petrol prices

18" wheels make no difference!

When me and Pete went to the 'Ring last year in our 530's, we were in convoy for the entire trip and if anything, my fuel economy was slightly better. I don't see how you can get a more accurate comparison than that :p
 
OllyM said:
18" wheels make no difference!

When me and Pete went to the 'Ring last year in our 530's, we were in convoy for the entire trip and if anything, my fuel economy was slightly better. I don't see how you can get a more accurate comparison than that :p
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I made the same trip at the same speed a week apart, first time with 17's 2nd time with 18's and got 2mpg less. As the car was the same and the only difference was the wheels this is therefore more accurate than two different cars with two different sets of wheels :p

I also noticed I got about 5% more economy on the way to get my wheels fitted (20 miles away) than on the way back :p
 
OllyM said:
Different outside temperature? Different driving style on different days?!
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Less likely to be a variable than two different cars aged a year apart :) Ever since the exact day I fitted the 18's, my long distance cruise mpg has been a couple of mpg down :)
 
Thats because the unsprung weight has increased. Assuming the larger wheels are heavier it affects acceleration too which is why lightweight alloys are preferrable.
 
On the subject of fuel economy my last tank full was my most economical since records began (beginning of Feb) :eek: a whopping 32.5 MPG :o The lie-o-meter... sorry, trip computer was showing a much more flattering 35.4 MPG :p
 
Stonedofmoo said:
Thats because the unsprung weight has increased. Assuming the larger wheels are heavier it affects acceleration too which is why lightweight alloys are preferrable.
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There isn't much of a difference in weight but the rear wheels are now wider which I assume increases rolling resistence.
 
[TW]Fox;11652243 said:
Can't really say its making any difference to my car habits at all. When I decided to buy a somewhat thirsty car I did projected running costs based on fuel up to and including £3 a litre. It will take £4-5 a litre before it changes my usage habits.
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I doubt you took into account the knock-on effect those kind of rises in fuel price would have on your other expenditures e.g. shopping, given that businesses that rely on road haulage for distribution will pass on any added costs to the consumer.

So unless you're made of money I wouldn't act quite so nonchalant.
 
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norm said:
I doubt you took into account the knock-on effect those kind of rises in fuel price would have on your other expenditures e.g. shopping, given that businesses that rely on road haulage for distribution will pass on any added costs to the consumer
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None of this has any bearing on the cost of running my car but thanks for the patronising lecture on a subject I'm pretty sure I'm rather well versed in.
 
lordrobs said:
On the subject of fuel economy my last tank full was my most economical since records began (beginning of Feb) :eek: a whopping 32.5 MPG :o The lie-o-meter... sorry, trip computer was showing a much more flattering 35.4 MPG :p
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If you have access to vagcom you can calibrate the trip computer to be pretty accurate, I've got mine within 0.5mpg don't think its possible to get it much closer unless you have a more accurate method of briming the tank right to the top.

Weather is getting warmer now so petrol cars are in the warm up cycle for less time mines has went up about 1mpg in the last couple of weeks.
 
norm said:
given that businesses that rely on road haulage for distribution will pass on any added costs to the consumer.
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No, the big boys (DHL,Stobart Group etc) absorb it to a great extent whilst many smaller private hauliers cannot afford to pass on the extra for fear of being undercut by the big boys and subsequently go to the wall due to squeezed profit margin & massive cash flow issues.

Come to think about it, many are not small hauliers at all. :(

Our road haulage industry is dead on its wheels. :(

Anyway, back to the thread, don't mind me..... ;):D
 
[TW]Fox;11675221 said:
There isn't much of a difference in weight but the rear wheels are now wider which I assume increases rolling resistence.
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I think a few factors
1. The Rolling radii are probably different, even if they measure the same on paper, the 18's will be less flexy giving a slightly larger rolling radius?
2. Wider tyres = more drag
3. You've mentioned rolling resistance, it depends on a few things, less flexy tyres generally have less resistance due to less deformation, but more contact area may negate that, I don't exactly know..

Just some more 'possible' factors
 
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