Full Suspension Frame Style for a Hubmotor

[GoFastGus]

Hey all, I'm almost certain that a full suspension frame is going to be the way to go on my next bike. My friend is building a bike similar to the one I was planning, with a large hub motor in a fat tire bike, so I'll get to try his out when he's all done. Anyway, I'm looking for an FS frame on FB, CL, Pinkbike, and Ebay (welcome to other options for places to look), basically just for the frame or the frame and a shock.

A little about the build vision:
Frame: full suspenion mountain bike, 17-19.5" frame, large open space in the front triangle, 1-1/8" straight/unthreaded headtube, 26" wheel size
Powertrain: Leaf Bike 1500W hubmotor, 3T or 4T depending on wheel size and battery config. 52/60V battery (likely going to be custom built to fill out the triangle)
Suspension: dual crown front fork & coil spring rear shock w/ adjustable rebound (adjustable compression would also be nice), brands ex. Fox, Rockshox, Marzocchi, etc.
Wheels: 26" front, Possibly a 24" rear wheel if suspension geometry allows it, more torque and would work well with a lower winding.
Tires: 26x2.5" Hookworm front, likely a 24x2.5" Hookworm rear unless I find : A. a frame that can fit a wide enough wheel B. a 24x3" semi-slick that's puncture resistant enough and not unobtanium.
Use case: almost exclusively street, some gravel paths. Mostly looking for suspension that will absorb bumps and potholes at high speeds.

My options fall into a few categories of suspension design (Single Pivot, Single Link, Dual Link, & Horst Link), and a few shock locations:

Single link, shock at back of triangle: Ex. Kona Stinky (Ebay listing) Asking $308, $6 shipping. (can't find wheelbase online yet)

I like how this like turns a lot of travel in the rear suspension into much less at the shock. I also like its location close to the bottom. This would set me up well for a triangle battery pack. If this design works well for my goals, I'll keep an eye out until one at a good price comes along.

Single link, shock at top of triangle: Ex. Rocky Mountain Element Race (Ebay listing) Asking $180, $58 shipping. (can't find wheelbase online yet)

I like this link design a little less, because it seems like the ratio between suspension travel and shock travel is closer to 1:1. The shock's location also makes a triangle battery more difficult, but it lets me mount a downtube battery lower, which would lower my center of gravity. This bike being more optimized for a downtube battery rather than a triangle battery might make its power potential more limited.

Single link(?), shock at top of swingarm: ex. Specialized Epic (Ebay listing) Asking $230, $100 shipping. Wheelbase: 1106mm

First off, does this single link function more like a single pivot suspension? The shock is mounted between the top of the swingarm and the frame. The link only locates the top end of the swingarm, it doesn't alter the leverage the swinarm has on the shock, does it? The triangle is undoubtedly has the most space to put a battery in, but my concern is how the shock might interfere with a hub motor. The disc side of the Leaf Bike hub motor pokes out some, but it doesn't say how much in the schematics on their site. Without measurements that confirmed that a Leaf Bike hubmotor would fit, or someone else posting their Specialized Epic- style frame with a hub motor in it, I'm sadly gonna pass on something like this.

Dual link, shock at bottom of triangle: Ex. Giant Trance (Ebay listing) Asking $300, $70 shipping. Wheelbase: 1085mm

This suspension design is supposed to be better at preventing pedal bobbing than single links or single pivots. However, I don't have any plans to install a pedal drivetrain at this point. Maybe waaaaaay down the line for it to look more plausibly like a bike, but not for any practical reason. In that case, is a dual link suspension design really all that much better than a single link (given the price difference between the two)? My understanding of how the suspension works on one of these is much less solid than on a single link or a single pivot frame. The frame has room for a battery, but the top tube is at a steeper angle which limits the size of a battery.

Horst link, shock at back of triangle: Ex. Giant XTC NRS 1 (Ebay listing) Asking $200, free shipping. Wheelbase: 1056mm

This design is supposed to be quite good for pedal bikes, I don't know how well that translates to ebikes. Other than that, there's plenty of room for a battery. Is the shock being a couple inches higher than the Kona Kikapu really a big deal given the suspension design?

