Vette suspension in nova

[mfain]

A couple of random thoughts on C4 IRS for your project. The C4 IRS "batwing" is easy to install in most chassis, but even the Dana 44 is fairly weak if you are going to abuse it (especially drag racing with big tires). Also, Chevrolet designed the suspension to impart a little "roll steer" into the geometry to "tighten" the car in hard turns to keep the back end from coming around -- a safety thing. That is partially why the links are so short (space in the C4 Corvette is the other). Also, you have a "loaded" half shaft that serves as a suspension link which is not especially desirable. That being said, a couple of advantages to the C4 set-up are that you can easily adjust the rear moment center and the camber gain for cornering and, if you make the four link front pick-up points adjustable, you can change the "hit" on the rear tire for drag racing and the squat/dive characteristics for road racing. You can't do either of these with a C5/C6 set-up without moving the rear control arm pick-up points. I solved the "weak differential" problem by going to a Tom's Differential C3 Corvette center section (12 bolt ring gear, 31-spine hardened stub axles, big spiders and side gears) on a custom built rear crossmember. There are also Ford 9 inch IRS center sections available. The Driveshaft Shop (and others) build extremely strong, custom length half shafts with 1350 u-joints. Tom's Differential sells cryo-hardened outer axles. I use 20-inch long forward links with heims and adjustable forward mounts that eliminate the roll steer. It takes a lot of work to make the C4 IRS live and perform well behind a big motor, but it is an option. I guess it just depends on how you are going to drive your car. Good luck with your project!

[deuce_454]

Originally Posted by mfain

A couple of random thoughts on C4 IRS for your project. The C4 IRS "batwing" is easy to install in most chassis, but even the Dana 44 is fairly weak if you are going to abuse it (especially drag racing with big tires). Also, Chevrolet designed the suspension to impart a little "roll steer" into the geometry to "tighten" the car in hard turns to keep the back end from coming around -- a safety thing. That is partially why the links are so short (space in the C4 Corvette is the other). Also, you have a "loaded" half shaft that serves as a suspension link which is not especially desirable. That being said, a couple of advantages to the C4 set-up are that you can easily adjust the rear moment center and the camber gain for cornering and, if you make the four link front pick-up points adjustable, you can change the "hit" on the rear tire for drag racing and the squat/dive characteristics for road racing. You can't do either of these with a C5/C6 set-up without moving the rear control arm pick-up points. I solved the "weak differential" problem by going to a Tom's Differential C3 Corvette center section (12 bolt ring gear, 31-spine hardened stub axles, big spiders and side gears) on a custom built rear crossmember. There are also Ford 9 inch IRS center sections available. The Driveshaft Shop (and others) build extremely strong, custom length half shafts with 1350 u-joints. Tom's Differential sells cryo-hardened outer axles. I use 20-inch long forward links with heims and adjustable forward mounts that eliminate the roll steer. It takes a lot of work to make the C4 IRS live and perform well behind a big motor, but it is an option. I guess it just depends on how you are going to drive your car. Good luck with your project!

Those thoughts dont seem that random at all.. ive been researching IRS options for my 35 ford lately and have come to almost the same comclusions..

one of the very big plusses on the C4 is that since the half shaft serve as the UCA it wont require butchering the rear of the car to get it in there as would a c5/6

i dont agree that moving the trailingarms will affect the hit of the car like moving the arem on a 4 link.. and the reason fro this is that the trailing arms mount to the uprights and they do not absorb any of the forces involved in turning the wheels.. that reaction is handled by the longitudinal arm mounted to the diff case... the trailing arms only handle thrust from the wheels on acceleration and enginebraking, and the rotational forces excerted when applying the brakes..

all that being said, it isnt that bad a setup.. and it will polish nicely too :-)

If you want best handling from your c4, you will need to replace a lot or the rubber bushings with heims (as do gullstrand) to heep the bushing flex from changing the geometry in the turns...

im sure that a well engineered 3 link with a wattslink will be a more favorable setup for a car that sees occational drag racing.. if on the other hand you road race with roling start, you can't beat an irs.. the lower unsprung weight just keeps the tires planted more consistently...

[mfain]

[QUOTE=deuce_454;269182]

i dont agree that moving the trailingarms will affect the hit of the car like moving the arem on a 4 link.. and the reason fro this is that the trailing arms mount to the uprights and they do not absorb any of the forces involved in turning the wheels.. that reaction is handled by the longitudinal arm mounted to the diff case... the trailing arms only handle thrust from the wheels on acceleration and enginebraking, and the rotational forces excerted when applying the brakes..

I do agree that you don't alter the tire loading effects caused by the rotational forces of the rear end by moving the front of the IRS 4-link, but you do change the instant center of the rear suspension. This alters the percentage of loading caused by mass of the vehicle on the rear tires during acceleration. Some circle track cars use this principle (moving the 4-link pick-up) to load the outside rear tire during acceleration. Most use a full floating rear end which, in effect, stops the rotational forces from transfering through the four link, much like an IRS.

Pappy

[deuce_454]

[QUOTE=mfain;269225]

Originally Posted by deuce_454

i dont agree that moving the trailingarms will affect the hit of the car like moving the arem on a 4 link.. and the reason fro this is that the trailing arms mount to the uprights and they do not absorb any of the forces involved in turning the wheels.. that reaction is handled by the longitudinal arm mounted to the diff case... the trailing arms only handle thrust from the wheels on acceleration and enginebraking, and the rotational forces excerted when applying the brakes..

Originally Posted by deuce_454

I do agree that you don't alter the tire loading effects caused by the rotational forces of the rear end by moving the front of the IRS 4-link, but you do change the instant center of the rear suspension. This alters the percentage of loading caused by mass of the vehicle on the rear tires during acceleration. Some circle track cars use this principle (moving the 4-link pick-up) to load the outside rear tire during acceleration. Most use a full floating rear end which, in effect, stops the rotational forces from transfering through the four link, much like an IRS.

Pappy

exactly.. so its only the "lift" caused by "pushing" on a non horizontal pair of links.... so the antisquat effect is caused by the thrust acting over or under the C or G..

[Sartren]

Well I'm only in the thought process of my build right now so I'll proly change my mind several times.

[novanutcase]

Originally Posted by Sartren

Well I'm only in the thought process of my build right now so I'll proly change my mind several times.

If you need a point of reference go here:

http://www.stevesnovasite.com/forums...64#post1299964

Jasons already grafted a C4 front end onto his '63.....

John

[Garage Dog 65]

Recently used this setup on a 58 vette with C4 rear transplant. Very easy to install. Didn't cost much either. Tray Walden is owner.

http://www.streetshopinc.com/c4str8axl.html