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richardsimkiss
Member Since: 22 Feb 2017
Location: Warwickshire
Posts: 5
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| 255/55R19 vs 255/50R19 (D3 vs RRS) - Please Enlighten me...! |
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I've searched, pondered, and searched some more but to no avail - I simply can't find an answer. And I'll come clean - I'm currently a RR Sport owner, but find myself on Disco3.co.uk more often than rrsport.co.uk 
To the best of my understanding - D3 and RRS 2.7 TDV6 have the same engine, gearbox, and chassis/running gear... all except for the wheels/tyres.
Disco 3 (L319) runs 255/55R19 from the factory
RR Sport (L320) runs 255/50R19 from the factory
If we exclude load rating (I know D3 has a higher load rating), I can't for the life of me fathom why they would specify different tyre profiles for the two vehicles, given a 3.4% difference in rolling circumference. Anybody have any idea as to why?
I'm not sure how the speedo is configured - I'm assuming it's not mechanical? Is it programmed into a control module somewhere (and the control module for D3 coded differently to RRS?) 
Appreciate this isn't the simplest/most obvious of questions - but curiosity has gotten the better of me and I had to ask!
Last edited by richardsimkiss on 5th Mar 2022 9:45 am. Edited 1 time in total
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 5th Mar 2022 9:23 am |
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NJSS
Member Since: 06 May 2009
Location: Catherington, Hampshire.
Posts: 10798
 
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Welcome richardsimkiss.
My guess, and it is a guess, is that JLR think the RRS looks better with the slightly lower sidewall tyres.
IMHO it would be more comfortable & better off-road with with 255/55 R19.
NJSS Am I Gammon or Woke ? - I neither know nor care.
2016 Discovery 4 Landmark
2011 Mercedes Benz SL350 (R230)
1973 MG B GT V8 - 3.9L John Eales engine, 5 speed R380 gearbox, since 1975.
1959 MGA roadster - 1.9L Peter Burgess Engine - 5 speed gearbox
Past LRs - Multiple FFRs, Discos & a Series I - some petrol, some diesel,
none Electric or H2 fuel cell - yet.
There are 10 types of people in this world: Those who understand binary, and those who don’t.
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| 5th Mar 2022 9:30 am |
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Hardware
Member Since: 28 Jun 2016
Location: Hiding under the M60
Posts: 13018
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indeed, welcome to the madhouse!
your thread title 225/55R19 vs 255/50R19 (D3 vs RRS) - Please Enlighten me...! confused me but i can see it was a typo and not a non-standard tyre size.  .
Dean
====================================
2011 D4 XS - OBD port protection, RLD spare wheel protector, All LED interiors lights, Timed Climate enabled, iiD tool paired.
2011 D4 Landmark - Stolen from same dealer before I paid for it
2011 D4 GS - Stolen whilst at dealer  ... All LED interiors lights, DRLs, Spare Wheel protector.
1996 300Tdi - Eaten by tin worms
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| 5th Mar 2022 9:35 am |
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richardsimkiss
Member Since: 22 Feb 2017
Location: Warwickshire
Posts: 5
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Oh jeez... thanks Hardware... hopefully I've now corrected it now - at least it enticed you to take a look at the thread 
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| 5th Mar 2022 9:47 am |
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richardsimkiss
Member Since: 22 Feb 2017
Location: Warwickshire
Posts: 5
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Okay.... I think I've sussed it out after spending the the last 2 hours pondering.
The reality is I'm already running D3 wheels and tyres on my RRS - (255/55R19), I've had a blowout (a dislodged kerbstone on a motorway bridge took a chunk out the sidewall) and started looking for replacements, of course this tyre size is flagged up as incorrect for RRS, and is notably different in size (3.4%) to the RRS spec'd 255/50R19.
Having looked at the tyre options for D3, they're all within 0.1% of each other
Having looked at a number of tyre options for RRS, they're within 0.3% of each other
So there's a ~3.5% difference between the two model lines - which I can only assume they account for in the programming of whatever control module looks after the speedo readout...
...I think 
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| 5th Mar 2022 9:52 am |
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ronp
Member Since: 29 Nov 2006
Location: North Yorkshire
Posts: 15263
 
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Just make sure you keep the same tyre size per axle.
Mixing different sizes on the same axle gives a different rolling radius that can be picked up by the car.
In doing so it can then be put into limp mode.
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| 5th Mar 2022 11:26 am |
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richardsimkiss
Member Since: 22 Feb 2017
Location: Warwickshire
Posts: 5
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sage advice... since I didn't want mixed brands I'd already committed to new tyres on all corners - after hours of research I'm now £500 lighter (not bad for the size of tyre, but far from what I'd like to pay!).
Also seems virtually every tyre in existence is a terrible decision if you read enough reviews. I won't divulge what I went for for fear of comments, but rest assured it was a premium brand (and kwik fit were cheapest with 15% off atm)
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| 5th Mar 2022 11:32 am |
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Gary_P
Member Since: 03 May 2016
Location: Kent
Posts: 1664
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Know what you mean about the reviews. I think it helps to focus on the main /most important to you type of motoring you do and go for a tyre rated well for that. Gary
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Discovery 4 HSE 2016MY
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| 5th Mar 2022 12:59 pm |
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riverblanche
Member Since: 31 Aug 2010
Location: retford'ish
Posts: 2226
  
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Hi,
the RRS is the sporty version so has lower side walls
although the G4 model had 255/55/19 
if your still going with the 55% aspect ratio just remember to tell your insurance company that you have fitted different wheels and they are Genuine l/r wheels so should not be a mod
the right tyres are the ones that suit your needs the best 
your speedo should be spot on now as well (mine was )
 Transit! 2019
Gone D3 HSE 2008
Another Porsche Cayenne 2022
Gone Porsche Cayenne 2020
Gone RRS HSE Dynamic 2016
Gone RRS HSE LUX 2011
Gone RRS HSE 2006
Gone D3 SE 2.7 2008
gone D2 Td5 1999
I plan on living forever and so far so good !
Club DG Mclaren stuff
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| 5th Mar 2022 7:42 pm |
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richardsimkiss
Member Since: 22 Feb 2017
Location: Warwickshire
Posts: 5
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Quote:your speedo should be spot on now as well (mine was )
Yup! Still going with the 55's... and I definitely noticed the improved speedo accuracy too
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| 7th Mar 2022 7:27 am |
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