New 29" MTB build

Hi, I am looking to build an ebike for commuting. I am looking to use a GT karakoram sport 29 " MTB, its a 9 speed with front suspension and hydro brakes. One of the reasons I chose the 29 size and this model in particular is that it provided a lot of gear inches (bike specs are here: http://mountain-bikes.gearsuite.com/l/9012/2015-GT-Karakoram-Sport) and suits my height. I want the bike to be as much of a bike as possible, meaning I'd like it to ride well just on leg power, and also when using the assist, which I plan to most the time. I'd like to be able to travel between 40 to 45 kph on average while being able to put a comfortable amount of power when pedaling. I'm looking to add 2.35" schwalbe big apples for greater stability on pot holed roads and also increase the top pedaling speed due the tires' larger circumference. My area is mostly flat and would like a range of about 100 km while pedaling. Rider weight is 200 lbs.

I would prefer a light and stealthy rear hub, however I think any small rear hub motor will not have enough power, so I was looking at the 1000 watt leaf motor kit for 29” (http://www.leafbike.com/products/diy-bike-conversion-kit/29-inch-electric-hub-motor-kit/newest-29-inch-48v-1000w-rear-hub-motor-bike-conversion-kit-1014.html) with a 48v 20 ah battery (for example one from luna cycle).

I was also considering the cycle analyst 3.0 so that I can use a bottom bracket torque sensor for the pedal assist, do you believe this will improve the ride quality / pedalling feel vs a cadence sensor ? Will the cycle analyst and torque sensor work with leaf motor kit (I'm noob so I'm not sure exactly how all these things hook up) ? I'm also somewhat hesitant to get the cycle analyst as I'd like to lock up my bike, and a large bike computer seems easy to steal and draws more attention. It'll get enough attention with the huge hub motor at the back already. Not a big bike theft area though...

Since the bike is 9 speed, I'd probably want to get a 9 speed free wheel (will it fit with the leaf motor?) so that I can use the bikes' existing gear set up without any little/modifications.

Please let me know your thoughts, suggestions and answers to my situation outlined above.

Thank you for attention

Welcome! I'm a big fan of 29ers as well and instead of a hub motor, would you consider a mid-drive (BBSHD or BBS02)? The reason I say this is because of the integrated pedal assist that comes with the Bafangs vs the addon bits for the other motors. I ran a 9 speed on my old hub motor, however I kept on destroying the DNP freewheels which might be an issue if you're after commute reliability. I switched from a 2.2kw MAC 10T hub to a Bafang BBS02 750 mid-drive and havent been happier. It's not as quick off the line ( My MAC10T kept on lifting the front wheel on take off ) but the central weight distribution makes it feel more nimble like a normal bike. I also bent the rim of my hub motor and getting it relaced is a pain in the ass.

In regards to the big apple, I used to run one in the rear (awesome commute tire... that just doesnt puncture... ) but with a motor, it doesnt really matter if it's a slick or studded since you have assist anyway. The big apple is great for road, but I found myself crossing random fields and parks where it would be slippery as shit on wet grass.... I went back to a Rapid Rob for a cheap all terrain tire and find that if it's pumped up to 45 psi it's fine for most conditions (road and park). If I dedicate a day to trail riding, I just let some air out which aids grip. Lycra's get annoyed by the sound of MTB tires chasing them down. =)

Thanks for the info about the free wheel, I didnt know the DD rear hub motor like the leaf would destroy the DNP freewheel regularly. Yes I have considered those mid drives but after reading numerous discussions on this forum I came away with impression DD rear hubs would be the simplest , most reliable application for my situation. I do like the central weight distribution with the mid drives but it seems that advantages of the mid drives would be more significant in other applications (such as trail riding) besides mine. The leaf motor seems to also be quite powerful and very efficient and being DD , quiet-ish (I like quiet and efficient and low maintenance). It supposedly free wheels really well. The review of the motor seems to be quite favourable here ( https://endless-sphere.com/forums/viewtopic.php?f=30&t=66489) Although I am somewhat convinced about using a DD rear hub such as the leaf motor, I do welcome any info with regards to potential issues in going this route as you have brought up. Thank you!

With regards to the tires, the prospect of annoying Lycras is appealing haha. I test drove a granny style ebike last summer and the ire I received was confounding. They would try to beat me and say things to me as they passed (even after I kindly inviting them to draft me). However my motor doesn't get tired like humans and I would always pass them shortly afterwards as it is hard to maintain 35km/hr for most. Conversely, lycras never try to sprint by me on my road bike, nor do they say things as they pass (besides "passing!").

