Tyre size?

Discussion in 'Mech Tech' started by rickyrooo1, Mar 19, 2012.

  1. i went for 225/70/15's on the back to up the gearing a bit

    worth thinking about if you have upped the engine power
     
  2. rickyrooo1

    rickyrooo1 Hanging round like a bad smell

    i don't get how the width up's the gearing? 225 is just the tyre width isn't it? the height of a standard wheel is 80 so dropping to 70 but adding an inch to the rim is the same is it not? 185 up to 205 or 225 should make no odds?
     
  3. Say tyre is 225/70/14 compared with 185/85/14, bear in mind T2's run 185/85/14 or 195/85/14 as standard
    225 is the width of tyre tread, 70 is the profile, this means the tyre wall height is 70% of tyre tread width and obviously 14 is rim diameter.
    therefore 70% of 225 is almost the same as 80% of 185 so the rolling radius will be almost identical, giving a radius of 210.5cm but if you up the rim size to 15 and still us a 225/70 tyre the radius increases by 8cm and increases your gearing by just under 4% which is about 1.2mph.
    try checking out tyre size comparison web sites
    ie:- http://www.kouki.co.uk/utilities/visual-tyre-size-calculator
    here you can play with changing tyre sizes to your hearts content.
    sorry its a bit long winded but there you go.
     
  4. rickyrooo1

    rickyrooo1 Hanging round like a bad smell

    so is 195 70 15 as near as i can get to my standard size?my tyres say 185 14 c (american) no mention of height
     
  5. 195/75/15 is about the same as 195/85/14, its 0.2mph higher
    or
    195/70/15 is about the same as 195/80/14, its 0.1mph higher
    most tyres are 80 or 85 profile if not marked but measure side wall height compared to tyre width this would confirm profile.
    so as close as it gets i think, but always pays to check as cant guarantee.
     
  6. The mad world of tyre sizes eh?
    Rim in inches,
    width in mm and
    height in %.

    It's enough to give you a headache. :)
     
  7. Does anyone know what the biggest size tyre I could get away with on 15" 5.5's?
    my van has been modestly lowered 1 spline on the rear and 1 adjuster on the front. I currently have 185,60,15
    Sorry to thread jack, rick
     
  8. You'll certainly be ok with standard diameter tyres Chris. Do you want bigger?
     
  9. Yes mate, I use my bus every day and part of my commute is motorway. So I was wondering if I could go bigger than I have to make the journey easier ;)
    But I'm mindful of clearance etc
     
  10. a 205 width tyre is the largest you can fit on a 5.5 inch rim
     
  11. rickyrooo1

    rickyrooo1 Hanging round like a bad smell

    so will 205 / 70 / 15 be the best for me not being lowered at all? or 75? or shall i get 195?
     
  12. Woodylubber

    Woodylubber Obsessive compulsive name changer

     
  13. rickyrooo1

    rickyrooo1 Hanging round like a bad smell

    195 it is then.
     
  14. i squeezed 225's on the back

    [​IMG]
     
  15. rickyrooo1

    rickyrooo1 Hanging round like a bad smell

    still need to work out if my standard tyre is 80 or 85 high, it just says 185/14 no height. i have my wheels now but i don't know whether to get 195/75/15 tyres = to 185/85/14 or 195/70/15 = to 185/80/14 if i have to guess then i suppose the 70 is best bet as i've never had 85 tyres before i always thought 80 was standard.
     
  16. Its a shame that there are no better offsets available. I would love 205 tyres on the back, but with my offset of 20, I think a 195 would be the max.

    With an offset of say 30 or 40, could even get a 6" or 7" wheel on there. Even on a 5.5" wheel, a better offset of say 30, would give you 10mm of extra clearance from the arch, meaning 205's would fit nicely.

    So, check your offset first, before buying your tyres.

    Don't know why the choice is so limited.
     
  17. rickyrooo1

    rickyrooo1 Hanging round like a bad smell

    i have no idea on the offset? will that be on the box or wheel?
     
  18. ET20 according to the SSP website
     
    Mark Ashton likes this.
  19. rickyrooo1

    rickyrooo1 Hanging round like a bad smell

    that means nowt to me lol i'll look on box later, my local tyre place i always use can get me 195/70/15 8 ply van tyres at £60 each fitted, no name make but at 1500 miles a year i think they will be ok?
     

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