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1999 M6 V Code Active Handling car with totally defunct EBCM (death code). Pulled fuse for all related assists.
2 times I have experienced snap oversteer/looped the car. Once coming into the rollercoaster at VIR and once into a chicane at charlotte motor speedway (roval)
Looking for opinions on the cause and trying to rule out that the EBCM isn’t causing something I don’t understand/can’t fix.
My theories ranked by likelihood:
Braking and turning - Possibly turning too early before releasing brakes (nose dive/light rear end)
Currently running a 285/35r18 square setup - Could go 315/30 square
Alignment Specs - I had an alignment done and requested the suggested 1/8” toe in. If I recall my driver setting is at -.01 while passenger is at -.02 .. Would that small variance cause snap oversteer? How finicky is toe?
EBCM is causing something weird. My understanding is that 97-00 cars have a BPMV and biasing is done manually while 01-04 cars have DRP electronically controlled. If I understand correctly my car should be biased manually around 60/40 or 65/35? That would mean the EBCM/ABS isn’t causing weird things to happen especially with fuses pulled?
Since your ABS is not working, you must drive old school--brake in a straight line. With practice you can them move to trail breaking, that is major braking in straight line and soft breaking into the turn to keep the car balance and easing up gradually before it starts to over steer. We did this old school in the C1-2-3 Vettes.
Since your ABS is not working, you must drive old school--brake in a straight line. With practice you can them move to trail breaking, that is major braking in straight line and soft breaking into the turn to keep the car balance and easing up gradually before it starts to over steer. We did this old school in the C1-2-3 Vettes.
Which is what I think is the most likely culprit for my looping, judging by it happening when going into a turn each time. That’s a skill that is a work in progress.
How are your shocks? I had the same issue, always on corner entry, before apex and still coming off brake and turning in the wheel, sometimes the rear would step out.
I installed 1-way adjustable (rebound only) shocks and started with 11 clicks on front and rear. The issue was greatly diminished but still present a little bit. I stiffened the rear to 9 clicks and the car handles perfect now. Ideally you have multi-way adjustable shocks for rebound AND compression but those get into $$$
I have a 98 so it never had the active handling to begin with. The age and condition of my old shocks made the oversteer situation unpredictable. I never once had the car step out after apex once I was on the gas.
How are your shocks? I had the same issue, always on corner entry, before apex and still coming off brake and turning in the wheel, sometimes the rear would step out.
I installed 1-way adjustable (rebound only) shocks and started with 11 clicks on front and rear. The issue was greatly diminished but still present a little bit. I stiffened the rear to 9 clicks and the car handles perfect now. Ideally you have multi-way adjustable shocks for rebound AND compression but those get into $$$
I have a 98 so it never had the active handling to begin with. The age and condition of my old shocks made the oversteer situation unpredictable. I never once had the car step out after apex once I was on the gas. https://www.youtube.com/watch?v=OI3KdoBqzhc
I feel like what I saw in your video is similar to what I experience. The shocks are fairly old and this car sat for some amount of time before I acquired it. It was abandoned at a garage. I have them on the list to replace when I put on my C5Z leaf springs. I was thinking DRM Bilsteins because I don’t really want adjustable but could also spring for the adjustable koni yellows.
It seems like in your video when you let off the gas and started turning in, the rear end got light and came around. So you’re saying your shocks were essentially unloading too quickly causing nose dive and a light rear end?
In my case one of the rear shocks was completely gone, could move it freely in and out by hand. The others were not much better.
I got the ridetech HQ fox shocks from strano, it's what sam recommend and I have been very satisfied with them. I wouldn't bother with non-adjustable shocks if you are doing any kind of performance driving. Even if you only set them once and never fiddle with them again, you have lost nothing. But it provides a very powerful tuning tool, especially if you later decide to change the spring and ARB. Like that Blayze article says, the whole suspension functions as one system. So if you only have one way adjust like the HQ, instead of increasing front compression you can increase rear rebound... Instead of increasing the load on the outside front, you are increasing it on the inside rear.
There are a lot of good books on the subject, I read and would recommend Inside Racing Technology from Paul Haney, and How To Build A High Performance Miata from Keith Tanner. Also of course what works for one driver may not work for another. You need to get the car setup for your own driving style and the tracks you go to.
Originally Posted by Bryan144
It seems like in your video when you let off the gas and started turning in, the rear end got light and came around. So you’re saying your shocks were essentially unloading too quickly causing nose dive and a light rear end?
When turning in, you are compressing the outside tire and rebounding the inside tire. The shocks control the force on the tire during the change. When the car is stable in a long smooth sweeper, with constant speed (maintenance throttle) and no wheel input (you can install "the club" and have a coffee break) the shocks are doing nothing: you can take them off and throw them away! Just dead weight! Then when you unwind the wheel, the shocks do the opposite: rebound on the outside and compression on the inside.
In this case is the rear shock could not control that weight transfer, so when the car hit some small bump (and there is always some bumps in the road) the tire was already close to it's limit and it cause the traction to be lost. A sudden large compression that the suspension couldn't do anything with other than make the entire car bounce.
