Fat MAC: Is it do-able?

[Gregor]

I have an aluminum (no-name, probably china made) fat bike frame that I am working with. The rear dropout is 170mm with 8mm thick horizontal dropouts. this makes the total width 186mm. I am looking to makes this into a 1000w build and I am too challenged with some design limitations. you can reduce the width 10mm, so you are down to 176mm. I would allow 2mm pe rside for washers and/or lockwashers. On my frame I will be using a steel torque arm on the inside of the dropout as it is easier to mount it there. I am leaning towards 3.0 or 3.5" tires as it is a problem to use more than a single speed freewheel if you have the 4" tires on there. Finding mid size rims that are 36 hole may also pose a problem--any sources on these from other members, maybe with prices if possible?

 

[lutefisk]

First post on E-S, so take this with a grain of salt.

I have a Surly Moonlander, bought it with the intent of making it an ebike, but the problems you're running into put me off the idea of a hubmotor, and the 100mm bottom bracket rules out most mid-drives. Tired of running into a brick wall, I zigged and decided to purchase a used full-suspension 26" MTB, and installed a 750W BB02 setup.

The reason I mention this is because I wanted to compare the rides. I understand that you're looking to conquer crushed concrete roads littered with golf ball sized gravel, at speeds up to 25mph. In those conditions, I'd be tempted to ride the FS bike over the fatbike. The Moonlander has the fattest tires currently available, and at pressures high enough to avoid a snakebite at speed, it's really bouncy. If you have a suspension bike with good compliance, the damping really helps keep the rubber on the road, even with 2.5" tires. In a perfect world, 5" tires on a full suspension fatbike would have you FLYING across the type of roads you describe, but that's currently a $5K+ dream

Another thing to consider about fatbikes is that their tire diameter is really closer to 29". Makes things even harder on the hubmotors.

So if I were you (heh, here it comes...), and I happened to have 3 6s 10Ah batteries lying around with the means to charge them, I would hunt down a nice full-suspension MTB with a 67mm BB. Then I'd order up a 48V BB02 kit from em3ev.com. I know you said that you considered the BB02 inadequate for your needs, and the programming was too troublesome. I would have agreed before installing and programming mine. Now, I can't stay off the dang bike. Regarding it's climbing ability--if you can stay on the bike, it can climb it. Best of all, it's practically silent.

As for the programming, if you're willing to invest the time necessary to fab custom dropouts and rewire MACs, I think you'd be up to the task of buying a USB converter on ebay for $1 and putting some shrinkwrap on the bare ends of the included connectors, and then installing some software on a Windows XP machine. Yeah, it's a pain, but once it's done, you won't believe how easy it was, given the profound changes it makes to the setup.

Yikes, this is getting long, but hopefully you'll bear with me. Just wanted to add that if you want to do a fat ebike, IMHO it will get expensive, fast, mostly because you're in uncharted territory. If you just want to get into ebiking, get a full suspension 26" mtb. It should handle the type of riding you're doing, and there's lots of ebike options that are tried-and-tested.

 

[SprocketLocket]

ChoopaK, I may be going out on a limb here, but regarding heat & high voltage with MAC, the fact you were running a 6-turn, and a non-EM3EV controller, are both red flags to me. (And was yours a first-gen or 2nd gen?) So yes, I wouldn't do that. But I will be getting the 12-turn, the slowest wind they make, and a properly fast controller. I also ride gently, normally. And plan to probably experiment with oil cooling either way. The beauty is, I can always use 48V if I decide 72V is too much, or if I'm doing a shorter ride. EM3EV does include an up-to 72V controller option in his kit, and I have found him to be conservative, or at least careful about matching kit items. Of all the things he warned me about, the 72V wasn't one of them, LOL. But I will pay attention.

