lightweight ebike

[iflyadesk]

If you must fit a crank drive to it, I'd go as low as a BBS01 at 15 amps.

Charlotte Cycles has an 8Fun kit with the BBS01. It's $200 less. Other than the lower price and the lower power (that's less likely to break things per your suggestion), are there other reasons to go with the BBS01? Any weight difference? Any difference in reliability? Range? etc...

 

[d8veh]

Normally, I'd recommend the BBS02 because it has more power for very little weight disadvantage. I hate to have to say it, but that's just the wrong bike for converting. All that technical excellence would be wasted as much of it starts to become a disadvantage as soon as you add a motor. Take my advice and get a more suitable donor.

 

[friendly1uk]

Personally, I have a lot of reservations about that bike. It's a complete waste of it to fit a 750w BBS02. Sure, it'll be light, but you don't need so light when you have that much power. To me, it would make more sense to keep that bike how it is an get a lightweight hybrid or cyclocross type bike with disc brakes. That's if you insist on a BBS02. I've got a feeling your present braking system would be overwhelmed by the extra speed. The other reservation I have is the torque. Your frame isn't designed to take any torque around the bottom bracket, and a BBS02 will make a lot. If you must fit a crank drive to it, I'd go as low as a BBS01 at 15 amps.
I built this one, which was about 19kg and could easily sustain 20 mph with its "250w" Bafang CST motor. It was actually featured on a TV show (The Gadget Show season 21 episode 9). The bike and kit cost me about £800. It would still be a good build with a BBS02, which would make it about 5 mph faster.

Is that 48v and a 201 d8veh?

I'm looking at a 26" 12kg mtb next, with a 48v dolphin and 20A controller. I see the 260 will knock on the door of 24mph but won't like an gradient. I forget what justins simulator calls the 201 though.

Sports bikes are ok when your stood on the pedals, but once you are simply getting a ride while offering support, you want a comfy seat not a razor like saddle. Your seating position becomes less hunched transferring more weight to the seat and the whole experience is somewhat different. The only reason to really want a few kg gone is if your picking it up and carrying it.

I think 20kg perfectly manageable. 25kg is where the HSE steps in and says it's a two man carry.

 

[LewTwo]

Normally, I'd recommend the BBS02 because it has more power for very little weight disadvantage. I hate to have to say it, but that's just the wrong bike for converting. All that technical excellence would be wasted as much of it starts to become a disadvantage as soon as you add a motor. Take my advice and get a more suitable donor.

I have to agree. The pictures the OP posted show a beautiful machine.
It would almost be a crime to mess with it and it is not really a good base for conversion to an e-bike.

hub motor problems:
... 20 spoke wheels
... hard to tell from the picture but would either set of drop out accept a slide in axle
... toquer arms might be a challenge as well

mid drive problems:
... single speed
... gates belt

ride comfort problems:
(with an e-bike your average speed is going to increase and so will the roughness of the ride - your back will notice)
... 17mm rims and 25mm high pressure tires are going to make for a rough rides at higher speeds
... no shock absorption in the current frame, seat post or fork
... lowering the seat for a less aggressive posture will leave little room for a good suspension seat post
... suspension seats are one 'size fits all' (worst case scenario is a 350 pound rider ... do the math for 150 pound rider)

Look for a new donor bike. Consider:
... Aluminum frame (for the obvious weight reason)
... Avoid suspension frames or forks (for the obvious weight reasons)
... Consider smaller wheels 26, 24, even 20 inch (less tire, tube, wheel and shorter spokes = less weight)
... Under 20-25mph rim brakes work well and they weight less
... Be sure you have enough room for a good suspension seat post like the Thunderbuster (and fit the correct elastomer)
... Pay attention to the tires. For urban riding avoid knobbies and steel bead wires (for the obvious weight reasons)
... Have the battery mounted in the bottom of the triangle to keep the center of gravity low ... easier to lift and/or carry.

I hesitate to say anything regarding the motor because for your parameters it is mainly personal opinion and opinions are like ...
Personally I think I would go for the mid drive at about 500 peak watts and a 3 speed IGH (internally geared hub) ...
Although many people berate them: front hub motors are simple and there are an awful lot of e-bikes made in that configuration.

 

[iflyadesk]

First off, thank you all so much for all the advice. I sincerely appreciate it!

