# Cars Tyre sizes into Assetto Corsa

Discussion in 'Assetto Corsa Modding Discussions' started by ltcars, Jun 1, 2017.

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1. ### ltcars

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If I search tyre sizes at Google, I usually get a result like this:
245/45R12 98

WIDTH=0.245 I know what to do for this but the rest...

2. ### garyjpaterson

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Just a bit of maths, should be easy enough.

45 - profile height (as a percentage of the above tread width)
R12 - rim diameter (inches)

You know the rim radius, thats 12 inches divided by 2, then converted to meters (google will do that for you). Though make that 13/2, because AC suggests adding 1 inch...

Or you can set up a wee formula in excel to do it for you

WIDTH=0.245

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Thanks a lot

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4. ### Stereo

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You shouldn't include the extra inch in the overall radius though, since it represents the lip of the rim that extends out past the bead. I know your numbers don't, just worth being clear. The rim radius is used for popped tires to say where the car'll ride on its rims.

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5. ### Willy Wale

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Not sure if it matters in AC but the geometric radius of the wheel/tyre is different to the dynamic (wheel centre to ground) radius because the weight of the car squashes the tyre.

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6. ### Stereo

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Use the geometric radius in RADIUS=, then adjust the spring rate and spring rate change w/ pressure until the dynamic radius is ok.

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7. ### garyjpaterson

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Yep I should've clarified that, i never even thought about it.

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Could someone help me out with this because Content Manager gives me a size that I don't agree with.

I have a wheel size of 265/35/18

((18+1) / 2) * 0,0254 = 0,2413

(18 / 2) * 0,0254 = 0,2286
(265*0,35) / 1000 = 0,09275
0,2286 + 0,09275 = 0,32185

Yet when looking inside Content Manager it gives me 265/25/18?

9. ### ltcars

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I think I had these too in the past, probably just a bug. I'm no expert though

10. ### aphidgod

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For tire sizes, I cheat and go to tirerack.com and check the actual manufacturer spec on the tires in question. It's usually very close to, but not quite equal to, the mathematical result posted above.

On the CM thing... I reported that as a bug a year ago. Was told it's working perfectly, even though it's not, so...