Would the 48-50 V 20ah battery be sufficient for my wants of 100 km assisted, even with only charging to 90% and discharging to 10% , perhaps 22 or 25 ah would be better (I'm now thinking at least 22)? I know most don't really care too much about weight on an e-bike, but I'd like to carry the least in battery as possible and 1KW + of power is heavy (and $$) , even with the newest cells. Also I may be locking bike up and hopefully would like to remove the battery (and bag) and carry it.

A mid drive is many times more likely to wear out the drive train (sproket, freewheel, chain) compared to a hub motor since it uses the bikes drive train to power the bike where a hub motor doesn't. A dd hub motor will be the most reliable of all options.

wesnewell said:

A mid drive is many times more likely to wear out the drive train (sproket, freewheel, chain) compared to a hub motor since it uses the bikes drive train to power the bike where a hub motor doesn't. A dd hub motor will be the most reliable of all options.

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Yes that is the impression I got from reading this forum.

I think Wesnewell is on the money for most things, but as with everything, it depends on the user.

Do you like pedalling hard or do you just want to run on the motor for most of the trip?

Lakebod said:

Thanks for the info about the free wheel, I didnt know the DD rear hub motor like the leaf would destroy the DNP freewheel regularly.

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The freewheel doesn't know what kind of hub it's attached to. And the hub motor can't transmit any power through the freewheel. The DNP freewheel is just a steaming pile of crap, that's all. Born to break.

Yes, a direct drive hub is probably the most reliable e-conversion you can use... but not if you want 9 speed. My advice? Convert to 7-speed and enjoy better function, better durability, and much cheaper replacement parts when you do need to replace them.

At my shop, a 7-speed chain costs $12, freewheel or cassette costs $15, and shifter costs $15-22. 9-speed chain costs $23, cassette costs $42, shifter costs $28 up. And the 7-speed stuff really does last longer and work better with less maintenance.

Chalo said:

The DNP freewheel is just a steaming pile of crap, that's all. Born to break.

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Just an FYI - I stripped 2 of my 9 speed DNP freewheels in 10 months of all weather commuting before I taco'ed the rim.

But yes... Option 2 is to lose your nice 9 speed gear and go to 7 speed... Or jump to a mid-drive since no one uses the granny chainrings during commute anyway.

Raged said:

Or jump to a mid-drive since no one uses the granny chainrings during commute anyway.

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Well, yes... unless they're limping around with an unpowered e-bike that provides several times as much resistance as a normal bike.

Road triple cranks (typically 52-42-30) are a better match to e-bike situations than MTB triple cranks which are usually 42-32-24.

Chalo said:

Raged said:

Or jump to a mid-drive since no one uses the granny chainrings during commute anyway.

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Well, yes... unless they're limping around with an unpowered e-bike that provides several times as much resistance as a normal bike.

Road triple cranks (typically 52-42-30) are a better match to e-bike situations than MTB triple cranks which are usually 42-32-24.

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My cyclocross runs a MTB 11-34T 9 speed rear (mega-range) to click through most scenario's (5%-8% gradients are fine for me without power) and a 48t chainring up front on the BBS02. Referring to the drive/speed calculations ( http://sheldonbrown.com/gear-calc.html ) Theoretical top speed at 90rpm for this 1 x 9 speed setup is 52km/h... which is fast enough to be fun, but still stay under the radar as a bike.

Raged said:

I think Wesnewell is on the money for most things, but as with everything, it depends on the user.

Do you like pedaling hard or do you just want to run on the motor for most of the trip?

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I'll try to qualify how I'd like to peddle as best as I can. I'd like to peddle at a *leisurely* pace , by that I mean similar to pedaling my 27.7 lb road bike at 23kph on flats, I'm 200 lb. I'd like to pedal most if not all the time (like I'm biking ) Am I correct in assuming that a motor like a MAC 10T will have less pedaling resistance when pedaling (either in PAS mode or just leg power) vs a 0.35mm lamination (this smaller lamination make sit easier?) direct drive like the leaf 1000w or MXUS V2 1000 w?

when the motor is on, it makes not one bit of difference what kind of motor it, you will pedal just as easy regardless.
When the motor is off, it will make a difference. T Freewheel gear motors will disengage the motor and let you pedal as a normal bike with no drag. Direct drive motors will drag, a little. The lamination thicknesses have little to do with it. The magnet strength, pole count, stator width, copper fill, and idle resistance of the MOSFETS does.
But people put way to much emphasis on Direct Drive Drag. You may actually notice it, but it isn't much, even on the absolute worst motors. If you're going to do long distances with no power, get a geared drive, otherwise, don't worry about it.

