C5: Street Touring Unlimited (STU) Build Thread
11-05-2014, 04:04 PM
#121
Supporting Vendor
A little taste of the bushings. More info next week or so, after I pound these around some on the PA roads and a couple of track days. 
https://www.youtube.com/watch?v=3Fe1...ature=youtu.be
https://www.youtube.com/watch?v=3Fe1...ature=youtu.be
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Sam Strano
Strano Performance Parts
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More options than any other single company out there. More parts than any other single company I know: Brakes to Safety, Wheels to Exhaust. Suspension to Air Filters: Girodisc, Hawk, Raybestos, Essex Racing/AP, Ferodo, Wilwood, Penske, Koni, Borg Motorsport, Ridetech, Viking, After Dark Speed, Hotchkis, Bilstein, KW, Forgestar, BC Forged, Forgeline, MRR Wheels and on, and on, and on it goes.
Sam Strano
Strano Performance Parts
www.stranoparts.com
814-849-3450
More options than any other single company out there. More parts than any other single company I know: Brakes to Safety, Wheels to Exhaust. Suspension to Air Filters: Girodisc, Hawk, Raybestos, Essex Racing/AP, Ferodo, Wilwood, Penske, Koni, Borg Motorsport, Ridetech, Viking, After Dark Speed, Hotchkis, Bilstein, KW, Forgestar, BC Forged, Forgeline, MRR Wheels and on, and on, and on it goes.
11-05-2014, 04:07 PM
#122
Drifting
As for the air tubes. There are headers with air fittings on them, so no change is necessary there. ST rules do not allow update/backdate or removal of emissions, at least the way I read the rules. I'm sure someone will read something different. You can change EGR tubes, but Air tubes are not EGR, so I think you have to run them.
As for X-Pipe, it can be before the cats if you want. As Sam said, the cats just have to be in the right place when complete. From what I can tell, it looks like with how long the LG headers are, you'd have to do headers-cat-xpipe. With something like ARH, it looks like you could do headers-xpipe-cats and be fine. I have NOT measured either of these systems to know for sure, just going on the pictures of installed parts.
11-06-2014, 03:22 PM
#124
Racer
Not even VB&P are triple the rate. We are limited in our choices. Basically there is VB&P and Hypercoil (plus other stock GM springs). Here's the list from a thread on here:
Springs:
* C5 Z06: 526# Front, 714# Rear
* C6 Z06: 531# Front, 782# Rear
* C6 Z51: 526# Front, 645# Rear
* T1 (C6): 582# Front, 850# Rear
* C6 Base: 420# Front, 657# Rear (VBP: 400-420 F / 600-620 R)
* T1 (C5): 582# Front, 793# Rear
* Pfadt Coil-overs: 425# Front, 575# Rear (Remember: Wheel rates!)
* Hyperco HPS (Street): 565# Front (12405HPS), #765 Rear (12406HPS)
* Hyperco HPT (Track/Solo): 625# Front (12407HPT), #850 Rear (12408HPT)
* VBP Sport 990# Front, 650# Rear
* VBP Extreme 1050# Front, 855# Rear
Springs:
* C5 Z06: 526# Front, 714# Rear
* C6 Z06: 531# Front, 782# Rear
* C6 Z51: 526# Front, 645# Rear
* T1 (C6): 582# Front, 850# Rear
* C6 Base: 420# Front, 657# Rear (VBP: 400-420 F / 600-620 R)
* T1 (C5): 582# Front, 793# Rear
* Pfadt Coil-overs: 425# Front, 575# Rear (Remember: Wheel rates!)
* Hyperco HPS (Street): 565# Front (12405HPS), #765 Rear (12406HPS)
* Hyperco HPT (Track/Solo): 625# Front (12407HPT), #850 Rear (12408HPT)
* VBP Sport 990# Front, 650# Rear
* VBP Extreme 1050# Front, 855# Rear
From personal experience, the VBP 1130 is not nearly double the rate of a C5 Z06 front spring... I'd estimate that it is less than 50% stiffer. I've tried a 900 and it wasn't a big enough difference from stock.
For my STU setup, I've run 285/30-18 Dunlop ZIIs on C5 Z06 rear wheels, square. They don't seem to be as great on concrete as the RS3s. I'd like to try the RS3s next year... also will be upgrading shocks next year. I wanted to get spring rates and sway bars nailed down first and now they are.
11-06-2014, 03:27 PM
#125
Instructor
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I have some experience with VBP springs. I'm the previous owner of HKLVette's 1130 lb/in front. The most important thing to consider is that they use a different measurement method than what was used for GM parts. I spoke to a technical expert at VBP, Gary I believe, and he informed me that these springs are simply clamped in the middle and both ends are deflected to measure the rates. For our purposes the numbers mean nothing. The numbers can only be used on the basis of relativity. Good luck calculating a wheel rate.
