Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Clydesdales/Athenas (200+ lb / 91+ kg) Looking to lose that spare tire? Ideal weight 200+? Frustrated being a large cyclist in a sport geared for the ultra-light? Learn about the bikes and parts that can take the abuse of a heavier cyclist, how to keep your body going while losing the weight, and get support from others who've been successful.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 04-16-12, 07:46 AM   #1
ccrow
Member
Thread Starter
 
ccrow's Avatar
 
Join Date: Mar 2012
Location: Stillwater, OK
Bikes: 05' Gary Fisher Nirvana
Posts: 34
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Tracking Mileage

So, i'm just getting started and I have an expensive ($20) computer on my bike. I thought I had it set up correctly, followed all the instructions, measured the circumference of my tires with me on the bike. I compared it's calculated distance against Strava (Iphone GPS app) and they don't match up. I think they were off 3/10 over a 10.5 mile ride.

I'm sure I'm over scrutinizing at 3/10 difference in 10 miles, but I'm not sure which one would be correct.

On the mathematical side, I'm not completely sure I have my tire circumference correct. When I compared my measurement to the suggested measurement in the instructions for 700x32 tires mine was a little less. I figured it was do to compression of me being on it. Admittedly I don't know if a few mm's would be throwing it off that much.
ccrow is offline   Reply With Quote
Old 04-16-12, 08:22 AM   #2
indyfabz
Senior Member
 
Join Date: Jan 2010
Bikes:
Posts: 9,367
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 370 Post(s)
Quote:
Originally Posted by ccrow View Post
I'm sure I'm over scrutinizing at 3/10 difference in 10 miles, but I'm not sure which one would be correct.
So the difference is 1 mile vs. 1.03 miles. I don't think that's a meaningful difference or one you need to worry about.
indyfabz is offline   Reply With Quote
Old 04-16-12, 08:25 AM   #3
TrojanHorse 
SuperGimp
 
TrojanHorse's Avatar
 
Join Date: Mar 2010
Location: Whittier, CA
Bikes: Specialized Roubaix
Posts: 11,173
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 85 Post(s)
No, it would be 10.5 vs 10.2 which is a bit significant.

Just go with your GPS app and use the computer for real time input while riding. Every now and then you'll get crazy results there too though, like a little quantum leap.
TrojanHorse is offline   Reply With Quote
Old 04-16-12, 08:40 AM   #4
vesteroid
Climbers Apprentice
 
vesteroid's Avatar
 
Join Date: Feb 2012
Bikes:
Posts: 1,608
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
It's a 3% difference any way you slice it.

No more or less significant, just more or less miles different depending on the amount miles ridden.
vesteroid is offline   Reply With Quote
Old 04-16-12, 09:22 AM   #5
volosong 
Senior Member
 
volosong's Avatar
 
Join Date: Apr 2011
Location: Antelope Valley, SoCal
Bikes:
Posts: 2,714
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
An easy way to measure a wheel is put the bike on a sidewalk with the valve stem in the bottom position on a crack. Roll the bike forward until the valve stem is again in the bottom position. Then just measure with a tape measure, (and convert to cm/mm if you don't have a metric tape). Change in distance due to tire deformation of a rider's weight should not be significant.
__________________
Deut 6:5

---

"Ha ha! You fool! You fell victim to one of the classic blunders - The most famous of which is 'never get involved in a land war in Asia'".
- Vizzini during his "battle of wits" with the Man in Black
volosong is offline   Reply With Quote
Old 04-16-12, 09:42 AM   #6
Seattle Forrest
Senior Member
 
Seattle Forrest's Avatar
 
Join Date: Mar 2010
Location: Seattle, WA
Bikes:
Posts: 13,704
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 314 Post(s)
I don't think many people actually measure the circumference of their tire; it's usually a roll-out test where you put a drop of paint on the tire, then roll the wheel a few times, and take the average distance between spots on the road.

Your bike computer is almost surely more accurate than GPS, just based on the way each system works.
Seattle Forrest is offline   Reply With Quote
Old 04-16-12, 11:59 AM   #7
avance
Senior Member
 
Join Date: Mar 2012
Location: Maryville, IL
Bikes: 2012 Specialized Roubaix
Posts: 174
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I use multiple apps and a computer on my bike and all give me different results, but within 1-1.5% of each other. Strava rounds up.

I use Strava, Endomondo, and mapmyride(sometimes). Strava and endomondo tend to be closer together then my bike computer.
avance is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

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



All times are GMT -6. The time now is 09:21 PM.