Bobbing up and down when pedaling fast
 

I am new to this SS/FG business. Im currently riding my first such bike. But I find that when I pedal fast, i am bobbing up and down a bit when sitting in the saddle, I tried searching Sheldon Brown's site for answers, but found nothing yet. I originally had the seat a bit to high so I was having to reach a bit to comfortably reach the pedals (and was having this issue a bit). So I dropped the seat so now I reach fine, but when I am hammering it i find I bob a bit, I suppose it could be bad technique, but I was thinking maybe it was the position of the saddle. I have it horizontal (measured with a spirit level). Perhaps I need to have the seat pushed back a bit?

For clarification, it's a 54cm frame and I am 177cm, which some mi8ght judge to be on the small end of the scale for me, but my handle bar reach is perfect, I am reaching forward pretty damn far to get into the bullhorns.

What do you think I should try?

typically that's a sign that you're saddle is too high (as you already know based on your earlier adjustment). you could also have the saddle too far back which would yield a similar result. trial and error is the only way to resolve fit issues... take your tools with you and go for a ride making minor adjustments until you get it right.

Ok, got the allen key set in my pocket now! forward and down! gotcha!

hummm, pushed seat forward, went for a quick spin around the block and it is feeling much better.
Thanks.

I will do a full test next time i get to commute to work (rainy season just officially started today, although it was actually dry here today)

You should experience this less the more you ride and the smoother you get. Once you hit a speed/cadence where your legs can't keep up with the rotation of the cranks you will start to bob. Shorter cranks can make spinning faster quite a bit easier too.

shorter cranks will also make hitting the ground a lot less common.
ergo, buy short cranks.

i don't hit the ground (i ride SS:innocent:). It's ok, I will one day flip flop over to fixed when I am brave, I might go up from 42x16 to 46x16 front chainring as I want more top end speed, I can handle all the hills around me fine at the moment.

I saw people talking about the silver messenger Sugino chainrings (when searching info on chainrings) and how they can't find them in the US. i was in a store here in tokyo today (y's international Akasaka) and they had blue, silver and black in stock.

if somebody really wanted some, i could get it and send to you.

price? and what size?

they have all the sizes they come in, price was about ¥7000 if i remember rightly

If you have bad technique, you will bob regardless of fit. Work on a smooth pedal stroke, and eventually you will be able to pedal at very high cadences with no bob.

Just curious, is your seat-post 0mm setback or something more like 20mm?

Dropping 1cm from 175mm to 165mm really doesn't make a difference for hitting IMO, as long as you're not riding a road conversion frame. Track/Fixed spec'd frames have a much higher BB shell (so does cyclocross) for this very reason. Many people ride the shorter cranks to be able to spin much higher. If you're on an old Schwinn Road conversion, or any conversion really, the length of the cranks would play a bigger role.