C5 spring rates - going HIGHER on front?
10-13-2011, 09:44 AM
#61
Safety Car
I'm glad my PTA/TTA car has to run stock springs/schocks so I don't have to think about all this engineering mumbo-jumbo.
A few years ago I was given this book as a gift... need to read it again...
A few years ago I was given this book as a gift... need to read it again...
10-13-2011, 09:51 AM
#62
Drifting
Travis,
Without giving this exhaustive thought, I would think of it “the other way” - that the shocks are angled to that degree in order to effectively damp the oscillation of the transverse leaf spring. That may have inspired GM to spec higher rates for the rear, but again, FOR THE STREET. Once we move to the track, all that reasoning becomes moot. Ed
Without giving this exhaustive thought, I would think of it “the other way” - that the shocks are angled to that degree in order to effectively damp the oscillation of the transverse leaf spring. That may have inspired GM to spec higher rates for the rear, but again, FOR THE STREET. Once we move to the track, all that reasoning becomes moot. Ed
Agree...for the track it doesn't matter.
10-13-2011, 02:02 PM
#63
Le Mans Master
10-13-2011, 03:07 PM
#64
Tech Contributor
I find it entertaining that they select one of the most evil-handling cars of all time as their "poster child" on that cover. I suppose the subliminal message is, "If you can set up one of these to stay on the track, you can set up anything."
Ed
Ed
10-13-2011, 09:20 PM
#65
10-13-2011, 09:59 PM
#66
Tech Contributor
Bob,
My understanding of it is this: Theoretically, the only time that anti-roll bars even come into play is in a turn. But wheel rate, by definition, is the STATIC stiffness of a particular corner of the car. Wheel rate is critical in a corner, absolutely, but also under straight-line braking, and under straight-line acceleration.
By definition, wheel rate on a particular corner of the car is (Motion Ratio squared) times Spring Rate, and both these measurements have to do with the SPRING only. Indeed, when we measure to determine an unknown motion ratio, we typically disconnect the damper, and occasionally the anti-roll bar, if we think they could interfere with accuracy.
We all know that heavier anti-roll bars contribute to the overall stiffness and control of the chassis. They just don't add to the (static) spring rate.
Hope this helps,
Ed
My understanding of it is this: Theoretically, the only time that anti-roll bars even come into play is in a turn. But wheel rate, by definition, is the STATIC stiffness of a particular corner of the car. Wheel rate is critical in a corner, absolutely, but also under straight-line braking, and under straight-line acceleration.
By definition, wheel rate on a particular corner of the car is (Motion Ratio squared) times Spring Rate, and both these measurements have to do with the SPRING only. Indeed, when we measure to determine an unknown motion ratio, we typically disconnect the damper, and occasionally the anti-roll bar, if we think they could interfere with accuracy.
We all know that heavier anti-roll bars contribute to the overall stiffness and control of the chassis. They just don't add to the (static) spring rate.
Hope this helps,
Ed
Last edited by RacePro Engineering; 10-14-2011 at 05:46 PM. Reason: Forgot the "squared"!
10-14-2011, 08:02 AM
#67
Drifting
Bob,
My understanding of it is this: Theoretically, the only time that anti-roll bars even come into play is in a turn. But wheel rate, by definition, is the STATIC stiffness of a particular corner of the car. Wheel rate is critical in a corner, absolutely, but also under straight-line braking, and under straight-line acceleration.
By definition, wheel rate on a particular corner of the car is Motion Ratio times Spring Rate, and both these measurements have to do with the SPRING only. Indeed, when we measure to determine an unknown motion ratio, we typically disconnect the damper, and occasionally the anti-roll bar, if we think they could interfere with accuracy.
We all know that heavier anti-roll bars contribute to the overall stiffness and control of the chassis. They just don't add to the (static) spring rate.
