# cruiser + front hub motor - safety?



## high_desert_mud (Jul 22, 2017)

I'm doing a relatively low-power cruiser conversion for my mom. she's not an experienced biker by any stretch, and will be using the cruiser year-round, including towing a small trailer (kids; attaches at rear dropout). pavement or gravel path only.

I'm wondering - does this create a crash risk from unexpected spinout / traction loss on front (cornering, wet pavement)?

Thank you for your thoughts!

DETAILS:

For reasons, I would prefer to do front drive:

balance of bike when picking up (the battery must be on the rear rack due to space)
ability to use IGH

Kit:

I will be doing a BB torque sensor, versus throttle or crank-rotation sensor, which will hopefully reduce 'sudden power' surges that could exacerbate this.
Most likely Grin eZee or G301, possibly GMAC (software-limited on power) to support regen braking.


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## honkinunit (Aug 6, 2004)

high_desert_mud said:


> I'm doing a relatively low-power cruiser conversion for my mom. she's not an experienced biker by any stretch, and will be using the cruiser year-round, including towing a small trailer (kids; attaches at rear dropout). pavement or gravel path only.
> 
> I'm wondering - does this create a crash risk from unexpected spinout / traction loss on front (cornering, wet pavement)?
> 
> ...


This forum generally talks about factory mid-drive eMTBs.

I'll say this though. Unless you are truly interested in doing a science fair project, you are much better off just finding your mom a used mid-drive commuter/trekking bike if you are concerned that she can't operate a throttle. Most of the aftermarket BB torque sensors are garbage, and the odds of getting it all to work together smoothly with a front hubmotor are low.


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## high_desert_mud (Jul 22, 2017)

honkinunit said:


> better off just finding your mom a used mid-drive commuter/trekking bike if you are concerned that she can't operate a throttle. Most of the aftermarket BB torque sensors are garbage, and the odds of getting it all to work together smoothly with a front hubmotor are low.


excellent point, and true. For this reason, I'm using Grin/ebikes.ca stuff - while not cheap, I have heard it works quite well**. It is certainly well engineered and I've found them very knowledgeable and helpful. For eMTB the low CG, low overall weight, and no change to unsprung weight - certainly means integrated BB motors have a big advantage; however for a cruiser, none of those come into play (especially not the biggie - unsprung weight - I don't think she'll be doing any ~ springing  )

Her bike won't have a manual throttle; maybe to reprase my question:

a cruiser already has weight distribution further rear than types (less available traction in front)
adding motor thrust reduces the available traction for cornering on whichever wheel
she will not accelerate quickly, but any acceleration reduces front wheel available traction (hopefully not that relevant for cornering)
for (non-avid bikers, even more so) loosing front wheel traction is much harder to recover from than rear-wheel

--> so as a practical matter, in a "heavy-rear" bike, with a low-thrust front wheel, in "good" but "all year" conditions (eg, some wet road), do folks see significant washout of front wheel?


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## high_desert_mud (Jul 22, 2017)

** from last post == I'm using a Grin GMAC/Phaserunner/CycleAnalyst on my BigFatDummy - but only occasionally (I swap the whole fork) so I have not installed a thrust sensor to experience the PAS. But the overall kit is great, and seems to have a great reputation.


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## Bigwheel (Jan 12, 2004)

"This forum generally talks about factory mid-drive eMTBs."

While this is true it is not labeled as exclusive to eMTB's:









There are far more hub motor eBikes out and about than mid drives, mainly due to their popularity in China. A hub motor bike is obviously not the way to go for MTB but for road use many prefer them.

I also use Grin products on my hub (front) motor all road bikes. Thousands of miles and no issues with handling whatsoever. This includes riding trails and steep loose mining and logging roads. For those events the two wheel drive aspect is king. To me the weight distribution with the front hub, battery mounted as low as possible on the down tube and my weight biased towards the rear has a net effect of very stable and predictable handling and no evidence of the motor taking over steering control. Not enough weight so that I can't unweight the front end either.

I would suggest that you do put a throttle on there especially if she will be towing even more weight. She will find it useful getting going enough to engage the PAS and her choice to use or not use. My road bikes have no PAS at all and through the CA I can set my watt limits and cruise control leaving my drivetrain input up to whatever I feel like and as natural a cadence as my non eBike.

