hi, I sold some side steps a few days ago, guy turned up in a 06 ffrr to pick them up, as he drove away, his tyres looked bigger than mine, he had 20ins wheels as I do, I checked mine, and I have 275/40/20 tyres on stormer type alloys which I am now presuming are the wrong standard size and they should be 275/50/20, ?? this would prob explain why the speedo reads a good 7mph higher than my shown sat nav speed, cant really change them as they are almost new scorpions, they were on when I bought the car, can anyone confirm correct size
cheers hammie 2003 ffrr v8 vogue

20" on the full fat are 255 50 20

Load rating should be 109 also. Present :2008 TDV8 HSE
Gone Audi A5 2.7TDI
Gone Discovery 3 HSE
Gone Mercedes CLK
Gone Range Rover 2.5 DSE

These are factory standard: -

7.5J x 18 255/60 R18 112 H or V- All
8J x 18 235/65 R18 110 H - Winter
8J x 18 235/65 R18 110 H N Y
8J x 18 255/60 R18 112 H or V N Y
8J x 19 255/55 R19 111 H or V- All
8.5J x 20 255/50 R20 109 V- All

275's are not factory standard. Your 275/40's are only 95% of the circumference of the standard tyres. The 275/50's are 102% which is a lot closer.

Someone else will be along soon to tell you it doesn't matter or you should rush to the tyre depot for the correct tyres.

275/45/20 are the closest in diameter to the oem 255/50/20, but are 20mm wider.

So in theory ride should be better or worse? Present :2008 TDV8 HSE
Gone Audi A5 2.7TDI
Gone Discovery 3 HSE
Gone Mercedes CLK
Gone Range Rover 2.5 DSE

In theory better if they are 275/45/20 as the tyre wall depth is almost the same but they are 20mm wider. If they are 275/40/20 then worse as there is significantly less tyre wall depth.

A lot depends on which tyres you fit though as the General AT I have fitted is definitely worse than oem - but they are AT tread for the winter and off road use in the shooting season so its to be expected

cheers for your informed replies guys, as I said, the tyres on are as new, so they will have to stay put for the time being, just thought they look a bit small, plan to change the wheels next year, and will make sure I have the correct tyre size on
cheers hammie 2003 ffrr v8 vogue

Basically you have RR Sport tyres fitted... Probably came from a sport originally before being fitted to your car... So, your choices are not as limited as you maybe first thought? Sell them back to the RRS fraternity is another viable option

As Craig says - I would also flog them and buy some the right rolling radius - you would save money in the in unburnt fuel as your gearing is slightly lower with 40 profiles

Autodata lists 255/55R20 or 265/55R20 on 8,5x20 rims, I've just bought some Sport wheels with some knackered 275/40R20's on them, I've just spent £552 on 275/55R20 Hankooks.

Please tell me that 55 is the correct sidewall size for these as they had to be imported especially and are now fitted as of 10 mins ago!

Cheers Chris

275 55's are entirely wrong im afraid... 255.50.20 are the correct size for a FF

255's won't fit, it's got range rover sport wheels on it 9,5j or 10j I can't remember which!

Why does Autodata say ---/55R20's then?

And above it says ---/50R20!!!! Goddammit!!!!!!!!

Standard Diameter 763mm

275 55 20 Diameter 810mm

Difference 47mm or 6.16%

Recommended deviation only up to 2.5%.....