After the original build last year, I decided to rebuild our 2013 Calfee Tetra tandem with a little experimental flair to it and maybe not so conventional. So, after all the parts the frame was sent to Calfee to do all the frame & paint (err... no paint) modifications.
Major change points:
- frame retrofit for Di2 shifting. Removed all traces of mechanical shift cable routings. Drilled holes in BB shells and frame to allow Di2 wire routing. Reinforced FD mounting location.
- added 1 rear water bottle mount on the bottom tube to improve ergonomics for a short (5'2") stoker that didn't like reaching forward to grab a bottle from between my spinning heels.
- cut head tube extention by 1cm. We had added a 2.5cm extension during the original build, but I didn't like the look and depending on the stem used was resting directly on the top headset.
- "nuded" the frame and fork (stripped the Cobalt Blue transparent paint job). Frame was left with a polished nude carbon finish, with 303 Aerospace UV Protectant applied by Calfee. I added a couple applications of 303 Detailer (also contains UV protectant and a little more glossy finish).
- nuding the original ENVE 2.0 tapered fork revealed a lot of ugly filler, so Calfee had ENVE replace it under warranty. The 2nd fork has a far better appearance, but still has some filler that shows up mostly under flash photo conditions. Otherwise the new fork looks nice enough.
- swapped out the Shimano Ultegra 10sp (r601/603) tandem crankset and in with a set of standard road FSA SL-K Light cranksets (triple rear, double front).
- installed 48/30 TA Specialites chainrings. Problems with big ring as noted here, so changing to Stronglight rings.
- mounted the Gates CenterTrack as same-side-drive. To achieve the required belt/chain clearance in the rear drive, that meant installing 3.5mm Origin8 chainring spacers behind the CDX rings. Of course, using spacers also requires using longer chainring bolts. Also needed to add 1.0-1.2mm worth of spacers to the granny in order to provide good clearance from the 130BCD bolts.
- modified the Di2 6770 RD with a GS (mid-long) cage from a 6700A. Parts available from Shimano (for $30), or by stripping from a 6700A GS RD ($90+). This cage has a 41T total capacity. Tested successfully with a 11-34T cassette after installing a reversed "B-screw" that had a big enoung screw head to catch the lip of the hanger stop.
- swapped out the draggy Shimano jockey wheels, installed KCNC ceramic pulleys. Used a smaller 10T top pulley (increases clearance for a 34T cog (if/when needed) and a standard sized 11T bottom pulley.
- installed a modified 11-28 cassette (11,13,14,15,16,17,19,21,24,28). The 11T and 21-28T spider is from a Ultegra 10spd cassette I had on hand. The individual 13-19T cogs are borrowed from a SRAM 12-27 cassette, each with a full set of splines to engage the freehub body (unlike the Ultegra 10spd cogs).
- built up some new wheels. Rims: 32 hole, 23mm wide x 28mm tall Kinlin 279 / BikeHubStore 472, hubs: White Ind Mi5 front / Mi6 disc rear. Front is cross-2 DT Aerolite spokes, rear is cross-3 DT Aero Comp spokes. Specific thread about these wheels here.
- installed a TRP Spyer (v2) rear disc caliper
- lastly(?) obtained a funky new set of captain's bars: 3T Zefiro + Pi Wing.
For reference, here is the original build thread and photos from last year:
- 2013 Calfee Tetra S&S
- Google+ album:
Current "rough" weights:
- Frame: 9.8lbs, fork: 365gm (13oz). Total including Di2 wiring and 3 internal junction boxes: 10.6lbs. Recall, this frame has 3lbs worth of S&S couplers, so you could net that down to 7.6lbs for a Tetra frame + fork without couplers.
- Wheels (bare): 1864gm. Front 788gm, rear 1076gm.
- FSA SL-K Light cranksets, w/BBs, TA chainrings, CDX rings and chainring spacers: front 700gm, rear 864gm.
- Captain's 3T Zefiro LTD bars (42cm) w/Pi Wing: 460gms.
Total weight as shown below: 30.3lbs.
Here are a few snapshots of the initial rebuild (see full Google+ album here):
Other minor adjustments and interests to note:
- rotated the Bushnell/DaVinci eccentric "wings" 180 degrees to put the adjustment/tightening bolt on the non-drive/left side.
- Di2 wiring is using 3 internal junction boxes. 1 at front S&S coupler, 1 at rear coupler, and 1 in the bottom of the rear seat tube. Access to the rear seat tube box is best done via the hole drilled in the BB shell. When installing this box, rotate the box (endo) to prevent any potential cable disconnects. For the junction boxes at the S&S couplers, I wrapped these with closed cell foam to prevent rattling and provide some impact protection to the connections.
- Di2 battery is the Shimano BTR2, installed in the stoker's seatpost. Charging is via a USB port in the front junction box (mounted under the capt stem). I'm using a BTR2 seattube battery holder made by Specialized. Ritchey also makes a simplier design. In either case, no epoxy or duct tape required.
First ride impression:
Well, it's 11F and a blizzard today (Sunday). Yesterday after getting the steerer tube cut at my LBS, I took a few spins around the parking lot, dodging sheets of ice until my bare hands were completely numb. The Di2 shifting was so smooth and quiet (maybe it was the 15-20mph wind @ 15F) that I had to look back to see what was going on. Not exactly a true ride report - yet. Time to head out skiing (I feel a Monday cough coming on .
- Fabricate(?) a 45 degree bracket for the new water bottle mount. Idea is to create a similar bottle cage angle as with a normal downtube mount. This will 1) ease stoker access, 2) reduce any dripping from bottle, 3) prevent ejection of bottle.
- Think about replacing the Pi Wing with standard TT extensions, then add Di2 bar end shifters into the mix.