I know wheelbase is important for stability at high speeds, but how much stability would ~2% more wheelbase gain me? I'm also curious if any of these designs have a narrow gap between the swingarm forks or if the linkage design is poor for street riding. Are there any other factors I'm not considering? Are any of these bikes notably good or bad choices?

 

[neptronix]

I would pick your suspension design / frame based entirely on:
Can it fit a battery?

Anything else is secondary!

 

[Nix Liou]

Single link, shock at top of triangle: Ex. Rocky Mountain Element Race (Ebay listing) Asking $180, $58 shipping. (can't find wheelbase online yet)

I like this link design a little less, because it seems like the ratio between suspension travel and shock travel is closer to 1:1. The shock's location also makes a triangle battery more difficult, but it lets me mount a downtube battery lower, which would lower my center of gravity. This bike being more optimized for a downtube battery rather than a triangle battery might make its power potential more limited.

Just by eye, it looks like this would have the most room for a custom triangle battery.
Much more than the giant trance, which has a lower top tube, similar to the kona, but the kona's suspension takes up more space it looks like, and perhaps even more than the specialized because it again has a lower top tube. If you can get the triangle inner dimensions and the dimensions of the shock and link arm, then that would be helpful for deciding which would work best...
The triangle of the Specialized would be the easiest to pack with a battery at least, without needing a "cutout" from the shape.
Also, if you look at the pivot point of the element frame you can see that the seatstay attaches almost 2x as far out from the pivot on the arm compared to the suspension, so it looks like it's about 2:1 compression.

2% wheelbase won't matter anywhere near as much as headtube angle for high speed stability. Running a 24/26 mullet will change the wheelbase and give a slacker head tube angle vs staying 26/26, which will lead to a boaty feel at slow speeds but good high speed stability.

I tried a bit of googling but I'm unsure if the element race is aluminum or steel. It's older and has the thinner tubing look of a steel frame, and if that's the case, I would maybe choose it over the others.

What's the target for battery capacity/power here? Any of these bikes could fit a battery capable of 1500w easily, and probably a sizeable amount of capacity as well. If you ate willing to go double width, then even more of course. If you can get the internal dimensions of the triangle for some I can mock it up in CAD real quick to demonstrate.

 

[2old]

The welds on the Element suggest (to me) that it's aluminum. As above, I wouldn't worry too much about the pedaling characteristics since you'll have a big motor. What I would worry about is a double crown fork on a "single crown" bike.

 

[GoFastGus]

Just by eye, it looks like this would have the most room for a custom triangle battery.

Either that or the Specialized, yeah.

Much more than the giant trance, which has a lower top tube, similar to the kona, but the kona's suspension takes up more space it looks like, and perhaps even more than the specialized because it again has a lower top tube. If you can get the triangle inner dimensions and the dimensions of the shock and link arm, then that would be helpful for deciding which would work best...

I'll look online and maybe ask sellers on ebay for dims.

Also, if you look at the pivot point of the element frame you can see that the seatstay attaches almost 2x as far out from the pivot on the arm compared to the suspension, so it looks like it's about 2:1 compression.

Are you talking about how far out from the top tube plane that the seatstay forks meet as compared to the top arms meet?

2% wheelbase won't matter anywhere near as much as headtube angle for high speed stability. Running a 24/26 mullet will change the wheelbase and give a slacker head tube angle vs staying 26/26, which will lead to a boaty feel at slow speeds but good high speed stability.

I'm looking for frames that have a long enough axle to crown length that adding a dual crown fork won't change the geometry too much. Decreasing the rear wheel size by an inch would decrease the headtube angle by ~1%.

I tried a bit of googling but I'm unsure if the element race is aluminum or steel. It's older and has the thinner tubing look of a steel frame, and if that's the case, I would maybe choose it over the others.

They're all aluminum, I couldn't find any good quality steel suspension frames.

What's the target for battery capacity/power here? Any of these bikes could fit a battery capable of 1500w easily, and probably a sizeable amount of capacity as well.

