C5: Street Touring Unlimited (STU) Build Thread
09-21-2014, 10:28 PM
#21
Drifting
FYI, I'm going to try and get a letter into the SEB tomorrow about the intake. If you are thinking of doing a Vararam, please write in to ensure the issue gets addressed. I know people have legally run the Vararam in ASP now SSP and reading the SP rules, I see nothing different from the ST rules. There are no allowances for additional openings in bumpers/fascias and the only allowance I see is for fog light removals, which are also allowed in ST. I think there is a case to be made either way so we need an official clarification.
09-21-2014, 10:34 PM
#22
Safety Car
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.
09-21-2014, 10:49 PM
#23
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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 Z51 526/634
* 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 Z51 526/634
* 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
Interesting to see the Z51 and Z06 have the same front spring.
Aren't the VBP rates based on their own method of testing? Would be helpful if they compared their springs to the above stock springs, so we could compare them better.
Will the C6 springs work on a C5?
09-21-2014, 11:02 PM
#24
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FYI, I'm going to try and get a letter into the SEB tomorrow about the intake. If you are thinking of doing a Vararam, please write in to ensure the issue gets addressed. I know people have legally run the Vararam in ASP now SSP and reading the SP rules, I see nothing different from the ST rules. There are no allowances for additional openings in bumpers/fascias and the only allowance I see is for fog light removals, which are also allowed in ST. I think there is a case to be made either way so we need an official clarification.
09-21-2014, 11:04 PM
#25
Drifting
Adding C5 Z51 to the spring list: 525/634.
Interesting to see the Z51 and Z06 have the same front spring.
Aren't the VBP rates based on their own method of testing? Would be helpful if they compared their springs to the above stock springs, so we could compare them better.
Will the C6 springs work on a C5?
Interesting to see the Z51 and Z06 have the same front spring.
Aren't the VBP rates based on their own method of testing? Would be helpful if they compared their springs to the above stock springs, so we could compare them better.
Will the C6 springs work on a C5?
The C5 Z51 and C5Z are very similar suspension wise. Same front spring, same rear bar. In autocross trim, the only difference is the rear spring.
I've heard that about VB&P but don't know for sure.
I think C6 springs are interchangeable with the C5.
09-22-2014, 08:49 AM
#26
Racer
Thanks for the extra info.
The C5 Z51 and C5Z are very similar suspension wise. Same front spring, same rear bar. In autocross trim, the only difference is the rear spring.
I've heard that about VB&P but don't know for sure.
I think C6 springs are interchangeable with the C5.
The C5 Z51 and C5Z are very similar suspension wise. Same front spring, same rear bar. In autocross trim, the only difference is the rear spring.
I've heard that about VB&P but don't know for sure.
I think C6 springs are interchangeable with the C5.
I'll see if I saved the sources for this info, but from my research when doing a year-correct Z51 conversion:
FE3 (Z51) vs FE4 (Z06)
edit again: corrected swaybar information
'00+ FE3 front spring and front bar are the same PN as '01-'04 FE4 front spring and front bar.
The '00+ rear bar is the same or very similar the '01-'04 Z06 rear bar.
The '01-'04 FE4 rear spring is slightly stiffer than the '00+ rear spring.