Lutefisk: I'm honored to have your first post in my thread! Welcome to the board! I'm pretty new here myself
Don't apologize for length, drop it on me.
Well, EM3EV sells only 2 motors: MAC and the BBS02. That tells me something right there. So, the BBS02 is #2 for me right now. I keep going back and forth. I just don't think it would be as pleasant of an experience... This is just for pleasure, not a commute, which affects my choices. Using the gears is a mixed blessing. First, yeah I wouldn't be able to do this with a fatbike at all. Then, I'd have to be shifting gears all the time. See, I do a lot of stopping "to smell the roses". Think sightseeing. That's a lot of gear shifting and distraction while I want to focus on the experience (not sure, but that's what I'm thinking). On a commuter, that extra control is probably desirable, and you're already focused.
BBS02 is only medium power, so reliant on gear selection. Mostly though, I think current mid-drive solutions, and the BBS02 specifically, are works in progress, whereas the MAC, especially from EM3EV, is strongly refined. I expect the BBS02 to be obsoleted quickly. Following Neptronix's experience, the built-in controller seems to be crap, it needs serious tweaking right out of the box (I don't fear the programming whatsoever, just a statement on factory quality), and there are other issues I'll leave for those threads. I am fascinated by its quiet-ness, the freedom to change wheels, and improved hill climbing ability. I find I just don't "want" it enough. I'm sure if I could ride each, I'd know right away, but barring that, sometimes you just have to make the best decision you can, and I find even with research, I often am wrong. That's demoralizing to hear you kept running into brick walls w/your Moonlander. Just sucks

Some clarifications, lutefisk: I never mentioned rewiring the MAC. 20-25mph is the fastest I think I'd "ever" want to go under motor power, and then only in ideal conditions (no one else on the road, good surface, feeling safe, or emergency). On unpaved roads, and just commonly anyway, I'd probably be doing only 8-13mph. I'm not in a hurry to get anywhere. I just don't want the damned bike bogging down on steep hills without momentum (is that too much to ask? It seems so). Golf ball sized concrete stones are not common, but they are around. Most of them rocks are under an inch. Still, dangerous and not fun. Safety is my first priority. Then fun. Leisure fun, not sport. Hence how the fat bike fits... I think. (Never having ridden one). Would you agree on that?

I really have no interest in a rear suspension, yet. I've done a ton of (mostly road) riding in my youth, and never yearned for a rear suspension. I did yearn for a front suspension before they even existed, though. BikesDirect is going to be releasing a somewhat cheaper fat bike with front suspension in coming months (no price announced). I might hold off till then. I've seen Neptronix and WesNewell talk about how how much of an upgrade they thought rear suspension was.. I respect them, but for me, I'm not seeing it. I'm not sure what a hub motor actually does to the ride, though? MAC is light, only about 8 pounds IIRC, about the same as a light DD, I think. What rear suspension does to the available battery space and overall complexity doesn't help either. At this point, I'd still take wider tires over a rear suspension. I could always get a suspension seat post, though (and probably will). But a normal mountain bike with front suspension is still a consideration. I am also concerned that the front suspensions on cheap mountain bikes will basically be crap.

Here's what you wrote that really intrigued me:

Regarding it's climbing ability--if you can stay on the bike, it can climb it.

