1LE to Z/28 Wheel Specs

[Dropspeed]

I acquired a set of used Z/28 wheels that I am going to run on the car with a set of Hankook RS3 (140 treadwear). I figured out the following information for 1LE owners looking to changed to a 305/30/19 tire for the track. ( No, I cant get anymore Z/28 wheels for you ) Note: I have a set of used 305/30/19 Bridgestones on the car in the pictures while I was test fitting them and deciding what tire to try....

Stock 1LE

• F 20x10ET23
• R 20x11ET43
• 285/35/20
• Tire OD: 27.85"
• Gear ratio: 3.91

1LE Top Speed in 1st - 4th gear

• 53mph
• 79mph
• 108mph
• 140mph

1LE with Z/28 wheels and 305/30/19 tires

• F 19x11ET11 (25mm further out than 1LE wheels)
• R 19x11.5ET26 (23mm further out than 1LE wheels)
• Tire OD: 26.2"
• Effective Gear Ratio with 305/30/19 tire: 4.1562

1LE Top Speed in 1st - 4th gear with 305/30/19

• 46mph
• 69mph
• 95mph
• 124mph

Misc: If using 305/30/19 tires on 1LE

• Tire OD is 1.65" shorter
• Car will sit .825" lower than stock.
• Speedo Error at 60mph: +3.8mph
• Speedo Error at 100mph: +6.3mph

I did look at using CTS-V Coupe Rear Rim on all 4 corners for daily driving: (must be a coupe rear to get the 10" width)

• 19x10ET40
• F 17mm inward from a stock 1LE
• R 10mm inward from a stock 1LE
• 285/35/19: 26.85" OD
• 295/35/19: 27.12" OD

Please let me know if my math is off.


Matt

[NJ Drive]

You of all people should know that we have 20 x 11" rears.

[Dropspeed]

Originally Posted by NJ Drive

You of all people should know that we have 20 x 11" rears.

Yeah...That would have been a typo

[Synner]

Whats the clearance like on the inside of the rear tires? Can they be brought in a few mm? -3.5 degrees of camber up front tucks a lot of tire from what I've done with camber plates.

[Dropspeed]

In the pictures the car is sitting with -2.0 up front and -1.0 in the rear.

There is 11mm more clearance than the stock wheel on the backside.

[Mikamaro]

how does it drive ?

[Orange Crush 1LE]

Originally Posted by Synner

Whats the clearance like on the inside of the rear tires? Can they be brought in a few mm? -3.5 degrees of camber up front tucks a lot of tire from what I've done with camber plates.

Synner,

How do you like -3.5 degrees camber in the front? How's tire wear on the track? I'm at -2.9 now and since I'm running Hoosiers on the track I'm thinking of going to -3.5 or maybe -4 degrees. I know a racer that is at -5 degrees front but Justice Pete advised that I go -4 max, even for a track-only car.

[woodside783]

I would go with what Pete said he knows his stuff

[Need4speed_motorsports]

Looks awesome, where able to find the fender extensions, are those even bolt ons?

[Synner]

Originally Posted by Orange Crush 1LE

Synner,

How do you like -3.5 degrees camber in the front? How's tire wear on the track? I'm at -2.9 now and since I'm running Hoosiers on the track I'm thinking of going to -3.5 or maybe -4 degrees. I know a racer that is at -5 degrees front but Justice Pete advised that I go -4 max, even for a track-only car.

Its working well although I think I need to reduce toe slightly due to how the plates effect toe as you adjust them. Wear is much more even now and visually I know temps are getting closer to being even across the tire. A tire pyrometer is on my to do list to further dial it in. Previously with -1.5 I was only using half my tire, if that, and thrashing the outer edge. Chunks from the outer rib were flying off from the stress and heat while the insides looked new.


The reason why you don't want too much camber is keeping things balanced with the rear where you normally run half the front setting. You reach a point and your camber in the rear gets too high and you will have a hell of a time planting the power in straights and powering out of turns. High HP RWD cars will always need to find a balance. If we were mid engined we could push the envelope more.

[Dropspeed]

Originally Posted by Mikamaro

how does it drive ?

I think it rides the same if not better than stock as the wheel/tires are 5lbs lighter per corner...side wall is almost the same at 91mm vs 97ish mm stock. Turn in is good and the seat of the pants acceleration is better in all gear (as the smaller tires act like a gear was installed)

Originally Posted by Need4speed_motorsports

Looks awesome, where able to find the fender extensions, are those even bolt ons?

No luck as of yet...Z/28 wont work on the 2013 as it requires the full ground effect package to be install. The front seem to be just tucked enough to be OK...The rears toss water, debris, stuff up the side of the rear quarter panel.

Matt

[Orange Crush 1LE]

Originally Posted by Dropspeed

No luck as of yet...Z/28 wont work on the 2013 as it requires the full ground effect package to be install. The front seem to be just tucked enough to be OK...The rears toss water, debris, stuff up the side of the rear quarter panel.

Matt

Matt, lookin good. Do you have any idea how hard it would be to morph a Z/28 splitter and front flares to a 2013 1LE like ours? While I'm happy with my wing, I need to improve front downforce to better balance the car aerodynamically as my APR splitter isn't quite enough.

[Synner]

You need the 2014 front end to make it work. Been pondering that plus the ACS Z-style spoiler but not sure how to terminate the wheel flares/rocker situation since I have zero interest in a rear end conversion. Might need to make a small custom piece or two out of fiberglass but no time for that.

I'm curious to see what the aero package from GM includes since it seems to be a "partial" setup around the sides of the car.

[Synner]

• Camaro Z/28 Aerodynamics Package – Compatible with 2014 model and later Camaros, this package includes four components that contribute to the aerodynamic performance of the Z/28: front splitter, front wheel-lip extensions, underbody belly pan, and rear spoiler.

I figure I can sell the spoiler if I get it and do the front end conversion. Would need wheel well liners too though. Just not sure how they terminate the lip extension to rocker area.