74' Vette Boy

I am in the process of restoring my 1974 Corvette and just finished reassembling the rear suspension last weekend. I originally bought an Addco 1-1/8" sway bar with poly bushings for the front (which is currently installed) and an Addco 7/8" bar with poly bushings for the rear. However, when I ordered the sway bars I did not realize the difference in how the Addco rear bar mounted vs the GM since my 74' did not have a sway bar from the factory. Here is the current suspension set up:

Front Suspension:
Moog #5762 Coil Springs (474 lbs)
KYB Gas-A-Just
Addco 1-1/8” Sway Bar, Poly Bushings (Currently)

Rear Suspension:
KYB Gas-A-Just
VBP 360lb (actual rate is closer to 350lb) Monospring, Poly Bushings
Sway Bar???

All the suspension bushings and the differential mount bushing are Energy Suspension Polyurethane

Its a small block car and will be converted from an auto to a 4-speed. It was originally an a/c car, but I am undecided as to whether or not I will be a/c back in as one of the previous owners removed all of the components. What would you guys suggest for a rear sway bar? I am correct that I should go with an OEM style bar as I have read that the aftermarket bars limit the IRS causing sudden oversteer? Thank you

terrys6t8roadster

My 69 SBC with a 330lb rear monoleaf spring got a 5/8 sway bar of the type you are describing, nom OEM. I went with the smaller diameter for the less over steer reason and a softer ride. There are ways of converting your sway bar to OEM style ends using heim joints, the CF members that have done that report good success. T

Alan 71

Hi 74VB
I believe during 70-72 the rear sway bar was 9/16" diameter. It was standard on BB cars and those with the F-41 suspension option.

Later the size was dropped to 7/16" diameter.

This is a 7/16" bar installed with the original links and hardware.
Regards,
Alan

jb78L-82

The 70's SBC C3 cars with the sport suspension like my 78 L-82 came from the factory with 1 1/8 inch front swaybar and a rear GM OEM swaybar of 7/16 inch. You can get the OEM type swaybar from any number of vendors including MidAmerica Parts. The factory Spring ratings for a sport suspended car like my 78 are 550lbs front and 292lbs rear Steel spring-Be advised that a composite spring has very different characteristics from the rear steel spring and the spring rates are not comparable 1:1.

Most vendors recommend a 360 composite rear spring to replace the factory rear 292lbs steel spring for gymkhana cars and 300lbs composite to replace the 192lbs base rear steel spring

jb78L-82

Alan, as usual, appears correct.

The 7/16 rear bar does not show up until 1975. The 70-74 C3's only show a 9/16 rear bar. Look here:

https://www.gmheritagecenter.com/doc...t-Corvette.pdf

The earlier C3's have very light front coils (260 lbs) but have the 9/16 rear bar and a smaller front bar.

Starting in 1975 the front coils are 295lbs with a 7/8 front sway bar and the 7/16 rear bar with the sport suspension.

OldCarBum

As part of my suspension upgrades I talked with several vendors who all recommended retaining the OEM 9/16" rear sway bar and upgrading to a 1 1/8" front sway bar on my 73 BB for spirited driving on twisting mountain roads.
During my research I found that many aftermarket rear sway bars require the removal of the spare tire and cover, however if you are adding an OEM style rear sway bar it will allow you to keep your spare.
Something else to ask and consider before you go with an aftermarket style versus an OEM style rear sway bar.

ignatz

You must have seen this advice many times if you've researched this here. Do not use anything but the factory sway bar linkage on the trailing arm.

jb78L-82

OldCarBum

I did and that's what I plan on using.

ignatz

Forgive me, I was pretty sure you would know that, I had meant it for the OP as he had mentioned the Addco bars. However I am now guilty of not reading to the end of his post, so it sounds like what he wants is a size recommendation.

There are only so many choices to fit stock. What I have is a 3/4" rear bar and a big fat 1-5/16" hollow front bar and my car feels nicely balanced. I would think a 7/8" bar is way too stiff to go with the 1-1/8" front.

jb78L-82

I have the stock 1 1/8 inch OEM front sway bar (don't know if it is solid or hollow) with an OEM GM style stock type rear 3/4 inch swaybar......car is nicely balanced as well but I do have in the front aluminum heads, aluminum radiator, aluminum water pump, no AC, no AIR pump and hardware, no heavy cast iron exhaust manifolds and a rear composite spring weighing 8lbs....

Pop Chevy

A 7/8 rear bar is way too heavy in my opinion.

OldCarBum

No forgiveness needed.

