a-body vs. f-body

**iLIKEtransAMS** · 01-22-2007, 07:05 PM

I want to know wich is the better car in cornering, dragging, etc. the F-body or the A-body?

**9t8z28** · 01-22-2007, 07:57 PM

So you mean a say late 60's A-Body compared to a late 60's Camaro. I would have to say a Camaro. Their lighter. But then again are you gonna go all out and turn it into a drag car. I would still say the Camaro. But IMO, I would love to see the Chevelle cause I gots one!

**JohnnyBs98WS6Rag** · 01-23-2007, 03:25 AM

IMO, the F-bod has always been the better handler due to it's better front suspension geometry. The early (up to '72) A-bod's front suspension was back-asswards for good handling (positive roll center). Although that can be fixed with a tall-spindle conversion or a Global West a-arm kit. As far as drag-strip performance, I don't think anything transfers weight like an A-bod. The 1st & 2nd gen F-bod leaf spring rears sucked for planting the axle and getting traction, AND they would sag like grandma's boobies after some abuse. Also, the full-frame of the A-bods (and G-bods, which replaced the A-bods from '78-'87) made for a stronger chassis. The 3rd and 4th gen F-bod's rear suspension was much improved, but then they put a wimpy 7.5" 10-bolt under there, so advantage lost.

**69Nova355** · 01-23-2007, 04:55 PM

The A body will naturally be heavier than the F body HOWEVER the A body uses a factory 4 link rear whereas the F body uses a leaf spring rear.

Also an A body is a full frame car whereas an F body is a unibody.

Either way I don't think you can go wrong. The A body accepts a big block better IMO. There are people racing A bodies in the 10's with a 454.

**iLIKEtransAMS** · 01-24-2007, 10:32 AM

what is unibody and full chasis?

that's what i was wondering about the weight transfer and lauching with the A-body, does the extra weight even out b/c of the better lauching and weight transfer in drag racing?

what is a four link rear?

thanks guys this is good information, keep it coming

p.s. is the gto an A-body?

Thanks

**JohnnyBs98WS6Rag** · 01-25-2007, 07:19 AM

Originally Posted by iLIKEtransAMS

what is unibody and full chasis?

that's what i was wondering about the weight transfer and lauching with the A-body, does the extra weight even out b/c of the better lauching and weight transfer in drag racing?

what is a four link rear?

thanks guys this is good information, keep it coming

p.s. is the gto an A-body?

Thanks

A "unibody" car has no frame from which the suspension is connected. The suspension is connected directly to the shell of the body, so that the body carries the stress of the weight of the car, passengers and cargo. A "body-on-frame" car has a seperate "rolling chassis" to which the suspension is connected. The body is simply bolted on top of the frame, but the frame carries the loads, not the body shell (although, in reality, the body shell does provide some amount of stiffness to the car and chassis by carrying some of that load). F-bodies are actually kind of a hybrid of these two basic types, where the body carries the load, but the suspension is connected to front and rear "sub frames", which are then bolted (front) or welded (rear) to the body shell.

A 4-link rear refers to how the rear axle is suspended from the frame / chassis. A-bodies use two upper and two lower control arms which allow the axle to swing up and down with the motion of the suspension. Weight of the car is transferred to the axle through coil springs between the frame and rear axle. The forward force from the driven axle is transferred to the frame by the control arms. Also, the twisting force of the axle under acceleration is controled by the upper and lower arms (the lower arms are under compression and keep the bottom of the axle from moving forward, while the upper arms are under tension and keep the top of the axle from moving backwards. Side-to-side motion is controled by the fact that the upper arms are angled and triangulate the axle relative to the body/frame. By playing with the geometry of these control arms, you can optimize how well the rear axle is planted to the ground on take-off.

This is in contrast to the leaf-spring rear setup of the 1st and 2nd gen f-bods, where the axle is connected to the rear subframes / body with leaf springs, which not only carry the weight of the car, but also control the up and down, fore-aft and twisting forces from the axle. Side-to-side motion is controlled by virtue of the flat springs being laterally very stiff. Most leaf-spring rears dampen the twisting forces by having one shock connected to the front side of the axle and the other shock connected to the back side of the axle. About the only way to improve a leaf-spring rear's ability to plant the axle is to add "ladder bars" that limit the twisting of the axle and transfers the forces more directly to the body, lifting the body and pushing the axle down.

The 3rd and 4th gen f-bod rear suspension is different, they use two lower control arms to control fore-aft motion/forces, a panhard bar to control side-to-side motion/forces, a torque arm to control twisting forces and coil springs carry the weight.

Old GTOs, up to '73, are A-bods. The '74 GTO is an X-bod (Nova based). Not sure what the '04+ GTOs are called, but they are entirely different from A-bods and F-bods by virtue of their IRS. I'm pretty sure they are "unibody" cars.

**iLIKEtransAMS** · 01-25-2007, 08:01 PM

thanks

**mullenh** · 01-29-2007, 07:22 PM

while it is true a stock f body is better at handling than a stock a-body that can be fixed.
steering geometry fixed with spindle change and custom upper a-arms.
custom coil overs all the way around.
4 wheel disk brakes.
fast ratio steering (but I want rack and pinion as soon as i can figure what will work without bump steer, and i think i have)
curb weight 3300 lbs
ls1 4l60e
222/226 111lsa
yankss3800

**coolingpro** · 02-01-2007, 04:44 PM

what is bum steer.

