Suggestions for a drivetrain setup (NWT)

[Peter Fray]

Hello

I am looking to replace the IGH that came on my silk with a derailleur based drivetrain with a broad gear coverage. I will do small tours with this setup so spare availability is a priority. I have some components in mind but would appreciate your advice in general. 

- microshift 8 speed thumb shifters Shimano compatible (can friction 7 to 9)

- Altus rear derailleur - the big pulleys allow the benefit of a smaller cage and more clearance 

- 11-34 or 11-36 rear cassette 8 speed shimano

- front crank 2 speed - not sure of the optimal ratio here. The bike does not have a FD mount right now so I am thinking of the bigger chainring as the primary one I'll use for most roads and its ok if it's not very high. 

The smaller ring can be a bailout option for steep terrains and I can shift it manually with my hand. 

Does it look ok? 

(Would love to shift to a rohloff but it's not in my budget right now)

Thank you

P

[Access Dubious]

You could maybe look at an old 3-pulley Suntour rear derailleur. Should take up more chain than a 2-pulley derailleur with the same ground clearance. That would probably limit you to friction, though, as Suntour derailleurs have a different pull than Shimano.

I really like having the 62t big ring on my Air Friday. I like tall gears for the flats, and this lets me get those without going smaller than an 11 tooth cog in the back. I think you can get 60t rings in 130 bcd without too much difficulty.

[Eric Daume]

On my Crusoe with a single ring up front and a regular rear derailer, I seem to throw the chain every other ride or so. My next setup will be a clutch rear derailer. Microshift has a special group for small wheels, I’ll look at that. 

Eric 

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[John Thurston]

Peter, you might want to re-think this project.

AFAIK, the 'Silk' Fridays are built specifically for a fixed-length chain. The rear triangle has rearward-facing openings to accept the axle, and adjust the tension of the chain/belt. The rear triangle is 'unified' with the folding hinge placed ahead of the bottom bracket. It will have cable routing/stops installed to accommodate the hub for which it was built.

If you are going to switch this to a derailleur setup, you're going to need provide a rear derailleur hanger and suitable cable/housing routing/stops for it. An old-school derailleur 'claw' might kinda-work, but those are designed to work with forward-facing "horizontal" drop outs. You can probably fit something up to make it work with horizontal rearward-facing openings....but heaven help ya' when it's time to swap tires or tubes. You're going to have to un-hang the derailleur to get the wheel out :( And you don't say what kind of hub you have now, so we can't say if you're going to be able re-use the routing/stops for your new derailleur.

There's also the question of space in the frame for rear cogs. Let's guess and say your bike was built for 135mm rear axle spacing. You can't just assume that any ol' 135mm hub and cog combination is going to fit. The cog on your current hub is set nearer to the bike's centerline than the small cog on any cassette you install. That  cassette cog may foul on the chainstay, even though it is smaller than the cog you have now.

I suggest you find a hub, install a cassette, and see what sized cogs are an option in your frame. Then, hunt for a derailleur hanger which will work on the frame. Then see what sized chainrings will be needed to give you the gear-range you want with the cassette that will fit.

https://www.gear-calculator.com/

You mention "NWT", so I'm assuming this has 406mm wheels. In my experience, a 40t cog is the largest which can be fitted to a 406mm wheel Friday and still keep the rear derailleur away from the pavement. So if you can get the range that you want with a 34t or 36t, you shouldn't have too much problem.

A quick pic of your bike, and a quantitative statement of what gear range you seek, would help us give more specific (and helpful) suggestions.

-- 
John Thurston
Juneau, Alaska

[Wolfgang Ketterle]

I have just converted a Tikit from IGH to a 10-speed derailleur.   I used a Shimano Zee derailleur which has very low profile and good ground clearance.  It works very well on a 11-36 cassette.  To add a double chainring is more challenging --- you will then need a derailleur with more capacity which I did for a Brompton.  See my post at
https://www.facebook.com/groups/796190400521866/posts/3148541731953376/

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[Stephen Turk]

Wolfgang - that sounds like a good setup. My bikes have tended to migrate to 10-speed, which offers a good choice of wide range cassettes and other components. 8-speed and, to some extent, 9-speed are typically old tech and/or low end components. About the only exception I have made is using a 9-speed XT RD-M772 (Shadow) in a 10-speed build, since cable pull is compatible with 10-speed road STI shifters. And it comes in a mid-cage (GS) version for clearance.

Stephen Turk

SteveT...@gmail.com

(213) 300-4149

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[Peter Fray]

Thank you all for the replies.

I looked up the 3 pulley suntour derailleur - very interesting. Harder to come by and a little more expensive, probably will start with the Altus and grab a Suntour when I get the chance.

@Eric - do you know what causes the chain to throw off? I have looked at the microshift short cage groupset but it is tied into the system and you have to use advent specific cassettes and shifters

@John - thanks a lot for your very helpful comments. I mentioned NWT because that was my understanding that all BF Silk bikes are built around the NWT frame - except the rear triangle. The Silk uses a replaceable dropout - so the one for the current hub (Alfine11) can be replaced with a dropout that has a derailleur hanger. 

Thank you, also, I should read more about the chain line and do some trial and error to figure this out. I don't have the bike or the dropout with me at this moment but I will share pictures soon.

@Wolfgang - did you also have to change the drouput for this? Did you have any issues with what John mentioned? and what size front chainring are you using? Thank you for sharing.

