Grin Technologies is dedicated to building the best eBike parts for converting your bicycle to an Ebike. We enable our community to build their dream eBike. Find out more about Grin Technologies on our YouTube: https://www.youtube.com/@GrinTechnologies
This article goes over the most common questions our customers ask when planning their Tandem eBike conversion. If you’re looking for a full Tandem bicycle build video, check out our Santana Tandem Build Video here.
Check out this Tandem eBike Conversion story here.
What is the best electric conversion kit for a tandem?
Tandem bikes have to carry double the weight of normal bicycles and also have non-standard cranksets, with both the captain and stoker pedals linked together with left-side chain. This makes Grin’s rear All-Axle hub motor one of the best kit options for converting your tandem to an electric tandem. It is sufficiently powerful for dual riders and the torque sensing is integrated inside the rear wheel rather than in the cranks or bottom bracket.
Tandem bikes also frequently have wider rear dropout spacing (145 - 160mm), which the All-Axle hub motor is unique in supporting without any frame or motor modifications.
Can I convert my tandem to an eBike without compromising the frame, handling, or wheel strength?
Yes. Tandem bikes put more weight on both the front and rear wheels, but Grin’s expert wheelbuilding is totally up to the task. The 32 spoke All-Axle motor with Sapim butted spokes has a proven track record in both cargo and tandem applications. Furthermore, tandem bikes usually have wider dropouts, either 145mm for most brands or 160mm for Santana. This wider dropout reduces the dishing requirements on the rear wheel and better distributes the load on both left and right side spokes.
Check out this Tandem eBike Conversion story here.
Does the eBike Conversion kit fit rear spacing, tandem dropouts, thru-axles, or coupled travel frames?
Yes, we have adapters for 145mm slotted dropouts, and even Santana Tandem’s unique 160mm slotted or 167mm thru-axle frames. We also have adapters for all the normal rear wheel standards like 135mm quick release or 142/148 thru-axles.
For bikes like Comotion or Santana that decouple for travelling, the kit is conveniently connectorized (where you can easily disconnect and reconnect a wire) making it easy to decouple components on different parts of the frame.
Is a rear hub motor, front hub motor, or mid-drive better for an eBike tandem?
Either front or rear direct drive hub motors are ideal for tandem bikes.
With double the weight of a normal bicycle, tandems already put extra wear and demand on the drivetrains and the brake system. A direct drive hub motor can reduce the drivetrain stress while climbing hills, and all but eliminate brake pad wear and overheating on the long descents through regenerative braking.
We usually recommend our Rear hub motor as it simplifies the torque sensor integration, but for tandem setups using an internal gear hub on the rear then the front motor works just as well. Grin can discuss available options for PAS or Torque sensing on the bottom bracket if that is desired. Reach out to us any time!
Mid-drive motors are especially problematic on a tandem as there are now 3 loads (captain, stoker, and motor) all going through one bicycle chain exacerbating the wear and making the system more vulnerable to a single point failure.
Check out this Tandem eBike Conversion Story Here.
How much torque and power do two riders on an eBike Tandem need for hills?
Tandem bikes are very efficient on flat ground as you have the power output of two riders but the aerodynamic profile of a normal single rider bike. But this advantage is lost when climbing hills where air drag is less of a factor and the weight tends to dominate.
Higher torque hub motors are usually needed to be effective on hill climbing, ideally with at least 60 Nm of available short term torque output and 40 Nm continuous. Our All-Axle motor hits the sweet spot of this power realm perfectly. Some physically fit tandem riders are OK with smaller/lighter geared hubs, and tandem riders who are heavy or have limited leg power will occasionally require a dual motor setup for steep hills, with both the front and rear wheels electrified.
Check out this eBike Tandem Conversion Story here.
What battery size do we need for long eBike tandem rides or touring?
We find that most people touring on tandem bikes are using the motor only when needed and get quite good overall range, averaging 5-7 wh/km. That means a 500 watt-hour battery pack will provide 75-100 km of range. Those who rely extensively on the motor assist will require 15-20 wh/km, and get about 1/3rd the range.
We recommend our LiGo Battery, which is a modular battery that enables you to pack exactly the amount of power you need. We have other good battery options available on our store.
Does the eBike system support regen or engine braking for descents?
Yes, the regen braking or engine braking is a core feature of the all-axle motor kits and is especially beneficial for tandem bikes. Because of the high weight to air drag ratio, you will achieve a higher % energy recovery from regen on a tandem than on a normal bike, quite often 10-20% over the course of a trip. This not only increases the range from the battery, it all but eliminates wear of the mechanical brake pads so that they are always in top form for any emergency stopping needs.
Can the system handle the extra weight of two riders plus luggage?
We have had occasional problems with people breaking spokes, but this is the exception and not the norm. We do recommend having the spoke tension in both the front and rear wheels checked on a regular basis, and it never hurts to carry some spare spokes if you are on a long distance touring trip just in case.
Will the Tandem eBike conversion kit work with disc brakes, cassettes, and modern drivetrain standards?
Yes, the all-axle kit supports both Shimano HG cassettes and also higher-end SRAM XD cassettes, in both road and mountain flavours. But it is also a great option for more vintage tandem bikes that have threaded freewheels and rim brakes. The addition of regen braking is an enormous plus on a bike with rim brakes, as it not only makes stopping safer but it also reduces the wear of the rims themselves. And on very long descents, rim brakes have been known to heat up.
Can the system still be travel-friendly for a coupled Santana or Co-motion tandem?
Yes, because the motor is compatible with quick release dropouts and has a single point torque arm attachment, removing the wheel from the frame for packing is not much different than removing the original wheel. And very uniquely to Grin, we offer a battery solution with our LiGo 10X packs that allows you to fly with the batteries too. Both riders can carry 3 or 4 LiGo batteries in their carry on baggage which simply click together into a large pack on arrival. Otherwise travelling with an ebike battery is next to impossible.
Planning a Tandem eBike Conversion? Reach out to us!
We'd love to here more about your tandem eBike Conversion. Reach out to us here, and we'll talk with you about the best parts and set up for your tandem bike.
