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Let's talk Tyre basics... =) (Q's here)

Discussion in 'Technical and Troubleshooting Torque' started by Grunge, Apr 28, 2008.

  1. Hey guys,

    Just thought I'd start a thread on tyres and basics of it, as I have a question on my mind that seems silly that prolly everyone knows. :]

    This relates to sizing.
    As you know they usually have it numbered as 180/55/17"

    I know the first last one relates to sizing to fit your wheels.
    How does the first and the last numbers work?

    I mean, with my current rear tyres are like, 180/65/17"
    Would I be able to fit these tyres on what I've got?
    And how would it affect the bike?

    Just a quick Q on that. Thanks for any help guys.
  2. 180 relates to the width of the tyre in mm.
    55 is the aspect ratio of the side of the tyre to the width of the tyre.
  3. 180 is the width of the tyre (if it was flat) and 55 is the profile, or height the tyre sticks out from the rim at its highest point.
  4. Cejay's right... Here's a full chart for how to read a metzeler tyre:

    1. Metzeler = Brand name
    2. E3 = code identifying the country where the tyre has been homologated
    3. 75R-xzy = ECE homologation code
    4. Max. load … = specification of the max permitted load on the tyre at the specified inflated pressure in cold conditions
    5. DOT = Department Of Transportation. This indicates that the tyre conforms the regulations issued by the transportations dept's in USA and Canada
    6. 3403 = the first 2 numbers identify the week (34 th ) and the last 2 the year (2003) in which the tyre was produced
    7. Tread: = specification of the number of plies used for carcass and belt and the correspondent material used
    8. Roadtec Z6 = Product line name
    9. A = special version code. This letter identifies a special construction of the tyre, dedicated to a specific bike
    10. Steel radial = Specification of construction typology
    11. 180 = nominal section width in mm
    12. 55 = aspect ratio: this percentage value identifies the ratio between tyre section height and nominal width. This is not indicated when the section width is expressed in inches
    13. ZR = code identifying tyre construction technology ("-": bias, "B": bias-belted, "R":radial)
    14. 17 = nominal rim diameter size expressed in inches
    15. M/C = Motorcycle in abbreviated form. Needed to differentiate motorcycle tyres and rims from those designed for other vehicles.
    16. 73 = load index code identifying the max permitted load. Please refer to conversion table for values in kg / lbs
    17. W = speed index code identifying the max permitted speed. Please refer to conversion table for values in km/h – mph
    18. TL = Tubeless. This tyre doesn't need a tube. Please consult the "safety" section regarding the use of tubes in tubeless tyres
    19. Made in Germany = indicates where the tyre has been produced
    20. Arrow = The arrow indicates the rotation direction of the tyre accordingly to its fitting position (front or rear). In case a rear tyre is fitted on a front wheel, the tyre has to be fitted reverse to the rotating direction indicated on the sidewall. Fitment of front tyres on rear wheel is not permitted.
  5. Just a few quick notes as I know a lot of people get confused with what
    the tyre companies descriptions do not explain...
    For a common 180-55-17 tyre

    As people have said 180 is "nominal" width. This means the manufacturer says "this tyre is suitable for bikes which require a 180mm wide tyre". The actual width of the tyre can often be from 175mm-190mm.
    Different widths can affect turn-in handling, and maybe not fit between
    the arms of your swingarm or forks.

    55 is the height as "aspect ratio" or "profile height". So a
    180-55 tyre is (55% of 180mm)=99mm high off the rim.
    Taller aspect ratio usually leads to a quicker turnin, lower
    means a smoother more stable turn-in.
    A different aspect ratio tyre WILL fit on the rim, will usually fit
    into the swingarm (if it does not get too much taller) but WILL affect
    handling/steering. Your 65 tyres might rub on the inside of the mudguard
    or hugger or swingarm.

    17 is the rim size in inches. The wrong rim size tyre will NOT fit on
    the wheel at all.

    I recommend sticking to stock sizes and aspect ratio etc almost all
    the time unless you seriously know what you are doing and have
    tried different tyres at different pressures already.

    A lot of handling changes can be made by changing brand/model
    of tyre instead. Going from a road to a supersport/track tyre
    - eg Michelin Pilot Road to a Pilot Power or
    - eg a Dunlop Roadsmart to a D-GP
    the tyre is a different shape (pointier when looking from front/rear)
    meaning much quicker/sportier turn-in, lighter steering, better
    edge grip when at full lean. The road/touring is more rounded
    meaning more stable handling, consistent grip and performance
    at all lean angles.
  6. You sure? I've got some biiig tyre levers :grin: .
  7. Grunge,

    the general rule is don't put a different tyre size on unless it is common knowledge that it improves the handling of the bike.
  8. Kewl... well now that I know the basics (what tyres I can actually put etc etc)
    I can think/research about what the differences in aspect ratio/profile height will do for my riding etc etc...

    Thanx for that quick lesson in the basics guys...
    I wonder if there are any more people wanting more info about tyres. :p