Sean's C5 Chevrolet Corvette Z06 in Alberta, Canada
Encouraging and engaging, Sean S. has been a true delight to work with since our first contact. Initially, he came to us asking about a suspension for his '05 Subaru Legacy sedan. That ended up being delayed but in the meanwhile he had been planning to purchase a 2002 Corvette C5 Z06. The C5 Z06 one of the best turn-key sports cars even made. In fact, there's a great thread on CorvetteForum.com about it - 'What makes the 2004 Z06 shocks so good?' and I've read it quite carefully. I'll admit, I've been curious about this car since seeing it live at autocrosses in the early 2000s. I was eager for the chance to see what GM had done and what I could do to make the setup even better (if possible!). Always approaching with the attitude of discovery and respect for the work that's been done, then see what can be built upon it. We all stand on the shoulders of giants. Dennis Grant on his Far North Racing website has some interesting analysis and data that inspired me to dig deeper into what indeed made those dampers - tuned on the famous Nurburgring - so good.
Sean's early emails contained his desire for improvement:
Sean's early emails contained his desire for improvement:
Shaikh,
I picked up the C5 last Friday. It was a fun drive back. I just wanted to give you my initial impressions on the stock suspension with about 50000 miles on them.
1. The car is surprisingly comfortable! On the highway and in the city. I think I can feel the flat ride spring rates in the works. Over smaller imperfections on the road, the car glides over them very well, a little bit of the impact gets passed into the seat, and the car settles with just one stroke. Over the bigger bumps, the suspension is still fairly comfortable without bounces, but it does feel that the suspension works a little harder to keep the car's composure. Sometimes it feels like the rear of the car accelerates downward after a big bump. Driving over continuous bumps and very uneven pavement, the car still soaks up the bumps well, there is definitely some body motion (engaging the bump stops?). Car feels busy, but not nervous.
2. Handling is still to be determined... If there was ever a contest of handling capability vs OEM seat holding capacity, this C5 Z06 would be up there on the podium. The stock seat is very slippery, and the door panel flexes when I try to brace myself with my knees. I have not been able to really test the handling of the car. The steering wheel has a bit of a dead spot on center, I think this could be improved with newer control arm bushings and steering column bushings. Turn in feels good, not the super rebound biased feeling. There is just a hint of under steer. The weight transfer feels fairly smooth and predictable, without any wobbly feeling. Once the weight is set, the car holds its lines throughout the corner. On corner exits, car squats down and goes; I have not dared to really dig into throttle on corner exits yet, but I predict there would be a bit of tail happy actions if throttle is applied more. The car seems to have pretty decent roll control, there is no significant body roll at the speeds I have tried yet.
3. Brake dive. The brake dive is very pronounced. It does not take much brake force to hear the front air dam scraping the road.
Overall, I am very happy with the car. Every time I drive the car, I appreciate the level of engineering and the thoughts that were put into designing it. Like you said in an earlier email, the car is relatively soft sprung, and it still has its handling capabilities. I am very looking forward to seeing what you and your team can do to improve the suspension on this great platform. Please keep me updated on the build schedule.
Thanks,
Sean
I picked up the C5 last Friday. It was a fun drive back. I just wanted to give you my initial impressions on the stock suspension with about 50000 miles on them.
1. The car is surprisingly comfortable! On the highway and in the city. I think I can feel the flat ride spring rates in the works. Over smaller imperfections on the road, the car glides over them very well, a little bit of the impact gets passed into the seat, and the car settles with just one stroke. Over the bigger bumps, the suspension is still fairly comfortable without bounces, but it does feel that the suspension works a little harder to keep the car's composure. Sometimes it feels like the rear of the car accelerates downward after a big bump. Driving over continuous bumps and very uneven pavement, the car still soaks up the bumps well, there is definitely some body motion (engaging the bump stops?). Car feels busy, but not nervous.
