Advertise on Bikeforums.net



User Tag List

Results 1 to 17 of 17

Thread: Tires & inches

  1. #1
    Newbie
    Join Date
    Mar 2014
    Posts
    3
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Tires & inches

    Hello, I just bought a Bike Computer but I've stuck at the part with the inches. My tire has so many numbers.. But i've no idea what all these mean. If you could help me by telling me which of that is the inches.. I googled it but I didn't find a solution..
    So, here is the numbers:
    Pressure 40-65PSI 2.8-4.6kgf/cm2 280-460 KPa (56-559) 28x1.95 k-849-010

  2. #2
    Senior Member
    Join Date
    Jul 2011
    Location
    Champlin, MN
    My Bikes
    1994 Mongoose Switchback, 1983 Schwinn Voyageur SP, Cheap unnamed ssfg road bike
    Posts
    136
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    28x1.95. If your computer doesn't have that size in the menu, you'll have to look at the book for manually entering, and (for the computers I've owned) measure the circumference and manually enter that number.

  3. #3
    Senior Member rumrunn6's Avatar
    Join Date
    Jul 2008
    Location
    25 miles northwest of Boston
    My Bikes
    Bottecchia Sprint
    Posts
    11,962
    Mentioned
    5 Post(s)
    Tagged
    0 Thread(s)
    Sheldon Brown has a bike computer page that might help

    Harris Cyclery articles about Cyclecomputers by Sheldon Brown
    cycling is like baseball ~ it doesn't take much to make it interesting

  4. #4
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    38,884
    Mentioned
    20 Post(s)
    Tagged
    0 Thread(s)
    some allow a wheel radius that you measure, to be input.

  5. #5
    The Improbable Bulk Little Darwin's Avatar
    Join Date
    Jul 2005
    Location
    Wilkes-Barre, PA
    My Bikes
    Many
    Posts
    7,242
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Something is wrong...

    Looking at 56-559

    559 = 26"
    56 = width (in mm) or about 2.2 inches

    So, I would expect to see something like 26 x 2.2

    I have noticed that some tire manufacturers are confusing things by applying measurements, and who knows, theirs may be more sensible, but if you look at Sheldon's site noted above, you'll see we already have enough different ways to get confused.

    However, the 56-559 should be the most "standard" thing related to size in what you show.
    Slow Ride Cyclists of NEPA

    People do not seem to realize that their opinion of the world is also a confession of character.
    - Ralph Waldo Emerson

  6. #6
    Life is good RonH's Avatar
    Join Date
    Jan 2001
    Location
    Between Lecanto and Hernando Florida, 6 miles west of the Withlacoochee Trail
    My Bikes
    I've had several since 1999 but have settled on my beloved 2001 Litespeed Tuscany and my latest, a 2013 Cannondale CAAD 10.
    Posts
    13,517
    Mentioned
    3 Post(s)
    Tagged
    0 Thread(s)
    The manual/instructions that came with the computer should have a list with tire sizes and the corresponding number you'll need to enter into the computer when setting it up.

    If you don't have the manual/instructions they're probably online. What computer did you get? Brand and model.
    My bikes --> 2001 Litespeed Tuscany---2013 Cannondale CAAD 10 2 (5) "Racing Edition"

    Life is like a 10-speed bicycle. Most of us have gears we never use. ~ Charles Schultz

  7. #7
    Newbie
    Join Date
    Mar 2014
    Posts
    3
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Yes, I have the direction paper and it says that I can calculate the tyre circumference by multiplying my tire diameter by 3.1416
    And then there's a list of mosto common cicle tyres circumferences..

    20'' = 1598mm
    22'' = 1759mm
    24'' = 1916mm
    26'' (650A) = 2073mm etc.

    But what I should multiply? My computer accept 3 numbers to fill it. The 2 first are big and the third smaller.
    Last edited by popcorns; 03-26-14 at 01:22 PM.

  8. #8
    The Improbable Bulk Little Darwin's Avatar
    Join Date
    Jul 2005
    Location
    Wilkes-Barre, PA
    My Bikes
    Many
    Posts
    7,242
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    I searched for: circumference of 56-559 tire

    And found this: http://202.215.251.86/data/resources...e_chart_v2.pdf

    And it lists 2068 for 55-559 and 2070 for 57-559, so you can use 2069
    Slow Ride Cyclists of NEPA

    People do not seem to realize that their opinion of the world is also a confession of character.
    - Ralph Waldo Emerson

  9. #9
    Newbie
    Join Date
    Mar 2014
    Posts
    3
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Little Darwin View Post
    I searched for: circumference of 56-559 tire

    And found this: http://202.215.251.86/data/resources...e_chart_v2.pdf

    And it lists 2068 for 55-559 and 2070 for 57-559, so you can use 2069
    Aw thank you very much!!
    Thank you all for your help!

