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[C2] Front Coil Over Suspension & Rear Sway Bar

 
Old 01-20-2018, 01:54 PM
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woodsdesign
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Default Front Coil Over Suspension & Rear Sway Bar

Guys,
I'm thinking of installing a front coil over suspension on my 65 coupe.
I have been looking at Ridetech but am interested in the forum's comments on other brands like Van Steel. If they are all basically the same then it is just a matter of cost.
I would like to hear what others have done and what you think the pros and cons are.
My initial though is to budget about $2500. It that reasonable?
As for the rear, is there any benefit in adding a rear sway bar? What brands do you guys recommend.

Thanks
Larry
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Old 01-20-2018, 01:56 PM
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what are you trying to accomplish? catalog engineering never works out to well
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Old 01-20-2018, 02:14 PM
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Hi Larry,

I'd suggest you take a look at Global West . . .they offer everything from simple bushing kits (featuring their amazing Del-A-Lum bushings) for your stock control arms to custom upper and lower control arms designed to improve the front end geometry - plus coli over kits as well. Don't forget to check out their videos where they showcase the benefits of their products. I have their Del-A-Lum bushings in my stock lower control arms and I LOVE them! Good luck!

Tom
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Old 01-20-2018, 03:53 PM
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Originally Posted by Nowhere Man View Post
what are you trying to accomplish? catalog engineering never works out to well
I want to lower the car's stance by about an inch.
But, last year on the way to Carlisle I had to make a fast maneuver at about 75. I wasn't impressed with the response. I run Borgeson.

Last edited by woodsdesign; 01-20-2018 at 04:47 PM.
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Old 01-20-2018, 03:58 PM
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Originally Posted by woodsdesign View Post
I want to the car's stance by about an inch.
But, last year on the way to Carlisle I had to make a fast maneuver at about 75. I wasn't impressed with the response. I run Borgeson.
how wore out is the rest of the suspension and tires
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Old 01-20-2018, 04:07 PM
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Originally Posted by Nowhere Man View Post
how wore out is the rest of the suspension and tires
All new poly bushings. New Michelin's from DB. Mounted on bolt on KO's.
A truck kicked up a big piece of metal and I had to go on the berm.
I had a little over steer that I want to get rid of.
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Old 01-20-2018, 04:32 PM
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I installed the semi coil over front suspension in a 63 and Iím very impressed with it so far. Great upgrade for $700. I used the single adjustable shocks.
I have about a 1.5Ē rake in the stance. I would go with the 450pd Springs.

Last edited by 65silververt; 01-20-2018 at 04:33 PM.
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Old 01-20-2018, 04:36 PM
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Donít add a rear sway bar if you have a small block. John z has discussed this topic several times, so do a quick search using his name and rear sway bar
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Old 01-20-2018, 04:50 PM
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Originally Posted by 65silververt View Post
Donít add a rear sway bar if you have a small block. John z has discussed this topic several times, so do a quick search using his name and rear sway bar
I remember that now. Thanks
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Old 01-20-2018, 05:23 PM
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Originally Posted by woodsdesign View Post
I remember that now. Thanks
I have Van Steel front kit with tubular a arms and QA1 coil overs single adjustable shocks 450 # springs front dropped about an inch. Takes some weight off the front end.
Should be under $2000 if your installing.
Very nice with rack and pinion and radials.
Considering a 400# spring since I have taken so much weight off the front end the 450 is stiff. Aluminum heads and water pump, mini starter. Wilwood mini lite front calipers and master cylinder.
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Old 01-20-2018, 05:29 PM
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Originally Posted by 65silververt View Post
Donít add a rear sway bar if you have a small block. John z has discussed this topic several times, so do a quick search using his name and rear sway bar
I just went through 6 pages in a search using the above and could not find it. Anyone have a link?
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Old 01-20-2018, 05:46 PM
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Old 01-20-2018, 06:08 PM
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One thread with a discussion on rear sway bars. https://www.corvetteforum.com/forums...-sway-bar.html
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Old 01-20-2018, 07:19 PM
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Originally Posted by 65silververt View Post
One thread with a discussion on rear sway bars. https://www.corvetteforum.com/forums...-sway-bar.html
Thanks, that is the info I was looking for.
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Old 01-21-2018, 01:14 PM
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The C2 base suspension is very "neutral", but can be twitchy at the limit and suddenly transition to oversteer on trailing throttle or with very quick steering inputs.

Tire construction and front camber have a big input on steering response. Going negative on camber will improve it, but increase oversteer bias. This can be mitigated by replacing the front rubber anti-roll bar link bushings with hard urethane bushings.

