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16" to 18" - How much will my speedo be out?

grimavxs

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Hi all,

have just bought a set of VY SS 18" rims and tyres.

Original tyres on car are (original VX S pac rims) 225/55/16

Proposed rims and tyre are (VY SS rims) 235/40/18

I found a cool excel spreadsheet which compare all aspects of the tyre and rims geometry (plz find attached)

However I dont know the offset of the rims... so cant accurately calculate.

Can someone help out?

Thanks
 

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minux

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It all depends on how much the rolling diameter changes, in alot of instances your speedo may not be affected.
 

grimavxs

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Sweeeeet
looks like any difference would be minimal..

I was worrying about speed cameras etc..

so now.. if my speedo reads 60 ill be doing 61 or so
 

FXST01

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Actually your speedo will read 60 but you'll be doing 59.2 kmh
 

Slick6

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I have an 'S' and did the calcs a while ago for all the options on my placard 15, 16 and 17.. Not one is the same..

Although when you think about it your rolling diameter would change between tyre types and new vs old tyres so it wouldn't make much of a difference int he long run
 
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