just fitted 18" and mpg reading on display has dropped by 10mpg

[rugbymad]

can this be changed via vag com?  gotta be cheaper than 4 tryes?

[bobbarley]

I don't think so, as the tyres are throwing your speedo out as well.

[rugbymad]

sorry just checked the tyres they are 225/40/18 and not the 45> thank f***.

still that aint helped really lol

steph

[pazz]

sorry just checked the tyres they are 222/40/18 and not the 45> thank f***.

still that aint helped really lol

steph

Just about to say 225/45/18s are way out! And I'm assuming you mean 225/40/18.

Could be a lot heavier wheels, but 10mpg heavier - wouldnt really think enough to make that big a difference

[Egbutt Wash]

205/55/16 gives a diameter of 16" (40.64 cm) + (20.5x0.55)x2 = 63.19cm, Circumference = 198.5 cm
225/40/18 gives a diameter of 18" (45.72 cm) + (22.5x0.4)x2 = 63.72cm, Circumference = 200.2 cm

So the new rubbers are just 0.8% bigger than the old ones. 

47 mpg would be 46.6 mpg.

35 mpg suggests you are feeling good about the new wheels and driving with some verve.

[rugbymad]

LOL DO YOU KNOW I WISH I HAD BEEN TANNING IT BUT DECIDED TO KEEP SAFE DUE TO NEW WHEELS AND ROAD CONDITIONS SNOW ICE ETC.
but thanx for the calculations . by the looks of it it shouldnt make that much difference..

in my hyundai coupe i used to reset the ecu by disconnecting the batt and pumping the brakes to dischare any juice left, and when reconnected it would learn your drive style and resort to that. i.e if you drive like a nutter it put more juice in and reflects on the dash but if you drive carefully ..

can this be done on a mk5?

[winrya]

The rolling radius is exactly the same so should see no difference at all.  If they are genuine monza's they should be extremely light as they are made using a new bbs hollow technology.

[No Golf Clubs at all]

How many miles had you driven before you arrived at the new figure and did you rely on the onboard computer or did you brim it and do the manual thang?
 

[rugbymad]

those figs were off the computer but it always been at 47 ish, just brimmed it today so will run her dry to see what i am getting.

[pw motorsport]

As suggested above, the weight of the wheels will affect performance and fuel economy.

I use a A6 2.0 TDI for long trips through Europe, I run a light 18" wheel. A few months back I sold the demo wheels and fitted some old 19" reps that I had.
The MPG was reduced from 48/50 mpg to 40/42 mpg. Plus it was a lot slower.