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Old 09-15-2014, 12:38 PM   #43
Orange Crush 1LE

 
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Quote:
Originally Posted by Dropspeed View Post
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.
Very interesting that you are running 3.4 seconds faster on the new set up yet the car feels less confidence inspiring. 3.4 seconds is huge. So the limits are higher but less stable at the limit, so to speak? Are you thinking about upgrading to coilovers, or what's your next move?
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Old 09-15-2014, 01:29 PM   #44
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Quote:
Originally Posted by Orange Crush 1LE View Post
Very interesting that you are running 3.4 seconds faster on the new set up yet the car feels less confidence inspiring. 3.4 seconds is huge. So the limits are higher but less stable at the limit, so to speak? Are you thinking about upgrading to coilovers, or what's your next move?

AHHHHH that was a huge fat finger. It should be: 1:44.41 vs 1:44.01....

I am actually eyeballing the full Z/28 suspension set-up.

-Matt
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Old 09-15-2014, 02:32 PM   #45
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Originally Posted by Dropspeed View Post
AHHHHH that was a huge fat finger. It should be: 1:44.41 vs 1:44.01....

I am actually eyeballing the full Z/28 suspension set-up.

-Matt
So you probably have lost some time due to lower confidence in the set-up, considering the lighter wheels and grippier tires (RS-3s compared to G:2s) should have let you cut a good chunk of time automatically. I wonder if the stock springs would fare better for you; the shocks would have more travel to work with.

If I were going the route of Z/28 full suspension, I'd also get a BBK ($~2.8K fronts, $1.9K rears but might not be necessary) to lower the un-sprung suspension weight as much as possible to match Z/28's. After all, those DSSVs are very highly tuned to match the weight of the Z/28 components, which includes featherlight carbon-ceramic rotors. Otherwise, your compression and dampening will be a bit off (though probably still much better matching than your current 1LE shocks).

You should also note your CTS-V brakes are even heavier than the stock 1LE brakes. ZL1 2-piece rotors are a big compromise: they do allow better cooling that GM needed badly for ZL1, but they do not provide any weight advantage, which I suspect is for keeping costs low, which makes a lot of sense from GM's point of view (better have a heavy 2-piece than not having a 2-piece at all).

Finally, have you upgraded any bushings? More mechanical grip will cause more deflection from your bushings. They're painful to install, but you could address all important bushings for about $500. Z/28 package also replaces some of those bushings as far as I can see.
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Old 09-15-2014, 03:24 PM   #46
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Finally, have you upgraded any bushings? More mechanical grip will cause more deflection from your bushings. They're painful to install, but you could address all important bushings for about $500. Z/28 package also replaces some of those bushings as far as I can see.
My thoughts as well. More grip = more pitch and roll from both the suspension's ride and roll stiffnesses and from the compliances at the suspension attachment points. This would include things like cradle bushings.

Camber that's more negative would generally help in the corners, though at some cost in braking and acceleration grip.


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Old 09-15-2014, 06:26 PM   #47
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This is a good bit of information. Seems one would be best moving to an R comp on the 20 unless they are ready to go in on suspension components as well.
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Old 09-15-2014, 06:42 PM   #48
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Lots of good discussion above. Couple of items:

Bushing are all stock
Z/28 Caliper and pads are about 1kg more than CTSV caliper and pads primarily due to the pads
V rotor is 12kg
Z/28 rotor is in the 5kg range.

I am also not convinced the RS3 tire is any better than a hot Goodyear Supercar G2

Thanks, Matt
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Old 09-15-2014, 10:23 PM   #49
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Matt I know you like to push your car but how do you think these wheels would effect performance in an AutoX setting? I have a way to go before my car sees track days. I'm looking to get these wheels when they become available and am running the Pedders Super Car CO as well. I do mostly AutoX and street driving for now but intend to track the car once it's properly built. I scrapped my Cipher harness bar after trying it on a couple events. Comments you had made kept running through my mind so I'd value your input on these wheels in the setting I'd use them the most. Thx.
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Old 09-16-2014, 02:32 PM   #50
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Matt I know you like to push your car but how do you think these wheels would effect performance in an AutoX setting? I have a way to go before my car sees track days. I'm looking to get these wheels when they become available and am running the Pedders Super Car CO as well. I do mostly AutoX and street driving for now but intend to track the car once it's properly built. I scrapped my Cipher harness bar after trying it on a couple events. Comments you had made kept running through my mind so I'd value your input on these wheels in the setting I'd use them the most. Thx.
I can't answer your question in regards to Auto-crossing the car on them as I have no experience doing so. For reference the last car I autocrossed was a 1998 Integra Type R that was 2400ish lbs on a 205 tire in about 1999.

-Matt
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Old 09-17-2014, 02:40 PM   #51
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Matt, how much room do you have left on the inside of the rear wheels? That is, if I wanted to have wheels made and wanted to go in further, how much room is there, if any?

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Old 09-17-2014, 02:45 PM   #52
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How much room do you have left on the inside of the rear wheels? That is, if I wanted to have wheels made and wanted to go in further, how much room is there, if any?
Take a look at the wheel offsets. The wheels are pushed out even further than the amount they widened. Judging from offsets, the front room should be about same, while the rear should have even more room than what 1LE tires have.
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Old 09-17-2014, 04:03 PM   #53
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Front comparison. Z/28 is plotted in red.




Rear Comparison. Same plot convention.





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Old 10-13-2014, 05:42 PM   #54
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Quote:
Originally Posted by Dropspeed View Post
Lots of good discussion above. Couple of items:

Bushing are all stock
Z/28 Caliper and pads are about 1kg more than CTSV caliper and pads primarily due to the pads
V rotor is 12kg
Z/28 rotor is in the 5kg range.

I am also not convinced the RS3 tire is any better than a hot Goodyear Supercar G2

Thanks, Matt
Is that the ring, or does it include the hub, too? I remember seeing discard weights around 4600 grams, etc., so I would imagine 5kg does not include hub.
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Old 12-15-2014, 10:02 AM   #55
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I have no experience tracking a 1LE (saving up for mine currently) but I want to add that pushing the wheels father out will change the wheel rate, essentially adding a longer lever to push the spring making it feel softer. Anyone who knows the stock motion ratios and spring rates of the Pedders springs can calculate the difference with the new wheels.

Matt,

Before you go changing out your springs again, I am curious if just a larger front and rear sway bar will help with the transitions and feel with the wider wheels.
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Old 12-15-2014, 10:58 AM   #56
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I have no experience tracking a 1LE (saving up for mine currently) but I want to add that pushing the wheels father out will change the wheel rate, essentially adding a longer lever to push the spring making it feel softer. Anyone who knows the stock motion ratios and spring rates of the Pedders springs can calculate the difference with the new wheels.
Fortunately, the motion ratio consequence of changing the wheel offset is small. Hint: it involves the FVIC, not where the links making up the "LCA" physically attach to the chassis.


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