Bigger Wheels on 460

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Jdring
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Joined: 12.04.2004
Location: South of Oxford, UK. 'dingaling' on the Register
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I got a nice set of 265/60 R18 wheels (from a G350 I think) and want to try them first on my 460.

Will I need spacers and longer wheel bolts to prevent rubbing/contact on the inner sides?

Obviously no electronics or ESP to worry about, and the slightly bigger circumference may add a little bit of top-speed for a more comfortable 3k rpm running.

I thought I would calculate that and to start there is a good explanation of Tyre Size standard here:

https://www.uniroyal-tyres.com/car/tyre-guide/tyre-knowledge/what-does-tyre-size-mean 

So the circumference of my current 460 wheels (225/R75 R16) would be:

75% x 225 = 169mm.  Plus half the rim diameter = R16 / 2 * 25.4 = 203mm.   168+203 = 372mm Radius (744mm diameter)

Interestingly, measured diameter with a tape and it was about 720mm, so close !

For the new tyre (265/60 R18):

60% x 265 = 159mm.  Redius = R18 / 2 x 25.4 = 229mm.  159 + 229 = 388mm  (775mm diameter)

Measured at 750mm, so the same undermeasurement.

 

Lets go with the calculated diameters:

1 wheel revolution = Pi x Diameter = 3.1416 x 744 = 2.34m  (for the 460 wheel)

1 wheel revolution = 3.1416 x 775 = 2.43m  (for the 463 wheels) - not that different

2.43/2.34 = +3.8%  per revolution.

Now the guessing part... I recall that the 460 does about 3,800rpm at 60mph currently.  So with the 3.8% increase in wheel, that will increase to 62.28mph.

So after all that... bugger all noticeable increase!

 

Anyway - they will look nice - anyone got wheel spacers and bolts?