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Home > Technical > Amazing decrease in fuel consumption! |
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gilford Member Since: 07 Jan 2010 Location: Anglesey Posts: 542 |
I think you mess up your MPG computer when you change wheel sizes? |
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Thu Nov 10 2011 4:11pm |
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Jmac Member Since: 17 Feb 2011 Location: South Posts: 125 |
I totally agree that new tyres will give different readings when compared to worn out ones due to a different rolling radius but 20% ??? surely not... My speedometer seems to be the same - i definitely dont think im going 20% faster or slower! Also, as the tyres are LR specification sizes for the car, I would have thought the car should be pretty accurate for both sizes.. cheers, J |
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Thu Nov 10 2011 4:30pm |
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JonnyDangerous Member Since: 09 Nov 2009 Location: Reading Posts: 57 |
hmmm - i always thoughts (maybe incorrectly) that the actual circumference of the wheel is the same if its a 19" or 20" rim as the inch difference on the 19" rim is made up by a tyre that is less low profile.
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Thu Nov 10 2011 5:21pm |
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Jmac Member Since: 17 Feb 2011 Location: South Posts: 125 |
I thought the same and although there may be a difference it shouldn't throw out the numbers that much surely! will be interested to hear if your numbers change too.. I'm using the vredestein wintracks (sp?) Cheers, J |
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Thu Nov 10 2011 5:25pm |
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JonnyDangerous Member Since: 09 Nov 2009 Location: Reading Posts: 57 |
we can compare notes as that's the tyre i'm putting on too. Just need to wait for it to get a bit colder. |
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Thu Nov 10 2011 5:27pm |
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npinks Site Moderator Member Since: 26 Nov 2007 Location: Watching Posts: 6716 |
There is a tyre change button on my satnav, which resets it to new tyres thought is is the fl2 |
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Thu Nov 10 2011 6:15pm |
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Jmac Member Since: 17 Feb 2011 Location: South Posts: 125 |
Hmmm. I do remember something about that. I will investigate in the morning. Cheers, j |
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Thu Nov 10 2011 7:15pm |
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awd man Member Since: 30 Nov 2010 Location: Malmesbury Posts: 3355 |
iirc 20" rims read slightly quick on the speedo.
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Fri Nov 11 2011 10:30am |
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Beancounter_74 Member Since: 11 Oct 2011 Location: Down here now... Posts: 5796 |
Interesting, mines got 20's as standard, so I would assume they have resolved this
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Fri Nov 11 2011 10:43am |
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awd man Member Since: 30 Nov 2010 Location: Malmesbury Posts: 3355 |
Sorry I should have clarified...
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Fri Nov 11 2011 11:17am |
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Jmac Member Since: 17 Feb 2011 Location: South Posts: 125 |
My car had the 20s as std so that might be an explanation but the difference does seem massive.. |
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Fri Nov 11 2011 1:18pm |
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awd man Member Since: 30 Nov 2010 Location: Malmesbury Posts: 3355 |
so are we talking 20mpg to 24?
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Fri Nov 11 2011 2:34pm |
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Jmac Member Since: 17 Feb 2011 Location: South Posts: 125 |
I don't look at the MPG reading as I know it's optimistic - I just add the two numbers from the range to go and distance travelled since I filled up. All I can say is that it used to add up to 400 miles and now it adds up to 490. If we assume the tank holds 84 (18.5 gallons) litres then that means a jump from 21.6mpg to 26.5mpg.. Seems like an awful lot to me for a very small change in diameter... |
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Fri Nov 11 2011 2:40pm |
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awd man Member Since: 30 Nov 2010 Location: Malmesbury Posts: 3355 |
I'd not take too much notice of range either ..based on real time mpg that the module is telling the ecu...
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Fri Nov 11 2011 2:48pm |
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