Hope this helps,
Ed
My understanding of it is this: Theoretically, the only time that anti-roll bars even come into play is in a turn. But wheel rate, by definition, is the STATIC stiffness of a particular corner of the car. Wheel rate is critical in a corner, absolutely, but also under straight-line braking, and under straight-line acceleration.
By definition, wheel rate on a particular corner of the car is Motion Ratio times Spring Rate, and both these measurements have to do with the SPRING only. Indeed, when we measure to determine an unknown motion ratio, we typically disconnect the damper, and occasionally the anti-roll bar, if we think they could interfere with accuracy.
We all know that heavier anti-roll bars contribute to the overall stiffness and control of the chassis. They just don't add to the (static) spring rate.
Hope this helps,
Ed
If you hit a bump and just one wheel goes up, the wheel rate is due to the spring and the bar.
The bar rate doesn't affect wheel rate if both ends of the bar move together in the same direction.
08-27-2012, 07:52 PM
#68
Race Director
Thread Starter
Update on this slightly old thread, I put the rear t1 bar in today & front later this week. T1 bars. rear set soft. Will realign & try for the last events of the season.
Did a video on rear bar, piece of cake.
Click below later tonight. Not up yet.
Did a video on rear bar, piece of cake.
Click below later tonight. Not up yet.
11-19-2012, 07:59 AM
#69
Sorry for digging up an old thread but I'm curious of the thought of putting a VBP sport front and C5 Z06 rear spring (990/714) with C5 Z06 sway bars (30/23.6) and C6 Z06 shocks?
11-19-2012, 01:52 PM
#70
Le Mans Master
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But now i just went to a larger sway bar setup, with Koni FSD's. The jury is still out on my new config. Should know after a few heats 
09-02-2014, 04:09 PM
#71
Racer
I don't mean to break forum rules by responding to a dead thread, but I had read through this when beginning to set my car up and had I known what I do now, I would have been much better off. So I wanted to share what I learned from the technical folks at VB&P and what it's meant for my car.
What I learned talking to Gary G. from VB&P is that these springs are not measured how you might expect. VB&P also makes and tests springs for older Corvettes and those springs only mount in the middle. They use the same test equipment for the C3 springs for example, as they do for C5, C6 springs. Therefore, for a C5 and C6, the measured rates do not reflect how the spring acts on the vehicle.
What I got from Gary is that the spring is clamped in the center and both ends are deflected at once. This also would explain the apparently high figures. It seems like the ideal front:rear ratio is about 1.33 from my testing with a square tire setup.
Just food for thought.
What I learned talking to Gary G. from VB&P is that these springs are not measured how you might expect. VB&P also makes and tests springs for older Corvettes and those springs only mount in the middle. They use the same test equipment for the C3 springs for example, as they do for C5, C6 springs. Therefore, for a C5 and C6, the measured rates do not reflect how the spring acts on the vehicle.
What I got from Gary is that the spring is clamped in the center and both ends are deflected at once. This also would explain the apparently high figures. It seems like the ideal front:rear ratio is about 1.33 from my testing with a square tire setup.
Just food for thought.
09-02-2014, 04:48 PM
#72
Instructor
Cool, thanks for posting that. Did he have any idea what their posted spring rates correspond to in terms of a stock C5Z spring? Trying to decide between T1, Hyperco and VB&P for my front spring so having comparable spring rates would be wonderful.
It's frustrating that the rates are listed differently, how hard would it be to clamp a stock C5 spring in their same rig and tell us the % difference?
It's frustrating that the rates are listed differently, how hard would it be to clamp a stock C5 spring in their same rig and tell us the % difference?
09-02-2014, 05:59 PM
#73
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FYI the KONI FSD Shocks are fricken' Phenomenal!
09-02-2014, 09:38 PM
#74
Racer
Cool, thanks for posting that. Did he have any idea what their posted spring rates correspond to in terms of a stock C5Z spring? Trying to decide between T1, Hyperco and VB&P for my front spring so having comparable spring rates would be wonderful.
