Wednesday, May 16, 2012

Body Position - Too Tall Again

When you drive a car, you make your driving position so its comfortable, so you can see, and you have good control of the pedals, etc. With a motorcycle, your body position is so much more. And it's so surprising how much the feel of the bike is controlled with body position.

When I bought the ZRX, I recognized that it was pretty tight on the legs. I also found the bike difficult to corner, not natural at all. I've been adjusting on the suspension and that has helped some, but this spring I looked for a way to get more room for my legs. First, I looked at lowering the pegs, but the rear brake and the exhaust pipe are only about 1/2" clearance, so taking the pegs down was not an option.

Then I looked at raising the seat. The front of the seat is located by a tab that goes into a slot at the back of the fuel tank, so the fuel tank would have to go up too. As it happens, the front of the tank couldn't easily move up due to handlebar clearance and mounting concerns, so I decided to just raise the back of the tank. This had the interesting side effect of giving the bike a more forward stance that I like. It also let the stripe on the side of the tank align with the fins on the engine. Hey, this is artistic.

With some help from my friend, John Chamberlin, the best solution for the seat was to raise the whole thing by about 40 mm. Some fabrication and I was able to test ride. By the way, the plan is to add some skirts to the seat that make it come down to the bodywork and recover the seat. More to come.

Here are two pictures, one in the original condition and one with the seat and tank raised. I admit that the scenery in the original condition picture is a tad better than the background of my front yard shown in the modified picture, but hopefully you can get the change in stance.

What a difference!

I now realize that my body position had been all wrong. It was like I was sitting on a toilet made for a child. My legs were so tight that it forced my knees up where they sat on the corner of the tank above the cutouts in the tank intended for my knees. The high position of my knees caused my pelvis to rotate back and my back had to curl into a C shape in order to stretch to the handlebars. The result was not only uncomfortable, but it put my center of gravity too far aft and my upper body and arms in a poor position to control the handlebars.

The reason I know all this is the major difference the seat raising project has made. For a change, my hips are above my knees and the knees fit in the cutouts of the tank as intended. Now, my legs naturally flow around the tank and my body "grips" the bike through the tank. I had always heard about this, but never felt it. My upper body can now lean a little forward in comfort. My arms are slightly bent and I feel like I have leverage over the handlebars. Wow.

In the past, the bike took high effort to turn and the front wheel did strange things like fall into the corner. With the raised seat, turning is easy and I have much more confidence. I even like riding this bike around corners where before it was tiptoe around the corners and goose it on the straight. I'm looking forward to learning this bike all over again.


  1. Jac, some nice leather fringe would cover that gap below the seat.

  2. Good suggestion Doug. I'll consider that seriously, right after I get and ear ring and a skull tat. Fine for some, not for me.

  3. I feel your pain (and joy at finding a solution) as I'm struggling right now trying to find the best position for me on my bike. Rather than putting skirts on the seat, why not build it up the 40 mm or so from the seat pan and then recover the whole thing. Of course you'd have to put the tank back in the original spot, but it's an option.

  4. Canajun,
    I seriously considered that, but getting my knees into the pockets on the tank made a big difference. In truth, I was less confident of my ability to do the right thing in designing the foam than to space up the seat pan.

    Now we'll wait and see how badly I do the seat cover.