Steering issues, any input?
Pro
Joined: Jul 2015
Posts: 748
Likes: 222
I have driven several C7 Z06's (I've owned two, plus I did the COS at Spring Mountain) and what your describing sounds normal to me. Like all wide tired sports cars, the steering is very dependent on the road surface. Also, these tires are different animals when they are hot v. when they are cold.
Luke at Criswell is phenomenal and if he says that all is right with your car, then I would tend to believe him.
Luke at Criswell is phenomenal and if he says that all is right with your car, then I would tend to believe him.
Intermediate
Joined: Feb 2014
Posts: 41
Likes: 15
From: Indianapolis
I have driven several C7 Z06's (I've owned two, plus I did the COS at Spring Mountain) and what your describing sounds normal to me. Like all wide tired sports cars, the steering is very dependent on the road surface. Also, these tires are different animals when they are hot v. when they are cold.
Luke at Criswell is phenomenal and if he says that all is right with your car, then I would tend to believe him.
Luke at Criswell is phenomenal and if he says that all is right with your car, then I would tend to believe him.
Team Owner
Joined: Sep 1999
Posts: 41,732
Likes: 1,718
From: Springfield MO
Blaming the problem on wide tires is wrong.
I have over 50,000 miles on my C6 Z06 and it also has wide tires(275 front and 325 rear) and I have near zero tramlining(I never notice any). I did have some tramlining with the OE Goodyear's, but after new Bridgestone's(at 12,500 miles), and a GOOD alignment, all is well. Almost 40,000 miles on my Bridgstone's and they still drive straight, whether at 30 MPH or 160 MPH.
BTW, my Bridgestone's were developed specifically for the C6 Z06 as Bridgestone was after the OE suppler business(but failed to get it).
The expressway near my home is concrete and part of it has longitudinal grooves cut into the surface. They weave a little bit and different tires on my four cars react different to it. The 205/70 Goodyear Integrity tires on my 1956 and 1964 Corvettes will wander side to side trying to follow the very shallow and narrow grooves in the pavement. The OE 205/60 Goodyear LS tires on my Mercedes tried to follow the grooves, but when I put Michelin Pilot tires on the Mercedes, it went away, only to return when I put Goodyear LS tires back on. BTW, the Goodyear's on my Mercedes were terrible in the curves, but the Michelins were great, but the Michelins were noisy and had terrible wet weather manners, which is why I dumped them.
My C5 had all the problems you C7 Z06 owners are describing, even though it had 245 front and 275 rear tires. When I replaced the OE Goodyear's with Michelin A/S tires(same size) 95% of the tramlining went away.
With the WIDE OE Goodyear tires on my C6 Z06, they also tried to follow the grooves, but not near as bad as the NARROW 205 tires on my other cars. The WIDE Bridgestone tires I now have on my Z06 do not follow the grooves. Not one iota.
I have over 50,000 miles on my C6 Z06 and it also has wide tires(275 front and 325 rear) and I have near zero tramlining(I never notice any). I did have some tramlining with the OE Goodyear's, but after new Bridgestone's(at 12,500 miles), and a GOOD alignment, all is well. Almost 40,000 miles on my Bridgstone's and they still drive straight, whether at 30 MPH or 160 MPH.
BTW, my Bridgestone's were developed specifically for the C6 Z06 as Bridgestone was after the OE suppler business(but failed to get it).
The expressway near my home is concrete and part of it has longitudinal grooves cut into the surface. They weave a little bit and different tires on my four cars react different to it. The 205/70 Goodyear Integrity tires on my 1956 and 1964 Corvettes will wander side to side trying to follow the very shallow and narrow grooves in the pavement. The OE 205/60 Goodyear LS tires on my Mercedes tried to follow the grooves, but when I put Michelin Pilot tires on the Mercedes, it went away, only to return when I put Goodyear LS tires back on. BTW, the Goodyear's on my Mercedes were terrible in the curves, but the Michelins were great, but the Michelins were noisy and had terrible wet weather manners, which is why I dumped them.