Please, please, elaborate! Details! What have you tried so far? Care to share your and your bike's weight?
That kind of contradicts the little I've been able to find online. The closest I could get to info on this specific matter was 1Boris, who is somewhat heavy. He actually has both a MAC (10T, I think) and BBS02. He did a steep (off-road) hill test, and actually said that both motors eventually stalled, but the MAC won (went farther before stalling, and more confidently). That did it for me. I almost want to pay him a tip! So then, someone chimed in and told him he had the wrong front sprocket size or something, that he needed a smaller one. Whatever. I haven't even seen such a thing for sale? From what I know, the BBS02 comes with a replacement crank assembly, including front sprocket (or whatever it's called), and that's it?
A separate video I saw was a brief, poorly made video by one of the pro outfitters (hi-powercycles, I think), of 2 bikes going up a steep but only ~5-foot long incline, but from almost a standstill. Their BBS02 model "won", but clearly could not have kept up at that incline--it was nearly stalled at the top. By comparison, their Direct Drive model at 2000 watts (with normal wheels) was hopeless without momentum/RPM. Disappointing on both accounts.
The way I see it, if you're limiting a competition to the same amount of current, the BBS02 at 750 watts will win. But that's not how life works. The MAC can use much more wattage... not as much as DD, but a lot. So while it's less efficient during those times, for shorter distances at least, it also might be able to do things a BBS02 can't--I THINK (I don't know). Also, the belief that a BBS02 can't overheat or never gets hot, and can climb mountains "all day long" seems mythical too. I see the MAC as kind of a compromise between DD and mid-drive, all of which are appealing to me for differing reasons. My biggest concern for the MAC, outside axle size, is actually noise, believe it or not. I KNOW it can more than suit my local 'sightseeing'. Can it go up a mountain, though? That remains to be seen.
I will admit Neptronix bought the BBS02 while having a MAC, because he moved to a very hilly area. From reading his thread, the jury is still out on whether he likes it more than his MAC, though.
I'm thinking about doing a 24-incher for the rear no matter what I end up with, but that too adds extra complexity, due to rarity of parts. This is where the BBS02 would make life easier. If you buy and lace up a special rim for a hub motor, you're basically stuck with it. Harder to experiment. I could get it on a 24-inch rim from EM3EV, and see if it's fast enough, and handles okay.. If so, commit to a nice wide 24-inch rim, as 24 is only offered by EM3EV in 24mm. If handling is weird or I prefer more speed, I could switch to 26. :|

 

[SprocketLocket]

IMPORTANT DEVELOPMENT...

EM3EV is now considering making a MAC with a wider axle, for fatter-framed bikes!!!

Here is most of the message I received from Paul:

- - - -
The Mac axle is 205mm long, not more.
I have been considering getting a run of some custom axles built to make the
Mac work on Fat Bike Frames. What would be the ideal starting place for the
axle width? If I can get that info, we will try to get something designed
around that and to make it work with the motor, disc and freewheel. Customs
parts are not going to happen overnight, but it shouldn't take so long
either, I can get a custom axle produced.
If I can get a consensus of what is actually required, we are 1 step closer
to offering the Mac for fat Bike installs.
- - - -

Lutefisk, you've got a Moonlander. I don't think you can get any bigger than that. What's your rear dropout size, and also what's the distance between outer sides of the dropouts (IOW, what's the total thickness of the metal at the dropout)?

Paul's entertaining blank-slate suggestions. So what do we want as axle width?
It would be nice if it were wide enough to suit most everybody....

 

[dogman dan]

You can make a front motor out of a rear motor right now, to fit a 135 mm front fork.

But hell yeah a rear mac made to fit fat bikes would be sweet! Do it Paul! We need it. 12t would be the winding I'd want for a fat bike, but you know us yanks. We'd want it in 8t

The one thing that keeps returning to turn me off the bb motor, is being locked into the sprocket size they give you. For some, it would be great to have 15 mph the max speed, and have ability to crawl up hills at 3 mph. Pedicab for example.

This could be fixed, if somebody made abnormally large size freewheels. But it seems to me you should be able to bolt on the sprocket size of your choice to the bafang.

I've not yet touched one, can anybody say if they have a removable crank? Or removable sprocket? If you just put a regular small crank on, you'd have the pedals turn at all times right? But for a pedicab, this could be lived with I suppose.

In the end though, one thing I know for sure sprocketlocket, you need to ride a good FS bike before you decide they are not for you. If you weigh too much for the suspension, then you will also need a more powerful mid drive than the bafang. But I will always recommend a FS bike for those wanting to ride rough surfaces, it's just too nice once you get into a quality one.

Cheap wallmart bike suspension would need a shock upgrade and new forks to be Ok.

