Sean's C5 Chevrolet Corvette Z06 in Alberta, Canada

Sean's C5 Z06 Chevy Corvette
Supportive 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 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:

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.


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 and making sure the suspension is not jacking down.

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:

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.



A few thoughts on Complexity vs. Simplicity in Suspension Design

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 that C5 Corvette chassis was built from 1997 to 2004, the last new model coming off the production line nearly 12 years ago at this writing (2016). As wonderful as Sean's car is, the C5 is no longer being made although you can buy a used example and improve it as we've done for Sean. However, imagine someone says "that's very nice, but I'm going to buy a NEWER C6 or brand-new C7 Corvette and it'll be even better than Sean's!" Are we at Fat Cat Motorsports simply 'behind the times', and would attract a wider audience if we focused on the newest fancy electronically-controlled suspension technology? Are we having to deal with a situation where the newer Corvettes are better in the ride and handling department than the best we can do? Granted, the newer cars have more horsepower but that's not the topic at hand - any Corvette since 1997 will be wicked fast and more car than 99% of drivers can handle.

So the question that compels me now, having had this positive experience with the C5 Z06, is "does a new C7 Z06, with MagneRide semi-active suspension technology, ride and handle better than Sean's FCM Elite - improved C5 Z06?" It's a very interesting question and one I'd love to answer. Yet, until I can get his vehicle or another local vehicle (Sean's in Canada and we're in California!) to compare to a C7 Z06, it'll just be an intellectual exercise. But question does provoke other trains of thought regarding the benefits and drawbacks of technology especially in the real-world driving environment. We have some experience examining semi-active suspensions and it's not an immediate 'home run'. As I mention in the first 'Playing with Knobs' video, the baseline damping curve really needs to be tuned with several important design chocies in mind otherwise you are adjusting the dampers from 'very bad' to 'less bad' in terms of potential ride quality and grip. When you don't know how the factory designed the suspension and you don't have data or someone willing to share information with you, it's like going to a restaurant where you sit in the dark and are fed blind-folded. In the case of a vehicle's suspension design, you're figuratively closing your eyes and opening your mouth not knowing if the food you're being offered will be tasty and nourishing or foul and upsetting.

The idea of 'newer tech' beating out 'older tech' particularly arises when we speak about modifications. There is often the idea that because the factory has created some new technology such as semi-active suspension, no changes would make sense because one of the 'factory available settings' would cover all your needs. To briefly explain, semi-active suspension is where road and chassis sensor feedback helps the suspension computer decide what changes to make to each damper in very short time periods. Usually those changes are limited to changing rebound and compression damping together, but not separately. There is also the very real possibility (as we saw working on the R35 Nissan GT-R chassis) that the 'Sport' mode is ridiculously stiff. Later models were softened but it still was shocking to see how dramatically the forces increased which essentially made th car more prone to understeer while 'feeling' stiffer. It was not truly a performance advantage vs. having a better-optimized initial damping curve, as we did for the customer using the original-equipment Damptronic Bilsteins.

Let's take a look at the idea that any new technology must ONLY bring advantages without any disadvantages? No and no we can certainly answer. But this is never spoken about widely, just the assumption that 'the newest tech must always be better' and 'leave the past behind, it's no longer relevant.' That kind of thinking is dangerous in many ways we won't get into here (only focusing on suspension design and technology!). There MAY be benefits to technology such as MagneRide, GM's semi-active suspension system (which is now used on even more models than just the newest Corvettes) but what are the drawbacks?

I understand the impetus for this technology: there can be improvements in both handling and control when you can have an intelligent algorithm plus sensors to determine what the ground and chassis are doing and how to make adjustments to maximize grip or ride (but almost certainly not both at the same time). This, if anything, is my biggest problem with the newer semi-active suspensions. They can be excellent for control on a road course and have advantages there (which is why most santioning bodies outlaw them) but the real-world environment demands a long-lasting design that rewards simplicity not complexity. I have seen what amazing comfort is possible with a well-optimized suspension, each element working in harmony with the other, nothing out of place either too much or too little. It's an exercise in balance, proportion, sensitivity truly like a dance but done in design space rather than physical space. however, the dance plays out in physical space.

Lucky, or well-designed?