I want to dig into some of your comments. Please don't take this as combative or argumentative. I am just trying to learn by digging deeper!

Normally, I'd recommend the BBS02 because it has more power for very little weight disadvantage. I hate to have to say it, but that's just the wrong bike for converting. All that technical excellence would be wasted as much of it starts to become a disadvantage as soon as you add a motor. Take my advice and get a more suitable donor.

I have to agree. The pictures the OP posted show a beautiful machine.
It would almost be a crime to mess with it and it is not really a good base for conversion to an e-bike.

Why is taking an elegant, fun, lightweight, and extremely comfortable bike and adding a motor to it such a bad thing? I have this bike tuned in to exactly the right geometry for my body and it is so very comfortable, you wouldn't even believe. Every time I ride a different bike, I'm reminded of just how many hours I've spent on a bike fitting machine testing saddles, grips, cranks, and stems to get everything just perfect.

hub motor problems:
... 20 spoke wheels

These are Mavic Ksyrium Wheels. I would have never cut the spokes and reuse the rims. They are worth too much in resale value as a complete set. So if I go hub motor, I'm going to have to build a new wheel from scratch. And don't let the low spoke count fool you. These wheels are tough. I ride onto and off of curbs, potholes, manholes, and those crazy metal plates they use to cover big holes in the road every day. I bunnyhop over them when I can, but sometimes it comes at you too fast when darting around a car or something.

... hard to tell from the picture but would either set of drop out accept a slide in axle

What do you mean? Do you mean slide-in drop outs? They have to be slide in to accomodate the belt, so a bolt on slide in axle should work if I'm understanding you correctly.

... toquer arms might be a challenge as well

No clue about how hard that will be. I could ask the bike shop when I take it there, although I gotta be honest, I'm leaning more towards mid-drive.

mid drive problems:
... single speed
... gates belt

I don't know if you can tell from my pictures, but the rear wheel has Shimano 11sp cassette spline. The gates sprocket is aligned with spacers. I can move it in and out wherever is necessary to accomodate the front chainring's offset. What's more, the CDX Centertrack Gates belt is much less sensitive to flawless chainline alignment than the previous models.

ride comfort problems:
(with an e-bike your average speed is going to increase and so will the roughness of the ride - your back will notice)

You're probably right. I rented a Trek XM700+ (Bosch Drive 28mph) for a day and rode it 40 miles and an average speed of 26mph. Things come at you faster and they hit harder. It had a 35mm front suspension and it was bottoming out a lot. I thought the bike was going to fall apart and then I realized that god awful sound was chainslap. Riding a gates carbon belt for years you forget how many horrible sounds a chain makes.

... 17mm rims and 25mm high pressure tires are going to make for a rough rides at higher speeds

I can get bigger tires. I actually tried some 32mm tires once running 70psi but they weren't any more comfortable and I got several flats after riding years with no flats. So I went back to the 25s and no issues since.

... no shock absorption in the current frame, seat post or fork

Isn't that what your arms and legs are for? If a big bump comes, you use your body as a spring, otherwise the little stuff is fine. When I raced XC, I would use a rigid bike (mind you at the time full suspension was heavy and worthless and front suspension would stiffen up badly at low temperatures so rigid had a huge weight advantage with very little disadvantage. I used to kill the competition because it also just makes you much better at bike control.

... lowering the seat for a less aggressive posture will leave little room for a good suspension seat post
... suspension seats are one 'size fits all' (worst case scenario is a 350 pound rider ... do the math for 150 pound rider)

I would be hesitant to change my geometry at all. And although it may not look it, my seat is actually very comfortable. The most important thing in seat comfort is not cushioning. Think of sitting on a hard coffee table. Now imagine adding a soft pillow and sitting on that. It feels better at first, but before long, your sit bones press through the squishy material and you're right back where you started. What's far more important than squishy is springy and a shape that matches your sit bones precisely. My saddle is thin and flat with long seat rails so it works like a spring to absorb the bigger hits, but fits my sit bones perfectly and therefore doesn't need foam or gel. It's kind of like a leather saddle with a built in spring, just much, much lighter.

Look for a new donor bike. Consider:
... Aluminum frame (for the obvious weight reason)

Aluminum frames beat the crap out of me. I much prefer steel and carbon.

... Avoid suspension frames or forks (for the obvious weight reasons)

But isn't that what's wrong with my bike? The fact it doesn't have suspension?