 

[lutefisk]

Lutefisk, you've got a Moonlander. I don't think you can get any bigger than that. What's your rear dropout size, and also what's the distance between outer sides of the dropouts (IOW, what's the total thickness of the metal at the dropout)?

The Moonlander is kind of a funny animal. Indeed, it runs the widest tires currently available, but it does so using a 135mm drop, and some seriously offset rear stays to preserve the chainline. If you look at the back of the bike, it looks like it's falling over. The rear wheel is also laced offset, to push the cassette out far enough to clear the tire. The dropouts are 7mm, so overall width is 149mm.

 

[lutefisk]

Well, EM3EV sells only 2 motors: MAC and the BBS02. That tells me something right there. So, the BBS02 is #2 for me right now. I keep going back and forth. I just don't think it would be as pleasant of an experience... This is just for pleasure, not a commute, which affects my choices. Using the gears is a mixed blessing. First, yeah I wouldn't be able to do this with a fatbike at all. Then, I'd have to be shifting gears all the time. See, I do a lot of stopping "to smell the roses". Think sightseeing. That's a lot of gear shifting and distraction while I want to focus on the experience (not sure, but that's what I'm thinking). On a commuter, that extra control is probably desirable, and you're already focused.
BBS02 is only medium power, so reliant on gear selection.

Yeah, there is a fair amount of shifting gears. In lower power modes, it's just like riding a normal bike. In higher power, you do have to pay some attention (15+mph).

Mostly though, I think current mid-drive solutions, and the BBS02 specifically, are works in progress, whereas the MAC, especially from EM3EV, is strongly refined. I expect the BBS02 to be obsoleted quickly. Following Neptronix's experience, the built-in controller seems to be crap, it needs serious tweaking right out of the box (I don't fear the programming whatsoever, just a statement on factory quality), and there are other issues I'll leave for those threads. I am fascinated by its quiet-ness, the freedom to change wheels, and improved hill climbing ability. I find I just don't "want" it enough. I'm sure if I could ride each, I'd know right away, but barring that, sometimes you just have to make the best decision you can, and I find even with research, I often am wrong. That's demoralizing to hear you kept running into brick walls w/your Moonlander. Just sucks

I think the BBS02 is actually quite refined, especially on the hardware side. The quality is really surprisingly high, with only a few knocks, like the cheesy brake levers and much-maligned throttle. On my bike though, the brake levers actually work surprisingly well, and haven't had any issues with the throttle so far (knock on wood). The programming is IMHO what's holding it back. But what was a relatively unrefined system out-of-the-box became a shockingly impressive ride with some relatively simple programming tweaks.

Not converting the Moonlander was more of a self-imposed decision for me. I ran into enough obstacles to convince myself to leave it alone. That said, I learned a while back that electriccycles.com was working on a 100mm BB for the BB02, which was supposedly available to purchase late September, but haven't followed up.

Some clarifications, lutefisk: I never mentioned rewiring the MAC. 20-25mph is the fastest I think I'd "ever" want to go under motor power, and then only in ideal conditions (no one else on the road, good surface, feeling safe, or emergency). On unpaved roads, and just commonly anyway, I'd probably be doing only 8-13mph. I'm not in a hurry to get anywhere. I just don't want the damned bike bogging down on steep hills without momentum (is that too much to ask? It seems so). Golf ball sized concrete stones are not common, but they are around. Most of them rocks are under an inch. Still, dangerous and not fun. Safety is my first priority. Then fun. Leisure fun, not sport. Hence how the fat bike fits... I think. (Never having ridden one). Would you agree on that?

I really have no interest in a rear suspension, yet. I've done a ton of (mostly road) riding in my youth, and never yearned for a rear suspension. I did yearn for a front suspension before they even existed, though. BikesDirect is going to be releasing a somewhat cheaper fat bike with front suspension in coming months (no price announced). I might hold off till then. I've seen Neptronix and WesNewell talk about how how much of an upgrade they thought rear suspension was.. I respect them, but for me, I'm not seeing it. I'm not sure what a hub motor actually does to the ride, though? MAC is light, only about 8 pounds IIRC, about the same as a light DD, I think. What rear suspension does to the available battery space and overall complexity doesn't help either. At this point, I'd still take wider tires over a rear suspension. I could always get a suspension seat post, though (and probably will). But a normal mountain bike with front suspension is still a consideration. I am also concerned that the front suspensions on cheap mountain bikes will basically be crap.

