I'd love continued input from the group: I took the first step and ordered new bushing sets front and rear from www.superformance.co.uk. I also spoke with Rob at deltavee and plan to rebuild the shocks and swap to new springs. After a bit of soul searching I realized that - despite my longings for track time - the 355 will remain primarily a road car. So I did the standard bushing set, and I plan on a spring and damper setup that retains the current road comfort but will be a bit more aggressive in sport mode. The springs will be stiffer than stock. I will wait until the weather really gets crappy to put it up on the lift, anticipating a long but not-rushed project. Thinking about stiffer anti-sways? Yes/No? My biggest complaint on-track was body roll, but with stiffer springs I am not sure I need stiffer bars. Philosophically I think of anti-sways as a band aid. Rob had mentioned considering adjustable drop links but I think the Superformance kit includes new ones so I am unlikely to do that. I'll revive this with some pics as I go.
Did you determine that your bushings were worn? At a cost of over $1k for the parts alone, it's not something I'd do just in case. Which springs are you considering? Superformance lists a front Fiorano Handling Pack spring, but nothing for the rear. Regarding anti-sway bars, your stated objective is to reduce body roll, but you want spring/damper rates that are still comfortable. I think stiffer bars are exactly what you need. What is the reasoning behind adjustable drop links? Are you planning to corner balance?
I determined that I wanted to pull the suspension apart and replace springs and shocks, and as the car is 15 years old, it makes no sense to leave the original bushings in place. You are correct, parts are about $1200 for all four corners and sway bar mounts. I decided to rebuild and revalve the shocks through www.deltavee.com. The springs are also from them. They will be stiffer and the shocks will be valved to match. I am only getting bushings from Superformance. If I am doubling the spring rate, then I will greatly reduce body roll without touching the sway bars. The revalved dampers will keep things comfy. I have never liked a setup that is under-sprung and over-damped, especially with medium level dampers - it just doesn't work. And then you slap on stiff sway bars to reduce roll, but stiff sways compromise the independence and reaction of the suspension at each corner. I much prefer proper springs, well valved dampers, and light on the anti-sways. That being said, I don't know how much stiffer the fiorano bars are compared to stock and compared to challenge spec. I will absolutely corner balance. I will also lower the front some but that is going to be a compromise too. I don't want the front scraping on every drive way or bump. But right now I have the standard American ride height with the nose in the air to meet some old bumper regulation. I'll go more to the euro spec ride height. The adjustable drop links are to be sure there is no pre-load on the sways when you set them up and that they are as close to level as possible. Rob at deltavee said I would find the standard drop links will have some pre-load. I am not quite sure how all this works but that's part of the project, the learning thing.
Perhaps you need a lesson in suspension geometries:: Do you even know WHY anti-roll bars are needed? Anti-roll bars are needed because the wheelbase is longer than the track. If the wheelbase was equal to the track there would be no need for anti-roll bars! The anti-roll bars, in essence, make the car stiffer in roll so that the roll moment is equal to the pitch moment. {Moment in a physics and calculus meaning.} So, when you double the spring rate, you also need to double the anti-roll bars to achieve the same overall balance from to rear (i.e. oversteer versus understeer.) Yes, you can compensate a little by diddling with the roll centers (raising or lowering the rear) but it is much easier to find the O/U balance when starting from something close to what the Factory built. So, if you were raising the spring rate by 25%-40% you might be able to get away with the stock anti-roll bars. At 2X you have little chance unless you also plan on different tire widths. And at this point I could not tell you if yo need more on the front or the rear. This sounds like you ride heights are not correct! Perhaps a ride hieght and corner weighting is in order. Unlike cars like a Corvette which are almost imune to ride height adjustments, the F355 is very sensitive to ride height adjustments. While I agree that the ride is a little under sprung, but it is almost perfectly damped at speeds over 60 MPH. Something someone with 5000 race track miles on my F355 would have time to recognize. The chassis is fairly insensitive to front ride height, but very sensitive to rear ride height.
Mitch, Definitely agree with your points but please be aware that J. Salmon is extremely familiar with suspension theory and use.
So you're going with Rob's monoball upper mounts that work with standard 2.5" springs? Those eliminate the rubber bushing. Curious because you chose to stick with rubber for the wishbone bushings. The Fiorano bars are challenge spec (same part numbers). Don't know the rates either, but diameter reportedly is up by 2 mm (22 to 24 mm front, 17 to 19 mm rear). There's no indication of that in the workshop manual, it lists a single ground clearance. Do you have any additional info? Right, as you plan on corner balancing, you'll end up with asymmetric ride heights. That will cause said pre-load (beyond any that might already be there for other reasons).
