1LE to Z/28 Wheel Specs

[Norm Peterson]

It's the inward lateral clearance I'm interested in knowing. I have to use pairs of feeler gauges totaling around 0.045" and needed to fab up an 0.025" spacer for the right front to kill off a rub under unusual conditions. From that perspective, having as much less +offset on your front 11's than I have on my front 11's sounds like there's still a good bit of room.

Here's a couple of thumbnails for ya.


Norm

[Nick S]

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

Hey Matt,
When talking with Al O about this did he indicate if he was referring to a 1LE with the new 14 hoods? I know the Z/28 front splitter is advertised that it will handle 200lbf at the corners but I'm sure the Z/28 is capable of generating this much downforce. The 1LE doesn't come with the same front splitter or the belly pan so I'm curious if the numbers Al was talking about were in reference to a 1LE or the Z/28. I guess either way the point here is the 14 hood allows a lot more front end down force to be created compared to the 13 hoods. But knowing which car he was referencing with his numbers would be nice to clarify as well.

Thanks.

[Dropspeed]

Originally Posted by Nick S

Hey Matt,
When talking with Al O about this did he indicate if he was referring to a 1LE with the new 14 hoods? I know the Z/28 front splitter is advertised that it will handle 200lbf at the corners but I'm sure the Z/28 is capable of generating this much downforce. The 1LE doesn't come with the same front splitter or the belly pan so I'm curious if the numbers Al was talking about were in reference to a 1LE or the Z/28. I guess either way the point here is the 14 hood allows a lot more front end down force to be created compared to the 13 hoods. But knowing which car he was referencing with his numbers would be nice to clarify as well.

Thanks.

We were talking about putting the Z/28 spoiler on my 2013 1LE and it doing wheelies.....In my mind we were talking lift in a 13SS to a down force in a 14SS???? But this was in Oct/Nov of 13 so I don't really recall. I do remember asking specifically if a 14 hood would help my 13 reduce lift and the answer was yes.

Matt

[Dropspeed]

This is for some of the above questions. So I was out on Woodward Ave (google it) tonight as it is the week before dream cruise and met Tom Peters and his wife (search Tom Peters GM) . He introduced me to an aerodynamics Enginer at GM but I never caught his name.

I ask flat out if a put a 2014 hood with vent on my 2013 would I reduce the lift and create downforce. The answer was Yes I would reduce the lift, however I would not create downforce with just the hood. We also talked about good vent placement and how it is critical to function. GM placed the hood vent on the correct location on the Camaro for function. He was talking to one of my good friends at Chrysler about how the vents on the SRT cars are not in the correct spots and apparently this was done for styling reason over aerodynamics. GM chose aero first. (Yeah us)

We talked about the balance of the car and how if you add a rear spoiler you need to make changes to the chin spoiler ect. as you are more likely to upset the balAnce than improve it if you change one or the other or both incorrectly.

[CHMSC]

Originally Posted by Dropspeed

This is for some of the above questions. So I was out on Woodward Ave (google it) tonight as it is the week before dream cruise and met Tom Peters and his wife (search Tom Peters GM) . He introduced me to an aerodynamics Enginer at GM but I never caught his name.

I ask flat out if a put a 2014 hood with vent on my 2013 would I reduce the lift and create downforce. The answer was Yes I would reduce the lift, however I would not create downforce with just the hood. We also talked about good vent placement and how it is critical to function. GM placed the hood vent on the correct location on the Camaro for function. He was talking to one of my good friends at Chrysler about how the vents on the SRT cars are not in the correct spots and apparently this was done for styling reason over aerodynamics. GM chose aero first. (Yeah us)

We talked about the balance of the car and how if you add a rear spoiler you need to make changes to the chin spoiler ect. as you are more likely to upset the balAnce than improve it if you change one or the other or both incorrectly.

So I take it the same would apply if we did a ZL1 hood swap or an ACS vent?

Did you happen to inquire what is the best way or what would work the best to balance the car out as far as hood, splitter and spoiler besides taking all of the Z28's aero's and applying them to our cars if we could even get the parts which we or most of us can't?

[Spoolin]

Originally Posted by Norm Peterson

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

These numbers are closer to the actual numbers for the stock wheels. I hit the rev-limiter in 3rd gear at 104mph but that's also because of tire expansion. 102mph is closer I would think.

[X25]

Originally Posted by Spoolin

These numbers are closer to the actual numbers for the stock wheels. I hit the rev-limiter in 3rd gear at 104mph but that's also because of tire expansion. 102mph is closer I would think.

Is that reading from a high-frequency GPS, or car's speedometer? Speedometers are usually a few MPH off, if not more.