Before building my BBS02-powered Giant NRS, I had never owned a full suspension bike, and like you, frankly had no interest. I'd only messed around on friends' FS bikes, and thought they were too heavy, complicated, mushy, and pretty much stupid for a bike. And just like you, I thought a fat bike would solve the problem even better. Well let me be clear, I was totally wrong . Now this only goes for ebikes, which is to say, relatively heavy and relatively fast. Rear suspension is the BOMB on an ebike.

But here's the thing: Adding 8lbs of hubmotor to the rear wheel is NOT going to help things. With suspension, unsprung weight is the enemy of performance. But if you add the weight of the motor to the frame instead, then you can keep the unsprung weight nice and light. And ridiculously strong for the weight, thanks to how awesome bike parts are these days. That's probably the biggest reason I like the BB02 so much. It let's the suspension do it's thing, and makes the bike ride really nicely over all kinds of terrain.

All of that said, the *quality* of the suspension is not to be overlooked. Cheap shocks will result in a mushy bouncy ride. Nice shocks will give you a nice supple but well controlled ride.

Here's what you wrote that really intrigued me:

Regarding it's climbing ability--if you can stay on the bike, it can climb it.

Please, please, elaborate! Details! What have you tried so far? Care to share your and your bike's weight?
That kind of contradicts the little I've been able to find online. The closest I could get to info on this specific matter was 1Boris, who is somewhat heavy. He actually has both a MAC (10T, I think) and BBS02. He did a steep (off-road) hill test, and actually said that both motors eventually stalled, but the MAC won (went farther before stalling, and more confidently). That did it for me. I almost want to pay him a tip! So then, someone chimed in and told him he had the wrong front sprocket size or something, that he needed a smaller one. Whatever. I haven't even seen such a thing for sale? From what I know, the BBS02 comes with a replacement crank assembly, including front sprocket (or whatever it's called), and that's it?
A separate video I saw was a brief, poorly made video by one of the pro outfitters (hi-powercycles, I think), of 2 bikes going up a steep but only ~5-foot long incline, but from almost a standstill. Their BBS02 model "won", but clearly could not have kept up at that incline--it was nearly stalled at the top. By comparison, their Direct Drive model at 2000 watts (with normal wheels) was hopeless without momentum/RPM. Disappointing on both accounts.

Okay, so I live in Minnesota, so there aren't really many steep things around here. But I grew up in California so I know what steep on a MTB looks like Here's how it goes: Let's say there's a trail that's steep enough to just baaaarely make it up using a normal MTB. Well, using my Moonlander, it's usually a cakewalk. Now let's say there's a trail that's steep enough to just baaaarely make it up using the Moonlander. With the BBS02 powered NRS, it's pretty much a cakewalk. Reason being, I can stay in the saddle longer, maintain power and speed, and just cruise up. With unpowered bikes, when it gets steep enough, you have to stand up at some point, and that's usually when it all falls apart.

The BBS02 comes with with a bottom bracket that is attached from the factory to the left-side crankarm and motor assembly. The front chainring is 48t, and replaces your existing crankset/bottom bracket. The front derailleur is not used, so most bikes end up as 7-10 speeds. In the lowest gear, there is a bit of an issue with the chainline from the chainring to the biggest sprocket, which is the gearing you'd use for the steepest climbs. If you've ridden a MTB, it's basically the gearing you'd get on the biggest chainring and the biggest sprocket, with a similar chainline, but without a front derailleur to hold the chain in place. I've had my chain fall off the chainring a couple times. Is it a drag when it happens? Well, yeah, but you just put the chain back on. Is it a showstopper of any sort? Nah, not for me.

