chichi

Does anybody have any advice on converting an FAS SLK 9 speed triple to a compact double?
I am hoping to convert to SRAM wireless 2x11 and I had no idea of the difficulty of finding 130mm and 74 BCD chainrings that might make this possible.
The crankset set we have has 172.5 stoker arms which I would like to keep and they also seem difficult to find on new cranksets.

Alcanbrad

You might find them at precision tandem

bwebel

TA does some nice chainrings in a range of tooth sizes. Would be fairly easy to get a 48t 130 ring and a 32t 74 ring. If you wanted bigger than 48t, then you'd either need to go outside of the 16t spec on the front derailleur or find 74 rings bigger than 32t. Such rings definitely have existed in the past, but I don't know of a current source.

chichi

I have been trying to find a 52 or 50/38 that would both attach to the 130 bolt circle.

I think I might have better luck finding those rings than my original idea of mounting a 32 or 34 on the 74 bolt circle and a 48 on the 130.

Msteven 

House of Tandems in Texas sells 74bcd 34t chainrings
I have 48x34 on the 130/74 middle/inner chainring positions (using the HoT 34t) and 10-42 11 speed cassette, and I operate my Di2 in sequential mode (does not like big-big combo)
Lots of gear range here and I think I could drop to a 30t inner and be ok if I needed to.

For eTap 11 speed, if you run a more traditional 50x34 you will probably need to install a 11x34 cassette in order to stay within the eTap system parameters.
You might be able to push out to a 11x36 cassette. However, even with a roadlink, the 11 speed eTap system does not like bigger cogs such as 11x40.
You will have to purchase an 11 speed 50t chainring as well as a set of chainring spacers in order to get the 2 chainrings closer if you need to for the 11 speed chain to work and not drop in-between the rings..

Alcanbrad

I had a significant amount of problems when I went from 3X FSA gossimar with Ultegra 10S derailleur to 2x compact on same crank with 11S etap red i obtained from House of Tandems. The issue was eventually discovered to be the chain skipping on the 34T chainring that HoT included in the kit. This chainring was custom made for HoT by Vuelta. We only had the issue when pedaling under heavy load primarily when climbing. I resolved it with a different brand 34T I obtained from Precision Tandems (I think it is from TA). Ric at HoT does a great job and I am happy with the conversion, I think in my case, the quality of the Vuelta rings was poor and not up to the operating conditions we were subjecting it too. Your mileage may vary.

I run 34/50 with an 11/42 in the rear. If you are considering SRAM etap, Check out the Large capacity replacement cage for SRAM etap from Chinook Cycles. It has worked flawlessly for us across the full gear range without having to worry about having to avoid gears due to capacity limitations of the stock derailleurs. It does require a roadlink, but it's a drop-in solution.

Let us know what you do and what your experiences with the transformation are.

chichi

Msteven and Alcanbrad,

Thanks for the feedback. I have a 34T on order from HoT and a replacement cage from Chinook cycles on order. I plan to use a roadlink also.
Sounds like I should get a back up 34T on order from Precision just in case.

Did you use the same front derailer mount you were using previously with the new SRAM red? I currently am using a Campy racing T on an FSA mount.

I will let you know how it works out.

mikemelbrooks

I am working on the same kind of thing and have bought a second hand SLK crankset 110bcd I hope to just change just the right-hand crank so I can fit 50 34 rings.

Alcanbrad

We have 2014 Co-Mo Carrera and going from Ultegra 10S triple we did need a new front derailleur mount. I recall when I ordered the upgrade kit from HoT Ric said it was needed. I took a look today and the one we have on the bike now looks like the mounting point is farther from the center-line of the seat tube than the one I took off. I don't know the specifics, others on the forum make be able to clarify, or I am sure Ric at HoT, or ever, Mel at Tandems East could help.

Chilepines

A different approach that I think might work is to switch the current stoker triple to an FSA Adventure series modular crank. If your current triple is Mega EXO it should work. Then you can get their direct mount chainrings which replace the modular spider.
I started from the current FSA SL-K tandem crank which came with the modular spider and put on 46/30 rings and a 10T small cog on the rear.

chichi

I have completed my conversion of 3x9..12/36 to 2x12 11..50. I am very happy with the results.

This is a list of the changes
SRAM AXS Red road front and rear derailleurs
Cycles Chinook AXS Extended derailleur cage
Wolf Tooth Road link
10mm longer B screw with head ground down to clear derailleur body
FSA tandem FD mount with " point " filed down about 1/8"
Mount for inner ring milled down .125 mils
House of Tandems 34 tooth inner ring
FSA 50 tooth mounted at middle ring position
1/4"id x 5/16od x5/8" (filed to fit) sleeve bearing ,placed over chain ring stud at crank arm
1.2 mm spacers on outside of chainring bolts, chainring bolts mounted with allen drive facing in
SRAM PG-1230, 11- to 50-tooth Eagle cassette.
KMC DLC 12 chain

A side benefit which I was not expecting was improved braking. I am using Paul Klampers, front caliper has a short pull arm, the rear has a campagolo arm, they are spaced for Hope ventilated discs. The braking is much improved with the SRAM levers vs the Campy levers.

dmegarmstrong

I recently converted my 2010 Co-motion speedster to a single ring 12 speed option.

11-50 SRAM NX eagle cassette - compatible with my existing freehub; X01 eagle derailleur and chain; Microshift 12 speed SRAM bar end shifter. Timing chainrings are 36 tooth and drive chainring is 48 presently but would be swapped out for something smaller for touring purposes.

This setup allows use of standard double road cranks - same sided timing chain and drive chain is perfect.

Love the smooth shifting and absence of dropped chain concerns. It is also really nice to be able to use standard road cranks with their narrow pedal stance. We have lost a little on the top end but my stoker figures is happy to coast at anything over 30 mph