Suns_PSD

Bill, is the most positive rear castor I can get the best, or should I aim for a range as opposed to just going as far positive as I can?

I assume I can utilize the same technique I used on the front of my car (I mentioned it in our roadracing thread) to get the most negative camber and positive castor I can before I head to the alignment shop for a final clean up?

Please advise as I can't find anyone else that can answer this question.

rikhek

The troll returns. Dave, you just can't help yourself can you? I thought you might have turned over a new leaf after you deleted your troll post in this thread yesterday.

Hard to imagine what enjoyment you get out of trolling me when I'm just trying to help people. I haven't responded to your numerous troll posts against me since you started your nonsense but thought it was time to speak my peace.

Many, many people have seen my spin video and you're the only guy that makes the asinine statement that I was going too fast for the corner. Since setting the car up properly I've repeatedly taken the same corner at 20 mph faster with no drama.

Maybe someone who's seen my video will chime in addressing your "analysis".

I also note you once again get your stupid "driving outside the envelop on a public roadway" comment in along with your decree that "thou shalt not drive on public roadways with nannies off". I'm driving line of sight and not endangering the public.....

Trolls like you are the reason many don't contribute helpful information on the Forum.

No response is needed on your part but I know that won't happen. Your passive-aggressive condescending comment at the end of your post supporting my input just doesn't cut it. People see right through your BS. You just can't help yourself......

davepl

Fortunately I don't need your permission to post. And my Helpful count doesn't look very trolly compared to yours. And "troll posts" don't contain multiple caveats (look it up), cautions that I don't know everything, that I could be wrong, offer you specific praise, and so on. You should read my post again, actually.

Look, you crashed your car and I feel sorry for you for that. But your mission to absolve yourself of all guilt of that by blaming rear caster is a weird mission. And attacking anyone who doesn't adhere to your little manifesto of innocence is weak.

Did you include that video with your $19,000 insurance claim as proof that it was the car's fault I wonder? My copy doesn't show anything that implicates the car. So how'd you explain your 4x4 adventure to them? What were you avoiding?

I was talking about oversteer and camber, you can only talk about me for some reason. Consider that when discussing who's the real troll, pal... Or keep it to technical issue and shut up about me for a while. I don't need your love.

Kyflyer

This thread had been a great help to me and the links provided, images, and the wealth of knowledge is fantastic. I have saved a lot of this information and will discuss it with my dealer, particularly the all wheel alignment information. Since our corvette club sponsor is where I purchased my Z06 I hope to be able to discuss this with him and encourage him to invest in the equipment needed to do this. We have several members with C7 Z06s and it may be a profitable investment for him if enough of us purchase tires through him and have them mounted, aligned, and balanced. It seems most of us are "streeties" that occasionally track. Thanks to Rick and other positive contributors!

Oleman

Go on You Tube and you can see what Randy is commenting on while testing is pretty interesting.

dmaxx3500

finally somebody that can drive

most roads have a crown ,high in the center,down to the curbs on each side,,this is to let water drain,

Dfwz06

Go try that in your c7z and see how it works out. Lol

rikhek

I've thought about the pros and cons of reposting my spin video and decided to repost.

The pros being it will help fellow owners by allowing viewing of my snap oversteer incident to demonstrate the issue and hopefully prevent others from a similar event.

The cons being it will divert the technical conversation of this thread to the, "you got what you deserved by endangering the public driving that fast on a public road" and the "you shouldn't drive on public streets with the nannies off"folks. FWIW, I believe I was driving at a "safe" speed as utilizing line of sight. This is why I slowed significantly for the corner.

Dave396LT states in his post above individuals who have experienced the phenomena of the car rotating violently to the right under hard acceleration in a straight line is due to driver error. I don't agree and believe many who have experienced this trait are capable drivers.

He has also maintaines that my spin was due to driver error from attempting to navigate the corner too fast.

Factual information pertinent to my spin:

1. Speed limit on the road is 50 mph. I was doing 64 mph in 3rd gear (M7) with minimal maintenance throttle application at low RPMs when it let go.

2. Tires were in great shape and hot. Ambient temp was around 90 degrees.

3. Road surface was not a significant factor. No dirt, rocks, oil, water, inundations, surface material, etc. Shadows incorrectly suggest oil or tar on the road. The road is slightly off camber but nothing unusual.

4. Driving mode was Sport 2.

I attribute the main contributing factor to be improper rear caster setting. Post incident caster was measured at 0.0 degrees on one side and -0.8 degrees on the other. Settings were as delivered from the factory. Significant testing has determined the optimum setting to be symmetrical at +0.7 degrees.

I'll let you view and make own analysis. Sharing your thoughts is welcomed, hopefully related to the technical aspects of this thread.

Rick

mtaylor

Yeah definitely something odd about that spin IE not driver error.
You don't hear any increase in engine noise, with a minimal amount of steering angle.

Edwardz

I agree that Rilheks situation was completely different than the one with that red Corvette.

silver74vette

Rikhek,

Thank you for posting. I think this does a good job at differentiating the snap oversteer and the rotation under hard straight acceleration.

Very scary, glad you are OK and I will spend the $$ to ensure my car is aligned properly.