**mullenh** · 02-01-2007, 05:54 PM

Originally Posted by coolingpro

what is bum steer.

toe steer is often refered as 'bump steer'. it occurs during a turn and to make it simple one wheel turns more angle than the other. old ford trucks were renowned for it (the geometry was bad). and thanks i missed the 'bum' but fixed it. i can't type and all of the letters are missing off my keyboard (rubbed off)

**JohnnyBs98WS6Rag** · 02-02-2007, 03:52 AM

Originally Posted by mullenh

toe steer is often refered as 'bump steer'. it occurs during a turn and to make it simple one wheel turns more angle than the other. old ford trucks were renowned for it (the geometry was bad). and thanks i missed the 'bum' but fixed it. i can't type and all of the letters are missing off my keyboard (rubbed off)

Not quite. "Bump steer" refers to a toe-in/out change when one wheel goes over a bump while the steering is pointed straight ahead, causing the car to pull to one side when going over a bump, thus the term "bump steer". This is caused when the geometry of the tie-rods and control arms don't form a nice parallelogram in the verticle plane. This should not be confused with "rear axle skip" where, when the car is making a turn and encounters a bump, the tires lose contact with the pavement and the car takes an unexpected "hop" to one side. Solid (live) axle rear drive cars are notorious for this undesireable behavior, which is aggrivated by the higher level of un-sprung mass that is less-so on IRS cars.

What you are referring to is called something else (can't remember OTOMH), but that is needed to make the inside tire turn tighter than the outside tire since, while the car is traveling in a circle, the inside tires are traveling on a shorter turn radius than the outside tire, and this feature reduces tire scrub. ALL vehicles have (need) that.

**Firebirdjones** · 02-02-2007, 08:25 AM

Since I own both a 70 Firebird Formula and a 72 SS 454 chevelle I feel I can give an honest opinion without being biased towards either one.
The question leaves alot on the table. Stock for stock or in modified form it really changes the answer.
I can tell you my 70 Formula is a bone stocker, used to run in the muscle car classes years ago, now I only race it 1-2 times a year and enjoy it as a nice driver most of the time. It weighs 3,890 lbs. with me in it...so it has more than 200 lbs. weight advantage over my chevelle. Being a Formula, it's a Trans Am is disguise, about as good as they get in 1970. It has bigger sway bars, rear bar as well, different springs etc...and was designed overall to be a better handling car right from the get go. Yes it corners well and drives very nice, and has a factory 2.5 turn lock to lock steering box that makes the car feel very responsive. By far it corners better than my 72 Chevelle,,but for good reason.
As far as drag racing, well I always run the car in stock form with stock rubber, so a little finess is required, but it's very capable in that respect and it actually has decent weight transfer.
Is it better than an A body? It's tough to say.

My chevelle, weighs 4,108 lbs. with me in it,,,it's a Super Sport and has the F41 suspension package which is as good as it got in 72,,,but to be honest, the car is big and heavy, the steering box is a little slower, and quite frankly, I wouldn't go slinging this car around corners at speed. The big block up front doesn't help either.
The car was stock when I purchased it over 20 years ago. Now the motor is warmed up a bit, the suspension is very close to stock with only a few tricks done for straight line performance. It does fine at the track, even when it was stock, I had just as much trouble at the starting line as I do in the firebird, but the chevelle never seemed to have as much weight transfer as the bird does,,,which could be due to the heavy boat anchor under the hood,,,lol. With some suspension tricks on the chevelle now,,,it works well enough and gets the job done without sacraficing drivability.
Is it better? Tough to say. Both cars drive nice on the street. Although I was never a cornering kind of person, the ride quality is nice between both cars considering rear suspension designs were totally different between them, they both ride just as nice in my opinion.
As far as modifying either one? Both can be made to corner or drag race just as well as the other. I think what it really comes down to in the end is which body style do you prefer? Larry.

**mullenh** · 02-03-2007, 03:53 PM

Originally Posted by JohnnyBs98WS6Rag

Not quite. "Bump steer" refers to a toe-in/out change when one wheel goes over a bump while the steering is pointed straight ahead, causing the car to pull to one side when going over a bump, thus the term "bump steer". This is caused when the geometry of the tie-rods and control arms don't form a nice parallelogram in the verticle plane. This should not be confused with "rear axle skip" where, when the car is making a turn and encounters a bump, the tires lose contact with the pavement and the car takes an unexpected "hop" to one side. Solid (live) axle rear drive cars are notorious for this undesireable behavior, which is aggrivated by the higher level of un-sprung mass that is less-so on IRS cars.

What you are referring to is called something else (can't remember OTOMH), but that is needed to make the inside tire turn tighter than the outside tire since, while the car is traveling in a circle, the inside tires are traveling on a shorter turn radius than the outside tire, and this feature reduces tire scrub. ALL vehicles have (need) that.

nothing you said was wrong, but we still refer to it as bump steer and not OTOMH when we (not me) set up a car for a custom rack and pinion they measure and the angles height so that the rod ends are in the correct spot. you want both tires on the same camber plane not getting them the correct length and correct height will cause one tire to turn more than the other or have more camber (leans to one side) this causes one tire to drag around the turn and skip or bump. there is a tool used to set this up and it measure the amout the tire moves in relation to the opposite tire. on a race car the tolerance is .008 of one inch.