Why my good man, that is why I am here! (reduced condescension is preferred...) I thought I did... Well I admit this is not what I think of when I think of anti-rolls. In fact, no, it doesn't make any sense to me why a short wheelbase would mean you would not want to limit roll. I am not saying you are not right, but I'll need a better explanation. In my small mind, anti-roll bars limit side to side roll by physically connecting the springs on the respective axle. This is why I say that they limit the independence of the suspension: with no anti-sway, each corner moves without any connection to the other. The anti-sway means to compress the left suspension, I now have to compress the right suspension to some degree, depending on the stiffness of the bar. It lessens roll by increasing the effective spring rate on one wheel when the other wheel is not being compressed, such as in cornering. The downside is that it increases the spring rate when you hit a bump with only one wheel, like a pothole. It has absolutely no effect if you hit a bump with both wheels at the same time, like a pavement seam. Hmm. This certainly may be a target, but I guess I have never thought of that as being the primary goal. I wonder why they don't call them roll-pitch balance bars? OK, this is something I have never heard, and it's going to take me a LOT to buy into this. A 2x stiffer spring with the same load will compress less and need less assistance to resist roll, all on it's own. The last thing I would want is to ask for even more help from the other side. Now you are talking BALANCE front to rear, and I agree 100% that this is essential. Throwing on different spring rates (say relatively stiffer in the rear than the front as compared to stock) will change the balance of the car in corner (in this case more oversteer) Though I think it might be easy to say if you 2x everything the balance will be the same as stock (just without your fillings, although I don't have any, my father was a dentist) I don't think that's the right approach. I would prefer to stiffen the springs and then - if need be - stiffen one of the bars to achieve the desired balance. And this is really where I was asking about sway bars. I admit I am counting on Rob at deltavee to have a good idea on how everything is going to come together, as he is providing me with spring and valving rates knowing what I am doing and how the car is being used. He also has recommended ride height and alignment specs to go with it, and he is backed by a long line of experience in these cars (and satisfied customers). I should probably ask him this question... I said the ride height and corner balance are going to be changed. I prefer a stiffer sprung car than the feel of the dampers doing the work. Personal preference. As it is to be primarily a road car, I fear most of it's driving will be at road legal speeds. That's GREAT! Have a cookie. (you asked for that ) What about rake? I would think the aero wouldn't matter at road speeds, but mine measures just about flat front to rear if you are just considering the undertray. It will have rake to it when we are done. The rear ride height will not change much, the front will drop, probably 3/4 inch. I don't want the nose too low, it's a PITA in the real world.
I think I am going to do the monoball upper mounts, but I can't say that I have a real good reason except that the stock rubber is old and probably needs to be replaced and as you mentioned these allow more spring options. I chose the rubber bushings because it's going to be a road car. New rubber should be better than 15 year old rubber. I waffled for a bit. I admit I saw a Bradon post where they used them and decided they couldn't be all bad. And it's too late to turn back as they are on the way! Thanks for the sway info. Still undecided on changing them. I may get it set up and see how it does before deciding. I could go with one or the other if the balance isn't right. I am going to measure current corner weights and ride height before I start. In my opinion, corner balancing a road car is not nearly so precise as a race car. There is so much variation in what the loads are (passenger, luggage, etc) and there is so much give and take in the bushings that chasing stored energy in the suspension can be fruitless. I think I am just going to see how it goes and may make some compromises depending.
On the subject of sway bars, I have a (hopefully relevant) question. Imagine the case where a car is going through a hard right hand turn. The right hand suspension is now unloaded, causing the sway bar to simulate a much stiffer spring on the left hand side (lets say it doubles the spring rate, for this example). Now, still in the middle of this right hand turn, the left front wheel hits a 2cm high bump. The left side now has suspension with twice the spring rate, but the original rate of damping. Seems like the now-higher spring rate would overwhelm the damping. Mitch, do you (or anyone) know how or if that is compensated for? Do suspension designers over-damp a little in anticipation of this?
Paul, to me damper science is almost voodoo. I only know that the more expensive shocks have different circuits for high and low speed compression and rebound damping, and I thought some were position sensitive; the newer gen magnetorheologic jobs can be programmed to do all kinds of stuff. For the rest of us, I think it is just striking a balance. The situation you describe is one reason I think the suspension should be designed to minimize roll bar stiffness. Most of my experience comes from mountain biking; I do think you can learn a lot about how a shock works if you spend a lot of time on a mountain bike...
Mitch, you got a reference for this? I am looking and looking and can't seem to find this concept anywhere.
Yes, you understand what the books say about anti-roll bars. But consider why:: Consider driving down the straight at top speed. Now you feed in the brakes to reduce speed to make the upcomming corner. Braking causes the front end to compress, probably about 2 inches at max braking with street tires. If you set up the anti-roll bars so that the outside front tire and the inside rear tire do not change their compression/extension as you convert linear deceleration into lateral acceleration, you will achieve maximal grip from the tires during this transition. And while at maximum lateral acceleratioin, the outside suspension will be compressed the same 2 inches that the fronts were compressed durring braking. Thus the outside front tire does not change its compression from braking to cornering, and the tire stays firmly planted on the road. Similarly the inside rear tire does not change is extension and stays as firmly on the road as possible. The same thing happens as you dial in power and accelerate out of the turn as the rear squats and the front rises. In order that the opposite corner tires don't move while making these transistion, the longitudinal and lateral springing moments have to be the same!
