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

Cateye Wheel Calcuations

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

Cateye Wheel Calcuations

Old 07-28-19, 05:01 AM
  #1  
nomadmax 
Senior Member
Thread Starter
 
Join Date: Jun 2018
Location: SW Ohio
Posts: 922
Mentioned: 60 Post(s)
Tagged: 0 Thread(s)
Quoted: 403 Post(s)
Liked 234 Times in 131 Posts
Cateye Wheel Calcuations

This year I upgraded from a watch strapped around some pipe insulation on my handlebars to a Cateye bike computer. Recently, I've ridden with folks who have GPS based cycle computers and in comparing the data I'm always 2 or 3 tenths higher in mileage. I intend to change the input number and believe if the number for 700x25 is 2105 and 2096 for 700x23 then I should bump the number to 2110 or so to get it closer to accurate. Does increasing the number decrease mph and miles or is it the other way?
nomadmax is offline  
Old 07-28-19, 08:46 AM
  #2  
Weakbikr
Senior Member
 
Join Date: May 2018
Posts: 243
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 86 Post(s)
Likes: 0
Liked 28 Times in 9 Posts
I had the same problem, my numbers never match with gps, close but not the same. If my thinking correctly, bigger numbers slow it down, smaller numbers speed it up. Now my suggestion is air the tires up to the pressure you ride. Make a mark on the side wall on the rear tire. Make a mark on the floor. Have a friend help you. Line the mark on the tire to the mark on the floor. Sit on the bike and roll forward until the mark on the tire makes one revolution. Then make a mark on the floor. Measure the two points and input the measurement in your computer. Also save that measurement. It's still not going to be the same as gps but you know your measurement is now correct for your setup. There are videos that will show you how if I wasn't clear on the process. Hope that helps.
Weakbikr is offline  
Old 07-28-19, 08:48 AM
  #3  
Weakbikr
Senior Member
 
Join Date: May 2018
Posts: 243
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 86 Post(s)
Likes: 0
Liked 28 Times in 9 Posts
Sorry I went on, short answer is yes increasing the number will decrease mileage.
Weakbikr is offline  
Old 07-28-19, 09:00 AM
  #4  
waters60
Senior Member
 
waters60's Avatar
 
Join Date: Sep 2010
Posts: 307
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 60 Post(s)
Likes: 0
Liked 4 Times in 4 Posts
Roll it out to get your exact number, if Cateye has a place ti put that number.
waters60 is offline  
Likes For waters60:
Old 07-28-19, 12:12 PM
  #5  
deacon mark
Senior Member
 
Join Date: Sep 2009
Posts: 1,492

Bikes: Habanero Titanium Team Nuevo

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 197 Post(s)
Liked 10 Times in 7 Posts
Cateye does have place you just input the wheel roll out in mm. On my Habanero and Wilier they
are both 2093. I use that number and rarely are total amount from my Garmin 910 much different. The difference is less than 1/2 of 1 percent and I have done 50 mile rides and be like 50.25 and 50.35.

The measure the same thing but differently, will not be exact but i bet mine is down to less than 10 feet in a mile.
deacon mark is offline  
Old 07-29-19, 05:26 AM
  #6  
nomadmax 
Senior Member
Thread Starter
 
Join Date: Jun 2018
Location: SW Ohio
Posts: 922
Mentioned: 60 Post(s)
Tagged: 0 Thread(s)
Quoted: 403 Post(s)
Liked 234 Times in 131 Posts
Thanks all!
nomadmax is offline  
Old 07-29-19, 08:15 AM
  #7  
BCDrums
Recreational Road Cyclist
 
BCDrums's Avatar
 
Join Date: Sep 2013
Location: MetroWest, Mass.
Posts: 163

Bikes: 1990 Peter Mooney road bike

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 68 Post(s)
Liked 19 Times in 14 Posts
Originally Posted by nomadmax View Post
Recently, I've ridden with folks who have GPS based cycle computers and in comparing the data I'm always 2 or 3 tenths higher in mileage. I intend to change the input number and believe if the number for 700x25 is 2105 and 2096 for 700x23 then I should bump the number to 2110 or so to get it closer to accurate.
I use a Cateye and I compare its recorded distance to the distance I get on Ride with GPS, and at first they did not match—the Cateye was higher. So I began to decrease the circumference number in the Cateye by 5mm at a time until they were close, but still they never match. Finally I decided there was a little bit of deviance in both.

RwGPS shows a distance in tenths, whereas the Cateye gives it in hundredths. But if I switch to the RwGPS Edit Ride page, and Show Metrics, it gives a number in ten-thousandths, e.g. XX.xxxx. I find it hard to believe that is accurate; a ten-thousandth of a mile is 5 feet.
BCDrums is offline  
Old 07-29-19, 08:28 AM
  #8  
nomadmax 
Senior Member
Thread Starter
 
Join Date: Jun 2018
Location: SW Ohio
Posts: 922
Mentioned: 60 Post(s)
Tagged: 0 Thread(s)
Quoted: 403 Post(s)
Liked 234 Times in 131 Posts
Originally Posted by BCDrums View Post
I use a Cateye and I compare its recorded distance to the distance I get on Ride with GPS, and at first they did not match—the Cateye was higher. So I began to decrease the circumference number in the Cateye by 5mm at a time until they were close, but still they never match. Finally I decided there was a little bit of deviance in both.

