CHAIN RINGS CLEARANCE
If John had wanted only single chain ring clearance for his single speed
Tandem, this would have been much easier. Instead, he plans on riding
with two chain rings and two cogs for easier gearing changes. He
provided us with his chain-line numbers and the largest possible chain rings.
Once we had laid it out in AutoCAD, we realized that traditional dimpling
would not cut it. The other compounding issue was the requirement of 2.1"
29-R tire clearance. The larger tires forced us to bend the chain stays out
into the chain ring path.