Not certain yet, ~80A, 24AH? Like 14S8P or 16S7P out of 21700 cells. I'll use this tool to figure out how big a battery I can build.

If you ate willing to go double width, then even more of course.

I'd prefer single, but I'm not ruling anything out at this point.

If you can get the internal dimensions of the triangle for some I can mock it up in CAD real quick to demonstrate.

I'll look for dims, and I'll keep this thread updated.

 

[GoFastGus]

What I would worry about is a double crown fork on a "single crown" bike.

I'm concerned about that too. I'm looking for a bike with a longer axle to crown length or fork length (the Kona Stinky has a fork length of 557mm according to this Kona PDF) so the suspension geometry would be minimally changed by a dual crown fork. I'm also looking for a strong top tube that can take the abuse of a dual crown fork.

 

[E-HP]

I would pick your suspension design / frame based entirely on:
Can it fit a battery?

Anything else is secondary!

I’m going to say available rear suspension parts and bushings is a close second.
Out of the frames shown, the Rocky Mountain looks best for battery space, followed by the kona. The longer head tube on the Rocky Mountain makes a big difference. The Kona looks decent, then the nrs.

The frames with hydroformed tubes always steal battery space. You need to bring a cardboard pattern of the battery to check, before forking over any bucks though.

 

[99t4]

You need to bring a cardboard pattern of the battery to check, before forking over any bucks though.

This! Of course you can't do that if buying remote, but even then, I remember one CL bike I was interested in, local but not that local. Not wanting to make a wasted trip, I had the guy make a cardboard template to my dictated dimensions and test fit it. He reported it didn't fit, so that was the end of that.

Why are you only considering stripped frames? A full bike seems like the better option as it already has all your other necessary components and often is not that much more expensive.

Also: Don't let too much perfectionism get in the way of making consistent progress!

 

[neptronix]

I had the guy make a cardboard template to my dictated dimensions and test fit it. He reported it didn't fit, so that was the end of that.

Big brain move!

Why are you only considering stripped frames? A full bike seems like the better option as it already has all your other necessary components and often is not that much more expensive.

You can get some pretty cheap high end frames this way on places like ebay, even if it's a bigger pain in the ass to setup

 

[Stealth_Chopper]

Hey all, I'm almost certain that a full suspension frame is going to be the way to go on my next bike. My friend is building a bike similar to the one I was planning, with a large hub motor in a fat tire bike, so I'll get to try his out when he's all done. Anyway, I'm looking for an FS frame on FB, CL, Pinkbike, and Ebay (welcome to other options for places to look), basically just for the frame or the frame and a shock.

A little about the build vision:
Frame: full suspenion mountain bike, 17-19.5" frame, large open space in the front triangle, 1-1/8" straight/unthreaded headtube, 26" wheel size
Powertrain: Leaf Bike 1500W hubmotor, 3T or 4T depending on wheel size and battery config. 52/60V battery (likely going to be custom built to fill out the triangle)
Suspension: dual crown front fork & coil spring rear shock w/ adjustable rebound (adjustable compression would also be nice), brands ex. Fox, Rockshox, Marzocchi, etc.
Wheels: 26" front, Possibly a 24" rear wheel if suspension geometry allows it, more torque and would work well with a lower winding.
Tires: 26x2.5" Hookworm front, likely a 24x2.5" Hookworm rear unless I find : A. a frame that can fit a wide enough wheel B. a 24x3" semi-slick that's puncture resistant enough and not unobtanium.
Use case: almost exclusively street, some gravel paths. Mostly looking for suspension that will absorb bumps and potholes at high speeds.

My options fall into a few categories of suspension design (Single Pivot, Single Link, Dual Link, & Horst Link), and a few shock locations:

Single link, shock at back of triangle: Ex. Kona Stinky (Ebay listing) Asking $308, $6 shipping. (can't find wheelbase online yet)
View attachment 380553
I like how this like turns a lot of travel in the rear suspension into much less at the shock. I also like its location close to the bottom. This would set me up well for a triangle battery pack. If this design works well for my goals, I'll keep an eye out until one at a good price comes along.

