2wheelcommute

I'm putting together a build around a new Shimano Alfine 11 internally geared hub (specs here: https://www.kstoerz.com/freespoke/hub/190).

I already have a Shimano Tiagra FC4500 crankset set up (https://www.jensonusa.com/store/produ...+Crankset.aspx), which has two rings (39-52).

Obviously, since I'm going to run an IGH, I only want one chainring. I was thinking of going with a 42T chainring (and a 22T cog).

I have a few questions:
--Can I just remove the current chainrings and put any 44T 5-bolt chainring on? Do I need to get a fixed gear/single speed-specific chainring for any reason (if such a thing even exists)?
--Am I going to have any problem with the chainline? I had assumed that I could just throw a new chainring on my current cranks, swap out the hub, and the chainline would just sort of line up. Is this assumption off base? There's no chance I'd need to get a different crankset, is there?
--I assume I'll need a fixed gear/single speed chain, right?

fietsbob

You may be able to use an inner of a double chainring,
though Surly's Stainless steel chainrings are very nice.
[that's what I used on my Rohloff Hub bike]
Older pre index chainrings may work .. its the rampe and shifting aides you want to avoid.

chain .. match the cog on the hub .. 3/32" or 1/8''

single speed chains don't need the short flush pins that derailleur chains have featured

you can use a wider 1/8" chain on narrower 3/32" chainrings

Grand Bois

You really believe that ramps and pins on the side of a ring will have some effect on the chain when that ring is used as a single? That's ridiculous! The chain will never contact those ramps and pins. The fact the teeth tend to be shorter doesn't cause problems either.

Don in Austin

I just built a bike with the 11 speed Alfine. Loved it, but, sad to say, after no more than 100 miles, I just sent the hub back to Shimano as it started to go south inside. We shall see how good their warranty service is and how the replacement holds up.

Don in Austin

2wheelcommute

Thanks for the early feedback, folks.

Don, I'm so sorry to hear about your bad experience. 100 miles? Damn. I'd be very interested to hear how their warranty service is an how the replacement holds up.

Monster Pete

I use old-type 5/6/7-speed chain that was originally on my bike with a 3-speed IGH. I even still have the triple crankset. As long as the chainline is fairly good and the chain isn't hanging loose, you shouldn't have a problem. I would just keep the double crankset you have, maybe filing down the teeth of the larger chainring to make a chainring guard as a few others have done.

Boye

Keep your 39t ring and get a 20t cog instead. That would give you a gearing very similar to 42-22.

Cross Creek

If the 11 spd Alfine uses the same cogs as the 3/7/8 spd Nexus/Alfine hubs, you can mount it with the teeth facing either inward or outward (makes more sense when you see it in person). This allows quite a bit of chainline adjustment. +2 on using the inner 39 tooth chainring and turning the outer into a guard, but there are lots of options, some requiring a shorter BB spindle, and yes, there are certainly single speed chainrings available. BTW, chainrings come in different bolt circle diameters, so they're not all interchangeable by number of bolts--measure your center to center bolt distance (in millimeters) between two adjacent bolt holes if it's not marked on the spider or chainring.
CC

2wheelcommute

Hadn't even considered different center to bolt distances--thanks for the tip.

The only reason I was thinking about 44/22 over 39/20 was because most of the chainguards I've been looking at are for larger 44T chainrings. I suppose there's nothing stopping me from using a larger chainguard and smaller chainring, though, right? (although it seems that it may look a little odd...)

fietsbob

Bigger chainguard can be a more effective greasy trouser leg protection.

Cyclocrossworld.com has a bunch of chainguards, nicely finished in black annodize.
https://cyclocrossworld.stores.yahoo....okalchain.html

I got a 110- 38 for my R'off bike , replaced the Stronglight Mygal which has a 130 39t guard.
Self extracting fixing bolt stripped out the crank arm without budging it.

2wheelcommute

Hmmm, I was thinking of a chainguard that offers more coverage (at least a "hockey stick" style one--maybe one like this: https://www.amazon.com/SKS-22907D0400...9096108&sr=1-8). They seem to be made pretty exclusively for relatively larger sized chainrings.

You've used the circular chainring guards--are they fairly effective (against both staining and catching a pant leg)?

Monster Pete

The circular guards do a fairly good job in my experience at keeping clothes out of the chain. Your trouser leg may get a bit grubby though from the upper run of the chain. You should get on alright with the linked chain guard as this covers the upper chain as well as the whole chainring. Although it is listed as for 42-44 tooth rings it should still protect a 39t.

2wheelcommute

Got it. Thanks.

chucky

-You need to replace your chainring bolts with "short"/"single speed" chainring bolts.
-The drivetrain will be more efficient if you sort out the chainline. However, you don't have to do it. After all derailleurs always operate with bad chainlines and IGHs are much more robust.
-You don't need fixed gear/single speed chain. In fact, IMO with the Alfine 3/32" "8-9 speed" chain is preferable...although 11/128" "10 speed" chain will cause problems.

Mr IGH

I just measured my Tiagra double cranks, if he used the inner ring position on the cranks and flips the Shimano Alfine cog inward he'll be within a millimeter or two of perfect chainline.

chucky

In addition to the cranks themselves, with square taper bottom brackets the spindle length and taper (ISO vs JIS) will also affect chainline. Splined bottom brackets fortunately do not have taper, but I'm not sure if they have different spindle lengths.

If the OP really wanted to perfect the chainline he could also get a mm or two of additional adjustment by using a non-Shimano cog. There's a table for adjusting chainline via cog selection here:
https://www.hubgear.net/sprockets.html

Mr IGH

Sorry, I assumed his cranks were Tiagra 2 piece cranks, if it's a 3 piece set-up you're right.

fietsbob

Hebie chain-gliders enclose the chain fully,plastic, in 38 and 42 t sizes, the back portion either
for Shimano Or Rohloff IG Hubs.

2wheelcommute

Nice! Yeah, I've got the 2 piece.

And thanks everyone else for your great suggestions too. Those Herbie Chaingliders look great--I hadn't seen those before.

relyt

You can get chainring spacers for additional fine-tuning, or just use washers. I would try to do that before messing with the BB.