My C5 had all the problems you C7 Z06 owners are describing, even though it had 245 front and 275 rear tires. When I replaced the OE Goodyear's with Michelin A/S tires(same size) 95% of the tramlining went away.
With the WIDE OE Goodyear tires on my C6 Z06, they also tried to follow the grooves, but not near as bad as the NARROW 205 tires on my other cars. The WIDE Bridgestone tires I now have on my Z06 do not follow the grooves. Not one iota.
Last edited by JoesC5; Nov 4, 2016 at 05:18 PM.
Safety Car
Joined: Jun 2003
Posts: 4,250
Likes: 656
From: San Diego Ca
Have you put the tech behind the wheel to have him experience what you are feeling? Or a service manager or service writer that is an experienced Corvette driver? That would go a long way to help differentiate normal wide low aspect ratio tramlining from a bad steering rack or loose Ball Joint or ?
1st Gear
Joined: Nov 2019
Posts: 1
Likes: 0
Here you go:
Front
Left -1.6 camber / 6.8 degrees caster / -0.03 degrees toe
Right -1.7 camber / 7.1 degrees caster / -0.03 degrees toe
Rear
Left -1.2 camber / 0.8 degrees caster / -0.03 degrees toe
Right -1.3 camber / 0.8 degrees caster / -0.03 degrees toe
Which is basically exactly what I asked for, or as close as can reasonably be done. FWIW the car feels more confident while cornering and doesn't feel any less stable in a straight line. I was wearing out the outside shoulder of my front tires on the factory alignment so the extra camber should help.
I would also point out that GM's own tech materials suggest that if a car has a pulling issue that adjusting cross caster and cross camber is OK once the other possible causes have been explored. None the less it concerns me when you have to take such measures with the car.
I have also noticed that the car behaves much better in TRACK mode than TOURING mode. But track mode would likely break your back over a long haul drive. I think part of the solution may be a DSC SPORT controller for the shocks so I can make SPORT mode just as hard as track but also tune the shock to soften for high-velocity compression to keep the ride comfort there.
THANKS EVERYONE!!!!
Front
Left -1.6 camber / 6.8 degrees caster / -0.03 degrees toe
Right -1.7 camber / 7.1 degrees caster / -0.03 degrees toe
Rear
Left -1.2 camber / 0.8 degrees caster / -0.03 degrees toe
Right -1.3 camber / 0.8 degrees caster / -0.03 degrees toe
Which is basically exactly what I asked for, or as close as can reasonably be done. FWIW the car feels more confident while cornering and doesn't feel any less stable in a straight line. I was wearing out the outside shoulder of my front tires on the factory alignment so the extra camber should help.
I would also point out that GM's own tech materials suggest that if a car has a pulling issue that adjusting cross caster and cross camber is OK once the other possible causes have been explored. None the less it concerns me when you have to take such measures with the car.
I have also noticed that the car behaves much better in TRACK mode than TOURING mode. But track mode would likely break your back over a long haul drive. I think part of the solution may be a DSC SPORT controller for the shocks so I can make SPORT mode just as hard as track but also tune the shock to soften for high-velocity compression to keep the ride comfort there.
THANKS EVERYONE!!!!
Drifting
Joined: Jul 2019
Posts: 1,325
Likes: 701
In Tour my Z can be a bit "squirmy" just because the steering input is so light but other then that mine feels really planted...what tires are you running? Cup 2's are rather more "darty" then other non track tires.
Safety Car
Joined: Dec 2012
Posts: 3,858
Likes: 1,863
From: St. Louis Metro East IL
Try setting your steering mode to Sport or Track instead of Link to Drive Mode. You may not like / need the full power steering boost provided in Tour mode. I ran my Z51 and now my GS in Track for steering.
