A'PEXi 7

is this kind of suspension a good setup. i understand that it will be all custom. but i would like too knoe more if anyone has the knowledge to share.

here's a pic
http://fc3spro.com/TECH/FM2W/canti.jpg


BTW: this isn't for a street car.

DamonB

Absolutely no reason to do it unless you have absolutely huge rear tires that can't clear the shocks or you wish to make everyone say "wow".

The only advantages that mounting has are the ability to adjust wheel rate characteristics by varying the rocker ratio. Of course you can do this with the stock suspension as well but not quite as simply. There's no real advantage to that mounting other than "wow" factor. Open wheel and other true racecars use it fror packaging and weight placement reasons; a full bodied "sedan" based car has nothing to gain really.

RotaryAXer

iTrader: (4)

It has advantages. Most of which DamonB noted.

The advantages that I can think of a pushrod/inboard shock suspension. (no particular order)

1. Reduce unsprung mass
2. Easier to adjust/tune (ride height, shock rates, spring rates and motion ratio can all be changed without tearing the entire rear end of the car apart)
3. Weight placement in the center of the car and possibly lower than standard (not the case in this picture)

All of these thing take a good and practicable knowledge of vehicle dynamics to get the full usefulness out of the setup. I think maybe that is what DamonB means when he says that it is a WOW factor thing. Most people wont utilize the benefits that take a lot of work to gain. It could be consider very rice if the only reason to do it is to make the car look cool. On a full blown road race car with a vehicle dynamics engineer on the team that is using this tool for its intended purpose it makes sense.

DamonB

Pretty much. IMO the gains vs. cost in this case are so small as to not be worth it on any racecar which is based on a production car chassis. There are far better areas to spend development money. When you're designing from a clean sheet of paper the story is different.

In the case of an FD or FC for instance you wouldn't save any weight and you'd place it higher in the chassis. You'd still have the damper and spring but now you also have a pushrod, bellcrank, fabricated mounts and some sort of reinforced (heavier) floor where the dampers are mounted. Not to mention the mass needed where the bellcranks mount since they now carry the rear weight of the car as well. "Real" racecars are designed as a complex system that build upon intrinsic advantages of each subsystem. Putting pushrods on a production car chassis doesn't really contribute anything to the overall performance of the package; the package wasn't designed to take advantage of it.

A'PEXi 7

wow, thanks for the input. my goal is of course to build suspension package that will compliment the chasis. and i see that the stock setup is already fairly adequate. i was just wondering what was too much or unecessary.

anyways are there any resources that are specific to our cars w/ a focus on chasis and suspension dynamics, or any kind of car for that matter.

DamonB

I don't know anything specific for our cars but I have put together a bunch of sources for info in our Suspension and Handling Links sticky.

Don't fix what isn't broke. IMO too many people have aftermarket-itis and assume anything "new" you can bolt on makes the car better. It doesn't work that way; especially with suspension. You first have to identify the problems or qualities you don't like. Then you have to form a plan that may remedy them. Then you have to implement and test that plan. Obviously this takes some knowledge of what is really going on and how changes will affect different characteristics.

Believe it or not companies who sell parts are in business to make money, not make your car better. Companies are just like people. They all have an opinion but you have to decide for yourself which are valid and which are not. That takes some edjumication

FB332

wow, thats a really good idea

I don't think I'd do it on an FC or an FD, but I'm building an FB and I need some sort of easily adjustable setup for the rear, and since there really isn't any coilover options for first gens, and I think I may have to fab up a stup like this

then I could use pretty much any old racing shocks :]
(mhmm, penske and koni make some pretty nice stuff...)

Black91n/a

If you just fabbed up some eye to eye mounts then you could use those shocks anyway, without the added complexity with pushrods and all that.