edit: Found where a copied/ pasted the source info:
Front Springs
Part Number Casting Num Code Rate Years Suspension Useage
22178728 440# 97-02 FE1 w/o F45 All bodies with soft ride susp FE1,(EXC Chasis Realtime Damping F45)
22178729 22171750 AY 525# 98-00 FE3/Z51, FE4/Z06 All bodies with sport suspension Z51/FE3 and Z06 suspension FE4
22178748 457# 99-02 FE1 with F45 Y07-67 Soft ride suspension FE1, Chasis realtime damping F45
12480063 22188479A 582# 97-02 T1 New New style T1 front spring
22188479 582# 97-02 T1 Old Old style T1 front spring
Rear Springs
Part Number Casting Num Code Rate Years Suspension Useage
22179019 577# 98-03 FE1 with MM6 All bodies with 6 speed MM6 and Soft ride suspension FE1
22179020 22171757 RJF 634# 98-00 FE3/Z51 with MM6 All bodies with 6 speed MM6 and Sport suspension Z51/FE3
22146323 588# 98-03 FE1 with M30 All bodies with 4-spd auto trans M30 and Soft ride suspension FE1
22146646 645# 98-03 FE3/F51 with M30 All bodies with 4-spd auto trans M30 and Sport suspension Z51/FE3
22188038 22188078 RJH 714# 01-03 FE4/Z06 with M12 Z06 Hardtop with 6 speed M12 and FE4 Suspension
12480064 22188480 794# 97-02 T1 T1 Rear Spring
Part Number Casting Num Code Rate Years Suspension Useage
22178728 440# 97-02 FE1 w/o F45 All bodies with soft ride susp FE1,(EXC Chasis Realtime Damping F45)
22178729 22171750 AY 525# 98-00 FE3/Z51, FE4/Z06 All bodies with sport suspension Z51/FE3 and Z06 suspension FE4
22178748 457# 99-02 FE1 with F45 Y07-67 Soft ride suspension FE1, Chasis realtime damping F45
12480063 22188479A 582# 97-02 T1 New New style T1 front spring
22188479 582# 97-02 T1 Old Old style T1 front spring
Rear Springs
Part Number Casting Num Code Rate Years Suspension Useage
22179019 577# 98-03 FE1 with MM6 All bodies with 6 speed MM6 and Soft ride suspension FE1
22179020 22171757 RJF 634# 98-00 FE3/Z51 with MM6 All bodies with 6 speed MM6 and Sport suspension Z51/FE3
22146323 588# 98-03 FE1 with M30 All bodies with 4-spd auto trans M30 and Soft ride suspension FE1
22146646 645# 98-03 FE3/F51 with M30 All bodies with 4-spd auto trans M30 and Sport suspension Z51/FE3
22188038 22188078 RJH 714# 01-03 FE4/Z06 with M12 Z06 Hardtop with 6 speed M12 and FE4 Suspension
12480064 22188480 794# 97-02 T1 T1 Rear Spring
Last edited by hklvette; 09-22-2014 at 09:56 AM. Reason: found info
09-22-2014, 08:55 AM
#27
Drifting
Front C6 spring is interchangeable, but obviously the rates are different.
I'll see if I saved the sources for this info, but from my research when doing a year-correct Z51 conversion:
FE3 (Z51) vs FE4 (Z06)
'00+ FE3 front spring and front bar are the same PN as '01-'04 FE4 front spring and front bar.
The '00+ FE3 rear bar is bigger (if only slightly) than the '01-'03 rear bar.
The '01-'04 FE4 rear spring is slightly stiffer than the '00+ rear spring.
In '04 only, the Z06's received the stiffer FE3 rear bar and as a result they have the "stiffest" factory C5 suspension.
I'll see if I saved the sources for this info, but from my research when doing a year-correct Z51 conversion:
FE3 (Z51) vs FE4 (Z06)
'00+ FE3 front spring and front bar are the same PN as '01-'04 FE4 front spring and front bar.
The '00+ FE3 rear bar is bigger (if only slightly) than the '01-'03 rear bar.
The '01-'04 FE4 rear spring is slightly stiffer than the '00+ rear spring.
In '04 only, the Z06's received the stiffer FE3 rear bar and as a result they have the "stiffest" factory C5 suspension.
That is why some people hold that the 2000 FRC is the car to have for BS since it has the stiffest rear bar available for any of the non-Z06's.
09-22-2014, 09:53 AM
#28
Racer
See here:
https://www.corvetteforum.com/forums...s-97-04-a.html
I had thought I saw where the Z06s have a softer rear bar except '04. It looks like I was mistaken.
09-22-2014, 11:00 AM
#29
Instructor
Add me to the list for STU builds. I picked up a 99 FRC about a month ago, I will be doing the build in stages, looking to go to Nationals next year with the car in full prep. First stage is basically putting an SSR C5 Z06 suspension on the car + rear Z06 wheels all around, which is nearly complete. I'll run that at the North Carolina AutoX Championships in 2 weeks, then I'll start getting further into STU prep over the winter.