But I do have a mid kit with torque sensing on my MTB and wouldn't have it any other way.


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## matt4x4 (Dec 21, 2013)

Front hubs need Torque Arms on both sides! You mention its low power, so can assume 250W, still good practice to install 2 ta's.
Ideally you want a steel front rigid fork for its stiffness.

Grintech www.ebikes.ca in Vancouver Canada are the leaders in the ebike industry!


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## richj8990 (Apr 4, 2017)

Bigwheel said:


> A hub motor bike is obviously not the way to go for MTB but for road use many prefer them.
> 
> I also use Grin products on my hub (front) motor all road bikes. Thousands of miles and no issues with handling whatsoever. This includes riding trails and steep loose mining and logging roads.
> 
> But I do have a mid kit with torque sensing on my MTB and wouldn't have it any other way.


"Hub (front) motor, thousands of miles and no issues...including trails and logging roads...but a hub motor is 'obviously' not the way to go for MTB"?

Sounds like you are of two minds on the topic...which alternate every 10 seconds.

I recently got a decent chunk of 'free' money to spend on whatever I wanted, thought about a mid-drive conversion, or a whole new mid-drive e-bike...

And then about a month ago I caught up with a group of experienced riders 1/2 way up on a fairly steep hill. Enough room to say hello and pass them. It took the fastest guy about 2 minutes to catch up to me on his non-ebike, and the rest of them were way behind. To put this in perpective, this was with a $280 Chinese off-brand bike, front hub motor, and a 75% worn WTB Ranger 2.8 with mediocre knobs that was on its last legs. I just completely blew them away. I didn't really mean to, I don't want to be "One of those" E-bikers and I even told them that at the top and they were cool with it.

From the very limited data I have on ebike climbs vs. XC pro non-ebike climbs, the front hub drive, with the right type and width of front tire, can climb almost as fast as the non-ebike climbing KOM by a pro racer, usually within 25% or less, sometimes faster than the KOM. So please don't tell me hub drives don't belong offroad. I've had the money to buy a mid-drive for a while and I really don't see much point in doing that right now, I'm perfectly happy climbing offroad with a front hub drive. And that's with the front hub ebike more or less dedicated to offroad, now that I have a 24 lb XC non-ebike for pavement.


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## J.B. Weld (Aug 13, 2012)

richj8990 said:


> "Hub (front) motor, thousands of miles and no issues...including trails and logging roads...but a hub motor is 'obviously' not the way to go for MTB"?
> 
> Sounds like you are of two minds on the topic...which alternate every 10 seconds.
> 
> ...


Most people don't want to muscle a 20lb wheel over obstacles, also they're illegal on most trails.


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## Jack7782 (Jan 1, 2009)

*Start with getting a low step frame!*



high_desert_mud said:


> I'm doing a relatively low-power cruiser conversion for my mom. she's not an experienced biker by any stretch, and will be using the cruiser year-round, including towing a small trailer (kids; attaches at rear dropout). pavement or gravel path only.
> 
> [/LIST]


Stability and balance on and off the bike - a low step frame is your best setup for towing a trailer with kids. I would think that a throttle would be useful to get started too. Here is my street bike, an IZIP Vibe+ that features a mid-drive - and has an optional throttle kit, that I don't have.


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## matt4x4 (Dec 21, 2013)

I have been using a front dd hub, typical 9C clone, and only using one t.a. and its been fine, even in the winter, snow and ice. My t.a. is just a steel plate I cut notches to fit, and using hose clamps to secure. Not a single problem! 

Ideally you do want two t.a.'s installed, and for a front hub, ideally a steel fork. But my setup is so weak, 36V 26A that there have been no issues whatsoever. I believe my fork is more then likely alum. 

Front hub
- low power setups
- low speed setups
- ta's are a must with any hub front or rear
- easier to fix a flat tire
- 'unique' handling in some circumstances - like lifting the front up to pop a curb, going around a corner on snow/ice, the usual front drive problems with ebiking.

Rear Hubs
- way more ideal
- two ta's
- can use way more power if you choose to, within the law of course LOLOLOL
- better handling
- more of a problem replacing a flat, but not a big deal once you have done it a few times LOLOL I've done it many a times LOLOL

Never install a higher powered hub motor on a front fork, its not a wise idea at all.


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