  10. #10
    Senior Member Wilfred Laurier's Avatar
    Join Date
    Feb 2013
    Posts
    1,340
    Mentioned
    3 Post(s)
    Tagged
    0 Thread(s)
    the easiest and most accurate way to figure out your wheel circumference
    is a roll out test

    put the bike with the valve on the front wheel at the bottom of the rotation
    and put a mark on the ground beside it
    then roll the bike forward until the valve is at the bottom again and mark that point
    then measure between the two marks

    this is most accurate if you are sitting on the bike during this test
    but i dont think it makes a noticeable difference

  11. #11
    rebmeM roineS JanMM's Avatar
    Join Date
    Jan 2006
    Location
    Indiana
    My Bikes
    RANS V3, RANS V-Rex, RANS Screamer
    Posts
    11,422
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Wilfred Laurier View Post
    the easiest and most accurate way to figure out your wheel circumference
    is a roll out test

    put the bike with the valve on the front wheel at the bottom of the rotation
    and put a mark on the ground beside it
    then roll the bike forward until the valve is at the bottom again and mark that point
    then measure between the two marks

    this is most accurate if you are sitting on the bike during this test
    but i dont think it makes a noticeable difference
    +1 roll it out to be sure
    RANS V3 (steel), RANS V-Rex, RANS Screamer

  12. #12
    Senior Member rumrunn6's Avatar
    Join Date
    Jul 2008
    Location
    25 miles northwest of Boston
    My Bikes
    Bottecchia Sprint
    Posts
    11,962
    Mentioned
    5 Post(s)
    Tagged
    0 Thread(s)
    you might have to hunt for a metric tape measure but they are out there
    cycling is like baseball ~ it doesn't take much to make it interesting

  13. #13
    The Improbable Bulk Little Darwin's Avatar
    Join Date
    Jul 2005
    Location
    Wilkes-Barre, PA
    My Bikes
    Many
    Posts
    7,242
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    A difference of a few mm is not a big deal for most riders. Assuming a true measurement of 2000 mm entering any random number between 1980 and 2020 is less than 1% off....

    However, if accuracy is critical, you should measure the rollout of several revolutions, while sitting on the bike with any equipment and accessories you normally carry. If you do as an example 7 revolutions, measure total rollout to the nearest mm and divide by 7. To ensure even closer accuracy, this should be done at the usual riding speed on the usual surface you ride, and should be redone periodically to allow for tire wear.

    Then after that, you should still realize that it is just an estimate, since a bicycle trip involves a little side to side motion which will reduce accuracy.
    Slow Ride Cyclists of NEPA

    People do not seem to realize that their opinion of the world is also a confession of character.
    - Ralph Waldo Emerson

  14. #14
    coprolite fietsbob's Avatar
    Join Date
    Jun 2010
    Location
    NW,Oregon Coast
    My Bikes
    7
    Posts
    38,884
    Mentioned
    20 Post(s)
    Tagged
    0 Thread(s)
    Its all about circumference. all the computer does is count rotations ..

    measure .. mark the sidewalk when the valve stem is at the bottom

    roll the wheel once . ideally you are sitting on it. to compress the tire.

    and then measure the difference between the 2 marks on the sidewalk .


    you can ride thru a dog poo-pile and then the next time that deposit on the tire
    marks the sidewalk again would do the same..

  15. #15
    Senior Member BlazingPedals's Avatar
    Join Date
    Dec 2004
    Location
    Middle of da Mitten
    My Bikes
    Trek 7500, RANS V-Rex, Optima Baron, Velokraft NoCom, M-5 Carbon Highracer, homebuilt recumbent
    Posts
    7,020
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    You've already gotten the correct answers. 56x559 is a regular 26" mountain bike tire, with a width of 56mm or, actually, 2.2 inches. A roll-out will be the most accurate method of determining the actual circumference, which is what the bike computer will need. Most roadies try to get within 1%. IMHO being 10% off would render the speedo almost useless; but maybe for a mountain bike it's all you need, which can be done by calculation.

    The wheel's height will be the diameter of the rim plus twice the diameter (roughly, although different rim widths will affect that measurement.) So, 559mm + 112mm = 671mm. The circumference is that times pi, or 671 X 3.14 = 2107 (the computer won't accept fractions, even if tenths of millimeters would be too small to measure with a tape.)

    Where the accurate measurements become a problem is in tire deflection, which depends on pressure and load. A properly-inflated tire will compress by about 10-15% with the rider on it. Even more than that if you run your tires soft for extra traction or flotation. Not only can it can be tough to get an accurate roll-out unless you have someone helping you; if your tire pressure varies, so will your speedo's accuracy.

  16. #16
    Senior Member
    Join Date
    Mar 2012
    Location
    southeastern PA - a mile west of Philadelphia
    Posts
    264
    Mentioned
    0 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by popcorns View Post
    Hello, I just bought a Bike Computer but I've stuck at the part with the inches. My tire has so many numbers.. But i've no idea what all these mean. If you could help me by telling me which of that is the inches.. I googled it but I didn't find a solution..
    So, here is the numbers:
    Pressure 40-65PSI 2.8-4.6kgf/cm2 280-460 KPa (56-559) 28x1.95 k-849-010
    Simply measure the diameter of your rear tire in inches, multiply that diameter by 25.4, then multiply that by pi (which is 3.141592653) and it will derive the required 4 digits to enter into your bicycle computer.

  17. #17
    Elmira>Taiwan>Elmira flatlander_48's Avatar
    Join Date
    Oct 2004
    Location
    Elmira, NY
    My Bikes
    2005 Ritchey BreakAway (full Chorus 11), 2001 Gary Fisher Tassajara mountain bike (sold), 2004 Giant TRC 2 road bike (sold)
    Posts
    1,272
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by popcorns View Post
    Pressure 40-65PSI 2.8-4.6kgf/cm2 280-460 KPa
    These are all various measures of Inflation Pressure:

    PSI = Pounds/Sq. Inch
    KGF/CM2 = Kilograms of Force/Sq. Centimeter
    KPa = KiloPascals
    2005 Ritchey BreakAway (steel)
    Full Campagnolo double compact drivetrain - Chorus 11sp
    (50, 34 & 12-29)
    Proton wheels
    Cateye CC-TR300TW V3
    Ritchey fork, stem, headset, bars and seatpost
    Fizik Gobi saddle and bar tape
    BeBop Pedals

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •