Real world mpg

I think it has been stated that the figures quoted are not taken from a LR measurement, but from a standard government test, in which case they are covered, they submitted the cars for test, the results came back, and they publish them, end of... if anything is at fault its the tests that need updating to better reflect the real world scenario. In terms of anyone getting anything out of or from LR on this, i think you have roughly zero chance of that !

You can pretty much guarantee the cars used in the tests are the most economic versions possible, hence the SD will be the pure model on 18inch rims etc, all you guys on 20's should expect the mpg to be hammered due to the 2inch size increase over the ones no doubt used in the tests. I changed the wheels on a golf TDI some years ago, from 17 to 19 and lost about 8mpg average !, not to mention the acceleration was worse etc etc, smaller wheels = better mpg and acceleration, but obviously don't look as good and might not handle as well.

a lot of sense there Pedals

(02-01-2012 07:00pm)Pedalpower Wrote:  all you guys on 20's should expect the mpg to be hammered due to the 2inch size increase over the ones no doubt used in the tests.

The rolling radius of 18, 19 or 20 are all about the same due to tyre depth! therefore this has minimal impact!

Tyre efficiency will have more of an effect, Cheap tyres, more drag, less mpg!

Biggest effect will be the fact we've put Panoramic roof, electric tail, Lux seats, spare wheel all add weight and therefore reduce mpg!

(02-01-2012 07:44pm)PhilSkill Wrote:  The rolling radius of 18, 19 or 20 are all about the same due to tyre depth! therefore this has minimal impact!

Tyre efficiency will have more of an effect, Cheap tyres, more drag, less mpg!

Biggest effect will be the fact we've put Panoramic roof, electric tail, Lux seats, spare wheel all add weight and therefore reduce mpg!

no you have missed the point, of course the rolling diameter is the same !, the aspect ratio of the tire makes up the difference, it is the centrifugal mass which is massively different (alloy is heavier than rubber/Air!), the weight of a 20inch rim is much more than a 18, and the hence power required to make it spin is much more than a 18. Rotating mass can be multiplied by 2 or 3 to crudely get a idea of added weight to the car, hence and extra 4 lb on a wheel is like carrying 8 or 12 or so in the car, multiple that for 4 wheels and you are looking at a big gain. Drag is a factor, but nothing like rotating mass. Having big wheels will have a much much bigger affect than the tail gate or roof, every time you accelerate you are having to spin up the extra mass. I have seen it first hand, why do you think the pure can be purchased on 18inch wheels ?, its not for looks thats for sure . Take a look at VW bluemothin cars, i think the golf comes with something crazy like 15inch wheels !. If you have 20inch wheels expect to have compromised mpg.

(02-01-2012 07:57pm)Pedalpower Wrote:  no you have missed the point, of course the rolling diameter is the same !, the aspect ratio of the tire makes up the difference, it is the centrifugal mass which is massively different (alloy is heavier than rubber/Air!), the weight of a 20inch rim is much more than a 18, and the hence power required to make it spin is much more than a 18. Rotating mass can be multiplied by 2 or 3 to crudely get a idea of added weight to the car, hence and extra 4 lb on a wheel is like carrying 8 or 12 or so in the car, multiple that for 4 wheels and you are looking at a big gain. Drag is a factor, but nothing like rotating mass. Having big wheels will have a much much bigger affect than the tail gate or roof, every time you accelerate you are having to spin up the extra mass. I have seen it first hand, why do you think the pure can be purchased on 18inch wheels ?, its not for looks thats for sure . Take a look at VW bluemothin cars, i think the golf comes with something crazy like 15inch wheels !. If you have 20inch wheels expect to have compromised mpg.

Tosh. er, apologies, I meant 'in my somewhat opinionated view'

I have 18" and 19" wheels for the Evoque. Can't say the 19's feel heavy.
I have 17", 18" and 19", all in both road and AT for the Discovery. There's a small difference in weight between some of them, but it makes no noticeable difference in mpg. Road v All terrain can make about a 2mpg difference though.

Width (and length - ie pressure it's running at) of tyre in contact with road is likely to a significant factor.

My Evoque is running on 18" rims, so using your logic is in optimum format yet still unable to get anywhere near the figures.

TD4 Pure 150bhp on 18" Michelins 6000km on clock and on a 680km round trip( mostly 100/120km/h )it averaged 8L/100Km or (35mpg ) NOT near what i was expecting ,my previous 2.7 tdv6 Discovery 3 on the very same run always averaged 34 mpg . these are measured brim full before and after trip which works out as near as you get to dash displayed figures . Land Rover best come up with a solution soon before word spreads that they failed in producing as fuel efficient vehicle as claimed !

It does state in the brochure that the fuel economy is based on driving styles, this that & everything else & they can't be held to account - I tried!

However if enough & I mean enough people complained at the same time & we can show proof then I guess they may listen.

(02-01-2012 08:34pm)Dave_T Wrote:  Tosh

I have 18" and 19" wheels for the Evoque. Can't say the 19's feel heavy.
I have 17", 18" and 19", all in both road and AT for the Discovery. There's a small difference in weight between some of them, but it makes no noticeable difference in mpg. Road v All terrain can make about a 2mpg difference though.

Width (and length - ie pressure it's running at) of tyre in contact with road is likely to a significant factor.

My Evoque is running on 18" rims, so using your logic is in optimum format yet still unable to get anywhere near the figures.

Its not Tosh, its science !, you picking up wheels and 'feeling; if they feel heavy or not does not constitute a disproval of scientific fact !, also i am taiking about 20inch wheels, the jump from 18 to 20 is significant enough and will make a difference to the mpg.

(03-01-2012 12:04am)Pedalpower Wrote:  Its not Tosh, its science !, you picking up wheels and 'feeling; if they feel heavy or not does not constitute a disproval of scientific fact !, also i am taiking about 20inch wheels, the jump from 18 to 20 is significant enough and will make a difference to the mpg.

Sorry, I was just editing that

I'm still not convinced though. I'll find out the relative weights for you

Be good to know the weights as I cant believe theres very much difference (yes agree there will be some and not in a positive way, plus they are slightly wider) yes its times 4 and the forces will be squared but overall not convinced there'll be much in it especially with the lighter weight magnesium/alu wheels against weight of extra rubber, I have some 19 style 5's but no accurate way to measure.

200kgs of extras is also quite a lot to accelerate, still think that'll have more effect.

Dont disagree with the principal though yes they will use the setup to get best result, although I doubt the car does much accel in that test, maybe these figures are calculations not real tests... anyone know?