Hi, I want to lower my car a couple of inches and fit variable a height system to lift the car for speed bumps. I made up my mind to get an aircup lift system but I don't know yet if I will mount it on the OEM coilovers or aftermarket ones. First solution is more expensive and more complicate, but is it worth it? Is the 25 years old active suspension really superior to brand new coilovers? (I won't track the car) If not, I have a question about a good choice of springs for new coilovers: what are the spring rates of a stock car? And the one with Fiorano springs? I don't want to drive a car with a very harsh suspension (I have one already and I don't enjoy it) but I know a lowered car need stiffer springs. So what would be the best spring rate to fit on car lowered a couple of inches while keeping it close to OEM comfort? Thanks for your help.
I’ve lowered a dozen cars. You can’t slam a car on springs and have a supple ride. Forget about it. It defies the laws of physics. You’d need to have a dynamic hydrologic suspension like McLaren uses to come close. OR… or you need to stop worrying about what your car looks like on Instagram and focus more on how it drives. That comes with age.
Go thru my fiorano handling package thread and you will find most of your answers there. FHP spring rates are a secret and I prefer to keep it that way .
First of all, the F355 already has coil over shock suspension, and the shocks are electronically controlled. Probably state of the art 1994. You probably knew this. Second, you can lower the car with the suspension already on the car, just dial the shock tower down. {Which, BTW, is how the factory gets the ride heights correct.} Third, you should know that the oversteer/understeer relationship is controlled by the "roll axis inclination" and lowering the car raises the amount of understeer (not a lot but some). The car, at factory ride heights, has 4.2" of ground clearance. If you lower the car by 2" you will have 2.2" of ground clearance. At 1G of lateral acceleration, the car will depress about 2" on the outside of the turn and raise 2" on the inside on the factory springs; taking up ½ of the factory ground clearance, but lowered; this will leave only ¼" of clearance with stock springs. It gets worse (less clearance) if you put stickier tires on the car (and use them to their full traction extent). But, after 20 years of owning my F355, I find the suspension almost perfect both on the road and at the track*. I have not lowered my car and still bang the bottom rather regularly. {Also note: there are expensive parts under the car !!} (*) as long as you stick to street tires (not R-compounds and not slicks).
Mitch, I don't want to screw up the suspension so I'm listening advises from people who know their they stuff like you seem to be. That being said, I really would like to drop the car about 4cm front, and 3cm rear, not for performance (as I won't track the car) but for aesthetical reasons (I hate the big gap between the fenders and tires). I know that a lowered car needs stiffer springs, but I don't want to run the car with Challenge type springs either. I need infos about what are the original spring rates and what spring rates I should use with the coilovers to still get a good suspension and keep some comfort. Could someone help about this? PS: as I said, I could also get a lift fitted on OEM shocks, but it would cost more: does it worth it, or a good new set of coilovers will have the same (or better) performance as a 25 years old active suspension?
That will add oversteer (not a lot but might be enough to catch you off guard.) {I can tell you how much adrenalin is dumped into your blood stream when you enter a turn at 100 MPH and you have to steer away from the turn because the rear end is coming out on you........} There is the WSM (work shop manual) it has about everything you would ever need. But if it is just fender to tire clearance that worries you, why not use taller sidewalls and lower the car so that you still have 4.2" of ground clearance after making the fender to tire clearance where you like ? You typical Corvette comes with about 6" of ground clearance, and people lower them 2" to about where your stock Ferrari already is. I can understand this. But your typical Corvette does not alter its oversteer/understeer relationship with ride height like your Ferrari does. You tune your Corvette suspension with roll bars, you tune your Ferrari with ride height. It is all down to suspension geometry.
the change of the rake, or the general lowering? Because actually the rake is not correct. I guess previous owner raised the front because of our roads. So putting back the car -4cm at front and -3cm rear should put back the car at a more correct rake. I don't want to increase tire size. To kill the 4cm gap at front means having +8cm overall tire diameter. The car will look like a donk Perfect stance! Do you know the spring rate of your Nitron coilovers springs? How hard is the suspension compared to stock? Do you feel a difference between the Nitron and the OEM suspension?