2. Handling is still to be determined... If there was ever a contest of handling capability vs OEM seat holding capacity, this C5 Z06 would be up there on the podium. The stock seat is very slippery, and the door panel flexes when I try to brace myself with my knees. I have not been able to really test the handling of the car. The steering wheel has a bit of a dead spot on center, I think this could be improved with newer control arm bushings and steering column bushings. Turn in feels good, not the super rebound biased feeling. There is just a hint of under steer. The weight transfer feels fairly smooth and predictable, without any wobbly feeling. Once the weight is set, the car holds its lines throughout the corner. On corner exits, car squats down and goes; I have not dared to really dig into throttle on corner exits yet, but I predict there would be a bit of tail happy actions if throttle is applied more. The car seems to have pretty decent roll control, there is no significant body roll at the speeds I have tried yet.
3. Brake dive. The brake dive is very pronounced. It does not take much brake force to hear the front air dam scraping the road.
Overall, I am very happy with the car. Every time I drive the car, I appreciate the level of engineering and the thoughts that were put into designing it. Like you said in an earlier email, the car is relatively soft sprung, and it still has its handling capabilities. I am very looking forward to seeing what you and your team can do to improve the suspension on this great platform. Please keep me updated on the build schedule.
Thanks,
Sean
I had to do my homework to analyze what GM had done, decipher their intentions. In the interest of keeping some of their recipe secret, I won't share the nitty gritty details here (perhaps on our Suspension Truth forum for those who want to dig). But I did see room for improvement based on what I knew.
Some of the features that GM has always included in the Corvette design is 'Flat Ride', the idea that the rear suspension natural frequency must be slightly higher than the front. This is also used by other vehicle automakers, notably Porsche, BMW, and Mazda. However it's not mentioned anywhere as a benefit for a sports car. Clearly, GM knew this is important as they had, since the early 1930's, been engaged with a brilliant engineer, Maurice Olley, who literally wrote the book on vehicle suspension design in his time.
I made calculations to damping ratios, rebound to bump ratio, gas force, the required amount of ripple reducer behavior (through holes) while still maintaining enough low speed damping force.
It took about a month and I went on to other projects but was very curious what Sean's impressions would be. He finally got back to me and this was his feedback:
Some of the features that GM has always included in the Corvette design is 'Flat Ride', the idea that the rear suspension natural frequency must be slightly higher than the front. This is also used by other vehicle automakers, notably Porsche, BMW, and Mazda. However it's not mentioned anywhere as a benefit for a sports car. Clearly, GM knew this is important as they had, since the early 1930's, been engaged with a brilliant engineer, Maurice Olley, who literally wrote the book on vehicle suspension design in his time.
I made calculations to damping ratios, rebound to bump ratio, gas force, the required amount of ripple reducer behavior (through holes) while still maintaining enough low speed damping force.
It took about a month and I went on to other projects but was very curious what Sean's impressions would be. He finally got back to me and this was his feedback:
Shaikh,
I have sorted out the engine electronic issue, and got a chance to install the shocks on Saturday. I have had some street miles on the shocks, and I did one lapping day on the short track on Sunday. I would like to give you a quick and short review of the shocks based on my initial impressions. I will have to drive the car a little more to give you a detailed review. In a few words, the shocks are good, VERY GOOD!
The ride quality is very impressive. Everything is dealt with in just one stroke. The shocks do a great job of filtering out the smaller imperfections. I could hear the tire making impact with the road, but barely or do not feel the impact in my seat. There is one big dip and big bump (looks like v^ from the side) in my neighborhood that makes just about every car feel like bottoming out, I've even seen motorcycles catching a bit of air when going through there with speed. With the FCM shocks, I could feel the car following the contour of the road, but the impact after the ^ felt a lot less than stock, and the tires always felt connected to the road. It did not feel like bottoming out at any point. I traded cars with Justin (Porsche 996C2 with factory X73 kit) driving back from track. His summary was: the car felt very smooth, everything was dealt with in one stroke, and the shocks do a great job of smoothing out the road while still providing feedback. I asked him how did it feel around the big high speed sweeper with lots of mid corner bumps, because in the Porsche the car was relatively stable but the bumps were upsetting the steering wheel a little bit. His answer was "No I did not feel the bumps."
