rbl

I assume you would need to re-align the car?? If not, what stock wheels will work? Not interested in spending big $$ for CCW, etc. Z51 car so I need the 18” up front.

I have to drive it to the track and need the stock 18/19's for that.

Thanks

AndyF-Dallas

C5 ZO6 rears (18x10.5) will fit all the way around on your C6. 295x30x18 will fit nicely as will 315s however the 315s will rub the inner fender well at full/hard lock both ways even with 1/4 of spacing.

I use the 315s wiht 1/4 spacing (there is baerly enough thread) on the studs but it worked fine for me last year. When the funds allow I will go for a set of wheels with about 55mm offset (the C5Z06 rears have 50 mm) and then use the old wheels for rains.

Good luck. PM or email me if you want to carry this further.

mwvettec5

Can you post pictures of these wheels & tires on a C6 ???

THANKS

rbl

My real questions is about the alignment needing to be changed when they are swapped since I have to drive the car to the track.

Thanks

Poppy's Vette

No, I certainly don't. I had the alignment setup slightly more agressive than street and swap wheels/tires back and forth. -1.75 front and -.85 rear. I would have added more negative camber in the rear but the PS wouldn't go any further. I notice improvement in handling on both the track and the street and I have seen no negative effects (tire wear wise) on my street tires although I haven't put that many miles on the car on the street.

rbl

Thanks for the reply but I'm not sure the question is clear.

The stock setup is 18 front 19 rear. At the track it would be 18 F/R. I am not concerned about the negative camber and I actually run a little more than that.

If I change tires at the track and put the (4) 18"s on the car does the alignment need to be changed? I will obviously have lost the rake due to the diameters.

C66 Racing

You will only lose the rake, and change your alignment settings if the overall diameter of the tire changes. It doesn't matter how much of the diameter is tire and how much is wheel, the center of the axle (wheel) will be at the same height off the ground (meaning your ride height won't change) if the overall tire diameters are the same.

If you get the right aftermarket tire/wheel combination, the alignment should not need to be changed. What you are trying to achieve is an overall tire diameter that is the same as the stock setup. By varying the width and profile of the aftermarket tires, you should be able to get close enough to the stock diameter that you don't need to worry about alignment.

For example, I looked up the stock C6 fronts on tirerack, and a 245/40-18 Goodyear F1 EMT tire has a diameter of 25.7". Comparatively, a Kumho V710 305/30-18 has a diameter of 25.5", almost exactly the same as stock. Taking a look at the rears, the stock rears are 285/35-19 at 26.7". The Kumho V710 315/35-18 has a diameter of 26.4", a little shorter than stock, but only a 1.2% difference, within the 3% that I generally use as a guide. Any tire that you use that won't change your ride height shouldn't effect your alignment.

rbl

Perfect and thanks SubDriver! That answers my question. I was not sure about mixing the tire sizes to maintain the diameters.

So now I just need to find the correct wheels. I think I may be able to use a stock C6 front and I will need something a little wider for the rear.

Poppy's Vette

Well, that's all true if you are concerned about running AH and TC on the track and who does that? j/k because I know a lot of folks here do, for whatever reason. I don't so I don't care about maintaining that ratio at the track. I didn't mean to mis-lead you. So much of this stuff gets over thought and over managed.

C66 Racing

Keep in mind that even with AH/TC turned off the ABS wheel speed sensors are on. Though I can't confirm it, I've read many times that if the overall diameter is within about 3% of stock, ABS will function fine, so I've tried to follow that guidance over the years.

And, if you do change overall diameter a lot, the center of the axle will be half that (higher or lower) difference off. The alignment is fairly sensitive to ride height changes. Lower the front and camber will go more negative which will drive toe to go in (probably the larger effect).

Poppy's Vette

I have not experienced any issues with ABS so either I'm within that mystical 3% or ... it is "myth". I created a spreadsheet, when I was trying to figure out which way I was going to go with track wheels/tires, so maybe I will revisit that and see where my current setup falls. I suppose I could also have my alignment rechecked with the track wheels/tires on to see what the impact is, but again, it may be too esoteric. The car handles excellant on the street and at the track.

AndyF-Dallas

Here you go!

gkmccready

Nice! Do you have any pictures from directly above the fenders? Also, if you measure from the brake rotor face to the wheel spokes, how much clearance is there?

With the 18x10.5 and the 315s do you rub the fenders at all?

AndyF-Dallas

I believe that the offset on the C5Z06 rears (18x10.5) is 65mm. The stock offset on the fronts is 50mm. The wheels clear just fine. There is plenty of clearence. So with 1/4 inch of spacer on the front the tires stick out a tad and with stock front spring (~580? #/in) I was getting a little rub on the outer edge of the front tires when cornering hard. However I put in 860 #/in Vette brakes front spring because even with the Pfadt swaybars the car was still tail happy. What a difference the front spring made. Absolutely no rub on the outside but you do get a little rub on the inner fender well at full lock. The rears fit just fine with no spacers and no problems. I am going to look into a set of lighter custom wheels with the right offset so they don't rub. I don't care if they stick out past the fenders when autocrossing.

See attached.

gkmccready

Yeah, my 18x11 CCWs (w/ 295 rubber) stick out further. :-) I can see how switching to the heavier spring helped, but doesn't that really just mean you're using less suspension travel now?

For example, I barely rubbed the fronts at Thunderhill, but the drop at Spring Mountain showed some serious rub on the LF...

I was curious about the rotor to wheel spoke clearance because I have full width Wilwoods on the car.

davidfarmer

no need for alignment unless your wheels are crooked.

18x9.5 C5 wheels work fine all around, or 18x10.5 C5Z06 wheels as well.

rbl

Dave are the 9.5" wide enough for the rears?