Cannondale Jekyll Full Suspension with BMC build and review

I built up a Cannondale Jekyll with a BMC V2S some months ago. Here is a build log and riding impressions.

Some background. I have been riding a Specialized Stumpjumper with a 9C@72V past year and a half. While the Stumpjumper has admirable handling and feel in its original state, adding the weight of the 9C and 12kg of batteries made handling a dud.

Therefore, goals for this build were thus both a stiffer frame and less added weight. Stiffness comes from tubing diametre on a bike frame, so a Cannondale oversized aluminium frame was a natural choice. Suspension flex was another culprit on the Stumpjumper. The Cannondale Jekyll is built according to the theme less is better. One big diametre stanchion in the lefty fork is both stiffer and lighter than the two stanchions in a conventional fork. One beefy joint in the mono-pivot rear suspension is better than the numerous joints in most rear suspensions. The eBike components I picked are the popular BMC V2S and Clyte 35A analog controller. The BMC is a bit lighter than the 9C, but the biggest imrovement is a significantly better torque and efficiency at high loads and low speeds (that is going up hills and/or pulling my kid in a trailer.

The controller is mounted to the seatpost with metal straps fastened to the heatsink screws on the back of the controller. The battery triangle mounted. 6kg in the triangle perfectly balances the 4.5 kg of the motor in the rear. Longitutinal CG just at front tip of saddle. End result so far looks like this:
View attachment 2

Checking the axle in the dropout I found quite a bit of wiggle. To make it fit snugly I filed the dropout a bit deeper and added steel wedges to fill the gap in the original dropout. No idea why the dropout is like so. The previous Stumpjumper had forged steel dropouts. Super strong and nearly impossible to file. The aluminum in the cannondale is on the other hand quite soft.

I was concerned with the point load where the small ridge on the motor axle would contact contacts Alu dropout. Therefore I put washers on inside and outside of the axle to spread force over a bigger area of the dropout. A 5mm spacer was added to freewheel side to fit 9sp freewheel. On the brake side I mounted a torque arm to the disk brake eyelet. The black attachment is the trailer hitch for my Bell kids trailer.



I've got 16s of A123 15Ah pouches that I want to build a battery from, but haven't figured out how to solder the stubborn aluminum tabs yet.
http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=21519
For now I'm using one or two of my other batteries for 36 or 72V.

I also bought a cycle analyst direct plugin, but didn't figure out how to wire it. Once I have that wired I can give some speed and Wh/km figures.
http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=21931

In summary to be fixed is: '
Learn howto solder A123 tabs, build battery.
Learn how to connect CA direct plug-in to Clyte 35A analog controller and install.
See if I can file left hand shifters (Deore XT) to clear throttle.

Riding impressions
The Cannondale frame carries the added 10kg BMC motor and battery ok. Certainly much better than the weaker Specialized Stumpjumper frame dealt with 18kg 9C + battery. I can do relatively straight singletrack trails, but have to avoid the really challenging trails and hills. The added weight makes steering reaction much slower compared to the bare Cannondale (or any similar MTB)

I crashed pretty hard once (lost control after landing a jump). While I tore my pants, and bent the brake disc and handlebars the eBike parts survived fine.

I had to set the damping on the front and rear shocks to max, and the bike is still a bit underdamped. Bike shocks are just not made for the heavier load of ebike stuff.

I'm using the bike mostly for commuting, and it does fine in the urban jungle. I can go down stairs and curbs, but shredded tires trying to go up. Now I run Schwalbe big apples which do very well on the pavement. They obviously don't have good grip on dirt or grass though. Despite soft rubber (therefore good asphalt grip) they seem to not wear too quickly (compared to some Hutchinson high end tires, soft compound I tried before)

Now in the winter I found that the Big apples (surprisingly) have a decent grip on snow and walking paths. It is of course worse on the compressed compressed snow on the car lanes, so I have to get my studded tires on soon.

