504 Tyre Size
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Thread: 504 Tyre Size

  1. #1
    Fellow Frogger! Tom_95's Avatar
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    Default 504 Tyre Size

    Hi, so here's my question...

    The speedo has always read a bit faster than the car is actually going (reads 100kph, actually traveling at 90 etc) and I was wondering if it was something to do with the tyres possibly being incorrectly sized...

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    So my question is what size should they be? (with standard wheels)

    Thanks
    Thomas

  2. #2
    Fellow Frogger!
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    Default

    found this which should help you out!

    http://www.automobile-catalog.com/ti...ugeot_504.html
    Lets just say we have a few pugs about!

  3. #3
    Fellow Frogger! sfrawley's Avatar
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    Mine came new with 175-14 (forget the profile) but I have been on 185/75-14 for a long time. The speedo reads about 5% high compared to a GPS reading.
    Stephen
    '03 P406 HDI
    '16 Renault Master

  4. #4
    Fellow Frogger! FedGrapes's Avatar
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    Default

    175/80 R14 on the 5.5 inch wide standard steel rims.

    Pretty hard to find a set of rubbers that size, so I've recently got 185/75 R14 on each corner.

    My speed reads fairly accurately, though now reads slightly higher (about 2%) with the 185/75 instead of 175/80 on the front.


    Perhaps a previous owner changed the diff? 10% error I would guess is pretty large!

  5. #5
    Fellow Frogger! Doush_504's Avatar
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    Quote Originally Posted by Hipcrostino View Post
    found this which should help you out!

    http://www.automobile-catalog.com/ti...ugeot_504.html
    IMHO the info on this website is not 100% accurate. For instance the 195/65/15 commonly used with the 505 GTi rims on the 504 is only 1 mm smaller in diameter than the original 175/80/14 which equates to -.17% error, while the above website says its -1.4%.
    My refrence is: http://www.tiresizecalculator.info/

    Edit: a little search about the 175-SR-14 mentioned in the user's manual revealed that the aspect ratio is actually 82 and not 80 like I used to think, which explains the larger error percentages listed by Hipcrostino's website. It seems that this replacement issue was discussed in Mercedes forums as the W123 had the exact same size as standard.More info here
    http://www.barrystiretech.com/tiresizing.html
    Last edited by Doush_504; 1st June 2012 at 05:58 PM.
    Chadi

    1982 504 SR white manual sedan with A/C (257 000 Km)
    2012 308 1.6 VTi Vapor Grey manual H/B (35000 Km)
    1994 405 1.6 white manual sedan (208 000 Km)
    1992 605 SV24 (91 000 Km)
    2005 406 2.0L automatic (Replaced with a 2013 C5)
    1983 505 GR white manual sedan with A/C (170000 Km)

    All since new


  6. #6
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    I don't profess to know how, or why, but on occasion at work I have compared tyres from different manufacturers with the same nominal size, and outside diameter has been up to 40mm different. Figure that one!

  7. #7
    Fellow Frogger! FedGrapes's Avatar
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    Quote Originally Posted by kiwia110 View Post
    I don't profess to know how, or why, but on occasion at work I have compared tyres from different manufacturers with the same nominal size, and outside diameter has been up to 40mm different. Figure that one!

    *shrug* Fitted to the rim? They possibly react differently to pressure!

  8. #8
    Fellow Frogger!
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    No, not fitted!

  9. #9
    Fellow Frogger! Bruce Llewellyn's Avatar
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    Default The Tyre pavement interface.

    Hi,

    Tyres have several different sizes, all at once.

    There is the geometric diameter, easy to measure and absolutly meaningless unless it's rubbing on the bodywork.

    There is the 'static loaded radius' which is measures from the ground to the centre of the wheel. This varies with pressure, as would be obvious for those of us who have had flat tyres, which arte only flat on the bottom...

    There is the dynamic rolling radius, which is measured by guys in white coats using rolling road belt machines.

    This is before the peugeot turns into a corner and all the other anorak terms come into play... See Milliken & Milliken on racing car design.

    Bruce.

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