BMC motors FAQ

What BMC motor should I get, V1, V2 speed, V2 torque, or V3?

V1 400 Watt motor is rated for speeds up to 20-22mph. Maximum recommended input power is 36V 20A or 48V 15A.
V2 600 Watt speed motor is the most popular. At maximum recommended input of 48V 25A and 26" wheel motor reaches speed of 30mph/48kmh.
V2 600 Watt torque motor is recommended for conditions where extra torque is needed at lower speeds, like on cargo bikes for hauling heavy loads, or riding up steep hills. At maximum recommended input of 48V 25A and 26" wheel motor reaches speed of 26mph/40kmh.
V3 1000 Watt motor is optimized for higher speeds up to 35mph/60kmh, such speeds are neither street legal nor safe. Common reason for using this motor is desire to keep up with the traffic in rare situations like crossing a narrow bridge without a bike lane. It is recommended to use BMC 50A controller with this motor.

If V2S, V2T, and V3 motors were tested with the same controller (input power), V2T would consume most energy and have highest torque at lower speeds going up the hill, and on flat surface V2T would consume least energy and would have lowest top speed. V3 is the opposite, V2S is somewhere in the middle but closer to V3. Since V3 is usually used with more input power, on average it consumes more energy and produces more power than V2 motors.

How do geared BMC motors models differ in ouside dimensions?

All geared BMC hub motors have identical outside dimensions, except different axle lengths between front and rear models.

What are the advantages of a rear vs. front motor?

Rear motor advantages:

• Torque arm is not necessary for rear motors with steel frames (recommended for aluminum rames) but it is required for front motors.
• Rear motor looks better cosmetically, it doesn't stand out as much as front motor, and it is easier to hide motor wires behind a frame beams.
• Front motor interfers with steering at lower speeds. Even considering better front to rear weight distribution with front motor, overall, quality of a ride is usually better with a rear drive.
• Front wheel drive tire may not have enough traction on wet or loose surfaces going up steeper hills.

Front motor advantages:

• Rear motor can take up to 7 speed freewheel, so bikes with 8 and 9 speed systems will require either downgrade to 7 speeds, or a slight dropout stretching to accommodate 8 or 9 speed freewheel.
• Front motor is a solution for bikes with internal gear hubssystems.
• Better weight distribution since weight on ebikes tends to accumulate towards the rear end.

What are recommended rim brands and styles?

There are many rim styles and brands available. Generally double wall rims are strong, and V profile rims are stronger than rectangular profile.

Rectangular(ish) profile	V profile

We use Velocity Cliffhanger rims to build 26" and 700C wheels, these rim has strong V profile and thick side walls for maximum strengh.

What is the recommended spoke pattern for BMC hub?

Theoretically, higher cross patterns position spokes less perpendicular to the hub flange and to the rim, this helps to withstand the twisting forces of acceleration and braking forces in the case of hub brakes. In practice however, due to larger motor diameter, higher cross count often results in unsafe spoke to rim angle causing spokes breaking close to a nipple. We recommend cross 1 or 2 for 700c rims, and cross 1 for 26 inch and smaller rims.

What are the spoke lengths needed to lace motor in to a rim ?

Spoke lengths depend on ERD (effective rim diameter). ERD may significantly differ between rims with identical outside diameter. Rectangular profile rims have greater ERD than V profile rims, therefore require longer spokes. Rear BMC motor requires a slight dishing to the righ side. Spokes on freewheel side need to be 1-2mm shorter than on a disk break/left side. Dishing may be achieved by using shorter spokes on the right side, but it is easier to use same lengths spokes and tighten spoke nipples on freewheel side 3-4 turns more than on the disk break side. This page lists examples of rims, their ERDs, and spoke lengths.

My bicycle has 8 or more speeds but maximum recommended for BMC motor is 7 speeds. What should I do?

8 & 9 speed freewheels are available but require a spacer washer between axle and dropout, to make it work, place motor's torque washer (comes with motor) between freewheel and dropout instead of placing between dropout and axle nut - that will result in ~3mm frame stretching which is not recommended for high end full suspention frames. [PICTURE HERE]
Alternative option is to replace gear shifter wtih 7 speed shifter and use 7 speed freewheel.

Will freewheel on my bicycle work with motor?

There are two standards of cogsets, freewheel and cassette [PICTURE HERE]. BMC motors only support freewheel. If your bicycle has 7 or less speed freewheel it will work, .

Is BMC motor capable of regenration?

No. Internal freewheel detaches motor from the wheel when motor is unpowered. Even regenration sounds attractive, it is arguably insignificant for smaller size motors. Being able to pedal without motor's resistance would actually conserve more rider's engry than regeneration, when for example battery charge is exhausted.

Can I use BMC motor off-road?

The motor can be used for light off-roading such us gravel roads but jumping and riding over obstacles may prematurely wear out motor gears.