RwGPS shows a distance in tenths, whereas the Cateye gives it in hundredths. But if I switch to the RwGPS Edit Ride page, and Show Metrics, it gives a number in ten-thousandths, e.g. XX.xxxx. I find it hard to believe that is accurate; a ten-thousandth of a mile is 5 feet.
Wouldn't decreasing the circumference number increase the error even more if the error was optimistic ?
nomadmax is offline  
Old 07-29-19, 08:33 AM
  #9  
BCDrums
Recreational Road Cyclist
 
BCDrums's Avatar
 
Join Date: Sep 2013
Location: MetroWest, Mass.
Posts: 163

Bikes: 1990 Peter Mooney road bike

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 68 Post(s)
Liked 19 Times in 14 Posts
Originally Posted by nomadmax View Post
Wouldn't decreasing the circumference number increase the error even more if the error was optimistic ?
If by optimistic, you mean higher, then no. Decreasing the circumference will give a shorter total distance. Distance is calculated by revolutions x circumference, so the smaller the circumference, the shorter the distance.

I like that use of optimistic, though.
BCDrums is offline  
Likes For BCDrums:
Old 07-29-19, 08:37 AM
  #10  
nomadmax 
Senior Member
Thread Starter
 
Join Date: Jun 2018
Location: SW Ohio
Posts: 922
Mentioned: 60 Post(s)
Tagged: 0 Thread(s)
Quoted: 403 Post(s)
Liked 234 Times in 131 Posts
Originally Posted by BCDrums View Post
If by optimistic, you mean higher, then no. Decreasing the circumference will give a shorter total distance. Distance is calculated by revolutions x circumference, so the smaller the circumference, the shorter the distance.

I like that use of optimistic, though.
Got it. so in the case of the OP, an optimistic (too high) reading of mileage @2105, 2100 would be moving toward correction, correct?

There are a few things I'm good at, numbers, shoes on or off, is not one of them
nomadmax is offline  
Old 07-29-19, 08:40 AM
  #11  
BCDrums
Recreational Road Cyclist
 
BCDrums's Avatar
 
Join Date: Sep 2013
Location: MetroWest, Mass.
Posts: 163

Bikes: 1990 Peter Mooney road bike

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 68 Post(s)
Liked 19 Times in 14 Posts
Originally Posted by nomadmax View Post
Got it. so in the case of the OP, an optimistic (too high) reading of mileage @2105, 2100 would be moving toward correction, correct?
Yes, that is correct.

There are a few things I'm good at, numbers, shoes on or off, is not one of them
I share your pain!
BCDrums is offline  
Old 07-29-19, 08:44 AM
  #12  
jadocs
Senior Member
 
jadocs's Avatar
 
Join Date: Jul 2018
Location: USA
Posts: 872

Bikes: Litespeed T2 Disc, Fondirest P4 Carbon, Fuji Cross 2.0, Specialized Fatboy

Mentioned: 18 Post(s)
Tagged: 0 Thread(s)
Quoted: 362 Post(s)
Liked 90 Times in 70 Posts
I used to measure out my tire and input manually on my old computer. I marked the tire with chalk and actually sat on the bike to roll it out. I figured the weight of my body on the bike would compress the tire and I wanted to get the most accurate measurement I could.
jadocs is offline  
Old 07-29-19, 08:46 AM
  #13  
nomadmax 
Senior Member
Thread Starter
 
Join Date: Jun 2018
Location: SW Ohio
Posts: 922
Mentioned: 60 Post(s)
Tagged: 0 Thread(s)
Quoted: 403 Post(s)
Liked 234 Times in 131 Posts
Here's the saddest part of all. In a year when the battery goes dead, I'll do a search, find my own post and re-learn what I know now
nomadmax is offline  
Old 07-29-19, 09:19 AM
  #14  
BCDrums
Recreational Road Cyclist
 
BCDrums's Avatar
 
Join Date: Sep 2013
Location: MetroWest, Mass.
Posts: 163

Bikes: 1990 Peter Mooney road bike

Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 68 Post(s)
Liked 19 Times in 14 Posts
Originally Posted by jadocs View Post
I used to measure out my tire and input manually on my old computer. I marked the tire with chalk and actually sat on the bike to roll it out. I figured the weight of my body on the bike would compress the tire and I wanted to get the most accurate measurement I could.
I have done that too. It's probably as accurate a number as you'll get for the computer. But I decided I wanted to get RwGPS and the Cateye to match, so I fiddled the Cateye number until it (mostly) did.

Last edited by BCDrums; 07-29-19 at 11:06 AM.
BCDrums is offline  
Old 07-29-19, 10:30 AM
  #15  
Abe_Froman
Senior Member
 
Abe_Froman's Avatar
 
Join Date: Aug 2016
Location: Chicago
Posts: 2,559

Bikes: Marin Four Corners, 1960's Schwinn Racer in middle of restoration, mid 70s Motobecane Grand Touring, various other heaps.

Mentioned: 76 Post(s)
Tagged: 0 Thread(s)
Quoted: 9341 Post(s)
Liked 50 Times in 44 Posts
Somebody earlier had this incorrect. Larger input tire circumference will result in the cateye showing higher mph and distance covered, NOT the other way around.

If cateye is overshooting the mph and distance, you want to lower the input tire circumference. All it is doing is taking wheel revolutions x wheel circumference to get your distance traveled. If you reduce tire size, you reduce distance.
Abe_Froman is offline  
Likes For Abe_Froman:

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

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