# Computer for 39er?

Discussion in 'Cycling Equipment' started by Cbtbakkes, May 14, 2018.

1. ### Cbtbakkes New Member

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I've been searching the last couple summers for a bike computer for 39" wheels with no luck. Nashbar & Performance both say they do not have any that will work ans the internet has been no help. Does anyone know of one that does work?

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2. ### alfeng Well-Known Member

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You probably mean 29er ...

The rims are 700c by (probably) 19-to-22 ...

Regardless, your bike's future computer will be set to the tire's circumference which you will have to determine-or-calculate.

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3. ### Cbtbakkes New Member

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Yup...fat fingers and I can't figure out how to edit it.

All my old computers have settings for each tire size made. I'm told there are none for 29" tires. Describe calculate please? Thr size is on the side of the tire...

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4. ### alfeng Well-Known Member

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There are two ways to determine the circumference of your 29er tires which should theoretically yield the same result:

From an identifiable spot on a flat surface, begin with an inflated wheel with the valve stem at the 6 o'clock position ...

Roll the wheel along the surface until the valve stem is once again at the 6 o'clock position ...

Mark the second spot ...

Measure ...

And, consider repeating the process!?!
OR, "measure" the distance from the center of the wheel's axle to the outside edge of the tire AND mulitply that number by 6.2832 (2 x PI) ...

If you measure in inches, then you'll want to multiply the result by 2.54 to get the value for the bicycle computer.​

YOUR tire inflation will impact the ACTUAL circumference!

Ballparking the value, if you have 700x53 tires, then you would have something like:​

(311 + 53) x 6.2832 == 2287

(311 + 51 [for off-road inflation]) x 6.2832 == 2275
Some cycling computers let you input more than one tire size; so, if the one you end up with has that option then you may want to take advantage of that option as needed.​

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Last edited: May 15, 2018
5. ### Cbtbakkes New Member

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Thanks. Sounds like lit of bother for something that used to be in our computers/odometers though

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6. ### Cbtbakkes New Member

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Sounds like Cateye is the way to go.

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7. ### phillman5 New Member

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I think this says something about the knowledge of Nashbar & Performance.

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8. ### Cbtbakkes New Member

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Nashbat finally said that Cateye's were the only brand they carry with settings for 29ers...

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