I am thinking of getting a budget LitePro crank, the ones that BF uses, for initial trials.

best

p

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[David Dillard]

Peter--

Which Silk did you end up with?  There are two types -- Bike Friday first came out with a monostay rear and later came out with a more traditional looking rear triangle with seatstays that had a hidden split so they could accomodate a belt drive.  Mounting a front derailleur is tricky.  If you wanted a derailleur hanger it would probably be a special order item.  Occasional manual bailout shifting is a good idea.

Things I have in my basement, but haven't tried yet:

      Deore XT bottom bracket mounted front derailleur -- I think this will work but maybe not for very large chainrings.

      Microshift group with the short rear derailleur microSHIFT Advent "Super Short" Flatbar Groupset, 9spd – Velo Orange (velo-orange.com)

I also have a Sachs 3x8 wheelset which would eliminate the need for a front derailleur and be pretty reliable.  But not in tune with your no IGH intentions.

David Dillard

Louisville

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[robert clark]

Silk NWT being capable of belt or chain drive IGH, a Rohloff hub is quite renowned for its reliability

& no chain tensioner needed...  wear  on just 1 cog  - in a 20" wheel a 16:53 works quite well.. 

in my Llama I must use a chain tensioner. so no long wearing 1/8" chain..  

[robert clark]

eliminating the IGH option  every thing else  is just ratio math picking cassettes & chainrings

[Wolfgang Ketterle]

Peter,
my Tikit has 135 mm rear width, and I could exchange the dropouts against dropouts with derailleur hanger (from Bike Friday).
My front chainring has 60 teeth --- so I have 60 front, and 11-36 rear.
Wolfgang

[Peter Fray]

@David - hey! I got the newer version with the rear triangle. The original owner had ordered the replacement dropout and passed it on to me. Yes, would like to avoid an IGH for now...

@Wolfgang Ketterle - I think this might be similar to what would work for me. What's your crank and bottom bracket? Thank you...

P

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[robert clark]

Sram dumped the dual drive manufacturing,   Sun Race - Sturmey Archer  is the only one left

To have much of a ratio range  requires that long cage RD pulleys & chain, are down near the dirt.

[robert clark]

a 2 speed crank  the overdrive gear is 1.65X the physical chainring... 

[J. Nathan Matias]

Hi P,

Good luck with the conversion! 

What IGH does it currently have? I might be interested in an Alfine 11 wheel with disc brakes as a spare if that's what you have.

All the best,

--Nathan

[Peter Fray]

Hi Nathan,

Thank you! 

Yes it's the Alfine 11 with disc.

I'll write to the group when I get up to making the swap. 

Thanks 

p

[robert clark]

Personally  wonder what so dreadful about the alfine 11 speed?

On Wednesday, November 15, 2023 at 9:38:06 AM UTC-8 robert clark wrote:

With new NWT the rear fold is above the BB , so chain tensioner (Silk Version ) is on the frame

as BB and hub are in the same portion.

with the prior* fold behind the BB  the chain tensioner screws into the Derailleur hanger

* And Llama, Alpacka  etc.  

[J. Nathan Matias]

Hi Robert,

Great question!

The OP said spare/repair availability is the concern, which is one of the trade-offs for any IGH. On one hand, I've done over 12 thousand miles with my Alfine 11 no problem. This seems in line with reliability data on models from the last few years, and I actually feel more trusting about it than derailleurs, especially given the risk of damage to derailleurs and frames in suitcase transit.

But I can understand the uncertainty. While all Shimano service centers have training on these IGHs, not all of them have the parts, so I get it. People know their own needs/requirements, and I trust that.

Peter, thinking about all the effort to convert an IGH frame to derailleur, I actually wonder if you might have more luck swapping with someone, since IGH models are so in demand (and Alfine 11s have been hard to come by in general). Unless the fit is highly customized, you might find someone with a comparably-sized derailleur Bike Friday who would be willing to do a swap, saving you considerable time and energy.

--Nathan

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[robert clark]

Are Alfine  IGH prone  to fail . Heard as lot of instances of that?   What are the sources?

[robert clark]

A second had Rohloff  is what I Got..   that was 2008  Its still OK... 

My Bike Friday  uses 32 spoke  406 rims... 

[robert clark]

A Few years back  I chatted with 2 young guys from Sweden Touring on Commuter bikes

 with Shimano 8 speed hubs , they had started in Anchorage Alaska 

 , I'm on the Oregon coast   ... they were flying home from Florida, as a destination

Author Dervla Murphy  for her trip from Ireland to India . she said  the 3 speed  may not be reliable 

so did the whole trip on a one speed... 

Through Afghanistan's Mountains,...

Talk about a Push-Bike ! 

[J. Nathan Matias]

Yeah, the word on Alfine 11s is that they are not as reliable as the Rohloff (but what is?)

Alfine 11s are susceptible to cable adjustment problems that harm the internal gears and cascade over time. So either you are very careful about alignment (which needs almost no adjustment once your cables stretch), or you get electronic shifters, which don't have the problem. Some hubs leak oil, though I haven't seen this in either of mine. Other people worry about over-torquing them, and I'll admit that I only really go up to ~650 watts in sprint training as a pretty small rider, so I probably haven't put mine through a true torque test.

And then if some manufacturer problem, fluke, or preventable error happens on a tour when you're far from a bike shop with IGH experience, you have to wait while you mail your wheel to get looked at. So I get why some touring cyclists swear by them and others prefer to go with a derailleur.

--Nathan