[Drisser]

my fuel consumption since swapping back to my 19s has gone up from around 42-43 average to 44-45 in the last few days !

I guess I could work out what the extra inch gives you

[teaston]

They don't if you kerb them!

[sensible]

Originally Posted by Drisser

my fuel consumption since swapping back to my 19s has gone up from around 42-43 average to 44-45 in the last few days !

I guess I could work out what the extra inch gives you

Hasn't your fuel consumption gone down and your average mpg has gone up?

[AnthonyR]

Same brand and type of tyre?

[MattRST]

Less resistance on tyre brand or recent temperature increase?

[Kal101]

There was a remapping thread on here somewhere where a remapped car was showing less bhp at the wheels. This was put down to it running on winter tyres. Think it was something to do with bigger losses due to the softer rubber and the bigger sipes.

Just a thought.

Can't wait to put mine back along with new spacers.

[Drisser]

well, they are an inch bigger, so for every rotation of the wheel / shaft, that gives me Pi x radius squared for 19s v 18s if I remember school correctly !

[Drisser]

pretty sure the winters are less efficient also.. definitely more rolling resistance based on the feel.. by 19s are Good Years v Conti winter contacts

[Kal101]

Originally Posted by Drisser

well, they are an inch bigger, so for every rotation of the wheel / shaft, that gives me Pi x radius squared for 19s v 18s if I remember school correctly !

The overall wheel + tyre diameter will be the same - deeper side wall.

[Drisser]

that is what I was pondering - will the overall size be the same with the lower profile tyres ... couldn't remember what the 18s were now !

[AnthonyR]

Originally Posted by Kal001

The overall wheel + tyre diameter will be the same - deeper side wall.

Exactly what it is, if not ur electrics will start playing up as it would not be calibrated for the difference in size. I believe it is mainly to do with the difference in tyres

[Drisser]

in that case the goodyear eagles must run a lot better because I am a clear 2 mpg better on the 19s

[robbiep]

Originally Posted by Drisser

in that case the goodyear eagles must run a lot better because I am a clear 2 mpg better on the 19s

Were you on winter tyres previously though ? As others have said, winter tyres are softer, and thus give worse fuel economy

[HighlandPete]

Originally Posted by robbiep

Were you on winter tyres previously though ? As others have said, winter tyres are softer, and thus give worse fuel economy

It is not that simple, depends on the tyre. Rolling resistance could be different, but not necessarily. Both my winter and summer tyres have the same rolling/efficiency rating.

[maziatr]

Originally Posted by Drisser

my fuel consumption since swapping back to my 19s has gone up from around 42-43 average to 44-45 in the last few days !

I guess I could work out what the extra inch gives you

You mean it has gone down not up