Motorizing a bike with full suspension.

Discussion in 'General Questions' started by motorbikemike45, Apr 13, 2013.

  1. I have to scrap my newest e-bike because the rear suspension has begun to twist. There are two basic types of rear suspension, one has a U shaped lower arm with two articilated arms that act on a rocker to a spring(called a "shock"), the second type has a triangulated arm that pivots and acts directly on the shock in a straight line. My failed e-bike rear suspension was of the first type and is all alloy. I will no longer use such a rear suspended bike to motorize. The U shaped lower control arm made of alloy has little tortional rigidity and can twist slightly, this has become a permanent twist on my bike and will eventually fail catastrophically. A bad failure at the wrong time and place could spill you right in front of a cager at speed. Not a good thing at all. While a steel U lower control arm would be stronger than alloy, I feel the second type, with a triangulated control arm operating on a nearly straight line to compress the spring is a far stronger system. My old Genesis 2600 alloy bike was not strong enough to handle my 220 pounds, plus the weight of the bike, motor, battery, and the cargo I occationally carried on the rear rack. I am now swapping all the good e-bike gear to a new Schwinn Protocol 1.0 mountain bike with alloy center frame, but a steel triagulated rear suspension. I will also swap the road gears and premium aftermarket street tires and wheels onto the new bike. I love the smooth ride of a full suspension bike, but be careful of which rear suspension bike you choose. I expect the new ride to hold up much better than the old one did. My first e-bike, the one I call green bike, has held up very well for a very inexpensive full suspension bike. It has a triangulated steel rear supension arm. I'll post pix of the new Schwinn when it is completed.
     

  2. professor

    professor Active Member

    Good word Mike.
    I have never seen the type you described as number one. I have type 2 and have no doubt as to the strength.
    My second bike has the steel rear section- no problems.
     
  3. I see them all the time on cheap MTBs in the big box stores. Basically, any full suspension bike with rockers operating the shock will be of the type I referred to.
     
  4. jaguar

    jaguar Well-Known Member

    Thats good for me to know since I want to convert my ride to full suspension ands I know I will stress it much more than any e-bike could.
     
  5. The stress I put on my bike was not from excess power, but weight. E-bikes add twice the weight to a bike that a gas engine adds. A 14 to 17 pound electric motor and a 14 to 18 pound battery, plus the comtroller and wiring harness, etc, compared to the 10 pounds or so a 50cc 4 cycle engine weighs. The stress comes from hitting bumps, like storm sewer grates, at speed. Torque and power stress the suspension much less than a heavy bike hitting a big bump. The geometry of the rear suspension allows it to handle more torque and power than your engine puts out. Of course, if your engine is highly modded, it is putting out a lot more power and a little more torque. A strong rider accelerating from a stop at full power will put more torque through the bike's chain with his leg muscles and weight than a less than 50cc engine. The twist my bike is experiencing is canting the top of the rear wheel a little over to the right side, which is not the result of power or torque transmitted to the wheel, but of hitting bumps at 20+MPH with excess weight.
     
  6. Fabian

    Fabian Well-Known Member

    @ motorbikemike45

    If you could only know what i know, then you'd be happy to know that a certain vendor is looking into the idea of replicating the GT LTS frame; in steel and with disk brake mounts.
    It will do everything that are currently asking for in a motorized rear suspension bicycle with either a Chinese 2-stroke engine or a 4-stroke engine or you could use an electric motor if it so takes your fancy.

    It's in the works. You will just have to be patient.
     
  7. KCvale

    KCvale Motorized Bicycle Vendor

    A good bike certainly helps if you want it to hold together.
    I've only built one full suspension and that was a couple of years ago but the GT bike had a nice design that allowed for a tricked out 66cc SKyhawk motor with HC Head, X-chamber, Boost bottle, bla bla bla.

    [​IMG]

    Surprisingly the the NuVinci N370 hub even held up to the power and soft tail was and still is solid as it is still on the road.

    [​IMG]

    It was an engineering nightmare to build but that is fun part and still one of the fastest most comfortable MB's I've built.
     
  8. Fabian

    Fabian Well-Known Member

    Can't agree with you more: it's all about comfort.
    There is no point toughing it out when your hemorrhoids are taking a hammering from a hard tail rear end.
     
  9. KC, that is one of the most interesting rear suspensions on a bike I've ever seen. I can't quite figure out why such a complex set-up, but if it works well and makes you happy.......cool.
     
  10. KCvale

    KCvale Motorized Bicycle Vendor

    True, but I find a good seat and seat post shock works dandy too ;-}
     
  11. Nehmo

    Nehmo New Member

    I've seen the term 4-piece or 4 part rear suspension used. Mongoose+Status+3.0+Dual-Suspension+Mountain+Bike.jpg It comes in several varieties. I tried once to evaluate the relative merits by searching and reading, but I didn't come to a conclusion. The 4-part allows more travel, though.
    I do agree that having a "full" suspension is superior to a "hard tail". Some people claim a rear suspension robs power when pedaling is used.
     
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