... Consider smaller wheels 26, 24, even 20 inch (less tire, tube, wheel and shorter spokes = less weight)

Don't smaller wheels ride rougher? I once had a recumbent with 20" in the front and 24" in the rear and it beat the hell out of me.

... Under 20-25mph rim brakes work well and they weight less

I have rim brakes now. They work great when it's dry. But when it's wet... If I were going to start from scratch, I would want hydraulic disc brakes.

... Be sure you have enough room for a good suspension seat post like the Thunderbuster (and fit the correct elastomer)

I've heard nothing but good things about the Thudbuster. I could see adding that to a hardtail to create a kind of dual-suspension bike that weighs less. But per your comment above, I wouldn't have a front suspension fork. Do you ride a setup like this? With "rear suspension" and no front suspension? Maybe because on an electric bike you're suggesting I would ride more like a Harley where the weight is on my butt not my hands, a front suspension is wasted? If that's the case, wouldn't the aggressive geometry of a mountain bike be the wrong donor? Wouldn't a cruiser be a better donor for that?

... Pay attention to the tires. For urban riding avoid knobbies and steel bead wires (for the obvious weight reasons)

Do you have a favorite brand/model? Something supple, light, and resistant to flats?

... Have the battery mounted in the bottom of the triangle to keep the center of gravity low ... easier to lift and/or carry.

Makes sense. Thank you!

I hesitate to say anything regarding the motor because for your parameters it is mainly personal opinion and opinions are like ...

I can't tell you how much I appreciate a complete stranger taking the time to put so much effort into sharing your opinions with me.
So thank you and please don't hold back!

Personally I think I would go for the mid drive at about 500 peak watts and a 3 speed IGH (internally geared hub) ...

Once I realized the mid drive can spin faster than I can pedal, what's wrong with having a single speed? I know I'd need a lower gear for steep hills (but I don't have any) and the higher gears for higher speeds (but it'll speed limited to 20mph anyway won't it? Since it has the "throttle" those are limited to 20mph, right?). Why add the weight of an IGH?

Although many people berate them: front hub motors are simple and there are an awful lot of e-bikes made in that configuration.

I'm guessing my dainty carbon fork is a poor candidate for this. However, if I went with a new steel fork (or even suspension fork) with a disc brake mount, then I could potentially solve a lot of problems at once: stronger fork, front suspension, disc brake, motor. Thoughts?

If I were going to start from scratch with a new donor bike, my first thought would be an endurance frame carbon road bike that has some sort of compliant frame (like Trek Domane or Specialized Roubaix) and hydraulic disc brakes out of the box. This way I could have a comfy geometry, comfy low travel "suspension" AND 18lb/8.2kg starting weight.

Thoughts?

 

[Esting]

I think you should strap a 20LB on the down tube of your bike and take it for a ride and see , what it like to ride , you will be amazed at how different the bike will ride and I don't mean in a good way.

 

[LewTwo]

I want to dig into some of your comments. Please don't take this as combative or argumentative. I am just trying to learn by digging deeper!

A lot to process 8)

These are Mavic Ksyrium Wheels. I would have never cut the spokes and reuse the rims. They are worth too much in resale value as a complete set. So if I go hub motor, I'm going to have to build a new wheel from scratch. And don't let the low spoke count fool you. These wheels are tough. I ride onto and off of curbs, potholes, manholes, and those crazy metal plates they use to cover big holes in the road every day. I bunnyhop over them when I can, but sometimes it comes at you too fast when darting around a car or something.

I am sure that they are excellent ... and that was kind of my point. Be a shame to put something else on that bike.

... hard to tell from the picture but would either set of drop out accept a slide in axle

What do you mean? Do you mean slide-in drop outs? They have to be slide in to accomodate the belt, so a bolt on slide in axle should work if I'm understanding you correctly.

Hub motors typically have a 3/8 inch (actually I think it is 10mm) diameter axle with flats machined on two opposite sides. Those two sides have to slide into the dropouts and help resist turning. It appeared to me that your bike might have through hole axles (I did say I could not tell). I thought its frame might have round holes that the axles insert through (they do build bikes like that).

... toquer arms might be a challenge as well

No clue about how hard that will be. I could ask the bike shop when I take it there, although I gotta be honest, I'm leaning more towards mid-drive.

