2014 Corvette
09-09-2013, 08:49 PM
#286
Interesting factoid is that GM does not race the Corvette with the leaf springs, though. They use coils over dampers to race the Corvette.
GM could go a long way to showing how "advanced" the leaf spring is IF they raced on it.
I know that I'd be more proud with the leaf springs if they raced on it.
But, they don't.
Tells a lot, I think.
09-09-2013, 09:53 PM
#287
Drifting
I don't think there are many technical drawbacks to the advanced design the later Corvettes have been using. But you will know within ten seconds of driving away that you're in a Corvette and not a higher-quality European or Japanese car, and the leaf springs are a big part of the reason why. They just don't feel right.
Last edited by GSIRM3; 09-10-2013 at 12:39 PM.
09-10-2013, 01:53 AM
#288
Intermediate
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OK, just to be clear. Carroll Smith said he thought the transverse, fiberglass leaf spring was an ideal part for a road going car. Porsche has a recent patent on such a design.
I agree that it would help the leaf spring PR case if the C5R and C6R used them. However, if you know anything about racing components you quickly understand why they don't. It's not because the concept is flawed. I knew a guy with a Formula Ford who was running "Indy car" shocks. Literally the shocks on his FF were used dampers from an Indy car (CART actually). Why? Easy, because in racing many components are from common vendors. I wouldn't be surprised if several of the cars racing against the C6R were using the same dampers likely purchased from Penskee or Ohlin.
Let's also consider other issues for porting the leaf spring into racing.
1. Some Corvette leaf springs have failed due to high temperatures. You get someone who does a custom exhaust that dumps in front of the leaf. The resin bakes and the spring fails. Interestingly, one of the hardest design challenges for the team developing the first Corvette fiberglass springs in the 1970s was heat. The spring has EXCELLENT mechanical properties. It's in almost every way superior to steel as a spring material. However, it is not very heat resistant. The transmission and exhaust in the road car are pushing the safe limit for those springs. The added heat of the racing units could be very problematic.
OK, what next. Well race springs, which are actually quite different from road car springs, need to have very precise rate control. I'm not sure if the Corvette leaf spring has better rate control than a Hyperco race spring. It's certainly no worse than the steel coils on a Porsche but hey, let's be honest, the road going coils and those in the race prepped cars aren't the same thing. This basically says, leaf springs of the precise rates the race engineers need are not off the shelf items. Conversely, the coil springs on a racing C6 might be the exact same part as a similar rate coil spring used on a competing car. Hyperco can deliver just about any rate coil spring you want (in reason) even if they don't stock it. Ask how much they charge to get you a custom rate leaf spring...
Another big difference between the race stuff and the street stuff is service life. The race stuff is run at the edge of the material properties. If those springs last 10k miles great! The street car stuff must have longer suspension throw and is expected to last the life of the car even if that life includes sun, rain, salt, gravel roads and full suspension cycles. When GM was developing the leaf spring they did a cycle test on the thing. The springs basically never failed. From what I gather they have better long term mechanical properties than any steel spring. They also have a higher energy density. When GM switched from the C3's coils to the C4's front leaf the total spring weight was 1/3rd.
I also think it's worth noting what types of springs are used on F1 cars and many top LMP cars. No, not coils. Most are now using torsion beams. The crappy old twist beam stuff like an old VW Bug, old 911 or a 1979 GM pick up truck.
Anyway, race cars have many neat solutions but what works or is best for a race car often has little to do with what is best for a road car.
I agree that it would help the leaf spring PR case if the C5R and C6R used them. However, if you know anything about racing components you quickly understand why they don't. It's not because the concept is flawed. I knew a guy with a Formula Ford who was running "Indy car" shocks. Literally the shocks on his FF were used dampers from an Indy car (CART actually). Why? Easy, because in racing many components are from common vendors. I wouldn't be surprised if several of the cars racing against the C6R were using the same dampers likely purchased from Penskee or Ohlin.
Let's also consider other issues for porting the leaf spring into racing.
1. Some Corvette leaf springs have failed due to high temperatures. You get someone who does a custom exhaust that dumps in front of the leaf. The resin bakes and the spring fails. Interestingly, one of the hardest design challenges for the team developing the first Corvette fiberglass springs in the 1970s was heat. The spring has EXCELLENT mechanical properties. It's in almost every way superior to steel as a spring material. However, it is not very heat resistant. The transmission and exhaust in the road car are pushing the safe limit for those springs. The added heat of the racing units could be very problematic.
