Balance and Speed

[Mathew Fy]

we have a large absorbing body

I resemble that remark

 

[Randyc3]

I agree. The Cruzbike rocks. So when the S40 wanders a little while speeding down a hill at 30mph: is this speed wobble? Though it was me not able to balance arm/leg forces well. All I have to do is push left/right with my legs and bike goes in that direction.
How would you test for speed wobble?

 

[Randyc3]

Haaaaa . Your cda greatly improves if you are bombing down a hill with both legs straight. This means you have to have one foot out of the clip. I prefer in all honesty to have both feet clipped in.

-Install Power Cranks and you can have both feet forward without unclipping. probably will detract from riding experience slightly.

 

[billyk]

I agree. The Cruzbike rocks. So when the S40 wanders a little while speeding down a hill at 30mph: is this speed wobble? Though it was me not able to balance arm/leg forces well. All I have to do is push left/right with my legs and bike goes in that direction.
How would you test for speed wobble?

If you soil your pants, it's speed wobble. Otherwise, probably not. You'll know it when you feel it, and I hope you don't. (YouTube will show you videos).

What you're talking about, I think, is a CB-specific kind of wobble, due I think to the heavy front end that wants to fall into a turn.

It happens to me sometimes when I come over the crest of a hill at low gear, gratefully accept a rest while gravity does the work, and forget to upshift. Then nearing the bottom at a good speed, I start pedaling hard; not meeting the expected resistance from my feet, my hands pull the bar into a turn ... And the heavy front end doesn't always come back gracefully. Coupla good, scary wobbles follow.

So yes, what you're feeling sounds like what you say "Thought it was me not able to balance arm/leg forces well", exacerbated by the weight up front.

 

[Randyc3]

Thanks!

 

[Jim Parker]

Here is a photo and overlay showing the geometry of the S40, designed to be a stable yet maneuverable bike. It has more trail and more wheel flop than most bikes, but the combination with the heavy front end works well.





wheelbase 1130.3 mm 44.5 inch
chainstay length 476.1 mm 18.7 inch
rake (front fork offset) 30.3 mm 1.2 inch
head tube angle (steering axis) 70.6 degrees
trail 91.3 mm 3.6 inch
wheel flop 28.6 mm 1.1 inch
average tire radius 344.1 mm 13.5 inch
backrest angle 40.4 degrees
length of bike 1889.4 mm 74.4 inch
height of handlebar 1024.5 mm 40.3 inch
seat height (low point) 598.2 mm 23.6 inch
BB height 685.1 mm 27.0 inch
BB above seat low point 86.9 mm 3.4 inch
seat-backrest lowpoint-to-front axle distance 686.2 mm 27.0 inch

 

[Randyc3]

Thanks.