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Vintage Sekai 2000 to gravel ebike conversion

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    Vintage Sekai 2000 to gravel ebike conversion

    Hello. Have a vintage Sekai 2000 road bike that was gifted to me years ago. I would really like to convert it into a mid drive electric gravel bike. Would be really great to give a new life and get it back on the road and out of the garage.

    Would like to keep it looking fairly stealth, not obviously an electric conversion.

    Hopefully this is the best place to post.

    Not sure between the TDSZ2 and the BBSXX motors. Kind of leaning towards the TDSZ2 for the torque sensing PA. Want to be able to freely use the throttle with pedal assist...

    Where's the best place to start? How do i figure out what motor standard i need for the frame? What tools i need buy etc?

    Thank y'all so much!

    Check out this link to get started.


      Do you have room to get a little more tire in there? A wider tire is one of the defining characteristics of a gravel bike. Gearing is the other issue especially with something that age, you could be stuck with what you have. I have not looked to see what is available or compatible with freewheels that old. I know lots of us have done late 80's and early 90's usually MTB's with no real issues but late 80's there were a lot of changes when it came to the drive lines.

      Brakes are another area of concern. You will most likely end up going at least a little faster than normal biking speeds so you want to be sure you can stop. You will for sure need new pads since the old ones are likely petrified. New higher end cables may not be a bad idea too. The higher end cables have less flex and stretch in them so that will get you the most force to the calipers.

      An annoyance for gravel is there really isn't any accessories like display and throttle made for drop bars. The displays that mount in the center with dual clamps can usually be made to work on drop bars but things like eggrider or 500c don't work. Same with most throttles. There are all sorts of adapters and extenders made so there are options its just not as easy or straight forward. Brake cutouts you pretty much have to go with the inline type which are a little harder to find than the magnetic ones.

      For stealth I think a triangle bag is a good way to hide the battery. Makes it look more like a commuter bike especially if you have other packs and racks. I have Luna Wolves with the magnetic mounts. I bought their zip tie frame bags and punched holes in the bottom of the bag then mount the magnetic mount through the bag. Grinn in Canada has some flat packs that can be mounted flat on top of a rack or pannier style on the side(s) of a rear rack. The typical 'shark' style packs can't easily be put into a bag and are a little long for typical rear packs. It can be done but you have to find the right rack and pack to fit them.


      • Slythehand
        Slythehand commented
        Editing a comment
        Yes. There definitely is a little room to go wider. Not exactly certain how much, guessing maybe an inch? Was thinking it might need new rims for wider tires. Was also thinking maybe 700c? Seems to be all the rage. What fits is what it's gonna get, not a huge deal. I honestly know very little about changing the gearing and casets, free wheels, and crank standards, etc.

        Bike is rideable right now, minus peddles. Has only been sitting for a couple years. Neighbor gifted it to me but kept the peddled to put back on he's very nice expensive road bike. Just haven't gotten around to buying peddles yet.

        The current brake pads are usable, but yes they will get changed soon enough. The current tires are great, almost new. Not sure about the tubes, haven't tried airing them up to check for any slow leaks or anything yet. Was thinking they may need replaced to fit the new tires? Again, gotta look deeper into that later.

        I personally don't really feel the need for any displays short of battery voltage... don't care about mph read outs not trip/odometer. What makes an egg rider or 500c desirable? Hopefully brake cut outs and simple throttle aren't too big a deal. ^.^

        Definitely want to put a nice little rear rack on it. Would be great place for a battery.

        Was thinking keeping the battery(s) kinda small at first. Was leaning towards a water bottle battery and maybe sneaking one in a nice tool type pouch behind/ under the seat.... But yes there is a LOT of space in the frame.

        New cables really are great idea!

      Stealth is relative. An aftermarket mid drive sticks out like a sore thumb.
      Small hub motors and integrated mid drives are far stealthier.
      I thought my bike was stealth. I've ridden past older folks(60's) while on the local rail trail that stop me and ask about the motor, everytime its happened I was riding about 8-9 mph. And when they see you effortlessly pedaling up a hill forget about any stealth. Twice I've encountered drivers who passed me going up a hill stop at the top to ask about my e bike.

      Click image for larger version  Name:	20210720_143846.jpg Views:	0 Size:	2.32 MB ID:	149320


      • Slythehand
        Slythehand commented
        Editing a comment
        Have zero concern about any one noticing it can glide up hills, throttle only even. It's not a complete secret.

        Mostly really want to retain vintage look, and (with a little luck) hopefully not be too obvious when just sitting. Not being ridden.

        My first thought was a geard rear hub (geared so the hub motor would hide behind the cassette gears, the regular hubs seem rather noticeable). How ever, hub motors for old road bikes like this ended up being a lot harder to find then i thought they would be. Seem to marketed mostly to regular type bike and fat tires.

        Mid mounts are supposed to be much better any way. Yes they do stick out a little, but i definitely find the TDSZ2 to be fairly discreet. BBSHD maybe a bit more obvious, yes.

        Nice looking bike!