Turbotandem

• 35 pounds,
  • approx $10,000 budget
    • Increased tire width from our current gravel racing from for packing tandem for 29x2.3 and for sand/rocky riding we do in AZ also fit 27.5x3.0
      • Reconfigure how frame bags and bottles fit
        • Non-suspension, non mountain bike geometry. IE: 50mm Bottom Bracket drop, straight not bent top tube, 427AC non suspension fork.
          • Something bomb proof and drive train that works for long stretches in the back country..

I started by looking at stock tandems but none suited the criteria we set. I believe Co-Mo is coming out with a gravel specific tandem for their anniversary that might be close to these criteria. We went with a "direct to buyer" outfit Granite Tandem Designs [now Cycles Chinook] where David Lafferty did a great job engineering, applying novel and thoughtful design ideas, and helping with the most tricky parts of the spec and build. I prefer direct to buyer relationship because I've had so many tandems and have a good idea of what I want it's nice to work with someone able to address those needs. The spec sheet in the google doc link below includes all the build and component data, along with my basis of decision making for nearly all components. Feel free to comment on any of those ideas.

Here’s the link to the build spec: https://docs.google.com/spreadsheets...iOF-KBFQjHgPP0
The highlights in my mind, or special custom applications are:

• Tight Q-factor road cranks. 156mm Q-Factor while still clearing large tires. Worked wonders on knee comfort
• Eagle 12 with right side timing chain, tight timing chain line: Increase reliability, no need to recharge electric shifting for long stretches in back country, right side drive has better efficiency tranfering captains power than left side timing
• BB 386 EVO 86.5mm bottom bracket shell gives good base for chain stays.
• Granite tandem custom proprietary eccentric
• 65mm offset ti fork from Blacksheep works well on washboard
• custom Dean Bikes 240mm stoker stem
• JPak custom bolt on bags
• I’ll refine the numbers, but in round figures 35# ready to ride bare bike, 45# with all the empty bags, bottles, and electronic navigation and lighting, 55# loaded with gear, rain gear, safety shelter, tools, first aid, etc. add 10 pounds for food and a big water day (we usually harvest water along the way and try not to over carry) comes to 65# fully laden.

With lavender bushes showing 27.5x3.0 setup



with aspen trees how we ride back country in Colorado with 29x2.3 tires

• Inspiration image for the bag design:
• 
  
  
  
  
  
  
  

colotandem

Such a well thought out build! You guys have outdone yourself Andy!

I just realized that you had to use a Eagle shifter on the top of your handlebars. Did you encounter many times when you were in the drops or on the hoods (braking) when you needed to shift? Hopefully not many.

It certainly gives me some ideas for future builds. But I am not sure that we would use a bike like this the way that you two do!!

Either way - you and Kami are inspiring! You need to share with the group your route, miles & vertical that you recently rode to break in El Burro.

Turbotandem

I played with the shifter location for a month before settling (and before finishing the leather wraps that essentially lock in the set up). I could not find a good location that could be controlled from the hoods. But I can actually reach the shifter from the drops with my thumb. That's nice because after long mulit-days sometimes my hamstrings do better stretched riding in the drops. We had a beater gravel bike for many years with the shifter on the tops like this so I got pretty used to a quick reach for them. I could see if we did more technical riding where that 1 second shift with one hand off the bar might be hard to control, but it would be climbing not braking that I'd imagine the most urgent need for a shift. Our riding while lengthy, it's generally pretty tame with maybe 15% of our miles on something really rough and narrow.

A short summary of El Burro's first big trip, which was a good proof of concept. We'd ridden her for a month before the trip including some really rough stuff in sante fe area. The main trip we just finished was 13 days of riding from Moab to Boulder 85% off-pavement, 715 miles, 54,100 feet of climbing, 80 hours in motion and some 96.5 hours on the road including lunch breaks. Two broken spokes, both in the front, both right at the end spoke end of the nipple: I think the spokes weren't threaded/cut well. One de-laminated tire. One crash on a back-country plank bridge with the planks running parallel to the direction of travel with gaps and uneven placement between them. Below is a map of the ride and profile and one picture. I don't know how long our spotwalla track will persist, but this link is shows our route and re-route to Boulder and you can zoom it to see more detail (this one does not show our track just the route): https://spotwalla.com/tripViewer.php...85b10bc7f61362

our route this year in pink

Turbotandem

I added frame development pictures to first post, and here are some detail shots:


bags over chain, tool bottles in chain line


65mm offset fork by Blacksheep


ergon post stack height (the little blue collar is rubber decoration)


alternate narrower spider with 26t chainring clearance at 3.0x27.5 tire 2.5mm


alternate narrower spider with 26t chainring clearance at 2.3x29 tire


bar set up


shifter set up


side but side stoker bottles


Custom art for sewn patch, HA!

colotandem

I can't help but smile when I see your new bike set up and read of your adventures!!!!

EthanBixby

Fabulous build and great adventures! We have a more road and travel oriented Granite Tandem, and love it. David is a pleasure to work with, and we are extremely happy with our bike. It's funny Andy, our other bike is a Paketa V2R, which is a special bike too!
Ethan

kevrider

was there any magic needed to make the road cranks play nice with the plus wheel and tire? boost cranks are the main reason i am reluctant to ride anything with plus tires.

GraniteTandem

Turbotandem

David provided the best outline; we leaned on him to hit the criteria we set. As you say, boost cranks are a hurdle we did not want to accept. In fact, we wanted a narrower Q-factor than we have on our other "normal" gravel tandem. David at Granite was able to configure the bike at 156mm stoker Q-factor in back, and a little less for the captain. I think we have about the tightest clearances from cranks to stays, chain to tire tread, and mud clearance for both the 29x2.3 and 27.5x3.0 as is reasonable and reliable.