Are changes in sway bars and bushings worth the effort?

[LlanoBill]

I would like to quantify the improvement in handling I can expect from changing my sway bars to 30/26 mm and replacing bushings with new polyurethane on most applications in the front suspension and the rear control arms and rear spring cushions. Car is 96 LT4 coupe with 90k. What are your thoughts?

Also, is anyone using GS calipers with saw tooth wheels? Thanks! :confused

 

[MBDiagMan]

On most production cars, there are drastic improvements to be had in the area of sway bars especially, but also shocks and springs.

In the case of the Vette, however, the handling, even in the standard suspension cars is already EXTREMELY good, so unless you are planning on competition, the improvements will be unnecessary IMHO.

That said, if you have bad shocks or other components that are worn out or loose, they should, of course, be taken care of.

Good luck,

 

[froggy47]

I would like to quantify the improvement in handling I can expect from changing my sway bars to 30/26 mm and replacing bushings with new polyurethane on most applications in the front suspension and the rear control arms and rear spring cushions. Car is 96 LT4 coupe with 90k. What are your thoughts?

Also, is anyone using GS calipers with saw tooth wheels? Thanks! :confused

I did mine & it's better. I autox it mostly. Would not bother for a cruiser. You should have new shocks at 90k also. And probably wheel bearings & maybe ball joints. Depends on how hard the car has been driven.

No sure on the calipers, I think you would be ok as GS calipers are functionally the same as the regular, they just have the Corvette LOGO on them. They would not show much with sawblades, why would you bother?

 

[Chris Kennedy]

Generally, when you start fooling with springs and sway bars, for every "improvement" advertised there will be some side effect that you won't expect and won't like (for example, there is a lot of propoganda out there about poly bushings---most of the time poly bushings will squeak and don't improve performance on the street and can sometimes make it worse if you have bad roads in your area. So, your car rides and handles worse and sounds bad, too). Unless you plan to use your car for mostly track work, stay with the standard set-up you have----the engineers got the C4 dialed in very nicely. Use the money saved to keep the basics in good shape (e.g., shocks, ball joints, etc.) and to make repairs when needed.

/s/ Chris Kennedy

 

[96vetteLT4]

I just put a rear 26 mm on mine with poly bushings and a noticably improvement was noted right off of the bat. There is no more body roll and the car feels much tighter. According to Richard Newton (appears regular in Corvette Fever and written various books)this was the hot setup prefered by GM race teams for the C4. Poly bushings will not squeak if put on properly. Rubber bushings will wear out. If you only want to do the replacement once than I would go with poly, it will not wear out,and perform better. Just my opinion

 

[Edmond]

Basically, what Chris said is that some things may throw the balance off. The car was R&D'd with the rubber bushings in mind. When you put poly on there, it changes the balance of the car.

Most C4's are well capable of .9 G's lateral acceleration. That is still beyond a lot of modern cars.

But I found that most places aren't even selling the rubber bushings anymore. It may sound crazy but it might be cheaper to buy a full set of poly. I have not seen a full set with rubber but that doesn't mean it's not out there.

 

[Chris Kennedy]

Well, something that you can try as a good compromise (short of swapping out new bars and springs) is to use poly bushings on the EXISTING sway bars---this assumes that poly bushings weren't already used by the factory on the sway bars (my old IROC had these). What that will do is allow you to effectively have a larger anti-roll bar rate, since you won't get the deflection of rubber bushings. It's also relatively easy and cheap to do, and if you don't like it you can undo it easily. The concern I have is that the aftermarket makes all sorts of wonderful promises, and frequently when you try these you really don't like the changes but are too embarrassed to admit it. So, you end up buying something else to fix the new problem. This can all be really expensive and frustrating, especially since the C4 had such a well sorted out suspension to begin with. I would also experiment with different tires, tire pressures and shocks----again, you can do a lot of tuning with these components without major changes to the underlying suspension.

/s/ Chris Kennedy

 

[LlanoBill]

Thanks for all the response. I am not going to change springs or spring weight. What I want to improve is body roll. It appears from the suspension chart on this site, that the Z07 cars came from factory with 30/26 and I have ridden in a Z07 car with noticeably less roll than my coupe. The poly bushings are the easiest to acquire and while the car is apart for other part replacement appears to be a good time to do it all. The GS calipers, together with new 13” rotors, are for improved braking.

 

[tigmaned]

bill
check out www.p-s-t.com polygraphite bushings. they don't squeak, and last longer and don't deflect under driving condtions. i did the whole set on my C3 about 5 years ago and it made a world of diff in the drive!! i will be getting them for my C4 real soon!!

 

[LlanoBill]

bill
check out www.p-s-t.com polygraphite bushings. they don't squeak, and last longer and don't deflect under driving condtions. i did the whole set on my C3 about 5 years ago and it made a world of diff in the drive!! i will be getting them for my C4 real soon!!

