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

Crude aero test

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

Crude aero test

Old 04-23-08, 09:47 AM
  #1  
urbanknight
In beaurocratic limbo
Thread Starter
 
urbanknight's Avatar
 
Join Date: Mar 2006
Location: Los Angeles, CA
Posts: 22,455

Bikes: Specialized Allez, K2 Razorback

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Crude aero test

A stupid move (forgetting my wheels in the wheel pit at the last crit) has me commuting on my race wheels for the week, and has lead to an interesting correlation study. My commute includes a nice descent down La Tuna Canyon in Sun Valley, CA which is about 6-7% for about 4 miles. I usually top out at 39-40 mph when wearing my zipped up wind vest (42 without a vest, but that's a whole other thread) on my training wheels, but my max speed hit 44 yesterday with the same clothing. In both cases, I stop pedaling and tuck around 38 mph.

Training wheels:
Mavic Ultegra 6600 hubs
Mavic Reflex clincher rims (20mm rim depth)
32 double butted spokes laced 3x
Continental Ultra 2000 tires with 90g tubes

Racing wheels:
Performance Forte Titans (27mm rim depth)
16 bladed spokes front laced 1x
20 bladed spokes rear laced 1x
Michelin Pro2Race tires with 70g tubes

What gave me the higher top speed?
Aerodynamics?
Rolling resistance?
Lunar cycle?
Enjoy your argument.

Last edited by urbanknight; 04-23-08 at 09:58 AM.
urbanknight is offline  
Old 04-23-08, 09:56 AM
  #2  
Creakyknees
ride lots be safe
 
Creakyknees's Avatar
 
Join Date: Jan 2007
Location: Texas
Posts: 5,223
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 12 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
it's the lower spoke count.

I'm guessing you could plug the numbers into analytic cycling and get the same answer.
Creakyknees is offline  
Old 04-23-08, 09:59 AM
  #3  
deanp
On the big ring
 
deanp's Avatar
 
Join Date: Aug 2006
Location: Lenexa, Ks
Posts: 851

Bikes: Trek 1100, Litespeed Catalyst

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Tailwind, or less headwind?
deanp is offline  
Old 04-23-08, 10:13 AM
  #4  
urbanknight
In beaurocratic limbo
Thread Starter
 
urbanknight's Avatar
 
Join Date: Mar 2006
Location: Los Angeles, CA
Posts: 22,455

Bikes: Specialized Allez, K2 Razorback

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 1 Time in 1 Post
No wind. Where I live, the wind rarely comes out until the afternoon and my commute is at 6am.
urbanknight is offline  
Old 04-23-08, 10:22 AM
  #5  
deanp
On the big ring
 
deanp's Avatar
 
Join Date: Aug 2006
Location: Lenexa, Ks
Posts: 851

Bikes: Trek 1100, Litespeed Catalyst

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Did you recalibrate your computer for the different tire size?
deanp is offline  
Old 04-23-08, 10:28 AM
  #6  
urbanknight
In beaurocratic limbo
Thread Starter
 
urbanknight's Avatar
 
Join Date: Mar 2006
Location: Los Angeles, CA
Posts: 22,455

Bikes: Specialized Allez, K2 Razorback

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 1 Time in 1 Post
^ That might have something to do with it, although not as big of a difference as I saw. Same tire size, but different brand, so I use the same setting.
urbanknight is offline  
Old 04-23-08, 10:30 AM
  #7  
KevinF
Keep on climbing
 
Join Date: Apr 2004
Location: Marlborough, Massachusetts
Posts: 2,188

Bikes: 2004 Calfee Tetra Pro

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 23 Post(s)
Likes: 0
Liked 1 Time in 1 Post
You're asking for an answer out of one data point? If I read your original post correctly, it sounds like you have exactly one descent on your race wheels that happened to be faster then your regular wheels. And you're wondering why? It could be the reduced spoke count. It could be that your water bottles were somewhat more full then on other days. It could be a slightly tighter tuck. It could be wheel bearings being in better shape. It doesn't take much reduction of air resistance or much increase in mass to make a noticeable difference in end-result speed at the velocities you're talking about. Do it a couple more times -- if you're always faster on your race wheels, then there's something worth discussing.
KevinF is offline  
Old 04-23-08, 11:21 AM
  #8  
urbanknight
In beaurocratic limbo
Thread Starter
 
urbanknight's Avatar
 
Join Date: Mar 2006
Location: Los Angeles, CA
Posts: 22,455

Bikes: Specialized Allez, K2 Razorback

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by KevinF View Post
You're asking for an answer out of one data point?
That's why I said enoy your argument It could also have something to do with me being late and more interested in arriving on time. I don't plan on making a study out of it, though, as I'd prefer not to ride my low spoke wheels with race tires on the questionable roads in the area.

