Front hub motor for a SP roll elite with disc brakes

Doug Johnson

New Member
Region
USA
Can I install a Front hub motor for a SP roll elite bike with disc brakes? Does anyone know if the rotor will rub on the fork?
The brakes are hydraulic Shimano MT-200
Thank you.
Doug
 

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JES2020

Well-Known Member
Region
Other
Can I install a Front hub motor for a SP roll elite bike with disc brakes? Does anyone know if the rotor will rub on the fork?
The brakes are hydraulic Shimano MT-200
Thank you.
Doug

From endless-sphere forum:​

"Re: Disadvantages of front wheel drive for ebike?



First of all, if your bike has 7 or 8 gears in back, it is not in any way easier to do a front hub, vs a rear.

Because of much better traction when the power is in back, in almost every case a rear motor is better. And if you have an aluminum shock fork in front, it gets very technical to make a hub motor work safely. Some shock forks can be used, but they lock up and become rigid when the motor is pulling.

But there are exceptions, which make a front wheel just about the only way. The typical adult trike is the biggest user of front hubs. They have rear drive trains and axles that usually make using a rear motor impossible, or at least a need a welder type situation.

Beach cruisers with a coaster brake, have no brakes at all if you change the rear wheel to a motor wheel. Those can usually be adapted to have other brakes fairly easy though. Might take a welder to do a nice conversion to disk.

Others just have internal gear shifter hubs, and want to keep that, because they loathe derailleurs.

And lastly, the really exotic bikes, belt drive, shaft drive, and so forth, can never use a different rear wheel.


Other type beach cruisers can be a good ride with a front motor, when they are the type with a 7 speed rear gear and rim brakes. They are the one type bike that tends to have a very strong front fork. And you won't be riding it much in dirt, so the traction situation is not a big problem. The only two bikes I'd really recomend a front motor for, are the schwinn trikes and the 7 speed cruisers.


FWIW, I rode about 5000 miles on front hubs, and my main reason was wanting to keep my rear gears on that particular bike. I even built a 50 mph, very high power front hub racing bike. It was fun to learn to power slide the front wheel, and extremely dangerous. But today, all my front hubs gather dust, everything I have runs a rear hub."
 

tomjasz

Well-Known Member
Region
USA
City
Minnesnowta
No problem with a steel fork and two quality torque arms. Disc brake versions line up fine. Ebikes.ca has excellent front totque arms . Use two. Someone posted cherry picked negatives last week. Just clueless with poor reading comprehension. Grin engineer Justin Elmore wouldn’t destroy his business with a dangerous product recommendation. Break down the often quoted ES thread and each poster offers a scenario where a front drive can can be safe.
 

JES2020

Well-Known Member
Region
Other
No problem with a steel fork and two quality torque arms. Disc brake versions line up fine. Ebikes.ca has excellent front totque arms . Use two. Someone posted cherry picked negatives last week. Just clueless with poor reading comprehension. Grin engineer Justin Elmore wouldn’t destroy his business with a dangerous product recommendation. Break down the often quoted ES thread and each poster offers a scenario where a front drive can can be safe.
Major malfunction
 

m@Robertson

Well-Known Member
Region
USA
No problem with a steel fork and two quality torque arms. Disc brake versions line up fine. Ebikes.ca has excellent front totque arms . Use two. Someone posted cherry picked negatives last week. Just clueless with poor reading comprehension. Grin engineer Justin Elmore wouldn’t destroy his business with a dangerous product recommendation. Break down the often quoted ES thread and each poster offers a scenario where a front drive can can be safe.
Speaking from experience, this is absolutely correct. One thing you don't want to do is use cheap-ass torque arms. In particular the ones that use a hose clamp to bind to the fork arm. Those are of marginal utility even when properly installed, which is almost never.

The breaks occur when
  • you are talking about alloy forks (steel bends; alloy snaps)
  • You do not properly install torque arm(s); they come loose and the dropouts are destroyed
  • You use a hub motor on a suspension fork, which has the identical issue that an alloy fork does, plus no 2-piece fork on Earth was designed to be pulled upon strongly, which is a profound issue on a fork whose blades are two-piece. I have seen motors literally pull suspension fork blades forward and outward in real time under throttle as I ride.
There ARE ways to mitigate the risks to become acceptable on even these types of forks. But if you have to ask, you don't know enough to safely take the risk :D. I'll say this much: They involve dialing the amps way back. 250w EU-compliant motors are just fine for example (I rented one in Amsterdam for a day just a couple weeks ago and it wasn't even remotely powerful enough to cause any concern). 'domestic' bikes like what E-Cells offers are to my mind either profoundly flawed or they have been de-fanged to the point they are finally safe to use over the long term.

2100 miles on the green one below and still going strong. 45Nm motor. About 7000 so far on the orange one. An 80Nm motor. Both use a Grin eyelet 'v2' torque arm. 1/4" stainless steel. I have others these are just the easiest, prettiest pictures I came across.

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