The way I see it, if you're limiting a competition to the same amount of current, the BBS02 at 750 watts will win. But that's not how life works. The MAC can use much more wattage... not as much as DD, but a lot. So while it's less efficient during those times, for shorter distances at least, it also might be able to do things a BBS02 can't--I THINK (I don't know). Also, the belief that a BBS02 can't overheat or never gets hot, and can climb mountains "all day long" seems mythical too. I see the MAC as kind of a compromise between DD and mid-drive, all of which are appealing to me for differing reasons. My biggest concern for the MAC, outside axle size, is actually noise, believe it or not. I KNOW it can more than suit my local 'sightseeing'. Can it go up a mountain, though? That remains to be seen.

Okay, so here's the deal with the 750W rating on the BBS02. It's basically just a number. The limit is set by the hardware, and currently, the "750W" hardware appears to be able to support 22-25A at up to 60V. That's 1300-1500W. I run my setup at 58V, and have software-limited my current to 20A, so that's a theoretical max of 1,160W, which my watt-meter on the bike confirms.

Using the most of that 1,160W to climb hills with the BBS02 requires a simple trick. With my setup, it takes at least 1/2 crank revolution to startup the motor. So instead, I get use the thumb throttle to gently start the motor until the pedelec kicks in. Works great on hills and on intersections, especially if I'm in the wrong gear. At low assistance (250-500W), I can climb hills all day long. At at max assistance, a few minutes and the motor begins to heat up. I've never pushed it to shutdown, but it does supposedly have high-temp protection circuits.

So, can it climb steep stuff? No question. Can it climb a mountain? Probably, but only if you use lower power levels. Always a trade-off.

I will admit Neptronix bought the BBS02 while having a MAC, because he moved to a very hilly area. From reading his thread, the jury is still out on whether he likes it more than his MAC, though.
I'm thinking about doing a 24-incher for the rear no matter what I end up with, but that too adds extra complexity, due to rarity of parts. This is where the BBS02 would make life easier. If you buy and lace up a special rim for a hub motor, you're basically stuck with it. Harder to experiment. I could get it on a 24-inch rim from EM3EV, and see if it's fast enough, and handles okay.. If so, commit to a nice wide 24-inch rim, as 24 is only offered by EM3EV in 24mm. If handling is weird or I prefer more speed, I could switch to 26. :|

I'm working on a build thread for my bike, but how's this for simple: the BBS02 was installed from box to bike in about an hour. No extra trips to the hardware store. A bit of time spent online figuring out how everything went together, thanks to the complete lack of instructions. It looks like a bike. It pretty much handles like a bike. It's brought forth HUGE smiles from the two people I've let ride it so far.

I'm seriously reconsidering putting a BBS02 on the Moonlander if the 100mm bottom bracket is really available.

 

[SprocketLocket]

Great conversation. I'm sure this will be helpful to others.

The front chainring is 48t, and replaces your existing crankset/bottom bracket. The front derailleur is not used, so most bikes end up as 7-10 speeds. In the lowest gear, there is a bit of an issue with the chainline from the chainring to the biggest sprocket, which is the gearing you'd use for the steepest climbs. If you've ridden a MTB, it's basically the gearing you'd get on the biggest chainring and the biggest sprocket, with a similar chainline, but without a front derailleur to hold the chain in place.

This brings up an important point for someone wishing to take a "normal" mountain bike, and use tires and rims which as fat as possible--which is an option I'm still strongly considering, and "will" if I buy a "normal" MTB, at least with tire size. How wide are your tires? I'm realizing that wider-than-normal rims/tires could cause a problem with the chain getting to the lowest gear. If I were able to fit 80mm rims and/or 3-inch tires, that could seriously interfere with both the Bafang - and me - from using the lowest gears, which would, honestly, defeat the purpose. I'm interested in what issue you specifically meant when you said, "In the lowest gear, there is a bit of an issue with the chainline from the chainring to the biggest sprocket". What is the actual problem?