From personal experience, the VBP 1130 is not nearly double the rate of a C5 Z06 front spring... I'd estimate that it is less than 50% stiffer. I've tried a 900 and it wasn't a big enough difference from stock.
For my STU setup, I've run 285/30-18 Dunlop ZIIs on C5 Z06 rear wheels, square. They don't seem to be as great on concrete as the RS3s. I'd like to try the RS3s next year... also will be upgrading shocks next year. I wanted to get spring rates and sway bars nailed down first and now they are.
From personal experience, the VBP 1130 is not nearly double the rate of a C5 Z06 front spring... I'd estimate that it is less than 50% stiffer. I've tried a 900 and it wasn't a big enough difference from stock.
For my STU setup, I've run 285/30-18 Dunlop ZIIs on C5 Z06 rear wheels, square. They don't seem to be as great on concrete as the RS3s. I'd like to try the RS3s next year... also will be upgrading shocks next year. I wanted to get spring rates and sway bars nailed down first and now they are.
11-06-2014, 03:30 PM
#126
Supporting Vendor
Meanwhile the C5 and C6's I've driven in SSP trim on the BIG spring I fine way, way too stiff, on big old Hoosiers. No way will my car get anything like that, then again I've won Championships in cars with 1/2-1/3rd the spring rate of others in the same chassis cars (which also weighed less due to pulling A/C and the like) in ESP so I've been one to go big on springs. And that is even more the case with street tires which make less grip than R's anyway.
11-20-2014, 03:52 PM
#129
Racer
Lane, what are you doing????
J/K! Congratulations on the STAC seat 
Street Touring
#14843, 14926, 15026, 15070 STAC Resumes
The SEB has approved the addition of Robert Irish, Bart Hockerman, Matthew Leach, and Lane Borg to the STAC.
#14843, 14926, 15026, 15070 STAC Resumes
The SEB has approved the addition of Robert Irish, Bart Hockerman, Matthew Leach, and Lane Borg to the STAC.
11-20-2014, 04:03 PM
#130
Racer
Sam, I like the bigger front spring because it reduces lift & dive under throttle and braking respectively. It has also helped reduce front locking since the front can get settled quicker than before. I don't think it has affected maximum grip, but I don't have a data logger to confirm that.
11-20-2014, 05:43 PM
#132
Supporting Vendor
I agree with this. I'm curious if it ends up being the equivalent to the Hypercoil "HPT" leaf, with a different rate curve due to the different shape.
Sam, I like the bigger front spring because it reduces lift & dive under throttle and braking respectively. It has also helped reduce front locking since the front can get settled quicker than before. I don't think it has affected maximum grip, but I don't have a data logger to confirm that.
Sam, I like the bigger front spring because it reduces lift & dive under throttle and braking respectively. It has also helped reduce front locking since the front can get settled quicker than before. I don't think it has affected maximum grip, but I don't have a data logger to confirm that.
11-24-2014, 10:53 AM
#133
Racer
How stiff is it really vs a GM spring, who really knows... but it's stiff. Yeah, if you hate roll and dive at all it's great. All I can tell you is that without fail even on A6's the cars I've driven are just tight with that big spring on them. The "880" spring seems to be ok and from what I can tell more similar to the HPT Hyperco. Whether it's been on C5 or C6 (or even with their stiffest C4 springs on those in the day) the big front springs from them just make the car a skateboard. Some may like that, I'm not one. I'd rather have some compliance and get more front roll control from a bar.
I had:
'00+ Z51 leaves F&R
C6 Z51 front bar
'00+ Z51 rear bar
When I put in the VB&P leaf, I changed the front bar out for the C5 FE1 piece. Not having a data logger makes analysis difficult, but it feels like roll stiffness is similar to what I had before, and the cornering balance has moved slightly towards oversteer at all speeds.
If I had left the bigger front bar in, I'm sure that I would've seen a significant shift towards understeer.
11-24-2014, 01:12 PM
#134
Heel & Toe
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No. A shorter wheelbase WILL change direction faster. At higher speeds where smaller inputs result in bigger changes in lateral g, shorter wheelbase cars get harder to drive because they rotate so much faster than a longer wheelbase. OEMs don't go to autocross to prove their cars and set records, they go to tracks, where a longer wheelbase creates more stability. There's a big difference between building a track car and an autocross car. This is why the BM tend to be older DSR cars (shorter wheelbase) but current DSR cars are much faster on a track than the old ones.
