I thought this could be interesting.
Let's discuss what you did to improve your C3s handling, and how you like it.

I have a 27 year background in racing, Autocross, ProSolo and High Speed Road Racing, and engineering my own suspension solutions, but that was in a 1970 Camaro Z28 with an LT-1.

Quite a few things will change in my 454 LS6 C3, dream car build. But that is still under construction.

So what did YOU do? And how did YOU like it?

 

Here is the way I tuned the handling balance, understeer/oversteer, on my Z28:

My sway bar balance changed drastically over the years.

In the end handling balance all boils down to driver preference. Here are my two examples:

• Some drivers like a very neutral car setup in a corner, it feels very lively. It won't tolerate much throttle in the corner, but the corner points very well and is very responsive to steering and brakes. The rear might tend to step out on the brakes, or step out on the throttle. As long as this throttle induced oversteer is mild and you can control it. It is dead neutral with no throttle, and has throttle oversteer. It is like 4 wheeled steering. It is like playing. You can make either end of the car do anything you want. You just steer the rear of the car with the gas pedal. It is like a dance. Maybe you like to use a decent amount of throttle, so you give it a little more understeer. If you give it more understeer this playful dance feeling goes away. It makes for a car that is a lot of fun to drive on the street.

• Here is my big speed secret hard earned after 15 years on the track. It sounds a little counter-productive at first, but was taught to me by several National Champions. It is time for me to "pass it on". The fastest way around the track is to dial more understeer into the car than the above setup. The trick was to balance the car's handling, for dead neutral, only while the car was under WOT. It is not as lively, and honestly not as much fun to drive, at part throttle anyway. It understeers under no throttle, or even part throttle, and feels kind of sluggish. But the quickest way around the track is, as cottoneg mentioned, to go thru corners on the gas. My goal was on the throttle, WOT, by 25% of the way into the corner. So I took 75% of the corner under WOT. And I needed a perfectly neutral balance at WOT to get nice big long 4 wheeled drifts under power. Not just the tail sliding around, but the whole car. Just like the sprint car boys. This requires brand new driving lines and braking zones. And on a high speed track, these big drifts/slides took big kahunas. This was several seconds faster on a 60 sec course, but I had to relearn how to drive the course. I balanced it that way for 2nd gear for my autocross and pro-solo courses. On trips to the high speed track I had to rebalance it for WOT in 3rd gear, it needed much less understeer to do that. I ran the first tuning setup for 10-15 years and always wondered how the experts could possibly be 4-5 secs ahead of me. Then I tuned the car the second way, learned to drive it all over again, and joined the expert class for my last 10 years. I could take a 30mph 45* left turn, at WOT, and the car took off like a catapult out of the corner! I was already on the throttle 100ft before the next guy. The straight a way just got longer. But like I said, at part throttle or less, it felt sluggish.

So what did YOU do to your C3 and how do YOU like it?

 

You can probably find some older threads on the subject and issues that you address or work around with the C3. On the front check bump steer and camber gain. The front spindle is a bit short based on where the upper control arm is located in the frame. Some have used taller ball joints and if I recall correctly one guy modified the spindle.

On the rear camber gain can be dialed in by where the inner pivot of the lower link is mounted on the diff bracket. Because the car uses a trailing arm with no pivot link in the middle the arm pivots around the front mount. This causes toe change as the wheel moves in and out as the camber links go through travel. Old racers used to limit travel. Later the Rilley and Guldstrand design 5 link addressed toe. Later GT racers incorporated upper and lower control arms.

I used to race autocross in the Atlanta region a long time ago prior to me owning a C3. Used a gutted Monza to beat a number of cars.

 

Thanks!
What particular parts are you using and how does it drive?

 

Hey Leigh,

I'm happy to be your guinea pig this winter when I get the rest of my front end put together.

I'll be installing the SPC adjustable upper control arms and Global West lowers.

It has the 550 lb Springs in the front, the 380 composite spring in the rear, and qa1 single adjustable shocks. I also have the adjustable strut rods on the rear end for camber.

