1LE to Z/28 Wheel Specs

[Dropspeed]

Originally Posted by Orange Crush 1LE

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.

Thank you.

I looked at the Z/28 fender flare installation and there are brackets that secure to the front fascia and then the remainder on the front fender is glued in place with what appears to be a single attachment at the body where the rocker is.

Both the front and the rear of the fender flare are cut out to fit aroudn the splitter in the front and the rocker in the rear....without those there will be a gap.

I added the ZL1 deflectors in the front, but they barely cover a 1/2 of the portion of the tire that sticks out.

What is the top speed you are hitting on the tracks you run?

-Matt

[Orange Crush 1LE]

Looks pretty gnarly, maybe I'll wait for a good aftermarket solution. That does look solid the way it's tied in to the car on the Z/28.

I think about 140 MPH is what I'll hit on the faster tracks. People tell me that my rear end is compressed and my front end is up a little on the straights at Buttonwillow, where I think I'm going about 130 to 135 MPH, so I'd like a bit more front downforce. I'm going to raise the rear a little to compensate for the wing's downforce, per Justice Pete's recommendation.

Todd

[Dropspeed]

Originally Posted by Orange Crush 1LE

Looks pretty gnarly, maybe I'll wait for a good aftermarket solution. That does look solid the way it's tied in to the car on the Z/28.

I think about 140 MPH is what I'll hit on the faster tracks. People tell me that my rear end is compressed and my front end is up a little on the straights at Buttonwillow, where I think I'm going about 130 to 135 MPH, so I'd like a bit more front downforce. I'm going to raise the rear a little to compensate for the wing's downforce, per Justice Pete's recommendation.

Todd

Yeah, you are hitting higher speeds than I run on the local tracks to me. I hit about 130+ on one straight at Grattan, but Waterford is 110mph and Gingerman is 120mph...I haven't run the car yet at Mid-Ohio.

I spoke to Al O at a party last fall about putting the Z/28 spoiler on my car and he said absolutely do not do it unless you use the complete kit. I was told the car would be "doing wheelies" down the track as it creates so much down force.

Have you thought about a 14 hood on the car instead of playing with the suspension? I was told that would help keep the front end down as our 13s create 150lbs of lift at (I think it was) 150mph where the 14s create (I cant remember the number) 200lbs of down force at the same speed. The hood is major contributing factor as it relieves the under hood pressure creating the lift.....


Here are a couple new pics from yesterday...the Hankook RS3 are as buldged or square as the Bridgestone were in the same 305/30/19 size. It tucks the tires a bit more.

Matt

[Dropspeed]

Originally Posted by ZL575BumbleBee

First off Drop speed I love your car and the color and thanks for the tip on the hood as I have been on the fence of adding that to the list when I do the front end conversion.

Thanks! I appreciate it..

I have been looking at the hood and vents for awhile.

I thought about Hex Vents a bit, but there is a reason GM put the vent in the spot they did (when they could have put it anywhere) VS. the Hex Vents which are a tribute to the late 60s Camaro.

I also like the way the factory deals with water.....I am pretty sure I am just going to put a 14+ hood on the car eventually.

Matt

One more picture I just took this morning...I couldn't be happier with the wheels on the car.

[SSeric]

I have nothing beneficial to contribute. Just here to check out the wheels.

[Norm Peterson]

Originally Posted by Dropspeed

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

Please let me know if my math is off.


Matt

What are you assuming for a redline rpm?

I get these numbers, which don't show as much drop in speed with the 305/30-19's. These numbers also consider tire tread squirm effects to cost about 3% off of the speeds theoretically calculated from tire diameter, so they're probably just a little more realistic.


Norm

[Dropspeed]

Norm,

The max speed per gear for the stock tires I pulled from the internet.

Max speed per gear for the 305/30/19 I used 6200rpm, and rounded up....So we are "close" there. I also used the RPM provided on the tire rack site of 791

I like and trust your program better!

Thanks,
Matt

[Mean Green Z28]

Originally Posted by Norm Peterson

What are you assuming for a redline rpm?

I get these numbers, which don't show as much drop in speed with the 305/30-19's. These numbers also consider tire tread squirm effects to cost about 3% off of the speeds theoretically calculated from tire diameter, so they're probably just a little more realistic.


