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Old 06-28-19, 01:27 PM
  #15  
echappist
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Originally Posted by kevin****t View Post
Sooo (another thread ).

I haven't started to race yet but I am upgrading my bike from a Domane ALR4 to a Emonda SL6 Disc Pro. The bike I currently ride is 22lbs (Domane) the Emonda I am getting is 17.32lbs.

Why I am interested is because I am almost in the range for being a possible "lead pack or break away" finisher for the D riders in the ECCC (College cycling "league" in USA Cycling). Their averages for roughly 20-40 mile road races are around 23-24mph. Right now in group rides I can average 22mph every week we ride on my Domane.......

So I know speed conversions based on weight are super broad and determined by a lot of factors. The bikes are basically the same when it comes to how aero they are (not very) even though the Aeolus Pro 3 wheels on Emonda may be slightllyyyy more aero.

So lets say we put both bikes (Domane and Emonda) on a straight away for 20 miles completely flat and no head/tail wind. How much faster is the Emonda compared to the Domane in this situation.. Basically I am just trying to find out if just changing to the Emonda is enough to get me to 23/24ish mph average simply because it's less weight.
In the words of Simon & Garfunkel, you are hearing and not listening

Your question above (emphases yours) is a very simple physics question. On a mostly flat parcour, weight mainly affects rolling resistance. Assuming semi-decent aerodynamics, 5 lb reduction in mass results in maybe 0.1 mph speed increase. I plugged in your weight (115 lb or 52 kg) and assumed you are doing 205 W (to ride at 22 mph). Changing the bike from 7.7 kg (17 lbs) to 10.5 kg (22 lbs) barely results in an increase of 0.1 mph. You'd get better speed increases by using faster-rolling tires (increase of 0.2 mph). Put it another way, you could ride a bike made entire of unobtanium and having a mass of 0 kg, and you still can't get a speed increase from 22 mph to 23/24 mph based on decrease of mass per se (the speed increase for a 0kg bike would be 0.2 mph).

On a 6% climb, you'll be ~0.4 mph faster. Over the distance of a mile, that comes out to be 10 seconds.

You can play around with the various parameters here: https://gribble.org/cycling/power_v_speed.html


I should also note that those bigger-framed riders may just climb as well as or even better than you do. I was a full-on fat-ass at 174 cm and 72 kg and broke away on a hilly circuit race while racing ECCC D1 (back when there were enough riders for two separate fields in the Ds). By the same token, you should not presume that a willowy built per se is indicative of climbing prowess. A poster here (@carpediemracing) had a build similar to yours, but aerobic endurance wasn't his forte; what he is good at are sprints. He is very good at seeking shelter in the pack and then punching it
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