Building hub-geared disc-braked bike: a litany of questions

davis

I'm thinking of putting my first build together (for a friend), with an aim towards low maintenance, and I've got some questions. I've been reading a fair bit (mostly Sheldon), but I'm still after quite a lot of clarification.

I'm thinking hub-geared and disc brakes, and I've not used either before. I like the idea of putting them on a Cotic Roadrat or similar because the frame's flexibility means it'll be usable if I decide to do something else.

I'm thinking Alfine and Avid BB7s.


Hub gears:

They need either a chain tensioner or horizontal dropouts to get the chain tension correct, right?

The Roadrat has got horizontals (well, they look like track fork ends), so I can just slide slide the hub back, can't I?

Would I need a specific Alfine chainring? Surely any single chainring would do?

I understand I need a specific shifter (don't I?), but would a standard cable work? I quite like the idea of Gore because they're sealed, and apparently that's good.

I think I might need spacers or at least a method of getting the chainline straight. How do I find which spacers I'll require?

How low maintenance are they?


Disc brakes:

If I were to slide the hub back, presumably I'd have to adjust the position of the caliper. Are there bolts to adjust calipers' positions?

What wears with discs? Presumably pads, and eventually rotors, but how do you tell if they're worn, and how easy is replacement?

This one's an obvious one, but I can't find the answer. How are the rotors attached the wheel? I presume they bolt to the hubs somehow, but.. how?


General:

Would bottom bracket shell facing be required with a new frame? Does it matter with an external BB?

Is there such "facing" required for a head tube?

It'll be fine to simply hacksaw a steerer tube to the correct length, won't it?


Apologies for the litany of questions, but I've searched for the answer to most of these. This will be a slow build, as I collect cheap parts.

cheers

wgwarburton

davis wrote:

.. Hub gears:

They need either a chain tensioner or horizontal dropouts to get the chain tension correct, right?

Yes.

The Roadrat has got horizontals (well, they look like track fork ends), so I can just slide slide the hub back, can't I?

Yes.

Would I need a specific Alfine chainring? Surely any single chainring would do?

Yes, any would do. Tougher the better (1/8"? Steel?) if you want to mimimise maintenance

I understand I need a specific shifter (don't I?), but would a standard cable work? I quite like the idea of Gore because they're sealed, and apparently that's good.

Sorry, don't know about this one.

I think I might need spacers or at least a method of getting the chainline straight. How do I find which spacers I'll require?

You should be able to get a BB with an axle length to suit your wheelset. Find out what chainline your hub gear is designed for and match that to the BB.

How low maintenance are they?

Pretty low.

Disc brakes:

If I were to slide the hub back, presumably I'd have to adjust the position of the caliper. Are there bolts to adjust calipers' positions?

The frame claims to have slotted caliper mounts to facilitate this. It should just work....

What wears with discs? Presumably pads, and eventually rotors, but how do you tell if they're worn, and how easy is replacement?

Sorry, dunno.

This one's an obvious one, but I can't find the answer. How are the rotors attached the wheel? I presume they bolt to the hubs somehow, but.. how?

From what I gather the rotors have a set of (6?) hex-bolts that fix the rotor to the hub.

General:

Would bottom bracket shell facing be required with a new frame? Does it matter with an external BB?

It matters more with an external BB. I would hope a new frame would be prepped, but check with the supplier.

Is there such "facing" required for a head tube?

Again, yes but it may come ready.

It'll be fine to simply hacksaw a steerer tube to the correct length, won't it?

It's probably not the best way to do it, but I expect it can be made to work...

Cheers,
W.

The Rookie

I believe the Alfine hubs only take shimano star drive discs, although you can get star to IS 6 bolt adaptors if you want.

AIUI the gear change cable on the alfine is the same as any other gear cable, its only the shifter and what it attaches to that are different.

Simon

Craggers

Yeah Alfine hubs take centre lock discs, which as TB says you can get adaptors for to run standard 6 bolt rotors on...I'm also thinking of building up my P7 as a 'low maintenance/easilycleaned/less clattery on the trails' MTB using an alfine.

As for telling if your discs/pads are worn....you'd need a vernier caliper to check the thickness of the disc periodically. It will have a minimun thickness etched on it and obviously when it gets any thinner than that it needs replacing. Pads normally have a wear indicator on them, but if not you could probably measure them with the vernier caliper and check the manufacturers recommendations for minimum friction material thickness.

Hope that helps!

misterbleepy

davis wrote:

Hub gears:

They need either a chain tensioner or horizontal dropouts to get the chain tension correct, right?

They can also use a frame with an eccentric bottom bracket (EBB), though I guess these are rare (though I do have a spare one in my garage)

davis

Just a quick note to say thanks to all those who answered my many questions, particularly WGWarburton; that post was probably a hassle!

Thanks again