It's frustrating that the rates are listed differently, how hard would it be to clamp a stock C5 spring in their same rig and tell us the % difference?
It's frustrating that the rates are listed differently, how hard would it be to clamp a stock C5 spring in their same rig and tell us the % difference?
I had a good setup that I purchased used which was 1120 lb/in front, 825 rear. I had some understeer (tight autocross) with Z51 front bar and T1 rear bar. So I went down to a 975 front and ruined my setup, admittedly. I couldn't keep the rear behind the car and lost (in STU) to a BS car at a solo event. I played with swaybars to dial it back into something balanced, but the car just isn't setup as well as before I ruined it.
I now am awaiting my new 1100 front spring from VB&P and excited to have my car dialed in with lessons learned. They can make about any rate you want. I've had some trouble with miscommunication regarding rates with them, but they've corrected it and have been good to deal with. They're even going to take my 975# spring back with a restocking fee.
I just wanted to share my findings with VB&P. They seem like quality products. Their rates don't mean much, however. So try not to compare to rates that the OP presented. The only thing we can really use is relativity. 1100/825 seems like a good front/rear setup for my 285 square Direzzas. Another competitive driver here earlier mentioned success with 1200/900. As another reference point, I've heard mention that Danny Popp runs rates higher than 1300 front and well over 900 rear with slicks and aero with great success.
I thought my setup of 1100 front would be overly stiff and this is not the case. It is stiffer than stock, but the setup is still reasonably compliant, and I prefer the car's behavior being more stiffly sprung in the front.
Stock cars, even the C7, doesn't feel right to me anymore with the soft front spring. I'm convinced the higher rear rate is 100% for ride quality. And the car is then balanced with sway bars. Front engine, rear drive racecars just don't have lower ride rates in the front than the rear. They just don't.
09-02-2014, 10:02 PM
#75
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I agree with you 100% but I did not get a solid answer on OEM rates when I asked. They merely gave me OEM replacement rates and said that the C5 front spring stock replacement ranges from 750-900 lb/in. Don't read into this too much and over-analyze like I did. We don't know what stock rates are.
I had a good setup that I purchased used which was 1120 lb/in front, 825 rear. I had some understeer (tight autocross) with Z51 front bar and T1 rear bar. So I went down to a 975 front and ruined my setup, admittedly. I couldn't keep the rear behind the car and lost (in STU) to a BS car at a solo event. I played with swaybars to dial it back into something balanced, but the car just isn't setup as well as before I ruined it.
I now am awaiting my new 1100 front spring from VB&P and excited to have my car dialed in with lessons learned. They can make about any rate you want. I've had some trouble with miscommunication regarding rates with them, but they've corrected it and have been good to deal with. They're even going to take my 975# spring back with a restocking fee.
I just wanted to share my findings with VB&P. They seem like quality products. Their rates don't mean much, however. So try not to compare to rates that the OP presented. The only thing we can really use is relativity. 1100/825 seems like a good front/rear setup for my 285 square Direzzas. Another competitive driver here earlier mentioned success with 1200/900. As another reference point, I've heard mention that Danny Popp runs rates higher than 1300 front and well over 900 rear with slicks and aero with great success.
I thought my setup of 1100 front would be overly stiff and this is not the case. It is stiffer than stock, but the setup is still reasonably compliant, and I prefer the car's behavior being more stiffly sprung in the front.
Stock cars, even the C7, doesn't feel right to me anymore with the soft front spring. I'm convinced the higher rear rate is 100% for ride quality. And the car is then balanced with sway bars. Front engine, rear drive racecars just don't have lower ride rates in the front than the rear. They just don't.
I had a good setup that I purchased used which was 1120 lb/in front, 825 rear. I had some understeer (tight autocross) with Z51 front bar and T1 rear bar. So I went down to a 975 front and ruined my setup, admittedly. I couldn't keep the rear behind the car and lost (in STU) to a BS car at a solo event. I played with swaybars to dial it back into something balanced, but the car just isn't setup as well as before I ruined it.