Now onto handling: it only took about 2 corners driving out of my neighborhood to know the car was completely different. The best way I could describe it is the car has got more tires now. The biggest difference was in the rear end. The stock shocks had a feeling of the rear end might slip out under me without notice. That was how it felt at the first track day: the rear did not have enough grip, and it would easily give out if I applied throttle just a bit early. I used to drive with traction control on, because I wasn't sure when the rear end would slip out or if I could easily recover. After just a few corners on the street, the car gave me a lot of confidence. The track day further confirmed the confidence: it allowed me to corner faster, and get onto throttle as soon as I hit apex. It is almost like my AWD Subaru coming out of corners. I felt like a superman driving out of high speed sweeper turns (until the oil really heated up after a few laps... well, another issue to address...). The tires sticked to the ground very well and would only gradually give away if I do something wrong. In the tighter turns, the car had much better composure and body roll control. In the braking zone and corner entry, stability was much improved. The added low speed compression really helped.
That's it for the short review which turned out kinda long. I am very pleased with the improvements that these shocks made in both handling and ride quality. I am very excited to find out how much further I can improve the car with new bushings, front sway bar, and a good alignment, but first I need to address the oil temperature issue. I will continue to give you updates as I put on more street miles and track days on the car. I will send you the stock shocks soon.
Thanks,
Sean
I have sorted out the engine electronic issue, and got a chance to install the shocks on Saturday. I have had some street miles on the shocks, and I did one lapping day on the short track on Sunday. I would like to give you a quick and short review of the shocks based on my initial impressions. I will have to drive the car a little more to give you a detailed review. In a few words, the shocks are good, VERY GOOD!
The ride quality is very impressive. Everything is dealt with in just one stroke. The shocks do a great job of filtering out the smaller imperfections. I could hear the tire making impact with the road, but barely or do not feel the impact in my seat. There is one big dip and big bump (looks like v^ from the side) in my neighborhood that makes just about every car feel like bottoming out, I've even seen motorcycles catching a bit of air when going through there with speed. With the FCM shocks, I could feel the car following the contour of the road, but the impact after the ^ felt a lot less than stock, and the tires always felt connected to the road. It did not feel like bottoming out at any point. I traded cars with Justin (Porsche 996C2 with factory X73 kit) driving back from track. His summary was: the car felt very smooth, everything was dealt with in one stroke, and the shocks do a great job of smoothing out the road while still providing feedback. I asked him how did it feel around the big high speed sweeper with lots of mid corner bumps, because in the Porsche the car was relatively stable but the bumps were upsetting the steering wheel a little bit. His answer was "No I did not feel the bumps."
Now onto handling: it only took about 2 corners driving out of my neighborhood to know the car was completely different. The best way I could describe it is the car has got more tires now. The biggest difference was in the rear end. The stock shocks had a feeling of the rear end might slip out under me without notice. That was how it felt at the first track day: the rear did not have enough grip, and it would easily give out if I applied throttle just a bit early. I used to drive with traction control on, because I wasn't sure when the rear end would slip out or if I could easily recover. After just a few corners on the street, the car gave me a lot of confidence. The track day further confirmed the confidence: it allowed me to corner faster, and get onto throttle as soon as I hit apex. It is almost like my AWD Subaru coming out of corners. I felt like a superman driving out of high speed sweeper turns (until the oil really heated up after a few laps... well, another issue to address...). The tires sticked to the ground very well and would only gradually give away if I do something wrong. In the tighter turns, the car had much better composure and body roll control. In the braking zone and corner entry, stability was much improved. The added low speed compression really helped.
That's it for the short review which turned out kinda long. I am very pleased with the improvements that these shocks made in both handling and ride quality. I am very excited to find out how much further I can improve the car with new bushings, front sway bar, and a good alignment, but first I need to address the oil temperature issue. I will continue to give you updates as I put on more street miles and track days on the car. I will send you the stock shocks soon.
