Cannondale 700 Jekyll Full Suspension, good Ebike?

[floppy2floppy]

I found a 2001 Cannondale full suspension bike on my local craigslist for $550. I have been looking for a good full suspension frame for a while now and this one looks great for holding batteries. I will be using it with a HS3540 at 100V so I will be topping out around 50+MPH. I want to hear some opinions on the bike or if anyone has used this frame for an Ebike before. Does anyone see any problems or weakness with this bike that I may be overlooking. I attached a picture of the bike. Thank you in advance for your input.

 

[MadRhino]

Yep, it was a good bike. The odd, one of a kind, monotube suspension fork proved very tough and low maintenance.
I would not build one to ride the mountain, but it will be a very good Ebike for the street and mild offroad.
The price is high for a bike of this age, but they didn't sell a lot of those.
The rarity, and good condition would justify the price.

 

[biohazardman]

I would agree and add that the 3540 is a heavy motor so make sure the rear triangle is strong and well secured to the frame on the bike you choose. A wider stance on the connections usually makes it stronger and you will feel less flex on the trails and in corners on the road. Bikes like cars often have parts that get hard to find/get/replace as time goes on. Suspension parts for that may be made of unobtainium? I'm not sure but something to check/think about.

 

[Ykick]

My Super V uses that swingarm and it does great on a single torque arm plus hard steel derailer mount running a mild 9C under 2kw and no regen. For what you plan though a single torque arm and the derailer mount would not be wise.

Can't offer anything about the headshock fork since my Cannondale came to me with aftermarket fork.

 

[neptronix]

biohazard: motor weight doesn't matter since it is not supported by the bike, more so the bike is supported by the motor

When building any electric bike, my focus is always on the rear dropouts. Can a set of torque plates be made that will fit the rear dropouts - or are there no bolt holes / a crazy shaped rear dropout section that makes mounting even some basic torque arms impossible?

I saw a bike just like that the other day, but it was a hardtail. The dropout surface seemed nice and flat with about 3 bolt holes available on at least one side. That's good.

 

[dogman dan]

Whether it's good for 50 mph or not is going to depend a lot on it's flexibility from side to side. Too bendy and the high speed wobble is much worse if you ever get it. Hopefully they meant to make that frame stiff, rather than extremely light.

If you have motorcycle experience, it will help a lot if you ever get to tank slapping.

 

[biohazardman]

biohazard: motor weight doesn't matter since it is not supported by the bike, more so the bike is supported by the motor

When building any electric bike, my focus is always on the rear dropouts. Can a set of torque plates be made that will fit the rear dropouts - or are there no bolt holes / a crazy shaped rear dropout section that makes mounting even some basic torque arms impossible?

I saw a bike just like that the other day, but it was a hardtail. The dropout surface seemed nice and flat with about 3 bolt holes available on at least one side. That's good.

Motor weight makes a big difference in the way it handles as well as the amount of stress put on the triangle pivot points. A heavy motor, as well as too much weight on the triangle, tweaks the frame on corners and makes it feel like a rubber band. Something I really did not care for even on a hardtail. Stronger frames with wider mounting points and motors that weigh less are far more stable on corners and trails. Not that one can't learn to deal with a heavy motor and some frame flex cuz many of us have/do.

 

[neptronix]

Motor weight makes a big difference in the way it handles as well as the amount of stress put on the triangle pivot points. A heavy motor, as well as too much weight on the triangle, tweaks the frame on corners and makes it feel like a rubber band. Something I really did not care for even on a hardtail. Stronger frames with wider mounting points and motors that weigh less are far more stable on corners and trails. Not that one can't learn to deal with a heavy motor and some frame flex cuz many of us have/do.

Sorry, but i can't agree. I've ridden 7lb motors and 16lb motors by now.. I don't notice a difference in handling, or the problem you mentioned. That weight is on the road, and it supports the bike, not the other way around.

BUT... my experience is limited to hardtail bikes. Maybe dual suspension has some natural flex in the rear that i have not dealt with yet. I would imagine that it has more to do with the frame than the wheel though..

 

[MadRhino]

I have not built a heavy hub motor in DH frames that have any chance to flex, for I used only racing frames that have very stiff pivots and linkage. Yet I could experiment the difference of kinetic force that the weight of an X5 vs an H series motor, can apply to the swingarm. A heavier motor is harder on the whole suspension system and pushes the tuning range of the best DH shock to its limits. I have no doubt that the extra weight of the wheel can result in flexing a weaker suspension linkage, thus affect the frame handling in hard cornering.