I would like to be able to take it to the track - New Jersey Motorsports Park or Watkins glen. My friend Steve (the one with the Boxster at the Csrs and Coffee) is at Watkins Glen this weekend.

 

Leigh, Sounds like you have a lot more experience than most of us mere mortals.
My car came factory as a gymkhana suspension car.
The original Bilstien's died a few years back. The factory rear leaf springs died early 90's.
So, my Car.
Factory front gymkhana springs with one coil cut. Bilstien B6's I think on the front. (Memory is a bit fuzzy, 6's on one end, 8's on the other). Offset and slotted upper A arm shafts. (Thanks Leigh). On factory A arms. Moog ball joints, tie rod ends etc. Factory power steering, NOT a replacement control valve, the original. Big difference! Energy suspension bushings on the control arms. Factory 1 1/8" sway bar. Energy suspension links and bushings.
4deg.castor .5 neg camber and just a touch of toe in. Almost zero.
Rear, VB&P 300 lb. Mono spring with the correct Bilstien shocks. 3/4 inch VB&P sway bar. Energy suspension links and bushings. Rubber bushings on forward trailing arms. Heim jointed adjustable strut rods. (Had poly for 25 years without issue). Just a touch of toe in in the rear. .4neg camber.
How do I like it? I like it alot.
Local track is fairly short between turns. A couple of off camber turns to keep you on your toes. Decent on the track for an old guy and street tires.
Very nice on twisty roads. Ride quality is actually pretty nice.
Oh, and ride height. 27" front to arch in fender 27 3/4" rear.

 

I did a frame-off restoration over last winter with one of the main goals being a safe decent suspension. I used a lot of Van Steel parts; tubular A arms, front semi-coilovers, composite rear spring (I went with #300), 3” half shafts, adjustable strut rods. Bilstein rear shocks. All new rubber bushings. Everything is new or rebuilt. Result is a nice handling but not harsh cruiser that I can carve up curves if I desire. Small block automatic car.

 

Any experience with front or rear oversteer with your setup?

Thanks Doc.
Yes I have to keep reminding myself that I am not building a competitive track weapon this time.
Trying to find the right balance for a fast comfortable street car with sharp reflexes.
Things are going to happen in a hurry when I drop the hammer, with 550 ft lbs, right off idle, so the suspension had better be able to keep up.
I just hope the old driver is up to the challenge! It's been 22 years .....or so...

 

Leigh1322, With 550 foot pound of TQ you are going to need lot's of rear spring to prevent squat. The ultimate is the six link c-3 setups with coil over and dual adjustable shocks.

Smart rear struts are a must. Then you want to limit verticle tire movement with big rear springs. With no internet in the early 80's or even any idea that Tom's and Vette Brakes and products existed. You were on your own. My 79 L-82 came with the 9 leaf. As mods started I saw the rear squating problem. So I went to a local spring shop and ask them to Add a leaf and re-arch the OEM. It actually became a 500# steel. Years later thinking about weight I bought the 420# mono from VB&P. I tested it for couple of days and yanked it back off. It was very wimpy compared to my steel spring of 20 years. I called up VB&P and they made me the 520# which is exceptable with QA-1 dual adjust rear shocks. Steel has some better properties than mono springs.

Rear sway bar is determined by tires and rear track width. I have 2 inch wheel adapters and 13 inch wheels my rear track width is 9 inches wider than stock. The width is leverage. 335 width tires have lots of tration in all directions. So I can get away with a big 3/4 rear sway bar.

 

Oversteer isn’t really an issue. The guys at Van Steel were great. If you give them a call and explain what you’re looking to do they can make suggestions. I think they can get you exactly what you’re looking for.

 

I think I know what I want to do, but...

I thought this thread would be good for everyone to share and discuss their various setups, and how they like them.
Their is a LOT of variation of parts we can install!

I know Gkull has a really serious track setup. Does it ever oversteer on throttle or brakes? Bottom out? etc. If so when?

