Mine came with 255/55 R20’s so +25mm dia so the speedo and other trip data is off by a good 3%. In the hidden menu I can see the gps vs vehicle display difference and also on my phone’s gps. On the GAP website they say adjust the last 2 settings on the menu for rolling radius - abs and / or tyre size ( inches). Anyone done this? According to my calculations I’ll need to add 12mm to the rolling radius and set the tyre size (MSP-IPC) to 31(inches) 2012 TDV8 Vogue (L322)

What size tyres are you now running ?

255/55 R20 (verde) 2012 TDV8 Vogue (L322)

I am going to try a few changes today and monitor the results, I have changed to 285 40 22 Scorpion All Seasons. I have noticed a setting change for actual tyre size also but the Gap iid only allows 19 & 20 inch, I should imagine as they were only option when new, there are other non highlighted sizes available.

I very much doubt you will need to correct anything - every single LR/RR I have owned the speedo over reads by around 5% anyway - the larger tyres will just make the readings more accurate. There are several iPhone Apps you can download to check the readings - I have also triple checked mine in the past with a Snooper and Road Angel. I suspect your readings will still be a touch over by 1 or 2 mph 2021 L405 Vogue SE 4.4 V8 DIESEL ~ #17

Sonearly wrote:

I am going to try a few changes today and monitor the results, I have changed to 285 40 22 Scorpion All Seasons. I have noticed a setting change for actual tyre size also but the Gap iid only allows 19 & 20 inch, I should imagine as they were only option when new, there are other non highlighted sizes available.

Vogue wrote:

I very much doubt you will need to correct anything - every single LR/RR I have owned the speedo over reads by around 5% anyway - the larger tyres will just make the readings more accurate. There are several iPhone Apps you can download to check the readings - I have also triple checked mine in the past with a Snooper and Road Angel. I suspect your readings will still be a touch over by 1 or 2 mph

Mine is actually under reading presently, which concerns me especially with the amount of variable speed limits on UK motorways. Just had to complete Motorway Awareness Course, pretty sure I was on cruise control, might have been set at 64, I know a touch over but clocked at 69. Would just like to have Speedo as closely calibrated as possible, not sure if it also effects gearbox settings also. On the secret menu at 100 kph, Most showing 100, GPS 107- 108

285/40/22 is the same size up from stock as 255/55/20 so my calculated settings under the IPC-instrument pack are either
2nd from bottom (rolling radius-ABS mm) 382
or
bottom (msp-IPC) - 31
Probably best to set each on their own and see.
Also you can enable the a digital numerical speed in the main display under the same menu which may help. 2012 TDV8 Vogue (L322)

On my D4 I went from 255 50 20s to 285 50 20s and when I checked the speedo against the gps if found on the 285s it was within 1mph of accurate at 70-80mph so it must have been over reading with the standard tyres on  Paul

2014 Range Rover vogue se 4.4sdv8 Loire Blue
1992 Range Rover Vogue LSE 4.2 Ardennes green

Just noticed my wheel size is already set to 31" in the 'MSP-IPC' so likley the key setting is the rolling radius. Will set this tomorrow after a drive has charged up the battery a bit more. 2012 TDV8 Vogue (L322)

Fair run on the motorway, set at 31 and 22 wheel and 285 width.

Set cruise at 100kph, Speed display showed 100, on Secret Menu GPS at 100, Most 95.2

Would have thought Most and Speedo to be the same. Perhaps wrong way round.

JayGee wrote:

Vogue wrote:

I very much doubt you will need to correct anything - every single LR/RR I have owned the speedo over reads by around 5% anyway - the larger tyres will just make the readings more accurate. There are several iPhone Apps you can download to check the readings - I have also triple checked mine in the past with a Snooper and Road Angel. I suspect your readings will still be a touch over by 1 or 2 mph

All cars over read vs actual speed by design and LR are no different in this respect. Probably a 1/2" rolling radius increase is OK but for larger increases you also have to consider the other systems such as ABS, traction control and gearbox as these will all be expecting a predictable behaviour from the assumed rolling radius. For instance the gearbox may hold on to gears longer as it will assume the car is requiring more power to achieve a certain speed. Also the ABS may also struggle to function optimally even if it still works OK.

Probably there is enough tolerance built into the system to cope. I’d just be happier with an over reading speedo that gives you some room for error as both my SP30’s were right on the limit for 10%+2mph. I also miss the big numerical speed display on my old Audi. 2012 TDV8 Vogue (L322)

I’m doing a long run midweek and will have a play with settings and the same time will download a couple of GPS speed apps. I agree with JayGee, I just want the comfort of knowing approx speed without having to revert to over cautious driving. More importantly, if there is a way for greater accuracy and piece of mind by adjusting system settings, I want to find it.

Still don’t get why Speedo same as GPS reading and Most being the different one. Perhaps the settings are more accurate now