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Why do C7 Z06's pull to the right violently when breaking loose...WTF

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Why do C7 Z06's pull to the right violently when breaking loose...WTF

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Old 12-07-2016, 10:59 AM
  #141  
spearfish25
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If someone can replicate this phenomenon easily, why not post up a combo of PDR footage and an interior GoPro to show it first hand? I'm very interested to see what everyone is describing. The red vette going into the woods looks like nothing more than a planted, slow right foot and no or slow countersteer with the hands. Having auto crossed the car with all nannies off, I've found it to be extremely predictable. The only thing I haven't done is just smashed the gas pedal to the floor and surfed a huge burnout through two gears which seems like what some are describing as the inciting factor here. Rilheks now removed video showed a completely different situation which is somehow getting wrapped into this discussion as well.

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Old 12-07-2016, 11:50 AM
  #142  
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I did about 6 launches yesterday with my '17 Z, to try and see this happen. It did not affect the direction at all. It did, however, spin the tires too much in my opinion. I used launch control each time in track mode and then in comp 1 mode as well(no noticeable difference) . Seems to act the same each time, and shifted to second bogging the car after the tires spun in first gear. tires were hot and ambient temps around 65 degrees. I did PDR of each and it's just not pretty with way too much tire spin. My '15 model did not allow this much tire spin and shifting to second, bogging somewhat. I ran my SS street setup for this. Definitely did not pull in either direction, stayed straight.
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Old 12-07-2016, 11:53 AM
  #143  
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You ran MT SS tires? That changes it
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Old 12-07-2016, 11:55 AM
  #144  
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As stated in a prior post there are two different phenomena being discussed in this thread:

1. The car violently rotating to the right during aggressive straight line acceleration and;

2. The car randomly exhibiting snap oversteer while cornering.

I've been sharing my experience with the second issue, snap oversteer while navigating a turn. It happened to me while navigating a corner on a twisty country road at a relatively mild speed. My spin resulted in cosmetic damage to the tune of $19,000 to repair.

I have nothing to offer on the rotation to the right issue mentioned as #1 above as I don't drive my car in this fashion.

A solution to the snap oversteer was provided to me from Mike Levitas who owns TPC Racing and DSC Sport. Mike is a 24 Hour Daytona Winner and excellent race car driver. Mike has done extensive work determining optimum alignment for the C7 chassis to eliminate this trait.

Mike experienced the snap oversteer in his 2016 C7Z while driving on the street in a relatively mild manner. It greatly troubled him as he almost wrecked his car. Randy Pobst also experienced the snap oversteer numerous times while testing the car. Mike shared the fruits of his labor with myself and a good number of road racers and aggressive "twisty" road drivers.

Since setting my 2015 C7Z and my new 2017 C7Z to the street/track specifications recommended by Mike I have NOT ONCE experienced the snap oversteer phenomena.

Mike strongly believes the less than acceptable and nonsymetrical alignment provided from the factory is the culprit. The most significant setting being the rear caster. My cars both came from the factory with none of the alignment specs being symetrical. The rear caster on both my cars was 0.0 degrees on one side and -0.8 on the other. Not good.

Mike has determined the car is world class when set up properly. He's determined what he feels are the best settings as provided below. Very important is setting the rear caster at +0.7 degress on both sides. FWIW, I like +0.8 better than +0.7 but it's not really a noticeable difference unless you're at 10/10 and even then it's subtle.

You DO NOT need a DSC Sport Controller to realize the benefits from these settings. However, for full disclosure I have a controller on my race car and C7Z and the performance upgrade it provides is remarkable.

Please note I'm only offering input to help others avoid what happend to me, Mike, Randy and numerous others. I've no agenda or anything to gain personally, just trying to help....

Rick



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Old 12-07-2016, 12:26 PM
  #145  
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^ Rick, who did you have set your alignment?

And did you have them use 'loctite' etc. to try and stop the settings from 'shifting'?

