Combo car; drag and RoadRace

[Caprimaniac]

Yeah, Yeah- completekly hopeless thought. Won't be a winner, but let's say I'm out to have some fun.....

Unibody chassis. McPherson front. Can swap between a set of skinny front leg, even w/o brakes for drag and a set of beefy legs w/ big brakes for the track.

But what about the rears? Could a 3- link w/ Panhard or watts work? Or should I stay With traditional a 4- link?

Tempted going 3- link With a really beefy upper arm. 2" poly bush, 1/2" bolt in the front end and 1" rod end at the rear?

~2100 lbs car w/700 Hp smallblock.

[BCjohnny]

In practical terms, depending on how it's put together, either a three or four link should work and allow tunability of weight transfer (anti-squat) between drag & RR set ups.

Personally I'd go four bar with WL, but I doubt there's much in it ..........

[Edit: I should have said a four bar should allow a more dedicated set up, if you know where you are with it]

[cgarb]

If I were going to attemt something like that, I would build a drag race type 4 link rear suspension and use a heavy duty rear end location device like a watts link or something similar. The standard diagonal link or wishbone locator probably won't hold up to the cornering loads properly. Probably close to the best of both worlds as one could get.

[Brian P]

Parallel links on each side of the car won't give good anti-squat. Orienting the links of what I think of as a "4-link dragrace" suspension with the upper links sloped differently than the lower links in order to give good anti-squat, will bind up the suspension in roll or in one-wheel bump; not what you want in a roadrace car. The traditional production 4-link design with upper diagonal links and lower trailing links does not have desirable toe control in roll.

I would say 3-link with the lower trailing arms close to parallel to the ground and the upper one oriented to give the anti-squat that you want, and with your choice of panhard or Watts. No binding if built correctly; you're not stuck with a too-high roll center; you can have antisquat. The general arrangement would be not a whole lot different from S197 Mustang.

[Matt@RFR]

I'm no suspension guy, but a few years ago I helped put together a 3-Link setup for a startup business. Lateral-Dynamics. They are no longer in business, but the kits were really well received among the old Camaro guys. Primarily marketed as road race style suspensions, I know we had one guy run 9's with typical short sidewall street / road race style tires.

[Caprimaniac]

What I have now is a 4- link. Lower bars runs parallell (longditudinal) and have an angle up to the chassis from the axle, for anti- squat (actually redid the brackets after a couple of years of testing. Using a SLR camera I could see the rearend diving on acc.)

Upper bars are Close to parallell to the gorund, might point slightly uphill, but are at an angle to the axle/ chassis in the longditudal plane; so somewhat diagonal... slightly.

All ends balljointed/ rod ends 5/8".

Panhard parallell to the axle. Height middle of tubing. Size is of rod is ... 1" I Guess.

Cornering : cannot say there's any binding, steering to the extent it has been felt by any driver.

Out of the hole: Runs straight and behaves well. Maybe a bit too easy to spin the tires loose, haven't managed the wheelstand I'd hoped for yet...

It is quite quick on the RR, and un the 10's in the 1/4. But unfortunately a street legal car. Cannot wait to set the cutter in a New body to shape a real race car.

Tha answers in the thread are somewhat divided between the 3 and 4- arm setups.... I'm temted to og With the traditional 4- link. At least I have some experience there. And it will also depend on.... if the Project will be more serious in one of the two directions.

Thanks for all input.

[MadBill]

...I would say 3-link with the lower trailing arms close to parallel to the ground and the upper one oriented to give the anti-squat that you want, and with your choice of panhard or Watts. No binding if built correctly; you're not stuck with a too-high roll center; you can have antisquat. The general arrangement would be not a whole lot different from S197 Mustang.

Ditto, except for the fact that you already have a 4 link. A 3 link doesn't bind in roll and can be offset to cancel some or all of the unloading of the RR tire due to driveshaft torque. Also, contrary to what one might expect, the loads on single upper link are not twice that of each lower, since the accelerative thrust is additive to the axle torque forces on the latter but subtractive for the former.

[SupStk]

I'm far from a suspension guy especially with road race stuff. My option the traditional 4 link will make the rear axle housing act like a huge sway bar. That may render any suspension tuning unresponsive. For RR think I'd consider disconnecting one (left side) of the upper bars. Also like mentioned a panhard bar or watts linkage might be the best of both worlds.

Just a couple cents from a guy who really don't know what he's talking about...