There are so many variables in play. What is your experience level? Have you had success with previous cars but your Vette is giving you troubles? Worn equipment and improper driving technique together are a recipe for frustration. Sure, you can get better tires (NT01s are very good), proper alignment (PFADT specs), and shocks (Koni yellows on my Z) but if you're braking and power application are not timed properly you can end up facing the wrong way easily. I threw my car all over Az Motorsports Park. Luckily it's very forgiving. I was having trouble grasping the basics until I stumbled onto a YouTube Tutorial by Scott Mansell. His Driver61 series is definitely worth a look. Very good explanations of trail braking, turn-in, proper passing etc. After applying some of his techniques I can say I improved from being an unpredictable rowdy driver to a somewhat mediocre hobbyist. LOL! My goal next season is to progress to "good". Seat time, seat time and more seat time.
There are so many variables in play. What is your experience level? Have you had success with previous cars but your Vette is giving you troubles? Worn equipment and improper driving technique together are a recipe for frustration. Sure, you can get better tires (NT01s are very good), proper alignment (PFADT specs), and shocks (Koni yellows on my Z) but if you're braking and power application are not timed properly you can end up facing the wrong way easily. I threw my car all over Az Motorsports Park. Luckily it's very forgiving. I was having trouble grasping the basics until I stumbled onto a YouTube Tutorial by Scott Mansell. His Driver61 series is definitely worth a look. Very good explanations of trail braking, turn-in, proper passing etc. After applying some of his techniques I can say I improved from being an unpredictable rowdy driver to a somewhat mediocre hobbyist. LOL! My goal next season is to progress to "good". Seat time, seat time and more seat time.
I would agree with what you’re saying, I’m not claiming to be an expert. In fact, I’m novice at best. I’ve had a few corvettes and other cars but the only car I’ve consistently tracked was an S550 GT w/ track pack and now this C5.
im not the type to throw parts at something (even though it could be part of the answer since the car is older and higher mileage).. I think my inputs just aren’t quite smooth/timed correctly yet. Constantly trying to get more seat time but work takes up a good bit of that 😂 I’ll be sure to look up that YouTube channel and check it out, always willing to learn!
In my case one of the rear shocks was completely gone, could move it freely in and out by hand. The others were not much better.
I got the ridetech HQ fox shocks from strano, it's what sam recommend and I have been very satisfied with them. I wouldn't bother with non-adjustable shocks if you are doing any kind of performance driving. Even if you only set them once and never fiddle with them again, you have lost nothing. But it provides a very powerful tuning tool, especially if you later decide to change the spring and ARB. Like that Blayze article says, the whole suspension functions as one system. So if you only have one way adjust like the HQ, instead of increasing front compression you can increase rear rebound... Instead of increasing the load on the outside front, you are increasing it on the inside rear.
There are a lot of good books on the subject, I read and would recommend Inside Racing Technology from Paul Haney, and How To Build A High Performance Miata from Keith Tanner. Also of course what works for one driver may not work for another. You need to get the car setup for your own driving style and the tracks you go to.
When turning in, you are compressing the outside tire and rebounding the inside tire. The shocks control the force on the tire during the change. When the car is stable in a long smooth sweeper, with constant speed (maintenance throttle) and no wheel input (you can install "the club" and have a coffee break) the shocks are doing nothing: you can take them off and throw them away! Just dead weight! Then when you unwind the wheel, the shocks do the opposite: rebound on the outside and compression on the inside.
In this case is the rear shock could not control that weight transfer, so when the car hit some small bump (and there is always some bumps in the road) the tire was already close to it's limit and it cause the traction to be lost. A sudden large compression that the suspension couldn't do anything with other than make the entire car bounce.
good information- I’m sure it’s a combination of worn equipment and poor technique. Definitely still a beginner in this with only maybe 10 track days and 5 autox events. Not a lot with an instructor though which I’m hoping to do more of next year. I’m always deciding between Sales vs. Seat Time 😂
Everyone seems to be covering the braking and skill bullet points, with some mention of setup and damper maintenance
I'd like to ask that you inspect your rear toe links and the lower control arm cam bolts
The reason I suggest this, is that after about 4000mi on track with my MR2, she developed this weird "wiggle/waggle" sensation when cornering. I could definitely feel the car had rear steer, and it was only when turning to the right- anyway, it was that my driver rear toe link had worked loose and was allowing toe changes under suspension cycling
May or may not be applicable here, but its easy enough to check and rule out
This is me during my "rookie" first season. Turn 8 @ AMP. This progressed into a "Tank Slapper" but I managed to keep it on track and in the proper direction! That turn kicked my *** for several track days but once I figured it out (very late apex) my times and confidence improved dramatically.
^This. Different vehicle, my Jeep runs a 4 link rear suspension. It is very easy to tell when the upper link bushings are getting soft, the rear gets a distinct butt wobble under braking or acceleration.
This is me during my "rookie" first season. Turn 8 @ AMP. This progressed into a "Tank Slapper" but I managed to keep it on track and in the proper direction! That turn kicked my *** for several track days but once I figured it out (very late apex) my times and confidence improved dramatically.
Snap Oversteer EBCM/ABS Track Use
