## CA 2.23 setting for wheel size.

chroot   100 kW

Posts: 1284
Joined: Nov 29 2009 4:03pm

### CA 2.23 setting for wheel size.

Hi everyone, I need your help and I have a CA 2.23 already set the wheel size in MM metric for 26" and I need change to 20" wheel. Anyone know what is the measure wheel metric in MM for 20" wheel under the advanced setting. BTW the tires is 20x2.25" in case you want know.

I looked the CA user guide manual and they showing only 2 lists = 20 x 1.75 = 1515mm, and 20 x 1 3/8" = 1615mm. Please help
Thank you Justin Lemire-Elmore - You are a HERO!

Tidalforce, Yuba Mundo V4 Cargo bike, Juiced Riders ODK V1 Cargo bike
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OlderThanDirt   1 W

Posts: 58
Joined: Dec 11 2009 6:59pm
Location: NW Washington

### Re: CA 2.23 setting for wheel size.

I like to have accurate speed and distance figures, so I measure my own personal wheel setting. This how I do it:

1. On a quiet piece of smooth road or a long driveway, measure off a 528-foot distance.

3. Set the CA distance to 0.00 and the wheel size to 1515 mm.

4. Ride your bike over the 528-foot course. Turn around and ride back; continue riding until you have covered the 528-foot distance ten times.

5. Read the CA distance. You want it to be 1.00 miles, but it likely won't be that the first time you do the test.

6. Correct the wheel size based on the CA distance readout by dividing original wheel size by the CA distance over the 5280 feet ridden. This figure is your new wheel size (for example, 1515 divided by 1.04 miles = 1457 mm; or, 1515 divided by 0.96 miles = 1578 mm).

7. Reset the CA distance to 0.00 and repeat the test with the new wheel size. Your measured distance should be much closer to the desired 1.00 miles. Repeat until you are satisfied with the accuracy.

I use a full mile for the measurement to reduce the effects of small errors. You need to use the tire pressure that you will be normally riding with and you should be on the bike (your weight will influence the wheel diameter, especially at lower pressures). If you later ride with a lower tire pressure than what you tested with, your CA speed and distance will read higher that the true speed, and lower if you ride with a higher tire pressure.

For my recumbent with a 28-406 mm smooth front tire, my final wheel circumference at 120 psi turned out to be 1476 mm.
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Stevil_Knevil   10 kW

Posts: 771
Joined: Jan 09 2007 8:32pm
Location: Up where the air is fresh and clean

### Re: CA 2.23 setting for wheel size.

I use two pieces of tape and a metric tape measure to calculate wheel diameters.

-Stick one piece of tape to the back of my hand, and the other -sideways- on the floor at the entrance of my garage.
-Line up the center of the tire valve with the back edge of the tape.
-Roll the bike straight forward until the tire valve is pointing up again, pull the other piece of tape off my hand and stick it on the floor -> with the front edge of the tape lined up with the center of the valve.

The distance between the outer edges of tape = the wheel's diameter (which I usually write on the tire's sidewall with a sharpie).
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chroot   100 kW

Posts: 1284
Joined: Nov 29 2009 4:03pm

### Re: CA 2.23 setting for wheel size.

@OlderThanDirt - thank you for the tip and I think i got it more accuracy on CA. I am comparing with my GPS mile, and mph. My tires is 58-406 coming out 1635mm with your method tip work it out.

@Stevil_Knevil - I don't have the metric meter tape. instead I went OlderThanDirt's tip method work it out.

Thank you
Thank you Justin Lemire-Elmore - You are a HERO!

Tidalforce, Yuba Mundo V4 Cargo bike, Juiced Riders ODK V1 Cargo bike
English is my secondary language - ASL (American Sign Language) is my primary.