TIA,
Bish
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Old 12-07-2016, 12:43 PM
  #146  
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Originally Posted by thebishman View Post
^ Rick, who did you have set your alignment?

And did you have them use 'loctite' etc. to try and stop the settings from 'shifting'?

TIA,
Bish
Hey Bish,

Believe it or not I have a guy at my dealer who does my alignments for me. He's a fellow racer and takes pride in his work. Only problem is he's been promoted to a management position. However, he still does my alignments on his own time after hours at the dealership.

I've nor he has lock tighted the eccentrics. He cranks them down with a cheater pipe beyond the specified torque and then marks the position with a paint pen. I've never had an issue.

Rick

P.S. I think you saw I just got rid of my somewhat troublesome 2015 for a 2017?

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Old 12-07-2016, 01:35 PM
  #147  
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Originally Posted by rikhek View Post
As stated in a prior post there are two different phenomena being discussed in this thread:

1. The car violently rotating to the right during aggressive straight line acceleration and;

2. The car randomly exhibiting snap oversteer while cornering.

I've been sharing my experience with the second issue, snap oversteer while navigating a turn. It happened to me while navigating a corner on a twisty country road at a relatively mild speed. My spin resulted in cosmetic damage to the tune of $19,000 to repair.

I have nothing to offer on the rotation to the right issue mentioned as #1 above as I don't drive my car in this fashion.

A solution to the snap oversteer was provided to me from Mike Levitas who owns TPC Racing and DSC Sport. Mike is a 24 Hour Daytona Winner and excellent race car driver. Mike has done extensive work determining optimum alignment for the C7 chassis to eliminate this trait.

Mike experienced the snap oversteer in his 2016 C7Z while driving on the street in a relatively mild manner. It greatly troubled him as he almost wrecked his car. Randy Pobst also experienced the snap oversteer numerous times while testing the car. Mike shared the fruits of his labor with myself and a good number of road racers and aggressive "twisty" road drivers.

Since setting my 2015 C7Z and my new 2017 C7Z to the street/track specifications recommended by Mike I have NOT ONCE experienced the snap oversteer phenomena.

Mike strongly believes the less than acceptable and nonsymetrical alignment provided from the factory is the culprit. The most significant setting being the rear caster. My cars both came from the factory with none of the alignment specs being symetrical. The rear caster on both my cars was 0.0 degrees on one side and -0.8 on the other. Not good.

Mike has determined the car is world class when set up properly. He's determined what he feels are the best settings as provided below. Very important is setting the rear caster at +0.7 degress on both sides. FWIW, I like +0.8 better than +0.7 but it's not really a noticeable difference unless you're at 10/10 and even then it's subtle.

You DO NOT need a DSC Sport Controller to realize the benefits from these settings. However, for full disclosure I have a controller on my race car and C7Z and the performance upgrade it provides is remarkable.

Please note I'm only offering input to help others avoid what happend to me, Mike, Randy and numerous others. I've no agenda or anything to gain personally, just trying to help....

Rick


The problem is it is extremely difficult (nigh impossible) to find a dealer or speed shop that can measure/adjust rear castor...

All my local dealers shops have no clue, which is truly shameful since the C7 is now in it's 3rd production year.

Last edited by Newton06; 12-07-2016 at 01:36 PM.
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Old 12-07-2016, 02:09 PM
  #148  
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How is rear castor adjusted? Does anyone know if the adjustment is the same on a C6?

The race tires people always say to make front castor as positive as possible. Is the same true of the rear, or is the range suggested below, were it really needs to stay in the rear?
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Old 12-07-2016, 02:11 PM
  #149  
Bill Dearborn
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I only did one day on an autocross course so don't have a lot of launches recorded but this is one that I took when running in Sport 1 with a little rain falling. Sometimes you can hear PTM putting the exhaust when the tires are breaking loose (which they did on almost every run whether or not it was raining). There was no hint of the rear end kicking out to the rear on the launches or when accelerating off turns at wide open throttle in low gear.