Thanks, Chris

123sugey

Pretty much what I thought after watching the video a few times. Don't need to watch it anymore.

Les

I only saw the video once before it was removed. My thoughts now are as they were then. My initial reaction was that there had to have been something slick on the road- either oiled down or a layer of silt that made you lose grip. Absent that, and after reading your summary of conditions, I just can't see how someone could conclude that it was your fault. That only leaves having something wrong with the car as the cause- alignment being the obvious choice.

Don't worry about Dave. I think, now that 3 Z06ZR1 has been banned, he feels that somebody needs to fill his shoes.

h3mpking

[QUOTE=rikhek;1593619538]I've thought about the pros and cons of reposting my spin video and decided to repost.

Wow!! That is concerning. You didn't stab the throttle, brake hard, or anything to cause that snap.

Adam Silver05

I'm not an expert but that video didn't look too fast for the turn (except for the resulting crash). At second # 18 in the video it looks like oil or fluid on the road. Nobody will convince me (based on that video) that driver technique was the culprit. I think that video is definitely a snap oversteer situation (and upsetting to watch). If the road was indeed clean, the car 100% seems to me to be the cause - not the driver. If that road had oil at second # 18, any car would have had that spin. I do think some percentage of the C7Z has major issues with freaky behavior. BTW, I am sketched enough that I ordered 19" rear wheels and Nittos all around today to try to make my car less likely to have the evil monkey! I am hoping that softer compound, non-runflat and larger sidewall will slow down things back there.

pkincy

I have watched the spin a great number of times and it appears that the spin initiates just as you are getting off the brakes (you were trail braking) and begins as you were getting on the gas. Normally that getting on the gas would transfer weight back to the rear to help plant it, but it appears that happened a bit too late. Also the steering angle and g forces increased greatly just as you were getting off the brakes (so weight was still on the front of the car). I have no doubt that your rear caster setting helped cause the spin and in fact made it a snap spin rather than simple tail out, but releasing the brakes a bit earlier and/or getting on the gas sooner/harder to plant the rear and not cranking the wheel so much while still having an unloaded rear axle put you in the weeds.

So my take from the PDR is a bit of overcooking while trail braking caused a spin that was exacerbated by the alignment settings.

Now it would be most helpful to have a PDR recording of the folks that are getting spun out while going dead straight.

rikhek

I immediately went back to that section, parked the car and spent significant time walking the road. I looked at the road very carefully. Nothing there...

rikhek

Valid point and one of many contributing factors. I agree transferring more weight to the rear with throttle application would have helped.

I've thought about the lightly weighted rear end situation since the spin. Not to be defensive but after trail braking the tach shows I had consistent maintenance throttle. You can see one green throttle position light come on right before it lets go. I believe the tach suggests I was right on the border of the green indicator lighting when the light blips. Never the less more weight would have been beneficial.

pkincy

You are correct as the throttle was going on. But it appears that up to 45 deg of steering was cranked in and the G forces immediately jumped to 1.25G max. Lets assume that the rear was aligned correctly and wasn't going to contribute to ugly snap oversteer. In that case if you had needed 45 deg of steering to make the turn and you had planned on trail braking you would have dialed in 20 deg of steering and expected the tail to step out about 20-25 deg to give you the total 45 degree of turning.

I had an interesting experience in years ago in what was billed as the California State Autox Championship that was held at Buttonwillow which is a race track. To make it an autox they had put cones at track out in many turns to tighten the course and then put a chicane in the middle of the long straight. Actually that made the course much harder to handle than running the full straight. I ended up having one of those very good days and ran some good times for my class and would have placed 3rd in a very large very well represented Corvette SS class even in my F Stock Camaro.

After the event we had a barbecue and the corner works for that chicane came over and told me they expected me to spin evey time I came to that chicane. What I was doing was trail braking with gently steering input to allow the rear to step out about 45 degrees and than getting in the throttle rather violently to settle the rear and get it to hook, allowing me to have the car rotated and getting through that slow part of the straight as quickly as possible.

You were very close to being able to catch that spin but the alignment made that impossible. BTW, if Randy Probst gets caught out by bad alignment causing snap oversteer, you are in very good company.

Bill Dearborn

No. Here are the settings from the FSM.



You can see the alignment machine will read green within + or - 0.6 deg of camber in the front and rear while it will read red in the front if the cross camber is greater than 0.3 deg while they have a dash for the rear cross camber. That means camber can vary from -0.5 deg to -1.7 in the rear. Notice they have different camber settings for the front with -0.6 for the driver front and -0.9 for the passenger front so camber there can vary between 0.0 to -1.2 on the driver side or -0.3 to -1.5 on the passenger side. The most positive numbers with close to 0 toe or a smidge of toe in will give great wear but may not provide the best handling.

If you read the track alignment settings you will notice the recommended camber is -2.0 deg all the way around which is considerably more than the street specs. For what is worth my car came with -1.2 at all 4 wheels. I don't know what the rear caster was since nobody had a gauge to measure it before I had the car aligned (without rear caster measurement). The rear caster must be pretty close because I haven't had any unusual snap oversteer at VIR, Watkins Glen or Carolina Motorsports Park or at the one autocross I ran with my two grandsons.

Bill