63 SWC: Advice on Suspension Changes

[Jason S.]

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[Michael W.]

Re: 63 SWC: Advice on Suspension Changes

In 25 years in the hobby, I know of only two catastrophic failures of composite springs. Both were owner induced, both through ill-conceived modifications that would make Bubba cringe.

Poly bushings are a very bad concept from an engineering point of view particularly in locations where the bushing is required to move in more than one axis. Many owners are finding that the poly bushings do NOT last longer than rubber and realizing that the 30-40-50 year life of the factory bushings wasn't all that bad.

[Patrick H.]

Re: 63 SWC: Advice on Suspension Changes

In 25 years in the hobby, I know of only two catastrophic failures of composite springs. Both were owner induced, both through ill-conceived modifications that would make Bubba cringe.

Poly bushings are a very bad concept from an engineering point of view particularly in locations where the bushing is required to move in more than one axis. Many owners are finding that the poly bushings do NOT last longer than rubber and realizing that the 30-40-50 year life of the factory bushings wasn't all that bad.

I agree with Mike.

For those who have used a composite spring, the failure rate is probably no different than with a metal spring.
Note that if you go this way, you will probably need the longer spring end bolts to be able to properly adjust ride height.

The only two places I would ever use a poly bushing are the rear spring ends and the rear strut rods. Every other location I would only use rubber for the reasons Mike mentions above.

[Patrick B.]

Re: 63 SWC: Advice on Suspension Changes

The F41 suspension is very stiff and you will not like driving the car. I used the F41 rear spring when I drag raced my 70 Corvette to reduce squat and quit breaking U-joints. I was happy to remove it when I was through with racing. You can get Koni adjustable shocks for a 63 vette and adjust them as stiff as you want in rebound and still have a car that is pleasant to drive.

[Jason S.]

Re: 63 SWC: Advice on Suspension Changes

I agree with Mike.

For those who have used a composite spring, the failure rate is probably no different than with a metal spring.
Note that if you go this way, you will probably need the longer spring end bolts to be able to properly adjust ride height.

The only two places I would ever use a poly bushing are the rear spring ends and the rear strut rods. Every other location I would only use rubber for the reasons Mike mentions above.

This all good feedback. Exactly what I've been looking for (and the "good news" is the choice you're recommending is the less expensive one.......not that that was a major consideration). All joking aside, I may consider avoiding all the "rage" about poly bushes based on your feedback.

Given you're an NCRS Vice-Chair, Do you have any insights about my spring/shock dilemmas? Do you know of any people that have used a Z06/F40/F41-spec spring package and regretted it? I'm hearing alot of decent feedback on a "middle-ground" setup that uses 460# front springs and 330# rear composite spring. Keep in mind I'm not wanting to swap just for the sake of a swap - I figured if I'm going to be blowing apart the front/rear suspension to replace bushings and clean everything up anyway.....this is my time to make such a decision. The springs and shocks in the car probably need changing, anyway.

[Patrick H.]

Re: 63 SWC: Advice on Suspension Changes

How are you going to use the car?

If you're not going to track it, and you just want to drive it for fun on the weekends, I would keep it as stock as possible in configuration. I suspect that the other setups would be a lot more firm (rough) riding than you expect. Honestly, if you want a great handling rough riding car buy a cheap C4 for what the new suspension would cost you, beat the $%&^# out of it, and have fun with both. Changing to high quality shocks (Bilstein Sport or QA1 non-adjustable, for example) but staying with what's currently on your car (except new bushings) would probably help you more than anything else, with the other important component being the tires. If your current ride height is OK I would not even consider swapping springs, because no matter what any catalog company tells you, it WILL ride higher with the new components and you'll look like you need 4WD.

New shocks, new tires, stock everything else. That's what I would do, but it's not my car.
Oh, and new liners for the rear spring.

PS I think you'd be wasting your money to put all kinds of $$$ into the suspension and then installing the skinny Coker radial reproductions. But again, that's just my personal observation. Save your money, stay with the components currently on the car, and use all the money you saved to pay for gas.

[Jason S.]

Re: 63 SWC: Advice on Suspension Changes

How are you going to use the car?

If you're not going to track it, and you just want to drive it for fun on the weekends, I would keep it as stock as possible in configuration. I suspect that the other setups would be a lot more firm (rough) riding than you expect. Honestly, if you want a great handling rough riding car buy a cheap C4 for what the new suspension would cost you, beat the $%&^# out of it, and have fun with both. Changing to high quality shocks (Bilstein Sport or QA1 non-adjustable, for example) but staying with what's currently on your car (except new bushings) would probably help you more than anything else, with the other important component being the tires. If your current ride height is OK I would not even consider swapping springs, because no matter what any catalog company tells you, it WILL ride higher with the new components and you'll look like you need 4WD.