As Carroll Smith succinctly said, quoting Branch Rickey (the originator) - "Luck is the residue of design." I know it! Otherwise I'd never have intuitively felt confident avoiding a squirrel in the middle of Turn 6 at Laguna Seca! (By the way, I comfortably passed that Porsche 964 a lap later on the inside of Turn 9). I have found that the window where you can achieve excellent handling is very close to the window where you achieve ultimate grip. There is an orientation in many (but not all) factory suspension engineers toward 'adding more damping' to get tighter transient control when more is not necessarily better. I've seen this for years with our elegant, non-active controlled FCM Elite suspensions. By focusing your DESIGN on maximum grip, maximum road-holding, maximum comfort, you get the LUCKY outcome of having a very well-handling, responsive, confidence-inspiring vehicle. Again, read Sean's comments to see how my assessment here is totally justified as I did not focus on handling in his case but on getting the most grip from the tires given the rest of the components (springs, sway bars, ride height, alignment) remained the same as before. I do speak about this at length in the 'Playing with Knobs' video which totally relates to electronic suspensions in that the computer is 'playing with' various knobs that may or may not be delivering an optimal ride - for a microsecond!

If you argue "well other companies are including similar technologies so we need an edge" I understand that position too. But, there is another way to go about this instead of having the complexity and repair cost associated with electronically-controlled damping and air-bag-equipped suspensions - follow a design path where you absolutely optimize (at least within 90%) the potential of the suspension without resorting to electronic control. This is what we've done with our FCM Elite tuning methods (examining the optimal amounts of compression and rebound damping needed for a given application), the innovative use of high-frequency piston modifications such as our Ripple Reducer technology, and our patent-pending Kerb Blow-Off (KBO) system for delivering both more steering response and softer impact on sharp-edge road features. With these elements, we have enough available to challenge the very best factory suspensions! And if we 'lose' in a comparison test, I'd ask that the test be repeated at 10,000, then 50,000, then 100,000 miles (and we will keep innovating in the meantime!).

Frankly, I am very hesitant to recommend the purchase of any vehicle with a semi-active suspension (or even airbag suspension) to a friend, family member, or customers if someone asked "what vehicle should I buy?" I am leery of new technology that hasn't been rigorously proven or doesn't have a solid warranty. The more complexity the more likely something can fail. From having experience this and learned from racers every done to maintain simplicity creates a more solid, durable, dependable product. Just because you don't race doesn't mean you can suddenly "tolerate" intricacy in your daily-driven vehicle that may see 100,000 or more miles in its lifetime. For a novelty or specialty vehicle, sure, get all the bells and whistles you want! But don't expect it to last or to be cheap if/when it breaks. As this Maserati owner found, an electronically-controlled suspension can lead to 'expensive-sounding' lights on your dashboard. Even if the problem is just an old battery, imagine this happening on a long road-trip, or in the middle of winter on wet, snowy, or icy roads? Is that a chance you really want to take? (Click here on image 1, image 2, and image 3 for screencaps I took from that Masterati Life forum post).

As another example, there's an FCM Elite customer of ours, Greg W. in Los Angeles. He has an S4 Avant wagon that he later had an airbag system installed on along with Ohlins monotube 'race-type' dampers. The airbag system did not integrate very well with the 'race dampers' as there were clearance problems unknown until the whole system was on the vehicle. The airbag pneumatics and electronics had problems. Three of the for Ohlins dampers began leaking within the first year and the ride quality was not all that impressive (I could see why later when I reviewed the dyn graphs he sent me).

The whole situation caused many headaches for him and his shop. I don't think the problems were anyone's fault per se, but he's dealt with a lot of time not having his vehicle working properly, plus expense that isn't warrantied by either Audi or his shop. This is a cost of time plus money as well as build up of frustration. Even for a system that comes from a larger manufacturer such as GM, the repair or replacement cost of such technology can easily shock a customer especially once the vehicle is out of warranty. He still has the airbag system but at least now his dampers are the FCM Elite Bilstein with KBO and Ripple Reducer, designed to be elegant and effective without requiring fancy accelerometers, expensive throw-away dampers, or costly visits to the dealer.

I couldn't in good conscience recommend any kind of semi-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 one purchase and installed - another level of waste creating more landfill space to satisfy some urge to have the newest bells and whistles without regard for long-term consequences.

We've proven that through keeping it simple - designing for efficiency, durability, and harmony - we also get the best road-holding. We demonstrate that our suspension has better grip and better ride quality than the factory C5 Z06 suspension which was lauded as being exceptionally well-tuned on a rough road course (the Nurburgring in Germany). We did this without our KBO technology which I also know is another technological advantage over standard digressive or linear pistons which are common through the automobile industry. I would be very interested in a back-to-back test of all our best FCM Elite technology and tuning methods against 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 their dampers - but I can still dream big!

If you want to experience this kind of Ride Harmony, let's get started! Submit your Consult Payment and Project Form.