OldCarBum

I received the same advice from the people I talked with, which was to run a little heavier sway bar in the front and nothing heavier than the OEM style/size for the rear. Their reasoning was the same, it's just not needed and too large in the rear will hurt more than it will help. They all added that if I planned to track my car then run it on the coarse, see how it performs with the OEM, then go heavier only if I need too.

74' Vette Boy

Thank you guys for all of the input! I am going to go with 9/16" bar to start and then if I need to adjust from there I can always go up to a 3/4" OEM style bar from Mid America Motorworks. I really appreciate all of the info. Also thank you jb78L-82 for the link to the GM Heritage Center, that has some really great information!

Dennis Tapp

Has anyone tried not using one at all? If so what effect did you feel?

Dynra Rockets

Every car is different and every person likes a different handling car. For the street I personally like my Corvette to have great transitions and be a little pushy for constant radius corners.

My '69 small block with alum heads/intake/radiator/headers (~125# lighter) is currently set up with 550 front springs with 15/16" front bar and Bilstein HD shocks. The rear is 340# fiberglass spring and alum rear cover (~45# lighter) with some crappy Delco shocks and no rear swaybar. For alignment I run max caster and -1.5 degree camber with toe-in on front and -1 camber and toe-in at rear.

Transitions are awesome and the rear stays planted on my favorite decreasing radius expressway exit ramp.

Dennis Tapp

That is what I was thinking. In all of my racing I never ran a rear bar except on the ground effect cars. Just wondered if street cars were different and had to have one. I always thought the front set the car and the ride came from the rear. I could never afford play cars and race cars. Health forced me out of racing so it is time to play with street projects. All ideas appreciated.

keithinspace

I have not driven mine WITH a rear sway bar, so I can't speak to the difference in feel. But I can say that I do enjoy very spirited driving and my car does not "lean" per-se...I would describe it as "taking a set" when bending into a curve. There is a very distinct line that the car likes to cut in a quick curve, and a very distinct transition that occurs when the weight is transferred while taking a tight s-curve.

There are two things that would shorten the duration of the "set" my car takes:
---getting off the tall *** 70 series tires on 15 inch rims.
---getting more sway bar.

But I would think that the risk of losing the rear would become a little more pronounced with a rear sway bar unless other adjustments are made to mitigate. I will say that it's pretty tough to lose the rear of my car as it is today.

But...I actually like the car rotating a bit, so it becomes a personal preference thing.

In a car this low and light, I would think that the larger sway bar would be complete overkill and probably lead to more undesirable characteristics than benefits.

jb78L-82

I have never driven my 78 L-82 4 speed gymkhana/sport suspended car (OEM 7/16 inch factory rear swaybar) without the rear bar hooked up BUT:

1. ALL factory C3's were designed from the factory to understeer/push near the limit-Think Ralph Nader and the Corvair fiasco..regardless of whether base or sport suspension...just less understeer with the sport suspension.

2. #1 above is a fact^^^ and verified by auto magazine reviews of the C3 during the day. Running no rearbar on the street as the base suspension cars were made will ensure more pronounced understeer when pushed. Adding a bigger front bar like my 78 came from the factory with 1 1/8 inch bar without the rear factory 7/16 inch bar with result in bigger understeer which is why the factory cars came with the 7/16 inch rear swaybar BUT would still understeer moderately at the limit.

3. To dial out the factory push on my 78 gymkhana car, I added a 3/4 inch rear factory endlink swaybar of 3/4 inches and the car is much more planted in the rear and allows the front factory 1 1/8 inch bar to be more effective since the load is more evenly distributed.

4. The BB C3's which are more front end weight biased, ALL came with a bigger rear swaybar of 9/16 versus the SBC C3's of 7/16 for the sport suspended SBC C3's to further mitigate the understeer of the BB C3's

5. Even my 12 Lexus IS350 F Sport and 10C6Z06 understeer from the factory....Solution for both..BIGGER rear bars.

6. On the Lexus, I installed the Lexus/Toyota factory aftermarket F sport sway bars in which the front bar is approximately the same size as the factory bar but is solid versus hollow and a MUCH BIGGER rear solid sway bar. Understeer is further reduced.
After speaking with the C6Z06 guys who actually race their Z06's, I installed the factory ZR1 rear bar (deal of a lifetime-$89 from GM) which is bigger than the factory Z06 rearbar...understeer further reduced!

7. I know of no high performance or most mass market cars today with independent rear suspension that does NOT have a front sway bar with a rear sway bar......there is a reason for this approach AND GM would not have added a factory rear bar on the BB C3's and the Sport SBC C3's for no reason or no positive effect on the handling of the cars.

Hope this helps!