OK, what next. Well race springs, which are actually quite different from road car springs, need to have very precise rate control. I'm not sure if the Corvette leaf spring has better rate control than a Hyperco race spring. It's certainly no worse than the steel coils on a Porsche but hey, let's be honest, the road going coils and those in the race prepped cars aren't the same thing. This basically says, leaf springs of the precise rates the race engineers need are not off the shelf items. Conversely, the coil springs on a racing C6 might be the exact same part as a similar rate coil spring used on a competing car. Hyperco can deliver just about any rate coil spring you want (in reason) even if they don't stock it. Ask how much they charge to get you a custom rate leaf spring...
Another big difference between the race stuff and the street stuff is service life. The race stuff is run at the edge of the material properties. If those springs last 10k miles great! The street car stuff must have longer suspension throw and is expected to last the life of the car even if that life includes sun, rain, salt, gravel roads and full suspension cycles. When GM was developing the leaf spring they did a cycle test on the thing. The springs basically never failed. From what I gather they have better long term mechanical properties than any steel spring. They also have a higher energy density. When GM switched from the C3's coils to the C4's front leaf the total spring weight was 1/3rd.
I also think it's worth noting what types of springs are used on F1 cars and many top LMP cars. No, not coils. Most are now using torsion beams. The crappy old twist beam stuff like an old VW Bug, old 911 or a 1979 GM pick up truck.
Anyway, race cars have many neat solutions but what works or is best for a race car often has little to do with what is best for a road car.
09-10-2013, 09:36 AM
#289
Porsche has always raced the 911 with the engine in the rear.
Interesting factoid is that GM does not race the Corvette with the leaf springs, though. They use coils over dampers to race the Corvette.
GM could go a long way to showing how "advanced" the leaf spring is IF they raced on it.
I know that I'd be more proud with the leaf springs if they raced on it.
But, they don't.
Tells a lot, I think.
Interesting factoid is that GM does not race the Corvette with the leaf springs, though. They use coils over dampers to race the Corvette.
GM could go a long way to showing how "advanced" the leaf spring is IF they raced on it.
I know that I'd be more proud with the leaf springs if they raced on it.
But, they don't.
Tells a lot, I think.
A composite leaf spring has many benefits over a coil spring. Weight saving, installed height and low center of gravity. Someone who says they can get in a vett and feel the leaf spring is FOS. There is so much to a suspension/chassis design to say you feel one element makes you a suspension savant. All car companies need a guy like that.
Bottom line to me is that the Vett is very close in performance to a 911. One can argue the fine points. The fact that there are fine points to argue is a testament to the Vetts design at half the price. I am rooting for the home team, not ashamed of it. They did not attempt to create a car as expensive as the Porsche. They succeeded. They attempted to design a car on par with the performance of the 911, again in my mind they succeeded based on early reports.
Do the cars compete, I am not sure. They don't to me, different market. I'll bet more than a few people have both.
09-10-2013, 10:59 AM
#290
That is like me saying every purpose built Porsche race car is mid engine, if they used a rear engine it would say a lot. I brought up the rear engine configuration because it is an unusual configuration just as the leaf spring might be considered.
A composite leaf spring has many benefits over a coil spring. Weight saving, installed height and low center of gravity. Someone who says they can get in a vett and feel the leaf spring is FOS. There is so much to a suspension/chassis design to say you feel one element makes you a suspension savant. All car companies need a guy like that.
Bottom line to me is that the Vett is very close in performance to a 911. One can argue the fine points. The fact that there are fine points to argue is a testament to the Vetts design at half the price. I am rooting for the home team, not ashamed of it. They did not attempt to create a car as expensive as the Porsche. They succeeded. They attempted to design a car on par with the performance of the 911, again in my mind they succeeded based on early reports.
Do the cars compete, I am not sure. They don't to me, different market. I'll bet more than a few people have both.
A composite leaf spring has many benefits over a coil spring. Weight saving, installed height and low center of gravity. Someone who says they can get in a vett and feel the leaf spring is FOS. There is so much to a suspension/chassis design to say you feel one element makes you a suspension savant. All car companies need a guy like that.
Bottom line to me is that the Vett is very close in performance to a 911. One can argue the fine points. The fact that there are fine points to argue is a testament to the Vetts design at half the price. I am rooting for the home team, not ashamed of it. They did not attempt to create a car as expensive as the Porsche. They succeeded. They attempted to design a car on par with the performance of the 911, again in my mind they succeeded based on early reports.
Do the cars compete, I am not sure. They don't to me, different market. I'll bet more than a few people have both.
Yet, the issue remains unaddressed... if leaf springs are good enough, why doesn't GM, or Porsche with the patent that LSJU speaks of, race on leaf springs?