Single link, shock at top of triangle: Ex. Rocky Mountain Element Race (Ebay listing) Asking $180, $58 shipping. (can't find wheelbase online yet)
View attachment 380543
I like this link design a little less, because it seems like the ratio between suspension travel and shock travel is closer to 1:1. The shock's location also makes a triangle battery more difficult, but it lets me mount a downtube battery lower, which would lower my center of gravity. This bike being more optimized for a downtube battery rather than a triangle battery might make its power potential more limited.

Single link(?), shock at top of swingarm: ex. Specialized Epic (Ebay listing) Asking $230, $100 shipping. Wheelbase: 1106mm
View attachment 380549
First off, does this single link function more like a single pivot suspension? The shock is mounted between the top of the swingarm and the frame. The link only locates the top end of the swingarm, it doesn't alter the leverage the swinarm has on the shock, does it? The triangle is undoubtedly has the most space to put a battery in, but my concern is how the shock might interfere with a hub motor. The disc side of the Leaf Bike hub motor pokes out some, but it doesn't say how much in the schematics on their site. Without measurements that confirmed that a Leaf Bike hubmotor would fit, or someone else posting their Specialized Epic- style frame with a hub motor in it, I'm sadly gonna pass on something like this.

Dual link, shock at bottom of triangle: Ex. Giant Trance (Ebay listing) Asking $300, $70 shipping. Wheelbase: 1085mm
View attachment 380551
This suspension design is supposed to be better at preventing pedal bobbing than single links or single pivots. However, I don't have any plans to install a pedal drivetrain at this point. Maybe waaaaaay down the line for it to look more plausibly like a bike, but not for any practical reason. In that case, is a dual link suspension design really all that much better than a single link (given the price difference between the two)? My understanding of how the suspension works on one of these is much less solid than on a single link or a single pivot frame. The frame has room for a battery, but the top tube is at a steeper angle which limits the size of a battery.

Horst link, shock at back of triangle: Ex. Giant XTC NRS 1 (Ebay listing) Asking $200, free shipping. Wheelbase: 1056mm
View attachment 380552
This design is supposed to be quite good for pedal bikes, I don't know how well that translates to ebikes. Other than that, there's plenty of room for a battery. Is the shock being a couple inches higher than the Kona Kikapu really a big deal given the suspension design?

I know wheelbase is important for stability at high speeds, but how much stability would ~2% more wheelbase gain me? I'm also curious if any of these designs have a narrow gap between the swingarm forks or if the linkage design is poor for street riding. Are there any other factors I'm not considering? Are any of these bikes notably good or bad choices?

Hi Gus, This topic has been at the top of my list since I began riding and then I only built one hardtail afterwards for one summer backup. I've studied all these designs and their "old" buried manufacturers specifications intently because of several reasons. 1) I am 5' 7" tall with ~26" inseam and I require 17 1/2" frame (26" as above) RARE 2) Battery technology restricted my frame choice for battery fitment utilizing a template for the smallest high quality impact resistant well built commercial pack to fit in the frame. I want to ride period. 3) My background in Aerospace and living in Connecticut near Cannondale since 1984 I chose to collect and build Cannondale Mid-Drive Jekyll eBikes on Single Pivot Frames built >=YR2000 if Possible + up to 2004 because each pivot introduces SLOP. Good Luck Gus, Mike

 

[Stealth_Chopper]

Early Cannondale Scalpel Models of a similar generation ~YR2000? may be a consideration for you with a big 'triangle' however these are most often complete bikes that are well loved but occasionally overlooked.

 

[GoFastGus]

I’m going to say available rear suspension parts and bushings is a close second.

I'll look into that, thanks!

Out of the frames shown, the Rocky Mountain looks best for battery space, followed by the kona. The longer head tube on the Rocky Mountain makes a big difference. The Kona looks decent, then the nrs.

A long head tube is important to supporting a fork, right?

The frames with hydroformed tubes always steal battery space. You need to bring a cardboard pattern of the battery to check, before forking over any bucks though.

