TANDEM Diversity
Tandem Drivetrains
Considerations and Options
When contemplating purchase of a new tandem, a team will encounter several drivetrain options to consider. They will likely carefully research these options and will encounter a good amount of information, some unbiased and based on experience, and some more biased and perhaps based on prejudices and hearsay. It can be difficult to sort through all the information available. What follows is a distillation of some of the more important aspects if each drivetrain choice, with pros and cons to consider and with quirks and oddities to be prepared for.
The bottom line is that, these days tandem drivetrain offerings from the major manufacturers are of good quality, with most giving reliable performance and good service life, no matter the underlying technology. In other words, it's hard to go wrong when choosing the drivetrain to equip your new tandem.
As always, feel free to get in touch with us by email with any questions or comments you might have.
Common Tandem Drivetrains
**Chain/derailleur, with either timing chain or belt
**Enclosed gears/hub, typically fully belted
Chain/derailleur
Pros:
Less expensive
Easy to replace parts, and parts are readily available
Use any wheel set you want, within limits of frame design
Slightly more efficient, when clean, properly maintained, and properly adjusted
Cons:
Delicate (relatively)
More maintenance required
May require more adjusting, especially during travel
May require expertise to adjust
Enclosed Hubs
Pros:
Quiet, cleaner, especially with belts
Durable
Low maintenance
Rarely need adjusting - set and forget
Easy to use
Uniform steps between gears
Can shift while stopped
Can shift through multiple gears at once
Cons:
Weight and cost
Parts may not be readily available, though not often needed
May require expertise to service
Limitations on wheels that can be used (this applies to the Rohloff)
Choose the right drivetrain for your needs/desires
Need/Desire/Concern Best Drivetrain Choice
Go fast Chain/derailleur
Travel Hub is better, chain/derailleur ok too
Weight and cost Chain/derailleur
Dependability/Ease of use Hub is great
Getting the most out of what you have, especially gearing options
Rohloff hub:
Rear cogs are offered in 19, 20, 22T
Front rings are available in a variety of sizes but on tandem are most often 50 or 55t
Cannot go lower that 2.5 primary gear ratio on tandem (front ring t divided by rear cog T)
Smaller wheel diameter (650b) may have advantages in addition to lower gears (can use bigger tires)
Chain/derailleur:
Change chain ring size to get higher or lower gearing (may impact shifting quality)
Can also swap between regular, compact, and sub-compact chain ring sets (53/39, 50/34, 46/32)
Change cog sizes in the rear cassette, especially to get lower climbing gear
This may impact shifting quality
May need longer b-limit screw or possibly Road Link to make this work
Note: Triple cranks are becoming harder to find and are now more often available only in lower quality groupsets
This is due to a number of factors:
Industry influence and trends
Weight and complexity
Rear cassettes in 11 and 12 speed
Fully belted drivetrains (Rohloff and Pinion)
These are durable, reliable, easy to set up, easy to use, and easy to maintain
They are heavier and more expensive than chain/derailleur
Rohloff adds roughly $2000 to $2500 to the price of a tandem, depending on the model
Pinion adds roughly $5000 to $6000 to the price of a tandem, depending on the model
Rohloff adds about 2 pounds to tandem weight
Pinion adds more weight, but the weight is low on the bike and not rotating weight
Rohloff requires a properly built wheel, with the hub built in
Pinion allows use of whatever wheel set you want
Rohloff uses quick release only; there is a thru axle adapter, not a true thru axle version
Pinion can use thru axle
Rohloff has 526% gear range, in equal steps
Pinion has 636% gear range, in equal steps
Rohloff uses 2 belts (timing and drive)
Pinion uses 3 belts (timing, drive, and connector). Two of these are identical
Belts are expensive but last a long time; much longer service life than chains
Belt tension: Don't over tighten. Don't really need a device or app to measure belt tension; just make sure the belt is
tight enough to not skip. Any tighter might wear bearings prematurely. Note: the whole world of belt tension
changed many years ago with the advent of the center track belts that require less tension
Belt care: Keep clean with water or mild soap and water; rinse and air-dry. May spray with silicone spray if desired;
this tends to help the belt stay clean and quiet
Oil seepage: The Rohloff hub is not a closed, air-tight system, so some oil may seep out of seals or axle,
especially at altitude and/or if the hub is over-filled at oil change. Note: Guidelines for quantity of oil to be used
in the hub have changed (see a brief summary)
The "All-Road" movement:
Tandem manufacturers are offering more models in the "Adventure", "Gravel", and "All-Road" categories. This essentially means frame design that allows for use of wider tires, that is lower pressure, higher volume tires. From research mostly coming out of Seattle we know that lower pressure, higher volume tires have lower rolling resistance and accommodate a greater range of riding surfaces and conditions, when compared to traditional high pressure, low volume tires. So, this move by the industry is a good thing, offering tandems that better meet the needs of an aging clientele wanting more diversity in their tandem life.
Drivetrain and wheel/tire pairing:
The pairing of the drivetrain with wheel and tire selection (and frame design too) can help each couple dial in the perfomance characteristics they want in their tandem. Actually, it is becoming fairly common for teams to keep two sets of wheels: one for go-fast, recreational riding and another for touring/adventure riding.
Electronic shifting for tandems:
At present, offerings are pretty much limited to Di2 from Shimano and Etap from SRAM. An e-shifter for the Rohloff hub is available, but only when used together with the Bosch e-assist motor, as the shifter shares the motor's battery.
Di2 and AXS (Etap) both have phone apps for controlling and updating firmware. The Di2 system requires a D-fly device of Bluetooth capable display, while the AXS is already bluetooth capable.
Di2 can be set up in normal, synchro, or semi-synchro modes