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You may find this useful as well: Whenever I see comments about C3 Corvettes having hugh oversteer with stock or nearly stock suspensions, I am completely perplexed....My completely stock 78 gymkhana suspended car displayed heavy understeer at the limit and the reason for the trek to eliminate said understeer...............From a C3 corvette owner below...
BTW-completely agree and why I run my Gm STyle 3/4 inch rear bar....with my setup. Not sure what size rear bar this guy is using but I suspect around 7/8 inch with his front 1.25 inch bar.
If you are a C3 owner experiencing big oversteer whether BB or SB at low to moderate speeds whether with a stock suspension or modified with sway bars front or rear, there is something VERY wrong with your setup.
Herb Adams certainly knows more about this subject than me and any one on this forum..................
" Impressions of my huge rear sway bar
As you know I installed a 1 1/4 inch speedway bar on the back to go with my 1 1/4 inch front bar. The front is extremely stiff with a 1/4 inch wall tube. It is alot stiffer then the 1 1\8th in solid bar. For the back I used 3/16 wall tube.
I also used bearing blocks on the front and bushings , but good fitting bushings on the rear and 8 rod ends in total for the 2 bars.
After installing the bar I took the car for a short ride to settle the suspension and then adjust the linkage so there was no preload on the sway bar. I found the bar in this short run extremely stiff. The car felt like it had really stiff springs.
Last night I took it for it's first real run. Carguy4sure and I went 50 miles across country to a show. 25 each way.
As I started cruising at 60 I found the bar seems to smooth out, the ride was not harsh like slow speed in town. I even put the outside wheel close to the rought edge of the road to make that side work and it felt really smooth.
I entered a few corners at about twice the recommended speed and found myself accelerating as the corner became more comfortable and would come out of the corner 15 or 20 mph faster then when I went in. I also lost my buddy Doug.
I also found not once did the car ever feel twitchy. My car is not bad but occasionally you feel that twitch. It seems to be gone. Maybe our twitch is comming from the rearend??
I feel it was a big improvement over last week without the bar. It was worth the roughtly $350 I put into the project.
The reason I went with the huge rear sway bar is because of an article I read from Herb Adams and talking to twin Turbo. 2 very knowledgabel guys.
This was taken this morning from Corvette action, posted by Kid Vette but it is taken from Herb Adams, This is what convinced me a few weeks ago.
Agian I took this from KID Vette/Corvette action/Herb Adams
Here's Herb Adams direct quote, "One reason we recommend larger, more effective stabilizer bars for Corvettes is the bars' ability to control a car's understeer characteristics. Standard Corvettes are produced at the factory with a great deal of understeer built into their suspensions.Anyone who has driven a Corvette hard into a corner has probably experienced understeer. The car "plows" or "pushes" through the corner. Regardless of the term used to describe the condition, the front tires must be pointed more into the turn to keep the car on its line (see diagram A). Oversteer is the opposite effect: the front tires are pointed outward, and the car is said to be "loose" or "hanging out" (as in diagram B). Neutral steer is the middle ground between oversteer and understeer. Both the front and rear tires are running at the same angle to the road. A Corvette set up for neutral steer will be faster in steady state cornering than one which over- or understeers because all four tires are sharing the cornering loads equally. By using the recommended stabilizer bars, your Corvette will become very close to the desired neutral steering attitude.
