Full Suspension XC vs Downhill Frame For Light Duty Offroad

[SHARKBITEATTACK]

So I know alot of you guys go for the DH/Freeride bikes for high speed and serious offroad machines. I'm looking at a Giant NRS XL Frame that I can get a good deal on. How well would something like this work for moderate offroading? Dirt and grass trails with the occasional log and rock I gotta go over. Slow speeds of course, no more than 10mph on the trails and I'm not gonna beat on it or go off any jumnps. My main concern is how well the frame would hold up. I'm a pretty big dude 6'0" and 230lb and I plan on incorporating ALOT of nimh cells so I have a capacity of at least 1kwh. I think that would mean at least 60lbs of batteries.

I'll be running a 9C 2808 @ 72v on 26" tires.

 

[DAND214]

My main concern is how well the frame would hold up. I'm a pretty big dude 6'0" and 230lb and I plan on incorporating ALOT of nimh cells so I have a capacity of at least 1kwh. I think that would mean at least 60lbs of batteries.

nimh cells, WHY? That is not a good choice. Can't parallel them to charge, so charging is a nightmare.

Where will you carry 60lbs of NIMH?

Bike mike do fine by itself, it;s the battery that will kill the build.

Dan

 

[dogman dan]

I don't see a bike problem. But I do see a battery weight problem. Better be pretty dang light duty off road. On technical trails, you'd crash constantly packing that much battery.

It will be a real pain to charge that many strings of nimh too. But if they are free it might make some sense, on anything but off road.

 

[SHARKBITEATTACK]

I had the batteries donated to me and I have about 800 of them. They are pretty high quality cells as far as NiMH goes. 5000mah subC tenergy propel cells that can handle 30A continuous discharge. 3 strings at 72v would give me my 1080Whrs. I have 20lbs of nimh on a rear rack on my current build and overall its working ok... (minus the fact that a couple cells are bad and need to be replaced). Doesn't throw off the balance significantly as far as I can tell. Yeah I get it that A123's or headways would be better but that's not the purpose of this thread.

Anyone else have expierence with using a light duty XC FS frame? I would imagine that it could only be better than my current hardtail.

 

[d8veh]

I have two Giant NRSs that I've converted. They both have rear 500w geared motors: One Bafang CST and ond Bafang BPM. They both have 36v 20aH batteries on a rack. One of the batteries is LiMnNiCo ans weighs abour 4.5kg, the other is a Ping, which weighs 6.5kg. The rear suspension means that you have to mount the rack quite high, so the battery weight is noticeable. The one with the Ping is OK on the road, but too cumbersome for off-road. The other one is manageable but not ideal. You'd need to find some way of mounting your batteries in the frame triangle, but there isn't a lot of room.

The bike frame is strong enough. I'm 100kg.

 

[dogman dan]

20 pounds mounted wrong will still toss you on mildly hard off road riding.

But we were discussing light duty off road. 20 pounds on a rear rack can do that.

Weren't we talking about 60 pounds? Try that and then tell me it doesn't suck. Not saying it will be completely unridable, just that riding it off road won't be fun. Carry no more than 20 pounds off road. And if you can, put that in the triangle. Or put as much of it as possible there.

I ride off road on medium hard trails with a battery on a rear rack. But it's only 4 pounds of battery. If I carry more, I put the rest on the handlebars.

 

[SHARKBITEATTACK]

20 pounds mounted wrong will still toss you on mildly hard off road riding.

But we were discussing light duty off road. 20 pounds on a rear rack can do that.

Weren't we talking about 60 pounds? Try that and then tell me it doesn't suck. Not saying it will be completely unridable, just that riding it off road won't be fun. Carry no more than 20 pounds off road. And if you can, put that in the triangle. Or put as much of it as possible there.

I ride off road on medium hard trails with a battery on a rear rack. But it's only 4 pounds of battery. If I carry more, I put the rest on the handlebars.

Yes I would like for the majority of the weight would be inside the main triangle. As I mentioned I'm using SubC cells which means they are very small and versatile and I can pretty much solder them into any shape I want. Of course this makes the project much more complicated, especially since I want to design a battery box to contain everything and I don't even know where to start with that. Most likely wood for the first attempt.

For the short run I would most likely put a single string of batteries on a rear rack as I have on my current build. (360Whrs 20lbs)

Does the issue with offroading a bike with 60lbs of battery come down to being able to control the bike? I know most dirtbikes weight at least 100lbs and an Enduro definetley more, they seem to get the job done.

 

[SHARKBITEATTACK]

So I wound up buying a Jamis Dakar XCR. It's an 07 model, with deore LX shifters, hydraulic brakes, upgraded rockshox RL3 air shock and a 100mm air fork. Only weighs 31lbs Nicest bike I've ever owned! I bought the bike because it had full suspension and because I thought the frame had a lot of room to accommodate batteries (even tho they would have to be mounted higher up because of shock placement). I've taken it trail riding twice now and it seems to handle the terrain "pretty good". Up until now I've only ridden hardtails. So although it is a big improvement its not perfect. Something tells me that after I load it up with 60lbs of batt + 15lbs of hub motor + my heavy ass (230lbs) that it might be a dog on the trails. Again, not looking to go fast or go off jumps on gnarly trails. I just want a bike that I can go exploring on and be able to handle most of the terrain I come across without having to stand up so much. So this leaves me with the question should I build it up and risk being disappointed? or should I continue looking for a better bike (DH/FR)?

Here's the trail that convinced me a hardtail wouldn't suit my needs. Everytime I hit one of those rocks that are sticking out of the ground I felt like the batteries were getting really beat up. I figured it would only be a matter of time before one of the tab welds, my solder joints or something else was going to break leaving me f****d. The same trail with the FS bike much more forgiving. I intentionally hit all the big rocks and was able to stay seated without getting jolted around. (Mind you that this regular biking not ebiking)


Here's my current build.


Here's the bike I just got


I may be living in a pipe dream thinking that somewhere out there is a bicycle that could go on rough trails and ride like a magic carpet. I'm just looking for advice and others that have already went through this experience. I have a bad habit of starting projects and then getting discouraged and never finishing them. I don't want this to be one of them
Also, in the future I will upgrade to a better battery chemistry but for the time being the NiMH is here to stay.

 

[MadRhino]

Here's the trail that convinced me a hardtail wouldn't suit my needs...

That is not a trail, it is a highway

Dogman is right, your problem is mostly in battery weight.
On this terrain at the speed that you ride, I wouldn't mind so much though.
You still can build a smaller battery pack for off road riding. I carry only 7.5 Lbs of batteries to ride the trails on a perfect;y tuned DH racing bike, yet it is hard and fast on narrow trails that are not forgiving any mistake. Your Dakar will ride fine on the terrain that you show, fit the biggest tires that the frame will clear and don't inflate them too hard.