19x11 Forgeline CF5V is about 23-24 lbs, and can be used in all 4 corners. I (currently) think it would be the best compromise for 1LEs. They also have 19x12 available; might be interesting to try.

If you guys think that .5" wheel width difference in the rear (11" v.s. 11.5") and narrower track overall compared to the Z/28 is too important, then I suggest you first attack the issue of very heavy brakes and inferior struts we have on 1LEs (and even heavier with ZL1/CTS-V brake upgrade). I bet a featherlite rotor like the carbon-ceramic rotors found in the Z/28 makes most of the difference in suspension performance at the road-course track. Combined with the additional weight savings from using CF5Vs, the gap will get even closer. Long story short, my opinion is that a substantially lighter BBK with a real 2-piece rotor (StopTech kits come to mind) + Forgestar CF5V 19x11 square set-up might be closer to Z/28 performance than using real Z/28 wheels. Only then you might consider the Z/28 struts, too. I would actually not even buy the Z/28 struts without a lighter brake system and wheels, since GM has very highly tuned the struts with the DSSV system as a whole, as explained in details in their press releases.

[X25]

On the Chevrolet Camaro, Do The Tires Make The Car?
The Camaro 1LE and Z/28 Swap Rubber to Find Out


Read more: http://www.motortrend.com/roadtests/...#ixzz3CyIQgkDT

[Spoolin]

Originally Posted by X25

Is that reading from a high-frequency GPS, or car's speedometer? Speedometers are usually a few MPH off, if not more.

I was taking the reading from the HUD, so if it's as far off as your saying than maybe I could be actually hitting 108 or what not. I didn't know their calibration could be off by that much.

I'm thinking of bumping the rev limiter up a little as I hit it a few times at certain tracks.

[Spoolin]

Originally Posted by X25

On the Chevrolet Camaro, Do The Tires Make The Car?
The Camaro 1LE and Z/28 Swap Rubber to Find Out


Read more: http://www.motortrend.com/roadtests/...#ixzz3CyIQgkDT

I really wish they woulda put those two cars on the track to get some lap times, or do some auto crossing or something. That instrument testing doesn't tell the whole story.

[Dropspeed]

I do not have the Trofeo R tires, but I do have Z/28 wheels with a 305/30/19 Hankook RS-3 tire on all 4 corners, (CTS-V brakes, Pedders Springs, Z/28 seat.....)

Fastest lap at Gingerman:
Stock 20"s and 285/35/20 Goodyear Supercar G2: 1:44.41 April 2014
Z/28 19s with the aforementioned RS3s 305/30/19: 1:44.01 Sept 12, 2014
I have 17+ years of racing and instructing experience there, 45K+ miles on the track.

The car does not feel as confidence inspiring at the limit with the 19s as it was so well balanced before. It feel as if I have hit the limit of the stock damper/Pedders spring suspension and it would benefit from stiffer springs.

[Nick S]

Originally Posted by Dropspeed

I do not have the Trofeo R tires, but I do have Z/28 wheels with a 305/30/19 Hankook RS-3 tire on all 4 corners, (CTS-V brakes, Pedders Springs, Z/28 seat.....)

Fastest lap at Gingerman:
Stock 20"s and 285/35/20 Goodyear Supercar G2: 1:44.41 April 2014
Z/28 19s with the aforementioned RS3s 305/30/19: 1:41.01 Sept 12, 2014
I have 17+ years of racing and instructing experience there, 45K+ miles on the track.

The car does not feel as confidence inspiring at the limit with the 19s as it was so well balanced before. It feel as if I have hit the limit of the stock damper/Pedders spring suspension and it would benefit from stiffer springs.

Matt,
So with your experience and engineering background do you have any theories as to why the lighter and wider wheel set up would cause the car to feel less balanced? I'm just trying to understand the dynamics going on here. Everyone always touts that less unsprung mass and less rotating mass will make the car handle better and your lap time does show an improvement but yet you state that the car feels less confidence inspiring and not as well balanced. I'm curious as to what dynamic is going on that stiffer springs will help overcome? Not questioning your results just trying to understand the bigger picture here on what's going on.

Oh and since I know you did not like the factory seats at all how much more did you like the Z/28 seat? It would be nice to know how much of an improvement the Z/28 seats are for keeping you planted in your seat.

Thanks.

[Dropspeed]

Originally Posted by Nick S

Matt,
So with your experience and engineering background do you have any theories as to why the lighter and wider wheel set up would cause the car to feel less balanced? I'm just trying to understand the dynamics going on here. Everyone always touts that less unsprung mass and less rotating mass will make the car handle better and your lap time does show an improvement but yet you state that the car feels less confidence inspiring and not as well balanced. I'm curious as to what dynamic is going on that stiffer springs will help overcome? Not questioning your results just trying to understand the bigger picture here on what's going on.

