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Thread: Need an answer for understanding the numbers!

  1. #1

    Default Need an answer for understanding the numbers!

    For example..

    Profile: 235/40/18
    Wheels: 18x8.5 +45 Offset

    I have no idea what the numbers are for! I don't know what an offset is! And what matches what?! Someone explain to me please! Thanks in advance.

    ---------- Post added at 11:46 PM ---------- Previous post was at 11:43 PM ----------

    Oh, and the only things I know are the 18 is the 18 inch rims.. and 235 is the width thickness of the tyres.

  2. #2
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    The tyre numbers break down like this
    235 - 235mm width
    40 - 40% of 235 = 94mm, this is the tyres profile, or sidewall height
    18 - 18" wheel diameter

    Another thing that MUST be checked is that any replacement tyres satisfy the cars load rating, it is on the tyre placard, I cant remeber the MPS's spec off hand, but there will be a number like 89
    You also have the minimum speed rating on the placard, while you may have no intentions of exceeding 240 kph, you still need to satisfy the minimum rated requirements, although most decent tyres in these sizes usually carry a W rating (300+)

    Failure to follow these minimum requirements can, and has caused insurance companies to deny claims.

    Wheels
    18 - 18" diameter
    8.5 - 8.5" wide
    Offset +45, this is how far off centre the hub sits, so a +45 off set means the wheel hub is at 45mm closer (from the centerline) to the outer edge of the rim, a higher offset +52 sits the rim deeper in the guard, a lower offset +38 sits the rim further out, i.e hella flush.

    Here is a great calculator you can use to compare different wheel & tyre combinations, and see how they compare against your stock setup.

    Custom rims, wheel tire packages for your ride - RIMSnTIRES.com

    From memory the stock MPS wheels are 18 x 7 +52.5, stock tyres are 215/45/18
    Last edited by MattMPS3; 01-06-2011 at 06:17 AM.
    Nearly all men can stand adversity. But if you want to test a man's character - give him power.
    Abraham Lincoln

  3. Default

    Oh dude, prepare to get flamed for not using search functions prior to posting this little clanger.....
    I managed to google this out of laziness in less than a minute...

    Start here:

    Offset - 1010tires.com Tire & Wheel Tech
    Reading your tyre - Reading your tyre size

    Basically, the cut and thrust of the size you posted above is:

    235 - the width of the tyre in millimetres
    40 - The aspect ratio of the tyre, ie the sidewall height as a percentage of the tyre width
    18 - The diameter of the wheel
    18x8.5 - The wheel dimensions, 18 being the diameter and 8.5 being the width, in inches (we love to mix metric and imperial measurements)
    +45 - the offset of the wheel, ie the distance of the mounting surface of the rim to the wheel's true centreline

    As for what matches what? For example the Gen I 3MPS is 215/45 R18x7 +52.5. Jump on somewhere like 1010tires.com and do some searching with the tyre size and wheel offset calculators to get an idea about what will work. Or research it first on here...

    Search.....search.....search.....search.....

    Adrian

  4. #4
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    Default

    Quote Originally Posted by Damnfuzz View Post
    Oh dude, prepare to get flamed for not using search functions prior to posting this little clanger.....
    I managed to google this out of laziness in less than a minute...
    Haha, ironically, don't think he would get flamed on these forums, maybe a link to a post describing it, a link to a website describing it, or if I was first, it would be a lmgtfy link

    Also, Pretty sure stock gen 1 tyres are 89W
    Newbie FAQ My Build Thread
    From stock, to GT3071, to substantially less modded, many lessons learned!
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  5. #5
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    Default

    Yeah, flaming's not something I've seen a lot of here. Unlike the Mazdaspeed forums in the US

    As has been pointed out though, you'll get more people willing to assist if you show you've tried to find the answers yourself, as opposed to asking things that have been covered and documented a few times on the forums here