If GM Corvette racing RACED on leaf springs, and won, that would settle the issue.
But, they don't.
09-10-2013, 11:14 AM
#291
OK, just to be clear. Carroll Smith said he thought the transverse, fiberglass leaf spring was an ideal part for a road going car. Porsche has a recent patent on such a design.
I agree that it would help the leaf spring PR case if the C5R and C6R used them. However, if you know anything about racing components you quickly understand why they don't. It's not because the concept is flawed. I knew a guy with a Formula Ford who was running "Indy car" shocks. Literally the shocks on his FF were used dampers from an Indy car (CART actually). Why? Easy, because in racing many components are from common vendors. I wouldn't be surprised if several of the cars racing against the C6R were using the same dampers likely purchased from Penskee or Ohlin.
Let's also consider other issues for porting the leaf spring into racing.
1. Some Corvette leaf springs have failed due to high temperatures. You get someone who does a custom exhaust that dumps in front of the leaf. The resin bakes and the spring fails. Interestingly, one of the hardest design challenges for the team developing the first Corvette fiberglass springs in the 1970s was heat. The spring has EXCELLENT mechanical properties. It's in almost every way superior to steel as a spring material. However, it is not very heat resistant. The transmission and exhaust in the road car are pushing the safe limit for those springs. The added heat of the racing units could be very problematic.
OK, what next. Well race springs, which are actually quite different from road car springs, need to have very precise rate control. I'm not sure if the Corvette leaf spring has better rate control than a Hyperco race spring. It's certainly no worse than the steel coils on a Porsche but hey, let's be honest, the road going coils and those in the race prepped cars aren't the same thing. This basically says, leaf springs of the precise rates the race engineers need are not off the shelf items. Conversely, the coil springs on a racing C6 might be the exact same part as a similar rate coil spring used on a competing car. Hyperco can deliver just about any rate coil spring you want (in reason) even if they don't stock it. Ask how much they charge to get you a custom rate leaf spring...
Another big difference between the race stuff and the street stuff is service life. The race stuff is run at the edge of the material properties. If those springs last 10k miles great! The street car stuff must have longer suspension throw and is expected to last the life of the car even if that life includes sun, rain, salt, gravel roads and full suspension cycles. When GM was developing the leaf spring they did a cycle test on the thing. The springs basically never failed. From what I gather they have better long term mechanical properties than any steel spring. They also have a higher energy density. When GM switched from the C3's coils to the C4's front leaf the total spring weight was 1/3rd.
I also think it's worth noting what types of springs are used on F1 cars and many top LMP cars. No, not coils. Most are now using torsion beams. The crappy old twist beam stuff like an old VW Bug, old 911 or a 1979 GM pick up truck.
Anyway, race cars have many neat solutions but what works or is best for a race car often has little to do with what is best for a road car.
I agree that it would help the leaf spring PR case if the C5R and C6R used them. However, if you know anything about racing components you quickly understand why they don't. It's not because the concept is flawed. I knew a guy with a Formula Ford who was running "Indy car" shocks. Literally the shocks on his FF were used dampers from an Indy car (CART actually). Why? Easy, because in racing many components are from common vendors. I wouldn't be surprised if several of the cars racing against the C6R were using the same dampers likely purchased from Penskee or Ohlin.
Let's also consider other issues for porting the leaf spring into racing.
1. Some Corvette leaf springs have failed due to high temperatures. You get someone who does a custom exhaust that dumps in front of the leaf. The resin bakes and the spring fails. Interestingly, one of the hardest design challenges for the team developing the first Corvette fiberglass springs in the 1970s was heat. The spring has EXCELLENT mechanical properties. It's in almost every way superior to steel as a spring material. However, it is not very heat resistant. The transmission and exhaust in the road car are pushing the safe limit for those springs. The added heat of the racing units could be very problematic.
OK, what next. Well race springs, which are actually quite different from road car springs, need to have very precise rate control. I'm not sure if the Corvette leaf spring has better rate control than a Hyperco race spring. It's certainly no worse than the steel coils on a Porsche but hey, let's be honest, the road going coils and those in the race prepped cars aren't the same thing. This basically says, leaf springs of the precise rates the race engineers need are not off the shelf items. Conversely, the coil springs on a racing C6 might be the exact same part as a similar rate coil spring used on a competing car. Hyperco can deliver just about any rate coil spring you want (in reason) even if they don't stock it. Ask how much they charge to get you a custom rate leaf spring...