Factors such as the number of people in the car, road conditions, vehicle speed, and other variables can influence the handling characteristics of your car. Driving technique can compensate for these small changes if the car is close to the neutral state. In some special circumstances a slight degree of oversteer is beneficial. Certain autocross courses, for example, favor a car which oversteers somewhat. In general, though, you will probably be most comfortable in street driving conditions with a car set up to corner with a very slight amount of understeer. It is necessary to control body roll on cars with independent suspensions because there is little anti-roll effect built in. Stabilizer bars control body roll by requiring the bar to be twisted if the body is to roll. Since larger diameter bars are harder to twist, they are more effective in limiting body roll. Stabilizer bars are used to control body roll because they have little effect on the up and down motions of the suspension. Stiffer springs can also be used to control body roll, but they also decrease the suspension's ability to absorb bumps so the ride quality is poorer. Some of the reasons it is necessary to control body roll in cornering are for driver and passenger comfort, to limit the effects of roll steer, and to limit the loss of cornering power due to camber change. If a car rolls at too great an angle driving around a corner, like a Renault, the passengers feel like the car will tip over. Since the Corvette suspension has a considerable amount of roll-steer built in, this unwanted steering effect is reduced if body roll is reduced (roll steer is that part of the suspension geometry that causes the wheels to steer toward understeer as the body rolls.) GM always builds this into their cars on the premise that it makes them safe in spite of the driver's abilities. Performance minded drivers don't need much protection for themselves, so they don't need much roll steer.
The camber effects of body roll are caused by the fact that, as the body rolls, the tires roll with it. This causes the camber to increase on the outside tires, which reduces their cornering power, if body roll is minimized, the outside tires can remain perpendicular to the ground and deliver maximum cornering traction. The best way to limit body roll is to install bigger (and therefore stiffer] stabilizer bars. It is also an advantage to connect the stabilizer bars to the control arms with steel joints lo eliminate lost motion.
If a car, such as a Corvette, is equipped with both a front stabilizer bar and a rear stabilizer bar it is possible to control the amount of understeer and oversteer. When a larger rear stabilizer bar is used, the car will move toward the oversteer side of handling. If a large enough rear bar is used, the car will oversteer."
[Online]
I found buying the Bilsteins from the US was almost the same price as the kybs over here. I think you're right to stick with the 7/16 bar, at least to begin with, and make further decisions when the car is up to scratch. My car is still running factory gymkhana swaybars and springs (front shortened by a coil, and rear shortened (for tyre clearance) and with longer bolts (to lower it). I think my car sits pretty well, and I do track it. Judge for yourself, this was last weekend:
Other components are Energy Suspension poly bushes throughout, Bilsteins, Global West upper arms in the front, Moog ball joints/tie rods/idler arm, Borgeson steering box, and a spacer between diff and strut rod mount to reduce camber gain in the rear. I found my car handles dramatically differently at it's real limits (on the track) than I would have anticipated from fast road use...
Last edited by Metalhead140; 05-28-2017 at 09:00 AM.
I'm very happy with how it handles at this point, just going to concentrate on improving my driving for a while! Yes, I'll likely end up with a 360lb glass spring at some point, I think 360lb in glass will handle fairly similar to the gymkhana rear spring (stiffer needed due to not having the damping effect of the multiple steel leaves). More for the weight drop and ride quality than anything else though. I might be able to improve entry speed a little with more rear stiffness, but exit speed is where most time is made up on a race course, and I already have to be gentle on the throttle exiting corners.
I'm very happy with how it handles at this point, just going to concentrate on improving my driving for a while! Yes, I'll likely end up with a 360lb glass spring at some point, I think 360lb in glass will handle fairly similar to the gymkhana rear spring (stiffer needed due to not having the damping effect of the multiple steel leaves). More for the weight drop and ride quality than anything else though. I might be able to improve entry speed a little with more rear stiffness, but exit speed is where most time is made up on a race course, and I already have to be gentle on the throttle exiting corners.
Yes, the 360 composite will make a HUGH difference in the ride and will have better response rate than the 292lb gymkhana stock steel spring. I have the 360 composite on my 78 since 1986! I would make sure that you use a high quality shock with the composite. I originally had bilstein HD's and found the ride too bouncy and went to Bilstein Sports in the rear ONLY and it is perfect with the Sports.
