Why do you have to go lower profile on 20's?

[ILLFLY]

do you think fuel economy would change from for 245/30r22 to 245/35r20?

 

[Sean880]

do you think fuel economy would change from for 245/30r22 to 245/35r20?

The FC should hardly change at all. You will have a slightly higher gearing with the tyre size change up so if anything the FC should be slightly/marginally better in a mix of city and country driving.

With the 245 30 22 tyre (707 mm diameter) you have approx 4% larger tyre diameter and this translates to approx 4% LESS wheel revolutions for every km or mile you travel compared with the smaller 245 35 20 tyre (680 mm diameter). ( The larger diameter 22" wheel and tyre does weigh considerably more though assuming the use of a similar type wheel).

You improve your car's handling by decreasing the unsprung weight not by increasing it which is why putting 22 inch wheels and tyres (thus significantly increasing the unsprung weight) on a Commodore is usually for the w@nker group. They do think it looks great and really blingy though with all that wheel and minimal tyre profile.

This guy more than demonstrates that you do not need to put massive diameter wheels on you VE to make it look great...............
http://www.canibeat.com/2011/07/stance-pontiac-g8-hellaflush/#more-29914

 

[TraidMarc]

The FC should hardly change at all. You will have a slightly higher gearing with the tyre size change up so if anything the FC should be slightly/marginally better in a mix of city and country driving.

With the 245 30 22 tyre (707 mm diameter) you have approx 4% larger tyre diameter and this translates to approx 4% LESS wheel revolutions for every km or mile you travel compared with the smaller 245 35 20 tyre (680 mm diameter). ( The larger diameter 22" wheel and tyre does weigh considerably more though assuming the use of a similar type wheel).

You improve your car's handling by decreasing the unsprung weight not by increasing it which is why putting 22 inch wheels and tyres (thus significantly increasing the unsprung weight) on a Commodore is usually for the w@nker group. They do think it looks great and really blingy though with all that wheel and minimal tyre profile.

This guy more than demonstrates that you do not need to put massive diameter wheels on you VE to make it look great...............
Cars

Yes I agree, on the w@nker bit too.
How did you come up with the OD? I calculated it at 632(R22) and 593(R20) just want to know what i missed. It did how ever prove that I could go 245/45R20 as it would work out still a little less than the 245/30R22 so the clearance of the struts should be fine.
Cheers.