 

My current plans. May change as the testing progresses:

Ridetech Delrin a-arm bushings
5* front caster
Van Steel Bump Kit - zero bump steer
Possibly .75" taller ball-joint
Borgeson steering box
Revalved from 28 in-lb to 46
QA-1 Single adjustable shocks
480# / 330# spings Front lowered .75" rear monoleaf rear stock height or lowered .75"
Heim end strut rod
Van Steel delrin diff raising and mounting kit
Wheels 18x9 or 18x10 , Nitto 55 or similar 285-35-18 or 275-40-18
14" padded steering wheel
Multiple sway bars, Stock BB f/r, also 1-1/8" fr,/ 75" rr
I can tune the sway bars with spring links on the front
It'll be corner weighted & adjusted
I'll try the single-adjusts, if I can't tune them for the ride / handling way I like, I'll go to Viking Double-Adjust
Goal: Cruiser ride, with slalom car reflexes in the corners, fairly neutral, with enough understeer so I can use some throttle in the corners, but not so much as to dull the steering input crispness.
Oversteer will never be more than a right foot twitch away at any rate.
I am ok if it squats on the throttle all the way to the bump stops, I'll control it with shocks, I value the cruiser ride more than ultimate performance, this is not a track weapon

 

I had to reread your posts above and really think about what you were doing. All of what you said about being on the throttle only applies to lower power to weight ratio vehicles. Cars that you drive around the track at WOT all the time except during braking. Which applies to every stock vette including every model up through the ZO-6 C-6s (up throught the 427 505 hp) The 600+ hp supercharged models are a different animal! Like the Miata class.

Over and under steer is better explained as: When your front end hits the wall first or the rear end hits the wall first. Tight is when the car won't turn and the front wheels are pushing through the turns from the centrifugal force of the turn. Loose is when the rear wheels are loose in the turns and the rear end of the car is trying to fishtail or spin out or come out from under the rear of the car.

Back to the question. Gkull does your C-3 Vette ever oversteer on throttle or brakes? Bottom out? etc. If so when?

As a driving instructor I tell the students to do your maximum braking in a straight line before you enter the turn or do any steering input. As you turn in you should be lifting off the brakes. Partial braking helps make a controlled rotation of the rear of the car (the term trail braking) before the apex of the turn. At some point in the turn you are going to be off the brakes and back to being on the gas. Then back to WOT as soon as traction will allow on the next straight. Learning to left foot brake is an advantage, but mostly used in cars being able to shift without the clutch.

The word "ever" oversteer is the most controlled way through a turn. Yes, I can bring the rear end around turning while on the brakes or when applying the throttle. Yes, I have gone into turns too fast and the front end pushing in bad over steer and run off into the gravel traps. Just misjudging the late braking. I have attended a drifting school to see how the pros do it! Personaly I couldn't afford the tire bills. Bottom out. Not that i know of. I installed 550# front and 500# rear very early when my vette was pretty new and that's what I learned to drive. I was looking at the F&R bump stops and they had no sign of ever being touched so I removed them as excess weight. YOU never want to hit the bump stops anyway. Going from suspension to solid is not a good thing. With springs and shocks you want to limit verticle wheel travel. I have nice shocks on my different vehicles and I never want to damage a shock by bottoming them out. So you look at the shock shaft and see the travel and how close it is to bottoming out in testing. The front or rear you dial up the spring for less shock travel and or increase the shocks compression setting. Adjustability is everything. Street and track are two different things. Tracks tend to have better predictable surfaces. I had my favorite on ramps driving my vette to work every day. As my tires and brakes went up 550# front springs were not enough even with a just over 3000 pound vette with driver. The local track closed about 5 years ago and I returned my vette to street only and it drives perfectly smooth with 650# front dual adjust QA-1's and 520# rear. It's just a fun driver with mid 600 hp 434 SBC.

