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Old 23rd October 2019, 13:07   #11
RoverP480
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Without knowing the specific fuel consumption curve for the engine , one cannot really say what the effect will be by altering the engine revs at the same road speed . If say at 70mph the engine is running at its optimum speed for fuel consumption, altering it either way will make it worse. If though it moves the engine speed to a more favourable part of the curve it will be better, but if it moves to a less favourable part it will be worse. One is also moving it about on the torque and power curve as well so you end up with multiple effects . I suggest moving it by 2.5 % is unlikely to show a noticeable effect. One is more likely to notice the ride changing.
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Old 23rd October 2019, 16:33   #12
meterman66
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Hi

I'm only thinking of changing as I've just bought my latest conny with 16" forks that really don't do it for me in the looks dept and tyres are all pretty close to the limit and require replacement.

As there are a few sets of 18s on tinternet with newish tyres at around the £100-£150 price range so was going to kill 2 birds with 1 stone so to spk.

Many thanks for all your input

Col
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Old 23rd October 2019, 18:42   #13
T-Cut
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To be sure your chosen wheel/tyre combination complies with the spedometer regulations and for your insurance to remain valid, I'd suggest you stay within the sizes recommended in the Handbooks.





2004 Handbook (introduced 18" rims)

Last edited by T-Cut; 23rd October 2019 at 18:47..
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Old 25th January 2020, 17:21   #14
MarkS
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Honest John recommends that tyres should be a minimum of '55 profile to avoid rim damage due to potholes in the UK. Seems sensible advice. A blowout at high speed due to pothole damage does not bear contemplating, simply for a 'nicer' look. You only have one life.

But it is your choice.

Last edited by MarkS; 25th January 2020 at 17:34..
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Old 25th January 2020, 18:18   #15
peelaaa
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The 18 inch do fill the wheel arches better but car will be higher off ground unless the springs are shorter.
My car had 18 inch when I bought it but went back to the 16 inch . Car sits at correct height now and ride much better.
I am sure the mpg was slightly worse with the 18 inch but then it may have been the tyres.
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