All things being equal, I'd rather have a C4 sized car than a C5 sized car to autocross because a shorter wheelbase is helpful on small, tight autocross courses and the C4's denser packaging of the large masses makes it more progressive in rotation than the C5. That said, the C5 has superior rear suspension design, a much stiffer chassis, a better engine, etc. so all things are NOT equal. With the C5's high inertia, it is harder to get the car to rotate as well as harder to stop the rotation. Once you get it rotating, you have a lot more mass to stop than in a more traditional layout. Think of all the oversteer issues Porsche has had to design around because of the huge amount of mass at the back of the car. This is why the early 911's developed their reputation for sudden and stronger oversteer. It's the same thing in the modern Vettes, just on a less dramatic scale. Hopefully that clears things up.
Also remember, as mentioned above, all things aren't equal in the C4 vs C5 case. The inertia issues come into play when you can design a car from scratch. The Cayman was faster than the 911 for this reason (until Porsche retuned it to keep the 911 on top). Given we can't get into moving things around in STU, I'll just take the benefit of a nearly 50/50 weight distribution and deal with so,e extra inertia in driving style.
All things being equal, I'd rather have a C4 sized car than a C5 sized car to autocross because a shorter wheelbase is helpful on small, tight autocross courses and the C4's denser packaging of the large masses makes it more progressive in rotation than the C5. That said, the C5 has superior rear suspension design, a much stiffer chassis, a better engine, etc. so all things are NOT equal. With the C5's high inertia, it is harder to get the car to rotate as well as harder to stop the rotation. Once you get it rotating, you have a lot more mass to stop than in a more traditional layout. Think of all the oversteer issues Porsche has had to design around because of the huge amount of mass at the back of the car. This is why the early 911's developed their reputation for sudden and stronger oversteer. It's the same thing in the modern Vettes, just on a less dramatic scale. Hopefully that clears things up.
Also remember, as mentioned above, all things aren't equal in the C4 vs C5 case. The inertia issues come into play when you can design a car from scratch. The Cayman was faster than the 911 for this reason (until Porsche retuned it to keep the 911 on top). Given we can't get into moving things around in STU, I'll just take the benefit of a nearly 50/50 weight distribution and deal with so,e extra inertia in driving style.
Not wanting to off-topic this thread more than the conventions of this forum tolerate, I'm giving some serious thought to picking up a C4 toward spring for a local/regional level STU build -- not looking to compete at the nationals with it. I had a very good STS Neon about 6 years ago, and I think this might be a fun way to get back into AutoX and maybe a few track days here and there.
At any rate, is this an appropriate additional discussion topic for this thread, or should I start another one specifically for C4 content?
Thanks in advance!
11-24-2014, 01:30 PM
#135
Melting Slicks
Hello all!
Not wanting to off-topic this thread more than the conventions of this forum tolerate, I'm giving some serious thought to picking up a C4 toward spring for a local/regional level STU build -- not looking to compete at the nationals with it. I had a very good STS Neon about 6 years ago, and I think this might be a fun way to get back into AutoX and maybe a few track days here and there.
At any rate, is this an appropriate additional discussion topic for this thread, or should I start another one specifically for C4 content?
Thanks in advance!
Not wanting to off-topic this thread more than the conventions of this forum tolerate, I'm giving some serious thought to picking up a C4 toward spring for a local/regional level STU build -- not looking to compete at the nationals with it. I had a very good STS Neon about 6 years ago, and I think this might be a fun way to get back into AutoX and maybe a few track days here and there.
At any rate, is this an appropriate additional discussion topic for this thread, or should I start another one specifically for C4 content?
Thanks in advance!
Last edited by 69autoXr; 11-24-2014 at 01:39 PM.
11-24-2014, 01:41 PM
#136
Heel & Toe
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Oh wow! I did see that it wasn't listed there, but since it wasn't listed in any of the other ST classes that I saw, I just assumed it would be allowed as a slower prior model in STU... There I go with assuming again! Lol
11-24-2014, 03:45 PM
#138
Supporting Vendor
I'm curious, on the cars that you drive with big front leaves was the front bar changed to compensate? Using my setup as an example:
I had:
'00+ Z51 leaves F&R
C6 Z51 front bar
'00+ Z51 rear bar
When I put in the VB&P leaf, I changed the front bar out for the C5 FE1 piece. Not having a data logger makes analysis difficult, but it feels like roll stiffness is similar to what I had before, and the cornering balance has moved slightly towards oversteer at all speeds.
If I had left the bigger front bar in, I'm sure that I would've seen a significant shift towards understeer.
