Paging Fred...

[ws6drbob]

Hey i was tossing around the idea of getting wheels and Z06 brakes around summertime and was wondering if the rear brakes were worth messing with? Should i just get some powerslot rotors for em? I was thinking about 17"x9.5" in the front and 18"x10.5" in the rear. Or just 17"x9.5" all around. With 18"x9.5" I figure i will have to cut the fender lip and do the BFH mod but what about the axle snubs and what is the best offset?

Thanks in advance

[Injuneer]

BRAKES:

The stock brakes aren't as "bad" as some people seem to feel... Mine pull the car down from near 130mph trap speeds at the end of the 1/4-mile with no problems at all.

The choices you have:

-better rotors and pads, like the Power slots and some Performance friction Z-rated pads. $500.

-upgrade to LS1 front brakes. Maybe $250 for the used parts.

-Z06 or other Corvette brakes... not familiar with the sizes and costs.

-Baer Track Pack. 13" rotors and dual piston PBR calipers (I posted a pic of those in your other thread). $1,000 (I have mine for sale. $600 New, unused - they will not fit in 15" drag wheels. drilled/slotted/zinc washed 13" rotors, hand polished PBR aluminum calipers, braided S/S lines)

-Super exotic setups like 6-piston Wilwoods, Baers, Brembo, etc. $2,000 - $3,500.

Depends on your budget and how you use the car.

WHEELS:

Just because you go to a larger diameter wheel does not mean you will have to cut or hammer anything. A 285/30-19 tire will have approx. the same outside diameter as a 275/35-18, which is the same 275/40-17, which is the same as the stock 245/50-16. Put those on a 9.5" wide wheel with the correct offset (45-56mm) and the tires will not rub on anything, even on a car that has been lowered.

You only get into rolling the fender lip, hammering the inside of the fender liner, recentering the body with an adjustable panhard rod, and/or cutting the corners off the jounce bumper brackets if you go to an 11" wheel, or you get a 9.5", 10", or 10.5" wide wheel with the wrong offset. Even with the 17x11 50mm offset wheels, and 315/35-17 tires (also the correct diameter) only about 50% of the people have problems.

Again, it depends how you plan to use the car. There are people running Auto-X with 17x11 wheels and 315 tires on all 4 corners. For a drag car, you don't want large diameter, heavy wheels, with their thin sidewalls. Depends on what you want.... daily driver that is a nice "show" car, all out canyon carver, all out 1/4-mile car... balance of all of the above.... depends.

[ws6drbob]

Thanks for the info Fred. How do i go about using the offset calc? I put in the specs but wasn't sure what the answer it gave me meant. Do i want the wheel to extend out as far as the stock one does or do I want it out further??? I have no i dea about what strut house clearance means

[Injuneer]

Generally, you want to keep the wheel/tire centered side-to-side in the wheel well. And you don't want the inner edge to go into the suspension components, not the outer edge to get too close to the sharp fender lip, or go outside the fender.

The stock wheel is a 16x8 55mm offset. That results in a 6-5/8" backspace.

You can calculate backspace from offset. Take the wheel width (distance between tire beads), add 1" to allow for the flanges that retain the tire bead on each side. Divide that number in 1/2, than add the offset in inches. Ex....

17x11 wheel, with 50mm offset

11 + 1 = 12

12/2 = 6"

50mm = 1.97"

6" + 1.97" = 7.97" backspace.

That means the front of the wheel projects 12" - 7.97" = 4.03" out from the face of the mounting hub.

One caution... the 1" allowance for the 2 wheel flanges is approximate. Some wheels will have a slightly narrower flange. The actual backspace on an AFS replica ZR1 wheel with the dimensions I used in the example is 7.93".... so, the assumption gets you "close enough for all practical purposes".

To continue with the example, that is the maximum backspace you can put in the rear of a 4th Gen, without having the tire edge in intimate contact with the inner fender liner. Light hammering may be necessary.

And, the 4" "frontspace" is the maximum you can use in the back without the outside edge of the tire starting to poke outside the fender line, when viewed looking straight down from above the fender.

So.... for a 17x11 wheel, 50mm is the recommended offset.

For a 9.5" wide wheel, I have seen offsets ranging from 38mm to 56mm. The 38mm offset puts the wheel/tire too far toward the outside of the fender, in my opinion, but some people like it that way. It will be a problem as far as the front fender lip if your car is lowered. Any more than 56mm, and the inner edge of the wheel is getting very close to the steering knuckle, at least on a 17" diameter wheel. With an 18" wheel, you gain a little more room, since the steering knuckle is sloping back as the wheel diameter increases.

I can show you pics of 17x9.5's with 45mm, 49mm offset and 56mm offsets, if that would help you visualize the different locations. If you limit the offset on a 9.5" wide wheel to 45mm - 56mm, you are only talking about moving the wheel about 1/3", so it isn't any real earth shaking decision.

People have put larger wheels on the car. Some people put huge tires (315/35-17) on the stock 17x9 SS/WS6 wheels. Some people let the wheels stick out of the fender line. Some people use spacers to get a wheel with too much offset moved out from contact with the inner fender liners. I personally don't like any of those solutions, but that's just because I get a little anal about stuff like that.

17x9.5 49mm:



17x9.5 56mm front, 17x11 50mm rear:





17x9.5 45mm front, 17x11 45mm rear (Kelly Drown's WS6):