optimal shark battery placement on my bike, opinions?

Im intending on mounting my shark battery on the downtube on my ebike via rivnut/nutserts

Im wondering what the optimal placement would be, i imagine further back will put more weight on the swingarm and further forward will put more on the front forks

What is the best for handling and weight distribution?

I attached an image with the 3 possible locations in mind edited with my epic paint skills

https://imgur.com/a/60n6d

I’d suggest the middle or lower position, also at least 3 fastening point and use washers as spacers so you don’t deform the cradle.

The shark style case is not very sturdy when right side up so upside down it will be worse. I’d suggest a safety strap of stretchy Velcro too.

The lower the better, keep your center of gravity low for better handling and less tendency to tip over easy when setting the bike against stuff.

Added: might want to add a fender if you ride in the rain at all, prevents slinging water/mud all over the battery in that spot.

Raisedeyebrows said:

The lower the better, keep your center of gravity low for better handling and less tendency to tip over easy when setting the bike against stuff.

Added: might want to add a fender if you ride in the rain at all, prevents slinging water/mud all over the battery in that spot.

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I think this too but don't want too much weight near the back because the hub motor wheel is already adding a tonne of weight and the rear suspension won't work too well

Try the positioning with a couple big zip-ties and a rubber bungy holding it on before you mount it with bolts and nuts, that way you can see how it feels, I suspect it's going to be fine in any of your 3 positions. Looks like you're going to have a fun bike when you're done, nice bike that should handle real nicely and soak up potholes.

The other thing i realised is mounting it further up puts the weight at least closer to the top of the suspension rather than more under it, so it acts slightly more as sprung weight vs unsprung weight? Not sure how big the difference would be in reality

Marin said:

I’d suggest the middle or lower position, also at least 3 fastening point and use washers as spacers so you don’t deform the cradle.

Click to expand...

I installed a Shark pack upside down on a friend's bike. I machined a piece of aluminum angle to provide three mounting points, to stiffen the assembly, and to partially protect the plastic mounting rail against tampering. One side of the angle confirms to the underside of the frame, and the other side sits along the side of the frame.

My own Shark pack is mounted right side up, but also with three mounting points and an aluminum plate to bridge between them.

tolkaNo said:

The other thing i realised is mounting it further up puts the weight at least closer to the top of the suspension rather than more under it, so it acts slightly more as sprung weight vs unsprung weight? Not sure how big the difference would be in reality

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Where you mount it on the downtube has no effect on sprung vs. unsprung weight. It is sprung weight regardless since it is weight supported by the suspension springs. The mount position does affect the bike's center of mass and moment of inertia and hence the handling. Moving the battery toward the bottom bracket should make the bike feel a bit more nimble than mounting it up and forward.

Optimal pack placement for any battery pack would be between the wheels along the line that your axles create.

From that, any deviation should be considered a compromise to a well controlled center of gravity.

I would have to say my recent experience indicates rather the opposite. I have a three unit modular battery pack, one is shaped for the lower rack, and the others on a rack above the top tube. I used to habitually run the lowest one, and one of the upper ones for medium distance, but was working recently on the lower one, so ran the top pair for a change. Despite the higher placement the handling felt great! It suddenly brought back the bike like feel of whipping the wheels side to side to dodge potholes, while the rider stays in place above the bike.
It also markedly reduced how hard the bike wound into turns at low speed (EDIT.. 10 to 20 mph being low speed.) . That seems backwards, but now that I've road tested the different positions a lot, my theory is too low a weight between the wheels tries to sling out to the outside of a turn, making the bike wind into the turn hard, until the gyro effect of wheels at higher speed takes over. (EDIT... it also slowed down the initiation of the turn, then would wind in aggressively with the low CG)
The only very slight negative of the higher placement is the bike gets wobbly riding no hands at about 15 mph, instead of the previous 12ish mph, so not a big difference.

Usually I would run the bottom one and one top one for medium range trips.



This has become the preferred set up for sporty handling.. I even split the upper module to get it higher, which is great, as on long straightaways I sometimes lay my chest on the top battery, lock the throttle on, and drop my hands down and steer directly off of the fork crown... soooo comfy



And just to forestall anybody thinking that doesn't sound right re. the CG change, I've tested it with just the lower module, just the upper, the different combos, high speed vs low speed, straight line and turns, including locking the throttle at different speeds, and initiating into turns no hands and seeing how long it took to get so scary hard into a turn before grabbing the bars again.

cal3thousand said:

Optimal pack placement for any battery pack would be between the wheels along the line that your axles create.

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Oddly, no. Like Voltron says, higher is better up to a point. Basically, you want to concentrate mass as close as possible to the whole system's center of mass, which in the case of a bicycle is pretty close to the rider's center of mass. When the bike leans, it rolls around this point. So the closer the weight is to the roll center, the less inertial moment there is when you want to roll into a turn. Consider for a moment the difference in weight distribution between a MotoGP bike and a Harley.

I remember noting this when I had a Suzuki GSX1100G and my buddy had a BMW R75. My bike was top heavy and his was really low slung (weight wise). Geometry was otherwise pretty similar. But his bike was super pokey getting turned in, and mine just turned without delay or resistance, even though it was much heavier.

I learned that a two wheeler leans not around its contact patches nor its axles, but around its center of mass. So for best results, you put the mass where it can all be wadded up together right under your belly. That way, you don't have to swing any large masses very far from the center of rotation.

wturber said:

Where you mount it on the downtube has no effect on sprung vs. unsprung weight. It is sprung weight regardless since it is weight supported by the suspension springs. The mount position does affect the bike's center of mass and moment of inertia and hence the handling. Moving the battery toward the bottom bracket should make the bike feel a bit more nimble than mounting it up and forward.

Click to expand...

Is it not unsprung weight because it's under the suspension? Mounting it closer to the front as seen in my picture would put the weight higher above the suspension and also further away from the swingarm and hopefully not affect the handling as much

Chalo said:

I learned that a two wheeler leans not around its contact patches nor its axles, but around its center of mass. So for best results, you put the mass where it can all be wadded up together right under your belly. That way, you don't have to swing any large masses very far from the center of rotation.

Click to expand...

Keeping in mind im adding a hub motor to the back which adds a lot of weight, it shouldn't be too bad to put the pack in the green position in my photo to kind of balance things out weight wise

when i test fitted the wheel and sat down on the bike the suspension was basically fully bottomed out and it will be worse with the battery. I plan on upgrading from a 400x2.80 spring to a 550x2.80 spring to hopefully stiffen things up and deal with the weight a bit better

I don't think there's a nickel's difference between any of the prospective locations in your sketch. The thing weighs less than ten pounds anyway, and the overlap between your mounting spots is bigger than the variation. It's like the difference between having a sandwich in a handlebar bag versus one in a seat wedge. I mean, yeah... but no.

Put it where it interferes with other parts the least, and is the least subject to damage. If that's all the same, put it where the wiring harness works out best.

"This has become the preferred set up for sporty handling.. I even split the upper module to get it higher, which is great, as on long straightaways I sometimes lay my chest on the top battery, lock the throttle on, and drop my hands down and steer directly off of the fork crown... soooo comfy "


That's pretty impressive, if I happen to see you going down the road like that some time I'll for sure take notice, I'll either clap or run for cover