I have never driven a RWD sports car or formula car of sufficient power to weight ratio where I have not had to be prudent with the throttle coming out of a turn on a race course to keep the back from oversteering either some or much. The trick is to be able to carry more entry speed as you said AND to keep the car stable through mid corner with steady throttle. The steady state, entry corning and throttle out existing all define the actual handling of the car. Most people on the street mistakenly characterize throttle on power as the car oversteering...just about any RWD car of sufficient power will exhibit power on oversteer......often referred to snap oversteer as well.
I recently drove brand new 2017 BMW M2, M3, and M4's on the BMW race track in Spartenburg SC and was absolutely amazed that with stability control engaged on the track, I could not get the rear end to come loose exiting very sharp turns even at full throttle from the 450 HP twin turbo V6...amazing! The car would wiggle a tiny bit and then the electronics would intervene with the engine output reduction and individual brake caliper application necessary to reduce the slip angle of the car.
I'll agree that a an amount of controllable oversteer during corner entry can certainly help a car rotate into the apex, particularly at low to medium speed turns. But, I've found it's preferable during corner exit for balance to have transitioned to mild understeer, otherwise there's no surplus rear traction available to facilitate adding throttle until once again pointed dead straight. And, relying too heavily on rear bar to provide rear anti-roll stiffness in lieu of running more rear spring (where practical) doesn't help matters.
Thing is, a decently well sorted car's balance characteristics can be fine-tuned somewhat by varying driving technique, which I submit constitutes a better description of what having a "neutrally balanced" car means. However, while one may desire inducing an amount of corner entry oversteer to help get pointed into tight turns, IMOE the tail-out approach isn't the quick way 'round truly fast bends such as The Kink. JMHO.
Ok so so replaced the stock sway bar bushes, what a **** of a job !!! to get the mushroom bush through the sleeve... x4 when u have to do the end links too. Metalhead where are you in Oz ? would be good to pick your brain on a few things
Cool little track! That actually looks like a lot of fun.
It is! It's basically a kart track, a bit tight in a Vette but very fun.
Originally Posted by TheSkunkWorks
I'll agree that a an amount of controllable oversteer during corner entry can certainly help a car rotate into the apex, particularly at low to medium speed turns. But, I've found it's preferable during corner exit for balance to have transitioned to mild understeer, otherwise there's no surplus rear traction available to facilitate adding throttle until once again pointed dead straight. And, relying too heavily on rear bar to provide rear anti-roll stiffness in lieu of running more rear spring (where practical) doesn't help matters.
Thing is, a decently well sorted car's balance characteristics can be fine-tuned somewhat by varying driving technique, which I submit constitutes a better description of what having a "neutrally balanced" car means. However, while one may desire inducing an amount of corner entry oversteer to help get pointed into tight turns, IMOE the tail-out approach isn't the quick way 'round truly fast bends such as The Kink. JMHO.
Yeh, this basically reflects my POV at this stage in time. The car turns in well, mid corner is pretty good, and always tends towards oversteer at exit. I've actually been considering trying some runs at some point with the rear bar disconnected to see how it goes. Slow in fast out is almost always the quickest way around most courses.
I've only been driving this car in events for the last couple of months, I'm still getting used to it as my previous competition has been in much smaller lighter sports cars. But at the last 2 events I've been the quickest car in attendance not on semi-slicks or slicks, so the car is working pretty well. The event the videos above are from, I was in a class with 12 entrants, and all other cars in my class were caged race cars (I'm bumped up due to having fitted fuel injection) that were trailered to the event and running on semi slicks. I came 5th out of 12 in class, a pretty good effort I think in my street car that I drove the 180 miles each way to and from the event, on the same street tyres that I competed on.
Originally Posted by R6n350GT
Ok so so replaced the stock sway bar bushes, what a **** of a job !!! to get the mushroom bush through the sleeve... x4 when u have to do the end links too. Metalhead where are you in Oz ? would be good to pick your brain on a few things
Hey mate, I'm in NSW, near Newcastle. How about yourself?
I cut up the bushings from the VB&P kit to place between the washer and sway bar to mount the CMR6 units and added washers to make up the space between the CMR6 units and the OEM hardware on the trailing arm.
