# Help spec my DIY full susp conversions!!!



## money d (Mar 11, 2006)

I've procured two full susp mt bikes on which to perform a DIY ebike conversion, one for me one for the wife. 
Mine is a 2014 Spec Stumpjumper FSR Elite 29er XL - I'm 6'5 270lbs. I've mtb'ed since the days of DaleRider here on MTBR. I was thinking mid-drive BBSHD. I'd hate to build this and be unhappy with the power. My concerns are which battery and where to put it? I'm concerned about the motor hanging a little low, but I'm getting older and won't be jumping logs much.
The wife's is a 2006 C'dale Prophet. The wife is 5'7 and skinny, but doesn't MTB much (hence getting the diy ebike to foster passion?) I was thinking rear hub (Lefty fork) 500 watts since she is light and it would be cheaper. But I keep reading that rear hub conversions are tricky/difficult and wonder if I should just get a mid-drive. Location of the battery is another problem, as the shock of the prophet takes up most of the triangle. Rear rack sounds like the best idea here.

My bike will be used for actual mt biking as well as fun with the family/easy rides. The wife's will mostly be easy rides, with some logging roads thrown in.

Thoughts? BBSHD with a 48 or 52v 20ah battery for me? Rear hub or mid-drive for the wife? Motor and battery spec recommendations?

Thanks in advance.


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## minimusprime (May 26, 2009)

you aren't going to get much assistance from this group. You're better off researching and asking these questions on endless-sphere.com, luna's forum or electricbike.com. I've built a few diy conversions using the bbshd and also the tsdz2. The stumpjumper is a particularly poor frame to base a diy conversion on. It uses a pressfit bottom bracket, has a downtube that isn't sloped particularly well for motor fitment. Battery placement will be particularly challenging... the easiest solution would be to use several small batteries with samsung 3500mah cells so that you can change them as you go. Otherwise you're going to be making a custom battery box. Trust me when I say that you are far better off selling that bike and starting over then you are proceeding with it... The bottom bracket conversion sleeve on the frame is expensive and a pita, and the spindle extension with the bbshd conversion is expensive, and almost guarenteed to fail often at your riding weight. To be honest, at your weight/height I can't recommend any of them as there is a pretty high risk of spindle/square tape crank failure with all of them. It would be highly advised to buy a pre-built e-bike as there are going to be rather constant issues with parts failures with that sort of load.

For your wife, the canondale profit is a decent choice for a conversion, whether it's hub or mid drive. Single pivot frames (particularly pre 2008) are the easiest to convert as you can brace off the seat tube to brace the motor when doing a mid drive conversion. In this case, I'd suggest a hub drive and again, bottle cage format samsung 3500ah cells.

My overall thoughts are that from my experience, and the collected general rule of thumb for DIY ebike conversions.... you're going about this backwards. Pick the drive/setup that you want to use and find the best list of bikes that drive unit is possible on. There is a very, very steep learning curve to all of this and if you are an actual mountain biker instead of an electrical engineering hobbist/nerd, then I cannot suggest enough that you should not go the DIY route.

For context, I am an electronics nerd that is primarily a mountain biker. I've done these conversion, still own one myself which is a chameleon mk7 hard tail tsdz2 (see below links for my current build) Even my build, which was planned down to the last detail took a ton of work and about $1,500 to do the actual conversion and conversion specific bike parts. Even this bike is compromised and has a spindle that will eventually fail at my riding weight (~180lbs) and that is true for all of the conversions. You have to ride them gingerly, they are going to have overheating issues, you need to know everything there is to know about the motors, frame, clearances etc and then there will still be surprises. It was a fun project, but it is still expensive (this one would easily come to 3k when you factor in the parts that are on it) and it's heavily compromised to a store bought e-bike. As an avid mountain biker, it is not anywhere near as robust and reliable as a pre-built ebike. It'll work fine for your wife (and does work fine for mine) but don't go into it expecting significant parts failures with the energy you'll be putting into the bike and with significant build headaches.



http://imgur.com/BhfAFVu




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http://imgur.com/U8LyPoa


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## DtEW (Jun 14, 2004)

An addendum to *mimimusprime*'s sentiment:

At the OP's weight, he needs to do research if an off-the-shelf eMTB can even take his weight.

For example, an aluminum-framed Specialized Levo/Levo SL has a frame capacity of 300lbs. But a carbon-framed version of the same only has a frame capacity of 240lbs. But this is not the extent of the issue.

The Fox DPS EVOL shocks that come with many Levos are only rated up to 325lbs of pressure. But you might not be able to get the correct amount of sag at 270lbs even at maximum pressure.

This is known for the Specialized Levos. YMMV with other brands/models... but don't just assume that dimensional fit is the only issue. It is highly likely that you are already exceeding the safety/proper-functioning limits of the 2014 Spec Stumpjumper FSR Elite 29er XL.


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## matt4x4 (Dec 21, 2013)

If the TSDZ2 doesnt break, go for the BBSHD or Cyclone but most people dont require or need a mid drive bike whether its DIY or store bought. Maybe in San Fransisco, or very low power then the gearing helps out a lot.

Major priority should be given to the triangle of the bike for battery placement, or go Enduro frame.


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