It's starting to sound to me like the included chainring is also too big for a lot of riders (geared for speed, not climbing; I'm more interesting in pedaling if necessary for climbs, and, if necessary, only fake pedaling at speed).

I read carefully everything you wrote, some parts multiple times. I think there might be a significant difference in our riding styles, which could change what is best for me. You like to go fast, I do not. Speed (I think) is where the rear suspensions really help. If I encounter big bumps, I have always stood up and let the bike pivot on my pedals. The revolution with the motor would be that hopefully I wouldn't have to pedal during that time anymore. You seem to like and want to pedal; I am done with pedaling. I would not miss it if I never cranked another pedal in my whole life. I like riding, but dislike pedaling, which is why I haven't biked in... I won't say how long. I WANT to be able to pedal just for control, say at extremely low speeds (like turning around), but I don't even want PAS, and the first thing I would do would be to disconnect PAS, which I hear results in a revelation for throttle control anyway. (BTW, does getting in there void any warranty?) If I want to pedal, I'll do that in conjunction with Throttle, like I do now on my cheapie. You do a lot of offroading; I do a lot of paved and crushed concrete, with occasional offroading. But I might try a mountain or two on a trip--still slowly; even slower, actually. Great points on the peak power and programmability, great analysis. I think you do more challenging environments overall and more commonly, and like to go fast. I'm really seeing how well the BBS02 suits you, in a way I didn't realize before your writing. But my desire for wide tires even on a normal mountain bike sounds like it woul further complicates the BBS02, as it's totally reliant on a properly-working chain and crank. With a MAC on a fat bike, I could probably get away with an offset freewheel hopefully not hurting the MAC's sidewall, by not doing a lot of aggressive pedaling (which is the plan!). With a BBS02 in a normal MTB, I'm stuck with a cassette left where it is, with (I'm thinking) a fatter tire interfering with the lowest gears??

I was looking on BD to see what FS bikes I could find in my cheap price range. Link below seemed (to me) to be the most reasonable in this price area. I like that it still has a reasonable rectangle to try to put a battery pack on the downtube, although I think the bar configuration might preclude use of a frame bag? Perhaps a frame bag could be modded to fit it. I would probably use a box-within-a-box system, with foam between them, to protect the batteries from movements of the rear suspension. I wonder what the widest rims are that it would support. Also, for bottom bracket, it just says "Sealed Cartridge Unit, square taper", which isn't helpful to me. I barely even know what a bottom bracket is. How can a cylinder within another cylinder be called a bracket.
Input/opinions?
http://www.bikesdirect.com/products/gravity/fsx_3.htm

Lutefisk and dogman agree that dual suspension is great, with the proviso "if it's good quality". So I want to know, what kind of price range are we talking about, to get one that would be 'worth it'?

 

[lutefisk]

Interesting conversation indeed.

You may be right that we have very different riding styles. When I'm on a bike (electric or no), I do very much like to pedal--it's how I've always ridden bikes, and I feel like I have more control. I also own a Vespa and full size motorcycle, and those are obviously throttle-only, and I ride them VERY differently than I ride my bikes. I do not enjoy riding the BBS02-equipped Giant on throttle only, though that is a perfectly viable way to ride the bike.

Regarding how "normal" the Giant is, I run 2.25" knobbies at about 40psi. The frame will not clear any larger tire size, so I couldn't run 3" tires even if I wanted to. The issue with the chainline on the BBS02 doesn't have to do with interference from the tires. If your frame is designed to clear 3" tires, then chain interference with the tire shouldn't be an issue. The problem I was describing regarding the chainline is different--I'm referring to the angle from the front chainring to the largest rear cog, which so large that it causes the chain to fall off the chainring in some situations. And unfortunately, 48t is pretty much the smallest chainring you can run due to the design of the reduction gearing. As far as the gearing is concerned, it is too high for a regular mountain bike trying to climb hills. But with the addition of electric power, the gearing actually makes a lot more sense, and is more than enough virtually anything you'd be able to climb. I.e., the limiting factor is less the bike's gearing/power, and more your ability to stay on the damn thing when it gets steep enough.