Another big difference between the race stuff and the street stuff is service life. The race stuff is run at the edge of the material properties. If those springs last 10k miles great! The street car stuff must have longer suspension throw and is expected to last the life of the car even if that life includes sun, rain, salt, gravel roads and full suspension cycles. When GM was developing the leaf spring they did a cycle test on the thing. The springs basically never failed. From what I gather they have better long term mechanical properties than any steel spring. They also have a higher energy density. When GM switched from the C3's coils to the C4's front leaf the total spring weight was 1/3rd.
I also think it's worth noting what types of springs are used on F1 cars and many top LMP cars. No, not coils. Most are now using torsion beams. The crappy old twist beam stuff like an old VW Bug, old 911 or a 1979 GM pick up truck.
Anyway, race cars have many neat solutions but what works or is best for a race car often has little to do with what is best for a road car.
09-10-2013, 11:57 AM
#292
It is a pissing contest, why doesn't Porsche build all their purpose built race cars with a rear engine? Because it has it benefits and it has it weaknesses like all designs it is a compromise.
09-10-2013, 11:59 AM
#293
You talk like coils are expensive, or complex or special? Its a coil spring, same $.20 ball point pen.
09-10-2013, 11:59 AM
#294
The more I see it, the less I care for the C7 looks (my initial thought was that maybe it would grow on me, instead it grates), I like the 911 engine note more, the fact that the history is much more present, the distinct driving feel with the rear-engine, etc., but I'm all for GM making a very competitive sports car at 1/2 the price even if I'm not in line to buy one.
If it motivates Porsche to give us an on/off rev-match option in the PCM for the MT (say, with on/off per driving mode?), even better.
(Yeah, I know it's not happening... Too bad, because I'd set it the opposite of how Porsche defaults it, making normal mode 'easy' with auto rev-match and then going heel-toe in sports, while others might do the opposite - or whatever they want. Such a small software option... Maybe for $1000?
)Sorry, I digress... uh, C7!
09-10-2013, 12:02 PM
#295
I'm not sure if you mean "no more than a few people have both"? I'd think that for 98%+ of potential buyers they're not really overlapping, and I'm not sure how many people own both a 'vette and 911.
The more I see it, the less I care for the C7 looks (my initial thought was that maybe it would grow on me, instead it grates), I like the 911 engine note more, the fact that the history is much more present, the distinct driving feel with the rear-engine, etc., but I'm all for GM making a very competitive sports car at 1/2 the price even if I'm not in line to buy one.
If it motivates Porsche to give us an on/off rev-match option in the PCM for the MT (say, with on/off per driving mode?), even better.
(Yeah, I know it's not happening... Too bad, because I'd set it the opposite of how Porsche defaults it, making normal mode 'easy' with auto rev-match and then going heel-toe in sports, while others might do the opposite - or whatever they want. Such a small software option... Maybe for $1000? )
Sorry, I digress... uh, C7!
The more I see it, the less I care for the C7 looks (my initial thought was that maybe it would grow on me, instead it grates), I like the 911 engine note more, the fact that the history is much more present, the distinct driving feel with the rear-engine, etc., but I'm all for GM making a very competitive sports car at 1/2 the price even if I'm not in line to buy one.
If it motivates Porsche to give us an on/off rev-match option in the PCM for the MT (say, with on/off per driving mode?), even better.
(Yeah, I know it's not happening... Too bad, because I'd set it the opposite of how Porsche defaults it, making normal mode 'easy' with auto rev-match and then going heel-toe in sports, while others might do the opposite - or whatever they want. Such a small software option... Maybe for $1000?
)Sorry, I digress... uh, C7!
09-10-2013, 01:40 PM
#296
Rennlist Member
A composite leaf spring has many benefits over a coil spring. Weight saving, installed height and low center of gravity. Someone who says they can get in a vett and feel the leaf spring is FOS. There is so much to a suspension/chassis design to say you feel one element makes you a suspension savant. All car companies need a guy like that.
09-10-2013, 03:16 PM
#298
Race Director
Notwithstanding the pos of a leaf, I simply i dont like it because of its lack of adjustability and the shuddering feel i get on one side when the opposite side impacts something like curbing. GOSPEL? You're inferring way more than there is.
09-10-2013, 03:22 PM
#299
Three Wheelin'
That's the logical thing to do for us as driving enthusiasts, that's how I would do it too. But that wouldn't sell the sportchrono for Porsche ;-)
09-10-2013, 03:25 PM
#300
Drifting
Yeah, reminds me of the days when my 1985 $55,000 911 had torsion bar and trailing arm suspension. If Porsche still used that setup, some people would probably argue that it is better because it is used on a Porsche.
Last edited by GSIRM3; 09-10-2013 at 04:11 PM.