hello.


so my cyclometer says to take the Milimeter measuresments of my tire and multiply them by 3.14 to get the code to put into the computer.

so, my tire says 23x622 on it, so at first I assumed that meant 23" 622MM... but 23" is actually 584.2 MM...

so which one do I put in? when I measure the inside of the wheel, from metal to metal is exactly 23"s, but when I put 584.2•π code into my computer, and measure it with a car, it is about 2 MPH off (my bike says 10mph, the car says 12.

so I'm guessing the 622 is from edge of wheel, to edge of wheel, is that the code I am supposed to put in to make it accurate?


thanks!

23x622 is the width of your tire (23mm) x the diameter of the tire at the bead (622mm). Actually, I'm not sure about that last one, but 622 is the number you're looking for.

Out of curiousity, what kind of computer are you using? Most have all this info preset so you can just choose your tire without doing any calculations.

I don't know the model or name... but I just picked it up to have an odometer until I buy a garmin, it was 20 dollars on clearance at performance.

it had like 3 tire options, and then said "if your's isn't shown, just multiply the the MM by 3.1416 and put that code in...

thanks!

The number you want is the circumference of the entire wheel, since that's the distance you travel in one wheel revolution. Measure from outside edge to outside edge, and try that. Additionally, there may be listings of what that value is for 700cx23 is in the manual for your computer. That's where I got mine.

Just to save time, my manual says the circumference of a 700cx23 is 2097mm.

thanks!

To figure it in the future (if you change sizes) take 622 (diameter of the bead edge of your rim) and add twice the size of your tire (the width and height, in this case 23 - and twice because it's on both sides of the rim) and multiply by pi

622+2(23) * pi = 2098.6

now according to what I remember of the manual, it says to multiply 622•π ... so that would be 1954, not 2098..

hmmm...which do I use?

it is an ascent Delta V

here is the manual

https://www.nashbar.com/tech/pdf_file...20Computer.pdf

The manual says to multiply the wheel diameter by pi, not the rim diameter. Wheel D = 622 + twice the height of the tire

Unless you intend to ride sans tire, you should use 2098.

I'd say ~2090 mm, since 23 most likely is 22 and the effective radius decreases even more when the tyres bear the load of the bike+rider.

thank you!

Here's the easiest and most accurate way to find your tire circumference:

Put a small piece of masking tape on your tire.

Position the tire so that the tape is at bottom-dead-center.

(If you can sit on the seat while doing this, it's even more accurate as your weight compresses the tire.)

Have an assistant put a corresponding piece of tape on the floor to line up with the tape on the tire.

Roll the bike forward in a straight line until the piece of tape on the tire is again at botton-dead-center.

Mark the floor again with another piece of tape.

Measure the distance between the two pieces of tape. Convert to mm (in * 25.4 = mm) That's the number your computer is looking for.

Sheldon Brown's chart
https://sheldonbrown.com/cyclecomputer-calibration.html
says 2097 as DevLaVaca also said so I am going with that
Tim I-trust-SB Takemoto