal Transmissions box, a fixed cog really improves the shifting, and a fixed-specific hub is SOOOO much lighter than something with a freewheel...
 
fluider

fluider

Monkey
Jun 25, 2008
440
9
Bratislava, Slovakia
SuspectDevice said:
We are planning on spinning a batch of 150x12 fixed hubs over the winter for this application. If you use the Universal Transmissions box, a fixed cog really improves the shifting, and a fixed-specific hub is SOOOO much lighter than something with a freewheel...
Click to expand...
Ehm. What chainline will it have? And sprocket thread diameter? Are you planning on machining sprockets, too (what sizes)? I've designed 135x10 fixie but can't decide about the sprocket offset. But I need a thru axle design. The hub has cca 46.5mm chainline as displayed on images.
 
Last edited:
H

HaveFaith

Monkey
Mar 11, 2006
338
0
fluider said:
Ehm. What chainline will it have? And sprocket thread diameter? Are you planning on machining sprockets, too (what sizes)? I've designed 135x10 fixie but can't decide about the sprocket offset. But I need a thru axle design. The hub has cca 46.5mm chainline as displayed on images.
Click to expand...
The hub will actually be able to be used with both 135mm and 150mm spacing and 10mm or 12mm axles. The chainline is 60mm for the gboxx, so you cant use off-the-shelf 135mm fixed hubs. I would say it is a requirement to use something that is fixed. This hub is going to weigh less than your hope pro2 or king 20mm front hub, or roughly 1/3 lb less than a standard rear.

That being said, you could take a standard free-hub in your sizing and then braze the pawls inside the mechanism to the ratchet teeth. Viola!, a fixed hub...
 
Last edited:
You must log in or register to reply here.
Top Bottom