ive heard many times that an fd is that much better at handling.

this question is not necessarily putting the fd against the fc or vice versca but i want to learn more about different suspension designs and why is one better than the other.

so comparing the two why is the fds suspension better compared to the fc. this of course is not comparing modded cars lets only talk about stock cars.

technical links on general suspension articles would also be appreciated.

thanks from someone trying to learn about suspension

 

Well, the FC has mcphearson(sp?) struts in front with a multi-link rear suspension. I beleave an FD has double wishbones(both upper and lower control arms) on all four corners, add to that the FDs slightly stiffer more capible chasis, and you have a better handling car.

I've never driven an FD, but my FC has a few basic suspension mods(dampers/springs/bushings) and I'd be really surprised if a stock FD handled better.

 

Do a search on "double wishbone suspension", and that will explain why the FD is superior.


-Ted

 

read: http://auto.howstuffworks.com/car-suspension.htm

 

Well here is an example. the RE Street Fd does like 56.8X on tuskuba raceway, the RE Street Fc does a 58.XX The video of the RE FC was done at 350hp, they did try it at 460ps or whatever it was making and got that time. the RE FD makes like 480 or something.

 

thanks...... but after further research in most race cars multilink is used, so wouldnt that be better than double wishbone? or is this jsut in extreme circumstances for racing whereas a street car would be better off with a double wishbone suspension..

 

bacek if you really want to learn about the different types of suspension and their pros/cons go to the Suspension and Handling Links sticky and think about buying some books.

 

basically to make it simple, an FC suspension will 'flex' and bend where as an FD will almost always stay in proper alignment under heavy cornering.


if your going straight on a public road it really doesnt matter, now does it?

 

That is perfectly true, but (I'm sort of assuming that you are saying this....) car companies certainly do not think that way. These cars were designed to handle well in racing just as well as driving straight on a public road... the FD is just obviously newer technology that seems to work a lot better.

 

I own both an FC and an FD. I have also owned an Fb. which I autocrossed. This is just my opinion.

All three designs are competent. But there is a huge difference in weight of these cars.

The FB is a light car and was very predictable up to the limits of its suspension. After that, things got out of control badly, fast.

The FC was also very predictable and was a significant improvement over the FB in pushing the limits of the suspension envelope. The car was more forgiving at the limits of its suspension travel, in my opinon. It suffered from weight, however. That car is heavy. As the car aged, it lost a lot of its performance, so be careful about side by side comparisons unless the FC suspension has been freshened with new shocks and springs and maybe new bushings.

The FD has the best of both cars, low weight and a better suspension. All things being equal, however, I like the predictability of the FC suspension. If I could lose 600 pounds in the FC, I feel there would be very little difference with the FD until you began upping hoursepower. The FD has some problems controlling the impact of those twin turbos. It can be a tricky affair at best and you had better know how to drive, shift and apply horsepower when you enter a turn at speed or the whole thing will be a very unsettled mess.

 

The above statement is as a very accurate description. The fd handles better than fc but really requires a better driver to get the best out of it IMO.
The fc as stated is very predictable and therefore a better handling car for a less skilled driver IMO.

rgds

 

Well said.

 

Isn't it possible to retrofit a double wishbone suspension onto the FC chassis? What would happen to the FC's suspension potential if that were to occur?

 

I'm sure you could, but cost vs. benefit would make most other suspension mods a far better idea.

 

how so? Isn't the argument "The FD, while heavier, handles better than the FC because of it's double wishbone suspension setup?"

 

Umm...I believe the FC is heavier than the FD.

 

are you aware how much FC's and FD's weigh?

S4 TII ~2,845 lbs
S5 TII ~2,987 lbs
FD R1 ~2800 lbs
FD Touring ~2862 lbs

those are pretty dang close. and if you're talking about a s4 TII, it could actually weigh less than an FD if its a touring. maybe it FEELS heavier?

 

Hmm....if we're talking about N/A cars, the FC weighs even less..

 

yeah...

 

There's absolutely no sense in trying to re-engineer an FC just so you can put a double wishbone suspension under it. If that one quailty is so important to you then don't start with an FC.

There's a hell of a lot more involved than just bolting some links on, especially since the FC structure was designed for the suspension it already has. The pickup points for anything else will be in the wrong places.

 

agree'd. If you want a better suspension just buy coilovers or shocks and springs. If you want a double-wishbone suspension just buy an FD and get it over with.

 

Since I'm here to learn, and this topic is very widely discussed, why, specifically, is it a poor idea, besides cost, to engineer a double-wishbone suspension for the FC? Coming from Ted's site, it seemed to be a good idea, but there really weren't any specifics given. Nor was there any specific information given in your response, besides "There's a hell of a lot more involved than just bolting some links on."

From my understanding, when you develop a body, you're supposed to tune a suspension to properly, well, suspend the mass of a car and keep the wheels and the body moving independently. Isn't a suspension just a type of spring, damper and other force-adjusting bars? Does it really matter what type of suspension it is? All suspensions work towards the same goal, some are just more effiencient at that than others. I just never knew that certain bodies needed specific types of suspensions.

 

how accurate are those numbers posted by jacob on weight? ive always heard that the fd weighs less than the fc..

 

Absolutely they do. The modern car is a unibody and the chassis structure is designed to have the forces input into it at specific places and distribute them through the structure. The design of the chassis is absolutely hand in hand with the type of suspension.

For instance the FC has a strut front suspension. This means there is one locating member at the bottom (an a-arm) that ties into the bottom of the chassis and the sole upper locating member is the strut that ties into the strut tower. If you just want to bolt on a double wishbone suspension there is no where to mount the top wishbone on the structure because it was not designed with that in mind.

Sure some monkey could just weld some brackets on but it would not be structurally efficient and at minimum would require new upper and lower arms, a different upright and quite possibly different steering geometry. You would have just re-engineered the entire front of the car and that is pointless because in the end it's no longer an FC; it's some bastardized product. It would make much more sense to start with a structure that is optimized for what you want to do suspension wise.


It's not that simple. Suspensions have many purposes. They locate the tires in space, they input the load of the tire to the chassis, they orient the tire to the road, they isolate the occupants from bumps, they meet some specific price point in manufacture, they control chassis movement etc. With mass produced production cars the limiting factor is usually ride quality and performance vs. cost.

There are many ways to skin a cat but if outright tire performance is the goal of the suspension you'll find that every purpose built racecar uses unequal length double wishbones at front and rear except where limited by the rules (NASCAR, TransAm etc). Strut type suspensions are cheaper because they use fewer components and are easier to build, but they have poorer grip performance than a proper double wishbone design. Mostly this is due to the fact that a strut suspension cannot introduce camber gain through its motion. OTOH there are many cars with strut suspensions at one or both ends that handle very well. It takes more to build a well handling car than just bolting on some parts.

 

Actually it depends on the model some fd's weigh less than a fc, some the same and some heavier.