With a 550 foot pound BBC I would opt for 550# front and at least 420# rear. I have the solid mounted rear differential which raises it @ 3/4 of an inch in relationship to the body on the frame. It does not change the angle of the half shafts. In a static half shaft position should be a slight down angle out to the tires. Under max rear compression you want to end up being nearly level. Compression to the point where the half shaft is going up to the tire is bad and puts a terrific load on the yoke ends and posi unit central pin. I used to break posi housings before I learned to limit rear wheel verticle travel. That and buying the best yokes and Tom's stage 6 posi cases

 

Agreed GKull.
I was a driving instructor also, and an SCCA course designer, and a safety steward.

I could discuss race car handling dynamics all day. But it might just be me and Gkull! LOL

But what about the street?

Anyone want to discuss or have a question or comment about how their car handles on the street?

 

Thanks Doc!

Mine should be pretty similar.
I may just go with some bigger wheels & tires tho.

 

A lot of people on here say a 3/4 rear bar is to much. Yet I've run one for years. Maybe I'm just used to it. But I'm actually very happy with the way my car handles. Except maybe in the wet. Rear easy to kick the rear out in the wet.

 

My son likes his ridetech kit. It handles really well.

We haven’t driven it with the 454 in it yet though. It should hold up pretty well though.

 

I have a question for you all about short course parking lot racing. Currently have 474lb-ish front springs (they’ve been cut so effective spring rate is higher), a 400 pound mono rear spring, 1.125” front sway bar and no rear bar. The rear also has adjustable strut rods. The car has been lowered and has 245/45r18 in the front and 285/35r19 in the rear - 300 tw tires. I have Koni single adjustable shocks that are a few clicks away from their highest rebound setting. The car weighs 3100 lbs. The alignment is factory spec.

The engine is a 383 with about 450hp/475tq (estimated) with a TH350.

In terms of from a dig, it just straight hooks. No wheel spin - it just goes. In fact I’m waiting for an axle to break…. It hits that hard.



My question is, the front in doesn’t seem to want to bite in the corner. It almost feels lazy. How do I tune out the understeer? Is it a camber issue? Do I need to drop the valving for more weight transfer? Tire pressure??

I need it to bite and rotate the rear to get it around the sharp corners as quickly as possible.

 

The biggest thing I did was take out most of the rubber when I could and replace it with solid. One of the biggest changes was my work on the rear control arms. I took out the rubber bushings in the front of the arm and replaced them with solid bushings. The cars when stock have a bit of trailing throttle oversteer. Lifting in a corner is not recommended.

A few more things:

1. When you want to make a change, you must have a reason. In other words, “What is the car doing that needs correction”.

2. Try to do one thing at a time so you know if the change is a good one.

3. Realize you may not like a change you made. I have a ton of parts from changes I made that did not result in better handling or made it worse.

4. Do not overlook the simple things. Your suspension must be in good shape. And follow up changes with a good front and rear alignment.

5. Go to a local track and consider a HPDE. You learn a lot on a road course.

I purchased my car in 1974. I used to track it a few times a times a year. Now, I’m 70 and it has become very expensive. My last trip to Summit Point Motorsports Park, between the gas, tolls, hotel, meal and track cost makes it cost prohibitive to do more than once a year.

 

Why no rear sway bar? Also, what steering box? I love my 80's manual steering conversion for the roads I like to drive in the Virginia "mountains". But for auto-X, I'd absolutely want the faster ratio and lighter steering of a Borgeson conversion (like in my 79).

For the street in my 80, I rebuilt the entire suspension, using poly everywhere except the trailing arm (rubber) and strut rods (heim joints). I added an OEM 9/16 sway bar from a big block car (with Energy Suspension poly bushings, of course). 550 springs front (uncut) and a NOS VB&P spring rear (shortened at the factory, and marked 385 lb). The most notable improvements came from the SPC adjustable upper control arms, the strut rods, the Bilstein shocks, and the manual steering conversion. It is still a bit soft in the rear. I need to get VanSteel to make me a stiffer low-arch spring.

It does fine driving in the mountains. I can keep up with newer Corvettes, and the limiting factor is the passenger pucker factor.