Those are good reasons. Of course you could instead replace the standard upper mounts for less and there are a few spring options specifically designed for the 355. Most popular seems to be H&R, but they're only about 40% stiffer I believe. I say "only" because you want 100% stiffer (plus H&R is progressively wound and the 40% increase probably refers to their max rate). The standard suspension is softer in the front than in the rear, which is very apparent when driving. The challenge suspension in contrast employs much stiffer springs front than rear. Probably to stay off the front bump stops to avoid understeer, but that's just a guess. The Fiorano Handling Pack as best as I can tell only changes the front spring, presumably to one that's stiffer than rear, like the Challenge approach. You have decided to take the H&R approach by increasing the standard spring rates proportionately, leaving the rear stiffer than the front. I don't know which works better, but perhaps you'd like to discuss how you determined your new spring rates.
Just noticed that Superformance offers not one but two rubber options, standard and hard. Which one did you order and how did you choose?
J.. I'm curious, did you consider utilizing the Teflon-impregnated polyurethane bushing from, e.g., Energy Suspensions instead of the rubber? In general, I've heard very good things regarding these products. In addition, have you considered using the Fiorano Haneling package steering rack with a faster ratio and different power steering pump; along with the shock ECU? Best of luck with your project. I envy you.
You make good points and I'll have to have a look when I get things up on the lift (hopefully later today, but it's Turkey day, so we will have to see how that plan works out...) I determined my spring rates by talking to Rob at deltavee and letting him pick them based on my driving style and wants. Since I have zero experience setting up a 355, I figured I'd let someone with some experience make those choices!
I ordered the standard. (1) because they are going to be like new stock and (2) I saw Bradon using them, and figured they couldn't be all bad.
I did consider harder rubber and polyurethane bushings, but I am a real nut about noises. I was worried either might clunk or make other unwanted sounds. I would LOVE to go to another rack, but I think that is out of my budget and skill set. I'd really love to convert to the early manual rack that I think was available for just a bit in Europe at the introduction of the 355? Still, that's above my pay grade.
I know exactly what you mean. About 3 years ago I had a guy on eBay who wanted to sell me a NIB Challenge/Fiorano PS steering pump for $199.00 inclusive of shipping. Why is hindsight always 20/20?
Isn't that what 90% of people do anyway? Most performance off the shelf spring combos are instantly felt as a positive change but nowhere near double the rates. Can you imagine going from 500lbs springs to 1000lbs? That is a recipe for disaster. I actually drove on such a change and it was lame to say the least. Maybe you can comment on what I did to my 550. It has been several years so i can't remember all the details but I did not like the overly GT feel of the stock 550. So I weighed everything so I could plug into a program a race engineer had for suspensions. I chose close to the upper limit of chassis frequency that a road car should have and chose the the spring rates keeping in mind things like split for anti-porposing and chose my springs thusly. I got lucky or I was smart. I am not sure which, but my car is perfect. It works very nicely on track and still it is streetable. Minor tweeks for O/U with rake, alignment etc. If I did anything to it I would experiment and add more bar on both ends. But, we think we want less body roll. The reality for me is that body roll is sometimes a good thing. I want manageable grip. If I am so stiff that the grip breakaway point is a knife-edge I lack the skill to get to that point without going too far and flying off track. I need progressive roll to talk to me within my skill level to drive the car at the limit of my skill. That is something the OP should be thinking about when he makes these changes. Also, I have worked with Rob in the past and will in the future. He has a very good read on people and has been a track driving instructor too so he knows his stuff. The easy way for the OP to do this is just send his stuff to rob and have a conversation with rob about what his goals are and let rob set up the shock/spring combo. I'm sure he would be better off doing that than guessing. Rob is excellent!
You NAILED it. So the track event that started this was an Audi club event the my wife and I went to as her first experience on track. She drove my S4, I took the 355 (I couldn't run my Lola open wheel for obvious reasons.) I was sooo nervous in the 355. (1) because it's an expensive fix, and (2) because I am just not used to the feel of it at the limit, and I didn't find the communication with the car reassuring. Even though there is no comparison to the speed that my Lola will rotate, it's the unfamiliarity of the limits of the 355 and my fear of exceeding them just made me a bit of a nervous Nelly. So I took the S4 out for fun, and absolutely loved it. Because unlike the 355, the S4 was easy to drive on and beyond the ragged edge. Which would make you ask, then why would you tighten it up, where things are going to happen even faster? I found the body roll and feel of the car to be a little vague, and I think that was part of the problem. It wasn't that I was afraid the rear was going to step out, it was that I wasn't sure I was going to feel what was happening and be able to react. I am used to a car that will tell me everything that is happening and do exactly what I want it to, and I am hoping to get more sensation and feedback through the chassis with these changes. Again, you nailed it.
Love the thread. Started the same process myself. Picked up challenge shocks rather than the revalve. Also ordering the challenge bars from Superformance.