I cut up the bushings from the VB&P kit to place between the washer and sway bar to mount the CMR6 units and added washers to make up the space between the CMR6 units and the OEM hardware on the trailing arm.
That heim joint on a non factory rear sway bar is really slick and probably does the trick on minimizing trailing arm binding...I like it! Thanks
I wonder how your car will do with a 330 or 360 composite. The response characteristic of a composite versus steel spring of the same rating are very different. Another words, the 292lb steel gymkhana spring will behave very differently then a 300lb rated composite, the numbers are the same but the handling effect will be very different due to the reaction time of the composite spring. I would try a composite first before changing anything else.
Removing the rear 7/16 bar for some runs would be interesting as well but I suspect more understeer entering the corner, more understeer mid corner, and less oversteer exiting.
Third thought is a 1.25 inch front bar with a rear 9/16 GM style rear bar. I wonder what that change would have as well.
Good stuff...Thanks
BTW-On the street (I don't race my C3 on the track), I think with my setup, I have hit the sweet spot with the 1 1/8 factory OEM GM front swaybar with poly mounting AND poly endlink bushings (makes the bar act like a 1 1/4 inch bar or close to that size) and the 3/4 inch GM style rear sway bar....my turn in is crisp on sharp exit/entrance ramps, neutral/VERY slight oversteer mid corner with 4 wheel drift over the limit, and VERY slight oversteer at exist. When racing on the track, I prefer slight oversteer to understeer...nothing worse than turning the front wheels and having the car head straight to a guard rail!
I would not advocate the typical C3 owner even remotely experimenting with their C3's on exit ramps as a warning!
These are 60-70 mph turns at most. I would suspect that my 78 on the track with high speed cornering would benefit from a slightly bigger front swaybar (1.25 inch) to dial out the slight oversteer at greater speeds and for some insurance.....
i'm running a Rancho 1 1/4" bar in front and 3/4" in the rear, both set to the lowest settings. That's one thing I like about these bars; they can be fine tuned without changing bars. Things seem to be pretty well balanced. By the way, I'm running stock springs in front and a 300 lb VB&P on the back.
Yes, I'm a big bars-soft springs guy. The Rancho bars are very similar to what Herb Adams sold for years.
i'm running a Rancho 1 1/4" bar in front and 3/4" in the rear, both set to the lowest settings. That's one thing I like about these bars; they can be fine tuned without changing bars. Things seem to be pretty well balanced. By the way, I'm running stock springs in front and a 300 lb VB&P on the back.
Yes, I'm a big bars-soft springs guy. The Rancho bars are very similar to what Herb Adams sold for years.
I have always been a fan of bigger bars, softer springs as well...this approach has been well documented going back to the 80s
I wonder how your car will do with a 330 or 360 composite. The response characteristic of a composite versus steel spring of the same rating are very different. Another words, the 292lb steel gymkhana spring will behave very differently then a 300lb rated composite, the numbers are the same but the handling effect will be very different due to the reaction time of the composite spring. I would try a composite first before changing anything else.
Removing the rear 7/16 bar for some runs would be interesting as well but I suspect more understeer entering the corner, more understeer mid corner, and less oversteer exiting.
Third thought is a 1.25 inch front bar with a rear 9/16 GM style rear bar. I wonder what that change would have as well.
Good stuff...Thanks
BTW-On the street (I don't race my C3 on the track), I think with my setup, I have hit the sweet spot with the 1 1/8 factory OEM GM front swaybar with poly mounting AND poly endlink bushings (makes the bar act like a 1 1/4 inch bar or close to that size) and the 3/4 inch GM style rear sway bar....my turn in is crisp on sharp exit/entrance ramps, neutral/VERY slight oversteer mid corner with 4 wheel drift over the limit, and VERY slight oversteer at exist. When racing on the track, I prefer slight oversteer to understeer...nothing worse than turning the front wheels and having the car head straight to a guard rail!
