balpo

Which is the better choice as an autocross car that also has to do daily driver service?

Anyone back to back run each of them - if so please speak up

QKSLVRZ

I didn't autoX either (though I did my C5Z06).

I figure the Z51 will have a little less traction, and little more HP, and cost a little less to buy shoes.
Otherwise I think most the rest is a wash one way or another.

I needed to lose the 6 speed, but don't really see it as a drawback, other than for track days, I'd need more cooling.

conemark

It may very well be a toss up between the C7 Z51 & C6 GS as far as autocross goes. They're both eligible to run in either SSR or A-Street. Let's look at some pro's and con's:

C7 Z51 Pro:
Narrower car overall.
More developed chassis and brake package from the factory.
Weight is about the same as a C6 GS.
Power is slightly higher.

C7 Z51 con:
One inch longer wheelbase.
Narrower wheels: If you wanted to run SSR, no Hoosiers available in 19 & 20 inch sizes (I know at least around here, we wouldn't complain much at all if you went to 18 & 19 inch wheels and wanted to run A7's).
Targa top.

C6 GS Pro's:
Shorter wheelbase.
Wider front and rear wheels.
Greater knowledge base of development from other competitors.

C6 GS Con's:
Some argue the front spring rate is a bit soft (C6 GS & C7 Z51 spring rates look to be within the same ballpark, so it's somewhat of a draw here).
Targa top (I'm not a fan of the subsequent squeaks).

As far as a daily driver goes, I know I would prefer to live with the C7 interior.

strano@stranoparts.com

Were you specifically asking about the C7 Z51 vs. a C6 GS, or a C7 GS? I think I didn't see that and wasn't sure.

Frankly the C7 has not been all that embraced for autocross (seriously anyway). In fact I've driven not one. A C7Z at an Evo School I was teaching. The 20" wheels are a bit problematic as there is no good 20" tire, and 19's cost money and leave you with only the RE71R as a good option and the 305 only came out in September.

I dunno, the C7 turned out to be heavier than it was claimed. It's on skinnier wheels front and back too, so that's less than idea. LT1 has more power, sure.... how much of that is useful? Hint, not much. I've own(ed) C6's in both Z06 and GS guises. And I've driven the LT1 extensively in a 2016 Camaro SS auto a friend has.

QKSLVRZ

I was impressed with the performance of that car, even the handling with the skinny front tires, it has good street handling (ie mountain roads about as fast as is prudent).

I miss both my C5Z06, and my GS, not sure I'd go back the C7 is a better "car", but I think the C5Z makes a great track pet.

Hey, my C5 car cover fits the C7 just fine.......

balpo

Sam, Thanks so much for your wisdom. I have been a beneficiary of Evo school (won state in my class the year I went to Evo - haven't done nearly as well years I did not go to Evo). Sorry I was not specific. Question is C7 Z51 va C7 GS? There appear some theoretical arguments, but as I must have a daily driver I would like more than theory as it is a costly decision to make the wrong choice.

Thanks,

balpo

Conemark,
Thanks! I was not specific - need to know C7 Z51 vs C7GS.
Look forward to your thoughts.

NTMD8R

I have a '14 Z51 7 speed. We have autocrossed it for the last 2 years.
I have not driven (or even seen) a C7 GS.
But let me tell you about the "issues" I have had with my C7.

First, I lowered it a bit on stock bolts.
Then I put Toyo R888 tires on it.
Then I put LG sway bars on it (front and rear).
It did averagely well.

I moved up to wider wheels, and wider Toyo R888 tires. Should be better, right ?
I had to raise it back up to stock height, and had to put a TON of camber in
to stop the tires from rubbing. But Tons of camber is not an issue for me.
This fundamentally made things worse.
The back end kept "coming out" under acceleration coming out of corners.

I have had serious Autocrossers drive the car and they say the same thing.
Glenn Hernandez said "the rear keeps getting loose".
Another local guy said "this car is EVIL !"

The Z51 has magride (electronically controlled shocks) and an E-Diff.
We just CANNOT alter any parameters for these components.
I spent TONS of money on alignment settings, and those wheels and tires.
I took off the LG sway bars... slight improvement.

Finally, in desperation, I bought smaller (non Z51) wheels (18" and 19"),
and then put Bridgestone Potenza RE71-R tires on it.
Now the car is fairly competitive in AS.
But, the rear end still wants to come out, so judicious application
of the "go" pedal is paramount.

I have since now purchased an '08 Z06, and we are going to campaign that car.
We are used to being in the top 10 or better during our past at an event,
and being in the middle of the pack (in AS) just doesn't feel good.
So now to the C6 Z06 with A7 tires.

I've seen a C7 Z06/Z07 compete against us.
Wow... almost domination. Now, they do have the Pilot Sport Cup 2 tires,
and they ARE built for racing.

