Road Bike, Cycling Forums banner
1 - 20 of 53 Posts

·
I ride in circles..
Joined
·
4,990 Posts
Discussion Starter · #1 ·
So I just decided to check my setting on my polar unit and my Cateye on my mtb.. My wheel sizes were a little off so I corrected them. Using tape.. a measuring tape, and a few passes per bike I got as close to perfect as I think is possible.

2045mm on the mountain bike and 2086mm on my road bike.

This taking into consideration normal tire squish from my weight.

Anyhow.. just wondering how precise you all try to be.. I know when I'm rolling next to a car and they tell me how fast I'm going we're never the same.. But within a half mile or so..

Anyhow.. Food for thought I guess?!
 

·
Registered
Joined
·
11,555 Posts
As russotto suggested, comparing your computer to a known distance on the ground is best. With a decent route-mapping program, it's easy to stake out one exact mile (or more) in your neighborhood. Because the trip mileage display error relates directly to the input number, it's also easy to correct your computer: for example, if the readout's 8% off, correcting the input number by 8% will get you dead accurate.
 

·
Back from the dead
Joined
·
20,800 Posts
Back when I had computers on my bike, I would measure out the wheel distance rather than just accept the value from the manual. It almost always came out the same, so I guess that was a waste of time. That's about as anal as I ever got. Took the computers off and I have no idea what I'm doing anymore.
 

·
duh...
Joined
·
9,749 Posts
wim said:
As russotto suggested, comparing your computer to a known distance on the ground is best. With a decent route-mapping program, it's easy to stake out one exact mile (or more) in your neighborhood. Because the trip mileage display error relates directly to the input number, it's also easy to correct your computer: for example, if the readout's 8% off, correcting the input number by 8% will get you dead accurate.


this assumes that the rider rides a dead straight line... any little wavering adds distance and decreases accuracy of the measurement
 

·
duh...
Joined
·
9,749 Posts
mohair_chair said:
Back when I had computers on my bike, I would measure out the wheel distance rather than just accept the value from the manual. It almost always came out the same, so I guess that was a waste of time. That's about as anal as I ever got. Took the computers off and I have no idea what I'm doing anymore.


don't the directions of most computers have directions for this 'roll out' technique for calibration? of course, the truly anal will make sure tire pressures are consistent at the time of roll-out and at all times riding
 

·
Cannot bench own weight
Joined
·
4,298 Posts
I have Garmin Edge 305 and I let it figure out wheel size. I think it does it with combination of wheel revolutions + GPS. And I think it's pretty goddamn accurate as on of my favorite loops is within .01 distance wise every time I ride it, and if that's not good enough, my friend who has an Edge 705 and rides with me comes up with the same measurement.

So yea, I think GPS based is as good as it gets.
 

·
Registered
Joined
·
3,126 Posts
I tried to gauge using the car. Then I realized that the +2 tire/wheel combo had a diameter .5" smaller than stock and accounting for tire wear...I was way lost. Not very concerned so long as it doesn't give me a minus reading. :)
 

·
Registered
Joined
·
21,832 Posts
The measured mile

russotto said:
One of the trails near me has some measured mile markers, so I adjusted it based on those. And I had previously checked the mile markers with a GPS, so I guess that's getting pretty anal.
I don't use a computer, but for my wife's computer, we calibrated it against 20 surveyed miles on our local rail trail.
 

·
Registered
Joined
·
61 Posts
Lol this topic kills me. I don't get why people care so much about a distance of probably .1 mi over 40 mi. And second off you use that same computer when you ride so its not like it matters if you're trying to be consistent over a long period. If you ride what your compy says is 20 miles one day, you'll ride that same distance the next time you ride it too. It's all relative my friends.
 

·
Batteries not required
Joined
·
1,118 Posts
Einstruzende said:
I have Garmin Edge 305 and I let it figure out wheel size. I think it does it with combination of wheel revolutions + GPS. And I think it's pretty goddamn accurate as on of my favorite loops is within .01 distance wise every time I ride it, and if that's not good enough, my friend who has an Edge 705 and rides with me comes up with the same measurement.

So yea, I think GPS based is as good as it gets.
Agree 100%. I have an edge 305.
 
1 - 20 of 53 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top