30 Mph Electric Mountain Bike


A 48 volt power house pushes this mountain bike at speeds up to 30Mph.  That’s a bit of a boost from many off the shelf E-bikes. [Jennifer Holt] wanted speed, and to retain the off road capabilities of her bike, so she made a custom one. As you can see in the video, this thing gets going fast and hills are no problem. She says that it will toss you off if you slam the throttle, and we believe her. We know some of you will insist on chiding her because she’s not wearing a helmet in those videos. She did manage to break her elbow offroading in the video after the break. That part is edited out though.

[via Makezine]


40 thoughts on “30 Mph Electric Mountain Bike

  1. “The biker chick leather jacket is completely out of place tho.”

    Right, because leather jackets are about the “look” rather than for abrasion/laceration protection.

  2. I wore the jacket because it was November, and it is the one I wear when riding my motorcycle, so I already had it on. as for the music… that’s all my dad’s. he took the video and did the editing. I don’t own a video camera, so I had to contract that part out ;)

  3. @JR In Ohio, an electric bike that exceeds federal standards(20+ mph on level ground, 1KW, nonfunctional pedals) requires plates.

    That said, I love the statement “I had to set the current limit in the Alltrax controller to half its max value, otherwise it was impossible to keep the front wheel on the ground.”

  4. 30mph is 50km/h, right? I go that fast on my bike, with a bit of a boost from gravity, all the time.

    Still, wicked build. But it’s certainly not too fast, IMO.

  5. Knobby tires are no good on paved surfaces. I’d put a street tire on the back wheel(or something less aggressive) unless this is strictly a trail bike. Same reason why dirt bikes are no good on streets.

    Also, what’s with the frame? The seat looks particularly floaty.

  6. @jeff-o yep, thats within the EU moped definition. So one would technically require a license plate such for it. And yes, one can go faster on a bicycle, but the el-cycles are usually built so that when the speed goes above 25kmh it will cut the power to the engine. This so that one can ride them without any kind of license or similar.

  7. As for the 30 MPH top speed, I used to be able to do that with only a small amount of help from gravity on a road. I could do 25mph on a flat for around a 1/2 mile. A road bike would have let me go much faster if i wanted to.

    As for the build, I think the lack of working peddles is an issue, say the bike runs out of juice 2 miles from home? Well you could walk it, but i’d rather just peddle home, it’s easier than pushing a heavy ebike home. It looks like it was about $4000 in parts, i’m thinking a low end dirt bike would be about that used, and be a lot more fun.

  8. fun idea, however since the pedals are removed it appears that the motor is always engaged. a charging circuit for going downhill would be a neat addition to this project.

  9. “She says that it will toss you off if you slam the throttle”.

    LOL! bit of an odd addition for something you’d use in public but at least you’d be able to get away before the cops turned up.

    Joking aside, I think this is great. Obviously the main thing is how long the battery lasts, how far can you travel and what’s the recharge time?

    Pedals would be nice even if they were fake as it’d look way more funny if you were pretend cycling really slowly but doing 30mph.
    The cops would pay less attention too.

  10. When I was building this, everyone said I should add pedals too. This really wasn’t the point of the project. I wanted something fast and fun for playing around off road. A dirt bike is cheaper and more powerful, but where’s the fun in that? I wanted to build electric to see if I could. Adding a separate drive train for pedal power would have made things more complicated than I wanted.

  11. In Ontario that thing is completly illegal, too fast for an e-bike and can’t be licensed as a moped, so it could only go off road, unless you wanted a $2000 ticket!

  12. This is great, legal in the U.S.? no, but who cares? Gotta be heavy with all the batteries she packed into it, might have been better to use an old motorcycle frame, couple of hard knocks could break the frame, I how she goes for that next time, as long as it passes inspection (and assuming she can get the thing insured) she can plate it and drive it around the U.S. i wonder how long the battery life is?

  13. @Jennifer: Very cool build.

    All of you “It’s illegal” people should chill out. It’s not illegal if she only uses it off-road.

    Even if she does want to ride on the road, if she sticks to the legal limit for electric bikes in her area nobody will know that it can go faster, and she’s not likely to be hassled.

  14. Here in michigan i think that might be considered a motorcycle (no joking…)

    IDK how the state rates electric bikes, but if you were to slap a 51cc motor on a regular pedal bike, its instantly a motorcycle, other wise <50cc is a moped.

    That is pretty wicked though, i thought about building an electric bike but its way to expensive…

  15. Jennifer, that bike looks like a whole heap of fun – the broken elbow not so much. :-(
    Hope it heals well and doesn’t put you off being adventurous, life’s sweeter when you take big bites!

    What sort of battery-life do you get when you’re off-roading?

    If you’re not bothered about needing to be street-legal, what might you do different in the next version to optimise the (already impressive) off-road performance still further?

  16. For better off-road performance, I would go to motocross components for the wheels/fork/shocks. Also a bigger battery. Electric motors pack a huge punch, but they are only as good as the batteries. The small cells I used were tedious to build into a pack. I would try to get larger cells next time. A123 makes a 20AH pouch style battery, but I don’t know where to get them. Other companies make similar products. You could try http://www.falconev.com they might be able to get higher capacity A123’s or equivalent

  17. @aztraph: Be careful with gross generalizations. This isn’t illegal “in the US” because each state has a different set of laws. In Colorado for example, this would be considered a Moped, and not need plates. If she added a light in front and reflector in back, she could drive it on the streets as well as in bike lanes.

    @Jennifer: This is awesome! I like that you used a MTB frame rather than a motorcycle, I’m sure it saves a lot of weight and that frame doesn’t look too wimpy. If you wanted something more beefy you could use a downhill bike, those frames are incredibly stout. It would be like having an electric trials bike, probably even lighter!

  18. A123 cells seem pretty hard to get. Headway has 12Ah cylindricals that look pretty nice. They have mounting hardware so you can hold them securely, and screw terminals so you can connect them together with small bus bars.

    I disagree with the laws on ebikes (in most areas) A lot of them were obviously written by people who know nothing about electric motors, and not much more about cycling in general.

    I think if you’re riding like a jackass, you should get a ticket (motorized or not). If you’re riding nicely, it shouldn’t matter what your bike is capable of. (Just like a car)

    My bike is considerably faster than this one (in top speed at least) but you would never know it if I didn’t tell you, since I ride within the legal limit any time I’m on public roads.

  19. google grubee starfire 66 cc
    it may not have as sharp acceleration but they do get some nice speed to them, i never wear a helmet(that will be on my tombstone fyi)
    i f’d up my engine mount, would anyone be interested in some tutorials on cheap chinese engine kludging/repair?

  20. Hmmm…..
    A woman who builds stuff.
    Not just stuff cool stuff.
    Rides motorcycles.
    Isn’t afraid of some risk.
    Sounds about perfect.
    I don’t care if it’s legal or has pedals.
    Doesn’t seem to be the point of the exercise.

  21. What’s with all the HATing..I mean this Project is totally BadAss. And all this abiding by the Law BS ? Some of you people need to take your Head out of your own ^$$. I think this is a wonderfully designed project. And remember this is a 1st. Prototype, give this gurl a few more tries and she will be selling them at your local bike shop. My Hat’s off to You Jennifer, Excellent design, and fabrication. Thnxx for sharing 99+

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