EngineeredBLUR

I believe from looking at past emails, 265/35/18 front with a 9.5" wheel and 295/30-19 rear with a 11" wide wheel around a 55 offset.

Torque Obsessed

I've been looking at the F14's for my EB too. Supervettes offers them in a variety of sizes and offsets. The offsets are posted on their site. If you don't like silver, just navigate higher and look at the rest of the Forgestar offerings.

http://www.supervettes.com/forgestar-f14-silver.html

Torque Obsessed

I've spent a long time trying to figure out offsets and whatnot because I have a set of C6 Z brakes sitting in my garage waiting to put on the car. I want a 19/20 combo but I don't want to rub the brake ducts, and I don't want excessive poke. I wound up creating an Excel file to calculate the change in how far various wheels would poke, and how far inward they'd extend, compared to my stock '02 Z wheels.



In simple terms, there are two columns showing the change in mm of the position of the back (inside edge) and front (outside edge) of the wheel. Positive numbers are to the outside; negative to the inside. I highlighted the ones that seemed close, so I could tell what might work.

The math is pretty simple. If you have a 9.5 inch wide wheel, that's 241.3mm. The centerline is half that distance from either face, or 120.65mm. Add the offset to that distance to find out how far the inner edge is from the mounting face: 120.65 + 54 = 174.65mm. To find out how far the outer edge is from the mounting surface, subtract the offset instead: 120.65 - 54 = 66.65mm. (Those are the numbers for the OEM fronts.)

Anything with an outer edge distance > 66.65mm is going to stick out farther than the OEM front wheels, since the mounting face is fixed relative to the rest of the car. Anything with an inner edge distance > 174.65mm is going to stick inward more than OEM. I don't know how much space there is from that inner edge to the brake ducts.

None of this tells us whether wheels will clear the C6 Z big brakes; that depends on the wheel design. But it helps us know if they'll poke and how much closer we're getting to the ducts. BTW, those aren't real C6 wheels mentioned in the list; they're reproductions from vendors. I just threw them in to compare.

ZeeOSix

^^^ Torque Obsessed ... excellent spreadsheet. I do the same kind of analysis with Excel. I just did a spreadsheet to compare tire sizes for +1, +2 and 18 or 19 all-round to find tires that are closest to the OEM C5Z06 tires in terms of diameter, width and revs/mile.

AngryTurtle

This ever get verified?

04MSZ06

I'm looking in to it. Need a bit more cash to make the commitment.

BryanPendleton

Let’s clear up some confusion. C5 fitment and availability is not about what is stocked by vendors or having Forgestar give you the “right fitment”. Vendor stock is going to be extremely limited anywhere you go and likely will only accommodate more popular applications or more universal wheel fitments, which a C5 is far from. Forgestar does not cast wheels specifically for the C5. They cast universal wheels that can be machined to accommodate many different applications. Available fitments all comes down to the castings for the wheels and what offsets the castings will accommodate. With the Forgestar F14, the wheel face and spoke geometry is fixed based on your selection of Rim Diameter and Face (ie. "Semi-Concave" or "Deep Concave"). This face geometry is dictated by the casting. You pick a 19” Deep Concave and regardless of rim width, they all have the same face. With either face selection, the face will only support a minimum distance from the outer lip to the mounting surface. Forgestar manufacturers the F14 with the least amount of offset, and the mounting surface can then be machined (moving the surface closer to the outside of the face) to meet the desired offset, WITHIN the limits the design will accommodate.

Regarding C5 fitment, unfortunately the F14 is very limited. The 18x11 and 19x11 wheels (Deep Concave) are limited to a maximum offset of +55mm. I went back and forth with Forgestar on pushing that offset to even +56mm or +57mm, and they said the design will not support it without compromising the integrity of the wheel. I even argued with them that some of the other barrel widths had 1mm less front protrusion than the 19x11, which in my mind told me the 19x11 could be pushed another mm, but they said no. Could you have a machine shop do it for you? Yes, but I wouldn't go that far.