Oh, and it's THAN not THEN
urbanknight is offline  
Old 04-23-08, 11:31 AM
  #9  
prendrefeu
How much does it weigh?
 
prendrefeu's Avatar
 
Join Date: Jul 2005
Location: Weight Weenie on a budget.
Posts: 3,427

Bikes: Lotus Fixed, Bianchi Virata 2004

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
No need to get snippity, now
prendrefeu is offline  
Old 04-23-08, 11:35 AM
  #10  
urbanknight
In beaurocratic limbo
Thread Starter
 
urbanknight's Avatar
 
Join Date: Mar 2006
Location: Los Angeles, CA
Posts: 22,455

Bikes: Specialized Allez, K2 Razorback

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 1 Time in 1 Post
No no, nothing like that. It's just that I'm a teacher, and I have this thing about grammar.
urbanknight is offline  
Old 04-23-08, 12:59 PM
  #11  
ri_us
Senior Member
 
Join Date: Sep 2006
Posts: 776
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Don't forget differences in air pressure.
ri_us is offline  
Old 04-23-08, 01:10 PM
  #12  
waterrockets 
Making a kilometer blurry
 
waterrockets's Avatar
 
Join Date: May 2006
Location: Austin (near TX)
Posts: 26,129

Bikes: rkwaki's porn collection

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Liked 9 Times in 4 Posts
You should try some coast-downs with both wheels, alternating randomly, and see if you get similar results. My guess is that the Titans do not cut your aerodynamic drag enough to increase your speed by 5% at 42mph.
waterrockets is offline  
Old 04-23-08, 02:15 PM
  #13  
KevinF
Keep on climbing
 
Join Date: Apr 2004
Location: Marlborough, Massachusetts
Posts: 2,188

Bikes: 2004 Calfee Tetra Pro

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 23 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by urbanknight View Post
That's why I said enoy your argument It could also have something to do with me being late and more interested in arriving on time. I don't plan on making a study out of it, though, as I'd prefer not to ride my low spoke wheels with race tires on the questionable roads in the area.

Oh, and it's THAN not THEN
Touche'. Somebody PM'ed me once and told me to change the "then" in my signature to "than" as well. Gotta start paying attention to that one!
KevinF is offline  
Old 04-23-08, 02:16 PM
  #14  
prendrefeu
How much does it weigh?
 
prendrefeu's Avatar
 
Join Date: Jul 2005
Location: Weight Weenie on a budget.
Posts: 3,427

Bikes: Lotus Fixed, Bianchi Virata 2004

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by KevinF View Post
Touche'. Somebody PM'ed me once and told me to change the "then" in my signature to "than" as well. Gotta start paying attention to that one!
It is not "Gotta," it is "I should."
prendrefeu is offline  
Old 04-23-08, 02:18 PM
  #15  
prendrefeu
How much does it weigh?
 
prendrefeu's Avatar
 
Join Date: Jul 2005
Location: Weight Weenie on a budget.
Posts: 3,427

Bikes: Lotus Fixed, Bianchi Virata 2004

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by ri_us View Post
Don't forget differences in air pressure.
Atmospheric air pressure in the Los Angeles region has not changed that dramatically enough to affect the speed of a cyclist descending La Tuna Canyon.

Or did you mean tire pressure?
prendrefeu is offline  
Old 04-23-08, 03:11 PM
  #16  
crydee
Senior Member
 
Join Date: Apr 2007
Location: Tallahassee, FL
Posts: 458
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Aren't your training wheels better then your race wheels?
crydee is offline  
Old 04-23-08, 03:16 PM
  #17  
Snow_canuck
Senior Member
 
Snow_canuck's Avatar
 
Join Date: Dec 2004
Location: Canada
Posts: 667
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by urbanknight View Post
No no, nothing like that. It's just that I'm a teacher, and I have this thing about grammar.

You must enjoy the grammar on these forums.
Snow_canuck is offline  
Old 04-23-08, 04:14 PM
  #18  
urbanknight
In beaurocratic limbo
Thread Starter
 
urbanknight's Avatar
 
Join Date: Mar 2006
Location: Los Angeles, CA
Posts: 22,455

Bikes: Specialized Allez, K2 Razorback

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by ri_us View Post
Don't forget differences in air pressure.
I generally run the same pressure in both tires. I will increase the pressure in the Continentals if I'm riding smooth roads, but this route isn't smooth.

Originally Posted by prendrefeu View Post
It is not "Gotta," it is "I should."
Actually, gotta is accepted in US vernacular and is recognized as such in the dictionary.
https://dictionary.reference.com/browse/gotta
It is not professional, but it is correct.

Originally Posted by Snow_canuck View Post
You must enjoy the grammar on these forums.
It keeps me entertained.

Originally Posted by crydee View Post
Aren't your training wheels better then your race wheels?
Yes!
(but they're lighter and more aero)
urbanknight is offline  
Old 04-23-08, 04:40 PM
  #19  
Old School
Senior Member
 
Old School's Avatar
 
Join Date: Jan 2006
Location: Camino, CA
Posts: 1,181

Bikes: Trek 5500 OCLV, Trek Fuel EX 9

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by prendrefeu View Post
Atmospheric air pressure in the Los Angeles region has not changed that dramatically enough to affect the speed of a cyclist descending La Tuna Canyon.
Agreed. Perhaps the poster meant "air density" but the real answer is decreased drag...change in wind resistance, tuck, air flow around the rider and machine, etc.

Last edited by Old School; 04-23-08 at 06:29 PM.
Old School 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


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.