Thanks tigmaned! Just went to their site, ordered the polygraphite front end kit. Price is comp to Eklers, better than a few others and the graphite impragnated bushings sound great.

 

[LlanoBill]

Forgot to say some genius of a previous owner had retro fitted 12 inch rotors and single piston calipers. So, in my case the GS calipers and 13 rotors really will provide better braking. :ugh

 

[Mart]

As one who has switched from rubber to Poly, done right, they DO NOT SQUEAK, They are quiet, and man do they handle, Most of us bought C4's because they are cheaper and they handle great, not because they are a smooth ride and quiet.

I love them on mine.

I have found that alot of guys are quoteing others who have not installed or used them.

Mart

 

[aboatguy]

As one who has switched from rubber to Poly, done right, they DO NOT SQUEAK, They are quiet, and man do they handle, Most of us bought C4's because they are cheaper and they handle great, not because they are a smooth ride and quiet.

I love them on mine.

I have found that alot of guys are quoteing others who have not installed or used them.

Mart

I AGREE!

My poly bushings have been quiet. I did the entire rear suspension last January and the front last March.

Mike

 

[WhalePirot]

I believe you'll like the poly

Llano, You seem 'in tune' with how the cars feel, perhaps more so than some other Corvette drivers.

I have had polys on my car for nearly 20 years and do not like Vettes with rubber; the looseness caused me to decline a great deal on a ZR-1 which was stellar, otherwise.

I don't buy the 'balance' stuff at all. Conversely, the poly does not allow the suspension parts to move in the mounts. It keeps the parts where they belong, unlike rubber which deflects during cornering; moreso with bumps during cornering. My car, when 'set' in a corner, stays 'set'. I have the control that the suspension is designed to deliver, not random sloppiness.

My polys are very old and have always needed grease periodically. While they do not squeek, I notice an improvement in cornering transitions afterward sevice. It sounds as though your driving experience would be enhanced with a tighter suspension

I cannot speak to your other questions, but I think you already received some good feedback.

I have found that alot of guys are quoteing others who have not installed or used them.

Irritating, isn't it?

 

[LlanoBill]

Llano, You seem 'in tune' with how the cars feel, perhaps more so than some other Corvette drivers.

WhalePirot, I'm not sure about that, but thanks for the kind words!

I have now replaced all bushings, with the polygraphite mentioned above, except for the rear control arms, which I replaced with NOS parts that came with another brand of poly bushings. Not sure who made these last bushings, but I do get some noise noticable only a slow speed.

Also, replaced ball joints, tie-rod ends front and rear, shocks, 26 mm rear sway bar. Also, 13 inch sloted rotors and GS calipers, rear-wheel bearings and a few other things, all in one fell swoop. Major improvement in a 90K car! I have the 40K convert to compare the rebuilt coupe too and am very happy with the results and highly recommend every thing done to anyone considering spending the money. I love the C4 and consider it more fun than the C5, and yes I have owned a C5. Needless to say I intend to drive the coupe awhile. Thanks to everyone who offered their imput.

 

[MBDiagMan]

Thanks for all the response. I am not going to change springs or spring weight. What I want to improve is body roll. It appears from the suspension chart on this site, that the Z07 cars came from factory with 30/26 and I have ridden in a Z07 car with noticeably less roll than my coupe. The poly bushings are the easiest to acquire and while the car is apart for other part replacement appears to be a good time to do it all. The GS calipers, together with new 13” rotors, are for improved braking.

It is common for folks to start messing with sway bars because they don't like body roll. As far as good, controllable, predictable handling goes, body roll means NOTHING. I have seen people SERIOUSLY screw up a predictable, well handling car by changing sway bars to eliminate body roll.

The most common error is stiffening the front sway bar to eliminate body roll. Stiffening the front bar INCREASES understeer. For the most part the Vette is not an understeering car like most all other production cars. The Vette in stock form is one of the nicest, most balanced and forgiving handling production cars on the planet.

You can certainly stiffen up sway bars and get rid of body roll, but it is HIGHLY likely that when you do you will put some nasty handling characteristics in its place.

What IS important in handling is what the car does when you turn the wheel. It should turn and go where you point it. If the back end comes around too quickly and unpredictably the car is oversteering. If the car ploughs ahead when you turn the wheel instead of turning, it is understeering. These are the things that you need to pay attention to and just FORGET ABOUT body roll.

If you want to know more about setting your car up for good handling, buy a book called How to Make Your Car Handle. It has been in print for 20 or 30 years and is probably the best book out there on the subject. You can probably pick up a used copy on Amazon very cheap.

Good luck,

 

[LlanoBill]

MBDiagMan: Actually, if you’re talking to me, I’ve read that book and agree with you 98%. What I changed was the rear sway bar, going to 26mm from 24mm on a LT4. The 26mm matches what the factory installed on the Grand Sport. I.e., 26 tubular on front, 26 solid on the rear. Under steer is not a problem. Nor is it a problem on factory Z07's, at least the ones I've been in.