Anoter winter issues that came up one cold morning was that the 9speed freewheel does not engage. Temp was -30C and I guess the grease inside had stiffened. BMC motor worked though and after biking a bit the freewheel started working right. I have the same brand ebikes.ca 7sp freewheel on the older build, but did not have low temp issues with that one.

Overall the big full suspension Cannondale bike handles better in winter than the previous eBike. The substantial 5" shocks are good for obstacles hidden under snow.

Awesome work man. I can't wait to see some CA numbers. How fast, and range. Does it do hills well without pedaling, and from dead stop? How are the dropouts doing with only one tourqe arm. How thick is your tourqe arm?
Brian L.

RallySTX said:

Awesome work man. I can't wait to see some CA numbers. How fast, and range. Does it do hills well without pedaling, and from dead stop? How are the dropouts doing with only one tourqe arm. How thick is your tourqe arm?
Brian L.

Click to expand...

Subjectively it does significantly better than the 9C up steep hills or pushing through snow.

Cycle Analyst numbers will come when I learn how to solder the CA Direct Plugin connector to the Clyte 35A analog controller. This should be possible as many have this same Clyte controller with the CA DP connector already there. It is just that I bough a used controller without this plug.

Torque arm is this one from ebikes.ca. Seems to hold up fine with just one torque arm, and the provisions I made to prevent the axle from rocking (filled gaps, used washers etc. as above)

Winter riding update

So wife calls in a bread order with the bakery in the morning; then thinks I'm the one to get it. Edmonton was all snowed in. -20C. No problem. I step into the ski suit with the pajama still on. Have to push bike through the deep snow until I reach some barely plowed roads a bit away. Lots of abandoned ditched and bent metal on the road side. One guy still around to lament his crashed Mercedes. I decide to go on the sidewalks to not get stamped by the out-of-control drivers. Make it to bakery with just frozen fingers and toes. Worst part is fiddling with the U-lock and keys since I have to get my hands out. Way back pretty much the same condition. Battery runs out near home so have to pedal last piece. Good thing the BMC freewheels. Get back, step out of ski suit and eat.

So how does the equipment hold up?

Snow, salt and low temps has been harsh on the 9sp chain and freewheel. Freewheel is now pretty gummed up. Will try to thaw inside and get some lightweight oil into it. Others have their SRAM chains snap. Seems kind of crappy for a $50 chain! Maybe should have gone 7sp where chains are cheap and strong (e.g. KMX brand).

Rear shock is air and seals drop pressure from 200 to 100psi in a week or two. Glad I don't have air but a real spring in the front Lefty fork. Would be a pain to ride with a dead front shock (b.t.d.t. on the Stumpjumper)

Schwalbe big apples tires have surprisingly decent grip on snow despite minimal thread. Must be good rubber compound. Might not need to put on the studded tires until the freeze-thaw cycles in spring makes everything icy.

Really need some fenders/mud guards, but unsure how to mount them on the lefty fork. Also there isn't much clearance for fenders in the rear.

The once-piece ski suit works well for winter riding. Seems to breathe enough that I can workout pretty hard without getting swamped in sweat. Neoprene face mask is too restrictive for my breathing. I really need it below -15C though. Might try to replace the stamped out breathing holes with sewn-on nettling like the ladies have on their burqas.

Hi Jag,

you can't really get the CA DP to work properly with a geared motor with freewheel (it doesn't register distance travelled when the motor is freewheeling) and also the commutation frequency is too high to record speed Ion the BMC, MAC or Ezee motors (equivalent to 80 pulses per wheel revolution). Better off with a stand alone CA and you can still tie in the throttle signal to control speed and current by connecting just gnd and throttle into the controller. The single wheel magnet isn't so great for speed control IME as it tends to overshoot and then cut, but maybe with some fiddling of the settings you can get it to work well.