Tech Contributor
Joined: Oct 1999
Posts: 41,058
Likes: 9,820
From: Charlotte, NC (formerly Endicott, NY)
Tramlining on pavement imperfections can be reduced by making sure there is a small amount of toe Vs 0 toe or toe out. The GM spec is for +0.1 degrees of toe in plus or minus 0.2 degrees so you could have slight toe out and get some tramlining.
As for pulling with the crown of the road the car will tend to pull toward the side with the most positive camber or the least positive caster. If you look at the GM specs for the wide body cars you will see they specify -0.6 degrees camber on the driver side and -0.9 degrees camber on the passenger side which would tend to offset the natural pull a car would get from riding on the right side of the road crown. Of course this will vary with the crown and you will get more pull if riding on the left side of the crown. However, there is a tolerance of plus or minus 0.6 degrees of camber on each side.
Caster is spec'd at +7.4 degrees on each side with a tolerance of plus or minus 0.6 degrees. Cross caster is spec'd at 0.0 degrees with a tolerance of plus or minus 0.6 degrees.
I run my 15 Z06 with varying amounts of camber depending on whether I am tracking the car with slicks or street tires or just driving on the street during the off season. I try to have left and right side camber and caster as close as I can possibly get them to each other with between 1/32 and 2/32 of total toe in. With those settings the car usually drives straight with minimal pull to one side of the other unless the crown shifts suddenly. I can take my hands off the steering wheel and the car will drive straight for some distance.
One way to see if the pull is too much is to drive the car on a straight road with your hands at the 3 and 9 positions and then just relax your grip so the car is steering itself. See how long a distance it can travel before it moves out of it's lane. You may find the car will drift back and forth across it's lane without going out of the lane. That is acceptable and if you are holding the wheel all that would be necessary to stop the drift would be to hold the wheel steady.
Bill
As for pulling with the crown of the road the car will tend to pull toward the side with the most positive camber or the least positive caster. If you look at the GM specs for the wide body cars you will see they specify -0.6 degrees camber on the driver side and -0.9 degrees camber on the passenger side which would tend to offset the natural pull a car would get from riding on the right side of the road crown. Of course this will vary with the crown and you will get more pull if riding on the left side of the crown. However, there is a tolerance of plus or minus 0.6 degrees of camber on each side.
Caster is spec'd at +7.4 degrees on each side with a tolerance of plus or minus 0.6 degrees. Cross caster is spec'd at 0.0 degrees with a tolerance of plus or minus 0.6 degrees.
I run my 15 Z06 with varying amounts of camber depending on whether I am tracking the car with slicks or street tires or just driving on the street during the off season. I try to have left and right side camber and caster as close as I can possibly get them to each other with between 1/32 and 2/32 of total toe in. With those settings the car usually drives straight with minimal pull to one side of the other unless the crown shifts suddenly. I can take my hands off the steering wheel and the car will drive straight for some distance.
One way to see if the pull is too much is to drive the car on a straight road with your hands at the 3 and 9 positions and then just relax your grip so the car is steering itself. See how long a distance it can travel before it moves out of it's lane. You may find the car will drift back and forth across it's lane without going out of the lane. That is acceptable and if you are holding the wheel all that would be necessary to stop the drift would be to hold the wheel steady.
Bill
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Melting Slicks
Joined: Jul 2011
Posts: 2,055
Likes: 864
From: So Cal
2017 Z07 w/PSS ZPs running 30-31 cold and 34ish hot. Even tire wear, tracks straight, stops straight every time. But, tramlining can actually be hazardous in Tour Mode. SoCal has been expanding their freeways to the center to create more car pool lanes. So they are adding small sections that create lines close to the concrete barriers (or K rails) on the inside to enable the widening. Sometimes those lines are two feet from the barriers and in Tour Mode the car would very suddenly tramline left in a heartbeat.
But in Sport Mode the tramlining is minimal and it rarely “darts” suddenly. So I generally keep the steering in Sport mode and occasionally in Track Mode but rarely in Tour Mode.