Oh and since I know you did not like the factory seats at all how much more did you like the Z/28 seat? It would be nice to know how much of an improvement the Z/28 seats are for keeping you planted in your seat.

Thanks.

Hi Nick,

Clarification: The 1LE in stock form is a great package that handles well on track. The suspension, brakes and wheel/tire combo complement each other so well it is the perfect "balance" of go, stop and handling for a track day car.....(OK, so maybe "balance" wasn't the correct choice, but it made sense in my per-caffeinated mind!!)

From GM authority recently about the MT swap:

"MT said the 1LE felt razor sharp on its Goodyears but “mushy” on the Pirellis."

The wheel and tire change was by far one of the best changes I made as the car feels lighter, more nimble, and faster even though the lap times don't directly indicate a significant improvement. But as stated above it does not feel "razor sharp", specifically during transitions. According to my data I was hitting about 1.02gs on the stock 20" wheel tire combo and about 1.04gs with the 305/19s Friday. (Of course weather, track temps, etc are factors 5 months apart).

Lowering the the Cg and increasing the track I have decreased both longitudinal and lateral load transfer, so this may be what my seat of the pants sensors are missing or not sensing any longer?? I have another weekend at Grattan on the 27/28 and will try to pinpoint what I think is different from the drivers seat. But it does not feel as sharp, hence my deduction that I need to upgrade the suspension to match the grip of the new wheel/tire set-up.....

LOVE the seat!!!! It did everything it should have done for a tracked minded street seat. On a 1-10 scale the stock seat gets a 1 or 2 as it is comfy, but support is aweful. The Z/28 Recaro gets a 7+ and a true race seat would get a 10+ in my opinion.

Matt

[Nick S]

Originally Posted by Dropspeed

Hi Nick,

Clarification: The 1LE in stock form is a great package that handles well on track. The suspension, brakes and wheel/tire combo complement each other so well it is the perfect "balance" of go, stop and handling for a track day car.....(OK, so maybe "balance" wasn't the correct choice, but it made sense in my per-caffeinated mind!!)

From GM authority recently about the MT swap:

"MT said the 1LE felt razor sharp on its Goodyears but “mushy” on the Pirellis."

The wheel and tire change was by far one of the best changes I made as the car feels lighter, more nimble, and faster even though the lap times don't directly indicate a significant improvement. But as stated above it does not feel "razor sharp", specifically during transitions. According to my data I was hitting about 1.02gs on the stock 20" wheel tire combo and about 1.04gs with the 305/19s Friday. (Of course weather, track temps, etc are factors 5 months apart).

Lowering the the Cg and increasing the track I have decreased both longitudinal and lateral load transfer, so this may be what my seat of the pants sensors are missing or not sensing any longer?? I have another weekend at Grattan on the 27/28 and will try to pinpoint what I think is different from the drivers seat. But it does not feel as sharp, hence my deduction that I need to upgrade the suspension to match the grip of the new wheel/tire set-up.....

LOVE the seat!!!! It did everything it should have done for a tracked minded street seat. On a 1-10 scale the stock seat gets a 1 or 2 as it is comfy, but support is aweful. The Z/28 Recaro gets a 7+ and a true race seat would get a 10+ in my opinion.

Matt

Thanks for the clarifications Matt. I'll stay tuned for more of your reviews of the wheel tire set up.

So if I am interpreting your theory on the razor sharpness of the 1LE with the Z/28 wheels you are thinking that by reducing the load transfer each corner is not seeing as much of the cars weight in a corner and therefore the car is more prone to "sliding" or "pushing" more and then does not respond to the steering inputs as quickly? Since total friction force between the tire and pavement is directly proportional to the normal force between the two surfaces, the tire doesn't have as much normal force and therefore has a lower total friction force.

I know when I put my Strano Suspension on my 2002 Camaro SS he gave me some tips on adjusting the shocks and from what I remember he said if I wanted quicker steering response from the front to make both front's stiffer because the stiffer shock would lead to a quicker steering response (unless you know differently and can correct my understanding of this). So in my mind that seems to follow your theory here. Maybe the 1LE springs/dampers are not stiff enough to respond as quickly.

I'm guess this means you might be considering the Z/28 suspension set up?

The nice part about you doing this in steps is in a small way you are proving to people that the suspension needs to be considered as an entire system (I know you fully understand this but it seems many people think they can cherry pick parts and still have a great suspension).

Congrats on finding a good seat too. I know that was one area you were really getting irritated by was the seat not keeping you planted very well. Hard to drive a car when you are trying to worry more about keeping yourself from flying around the inside of the cabin.


Thanks.

Nick S.