Results of 20x8" and 20x9" stock rim test

[gwbates3]

I have been wanting to know for months how the performance is both handling and mpg running RS stock 20" rims as the standard configuratino with 8's with 245s on the front and 9's with 275s on the rear versus all one size on all corners.

Finally landed a full set of stock take offs at a good price and over the last 4 weeks have completed the test.

Results are:
20x9 with 275s on all corners
-Handling
Best of the 3.overall the best handling with cornering and hard carving.Never felt like the car was going to fishtail and stance was considerably better. I believe race terms are "tight" vs. "loose". This setup was tight! This configuration still felt like there was traditional understeer, however with a firm hand there was considerably less feeling of a nose dive while going into a corner hard.
-MPG
Worst of the 3, as expected. Over 400 miles the MPG averaged 23.3 with this setup, which was worse compared to the stock and smaller configurations. Average speed was over 45 mph, with a balance of city and highway driving.

20x8 with 245s on all corners
-Handling
Worst of the 3. This setup on the 8s especially immediately following the 9s was very loose. First day out following some of the hard carving I had been used to with the meaty 275s was almost comical. Fishtailing and single wheel spin on cornering was occurring without effort, and to the point where I really had to watch out on narrow single lane turns with curbs to avoid rashing on. Standstill burnouts from dead stop are way too easy with this setup. Nose dives on hard cornering and effect of road construction where lines had been chewed out of road lanes caused dramatic impact to steering line on both front and rear effect.
-MPG
Best of the the 3 as expected. Mileage came in above 25 MPG. I reset the average twice as the mix was too heavily weighted to city frivetime compared to the prior run, so there was no hard # for this run. Both averages exceeded 25.0 mpg, so I am comfortable putting this number out there on the conservative side.

Stock configuration 20x8x245s on front and 20x9x275s on rear
-Handling
Traditional understeer and nose diving at cornering with stock suspension setup. middle as far as ollse or tight configuration.
-MPG
Averaged 24.4 with city highway mix of 50/50.

[rydahog]

Well done,,i think (for me) i will take the better handling with a bit lower mpg's over the other tests.

[rolnslo]

Nice comparison but be careful with the MPG numbers. IMO, you didn't run long enough on each setup to truly be able to compare the MPG numbers equally.

I ran the stock 20x8/20x9 setup for 25k miles, then switched to 20x9 all around for another 16k miles. There was no noticeable change in MPGs and my car was a daily driver commuting over the same routes for the entire 41k miles. I also tracked (nearly) every tank of gas and MPG.

http://www.camaro5.com/forums/showpo...48&postcount=5

[Ohten]

Thanks for the write up,I have four 275/40 20 in my garage waiting to go on my car.Though I am not concerned about the mpg,I was more concerned about the handling aspect of the car.You just gave me what I wanted to know and expected with this setup.

[jmart53]

nice testing

[Doc]

I have 19x9.5 with 275's all the way around and combined with full Pedders bushings in the suspension the car handles like a dream. Solid, planted, snug... hugs the road like a magnet and no understeer. The car just goes where you point it. Ride isn't harsh either.

Nice test!

[gwbates3]

Right on with the short duration on total miles...I have a friend who rashed 2 of his wheels and we were trying to get through it on a fairly short window.
Only option I have not tried is the 8s all around with the 275s all around if anyone has that info for comparison.

I also saw on several threads that after a good front end alignment many have been able to get rid of some of the understeer based on some tested and true results.

I have been approaching this from a low $$$ spend perspective first.
I have the SS springs and swaybars yet to go on, and after this test am ready to put the 20x9s on and not look back unless there is similar result with the 20x8 with the 275s swapped in. Just a little hesitant to take them to "any" shop as I have heard some really bad stories of rim scratching from some of the shops.

[rhino200099]

Looking to trade my 20x9 for 20x8. Polished wheels