I have been told by my local Range Rover Dealer that if I have to fit my spare wheel (20" Original 7-spoke wheel) on my 2006 RR when I am running 22" Wheels I will total ruin my diff and cause £100s pounds of damage. I do appreciate that there is a small difference in diameter, around 30mm or so but is this true?

Should I be buying a set of original 20" wheels again? Might do as the road noise and harder ride from 22" wheels is grinding but would like to know if anyone has experienced a problem. Steve B

RR TDV8 56 VSE

The issue is that the front wheel diameter has to be within 1% of the rear wheel diameter so that the shaft speeds at the centre diff is closely matched. The centre diff has fancy torque biassing gearing that distributes torque based on differences in the shaft speed s of the prop shafts. Different sized tyres would force the props to run at different speeds making the diff fight very hard to bias torque, possibly leading to premature wear.

That being said, at low speed, the different wheel size would probably be alright in an emergency get you home, or get you to a nearby Tyre place. I certainly wouldn't drive at speed for long distances on it. Remember tweet on sharp turns, the props will be turning at different speeds, so the diff can deal with it, just not for sustained periods. V8 or else ...

Thank you for the info. I will probably end up refitting 20" Original wheels and tyres to combat any problems and give a better ride. Steve B

RR TDV8 56 VSE

Um, isn't the wheel/tyre diameter the same regardless of rim size, with the right profiles of course. Worth checking? Lots about this on the forum. .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

30 mm is actually a huge difference, so I would really avoid running this spare.

as said above, you can use it as a spare but only at low speed and to get you to a tyre shop or home....think of it as a spacesaver spare.. ... - .- -.




Y. O. L. O.
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You could buy a larger 20" tyre to compensate for the wheel diameter

It's not the dia of the wheel that matters it the circumference of the tyre that counts.
That's what determines the rotational speed of the wheel.
Haven't done a calculation but I'd bet theres not much in it.
Simple way to check is to put a tape around each of the tyre circumfrences.

There's a calculator in here that let's you compare very easily

http://www.1010tires.com/TireSizeCalculator.asp

Geez a break, diameter and circumference of a circle are proportionally linked, you can't say it's not the diameter but the circumference that affects rotational speed, the both do by the same ratio.

Ok, I've used wheel and not tyre in my post, but I think the point was clear. V8 or else ...

C= 2πr = 2π x d/2

So if the diameter is the same the circumference will be the same. Measure the diameter of the tyre on each of the wheels in question. .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

there's no need for this thread to get so complicated, steve only wanted to know if its safe to use his spare if he had to and the answer is yes with limitations..... ... - .- -.




Y. O. L. O.
.

at Professor Joe  Present :2008 TDV8 HSE
Gone Audi A5 2.7TDI
Gone Discovery 3 HSE
Gone Mercedes CLK
Gone Range Rover 2.5 DSE

Thank you to all who replied. I will look into a 20" tyre with same external diameter if possible. Someone told me a 22" will not fit in the spare wheel storage though. Will measure and report back. Steve B

RR TDV8 56 VSE

@ googsy

I had the Pythagoras Specs on  .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999