Go Back  Bike Forums > Bike Forums > Road Cycling
Reload this Page >

So I made an equation...

Notices
Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

So I made an equation...

Old 12-05-06, 08:19 PM
  #1  
Senior Member?
Thread Starter
 
Join Date: Oct 2005
Location: Denver
Posts: 1,977

Bikes: orbea onix, Cervelo SLC, Specialzed Allez, Cervelo P3 Alu

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 1 Time in 1 Post
So I made an equation...

for climbing.

First off, I apologize for the mixed units. They are just what I'm most familiar with...
v= speed in mph
P= power in watts
m=mass (weight) in lbs.
g=grade (6% grade would be entered as 6)
d=distance in miles of the climb
t= time in minutes to get to the top

first:

v=50P/(m*G)
t=1.2dmg/P

Boring I know but here's what i've learned:

For my weight (200lbs including the bike) and a 7% grade, losing 10 pounds off my ass or my bike is the same as increasing my power by 20 watts. 5 pounds gets me 10 watts.

For a climb that generally takes me 11 minutes, I can cut 17 seconds off that time by losing 5 lbs. or gaining 10 watts of power.

This is in the context of climbing and thus ignores air resistance.

hope it's helpful to someone.

B.
brianappleby is offline  
Old 12-05-06, 08:23 PM
  #2  
Dirt-riding heretic
 
DrPete's Avatar
 
Join Date: Aug 2005
Location: Gig Harbor, WA
Posts: 17,413

Bikes: Lynskey R230/Red, Blue Triad SL/Red, Cannondale Scalpel 3/X9

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Likes: 0
Liked 8 Times in 7 Posts
It's also assuming that the weight lost is not muscle, because the real key is watts per kg. Sometimes losing weight will actually lose you watts as well.
__________________
"Unless he was racing there was no way he could match my speed."
DrPete is offline  
Old 12-05-06, 08:26 PM
  #3  
Senior Member?
Thread Starter
 
Join Date: Oct 2005
Location: Denver
Posts: 1,977

Bikes: orbea onix, Cervelo SLC, Specialzed Allez, Cervelo P3 Alu

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 1 Time in 1 Post
/\word.
brianappleby is offline  
Old 12-05-06, 09:07 PM
  #4  
Senior Member
 
Join Date: Apr 2006
Location: Albuquerque, NM
Posts: 4,514
Mentioned: 12 Post(s)
Tagged: 0 Thread(s)
Quoted: 1028 Post(s)
Liked 447 Times in 263 Posts
You might want to look at https://www.analyticcycling.com. They've done the work for you and you get to include all effects in all conditions without having to assume any, e.g. rolling resistance, are negligible.
asgelle is offline  
Old 12-05-06, 09:56 PM
  #5  
Senior Member?
Thread Starter
 
Join Date: Oct 2005
Location: Denver
Posts: 1,977

Bikes: orbea onix, Cervelo SLC, Specialzed Allez, Cervelo P3 Alu

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 1 Time in 1 Post
holy sheep. that website rocks. still proud of my work but thanks for the link.
brianappleby is offline  
Old 12-05-06, 10:05 PM
  #6  
Because I thought I could
 
ks1g's Avatar
 
Join Date: Dec 2004
Location: Wash DC Metro
Posts: 969

Bikes: November, Trek OCLV, Bianchi Castro Valley commuter

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
If you want to play with the formulas more on your own, get from the library or buy a copy of Bicycling Science 3rd edition from MIT Press. An entire chapter is devoted to the bicycle power equation; that plus the info on analytic cycling and a good spreadhseet or graphing program and you can spend hours at least as productively as on bf
ks1g is offline  
Old 12-06-06, 07:29 AM
  #7  
Senior Member
 
MrCjolsen's Avatar
 
Join Date: Nov 2004
Location: Davis CA
Posts: 3,959

Bikes: Surly Cross-Check, '85 Giant road bike (unrecogizable fixed-gear conversion

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Likes: 0
Liked 4 Times in 3 Posts
Analyticcycling is where I discovered that if I spent $4000 for a bike 10 pounds lighter than the one I currently ride, I would get to work a whole 14 seconds sooner.
MrCjolsen is offline  
Old 12-06-06, 07:32 AM
  #8  
pan y agua
 
merlinextraligh's Avatar
 
Join Date: Aug 2005
Location: Jacksonville
Posts: 31,273

Bikes: Willier Zero 7; Merlin Extralight; Calfee Dragonfly tandem, Calfee Adventure tandem; Cervelo P2; Motebecane Ti Fly 29er; Motebecanne Phantom Cross; Schwinn Paramount Track bike

Mentioned: 17 Post(s)
Tagged: 0 Thread(s)
Quoted: 1428 Post(s)
Liked 697 Times in 353 Posts
also take a look here https://www.kreuzotter.de/english/espeed.htm
merlinextraligh is offline  
Old 12-06-06, 08:21 AM
  #9  
Know Your Onion!
 
badkarma's Avatar
 
Join Date: Aug 2005
Location: Boston, MA
Posts: 2,011

Bikes: Kestrel Talon, Motobecane Le Champion SL

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by merlinextraligh
Yeah, that's a better resource. Upon a cursory look, the OP's equations look correct, but the full-blown equations are 2nd order ODEs that need to be numerically-integrated due to their non-linear nature - so that'll give you much more accurate results.
badkarma is offline  
Old 12-06-06, 08:28 AM
  #10  
pan y agua
 
merlinextraligh's Avatar
 
Join Date: Aug 2005
Location: Jacksonville
Posts: 31,273

Bikes: Willier Zero 7; Merlin Extralight; Calfee Dragonfly tandem, Calfee Adventure tandem; Cervelo P2; Motebecane Ti Fly 29er; Motebecanne Phantom Cross; Schwinn Paramount Track bike

Mentioned: 17 Post(s)
Tagged: 0 Thread(s)
Quoted: 1428 Post(s)
Liked 697 Times in 353 Posts
Originally Posted by badkarma
Yeah, that's a better resource. Upon a cursory look, the OP's equations look correct, but the full-blown equations are 2nd order ODEs that need to be numerically-integrated due to their non-linear nature - so that'll give you much more accurate results.

thank god there are online calculators for this. Calculus was way too many years ago.
merlinextraligh is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.