williaty

The 110mm BCD should support a 33T chainring but I've been having trouble finding one. T.A. Specialities makes a 33T 5-bolt 110mm BCD but their only version of it isn't ramped and pinned. Does anyone know of a company that makes a 33T ramped and pinned? The setup I'm trying to put together is marginal enough that the difference between 33T and 34T actually does matter for front derailleur clearance.

Andrew R Stewart 

Since the general lower limit for ring teeth on a 110 is 34T consider it fortunate that someone has offered anything less then 34T. The day of ring selection by each tooth has gone years ago. Just like with cog sets, the economics of a wide selection of tooth counts for each position just don't make business sense to most every company in this business. Andy

dsaul

Is this for a Double chainring setup? If so, there is no need for ramps and/or pins on the small chainring.

delbiker1 

I have found this to be true, and they are less money then ramped and pinned rings. I have them on my triple, middle and small, also.

williaty

It's a triple and the granny-middle shift is huge, prompting me to want the ramps and pins for every little advantage I can get. If everything works out, I'm going to be running a 17-33-44 triple with a 13-42 10spd cassette.

HillRider

Wow, that's 56 total teeth! Your going to need a hose reel for a rear derailleur to wrap up all that chain. Assuming 700c wheels that's an 11 gear-inch low gear. Do you really need that low a gear or is this for a trike?

williaty

The RD won't take that much chain. Chain length will be set so nothing is destroyed if it's accidentally put into big-big and then will fall slack about half way through the cassette when in the granny ring. The goal is just to keep tension on the chain in the granny ring up to a small enough cog to get a ratio overlap with the middle ring.

26" rear wheel so I'm looking at about ~10.5 gear inches, which isn't unusually low for loaded touring in a recumbent tadpole trike. I currently have a 22T granny wit the 42T cog in back and it's nowhere near low enough.

williaty

To quote your for a 2nd time, the only reason I'm using a 44T big chainring is to work within the limitations of the capacity of the rear derailleur (47T capacity) well enough to keep tension on the chain in the granny. If I could figure out how to add a 2nd chain tensioning device to the system, I'd REALLY prefer to run something like a 52T big ring to get more top end because on my current drivetrain I spin out of 44-13 on surprisingly flat terrain. It'd be nice to pick up another 5mph or so before I spin out.

williaty

You missed the earlier replies where I did in fact clarify that this is for the middle ring of a triple.

JohnDThompson 

Yes, you're right.


But still, ramps and pins are really only an issue if you are using indexed front shifting. Are you?

williaty

No, friction bar ends. However, the size of the planned jump means that ramps and pins will help it be easier to climb up 16T in a single lift vs just smashing the crap out of the chain sideways and hoping it works.

dsbrantjr

This has a 2.5:1 reduction capability: rehab drive - schlumpfdrive - ultraflat Planetary Gear for Bikes

CliffordK

I'm not convinced a "shadow" derailleur is hurt by running a short chain. I've hit it once on a bike, and it simply failed to jump up. Of course, if one does catch the chain, one might rip the chain apart of one puts too much power in.

williaty

It's also (sadly) absurdly expensive otherwise I'd totally be down for it. My dream setup is a Schlumpf Mountain Drive mated to a Rohloff. Sadly that represents like 5 years worth of savings, so that's never going to happen.

tomtomtom123

SPA cycles has 33T inner/middle chainrings that have ramps and pins. I've tried the 46T and it shifts pretty well. I cannot remember whether the thickness was 4mm or 4.5mm.
https://www.spacycles.co.uk/m2b0s210...l-Middle-Inner

HillRider

OK, that's what I thought and I understand that a for a trike there is no such thing as too low a low gear. BTW, there are cassettes with 50 and 52T big cogs intended intended for 1X deivetrains but should work for your purposes. Your current 22T granny with a 52T cog gives the same 11 gear-inch low.

williaty

I couldn't find anything bigger than 42T for 10sp. All 52T kits I could find were for 11sp. 10sp is already stupid (for my purposes) so there's no way I'm going to 11sp. I'd love to drop back to 9sp but manufacturer support for it is so poor that I don't think it's wise.

williaty

OOOO.... good find! That's worth importing if they'll sell into the US.

JohnDThompson 

Friction shifting shouldn't have a problem with a 16T jump. A slight overshift to move the chain, followed by trim should become second nature with a little practice.

HillRider

Good point. I've regeared several 130/74 bcd road triples from 52/42/30 and 50/39/30 to 52/42/26 and 50/39/26 and never had a problem with the 26 to 42 or 39 shift even with indexed shifters. With friction shifting it's been even less of a problem. It's not fast but it does work.

As to slack chain, Rohloff makes a chain tensioner for use on bikes with vertical dropouts. Could you adapt it to your trike?

Andrew R Stewart 

I'll add that creating a "W" cut ring teeth gate is pretty easy and can help a non pinned/ramped ring shift better. But most people are afraid of taking a file to a new ring. Andy

tomtomtom123

I have a 20T jump between double chainrings and it shifts fine with index triggers. Only problem is the chain rub when on the small chainring and trying to get on the outermost 3 cogs, but it's ok since the gear range overlaps there. The spacing between the 2 chainrings need to be a little closer though for such a high jump. I have my TA chainrings at around 7.6-7.8mm center to center. The Spa cycle chainrings I was able to get to around 8.0mm for a little more chain clearance for the chain rub.

wesmamyke

I've wanted to try a triple with something like this: https://www.ebay.com/itm/NEW-mircoSH...0AAOSwCmBdzGxA

Maybe not enough for that small a granny, but might just work with a triple+wide range cassette. It is meant to work with a double though.

HillRider

I neglected to ask earlier but where are you getting a 17T granny chainring and what's it's bolt circle? Is it a repurposed cassette cog? The smallest real chainring I've ever seen is 20T but I've seen adapters that allow the use of a rear cog as a chainring.

williaty

Yup, using a Mountain Tamer to convert from 74mm BCD to freewheel cog.