Originally Posted by
Grumpy McTrumpy
you are too smart to fall for the linear speed vs. gravity thing
It's close enough for a swag. Go to a website like analytic cycling. Put in a 4% climb for a total rider and bike weight of 100Kg, then 99Kg. The difference in speed is a little less than 1%. Put in 90Kg, a reduction of 10% and you get an 8% increase in speed. Close enough for me.
http://www.analyticcycling.com/ForcesSpeed_Page.html