Lowering the front more than the rear. But there is a nonlinear relationship here. Lowering the front by 1 unit is equivalent lowering the rear by 1.6× units. You specified 4cm front and 3cm rear. The effect on the roll axis inclination is 4×1 F by 3×1.6 R = 4 F and 4.8 R for a drop in the roll axis inclination of 0.8 towards the rear. Factory ride height:: measured from a flat and level surface to the center of the rear bolt passing through the chassis side lower A-Arm: Front: 162±3mm Rear 187±3mm You can check if you car has been altered (or sagged over time), and decide to move forward from there. No, you raise the car with 4mm larger tires, then lower it back down 4mm to ride heights as specified above; and the 8cm gap disappears. ½ from the tires and ½ from the lowering. But also note: now that you understand the F-R relationship of 1.6×:: after lowering, if you find the car oversteering, you can raise the front or lower the rear. Conversely, if you find the car understeering, you can lower the front or raise the rear. These adjustments should be done 1mm at a time and are not terribly critical. But if you make such an adjustment and you can't feel the change in the steering wheel or seat of pants, your may not have the acuity to tune the suspension to your driving style. But if you do have the acuity, you can dial in your car so that it suits your driving style--anything from tail-out like an old Porsche 911 or nose-first like a 1960s Cadillac. Really, everything needed to go from a nose-first pig to a tail out drifter is possible without changing any components, just ride height.
Yep just scale it out and she'll take good care of you in those sweepers. Don't forget to check the air in your tires. That's all I care about Image Unavailable, Please Login
Still; to close the 4cm gap, you have to increase tire overall diameter 4cm. Better than the 8 cm I noted previously, but still a lot. Not mentioning the loss of acceleration with such a big wheels. I'd rather keep the wheel size stock and lower the car 4cm. I'll check my car ride height at the points you mentioned but I'm pretty sure the front is higher than it should be. By the way, on the workshop manual I've got, numbers are differents than yours: Image Unavailable, Please Login I'm curious to know those numbers for the Challenge... Otherwise it is good to know you can tune the car just by modifying heights, but this is not what I intend to do right now. Might be usefull later, but now I really need to figure what springs I need (again, I'm not racing, just driving mostly in city, highway and some back roads.) I found some numbers in the manual for stock spring rate: about 4000N front and 4300N rear. Is N for Newtons per millimeter? Now I'm lost when looking aftermarket coilovers with spring rate in K (kg/mm?). N, K, or no unit at all. Not easy to compare springs...
I’m using stock spring rates. It rides smooth, but you can tell the front shock is close to the point of bottoming out. All in all, I’m very happy with the setup. I might upgrade to three ways in the future.
1N = 1Kg×m/s^2 To get to kg/m you will need to multiply by s^2/m^2 -- which makes me think that the N is not Newtons.
I know to use google and saw those results before postig here, thanks I you had read the post you're showing here, you would have find out that it is an estimate from a calculator. Not a factory data (except the graphic with the unit N that nobody else using). So anyone who knows about this? Thank you.
I've attached the page from the Ferrari F355 Challenge Technical Regulations Manual which gives the suggested basic setup data for the F355 Challenge. Please note the chassis height measurements are taken from the center of the inboard lower control arm mount forks. This yields a 19mm positive rake (nose lower than tail). It's best to start with no more than a 15mm positive rake. The car should turn in well with that setting. Another way of measuring ride height is to measure from the floor of the chassis just behind the front tires and just ahead of the rear tires in which case the range will be: Front: 85 – 115mm and Rear: 85 – 115mm Again, this data is for Challenge cars with Challenge shock absorbers with active damping and 2200 lb/in front and 900 lb/in rear Challenge springs... Image Unavailable, Please Login
I don’t believe you’ve actually read it and digested it fit yourself, actually no. You seem to want it chewed up and plated for you. There’s 20+ years of information on this forum but you have to be willing to read it and interpret it. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
So what is it? 180 230 260 360? Retrophit, do you think that posting many different figures with no real sources is helping? Do you think your agressive attitude is helping? If you don't have any knowledge to share, please do something else. I'm sure (and hope) you have better things to do. Thank you.
Again, you seem to want it spelled out. You need to read the contextaround those posts to piece it together. Those rates are for different springs. I’m not trying to be rude or aggressive, trying to let you know why you don’t get answers to your extremely specific questions.
Sure. It figures. And I don't see why it would be an extremely specific question to ask about the stock springs ratings. They're listed in the workshop manual, the only problem seems nobody knows what unit is used. Usually when someone is asking a question, either you know and answer, either you don't then you're not supposed to reply... But I guess that too, comes with age.
Excellent comment Mitch; I also run a stock setup and find that I "bottom out" when driving fast / heard on road imperfections. Unless your roads look like an autobahn or you plan on driving 55mph would leave stock height personally.
It’s not not just potholes, etc. that can cause rubbing/bottoming out on a slammed car, there’s also the minor matter of changing directions at speed