With regards to the freewheel/cassette, why will a 7 speed freewheel wear out less than the 9 speed 11T DNP, is it because I can get a higher quality (different brand than DNP) freewheel/cassette? I heard talk of 9 speed sunrace (http://www.amazon.com/SunRace-9-speed-11-32t-Freewheel/dp/B00ABHFZO8), are these any better (perform well, last long) than the 9 speed DNP freewheel? Also, I suppose I can fit cassettes on DD hubs like the leaf 1000w or mxus v2 1000w? If so , 7 speed 11T is the max speed (I cant keep my 9 speed 11T cassette)?

I read this thread: https://endless-sphere.com/forums/viewtopic.php?f=2&t=25424&start=75, have things changed since then (years old thread)? I see that a road cranks with large chain rings (52,53t) are recommended so that you can use the "better" 13,14T shimano freewheels, however would there be fitment issues with my 29" bike? I read up on this option a little while ago on some forums , and some mentioned that there would be issues, I think it was clearance issues due to the chainstays sticking out more (to accomodate the thicker MTB tire), and the larger chainring's larger diameter (I'm not 100% that was the issue, it was a while ago). Maybe these issues wouldn't exist cause its a 29 er vs a traditional 26 MTB?

Lakebod said:

With regards to the freewheel/cassette, why will a 7 speed freewheel wear out less than the 9 speed 11T DNP, is it because I can get a higher quality (different brand than DNP) freewheel/cassette? I heard talk of 9 speed sunrace (http://www.amazon.com/SunRace-9-speed-11-32t-Freewheel/dp/B00ABHFZO8), are these any better (perform well, last long) than the 9 speed DNP freewheel? Also, I suppose I can fit cassettes on DD hubs like the leaf 1000w or mxus v2 1000w? If so , 7 speed 11T is the max speed (I cant keep my 9 speed 11T cassette)?

I read this thread: https://endless-sphere.com/forums/viewtopic.php?f=2&t=25424&start=75, have things changed since then (years old thread)? I see that a road cranks with large chain rings (52,53t) are recommended so that you can use the "better" 13,14T shimano freewheels, however would there be fitment issues with my 29" bike? I read up on this option a little while ago on some forums , and some mentioned that there would be issues, I think it was clearance issues due to the chainstays sticking out more (to accomodate the thicker MTB tire), and the larger chainring's larger diameter (I'm not 100% that was the issue, it was a while ago). Maybe these issues wouldn't exist cause its a 29 er vs a traditional 26 MTB?

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7 Speed freewheels are thicker because you're putting less gears (hence the gears can be thicker) in the same available space. They're also usually made out of steel which is stronger as weight is never really an issue with the lower end of Shimano spectrum. I actually eventually went with a sunrace freewheel in between my DNP failures as a stop-gap. I never saw the 11t Sunrace though (maybe wasnt available at the time) so I only had the 13t high gear one which seemed pretty good quality wise, but didnt have the right gear ratio's for an ebike =( . At least it didnt strip gears. Maybe that 9Speed 11t sunrace would be ok although it's an extra US$50... and things are starting to add up.

Also know that since the indexing on 7 speeds is different to a 9 speed, so you will need to get a 7 speed shifter as well if you decide to go down that route (deraileur should be ok across both items if they are for MTB). As 7 speed shifters are typically on cheaper bikes, I couldnt find one that felt as slick as my 9 speed (rapid fire trigger shifters). So I decided to keep my 9 speed setup.

In regards to road cranks on a 29er... No they dont fit due to clearance issues. Either the chainring hits the frame or the chain doesnt clear the fat tires. You need to stick to MTB components. I went down this path as well and finding a 50t chainring for a 4 bolt MTB crank is difficult unless you try to get the whole crankset (which is $200+). The cheap and easy way is to just replace the big ring with a 48T ( under $30 ).

Yeah... I've spent a bit of cash looking at shit that works vs shit that doesnt work =(.