Good luck with the pouch cells. With enough heat you should be able to solder them. If you can't get it work, drop me a line and I can send details of the mechanical termination metho I've used. You can build the parts yourself or I could knock them up for you. I have made a document detaling the termination procedure.

cell_man said:

you can't really get the CA DP to work properly with a geared motor with freewheel (it doesn't register distance travelled when the motor is freewheeling) and also the commutation frequency is too high to record speed Ion the BMC, MAC or Ezee motors (equivalent to 80 pulses per wheel revolution). Better off with a stand alone CA and you can still tie in the throttle signal to control speed and current by connecting just gnd and throttle into the controller. The single wheel magnet isn't so great for speed control IME as it tends to overshoot and then cut, but maybe with some fiddling of the settings you can get it to work well.

Click to expand...

Anyone knows what the max frequency is for the CA counting motor pulses? I had toyed with the idea of putting another old one I have on an RC motor, but that may be a failed idea at high rpms.

The CA I bought for the Cannondale/BMC build actually has the wheel speed sensor, but the controller plug instead of the separate shunt. I wanted this for a cleaner install using the controller shunt resistance , and having CA controllable max current etc. I'm pretty sure Clyte 35A controllers sold by ebikes.ca and Ilya among others do have the CA plug and work for the BMC/Ezee. Having an older used controller I just have to figure out where to solder the plug leads to the controller PCB myself.

cell_man said:

Good luck with the pouch cells. With enough heat you should be able to solder them. If you can't get it work, drop me a line and I can send details of the mechanical termination metho I've used. You can build the parts yourself or I could knock them up for you. I have made a document detaling the termination procedure.

Click to expand...

Thanks for tips and offers. I tried varying heat (to the point of carbonizing the flux). There's probably something else missing in my technique (despite having watched every youtube alu soldering video I was pointed to or found. I'm trying to find someone local to give me a lesson. I also wanted to try different solders and fluxes. I have trouble finding local knowledgeable people to help. I called lots of local electronics stores, battery rebuilders etc, but no luck. I'm going to try the RC flying club next.

I have two reasons for wanting soldered:
1. Corrosion. With big climate variations and outdoor use I was concerned how mechanical termination would hold up. I would be interested in hearing from people having used for some time the various different terminations posted on ES. I might change my mind.

2. I had thought to build my pack as 4x 4S, so each 4S section can be isolated, and I can e.g. connect as 8s2p or 4s4p. This would be difficult to fit with mechanical termination. The 4x 4S configuration gives me more voltage options (Like charging directly from a 14.5V car alternator when I live in my VW bus). Challenges include of course the BMS. The Fechter design should work I think, but I'm not sure if the BMS I have from you can easily be split from 16 into 4x4. So I might abandon this idea anyway and just go 16s

All this reading and I only just now realized that the Jekyl has a mono front fork! 8) I am proud of your courage to ride in the snow like that. I used to do that with a 20 inch Schwinn stingray that I modified with plastic star wheels and a homemade extended front fork. I drilled holes in the solid steel stingray forks, cut a set of chrome tip aluminum forks off a bent up bike, drilled them out, slid them over the steel ones, added nuts and bolts, and had a nice chopper. I rode that bike in a blizzard on New Years Eve to get a case of beer that was two miles away. I'm still proud of that run! I love your bike man. Nice work! 8)
Brian L.

I finally got a CA installed. Also swapped a studded Kenda tire on the front, but was too lazy to take off the hub motor and the torque arms, trailer hitch etc, so still riding on the Big Apple rear tire.

Just using one 36V battery now in the winter. Max speed motor only is 34-35km/h. With a bit of pedaling speed gets close to 40km/h Battery sags to 30V under load now in winter temps.

Riding is mostly hardpack snow. I use 15-16 Wh/km when riding mostly WOT and around 10 if I stay around 20-25km/h. Trailer+kid or not doesn't seem to make a huge difference to wh/km, though I tend to ride slower and more carefully with the kid in there.