If the car still has too much transient oversteer bias, replace the OE 3/4" anti-roll bar with the 13/16" bar that was used on C3 base suspensions beginning circa mid seventies. A larger front anti-roll bar will increase front roll stiffness and understeer bias, and the increase in roll stiffness is a function of the fourth power of bar diameter, so even a 1/16" difference in bar size will have a noticeable effect on transient and steady state dynamic response.

Also, having about 1/16" rear toe (with radial tires) EQUALLY DISTRIBUTED SIDE TO SIDE IS CRITICAL TO STABLE HANDLING! So when was the last time you had the car's alignment checked?

Case in point. I was helping the owner of a 15,000 original miles '67 L-71 prepare for a PV. I tested steering response with short, but quick steering inputs to test stability. Right was fine, but left resulted in definite rear instability in the form or oversteer.

So I said the alignment, particularly rear toe, needed to be checked. The LR toe-in was about 1/16", but the right was 1/8" TOE OUT! No wonder the rear wanted to step out with a quick left flick of the wheel.

Given the low miles I figured that the shims were as installed by St. Louis. So how did the RR toe end up so far out of spec? I could only guess, but my best WAG is that the operator installed the RH trailing arms shims "backwards" i.e. he installed what should have been the inside stack on the outside and vice versa.

Case number 2: My 1976 Cosworth Vega. In OE form it had excellent steering response (even with the junky OE Goodyear radials that had a habit of disintegrating without warning) and was dead neutral up to the limit when it would transition to oversteer. With a little help from Fred Puhn's "How to Make Your Car Handle" I figured out the problem and an easy solution. The front bar like most GM cars had compressible rubber bushings on the bar to control arm links, but the rear bar was solidly bolted to the trailing arms. So what was happening is that increasing lateral g caused increasing roll, which further compressed the link bushings, reducing front roll stiffness. This reduced front/rear roll stiffness distribution to the point where it caused the car to transition to oversteer just below the ultimate adhesion limit.

The solution was to replace the OE rubber anti-roll bar link bushings with the hard urethane bushings that were OE on Pontiac Trans-Ams.

From the early eighties to late nineties I ran this car in track events at Riverside and Willow Springs (on better tires). People who rode with me were amazed at how neutral and forgiving this car was. I could keep it at the ragged edge of adhesion in a slight four-wheel drift in the big sweepers with just minor steering and throttle adjustments.

I did add 1/16" larger front and rear bars along with Spax adjustable shocks. This took about two years at four events per year making one change at a time before it was fully dialed in, and in the early nineties I installed a set of real DOT legal racing tires - 205/60VR-13 Toyo Proxes RA-1s to replace the Phoenix Stahlflex 3011s I had used previously, which were the hot setup in showroom stock racing going back the the late seventies.

I never lost control of it on road or track, but in the process embarrassed a lot of name brand sports car (like beginning with F and P) drivers. A lot of them were way faster down the big straights, but could not out-brake or out-corner me to such an effect that my "Vega" turned better lap times.

So before you spend 2500 bucks on a suspension" upgrade", get the alignment checked and corrected as necessary and apply the tuning tricks I recommended above if you want to experiment further at little cost.

Over the years I've talked to many aftermarket suspension outfits, and when I stated asking some basic vehicle dynamics questions like ride rates and roll stiffness distribution, they all went catatonic. Clearly, none of them had even a basic understanding of vehicle dynamics. Like many aftermarket cam manufactures it was all about "bigger is better" - duration and overlap or spring rates and anti-roll bar sizes.

I don't know if Puhn's book is still in print, but I'm sure you can find serviceable used copies on the Web. Unless you have a sound background in vehicle dynamics I strongly suggest obtaining a copy before you spend one thin dime on "suspension upgrades". It's written for the average amateur car enthusiast/racer, so you don't have to have an engineering and math background to understand the basic principles.

Basic principle: if you want to increase understeer bias/decrease oversteer bias, increase front roll stiffness with stiffer springs and/or a bigger bar and vice versa if you want to reduce understeer/increase oversteer, and fine tuning an be done with camber adjustments. If you can grasp this principal, you will understand that increasing rear roll stiffness on a small block C2 by adding a rear bar will create an oversteering beast unless you compensate by installing an appropriately bigger bar on the front.

Throwing money at a problem will never solve it unless you understand, at least at a high level, the underlying physics. Example #1: federal, state, and local government!

