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Bit confused here

Old wheels: 195/50 R16

New sheels: 205/40 R17

In forscan change Tire dimension from old to new but what about tire circumference?

Its currently set at 1835mm but that doesn't make sense to me when using circumference calculators, what should it be set to for 17" alloys? What do you guys have it set to?

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Doesn't it change automatically when you change tyre size?

You can work it with some maths...I make it 1874mm.  There will be some tolerance because tyres aren't as exact as you'd think, plus sidewall flex etc.

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I got 1872mm. To be fair though I'm useless at maths!😂

Wheel 17 inches - 431.8mm

Tyre profile 40% of 205mm x 2 = 164mm

 

Total 595.8 x pie (3.14159) = 1,871.759322mm

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depends how exact you want to be with PI. A lot of people use 3.14 and hardly anyone goes beyond 3.142 in terms of decimal places I reckon.

3.14159265358979323846264338327950288419716939937510...[

As Tom's Focus says There will be some tolerance because tyres aren't as exact as you'd think, plus sidewall flex etc .    Also the difference between new and barely legal tyre with be about 35mm difference in circumference.

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I just googled 'Maths Pie' lol, my school days are well behind me, the fact I put 'Pie' rather than 'PI' says it all really.😂

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Thanks for the informative replys guys but you have all missed the kicker on this one

Work out my original wheel size and you will get somewhere around 1887 but my car was set to 1835

This was the reasoning for my question and really want to know what people have theirs set to out the factory with 17" wheels...

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41 minutes ago, liamstears said:

Thanks for the informative replys guys but you have all missed the kicker on this one

Work out my original wheel size and you will get somewhere around 1887 but my car was set to 1835

This was the reasoning for my question and really want to know what people have theirs set to out the factory with 17" wheels...

You're right, well, I got 1889mm for your originals.

So (16") 1889mm - 1835mm (factory set) = 54mm

(17") 1872 - 54mm = 1818mm

Problem solved!🤔

Only joking mate, I'm sure someone will be able to check exactly what they have it set to with 17's from the factory soon.

That's more maths than I've done in the last 25yrs!😂

 

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Is the factory setting for a half worn tyre or down to the TWIs  ?

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