Thanks,
Sean
A couple weeks later we had a great phone conversation and he mentioned again how much a a joy the new suspension was. Being even the perfectionist, I imagined where we could make it better. At the time he hadn't selcted our KBO option but I knew that upgrade would further improve the ride quality on more sudden impact of rough roads or expansion joints. The ability of the car to develop even more grip was notably, and important since the only change we made was to the dampers - not spring rates, alignment, tire pressure or any other variables. We simply had developed a faster, more comfortable, more composed suspension for the already amazing C5 Z06 Corvette chassis.
But not GM has moved on to including MagneRide and active suspension control on more models. I understand the impetus for this on a few levels: technology does advance and other companies are including similar technologies so one needs an 'edge.' But, having seen the complexity and repair cost associated with electronically-controlled damping and air-bag-equipped suspensions, I am very hesitant to recommend them for our customers or feel them appropriate for daily-driven vehicles that see tens or hundreds of thousands of miles. An Audi customer, Greg W., has had many headaches integrating an airbag system to his S4 Avant wagon. I don't think it's anyone's fault per se, but he's dealt with much downtime not having his vehicle working properly, plus expense that isn't warrantied. I couldn't in good conscience recommend any kind of active damping system for street use unless there was a very strong extended warranty and extensive testing of the technology establishing a realistic baseline for durability. Also, those systems are nearly never serviceable so the damper itself must be thrown away and another purchase - another level of waste.
We've proven that through keeping it simple (and designing for efficiency, durability, and harmony) we also get the best grip. I'd venture that a setup with our KBO, Ripple Reducer and FCM Elite tuning methods would rank very high in a comparison test with a more expensive semi-active damping system! Perhaps we'll be able to test that hypothesis out sometime soon...
I feel it would be truly a great asset to give their high-end customers the option to order a tailored suspension, something like what we do for them. Even if it was just a great 'off the shelf' factory option through FCM Elite, this would be a way to get the most elegant, effective technology into their customers hands. The active suspension could still be available, but to truly keep the customer's well-being in mind, a less complicated or costly to replace solution would shine.
Perhaps I'm too idealistic that GM would even come to me and ask to incorporate KBO, Ripple Reducer, into building .. but I can still dream big!
But not GM has moved on to including MagneRide and active suspension control on more models. I understand the impetus for this on a few levels: technology does advance and other companies are including similar technologies so one needs an 'edge.' But, having seen the complexity and repair cost associated with electronically-controlled damping and air-bag-equipped suspensions, I am very hesitant to recommend them for our customers or feel them appropriate for daily-driven vehicles that see tens or hundreds of thousands of miles. An Audi customer, Greg W., has had many headaches integrating an airbag system to his S4 Avant wagon. I don't think it's anyone's fault per se, but he's dealt with much downtime not having his vehicle working properly, plus expense that isn't warrantied. I couldn't in good conscience recommend any kind of active damping system for street use unless there was a very strong extended warranty and extensive testing of the technology establishing a realistic baseline for durability. Also, those systems are nearly never serviceable so the damper itself must be thrown away and another purchase - another level of waste.
We've proven that through keeping it simple (and designing for efficiency, durability, and harmony) we also get the best grip. I'd venture that a setup with our KBO, Ripple Reducer and FCM Elite tuning methods would rank very high in a comparison test with a more expensive semi-active damping system! Perhaps we'll be able to test that hypothesis out sometime soon...
I feel it would be truly a great asset to give their high-end customers the option to order a tailored suspension, something like what we do for them. Even if it was just a great 'off the shelf' factory option through FCM Elite, this would be a way to get the most elegant, effective technology into their customers hands. The active suspension could still be available, but to truly keep the customer's well-being in mind, a less complicated or costly to replace solution would shine.
Perhaps I'm too idealistic that GM would even come to me and ask to incorporate KBO, Ripple Reducer, into building .. but I can still dream big!
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