Duke

Last edited by SWCDuke; 01-21-2018 at 02:41 PM.
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Old 01-21-2018, 05:11 PM
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Originally Posted by SWCDuke View Post
The C2 base suspension is very "neutral", but can be twitchy at the limit and suddenly transition to oversteer on trailing throttle or with very quick steering inputs.

Tire construction and front camber have a big input on steering response. Going negative on camber will improve it, but increase oversteer bias. This can be mitigated by replacing the front rubber anti-roll bar link bushings with hard urethane bushings.

If the car still has too much transient oversteer bias, replace the OE 3/4" anti-roll bar with the 13/16" bar that was used on C3 base suspensions beginning circa mid seventies. A larger front anti-roll bar will increase front roll stiffness and understeer bias, and the increase in roll stiffness is a function of the fourth power of bar diameter, so even a 1/16" difference in bar size will have a noticeable effect on transient and steady state dynamic response.

Also, having about 1/16" rear toe (with radial tires) EQUALLY DISTRIBUTED SIDE TO SIDE IS CRITICAL TO STABLE HANDLING! So when was the last time you had the car's alignment checked?

Case in point. I was helping the owner of a 15,000 original miles '67 L-71 prepare for a PV. I tested steering response with short, but quick steering inputs to test stability. Right was fine, but left resulted in definite rear instability in the form or oversteer.

So I said the alignment, particularly rear toe, needed to be checked. The LR toe-in was about 1/16", but the right was 1/8" TOE OUT! No wonder the rear wanted to step out with a quick left flick of the wheel.

Given the low miles I figured that the shims were as installed by St. Louis. So how did the RR toe end up so far out of spec? I could only guess, but my best WAG is that the operator installed the RH trailing arms shims "backwards" i.e. he installed what should have been the inside stack on the outside and vice versa.

Case number 2: My 1976 Cosworth Vega. In OE form it had excellent steering response (even with the junky OE Goodyear radials that had a habit of disintegrating without warning) and was dead neutral up to the limit when it would transition to oversteer. With a little help from Fred Puhn's "How to Make Your Car Handle" I figured out the problem and an easy solution. The front bar like most GM cars had compressible rubber bushings on the bar to control arm links, but the rear bar was solidly bolted to the trailing arms. So what was happening is that increasing lateral g caused increasing roll, which further compressed the link bushings, reducing front roll stiffness. This reduced front/rear roll stiffness distribution to the point where it caused the car to transition to oversteer just below the ultimate adhesion limit.

The solution was to replace the OE rubber anti-roll bar link bushings with the hard urethane bushings that were OE on Pontiac Trans-Ams.

From the early eighties to late nineties I ran this car in track events at Riverside and Willow Springs (on better tires). People who rode with me were amazed at how neutral and forgiving this car was. I could keep it at the ragged edge of adhesion in a slight four-wheel drift in the big sweepers with just minor steering and throttle adjustments.

I did add 1/16" larger front and rear bars along with Spax adjustable shocks. This took about two years at four events per year making one change at a time before it was fully dialed in, and in the early nineties I installed a set of real DOT legal racing tires - 205/60VR-13 Toyo Proxes RA-1s to replace the Phoenix Stahlflex 3011s I had used previously, which were the hot setup in showroom stock racing going back the the late seventies.

I never lost control of it on road or track, but in the process embarrassed a lot of name brand sports car (like beginning with F and P) drivers. A lot of them were way faster down the big straights, but could not out-brake or out-corner me to such an effect that my "Vega" turned better lap times.

So before you spend 2500 bucks on a suspension" upgrade", get the alignment checked and corrected as necessary and apply the tuning tricks I recommended above if you want to experiment further at little cost.

Over the years I've talked to many aftermarket suspension outfits, and when I stated asking some basic vehicle dynamics questions like ride rates and roll stiffness distribution, they all went catatonic. Clearly, none of them had even a basic understanding of vehicle dynamics. Like many aftermarket cam manufactures it was all about "bigger is better" - duration and overlap or spring rates and anti-roll bar sizes.

I don't know if Puhn's book is still in print, but I'm sure you can find serviceable used copies on the Web. Unless you have a sound background in vehicle dynamics I strongly suggest obtaining a copy before you spend one thin dime on "suspension upgrades". It's written for the average amateur car enthusiast/racer, so you don't have to have an engineering and math background to understand the basic principles.

Basic principle: if you want to increase understeer bias/decrease oversteer bias, increase front roll stiffness with stiffer springs and/or a bigger bar and vice versa if you want to reduce understeer/increase oversteer, and fine tuning an be done with camber adjustments. If you can grasp this principal, you will understand that increasing rear roll stiffness on a small block C2 by adding a rear bar will create an oversteering beast unless you compensate by installing an appropriately bigger bar on the front.