See above ... Some people are particular about having the arms behind the rotation (me not so much).
These were the principal reasons for using a mid drive rather than a hub however to be fair there are some concerns about the mid drive.

mid drive problems:
... single speed
... gates belt

I don't know if you can tell from my pictures, but the rear wheel has Shimano 11sp cassette spline. The gates sprocket is aligned with spacers. I can move it in and out wherever is necessary to accomodate the front chainring's offset. What's more, the CDX Centertrack Gates belt is much less sensitive to flawless chainline alignment than the previous models.

I like that gates drive however the bafang mid drive would have to be adapted to use it. That may be as simple as replacing the proprietary bafang sprocket with a aftermarket spider. If not then the mechanic is likely to choose the simplest solution which is replace the Gates belt system.

... 17mm rims and 25mm high pressure tires are going to make for a rough rides at higher speeds

I can get bigger tires. I actually tried some 32mm tires once running 70psi but they weren't any more comfortable and I got several flats after riding years with no flats. So I went back to the 25s and no issues since.

My lightweight e-bike has 700x25C Thickslicks. However the top speed on it is less than 18 MPH. I have replaced the seat with something with a bit more padding. I was simply pointing out that there is not much of an option for tires that are wider and softer.

... no shock absorption in the current frame, seat post or fork

Isn't that what your arms and legs are for? ...

Not mine. My butt is for sitting with just enough weight on the handlebars to maintain balance. I would just as soon not have to stand in the pedals any more than absolutely necessary. In truth much depends on the condition of the surface you are riding on. Houston's streets are not very well maintained (and the sidewalks are worse).

... lowering the seat for a less aggressive posture will leave little room for a good suspension seat post
... suspension seats are one 'size fits all' (worst case scenario is a 350 pound rider ... do the math for 150 pound rider)

I would be hesitant to change my geometry at all. ...

My bad ... I think it was someone else that mentioned a suspension seat and less aggressive posture.

Keep in mind that the following applies a different donor bike that emphasizes keeping the weight down.

Look for a new donor bike. Consider:
... Aluminum frame (for the obvious weight reason)

Aluminum frames beat the crap out of me. I much prefer steel and carbon.

... Avoid suspension frames or forks (for the obvious weight reasons)

But isn't that what's wrong with my bike? The fact it doesn't have suspension?

Your biggest parameter is weight (30 pounds complete).
Compared to steel frames aluminum frames are usually lighter.
Carbon Fiber and Titanium are lighter yet ... but more expensive.
Suspension frames and Suspension forks are relatively heavy.
A GOOD suspension seat post would be the most effective shock absorption for the least weight.

... Consider smaller wheels 26, 24, even 20 inch (less tire, tube, wheel and shorter spokes = less weight)

Don't smaller wheels ride rougher? I once had a recumbent with 20" in the front and 24" in the rear and it beat the hell out of me.

That is an opened ended argument argument and relative to the terrain. Get a smooth enough surface and you will not be able to tell the difference between a 2 inch caster and 6 foot tractor tire ... except for the rolling resistance. For smooth paved urban streets there is not going to be much effective difference in the ride between 20 and 29 inch diameter ... but there is a lot of difference in the weight.

... Under 20-25mph rim brakes work well and they weight less

I have rim brakes now. They work great when it's dry. But when it's wet... If I were going to start from scratch, I would want hydraulic disc brakes.

As my Thai friends would say "up to you". I only had the 'wet brake' problem once. The bike and I went into the intercoastal canal but to be fair it was a junk bike with worn out pads that had crystallized years prior to my shortened ride. As far as I know the bike is still somewhere on the bottom of the canal.

... Be sure you have enough room for a good suspension seat post like the Thunderbuster (and fit the correct elastomer)

I've heard nothing but good things about the Thudbuster. ... Do you ride a setup like this? .... Wouldn't a cruiser be a better donor for that?

If you want to see what I ride most of the time then look at my signature. Most cruisers would be heavy. A mountain/hybrid bike frames typically has a top bar that descends from front to rear allowing for a taller seat post (unlike a road frame with a horizontal top bar). ... and no I do not have a thudbuster because there is insufficient room between the seat and the top bar (that will be corrected on a future build).

... Pay attention to the tires. For urban riding avoid knobbies and steel bead wires (for the obvious weight reasons)

Do you have a favorite brand/model? Something supple, light, and resistant to flats?