I understand that a GS has the same suspension components as a Z06 (not Z07),
and has the wide body, but has the LT1 motor.
Now, is the Z06 (plain jane) suspension similar to the Z51 ?
If so, then I suspect it (Z06) and the GS will be plagued with the same
problems I had with the Z51.

Get rid of the electronic shocks and E-Diff, and I suspect these cars could be tuned
suspension-wise to be awesome performers.

Or get a base C7 that doesn't have magride or E-diff, and it might do well also.

My opinion.... others' may vary.

(you can read all about my "issues" in the C7 Z06 forum)

balpo

Wow! Thanks for your experience. This is generating pause for thought. Rear end less loose with narrower wheel rims - interesting observation - what do you think is going on there?

QKSLVRZ

Did you ever try the alignment that was suggested at the same specific settings he gave?
I'm curious if it helped your problems or not.

greendot

I have a '16 Z51 non mag ride. I run NCCC so I can not only run the 1" diff diameter wheels but +1" width. I usually run A7s but have run RE71Rs and do not have an issue with the rear stepping out that you report on either of these tires.
My car is lowered on stock bolts and aggressively aligned for a/x, but I drove it from Michigan to Florida on the 'stones with no problem (other than the snow on the return trip ) And fwiw for you who don't know me, I'm regularly on or very near the top of the pile so I do drive very aggressively.
My major issue with the car is that I have to unlearn left foot braking as it is too easy to deplete the vacuum and lose boost assist. A8 trans.
As to the original question, I'd expect the GS to be better given the wheel and brake upgrades. Have not seen one in competition yet.
The Z51 has stiffer springs than the base car or than the mag ride car.

NTMD8R

QKSLVRZ,
yes I played with alignment for most of 2 years.
I did get the rear Caster done too (twice).
Essentially with the smaller wheels (18 and 19) and RE-71R tires,
it does now handle quite well.
But I want to do better, and that is why I have moved to the C6 Z06.

greendot,
with non-magride, that might be a major difference in the handling,
which might have some affect on the rear end stepping out.

greendot

I have not considered rear caster, but maybe I should not mess with success

Searious

I've got a 14 z51 with magride, and the feedback from our local nationally competitive drivers has actually been quite positive regarding handling, but he has complaints about the throttle response. The back end can step out some but it also settles in very well for us. Rear caster for me hasn't been touched, but the other regular C7 had to get his done. I am always surprised at the amount of roll it has for a corvette however.

QCK, how wide did you go on your wheels with 18/19? My 255/285 setup is going to make it a month or two more and I'm trying to see if I can get anything more onto the wheels of if that's it for AS.

formula80_ca

I have a 2015 Z51 and squeezed a 275 RE71r on the front 18x8.5 base wheels (minor rubbing on the plastic brake deflectors under load and major steering inputs), had to run the 285 on the 19x10 base rears because they hadn't produced the 305 yet... I will try the 305s on the rear this year. The car is still probably under tired for weight and power but on a more open course it can perform quite well. I managed to put down one FTD Pax this year and had a couple of Street class wins. This year it rained at 3 races in one series and 2 races in the other series I do, so a Golf R beat me in the Street class championship in the first series and that same Golf R and an FRS finished ahead me in the second series that run alot of "Miata" courses throughout the year, not bad for a 3500 lbs car without enough tire and a second year AutoX driver that is still learning this discipline. I definitely learned this is a terrible rain car, but I love it in the dry on "Corvette" courses. The Z51 moves down to AS from SS pax which will help a bit this year too, while the bigger tired C7 Grand Sport will remain in SS class.

Ennea13

What kind of wheels did you use when going to the 18/19 inch tires on your Z51? Also did you lose the ABS or any other systems when going smaller on the wheel size?

formula80_ca

I bought a set of the 2016 factory base corvette wheels in black, that had been taken off after just a couple hundred miles when the original owner ungraded to some aftermarket wheels. They have worked well, they clear the brakes on the Z51, but only just... you have to balance the wheels by having the weights placed a couple of inches inboard of both the inner and outer edges of the wheel otherwise the calipers will knock them off out the outside and the brake ducts will knock them off on the inside. Under extreme lock the plastic brake ducts will rub slightly so I did a small amount of trimming. As far as abs goes, I have had no problem. Some have said that if you change the ratio of the tire diameter from fronts to backs too far from stock the computer will have a problem, but I haven't had an issue.


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cleanerPA

I don't autocross, but just wanted to point out that the C7 Z06 also has magnetorheological shocks and the E-diff.

Holster Maker

Enneal 13, I also when with black 18/19's C7 Z06 Replicas for AS class. Better tire choice, better ride, less tire dollars, within 1-2 lbs each corner, no ABS problems, being same diameter, bought new TPMS, and like F 80 said, place balance weights in-board to avoid brake pad balancers or get new pads without ***** sticking out. Besides, I hate 20" tires.