I'm going to digress a bit here to talk about the differences between mid-drive and hub-drive, as far as gearing is concerned. On a hub-drive system, the motor doesn't benefit from the bikes gearing whatsoever. The only way you can affect gearing is by changing your rim diameter (and of course the reduction from the Mac's planetary gears). Most electric motors are more efficient the faster they're spinning (or at least, the closer they are to their "ideal" RPMS, which is almost never 0). When you ride a hub-drive up a hill, the wheel is usually not spinning very fast, which means that the motor is not operating in it's most efficient range.

On a mid-drive, the electric motor can benefit from the bicycle's gearing, so that it is spending more of its time operating near peak efficiency, thus extending your run times and reducing heat buildup. This is why mid-drives use so much less power when you're trying to climb hills. Same applies when you're just tooling around at slow speeds. With a hub-drive, you're actually running the motor very hard at slow speeds. With a mid-drive, you can gear down and run the motor very efficiently at the same slow speeds This is particularly true if you're running throttle-only, and not using the cranks to assist the motor at low speeds.

All the stuff I'm talking about above covers most of the reasons why I went mid-drive instead of hub-drive. Choosing to do a mid-drive pretty much eliminated fat-tire bikes from consideration, since none of the mid-drives could be fitted to fat-tire bikes at the time. As of yesterday I believe, that has changed, with the announcement of the BBS02 for 100mm bottom brakets by California E-bikes (check the mid-drive forum, there's lots of info about the announcement). Also, I believe lightningrod has just started shipping some of his modified GNG drives to fit on 100mm bottom brackets.

I also just read the thread in the photos/video forum about the fella who built a 45+mph ebike out of his Moonlander, using a hubdrive. Personally, I think a 45mph fat-tire bike is one of the most dangerous bikes I can imagine (imagine hitting a significant bump at those speeds, with those gigantic tires and no damping...), but it also sounds like a hoot. There's also a fella how built a 2WD fat-tire bike using hubmotors. If I had to guess, both of those bikes cost $4K+ to build.

California E-bikes sells a couple different models of fat-tire bikes. And nycebikes.com offers fully built Bion-X powered Moonlanders. Those bikes are all serious money ($3,500+++) Why so expensive? Well, because fat-tire bikes are expensive to begin with. The Wal-Mart Mongoose doesn't count. Tires alone for a fat-tire bike can be $100-$200! Things are starting to get much cheaper, with many more options to choose from, but for the moment, if you wanna do stuff with fat-tire bikes, I think it will cost a lot. Unfortunately, the same is true for full-suspension bikes, at least if you're buying new. The cheaper models on BD have pretty crappy suspension (coil-sprung no-name shocks). The bikes that have decent suspension are the ones that start around $1500 (like this one: http://www.bikesdirect.com/products/motobecane/275-650b-bikes/fantom_275-comp-6by6.htm). I know, it sucks. The big caveat though, is that if you're willing to buy used, then you stand a decent chance of finding a really high quality full suspension bike for several hundred bucks. That's because they've been around for over a decade, and even the older stuff, if it was cared for and good quality to begin with, is still really nice equipment. The same is not true for fat bikes, because they've really only been around a few years.

Obviously price is a huge factor with this stuff. But with bikes, like everything else, you get what you pay for. The $429.99 bike that you linked is a great example. There's probably never been another time in history where you could get SO MUCH bike for so little money. If you only put a few hundred miles a year on that kind of bike, you'd probably never understand why anybody would pay more. But if you start doing a few hundred miles a month, it will become very obvious why it was so inexpensive. And if you start adding extra weight, and start pushing double or triple the amount of power that bikes are designed for through that kind of bike, then I predict that stuff is going to start wearing out and breaking very quickly.