There is something that I will never try anymore: Speeding with a bike that has lateral flex in a mountain trail. I paid the price to know, and still pay it with pain in my bones every rainy day.

 

[dogman dan]

There you have it from the man that knows. I agree, the cruical question is how flexy the frame is. The faster you go on a rubbery frame, the bigger the risk you are taking.

A lighter motor does help if your frame sucks. My dirt frame is pretty rubbery. I wouldn't take it to the racetrack at all. But with a lightish 9c motor, and speed limited to 25 mph, I can tolerate riding it. I won't ride it with a 40 mph motor on it again for sure.

 

[SamTexas]

There is something that I will never try anymore: Speeding with a bike that has lateral flex in a mountain trail. I paid the price to know, and still pay it with pain in my bones every rainy day.

Both of my ebikes are on steel frames, without rear suspension. So I assume the frames are robust and have no lateral flex. What is lateral flex? Yes, I know it's the lateral movement. But how bad does it need to be to be noticeable? How do you tell when you have it? If I intended to buy a new bike, how do I ensure that it does not have lateral flex before I write the check?

 

[miro13car]

good points, motor weight

 

[MadRhino]

Both of my ebikes are on steel frames, without rear suspension. So I assume the frames are robust and have no lateral flex. What is lateral flex? Yes, I know it's the lateral movement. But how bad does it need to be to be noticeable? How do you tell when you have it? If I intended to buy a new bike, how do I ensure that it does not have lateral flex before I write the check?

The material it is made with has little to do with the stiffness of a frame, in fact many lightweight CF frames are stiffer than a heavy steel frame. Tubing size, geometric and mechanical design are the main factors. Titanium is a very tough material to make a bike, yet it is the most flexible, and it is its flex that makes it so durable. A frame can be very stiff and at the same time very fragile, an extremely stiff CF racing frame has a short life expectation, for what doesn't flex will suffer structural damage when it has to stand excessive force.

The flex of a frame, typically the tail, makes the bike twist under stress, thus momentarily affecting its alignment. Fast and hard cornering are the situations where you first notice the amount of flex of a frame, especially when there are bumps in the turn, for its handling will be affected, making you over or under estimating the turn radius. A very flexible frame doesn't need a turn to affect handling, some will start to wobble at high speed if the wheels are not perfectly aligned and trued.

When you are speeding off road, where the bike has to stand very high lateral forces cornering on the rough, a frame doen't need much flex to suddenly send you flying off the trail. That is why the DH racing bikes are made very stiff, with tubing size and design that may seem excessive at first sight.

The overall frame stiffness, is verified by measuring the flex amplitude between rear and front dropouts, when a force is applied. One can easily feel the potential flex of a frame by taking off the rear wheel and verify the amount of hand force needed to spread or close the dropout width by half an inch.

 

[SamTexas]

Thanks for the explanation. I guess I have never (and probably will never) ridden my bicycle hard enough to feel the lateral flex. I just removed the rear wheel and the derailleur from my Trek cromoly bicycle. Positioning myself in the most comfortable position (where I can exert the most force with my two hands without help from the body weight) I was able to squeeze the rear dropouts by about half an inch, that is using all the strength I have. What does that mean? Is my frame strong, weak or about normal as far as lateral flexing is concerned?

 

[MadRhino]

I can't judge of your strenght, and I can't rate what you can do to your frame according to my own strenght, for I can bend a horse shoe with my hands.

You'd have to compare with other bikes to know.

 

[SamTexas]

I can't judge of your strenght, and I can't rate what you can do to your frame according to my own strenght, for I can bend a horse shoe with my hands.

You'd have to compare with other bikes to know.

I'd like to see a video of that horse shoe bending

You're right. When I get a chance I'll try a $100 Walmart bike.

 

[corkscrew]

Being that Cannondales are all aluminum, I'd be sure to overbuild the torque arms if using a hub motor.

Also, I know a local cannondale shop still rebuilds those mono-shocks, and I bet if you hunt around enough, you can find an adapter to run a more traditional front fork on it.

 

[dogman dan]

My test for lateral flex is to reach at least 20 mph, then induce a wobble by oscliating the steering back and forth rapidly. Simulates a high speed wobble. If it flexes, you can look down at the frame and see lots of movement. IMO cheap y frames really flex, like the mongoose wallbikes that sell for $150 or less. Better y frames can be fairly stiff, as my giant is.

But a really cheap steel hardtail can be quite stiff, having a no suspension traditional frame. The stiffest hardtail frame I own got made into the racing bike.