Computer for 39er?

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

  1. Cbtbakkes

    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

    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.
     
  3. Cbtbakkes

    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...
     
  4. alfeng

    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.​
     
    #4 alfeng, May 15, 2018
    Last edited: May 15, 2018
  5. Cbtbakkes

    Cbtbakkes New Member

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

    Cbtbakkes New Member

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    Sounds like Cateye is the way to go.
     
  7. phillman5

    phillman5 New Member

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

    Cbtbakkes New Member

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

    Chuckabutty Member

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    I've been using Cateye Padrones on two bikes, and as Alfeng said, you need to measure the wheel's circumference. I did it the way he said, then converted the inches to millimeters. The number of millimeters is the number you program into the computer. It's easy once you see how it's done. It can be a bit frustrating learning how to set the computer despite the good diagrams. Perhaps inflate your tires to your normal running pressure before you measure the circumference. I found that both my bikes with the Cateye computers agree with one another over a set distance. One of them has 26" x 4" rims but measure about 29" in diameter. My other bike has 700C wheels.
     
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