With there being so many options of wheels/tyre combinations, presumably all with differing rolling diameters, how do you deal with recalibrating the speedo to read correctly?

Is there a setting in the CCF where you just select a wheel/tyre size or is the rolling diameter hard coded into the system?

 2017 4.4 SDV8 Autobiography
2012 4.4 TDV8 Westminster - Gone, but not forgotten

you cant Rob, theres no calibration i know of....

you could work out the speedo difference and try and remember it when you travel.. ... - .- -.




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Typically the speedo is showing higher speed than it actually is with 5-10 %. This has been true for most cars I've owned and I assume our RRs are similar. You can check your Speedo by comparing it to a GPS with a speed indication. The GPS is independent of rolling diameter and is showing a more correct reading.

With my Defender I changed from original 235/85R16 (31") to 285/75R16 (32") and the result was that the speedo on my Defender is now correct when compared to a GPS.

If you are worried, compare the speedo to a GPS and keep eventual difference in mind when driving. My guess is that an increase in tire size from for example 255/50r20 to 255/55r20 would result in a more accurate speedo than original. **********
Fullfatrr 5.0 S/C 2010
Defender TD5 2002

I thought these days with wheel speeds being "read" individually by the cars various systems that speedometers were more accurate compared to the old cable operated ones, which I agree were always out by around 10%. 2017 4.4 SDV8 Autobiography
2012 4.4 TDV8 Westminster - Gone, but not forgotten

Hi all, just found this post, I want to know about this too. There are sections on the CCF with tyre info, I have gone from 19 to 20 and up in profile too.

Anyone got any info, done any adjustments?

Click image to enlarge

this is a new feature on the iidtool and i've done this as well going from 20'' to 21''...whether this makes any difference i dont know... ... - .- -.




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Presume that's the latest firmware then Stan. Need to update mine....  2017 4.4 SDV8 Autobiography
2012 4.4 TDV8 Westminster - Gone, but not forgotten

i cant remember updating for a while Rob so not sure what version it is .. ... - .- -.




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Stan, can you let me know how you worked things out please? I have seen various calculators on the www, but would like to know how you calculated things just to get it right.

I've gone from 255x50x19 to 255x55x20 Current: TDV8 (3.6) RRS HSE



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not sure what you mean Stu...there's a part in the iidtool cff that lets you put in your wheel size and because i have recently changed from 20" to 21" i imputed 21"...
nit sure if this change makes a difference but it hasn't given me any warning lights on the dash.. ... - .- -.




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What I'm not sure of is how to work out the rolling radius and rolling circumference. My tyre size isn't on the list of options Current: TDV8 (3.6) RRS HSE



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Stu, your new 255/55-20 tyres are slightly bigger than the standard 20" so the speedo will read more or less spot on ..... ... - .- -.




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The 255 is mm and is width. The 55 is a percentage of the width, so the sidewall is 55% of 255 mm.....

You know the size of the alloy, but that's in inches...... so you need to do some conversion and some addition to get the overall diameter.... then you can work out circumference...... 2011 Range Rover Vogue SE 4.4 TDV8

Previous cars :
2003 Range Rover Vogue TD6
1999 Discovery Td5 ES
1995 BMW M5 3.8 6 speed
1992 Range Rover 3.9 Efi Vogue
1992 BMW M5 3.8
1988 BMW 735i SE
1989 Ford Sierra XR4x4 2.9i
1981 Ford Fiesta Supersport

there is a very easy and simple way how to adjust the speedo

if you buy an intravee unit for your L322 (BMW) you can set your speedo +/- think I have added 2mph to mine to read more than I'm traveling (to stop my photo being taken when I don't want it to be)

Thanks Guys, I'll have a fiddle over the weekend and check against my garmin to see how things are Current: TDV8 (3.6) RRS HSE



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TD6 Vogue
D2 V8 ES
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