CA install notes:
I bought a CA with external shunt at ebikes clearance sale, so avoided the "howto solder the CA connector to the Clyte controller problem" Will look into that later.

Couldn't fit the speed sensor to the front fork. Unlike typical suspension forks the rubber boot is placed low, so no non-moving part of the stanchion to put the sensor on.

Tried to fit it on the rear, but ended up too far from magnet. I made a 12mm standoff to get the sensor within 1mm of the magnet and put some vulcanizing rubber around it to make it stay without slipping.

Sounds like it works ok. Very nice pics, I like those too. Winter does tend to reduce the effectiveness of batteries huh. Sounds like you need another one. Very nice setup indeed, and thanks for the review. I am even more interested in that hub now, than when you started.
Brian L.

jag said:

Winter riding update
So how does the equipment hold up?

Snow, salt and low temps has been harsh on the 9sp chain and freewheel. Freewheel is now pretty gummed up. Will try to thaw inside and get some lightweight oil into it.

Rear shock is air and seals drop pressure from 200 to 100psi in a week or two. Glad I don't have air but a real spring in the front Lefty fork. Would be a pain to ride with a dead front shock (b.t.d.t. on the Stumpjumper)

Click to expand...

Update on the freewheel problem: Slush gums it up. Then when colder it gets stuck to the point of not freewheeling. ie I have to pedal all the time at road speed. Thawing and spraying light oil into it un-gums the freewheel. It must not be very well sealed. I just spayed randomly around it and the oil made its way in (presumably the same way as the water.

Rear shock (fox air shock) seems to be leaking less now. Maybe it acclimatized... Another thing I found out the hard way: The Planet Bike shock pump also fails to work below -20C. Had to warm it with my precious hand heat to get the seals to seal.

I have a Jekyll as well ,
will be next XC build,
thanks for the tips.

Why would anyone even try to pull a kids trailer or even one of the "tag along bike" type of things for the kids without a hub motor "helper"? If you have done this for any length of time with just your own power, you are a much better parent (or grand-parent) that I. Cheers

jag said:

Update on the freewheel problem: Slush gums it up. Then when colder it gets stuck to the point of not freewheeling. ie I have to pedal all the time at road speed. Thawing and spraying light oil into it un-gums the freewheel. It must not be very well sealed. I just spayed randomly around it and the oil made its way in (presumably the same way as the water.

Click to expand...

It may be too warm to matter now, but I have a few ideas. The grease they use in those is very low-end, and they aren't well sealed, but there isn't a way to disassemble them and pack new grease. Anything you use will have to be light enough to flow into the freewheel but viscous enough to stay there. Light oil will just wash out again.

I'd completely remove the freewheel and spray it out with a good degreaser (like Simple Green). When I say spray it out, I mean using a lot of fluid, until what flows out is the same color as what you're spraying in. Follow that up with brake parts cleaner. If you have compressed air available, use an air nozzle to blast every last bit of the solvents out of it. Then flow Phil Wood's Tenacious Oil into it until it is nice and saturated. You want clear oil leaking out. Wipe it all off, and reinstall on the bike.

I promise it will never gum up on you again, but it would be wise to refill it with Tenacious Oil every season. A bit more maintenance-intensive, but it's the best fix. If you just buy a new freewheel, it will most likely gum up again.

As for the shock leaking in the cold, you probably should rebuild the shock with new seals/o-rings. Fox sells a kit for $7 MRSP with all the replacement parts, and there are good instructional videos that will tell you exactly how to DIY. An experienced mechanic can do it in 5mins, and a first timer should be able to do it in about 30min, including rewinding the youtube vid and watching parts over as you do each step.


You should be able to get Simple Green, Phil Wood's Tenacious Oil, and a Fox shock rebuild kit at any good LBS. Hope those help. Cheers.

Do you actually use all the gears you have there?
What about a DOS freewheel like this? They keep fit for long.
http://whiteind.com/singlespeedgearing/freewheels.html