Lightest thing I could find were red label Freedom thickslicks 700x25C. In that size they are high pressure --- not supple. No flats as of yet.

Personally I think I would go for the mid drive at about 500 peak watts and a 3 speed IGH (internally geared hub) ...

Once I realized the mid drive can spin faster than I can pedal, what's wrong with having a single speed? I know I'd need a lower gear for steep hills (but I don't have any) and the higher gears for higher speeds (but it'll speed limited to 20mph anyway won't it? Since it has the "throttle" those are limited to 20mph, right?). Why add the weight of an IGH?

Why would you think an IGH would add weight? An IGH hub is NOT a lot heavier (if any) than a 20 something speed derailleur system and all its various bits and pieces. If one only needs a few gears then they can be very effective. Of course a single speed hub is less weight than a three speed hub. I like to have a lower gear available in case the electric (battery, motor, controller, cables, connectors) goes south and I still need to get home.

Legally it is limited to 20MPH under motor power alone on a flat (presumably) paved surface. Realistically it depends on combination of motor, battery voltage, grade, load and controller programing. A controller may have speed limiter built into it but they are not necessarily effective. Trust me on this... many individuals on this forum would be most unhappy if they were effectively limited to 20MPH.

Although many people berate them: front hub motors are simple and there are an awful lot of e-bikes made in that configuration.

I'm guessing my dainty carbon fork is a poor candidate for this. However, if I went with a new steel fork (or even suspension fork) with a disc brake mount, then I could potentially solve a lot of problems at once: stronger fork, front suspension, disc brake, motor. Thoughts?

If I were going to start from scratch with a new donor bike, my first thought would be an endurance frame carbon road bike that has some sort of compliant frame (like Trek Domane or Specialized Roubaix) and hydraulic disc brakes out of the box. This way I could have a comfy geometry, comfy low travel "suspension" AND 18lb/8.2kg starting weight.

Thoughts?

My thoughts are:
If you want to stick with the frame that you have then go with a mid drive and keep your wheels.
Consider a Thudbuster if you are happy with the current geometry (it looks like you have plenty of room). However be forewarned that your 'prefered geometry' and posture may change once you are riding more than pedaling.

I think the Trek Domane or Specialized Roubaix greatly exceed your budget parameter. Aside from the drop bars they look as much like a classic cruiser as a road bike. My point being there is no clear definition of a road bike, vs a cruiser, vs a hybrid, vs mountain bike, vs BMX, vs ... just happens to be what the marketing department felt they could sale more of that day. I have probably just offended someone but from watching the presidential primary race that seems to be in vogue. :|

 

[d8veh]

Another problem i just thought of. The BBS01/2 is designed to go into tubular bottom brackets. The clearance between the motor and the axle tube is not very much, so a thick carbon fibre BB won't pass. You'd have to borrow one from somewhere to see if it fits before committing to purchase.

 

[d8veh]

Is that 48v and a 201 d8veh?

I'm looking at a 26" 12kg mtb next, with a 48v dolphin and 20A controller. I see the 260 will knock on the door of 24mph but won't like an gradient. I forget what justins simulator calls the 201 though.

It's an Oxydrive kit 36v 15A 260 rpm.

48v 20A 260 RPM will be fine for hill-climbing unless you only have one leg.

 

[iflyadesk]

I rode a Cannondale Slate Ultegra today with 650 x 42 tires and a 35mm suspension fork. I can see why fat tires and a suspension fork would be desirable... particularly if it can be done without a huge weight penalty.

In other news, I rode my bike on "the commute" over that bridge this afternoon. The last two times I did it on the Trek XM700+ Bosch Drive eBike. (Most days I drive—why I'm wanting eBike.) First time (with the Trek) I went up at 28mph pedaling pretty hard. Second time I still pedaled (it's pedal assist only) but was very gentile and managed about 18-20mph the whole way up. Both times I was well over 30mph on the way down. But today, I was on my single speed. On the way up, I was so slow I really could have walked about the same speed. Maybe 3mph. There were 6 other bikers on the bridge and they were all walking (mostly tourists and families, not serious bikers). Then when I got to the top, I was looking forward to going fast again but the wind must have been 30mph because going down I had to pedal very hard to go maybe 10mph. At one point I stopped pedaling and came to a complete stop in 7 seconds!

Bottom line: I can't wait to get my eBike... be it converting this bike, starting with a new donor, or buying one off the shelf.

The value is real!