I don't have foglights on my FRC so I didn't see any issues in the rules with putting a Vararam on my car. Worst case, you just cut away most of the cover over where the vararam intake is- then you aren't removing anything, and you aren't altering anything post filter.
I don't have foglights on my FRC so I didn't see any issues in the rules with putting a Vararam on my car. Worst case, you just cut away most of the cover over where the vararam intake is- then you aren't removing anything, and you aren't altering anything post filter.
09-22-2014, 11:45 AM
#30
Instructor
As far as my full prep STU strategy, I am aiming for the lightest possible weight with a suspension setup that makes the car easy to drive and puts down power well. I'm no Lane Borg so going with a bit softer suspension so I can feel the car working, and being able to get the throttle opened up very early in the corner are my goals. The FRC I found is a zero-option car, so manual HVAC, no HUD, no fogs, no extra controls for the seats, no Bose stereo, etc, so hopefully 2950 lbs or even less is doable.
The other thing I would like to work on is getting the suspension to work at a lower ride height than typical for C5s, since ride height is open and CoG has such a large influence on grip. I have some ideas for more shock travel in bump (probably $$$), and will be upping the spring rates just as much as I need to stay off the bump stops. Some more progressive bump stops might also be helpful there so the car isn't slamming off them and losing traction if you do get into that region of travel.
The other thing I would like to work on is getting the suspension to work at a lower ride height than typical for C5s, since ride height is open and CoG has such a large influence on grip. I have some ideas for more shock travel in bump (probably $$$), and will be upping the spring rates just as much as I need to stay off the bump stops. Some more progressive bump stops might also be helpful there so the car isn't slamming off them and losing traction if you do get into that region of travel.
09-22-2014, 12:28 PM
#31
Drifting
My guess is the car will be super loose. I ran that setup on my A-Stock/B-Street car and the B-Street setup got pretty loose. Adding 285s all around is only going to make it worse. Might want to think of a stiffer front bar or stiffer front spring.
09-22-2014, 12:39 PM
#32
Racer
I didn't have a problem with oversteer while using a C6 Z51 front bar and 265 AD08s. I never picked up the C5 FE3/4 bar so I couldn't tell you if it would've been an issue with that.
09-22-2014, 01:13 PM
#33
Instructor
Stiffer front spring is next on the list for suspension after the NCAC. I was just reading another thread on here about VB&P springs and someone else did confirm that they test their springs differently than GM, so their rates are effectively meaningless. I really wish they would test a stock spring and post at least the % difference in rate for their sport and extreme springs.
09-22-2014, 03:13 PM
#35
Advanced
I guess I'll jump in. I am by no means a nationals level autocrosser but I do a lot of local events and like to know I'm not bringing a knife to a gun fight.
About 3 years ago I went from a STU STi to a 02 Z06 for SS. I hated trailering r-comps for local events
sorry. And mostly i hated not being able to tinker with the car.
So this year I ditched the Z06 and found a 99 FRC in white, no hud, no auto climate etc.
Set up so far:
Strano front bar and Strano recommended front spring.
Seat - Corbeau evolution X
Short shifter
Blackwing intake - found cheap on forum
ccw wheels (because i always wanted a set and there was a good price diff between the Z and FRC) 18x10.5 with 285 rs3. v1 cause all the v2 were gone.
Wheels were made with the old SS backspace allowance so i can remove spacer front or rear to help with balance/narrow track etc.
Any recommendations on leaving the spacers in or taking them out?
Stock rear bar which on the 99-00 is 21mm i believe
shocks - koni yellows - carry over from z06
alignment - 3 deg camber upfront with a little toe out
1.5 deg camber rear with a little toe in
Still have some money left over for headers and a tune, but waiting to see if the car needs more front spring or a bigger rear bar like the 24mm from the z06. Or maybe susp bushings.
I will say coming from an STi where stiffer was just about always better it's difficult for me to believe a c5 with just a front spring and bar can be competitive. Basically our cars will wind up being a c5 Z06 with a little bit more front spring and more front tire. Is that enough to make up the 1.5-2 seconds on a 60s course that STU is faster than BS?
About 3 years ago I went from a STU STi to a 02 Z06 for SS. I hated trailering r-comps for local events
sorry. And mostly i hated not being able to tinker with the car.So this year I ditched the Z06 and found a 99 FRC in white, no hud, no auto climate etc.