I now am awaiting my new 1100 front spring from VB&P and excited to have my car dialed in with lessons learned. They can make about any rate you want. I've had some trouble with miscommunication regarding rates with them, but they've corrected it and have been good to deal with. They're even going to take my 975# spring back with a restocking fee.
I just wanted to share my findings with VB&P. They seem like quality products. Their rates don't mean much, however. So try not to compare to rates that the OP presented. The only thing we can really use is relativity. 1100/825 seems like a good front/rear setup for my 285 square Direzzas. Another competitive driver here earlier mentioned success with 1200/900. As another reference point, I've heard mention that Danny Popp runs rates higher than 1300 front and well over 900 rear with slicks and aero with great success.
I thought my setup of 1100 front would be overly stiff and this is not the case. It is stiffer than stock, but the setup is still reasonably compliant, and I prefer the car's behavior being more stiffly sprung in the front.
Stock cars, even the C7, doesn't feel right to me anymore with the soft front spring. I'm convinced the higher rear rate is 100% for ride quality. And the car is then balanced with sway bars. Front engine, rear drive racecars just don't have lower ride rates in the front than the rear. They just don't.
Gotta sell cars! A lot depends lot on your tires . The main reasoning for lighter rear sway or no rear sway at all is to get the rear tires to stick. Only Vettes I have seen set up by Danny pop were for road racing. i would think you would want a lot stiffer suspension in autocross, but what the heck do i know? i never do autocross lol
10-22-2014, 03:25 PM
#77
Measure the motion ratio of the leaf spring attachment point in order to determine the wheel rate, then measure the motion ratio of the shock mounting point to back-figure into the spring rate you want. You'll also want to measure the shock angle so that you can use the sine ratio to determine what you need for an actual spring rate since your initial calculations will only give you the vertical rate without correcting for the mounting angle. Clear as mud right?
10-25-2014, 04:10 PM
#79
Drifting
10-26-2014, 02:11 AM
#80
Safety Car
And since progressiveness has no scale. . . yeah.
Well here's food for thought with respect to the original post: my 4th gen Camaro doesn't turn enough, so I installed softer rear springs. Sounds bass ackwards, right? I had to take a leap of faith on that one as I was running much stiffer rears than anyone else. I had 950 fronts (that I changed for 900 fronts at the end of practice) and 325 rears (that were changed to 275 before practice) and the car just plowed. When I threw the 275s on out back, the car still plowed. . . until I hit the gas. Then the car rotated. In most cases, I wouldn't even call it a drift, the car simply turned. Now the kicker was that the entry speed required made the car understeer mid corner. At that very moment, it was necessary (and counter-intuitive) to apply throttle at which point the car would begin to turn and exit faster than it ever did. Go figure. With the 325s it broke away more suddenly, so the car transitioned directly to a drift instead of just getting around the corner. I'd lose speed that way and it just didn't work for me. It was with this setup that I nailed down my first win, so I considered it a step in the right direction.
Well here's food for thought with respect to the original post: my 4th gen Camaro doesn't turn enough, so I installed softer rear springs. Sounds bass ackwards, right? I had to take a leap of faith on that one as I was running much stiffer rears than anyone else. I had 950 fronts (that I changed for 900 fronts at the end of practice) and 325 rears (that were changed to 275 before practice) and the car just plowed. When I threw the 275s on out back, the car still plowed. . . until I hit the gas. Then the car rotated. In most cases, I wouldn't even call it a drift, the car simply turned. Now the kicker was that the entry speed required made the car understeer mid corner. At that very moment, it was necessary (and counter-intuitive) to apply throttle at which point the car would begin to turn and exit faster than it ever did. Go figure. With the 325s it broke away more suddenly, so the car transitioned directly to a drift instead of just getting around the corner. I'd lose speed that way and it just didn't work for me. It was with this setup that I nailed down my first win, so I considered it a step in the right direction.