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pcourtney



Member Since: 14 Jan 2020
Location: Stansted
Posts: 654

England 2011 Range Rover Vogue 4.4 V8 Sumatra Black
Tyres and Low Profile

I would like to have 255 50 R20 tyres on my car, so I have just bought 2 new Pirelli Scorpion Zero's for the fronts ( PNCS - just looks like a bit of damping stuck on the inside of the tyre)

But my rear tyres are 255 55 R20's ( 10% more profile) , they still have over 5mm of tread on them, and are just too good to throw away, so can 50 profile on the front and 55 on the rear work OK ??


Read a bit on google about why low profile might be a good option !
====================
There are several reasons why 4WD makers are taking the low profile tyre path: more precise steering; better on-road handling; more powerful braking; quicker water dispersal and more torque capacity.

Low profile tyres improve steering response because there is a reduced amount of flexible sidewall between the wheel and the tyre tread. If you fitted a video camera to the front mudguard of a 4WD and steered it around a series of hard turns you’d see how sidewall flex slows down the steering action that’s imparted to the wheel. In the case of a higher-profile tyre the wheel can be seen moving momentarily before the tyre follows it.

With a low profile tyre there’s no perceptible tyre sidewall flex and the wheel and tyre carcase move as one in response to steering inputs.

A low profile tyre can improve on-road handling, because the stiffer sidewall doesn’t roll towards the inside of the corner and so the tread area remains more stable, in contact with the road.

The torque load on the tyre is at its greatest at lift-off and under heavy braking, and the torque capacity of a tyre is generally increased if its sidewalls aren’t very tall. A stiffer sidewall is better able to resist the tendency for the wheel to rotate inside the tyre – look at slow-mo footage of a dragster taking off for an illustration of tyre sidewalls distorted by engine torque.

Post #682360 10th Jan 2024 8:13pm
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CS



Member Since: 14 Apr 2015
Location: Edinburgh
Posts: 1344

Scotland 2017 Range Rover Autobiography 5.0 SC V8 Corris Grey

255/50R20 is the original size for a 2011 car, and you will have crisper steering and handling with them. LR recommend changing all four tyres at once and warn that having different types around the car can result in instability. I'd certainly not consider running different sizes on the front and rear axles, the supposed "saving" is just not worth it in the context of your and your passengers' safety, construction & use regulations and possible harm to the car. Only Range Rovers since 1988

Post #682363 10th Jan 2024 8:56pm
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pcourtney



Member Since: 14 Jan 2020
Location: Stansted
Posts: 654

England 2011 Range Rover Vogue 4.4 V8 Sumatra Black

Yes I am fully aware that would be or very well maybe the LR stance on this, I was hoping for a more practical response, they are still 20" wheels all round, with 10 inches of tyre width ( 255mm) and if I had 200kg in the boot, and my tyre pressures were a little lower than normal, then in all possibilty I would be running 10% lower ride height on the rears, which I am sure LR would have considered way back in 2002 with the original L322 design and its continued appeal to farmers and other countryside linked businesses, but thank you all the same for your considered response.

Last edited by pcourtney on 11th Jan 2024 1:54pm. Edited 1 time in total

Post #682378 11th Jan 2024 12:35am
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kevinp



Member Since: 28 Sep 2019
Location: Telford
Posts: 1133

United Kingdom 2011 Range Rover Autobiography TDV8 Santorini Black

On a permanent 4x4 driveline I would say that the rolling radius of the tyres need to be identical to stop any transmission wind up hence the reason not to even use new and used tyres together because of the different tread depth.

Post #682380 11th Jan 2024 2:45am
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Vogue



Member Since: 31 Jan 2008
Location: on the hill
Posts: 3696

United Kingdom 

I cannot believe I am even reading this - different diameter tyre sizes on a permanent drive 4x4.