    Like the lord, OzMPS helps those who help themselves

    Nobody wants to crush your enthusiasm though. It's great that you're exited about your car as that's what they're all about . Just make the search engine here on the site your friend and you shall be richly rewarded with the informational juices that flow freely from this forum
    Caff Mobile Mk1 - 2010 Aluminum Gen II | 2XS SRI | H&R Lowered Springs | cpe 75 Duro Engine Mount | Whiteline Rear Swaybar | Moog "Problem Solver" Rear Endlinks | 3M Carbon Black Tint | Lakin Custom Plates | Opti-Coat Paint Protection | Paint Correction by Me - SOLD

    Caff Mobile Mk2 - 2008 BMW Z4M Coupe - Sapphire Black Metallic | Stock....for now

  6. #6
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    Quote Originally Posted by Caffeine Fiend View Post
    Like the lord, OzMPS helps those who help themselves
    Note to self, change forum moderator title to forum apostle, I even have the right name
    Nearly all men can stand adversity. But if you want to test a man's character - give him power.
    Abraham Lincoln

  7. #7
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    Quote Originally Posted by MattMPS3 View Post
    Note to self, change forum moderator title to forum apostle, I even have the right name
    Is that just a thinly veiled excuse to get away with wearing a toga Matt?

    Be honest now


    Sent from my iPhone using soon to be uninstalled POS Tapatalk App (fix the damn app you mofos!!!)
    Caff Mobile Mk1 - 2010 Aluminum Gen II | 2XS SRI | H&R Lowered Springs | cpe 75 Duro Engine Mount | Whiteline Rear Swaybar | Moog "Problem Solver" Rear Endlinks | 3M Carbon Black Tint | Lakin Custom Plates | Opti-Coat Paint Protection | Paint Correction by Me - SOLD

    Caff Mobile Mk2 - 2008 BMW Z4M Coupe - Sapphire Black Metallic | Stock....for now

  8. #8
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    Its a perfectly good excuse for wearing a thinly veiled toga.

  9. #9
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    *is thankful the forum isn't webcam enabled*




    Sent from my iPhone using soon to be uninstalled POS Tapatalk App (fix the damn app you mofos!!!)

  10. Default

    Sorry guys, perhaps I came across a bit harsh. It was very early in the morning and I hadn't had breakfast.... Note to self: eat breakfast, THEN read OzMPS...

    I suppose I just meant have a good hunt around on the forum for info such as this, and failing that, use a search engine such as google to find stuff. I knew the answers but went searching to help ME understand how easy it was to find. Turns out I found the info really really easily with a minimum of searching.

    And Matt, no more thin toga talk. People are already becoming concerned...

  11. #11
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    it's all good... personally im more concerned with matt wearing thinly veiled togas than people asking newbie questions

  12. #12

    Default

    Thanks for the replies!
    Would 235/40/18 with 18x8.5 +45 fit on my 6 MPS? or would it need rolling, and in that case, if my offset was like 50 would it mean there would more likely be less rubbing?

  13. #13

    Default

    "richly rewarded with the informational juices that flow freely from this forum"

    Seriously.... are you drinking with that coffee Random lol

  14. #14
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    Quote Originally Posted by kh92 View Post
    Thanks for the replies!
    Would 235/40/18 with 18x8.5 +45 fit on my 6 MPS? or would it need rolling, and in that case, if my offset was like 50 would it mean there would more likely be less rubbing?
    what size rims are you using?
    Newbie FAQ My Build Thread
    From stock, to GT3071, to substantially less modded, many lessons learned!
    3" HTP | 100 Cel DP | Autotech HPFP | AP V3 - Self Tuned on E20 | JBR RSB | CPE S2 REM | JBR Shifter Bushings

  15. #15

    Default

    I said 18x8.5 :P
    "Would 235/40/18 with 18x8.5 +45"

    Oh and is 40 sidewall height also abit to little?

  16. Default

    It might fit, but would definately need rolling of your rear guards. I have 18x8 +45 with 235 tyres and got rubbing at stock height say on the very outer 2 - 3mm from the inside edge of the guard.

    40 profile on the 235 is fine, and the 235/40/a8 size is very very close to stock rolling diameter so a good pick

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