Just replaced my 20” wheels and fitted a set of 2016 genuine 21” alloys on my 2011 sport
Would I need to amend the settings in the ccf due to the increased diameter of the wheels so the the speedo etc reads correctly ?
Thanks in advance 

That depends on what tyre size is on. You can use a calculator like this - http://www.willtheyfit.com/ which will tell you the rolling circumference, and that is what dictates whether the speedo will be the same or not.

As a general rule, if you go bigger on the wheel, this can often be offset by going smaller on the tyre sidewall. 13MY Range Rover Sport Autobiography SDV6 - mine
14MY Range Rover Evoque Dynamic SD4 Black Pack - wife's
99MY Defender 90 TD5, Soft Top Conversion - my toy, and bairns favourite

What size was on the car & what size you fitted to car,,sometimes going slightly bigger makes the speedo more accurate.

Andy Andy.
21 Ford Ranger
Gone but not forgotten
Focus RS Red Edition
2015 RRS AB Fuji.
2014 RRS SC Santorini
2016 VW Amarok
2014 RRS AB Fuji
2012 RRS Red Edition Fuji
2015 Nissan Navara
2012 RRS SE Santorini
2008 RRS White
2007 RRS Santorino

Thanks for that insiorc
Would show that speedo would be out by -6.77%
I’m sure you can enable the ccf settings to allow for this with the iid bt tool
Pat at gap diagnostics will be the man to ask  

Last edited by aljo on Mon Sep 25 2017 7:37pm. Edited 1 time in total

Tyrefitter the original tyres are 275/40/r20

New wheels are 275 /45/ r 21 👍 

I have been running the 21" wheels for nearly three years and difference in speedo reading is negligible, at 30mph according to GPS it is less than 1 mph, If anything it is more accurate than it was from factory as Andy said. The wheel/Tyre size is in the CCF but it will not allow it to be changed for what ever reason. I believe Patrick at Gap was working on it to enable it to be changed, but not sure if he has done it yet.

Cheers
Col

Cheers Col
Will send pat an email about this