I don't know much about hydroforming as opposed to other ways to build a frame, I'll look into that. Cardboard template was part of my plan before any money gets spent on a battery.

 

[E-HP]

A long head tube is important to supporting a fork, right?

I don't know much about hydroforming as opposed to other ways to build a frame, I'll look into that. Cardboard template was part of my plan before any money gets spent on a battery.

Na, the longer headtube increases the area inside of the triangle, where the battery goes. On these two examples from your post, you can see how the longer headtube directly increases the area inside of the triangle. The hydroforming on the white frame, where the top, down, and head tube meet, may look cool, but it steals a bunch of space that could make the difference between a battery pack fitting or not.

 

[GoFastGus]

Early Cannondale Scalpel Models of a similar generation ~YR2000? may be a consideration for you with a big 'triangle' however these are most often complete bikes that are well loved but occasionally overlooked.

I’ll take a look, thanks! It sounds like we have similar goals for a project, I’ll keep you posted in what direction I go.

 

[GoFastGus]

The hydroforming on the white frame, where the top, down, and head tube meet, may look cool, but it steals a bunch of space that could make the difference between a battery pack fitting or not.

View attachment 380605

Gotcha, thanks so much for teaching me! I’ll keep a look out for non-hydroformed frames with longer headtubes to maximize battery fitment.

 

[GoFastGus]

This! Of course you can't do that if buying remote, but even then, I remember one CL bike I was interested in, local but not that local. Not wanting to make a wasted trip, I had the guy make a cardboard template to my dictated dimensions and test fit it. He reported it didn't fit, so that was the end of that.

Cardboard template seems like a great idea! I’ll have to ask sellers about that before I buy something.

Why are you only considering stripped frames? A full bike seems like the better option as it already has all your other necessary components and often is not that much more expensive.

I was looking at full bikes, but I’d need to replace too many components for it to make sense to me. Plus frames give me more choice around suspension geometry

Also: Don't let too much perfectionism get in the way of making consistent progress!

Good advice!

 

[2old]

Also consider the type of frame. For example, the NRS was a cross country bike AIR, and probably built "lighter" (so less robust) while the Kona probably was more "Enduro" and heavier which doesn't matter for an "3".

 

[GoFastGus]

Also consider the type of frame. For example, the NRS was a cross country bike AIR, and probably built "lighter" (so less robust) while the Kona probably was more "Enduro" and heavier which doesn't matter for an "3".

Good idea. I'm looking for a bike with a strong frame and a long axle to crown length to accomodate a dual crown fork. I'll revise my list of frames in contention.

 

[GoFastGus]

Update on what frames I'm considering:

From the last list, the Rocky Mountain Element Race: long headtube, lots of triangle space, but still don't have info on the axle to crown length. I’m gonna keep looking for the axle to crown length of a 1998 Rocky Mountain Element Race or a Marzocchi Bomber Z3.

-2000 Rocky Mountain Instinct (Ebay listing) $200, $50 shipping

Similar to the Element Race, however this frame is 20.5” and designed for 20” wheels. Need to read more about the axle to crown length, but if it’s the same as the element, I’ll probably take this frame for more space and closer to original geometry after a longer fork and wider diameter wheels.

Motobecane Fantom Team: (Ebay listing) $220, free shipping

Seems like a good bargain given the openness of the frame, the length of the head tube, and the welds as compared to hydroformed tubes.

Novara Method Team (Ebay listing) $200, $27 shipping

Similar to the above. Need to look at wheelbase & chainstay as compared to the above.

Kona Coiler Dee-Lux: (Ebay listing) $195, $50 shipping

Similar to the Kona Stinky, but smaller axle to crown length. This could be a good choice given the size and the thicker tubing near the headtube, but finding the right fork could be difficult.

I’m not ordering anything until I have all the info and I find a good deal. I’m open to more feedback or suggestions for alternative frames.

 

[OCD Garage]

Himalo ebike frame. I built one of these Himalo ebike frames from Aliexpress. I ride all the downhill/free ride terrain that my acoustic friends ride and it's been great. I used a 45 amp controller and a 72v down tube pack. I can easily get 3+ hours of riding time.