So what does this mean for C5 fitment? The closest-to-OE rear fitment you can get from the Forgestar F14 is the 18x11+55 or 19x11+55. You can go with a narrower rim width, but it does not change the distance from the mounting surface the outer lip any more than 1mm or 2mm, meaning the 18x10+44 or 19x10+44 will still look like the same fitment relative to the fender. Almost all C5 owners opt for the 18x11 or 19x11 rears. Some vendors spec out of +53mm offset (why I don’t know, just means more possible protrusion beyond the fender), most go with the maximum, +55mm, which effectively protrudes 1/3” (or ~9mm) more than a C5Z rear wheels. Now if you go with 20” rear wheels, you can get fitments that are within 2-3mm of a C5Z rear wheel, so you should have no issues of the wheel protruding beyond the fender.

So the next question may be why do some owners F14 install look flush and some protrude? Tolerances, alignment and ride height are the major contributors, though some have the more aggressive +53mm offset also. Tolerances: No two cars are identical. Fender position relative to the suspension will vary a few mm between cars. Alignment: GM appears to have delivered the C5 with 0deg camber. If you add any camber, you are pushing the lower control are outwards, and the wheel/hub pivots off the upper control arm attachment point, effectively moving the top of the tire/wheel more under the fender. Ride Height: Based on the double wishbone suspension of the C5, the more you lower the car, the more the wheels are moved inward or tucked under the fenders. So the C5’s that are slammed are going to look more flush with the Forgestar F14 than someone running OE ride height and/or camber. The one thing that can be safely said is that I have not heard of anyone having tire/fender interference when running a properly sized 295 or 305 rear tire. There may be some protrusion beyond the fender, but upon compression of the suspension the suspension geometry will still tuck the tire in to clear the fender.

Now if you are running wide-body fenders or fender flares you are own your own. 

Z06Brucey

I'm planning on running the F14s as well with a Nitto 305/30/18 DR. Do your 305's stick out a lot? My car is pretty damn low right now.

xdmikey

Good for you! I wish I had shined them on. As previously mentioned, my matte black arrived almost gray, kind of burnt charcoal. Now I wish I'd gone with the OZ ultralegerra(sp?)in gloss black to match the deep blue body on my e46 cabrio. Oh well, my gloss black wheels match thebody on my black c5!

xdmikey

Z06Brucey, you got the same color I have on my e46. After I cracked a rim I thought well now I can justify getting those OZs in gloss back but Celaya was able to weld it back to good. Dammitt.

nullpointer

Any issues with AH/TC with the following

FORGESTAR - F14 - GUN-METAL - 18X9.5+50

FORGESTAR - F14 - GUN-METAL - 18X11+53

Also do you think c6 z brakes will fit in with this combo? I really don't want to step it up to 19" wheels.

Hoping they don't stick out as well...

rjwz28

Wheel sizes don't cause AH/TC, tire sizes do

Pick staggered tires (such as a 255/35ZR18 front with a 285/35ZR18 rear) and you will have zero issues

See the photos of the Z06 with those exact front wheels and C6Z brakes IN THE FIRST POST

nullpointer

Gah I don't know how I miss it on the first page, thanks

rjwz28

No problem

Also, just FYI: I posted those sizes because they're the best fitment you can get for a Corvette on 18-inch wheels in the Michelin Pilot Super Sport lineup, which will be my next tire

You could just as easily run a 265|295/35R18 or 275|305/35R18 stagger, depending on which tires you want to use

tungstenfoot

Are the gunmetals on the EB on page 1? The 1st post are black...

shawng89

I just got a set of the f14's in black semi gloss with 18x9.5 +50 & 18x11 +53 offsets.Tire choice was Nitto NT05's - 265/35 front and 295/35 rear, looking back i should have gone with a 275 in the front to fill up the wheel well a little better but in the meantime i will just lower it a little more.

03 Z-oh-6

Looks like the rear wheels poke out beyond the fenderwell?

BryanPendleton

That's probably because they do. Without significantly lowering and/or adding camber the f14s are going to poke a tad.

03 Z-oh-6

Thanks. I just ordered 19 x 9/19x11(305/30's) F14's for my '03 z06. My car is lowered a good amount. I hope they don't poke out at all.

envyz06

anyone have the F14F yet?