Bouncing in the saddle

[Wasp]

Is your saddle too high? This can cause rocking.

I don't think the saddle is too high, however being a newbie maybe it is. I can sit on the saddle, and balance myself on my tippy toes. I had the LBS guy check it out, and he seemed to think it was ok. Last night I was looking at posts about trainers, and realized that when I was fitted for my bike the bike was on a trainer and the front wheel was elevated with some type of plastic block. Now I'm wondering if that would of affected the fit? I had them add a stem riser because I kept feeling like I was falling forward, the stem riser fixed that problem but.....other "roadies" often comment or do a double take when they notice, so im starting to think most cyclist dont put stem risers on there road bike.
Considering I had next to nil core strength when I started out, the stem riser helped with a more upright position. But I still wonder if that plastic block affected the whole fit issue. To get a bike fitted is it usually done only on a trainer?
I have a spin bike and at 90 rpm I don't bounce, so there must be something off with the fit? Or is this bouncing caused by being inexperienced? Or both?

It's definatley bouncing....up and down.....no side to side movement

[laura*]

I was fitted for my bike the bike was on a trainer and the front wheel was elevated with some type of plastic block. Now I'm wondering if that would of affected the fit?

The plastic block was to make the bike mostly level while on the trainer. The reason is that the trainer has to raise the rear wheel up off the floor so that the wheel can spin. Without a block of some sort under the front wheel, the bike would be "going downhill".

[OakLeaf]

I have a spin bike and at 90 rpm I don't bounce, so there must be something off with the fit? Or is this bouncing caused by being inexperienced? Or both?

A spin bike is much heavier than a rideable bike, and it doesn't have suspension (in the form of tires) between the frame and the ground, so it takes a LOT to make one bounce. As in, a WHOLE lot. (Pick your rideable bike up a couple of inches off the ground, be ready to catch it when it bounces, then drop it and watch it bounce. Now try the same thing with the spin bike, except don't bother being ready to catch it, because it isn't going to bounce.)

It's possible there's a fit issue, but it's more likely just a matter of practice.