This is one that was taken when it was raining quite heavily and I was running the car in Wet Mode.


The last run of the day was when it was a little drier and I was running Sport 1 again.

In none of those runs even did I have any issue with the rear end breaking to the right.

Bill
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Old 12-07-2016, 02:12 PM
  #150  
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How much faster will the camber and tow wear out tires. I really dont plan on hitting the track but dont want to end up in the ditch on the street.
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Old 12-07-2016, 02:32 PM
  #151  
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Originally Posted by Newton06 View Post
The problem is it is extremely difficult (nigh impossible) to find a dealer or speed shop that can measure/adjust rear castor...

All my local dealers shops have no clue, which is truly shameful since the C7 is now in it's 3rd production year.
I am disappointed that if I buy a C7, it will be very difficult to have it aligned properly.
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Old 12-07-2016, 02:39 PM
  #152  
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Originally Posted by mtaylor View Post
How much faster will the camber and tow wear out tires. I really dont plan on hitting the track but dont want to end up in the ditch on the street.
Toe is the setting that has the most affect on tire wear followed by camber. If you have lots of negative camber and then add toe out you will make the tires wear much quicker. If you have 0 toe or toe in then the tires will not wear as fast. You can run a decent street alignment with 0 to a small amount of toe in on the street and get decent wear. Toe in in the front should help reduce pulling on pavement seams, etc. Rear caster can be set properly with a street alignment.

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Old 12-07-2016, 02:44 PM
  #153  
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Originally Posted by dead of night View Post
I am disappointed that if I buy a C7, it will be very difficult to have it aligned properly.
The difficulty comes in finding a shop that has the proper equipment. The dealership that I go to is very good but they refuse to buy the equipment called for. The guy who manages the tools told me he was not going to buy close to a thousand dollars worth of tools for just one car. The mechanic that does the Corvette alignments told me if I brought in my own tools he would set the caster. There is another dealer on the other side of Charlotte from me that used to be a Saturn dealer. They have the GM gauge but don't have the adapter which I happen to have two of now. Anybody wants the adapter made by a forum member can have it at a good price.

Bill
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Old 12-07-2016, 02:46 PM
  #154  
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Originally Posted by Bill Dearborn View Post
Toe is the setting that has the most affect on tire wear followed by camber. If you have lots of negative camber and then add toe out you will make the tires wear much quicker. If you have 0 toe or toe in then the tires will not wear as fast. You can run a decent street alignment with 0 to a small amount of toe in on the street and get decent wear. Toe in in the front should help reduce pulling on pavement seams, etc. Rear caster can be set properly with a street alignment.

Bill
so the street recomendations that were posted shouldn't cause an extreme amount of wear?

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Old 12-07-2016, 02:47 PM
  #155  
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Bill your video is on a track surface and I'm assuming with track tires.
The issues most of us have is shifting into 2nd or 3rd on the steeets with street tires. Try that without traction control on, and you'll be lucky not to crash. Do the same thing in a c6 z06 or zr1, and you'll go straight while smoking the tires.
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Old 12-07-2016, 03:39 PM
  #156  
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I am actually very interested in this conversation. I saw the comments that Randy Pobst made before and after. It appears as if alignment solved the problem for him. He was driving on a track and not launching in a straight line.
Things I would be interested in:

The eLSD can potentially allow one tire to spin much faster (when more "open") then tighten down and transfer torque quickly to the other. This would not typically happen with a conventional LSD.

Does the compressed suspension (during hard accelleration) change the geometry to add or remove toe potentially making the rear end less stable.

Does the Carbon Fiber Torque Tube remove buffering ability that shifts torque very abruptly when the engine is producing high levels of power.

The fact that drag radials seem to minimize this for the straight line issue makes me think it is a tire/ application issue in this respect.
The fact that alignment seems to effect the track (road course) performance makes me think that factory specs need to be tightened up.

