any one using a bike computer?

[rangerbrown]

i have a really good one, and i am trying to get mounted. i wanted it for a few reasons one being that my trip meter cant be reset any more and i would like to have a clock, and a more accurate speed reading.


whats the average tire diameter total so that i can get a number to program into it.

[TragicImage]

easiest way for tire diametere is to mark a white dot on the top of your tire with a large glob of White out, and roll one fully revolution.

measure Mark to Mark on the ground....

This is your roll out distance.

[annguyen1981]

TRAGICIMAGE:  I do believe that's the circumference (C)...

But you could take that measurement and find the actual diameter...

C = 3.14 x r^2
The squareroot of (C / 3.14) times 2

This will give you the diameter

[TragicImage]

uhm, not to step on any toes......


But if you read the owners manual, it actually tells you to do that.

However, if you have something like the Specialized Pro computer... it has pre-sets for various common roll outs, then a "measured" roll out, which you need to enter in metric units.  Centimeters I believe, but each one is different.


How do I know?  I was the manager of a Bike Shop of 4 years....

[annguyen1981]

I replied based on RangerBrown's post:

whats the average tire diameter

That's all the info I based that on.

[TragicImage]

its cool....


It actually changes as you use the bike, as tread wears, you can actually lose several centimeters of circumference.

[annguyen1981]

That's true, but do you think "several centimeters" is a bit on the extreme side?  I'm too lazy to go out and measure the tread depth (plus, my tires aren't new).  I'm estimating maybe a centimeter at most?  I'm not sure on this.  But either way, it shouldn't affect the speedo any more than the effect on the factory speedo IMO.

[TragicImage]

well... reduce the radius of a circle by 1 centimeter... showing 1 centimeter of wear on the tread...


And calculate circumference between the original, and the reduced....

[rangerbrown]

well it says to get the diameter and then X buy 3.14 or what ever, i don't have the number in front of me. the diameter i need is for the 110/70 tire

[annguyen1981]

well it says to get the diameter and then X buy 3.14 or what ever, i don't have the number in front of me. the diameter i need is for the 110/70 tire

Strange...  I can't figure out what Pi x Diameter would signify...

Oh well

[corndog67]

Circumference.  Use 3.1416, you'll get a more accurate measurement.

[annguyen1981]

Sorry guys.  I remembered the equation totally wrong.  I remembered the "2" in the wrong spot with the wrong action.

The correct equation is:


RangerBrown:  Use TragicImage's method.  It's the MOST accurate.

TragicImage:  Sorry bout that.

[EdChen]

(17 * 25.4) + (110 * .7) = 508.8 mm = diameter

depth  (6 / 32) * 25.4 = 4.7625 mm

lost 3 mm *2 = 6 mm

502.8 mm / 508.8 mm

(1 - (502.8 / 508.) * 100 = 1.17924528%

[annguyen1981]

Nice post.  But it's only numbers.  It only makes sense to math geeks like you and me.

Well, I can figure out half of it kinda.

[NiceGuysFinishLast]

Hey.. way to exclude me An.. I'm a math geek too!

[rangerbrown]

I DON'T UNDERSTAND!!!!!























yes it do thanks man should make this easy when i get it all working on Monday.
trying to get the truck and bike ready for the big
deals gap meet

[rangerbrown]

ok got it on and working.

a few problems

1. wheel needs balance (bad  )
2. it reads 55 when i am at 70-75  when i want even faster it got to the point were the vibratios was so bad it couldn't read any higher than 60 mph.

so i will take the wheel off and run it to the shop after work tomarrow and then try again.

i will need to play with the sizing again as well.

[rangerbrown]

tire size is

585.724 mm * 3.1416 = 1840


1840 is the size i will use for the computer. the other one was off