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Old 09-26-16, 04:32 PM
  #82  
twocicle
Clipless in Coeur d'Alene
 
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Join Date: Mar 2012
Location: Coeur d'Alene, Idaho
Posts: 1,945

Bikes: Tandems: Calfee Dragonfly S&S, Ventana ECDM mtb; Singles: Specialized Tarmac SL4 S-Works, Specialized Stumpjumper Pro, etal.

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XTR Di2 w/triple "trekking" rings 48/36/26 & chain guard

Unique setup features:

1) modified Shimano Direct Mount and Problem Solvers Direct Mount Adapter to pull the FD inboard by ~3mm.

2) timing side Specialized S-Works 130BCD carbon spiders. These spiders were needed to center the spider offset for the somewhat fat Gates timing rings/belt. Spiders are mounted in reverse (inside-out) to get the perfect offset. Rotation direction matches normal driveside, so loads are per directional spec design for the spiders. Lightning provided 2 x 130/74bcd spiders, but the offsets just didn't work out on those because the timing ring was either too close to the crank arms or too far inboard and causing the belt to rub the lower stoker waterbottle cage (frame clearance was not a problem).

Unfortunately the special S-Works chainring bolts are a bit too short to work with the Race Face Crank Arm Tab Spacers I like to use on the back side of the timing spider tabs. Switched back to using just 2mm chainring spacers/washers.

Items #1 & 2 above are due to special narrow Q-factor crankset needs. Probably non-factors for regular-wide tandem cranksets.

3) 48/36/26 chainrings and chainguard taken from a Shimano Deore XT FC-T781 Crankset. 104/64BCD 4-arm Lightning spider for the driveside. I had some reservations about using the optional chainguard, but stoker and some friends seem to think it looks great so leaving it on and swallowing the few extra grams. It does have some functional purposes such as stoker safety and keeping the chain on in case of over-shift. When messing with FD adjustment, it's definitely a lot easier to see things without the chainguard (installs with 4 simple screws on the backside of the big ring).

4) bike is still sans-aero bars, but ready to mount them (incl Di2 TT shifters). This is why I have the XTR display is on the "wrong" (left) side, as my 3T clipon mounts slip right behind the display and I can still see the display while using the arm rests.
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Last edited by twocicle; 02-24-17 at 04:43 PM.
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