![]() | Home > Wheels & Tyres > Tyres and Low Profile |
![]() ![]() |
|
|
CS Member Since: 14 Apr 2015 Location: Edinburgh Posts: 1364 ![]() ![]() ![]() |
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 |
||
![]() |
|
pcourtney Member Since: 14 Jan 2020 Location: Stansted Posts: 763 ![]() ![]() ![]() |
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. |
||
![]() |
|
kevinp Member Since: 28 Sep 2019 Location: Telford Posts: 1182 ![]() ![]() ![]() |
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. |
||
![]() |
|
Vogue Member Since: 31 Jan 2008 Location: on the hill Posts: 3719 ![]() ![]() |
I cannot believe I am even reading this - different diameter tyre sizes on a permanent drive 4x4.
|
||
![]() |
|
JayGee Member Since: 27 Jul 2021 Location: London Posts: 3028 ![]() ![]() ![]() |
|
||
![]() |
|
rvbush Member Since: 08 Jan 2016 Location: Leamington Spa Posts: 529 ![]() ![]() ![]() |
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:
|
||
![]() |
|
JayGee Member Since: 27 Jul 2021 Location: London Posts: 3028 ![]() ![]() ![]() |
The diff is not designed to run continuously. 2012 TDV8 Vogue (L322) |
||
![]() |
|
Baltic Blue Member Since: 13 Aug 2015 Location: North Wales Posts: 3736 ![]() ![]() ![]() |
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.
|
||
![]() |
|
fisha Member Since: 25 Sep 2009 Location: Scotland Posts: 1280 ![]() ![]() |
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 ... |
||
![]() |
|
Gremlin500 Member Since: 11 Mar 2022 Location: Newcastle, UK Posts: 1296 ![]() ![]() ![]() |
@OP:
|
||
![]() |
|
JayGee Member Since: 27 Jul 2021 Location: London Posts: 3028 ![]() ![]() ![]() |
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) |
||
![]() |
|
pcourtney Member Since: 14 Jan 2020 Location: Stansted Posts: 763 ![]() ![]() ![]() |
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 ? |
||
![]() |
|
JayGee Member Since: 27 Jul 2021 Location: London Posts: 3028 ![]() ![]() ![]() |
I assume Baltic Blue means 55 profile over 50 and not the width (255 vs 250). 2012 TDV8 Vogue (L322) |
||
![]() |
|
AndyRoo Member Since: 06 Dec 2023 Location: Gloucester Posts: 512 ![]() ![]() ![]() |
Hi,
|
||
![]() |
|
![]() ![]() |
|
All times are GMT + 1 Hour |
< Previous Topic | Next Topic > |
Posting Rules
|
Site Copyright © 2006-2024 Futuranet Ltd & Martin Lewis
![](../images/layout/footer/disclaimer.gif)