dstke

Loving our new tandem! A custom build by Cycles Chinook.

Build features:

Titanium frame and fork
SRAM Red etap shifters and derailleurs
SRAM Hydro HC disc brakes and 203mm rotors
SRAM Force cranks
Veer custom length timing belt
Two wheelsets
- Road: 700c Velocity Blunt 35 rims, White Industry XMR hubs
- Gravel 650b Spank Oozy Trail rims, White Industry XMR hubs









Shifting is flawless there is absolutely no adjustment necessary when switching wheelsets. Braking is solid. The Veer timing belt occasionally grumbles catching on the teeth but happens only sporadically. It could be due to heat or dust, I'll keep monitoring it.

Thanks David Lafferty aka Oneisallyouneed

geoffs

Looks very nice. We're interested in something similar but with the Australian dollar so low it might be a while before we get ours.

Alcanbrad

Very nice, I am about ready to revamp the drive train on our Co-Mo as I am not happy with shifting performance and I would like to go to hydraulic brakes. Can you share more detail on the drive train? Crank model, gearing, and anything unique about the mix of elements you choose, etc. Thanks!

dstke

Sure. We had a Co-Motion Speedster for 10+ years and also experienced trouble shifting. With the rear derailleur it was mostly just making frequent adujstments with the cable barrel but the front derailleur was more problematic. I replaced the middle chain ring after a couple of years. The SRAM 42 tooth chainring wasn't available so I replaced it with a 39. After this shifting was never quite as good. I tried adjusting the height and angle of the derailleur and even changed from Dura Ace to an Ultegra shifter but it rarely would shift smoothly or effortlessly between small, middle, and big chain rings. Eventually I resigned myself to riding mostly in the small and middle chainrings. On a tour last year, getting caught up in the moment, I enthusiastically shifted into the big ring only to find the release lever completely shot when trying to shift down. The rest of the tour I had to manually adjust the shifting by adjusting the cable. So I hear you when you talk about shifting performance.


On this new tandem as I stated above the shifting has been smooth and effortless and I'm especially impressed that no adjustment is necessary when changing wheelsets. We went with a compact double crankset in front, SRAM Force BB30 50/34 and 'tanemized' rear cranks in the back. You might inquire with Cycles Chinook about how he 'tandemizes' the rear cranks, basically enabling the timing crankarm to be mounted on the non-drive side. Also the SRAM force cranksets have a 107 BCD direct mount arm so we could go with even smaller chain rings, e.g., 33/48. The wide range of cogs on the rear cassette, 11-42, is enabled by a Wolf Tooth Roadlink and extended derailleur cage.


What's probably unique about the set-up is the Veer timing belt. The Veer is a split belt that is riveted together to allow custom lengths. We haven't had any problems with the strength of the belt but it has occasionally made bumping and 'grrr' sounds. I've re-tensioned the belt several times and may need to adjust the spacing to improve the alignment but so far it occurs only sporadically so I haven't nailed down the exact nature of the problem.


Hope that helps,

Doug

Alcanbrad

Thanks for the info, I'll dig deeper, the gearing range you have looks to be more to our liking. I hear you on the front shifting. Our Carrera has Ultegra triple and I have never found the sweet spot of adjustment, it either won't climb into the big or drop into the small. I can adjust for either, but not both. Also, the capacity of the derailer is too small for the range we have so the chain keeps dropping off the lower jockey wheel if we drop into the small chainring with the chain on the low smaller end of the cogs. Just overall frustrating, that drivetrain was never designed for that set up.

As to your belt grrr'ing, maybe a hint:. Our other tandem is a Co-Mo Primera and I upgraded from a timing chain to a Gates timing belt. In order for the gates chain ring to clear the rear chainstay I had to place washers between the chainring and spider to move the chainring out and away from the chainstay. Whenever we pedalled with some force, we would get a "grrr'ing" sound during the power stroke and we could feel it a little in the pedals. After all sorts of futzing with belt tension, nothing seemed to fix it. On a last ditch whim I added similar washers between the front chainring and spider to move that chainring out by the same amount. Wo-la! no "grrr'ing". The in-line alignment of the timing chainrings may be your issue.

Good luck!

Alcanbrad

I have been investigating this solution and it is looking attractive. I have a few more questions:

With respect to the extended derailleur cage. Is this the SRAM mid length cage or is this an aftermarket option? (It looks like it might be different, I can't see too clearly in the pictures) If aftermarket, can can you share details? The capacity of the SRAM Red with mid range cage is only 36 teeth which renders the smaller 4-6 cogs unusable when in the small chainring. Do you have this condition/issue?

Have you found the smaller number of available gears to be an issue? I know there is a tremendous amount of overlap, but with a large selection of a triple, you are never far from a gear that is a little higher or lower and when the stoker constantly asks for a change, it usually is not too large. Has this setup appreciable changed your shifting habits?

Thanks again.

OneIsAllYouNeed

Howdy Doug. Beautiful bike. Looking forward to seeing more pictures of it out adventuring.

The Veer belt is similar design to the original Gates Carbon Drive from the early 2000s. The beltrings have guides on the sides, but there aren't any other centering features. With the beltline perfectly straight, the belt drifts from one side guide to the next. The rivets holding the split belt together run into those side guides. I think the rivet heads will eventually wear groove into the guides and the "grumbles" will lessen.

OneIsAllYouNeed

The crankarms on Doug's bike are Sram Force 22 BB30. They're compatible with many aftermarket 3-bolt spiders, including 76, 94, 104, 110, and 130bcd options. Sram's new 107bcd rings are meant for AXS 12-speed drivetrains with 8-bolt spiders. Aftermarket options for 107bcd rings or 8-bolt spiders are extremely limited at the moment.

The stoker cranks are made up of two right side crankarms and a replacement spindle of appropriate length. The front crankarms and rear left crankarm are all helicoiled to change the thread direction.

The derailleur cage is aftermarket*. It's made exclusively for Cycles Chinook by Digirit, as a longer version of Digirit's oversized pulley system. More details are here:
https://www.cycleschinook.com/produc...-cage-upgrade/
*Most folks with this extended cage get it with their new tandems. Is it still aftermarket if it's installed by the builder?

Alcanbrad

Thank you OneIsAllYouNeed, This helps tremendously.

dstke

So savvy. I've another friend who was wondering how you did that!

Alcanbrad

I took the plunge, ordered, and installed the ETAP Red system on the Co-Mo. Also ditched the TRP Spyres in favor of the Red Hydraulic brakes. One ride so far and we love it. I ordered the large capacity cage from Chinook, however, it is on back order for now and using the gearing display on the Garmin allows me to insure we don't go into the "slack" gears.

Thanks for the info, it was a bit pricey, but we'll enjoy every bit of it.

Carbonfiberboy 

For information only: The 42 middle ring and original big ring are shaped to be a matched pair. To sub in a 39t triple middle ring, one has to replace the outer ring with ring a intended for a 39T-53T double. Then it shifts fine. I replace my middle ring probably every year, the big ring maybe every other year. The teeth are OK, but the pins and ramps wear, probably because of dear Stoker. Of course 39T middle rings are only available in 10 speed if any are left at all. so if one is doing this to a 9-speed bike, the FD and left brifter have to be replaced by 10-speed. The issue is that the width of the rings is different. I have a SS granny which never needs replacement. We have a 2003 Speedster and love it. As we've aged, our gearing creeps lower. Now our low gear is 26-40, wolf tooth on the RD.

OT, but someone might be able to use this information.

dstke

I like knowing what gear I'm in. Enjoy the effortless shifting.