Throwing money at a problem will never solve it unless you understand, at least at a high level, the underlying physics. Example #1: federal, state, and local government!

Duke
I just had the alignment done by Corvette Conspiracy about two years earlier. They have done an alignment since the incident.
But I expected the handling to be better. The front sway bar is 1" ( I measured it today) and was on the car when I bought it. I have urethane bushings.
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Old 01-22-2018, 10:03 AM
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So the suspension has already been modified. What are the alignment settings? It's impossible to analyze a problem without data.

Also, what's the make, model, size, and UTQG ratings of the installed tires, and what cold TP do you run?

When you say "urethane bushings" are you talking about all the suspension pivot points or just certain points?

Interchangeable C2/3 OE Corvette front bars are 3/4, 13/16, 7/8, 15/16, and 1 1/8", so if you measured 1" it must be aftermarket, of maybe your measurement was not sufficiently precise. Bar diameter should be measured on a section that is not formed, and you should clean off any surface rust, which can effect the measurement.

Duke
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Old 01-23-2018, 01:27 PM
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Default Fred Puhn Handling Book

Here is link for the book in a free PDF format. I downloaded it.
https://bajatutor.net/wp-content/upl...-Fred-Puhn.pdf
Once your car is aligned, all of this stuff is trail and error in my book...especially spring rates. Most are looking for a comfortable ride and decent cornering. These two things are the hardest to achieve.
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Old 01-23-2018, 09:43 PM
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Thanks for that link to Puhn's book.

Base Corvette suspensions have a rather decent ride, especially compared to some modern "performance" cars. Some have nearly knocked fillings out of my teeth on So Cal's deteriorating freeways.

Of course, the first thing you need to improve "handling" is decent tires, not the rock hard S-rated radials that most guys run, and a good choice is the V-rated Avon CR6ZZ DOT legal racing tire, which is available in common radial sizes that fit Corvette OE wheels and wheel wells.

Once you have decent tires then you start tuning, and you should only make one change at a time, so you don't confuse what it does with other changes that are made at the same time.

Using my Cosworth Vega as an example, before I ever ran a track event I installed the urethane anti-roll bar bushings and Bilstein Sport shocks. After one or two events I dialed one degree negative camber into the front suspension. All worked well, but after a couple of more events I wanted to reduce roll. So I replaced the 1" front bar with a 1 1/16" bar that was on base H-Specials. I expected less roll, but more understeer, which is exactly what I got.

So I installed a 1/16" larger rear bar (aftermarket) for the next event, and it went back to dead neutral with less roll, but I was never happy with the damping rates. The Bilstein Sports had too little front rebound damping and too much on the rear.

So I arranged a group buy through the Cosworth Vega Owner's Assc. of Spax rebound adjustable shocks, and installed the Toyo DOT legal racing tires about the same time. I had to crank the fronts down to nearly the stiffest setting with the rears about halfway, but it was PERFECT!

That was as the late nineties were approaching and events were getting more crowded, especially with novice drivers, and it was getting tough to get a clear track free of traffic. So about the time I got the car totally dialed in I decided to "retire" from track events, but still enjoy driving it in the road with some occasional canyon runs in the mix.

BTW, the CV OE ride rates are higher than a base C2 even though it's about 300 pounds lighter than a base small block, so I knew I didn't need to mess with the springs, and with the shock settings it rides a little stiff on bad roads, but meets my needs for how I use it, and it's very responsive, sticks like glue, and fun to drive.

So, yes, it requires experimentation, but if you understand some basic vehicle dynamics and spend the time and effort to test one change at a time, you will be well rewarded.

Duke

Last edited by SWCDuke; 01-23-2018 at 09:48 PM.
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Old 01-23-2018, 11:54 PM
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Originally Posted by Nowhere Man View Post
what are you trying to accomplish? catalog engineering never works out to well
I think that's an exaggeration. Many here have assembled setups that suit their needs from catalog parts and feedback has helped others do the same. Lets face it, even running larger wheels and sticky modern tires changes the parameters and not necessarily in favor of the original GM design.

Usually for less oversteer it's less rear bar not more. Some oversteer has been blamed on changing geometry as the relatively rudimentary IRS loads and unloads. From personal experience worn camber rod and trailing arm bushings also allow dramatic and sometimes dangerous changes to occur as you go on and off the power, check those out !
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