Is torque arm necessary?

Torque arm is absolutely necessary for a front motor. We strongly recommend using two torque arms, one on each side, on aluminum forks. We advise to use torque arm for rear motors on aluminm frames, although it is usually necessary only if aluminum dropouts are not deep or thick enough. The danger of not using torque arm is that if motor axle nuts are left loose after installation, it may lead to axle spinout and aluminum droputs breaking off.

Is Cycle Analyst required?

Maximum Amps (current flow) limit on controllers included with BMC V2 and V3 kits is ususally set higher than remmended for a motor. Direct plugin Cycle Analyst allows adjusting Amps limit on the fly through its user friendly menu. This is especially usefull when riding conditions change. For example, riding on the flat at cool weather can be done safely at significantly higher Amps compared to riding up the steep hill on a hot summer day. Using throttle to control Amps is not always safe. For example, half throttle does not necessarily mean that controller is sending only half Amps it is limited to. Adjustable Amps limit is the main reason we recommend Cycle Analyst and of course it has many other useful features like energy use monitor, speedometer, odometer, and more.

I'd like to be able quickly install and remove electric kit to easily switch between regular and electric bike, is that feasible?

Although we don't favor such option, it is possible to configure a kit to be relatively easily removable. For instance, Topeak bags are designed to slide off a rack. If a battery is inside a bag, and controller is mounted on top like on some examples here, removing/installing such bag would require re-connecting throttle cable, motor phase and hall sensors cables, and possibly ebrake or kill switch cable each time.

What type of grease should is used for motor internals?

BMC uses Mobilgrease 28
Manufacturer's description:
Mobilgrease 28 is a supreme performance, wide-temperature, antiwear grease designed to combine the unique features of a polyalphaolefin (PAO) synthetic base fluid with an organo-clay (non-soap) thickener. Its consistency is between an NLGI No. 1 and No. 2 grease. It offers outstanding performance over a wide temperature range. The wax-free nature of the synthetic base fluid, together with its low coefficient of traction compared with mineral oils, provide excellent low temperature pumpability, very low starting and running torque, and can reduce operating temperatures in the load zone of rolling element bearings.
The clay thickener gives Mobilgrease 28 a high dropping point value of around 300?C, which provides excellent stability at high temperatures. Mobilgrease 28 resists water washing, provides superior load-carrying ability, reduces frictional drag, and prevents excessive wear. Tests show that Mobilgrease 28 lubricates effectively rolling element bearings under conditions of high speeds and temperatures. Mobilgrease 28 has also shown superior ability to lubricate heavily loaded sliding mechanisms, such as wing flap screw jacks.

What is the rate of gear reduction in BMC motors?

All bmc motors have 27:135 or 1:5 gear reduction.

What is maximum power recommended for BMC motors?

in progress...

What are common weeknesses of BMC motors?

in progress...

Is the motor reliable in hot weather?

in progress...

What are the advantages of BMC motors compared to direct drive motors like Crystalyte or Aotema?

in progress...

How does battery voltage, amperage, and wheel diameter affect speed and torque.

in progeress... Generally, motor laced in smaller diameter rim would have higher torque and lower top speed. For example. V2 speed motor in 20 inch rim would have similar torque and top speed as V2 torque motor in 26" rim Here are approximate rim size to max speed ratios:

	Rim diameter	700c rim	26" rim	24" rim	20" rim
36V 25A	V3 ?mph/?kmh V3 ?mph/?kmh V3 ?mph/?kmh V3 ?mph/?kmh	V3 ?mph/?kmh V3 ?mph/?kmh V3 ?mph/?kmh V3 ?mph/?kmh	V3 ?mph/?kmh V3 ?mph/?kmh V3 ?mph/?kmh V3 ?mph/?kmh	V3 ?mph/?kmh V3 ?mph/?kmh V3 ?mph/?kmh V3 ?mph/?kmh
48V 20A	V3 ?mph/?kmh V2S ?mph/?kmh V2T ?mph/?kmh V1S ?mph/?kmh	V3 ?mph/?kmh V2S ?mph/?kmh V2T ?mph/?kmh V1S ?mph/?kmh	V3 ?mph/?kmh V2S ?mph/?kmh V2T ?mph/?kmh V1S ?mph/?kmh	V3 ?mph/?kmh V2S ?mph/?kmh V2T ?mph/?kmh V1S ?mph/?kmh
48V 30A	V3 ?mph/?kmh V3 ?mph/?kmh V3 ?mph/?kmh V3 ?mph/?kmh	V3 ?mph/?kmh V3 ?mph/?kmh V3 ?mph/?kmh V3 ?mph/?kmh	V3 ?mph/?kmh V3 ?mph/?kmh V3 ?mph/?kmh V3 ?mph/?kmh	V3 ?mph/?kmh V3 ?mph/?kmh V3 ?mph/?kmh V3 ?mph/?kmh