My takeaway from reading this thread is that a car like the C7 Z06 needs to be set up for the kind of extreme driving you will be doing. I see the factory product as a compromise focused on road course performance which can (and does by the comments here) create issues when driving hard and straight on stock tires with an unprepared surface.

I would like to see a response from Tadge about this.

Just my opinion, Chris
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Old 12-07-2016, 03:50 PM
  #157  
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Originally Posted by dead of night View Post
I am disappointed that if I buy a C7, it will be very difficult to have it aligned properly.
Join the club.

For those of us that track our cars regularly and want the car setup properly, this issue is absurd.

I had a spin in turn 8 at VIR last month at 110 when I lost the rear end. After detailed analysis of the PDR data, it was likely due to me hitting the curbing too aggressively, too much steering angle, and lifting that caused the spin. But I'd sure as hell like to know what my rear castor is set to.

In 2.5 years I've owned the car, I can't find anyone with the tools or knowledge to check/adjust it locally. I may just have to bite the bullet & drive 5.5 hours to MD to have this shop do it.

The so-called 'dealer tool rental' program Tadge referred to once in order to obtain the GM tools without having to pay their absurd price is a joke; no dealers are aware of it or interested.

Last edited by Newton06; 12-07-2016 at 03:52 PM.
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Old 12-07-2016, 03:59 PM
  #158  
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Originally Posted by Newton06 View Post
Join the club.

For those of us that track our cars regularly and want the car setup properly, this issue is absurd.

I had a spin in turn 8 at VIR last month at 110 when I lost the rear end. After detailed analysis of the PDR data, it was likely due to me hitting the curbing too aggressively, too much steering angle, and lifting that caused the spin. But I'd sure as hell like to know what my rear castor is set to.

In 2.5 years I've owned the car, I can't find anyone with the tools or knowledge to check/adjust it locally. I may just have to bite the bullet & drive 5.5 hours to MD to have this shop do it.

The so-called 'dealer tool rental' program Tadge referred to once in order to obtain the GM tools without having to pay their absurd price is a joke; no dealers are aware of it or interested.
Hope that you and the car are OK after the spin. This is a concern I have as well. We do have a speed shop in town that will do a good alignment and spend the $ for the tool. Most auto shops can't do a decent alignment on a pickup truck, never mind a performance car.

Good luck and we would like to hear what you find after you get it checked.
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Old 12-07-2016, 04:48 PM
  #159  
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FWIW, Mike Levitas/TPC Racing told me he has about $30 in the "tool" used to check/set the rear caster. He bought a digital angle gauge from Lowe's and made an adapter bracket. He said it took him less than a half hour to make the adapter bracket used to attach the digital gauge to the car.

Also, a forum member is selling an adapter bracket he was producing for near nothing.

A number of forum members have gone the same route of the "Lowes" digital gauge to check/set their caster.

You can spend the $30 on the gauge and adapter and any half decent alignment shop can use it to hook you up.

You do not need to spend the ~$700 for the GM tool and bracket.

There are many Forum threads/posts depicting the gauges guys are using and the adapter you can make or buy from the forum member making them. It's really, really simple. All you're doing is measuring and angle.

A Google search or Forum search will provide you all the information you need.

For the hell of it I just Googled "C7 Corvette Caster" and found a wealth of info:

https://www.google.com/webhp?sourcei...orvette+caster

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Old 12-07-2016, 05:01 PM
  #160  
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While doing the search in my post above I stumbled across the Motor Trend Article where Randy Pobst retested the C7Z after the caster was properly set.

As Randy states in the article the car scared him when it was not properly set. Different story once the idiots prepping the car got it correct. It really is a hugh issue when subjecting the car to road course work or aggressive canyon/country driving. LOL, I'm not making this **** up....

http://www.motortrend.com/cars/chevr...-track-retest/
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