New shocks, new tires, stock everything else. That's what I would do, but it's not my car.
Oh, and new liners for the rear spring.

PS I think you'd be wasting your money to put all kinds of $$$ into the suspension and then installing the skinny Coker radial reproductions. But again, that's just my personal observation.

You are correct - it will never be a track car. Just a fun street car. Since you mention tires - I was tempted to put a set of ET Sebring 15" wheels because they look so much like the Halibrand magnesium wheels that GM used on so many of their race cars (57SS, the Stingray racer, '60 Sebring cars, the Grand Sports early on) and go after 15" bias-ply-look radials from either Coker or Diamond Back. Believe it or not - in the days where resto-modding is so popular, I actually want to go back to the 670-15 SKINNY tired original look!

Given the age of the springs and shocks (probably 25-30 years old) and the fact that I was going to go through the suspensions to put new bushings in (they are dry-rotted) and detail things anyway, was the reason why I was going to put springs on the list, too. I figured while I was in there, might as well do it? What I should do is measure the ride height - and double check myself on how "tired" I think my springs really may be. It does appear to be sitting pretty low. Perhaps I should also hang some weights off the bumper and try to calculate what the k-factor in the current springs are to see if they really are as tired as I think.

[Jason S.]

Re: 63 SWC: Advice on Suspension Changes

And to your point - shocks are much easier to swap out than springs if I ever do want to try to make the car more "correct"!.
So as I suspected - the Z06/F40/F41 parts are/were probably only good for "track day" cars even then. I had wondered if they were able to get away with such high spring rates because they also used such small sway bars, and because they were tuning with (relatively) soft bias-ply tires......but what I'm hearing is that despite those factors, the F41 is probably going to not be very pleasurable on the street. Heck - the spring rates are even significantly higher than my 2014 Track-Pack equipped Mustang (and it's a heavier car to boot)!

With all that said - with your input and Mr. Hulst's - it sounds like you both are confirming my suspicion that this is not the way to go - that I'd regret it. Alot of people have been recommending to me what I would call a "middle ground" setup - which is a 460# front (versus 550# F41) and a 330# rear composite spring (versus the F41 steel spring at 300#). It's difficult to compare a "rating" for a linear composite spring to a multi-leaf.....but still I'm concerned that even this may not be what I'm looking for? Again, the only reason I'm considering doing a change is because I'm going i to replace the original tired springs, anyway. Perhaps I shpould just replace stock-with-stock?

[Patrick H.]

Re: 63 SWC: Advice on Suspension Changes

Again, the only reason I'm considering doing a change is because I'm going i to replace the original tired springs, anyway. Perhaps I shpould just replace stock-with-stock?

I would inspect them when you get them out of the car, but if they don't look bad I'd clean them and reinstall them.
I have yet to see a replacement spring, any brand or rating, even stock replacement rated ones, that didn't raise the height of the car. These cars rode moderately low on Day 1.
Go to any NCRS meet or Bloomington and see how many of the restored cars aren't sitting too high. This is really obvious when you compare them to an unrestored example.

Again, if it's not going to be a track car I think you're waaay overthinking it.

I'm going to edit this and add a bit of a story-
One of my other cars is a 1970 Cutlass convertible. After buying it 10+ years ago I never quite liked the way it rode and handled. So, I did what you're thinking about. I replaced all of the ball joints, bushings, steering linkage, you name it. I kept the shocks because they looked brand new. And when I spent all that money I found out afterwards that it rode and drove exactly the same. I could not tell any difference at all.
So, I went ahead and replaced the shocks because it's all there was left to do. Tada! New car. I could not believe the difference.

Here's a silly question - how does the car drive right now?

Oh, and where in Michigan do you live?

[Paul Y.]

Re: 63 SWC: Advice on Suspension Changes

You are correct - it will never be a track car. Just a fun street car. Since you mention tires - I was tempted to put a set of ET Sebring 15" wheels because they look so much like the Halibrand magnesium wheels that GM used on so many of their race cars (57SS, the Stingray racer, '60 Sebring cars, the Grand Sports early on) and go after 15" bias-ply-look radials from either Coker or Diamond Back. Believe it or not - in the days where resto-modding is so popular, I actually want to go back to the 670-15 SKINNY tired original look!Given the age of the springs and shocks (probably 25-30 years old) and the fact that I was going to go through the suspensions to put new bushings in (they are dry-rotted) and detail things anyway, was the reason why I was going to put springs on the list, too. I figured while I was in there, might as well do it? What I should do is measure the ride height - and double check myself on how "tired" I think my springs really may be. It does appear to be sitting pretty low. Perhaps I should also hang some weights off the bumper and try to calculate what the k-factor in the current springs are to see if they really are as tired as I think.