Never mind mechanical sympathy, if you lose control of you vehicle as a result have you no thought for the safety of yourself, passengers & other road users - and also invalidating your insurance - common sense would stop most people from doing it. 2021 L405 Vogue SE 4.4 V8 DIESEL ~ #17

Post #682383 11th Jan 2024 8:11am
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JayGee



Member Since: 27 Jul 2021
Location: London
Posts: 2766

United Kingdom 2012 Range Rover Vogue 4.4 V8 Orkney Grey

Shocked
255/50 R20 are not 'low profile' - you would need 21" or 22" wheels to acheive this in the modern 'SUV' style.
The L322 is never going to compte with a modern SUV in handing and most opt for taller tyres ( i.e the ones you have on the rear) to maximise where the L322 does beat modern SUV's - ride comfort. 2012 TDV8 Vogue (L322)

Post #682384 11th Jan 2024 8:53am
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rvbush



Member Since: 08 Jan 2016
Location: Leamington Spa
Posts: 522

United Kingdom 2011 Range Rover Vogue TDV8 Stornoway Grey

Can someone please explain the principle behind transmission wind up? All road vehicle transmission systems are fitted with differentials, these exist precisely to take account of differences (hence the name) between the actual revolutions of each wheel on an axle (eg, when cornering) and between axles in multi axle set ups, whilst maintaining drive to all driven wheels. So, what exactly is this transmission wind up? Drives:
2010 FFRR TdV8 Vogue - Stornoway Grey
2010 FFRR TdV8 Vogue SE - Zermatt Silver
1998 BMW E36 M3 GTII

Post #682387 11th Jan 2024 10:05am
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JayGee



Member Since: 27 Jul 2021
Location: London
Posts: 2766

United Kingdom 2012 Range Rover Vogue 4.4 V8 Orkney Grey

The diff is not designed to run continuously. 2012 TDV8 Vogue (L322)

Post #682389 11th Jan 2024 10:11am
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Baltic Blue



Member Since: 13 Aug 2015
Location: North Wales
Posts: 3689

United Kingdom 2011 Range Rover Vogue SE TDV8 Baltic Blue

Given the state of our roads, I.e. the number and depth of potholes we all see every day, it’s 255 all round for me and the improvement over 250’s is very noticeable.
Mike. G reg 2.5VM Vogue Portofino red 1991- 1999
V reg 2.5td P38 Rioja red 1999- 2006
53 reg td6 Vogue Oslo blue 2006- 2015
11 reg 4.4 TdV8 Vogue SE. Baltic blue 2015- date.
https://www.fullfatrr.com/forum/topic56162...tty+affair

Post #682392 11th Jan 2024 11:07am
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fisha



Member Since: 25 Sep 2009
Location: Scotland
Posts: 1256

2015 Range Rover Autobiography SDV8 Aruba

rvbush wrote:
Can someone please explain the principle behind transmission wind up? All road vehicle transmission systems are fitted with differentials, these exist precisely to take account of differences (hence the name) between the actual revolutions of each wheel on an axle (eg, when cornering) and between axles in multi axle set ups, whilst maintaining drive to all driven wheels. So, what exactly is this transmission wind up?


Yes ... and no in the case of 4x4's like the FFRR. Ordinarily, the centre diff is set to allow a *small* amount of rotational difference between the front and rear prop shafts. This is, as you say to account for basic driving scenarios when going along the road.

However, on detecting larger rotational differences in the propshafts, they'll quickly try to lock up and keep both shafts turning at the same speed. This is to overcome the scenarios where a wheel might be spinning due to lost traction, so by locking up, it transfers the power to other wheels which do have grip, and so you can keep moving when off road. Some will also lock up on sharp pull-aways from junctions and corners to keep from wheel spinning etc.

Some transfer boxes do this mechanically ( torsen diff ) where rotation difference puts mechanical pressure on itself to try and match the rotation. Some transfer boxes use a clutch pack which can be ECU controlled to lock up or unlock the propshafts together. ( sort of haldex style ).

Where you have different size tyres, then you'll be constantly be putting rotational difference into the transfer box, and it'll try and fight it ... leading to early failure.

Wind up is when the transfer box tries to lock up the propshafts and fight against the wheel rotation ... something has to give at some point, and it'll often be the tyres scrubbing. If you have a locked centre diff / transfer box off road, thats not normally a problem as the surface off road will be loose and so the ground will give way to the lock up. On tarmac, the tyre will grip hard and keep a lot more pressure on the transfer box.

