This question is probably not couched in technical terms, but my C7 seems very loose in its handling. At 1600 miles the front end darts all over the road and at highway speeds when I hit a bump the rear end will jump sideways. Alignment has been checked and is within specification for camber and toe both front and back. Caster has not been checked. Could bad caster settings cause the car to be as "squirrelly" as it feels. Something definitely feels wrong. I have never had a car feel as out of control when hitting a bump at highway speeds. Any thoughts would be greatly appreciated.

 

May seem elementary, but have you checked the tire pressure? I have found on both bikes and cars that out of whack air pressure makes a huge difference on the way it feels in the corners. I am sure you have checked it but thought I would bring it up just in case.

 

When my tires are very cold, the car feels a bit twitchy over bumps but nothing like what you describe. Check tire pressures and if it is still feeling this way when the tires are hot, take it to the dealer.

 

Almost sounds like it's tramlining. Are you running stock tires? Tire pressure as mentioned could be an issue as well. Do the roads you are driving on have the lines cut into them running the direction of travel? Is the pavement uneven? Lastly, is this a base model or a Z51? I'd expect the base model to be a bit "looser" than the Z51 but not to the extent that you are describing. I can't help but wonder if this has more to do with the pavement than the car itself. One other thought would be a bad shock.

 

Tire pressures are at 30 lbs. C7 is Z51. Am running stock tires. The sensation happens on all road surfaces but is pronounced at highway speeds. I have taken it to the dealer and had the alignment checked. The only alignment spec not checked was caster. I am also of the opinion it could be a bad shock or bad anti-sway bar. But it is hard to believe this would be the case at 1600 miles. I am stumped. The car just feels loose and certainly not like a sports car should feel, expecially a Corvette.

 

Maybe put a torque wrench on the suspension bolts and see if everything is tight. I had the control arm carrier fail at the track and this is what happened. It is possible during assembly that they just didn't tighten down some suspension pieces and your getting movement.

 

Just because the alignment is within spec does not mean it is correct. You could have (slight) tow out on left front and (slight) toe in on right front and still be in spec. With caster at the high end of the scale the car would be more darty.

 

I notice your location is OH, and I feel your pain. We both live in the state with the worst roads in the US. I'm not a C7 owner, but the sensation you describe was exactly how I described the handling of my C6 GS when I picked it up last year--I described it as 'darty'. It's mainly a function of the wide tires and the stiff sidewalls of the RFTs fighting the road imperfections. I was initially disappointed with the handling of my car, simply because I was expecting it to be 'fun' but ended up feeling like driving it on our cr@ppy roads was more like work!

I had my alignment checked in the first 1000 miles, too, and the dealer confirmed it was "in spec", but those are a very broad set of numbers from GM that are meant to maximize handling and grip and can be improved for street use. Two things are gonna make you happy with your car's driving manners: 1) have the alignment set to a less aggressive set of numbers, i.e., use the Pfadt specs for street; and 2) switch from a run-flat tire to a non-RFT when your OE tires are shot (or before...if you've got money to burn).

Of course, the alternative would be to move south to NC/GA/TN where the state governments look upon their roads as an asset, vs OH and other northern states that consider their roads a liability.

 

My Z51 handles like it is on rails under any and all road conditions. Best handling car I have ever owned or ridden in.

I would try to hook up with another Z51 owner in your area and drive their car for comparison.

 

In touring the steering is effort is pretty easy and it can get kind of twitchy, kind of gives it a loose feeling. In sport and track it feels tighter since more effort it needed. Maybe your steering effort is unlinked to drive mode and is in the tour setting.

I have a non z51 and after 3k miles its as tight as can be at highway speeds.

 

Op, do you have magnet ride? If so what mode do you run ?

 

No magnetic ride. I have tried the handling in Touring, Sport and Track with the same sensation of the rear end kicking sideways when hitting a bump and darting all over the place.

 

The problem is the short sidewall tires and the heavy runflat tires. Basically, that setup is not going to work without magnetic shocks.

However, I recently watched a 458 accelerate over some city bumps and humps and it did not look good with the magnetic suspension going soft.

Anyway, the fix is wider tires and non-runflat tires:

265/35-18 tire on a 18 x 9.5 52mm wheel
305/30-19 tire on a 19 x 11 74mm wheel

or

265/35-19 tire on a 19 x 9.5 52mm wheel
305/30-20 tire on a 20 x 11 74mm wheel

And that first tire pair is about 1/2" less diameter than stock while the second tire pair is about 1/2" more diameter than stock. Both tire sets have the same sidewall heights at 3.65" front and 3.6" rear. There's a wider selection of tires in the 18/19 set.

Another setup is:

255/40-18 tire
295/35-19 tire

That's a front sidewall height of 4.0" and a rear sidewall height of 4.06".
And the BBS RS-GT wheels are spec widths for them at 18 x 9 and 19 x 10.5.

The Z51 tire sidewall heights are:

3.38" front and 3.37" rear
.

 

Is this your first Corvette or have you owned other Corvettes to know what feels normal and what doesn't?

Do the Z51 C7's come with run flats? This could be part of the issue...

 

Exactly...there is a lot of variance from "Dead on" to out of spec on either side.

Get a good performance shop to align the car...forget the "Free" chevy one. As long as it's in the green they'll let it go...Not necessarily the right way to do it.

 

What does your tire wear look like at this point? Does it appear to be even across the width of both rear tires?

I grew up in the south and bought my first front wheel drive car just before moving to IL thinking it would be a good idea for the snow. It was an 1989 Olds Toronado and mostly sat while I drove my '85 Monte Carlo but when the first snow hit I thought I would see how it did in the snow. At 30MPH I could barely keep it on the road and quickly returned it to the garage and drove my other car into work. When I got home I checked and at just over 1,100 miles both rear Goodyears were worn to the cord on the outer edge of the tread because of misalignment (and the dealer had checked it 800 miles earlier when I complained about poor handling). The good news was the IL dealer took care of the problem (new tires and proper alignment) without hassle.

As others said get the alignment checked at a "real" place and not the dealer.

 

Something is way wrong with your car if it handles like this. This vette has been reviewed by many media organizations who test thousands of cars. No one has mentioned the death trap symptoms you describe and I'm sure these media people didn't fine tune their alignment to some mystical close margin spec to achieve handling that bestowed many "best car' awards.

From the factory, the C7 is heaped praise regarding it's handling. If yours darts around, jumps sideways and is squirrelly, it seems obvious something is way wrong.

 

Definitely not my first Corvette. Have had a C3, C5, and a C6. I definitely know how a Corvette should feel and the rear end should not kick sideways when going over bumps. And it always kicks to the right. Never left. The C7 Z51 has Michelin Pilot Sport Run Flats. I have also driven other C7's without Magnetic Ride and they feel nothing like what I am experiencing with mine.

 

So please tell us when you find the culprit. I would guess it is something in it's undercarriage that is mis-assembled. Given your understandably vague description of the symptoms, you're going to get all kinds of responses as you've already seen. We can't help. Ensure that you get a conscientious mechanic to inspect the fittings on the beast's underbelly. I'm confident they will find something amiss.

 

I have talked to my Corvette alignment specialist and he was not aware of a rear caster specification for the C7. He also took a ride with me and described the sensation as bump steer which is what I have surmised it could possibly be. So where do I find the rear caster alignment specification and also how to set the rear caster. I have run out of ideas. The connections on the suspension have been checked and all seem to be in order. I would like to get him to set the rear caster and see if that solves the problem.