I would not advocate the typical C3 owner even remotely experimenting with their C3's on exit ramps as a warning!
These are 60-70 mph turns at most. I would suspect that my 78 on the track with high speed cornering would benefit from a slightly bigger front swaybar (1.25 inch) to dial out the slight oversteer at greater speeds and for some insurance.....
TheSkunkWorks, Mealhead, jb78L-82 and other track junkies what brand and size wheels, offset are you using and tyre size and brand etc ?
And should i stick with a 2.87 gear ration when ill be using a LS1 and auto 4l60e
TheSkunkWorks, Mealhead, jb78L-82 and other track junkies what brand and size wheels, offset are you using and tyre size and brand etc ?
And should i stick with a 2.87 gear ration when ill be using a LS1 and auto 4l60e
Thanks guys !
For now I'm on a set of cheapy 'Ridler' brand 17x9.5s, 5.05" backspace (purchased from VPW), currently with 285/40R17 Continental ExtremeContact Sport tyres all round. These Contis are brilliant, I had 255/50R17 Nitto Invos prior which I thought were very good, but these are in a different league. Had to import them from the US, as they were only released a few months ago and the Australian distributors didn't have them yet. Tested by Grassroots Motorsport as being as quick as the Pilot Super Sport in the dry and substantially quicker in the wet. I preferred the look of the Invos, the larger diameter better filled the arches.
No idea what sort of gearing the auto has, but that's a tall rear end gear. I have 3.36 behind my tko600. Keep in mind tyre size when working out your diff ratios too - changing from the 255/50s to the shorter 285/40s effectively was the same as changing my rear gear to ~3.5.
Last edited by Metalhead140; 08-13-2017 at 04:03 AM.
TheSkunkWorks, Mealhead, jb78L-82 and other track junkies what brand and size wheels, offset are you using and tyre size and brand etc ?
And should i stick with a 2.87 gear ration when ill be using a LS1 and auto 4l60e
Thanks guys !
4l60E
1st 3.059
2nd 1.625
3rd 1.000
4th 0.696
I am Using a 245 45 R 18 (Michelin pilot super sport) which is a easy fit ~ 26.6" dia.
They fit on a stock 18x8" with a factory -12mm offset 4" BS No mod's required to fit. Same as the factory 15" wheels.
If you want to go wider check this forum for a thread with many many responses on wider wheels.
2.87 rear.
This would give you
With shifting @ 5500 RPM
1st 0-50 MPH
2nd 50-94 MPH
3rd 94-152 MPH if you can get there , but I don't think so.
So any road course where you don't exceed 50-94 MPH you would never shift other than 1 & 2nd. It may also be difficult to get the downshift to 1st without hurting the transmission. Not great track ratios for basically a 3 speed.
3.08 not much change
1st 0-46 MPH
2nd 46-87 MPH
3rd 87-141 MPH
3.36 (this starts to work for many tracks)
1st 0-42 MPH
2nd 42-80 MPH
3rd 80-130 MPH
3.55 (this will work for many tracks)
1st 0-40 MPH
2nd 40-75 MPH
3rd 75-123 MPH
Once you know where your max torque / HP rpm is you will find the sweet spot for a given track.
I drive at the track with 3.08 gears but I also have a T56 6 speed close ratio transmission. This gives me more options and a auto.
I started with a TH350 transmission where I could only do 1:41 Laptimes and after a switch to a T56 I was down to 1:36 with the only change in transmission.
Last edited by cagotzmann; 05-30-2017 at 11:39 PM.
I dont have easy access like you guys to parts. Anything i buy comes with a huge price tag here and shipping from usa is $40 min for a small package let alone sway bars and shocks. KYB will have to do for now.
Thanks for the help
have you tried Summit racing ? , their I parcel shipping option used to be very reasonable (I haven't tried it for a while ) but the best part is it will give you a price BEFORE you buy, I got my Bilsteins through them .
05-28-2017, 02:55 AM