The different size tyres as suggested in the 1st post are a recipe for disaster for the above reasons - it'll put constant pressure on the transfer box. Either your tyres will wear extremely quickly, or the centre diff / transfer box will. Or you're ECU's will throw a fit cause the rotational differences cant be figured out by the cars computers.

IIRC the old BMW / early L322s were recommended to have no more than 1% difference. V8 or else ...

Post #682393 11th Jan 2024 11:10am
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Gremlin500



Member Since: 11 Mar 2022
Location: Newcastle, UK
Posts: 1222

United Kingdom 2017 Range Rover Vogue TDV6 Corris Grey

@OP:

Some good and knowledgeable advice above, I think.

My view, (and probs a lot of others) is that any FFRR is not a “performance” vehicle in terms of handling at any stretch of the imagination, and any small gain in handling will be at the detriment of comfort, and therefore pointless, so most of us opt for comfort, but it’s purely a personal preference.

If I wanted an SUV with “handling” I’d junk the FFRR, and buy a Cayenne Whistle

Meanwhile, you can drastically improve the handling of your fullfat for free!

Slow down a bit Laughing “If it ain’t broke, don’t fix it” -where’s the fun in that?

Post #682402 11th Jan 2024 12:07pm
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JayGee



Member Since: 27 Jul 2021
Location: London
Posts: 2766

United Kingdom 2012 Range Rover Vogue 4.4 V8 Orkney Grey

Handling can also be drasticaly improved IME by replacing worn suspension components and a good 4 wheel alignment. Any marginal gains from stiffer sidewalls will be negated if the whole wheel geometry is being altered under load due to worn bushes. 2012 TDV8 Vogue (L322)

Post #682403 11th Jan 2024 12:20pm
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pcourtney



Member Since: 14 Jan 2020
Location: Stansted
Posts: 654

England 2011 Range Rover Vogue 4.4 V8 Sumatra Black

Baltic Blue wrote:
Given the state of our roads, I.e. the number and depth of potholes we all see every day, it’s 255 all round for me and the improvement over 250’s is very noticeable.
Mike.


I agree, my car also has 255 width on all 4 tyres ( 10 inches of tyre on the tarmac ) , I would not have less than this, it is the profile height that is in question ?

Post #682414 11th Jan 2024 2:01pm
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JayGee



Member Since: 27 Jul 2021
Location: London
Posts: 2766

United Kingdom 2012 Range Rover Vogue 4.4 V8 Orkney Grey

I assume Baltic Blue means 55 profile over 50 and not the width (255 vs 250). 2012 TDV8 Vogue (L322)

Post #682417 11th Jan 2024 2:08pm
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AndyRoo



Member Since: 06 Dec 2023
Location: Gloucester
Posts: 387

Scotland 2012 Range Rover Westminster TDV8 Fuji White

Hi,

Depends what you plan on doing with your car.

Anything less than a 55 profile you should consider as on road use. Although 50s and lower will work offroad there are some disadvantages that are great on the road / track but not really practical once you get off the blacktop.

Tyrewall felx is a definate advantage in rocky road conditions, lower tyre pressures combined with a high profile sidewall will allow the tyre to "grab" the rocks. Low profile and stiff sidewall cannot do that.

Similarly lowering tyre pressures in lower profile tyres will bring your rims that much closer to the ground so even small rocks are just going to chew your rims to bits.

For sand it's preferable to have a lower tyre pressure to allow the tyre to "balloon" and be able to grab the surface.

Running lower profile tyres running low pressures are at much higher risk of being pulled off the bead in rough going if you put any stress on the tyres.

Horses for courses, but I'd say of your using your RR on loose surfaces stick with 55 or higher, if your Chelsea High Street then go with whatever your like, but your never going to overcome the physics of heavy weights in motion.

Andy Fuji White 2012 4.4 TDV8 Westmiinster

Post #682418 11th Jan 2024 2:19pm
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