Norm

wow I'd like a copy of that file! makes mine look retarded, haha http://www.camaro5.com/forums/showthread.php?t=369831

[Orange Crush 1LE]

Originally Posted by Dropspeed

Yeah, you are hitting higher speeds than I run on the local tracks to me. I hit about 130+ on one straight at Grattan, but Waterford is 110mph and Gingerman is 120mph...I haven't run the car yet at Mid-Ohio.

I spoke to Al O at a party last fall about putting the Z/28 spoiler on my car and he said absolutely do not do it unless you use the complete kit. I was told the car would be "doing wheelies" down the track as it creates so much down force.

Have you thought about a 14 hood on the car instead of playing with the suspension? I was told that would help keep the front end down as our 13s create 150lbs of lift at (I think it was) 150mph where the 14s create (I cant remember the number) 200lbs of down force at the same speed. The hood is major contributing factor as it relieves the under hood pressure creating the lift.....


Here are a couple new pics from yesterday...the Hankook RS3 are as buldged or square as the Bridgestone were in the same 305/30/19 size. It tucks the tires a bit more.

Matt

That was pretty close to the wording that my friend used at the track- I was doing "wheelies," LOL. Clearly Al is right on, because my APR splitter and Hex Vents aren't enough to balance the wing.

As crazy as it sounds, I might just price out what a pair of '14 Z/28 fenders, Z/28 nose, splitter and hood would cost. I have a friend that races and can buy anything made including restricted Z/28 parts. I could install them myself to save money and shop around to find a paint shop that won't charge me an arm and a leg. I don't need the perfect paint job for a track car. This might prove too expensive but I may look into it. At some tracks, this car is very fast but with competition fierce in NASA, I need to get the aero right. I may be leaving a good second+ per lap on the table with my wheelies and the drag associated with my tires sticking out of the fenders.

Those new tires tuck nicely, winning combo!

[X25]

Let me play the devil's advocate: I love the idea of losing rotational mass, but one can easily do so with 19" wheels that do fit right. It's a great idea to use OEM parts for upgrades whenever available, but these just don't fit right. TSW Nurburgring 19x10.5 wheels, good for 285/295 tires are 22.4 lbs each, so they save similar weight, yet would not stick out with the right offset. There are more expensive 19" wheels also available at below 20 lbs and as wide as 19x11".

By the way, Dropspeed, your car was already lowered, right? Now that it's even more lowered with lower diameter, do you have any rubbing or interference?

[Norm Peterson]

I get what you're saying - I play the devil's advocate from time to time as well.

10.5" is half a step down from the 1LE as far as the rear wheel width is concerned. If you're going to do 'square', make them all 11" - which is still only a partial solution to reaching a level playing field with the Z/28.

Lateral and yaw stiffness support for the tire tread really means more than rotational inertia, especially if you're intending to go with wider tires than 285/35's.

Conventional opinions regarding appearance won't shave anything off lap times and can't win races or autocrosses for you. If you're serious enough to run the numbers because you're considering a wheel & tire upgrade for the 1LE in the first place, you'll know what the appearance you'll likely end up with means. And that'll be good enough to settle any of your own appearance concerns.



On edit - Dropspeed, how much camber are you running up front?


Norm

[Dropspeed]

X2S.

No rubbing issues at all....but I now scrap the chin entering and exiting my driveway.

The look is not for everyone. With the RS3 the top of the tires is actually lined up exactly with the fender and quarter. It's the rest of the tire that sticks out.

Of course there are other wheel options, but I really wanted the Z/28 wheels and will sacrifice fashion over function to use them.

Norm

I am running -2.0 in the front. I didn't change it because I want to track the car with the -2 and read the tire wear. The Z/28 race spec from GM is -1.5 +.5 , so -2.0 max. Now I don't have the Z/28 springs or dampers. But we will see how it works.

Matt

[Norm Peterson]

Must be the angle you took the pictures because in the bottom two pictures it doesn't look anywhere near that much at all.

Those front wheel offset numbers sound awfully low to me, given that both your car and mine ride on struts up front - how much tire and wheel clearance to the strut do you have with the wheels pointed straight ahead?


Norm

[Dropspeed]

Originally Posted by Norm Peterson

Must be the angle you took the pictures because in the bottom two pictures it doesn't look anywhere near that much at all.

Those front wheel offset numbers sound awfully low to me, given that both your car and mine ride on struts up front - how much tire and wheel clearance to the strut do you have with the wheels pointed straight ahead?


Norm

Maybe?? Fronts are at -2.0 and rear is at-0.9

From the top of the tire to the spring base I just gained another .8" of clearance in the front and lost 1MM inward (Inside sidewall to strut)