Back in the day the 63 got bad press just like the 84 for too harsh of a ride and was softened up in 64 just like the 85 was. I find the 63 front springs to be perfect with Koni adjustable shocks all the way around and adjust them for a firm ride. I changed my rear stock 9 leaf spring out many years ago for a 7 leaf from a big block 67 so it was, I assume an F40 spring. I had poly on the spring ends for a while and found them to be too harsh so went back to the stock rubber from GM. I also have GM rubber in all of the rest of the bushings in the suspension and find them to be the best. I have put over 100k miles on the vehicle with what I would call spirited driving on the lovely Colorado mountain passes and carving corners all over the western states. The spring ends and differential support rubber has been changed the most often. My 63 is fuel injected and has a 67 big block rear differential with all of the heavier parts in it. The trailing arms are 63. The anti-sway bar is the stock one and seems to work fine but I have often been going to put the large one on and a rear one on also but haven't got around to it yet. I find the car highly predictable and easily steered out of any over exuberant expectations on my lack of experienced driving. I ran Michelin radials for years but the last tires I put on were staggered 205 /65/15/ Michelin on the front and 225/75/15 Kumco on the rear. They seem to work well without any rubbing or other problems. I have driven the car a lot and it has been as good to drive as any I have owned.

[Duke W.]

Re: 63 SWC: Advice on Suspension Changes

The production ride frequencies were well thought out and the high roll centers yield good roll stiffness without huge anti-roll bars. The result is a decent ride with excellent steering response and handling if all the OE components are in good working order.

The foundation of any automotive suspension system is tires, and installing a "racing supension" with the typical cheap, rock hard tires that most guys run, is a total waste. You just ge a harsh ride for little increase in grip becauce ultimate grip is a function of tires. All the suspension does is exploit adhesion characteristics of the tires.

If anything, the production spring/bar setup with low grip tires makes the car twitchy at the limit, which can cause it to suddenly transition to oversteer. This can be mitigated by installing poly bushings on the front anti-roll bar links and/or replacing the production 3/4" front bar with the 13/16" bar that became standard circa mid-seventies.

Grip and steering response can also be improved with "alignment tuning", and I have previously recommended both "touring" and "sport" settings.

A dramatic reduction in ride harshness and restoration of rear ride height is easily achieved by rebuilding the production leaf spring with new liners and reinstalling it with new spring link cushions.

Last but certainly not least are shocks. Adjustable types like Spax or QA-1 are best since they can be adjusted to your specific driving style and road conditions.

So tires and shocks are the only new components you need to consider other than replacing deteriorated elastomeric parts. If you want maximum grip get a set of Avon CR6ZZ DOT legal racing tires. Install the 13/16" front bar with poly link bushings and use the "sport" alignment recommendations.

If you just want a good handling (good steering response and decent grip) car and decent ride, a typical set of "van tires" with poly front bar link bushings, "touring" alignment settings, and adjustable shocks will be very pleasant.

The OE base drum brakes work very well and the J-65 metallic brake option was suitable for road racing. Either system will lock up the wheels, but drum brakes don't have the linear modulation of disk brakes, so it takes more skill to use them. Effort can be high especially compared to modern cars that all have power brakes, so a vacuum booster can be considered if you just can't deal with the higher pedal effort.

As with the suspension, bringing the OE brake system back to "as new" is the best approach, and keeping the car as original as possible will maintain its market value better than "upgrading" the various systems.

There are many detailed discussions of tires, brakes, and suspension over the nearly 15 years that the TDB has been on the internet, so spending time searching the archives will serve you well.

Duke

[Paul Y.]

Re: 63 SWC: Advice on Suspension Changes

As always, Duke gives good information and advice. I forgot to mention that I have had the metallic brakes on the car the entire time also with no problem stopping once one gets used to them. ( They work better heated up than they do cold) If you go through the suspension from front to back like I did and make everything new as factory, you will be amazed at how well the car feels and handles even with the stock alignment settings (as adjusted for radials). The car did not come with radial tires but radial tires make it a wonderful improvement on an already great old car.