I had:
'00+ Z51 leaves F&R
C6 Z51 front bar
'00+ Z51 rear bar
When I put in the VB&P leaf, I changed the front bar out for the C5 FE1 piece. Not having a data logger makes analysis difficult, but it feels like roll stiffness is similar to what I had before, and the cornering balance has moved slightly towards oversteer at all speeds.
If I had left the bigger front bar in, I'm sure that I would've seen a significant shift towards understeer.
And I'm not married to monster front bars either. In fact one thing I tried early last year on my Grand Sport with mega-dollar shocks was a stock front bar and a smaller rear. didn't work.
12-03-2014, 11:31 PM
#139
Racer
Like Mr. Strano has mentioned, he's had success with simply different setups than others. One may not be better than another. Two completely different setups may get close to one another in terms of overall capability. But, choose what suits your driving style.
I've chased my tail a bit with spring rates. I don't like stock Corvette feel, whether we're talking about my C5 or a brand new C7, where the rear ride rate is higher than the front. To be honest, even with my C5 not totally optimized, I enjoyed the handling feel over a C7 (FE1) that I happened to have from work for a weekend. Stiffer rear just doesn't feel right to me. And a lot of the reason behind GM doing this is ride quality. A higher rear ride rate and more importantly, ride frequency, is desired to make a car feel good to the masses when going over a bump. For hardcore cars like the Z/28 for example, GM will tell you that it is not meant to be daily driven on the street, and the basics to what they did to the suspension was set it up square in terms of wheels and tires, jack the spring rates up (especially in the front than rear), and actually downsize swaybars (especially in the rear).
The Z/28 is obviously set up beautifully for the track. Very little dive under braking, puts power down effectively on exit. But I only told a small part of GM's development of the Z/28 chassis and I'm sure I don't know the half of it. An important thing to remember, and what Strano has mentioned multiple times, is how important damping is. And someone playing with spring rates and sway bars without having any educated **** turning going on in terms of damping is dangerous.
Anyway, with my car, I did prefer the stiffer front spring rate. However, from the 1130, I downsized because I didn't like that I had a hard time shifting weight to point the nose when I wanted. I'm still searching for that 3 bears, just right, balance.
My spring rate and sway bar balance is what I'd call pretty good at this point, personally. What I would really like to play with is damping and just drive sets of tires. I am starting with DRM revalved Bilsteins and going from there. May have a 3rd party revalve down the road. I don't have much experience with tuning dampers though. I'd love a set of double adjustables to play with... But, playing with $400 easily resaleable dampers for now.
I've chased my tail a bit with spring rates. I don't like stock Corvette feel, whether we're talking about my C5 or a brand new C7, where the rear ride rate is higher than the front. To be honest, even with my C5 not totally optimized, I enjoyed the handling feel over a C7 (FE1) that I happened to have from work for a weekend. Stiffer rear just doesn't feel right to me. And a lot of the reason behind GM doing this is ride quality. A higher rear ride rate and more importantly, ride frequency, is desired to make a car feel good to the masses when going over a bump. For hardcore cars like the Z/28 for example, GM will tell you that it is not meant to be daily driven on the street, and the basics to what they did to the suspension was set it up square in terms of wheels and tires, jack the spring rates up (especially in the front than rear), and actually downsize swaybars (especially in the rear).
The Z/28 is obviously set up beautifully for the track. Very little dive under braking, puts power down effectively on exit. But I only told a small part of GM's development of the Z/28 chassis and I'm sure I don't know the half of it. An important thing to remember, and what Strano has mentioned multiple times, is how important damping is. And someone playing with spring rates and sway bars without having any educated **** turning going on in terms of damping is dangerous.
Anyway, with my car, I did prefer the stiffer front spring rate. However, from the 1130, I downsized because I didn't like that I had a hard time shifting weight to point the nose when I wanted. I'm still searching for that 3 bears, just right, balance.
My spring rate and sway bar balance is what I'd call pretty good at this point, personally. What I would really like to play with is damping and just drive sets of tires. I am starting with DRM revalved Bilsteins and going from there. May have a 3rd party revalve down the road. I don't have much experience with tuning dampers though. I'd love a set of double adjustables to play with... But, playing with $400 easily resaleable dampers for now.
12-04-2014, 08:37 AM
#140
Drifting
Most people really like the stiff front/soft rear setup and that's why I recommend it to people who ask me what to do with spring rate. I'll get into more details in the build thread for my car I'm planning, but basically compared to a looser setup, that setup requires large steering wheel inputs, the car takes a set sooner (although on a larger radius), and is super stable. All of these things make the car less sensitive to bad inputs (whether through driving skill level or just making a small misjudgement in inputs). This makes the car easier to drive, but is not necessarily fast as the car is more balanced to understeer.