Set up so far:
Strano front bar and Strano recommended front spring.
Seat - Corbeau evolution X
Short shifter
Blackwing intake - found cheap on forum
ccw wheels (because i always wanted a set and there was a good price diff between the Z and FRC) 18x10.5 with 285 rs3. v1 cause all the v2 were gone.
Wheels were made with the old SS backspace allowance so i can remove spacer front or rear to help with balance/narrow track etc.
Any recommendations on leaving the spacers in or taking them out?
Stock rear bar which on the 99-00 is 21mm i believe
shocks - koni yellows - carry over from z06
alignment - 3 deg camber upfront with a little toe out
1.5 deg camber rear with a little toe in
Still have some money left over for headers and a tune, but waiting to see if the car needs more front spring or a bigger rear bar like the 24mm from the z06. Or maybe susp bushings.
I will say coming from an STi where stiffer was just about always better it's difficult for me to believe a c5 with just a front spring and bar can be competitive. Basically our cars will wind up being a c5 Z06 with a little bit more front spring and more front tire. Is that enough to make up the 1.5-2 seconds on a 60s course that STU is faster than BS?
09-23-2014, 03:02 PM
#36
Supporting Vendor
Well this talk it making me think that my plan to pick up an FRC and to work with Lane is probably a good one. 
But I know I'm not likely to be one using huge front springs and massive rear bars. BTW we do have a pretty simple adjustable rear sway bar for the C5 in various sizes, much like the front bars.
And yes there have been some front bar issues due to a new bender and new people running it (and not getting some important details, but that's all worked out now).
But I know I'm not likely to be one using huge front springs and massive rear bars.
BTW we do have a pretty simple adjustable rear sway bar for the C5 in various sizes, much like the front bars. And yes there have been some front bar issues due to a new bender and new people running it (and not getting some important details, but that's all worked out now).
09-25-2014, 12:16 AM
#38
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Wheels arrived yesterday, 18x11 Forgestar F14's, gunmetal.
Shocks will be on their way soon. Some questions on mounting canisters. Where are you guys mounting canisters? What are you using to mount them? Any pics are most welcome. I really struggled with my Penske 8300's on my S2000, spent many hours trying to find a good place for them, and mount them properly (ie. no zip ties).
Next shock mounting question. Access to the rear rebound adjuster will need a hole cut into the carpet. Tips for best way to cut the hole? Anyone find a nice plug to cover the holes when not in use?
Jeff
Shocks will be on their way soon. Some questions on mounting canisters. Where are you guys mounting canisters? What are you using to mount them? Any pics are most welcome. I really struggled with my Penske 8300's on my S2000, spent many hours trying to find a good place for them, and mount them properly (ie. no zip ties).
Next shock mounting question. Access to the rear rebound adjuster will need a hole cut into the carpet. Tips for best way to cut the hole? Anyone find a nice plug to cover the holes when not in use?
Jeff
09-25-2014, 08:03 AM
#39
Drifting
Wheels arrived yesterday, 18x11 Forgestar F14's, gunmetal.
Shocks will be on their way soon. Some questions on mounting canisters. Where are you guys mounting canisters? What are you using to mount them? Any pics are most welcome. I really struggled with my Penske 8300's on my S2000, spent many hours trying to find a good place for them, and mount them properly (ie. no zip ties).
Next shock mounting question. Access to the rear rebound adjuster will need a hole cut into the carpet. Tips for best way to cut the hole? Anyone find a nice plug to cover the holes when not in use?
Jeff
Shocks will be on their way soon. Some questions on mounting canisters. Where are you guys mounting canisters? What are you using to mount them? Any pics are most welcome. I really struggled with my Penske 8300's on my S2000, spent many hours trying to find a good place for them, and mount them properly (ie. no zip ties).
Next shock mounting question. Access to the rear rebound adjuster will need a hole cut into the carpet. Tips for best way to cut the hole? Anyone find a nice plug to cover the holes when not in use?
Jeff
Look on McMaster for insulated band clamps in the right diameter for the canister.
09-25-2014, 08:04 AM
#40
Drifting