B Stead

The tire rub hysteria has gotten out of hand.

Here is a significant setup with very little risk:

Front, 18 x 9.5 56mm, 265/35-18
Front, 19 x 9.5 56mm, 275/30-19
Rear, 19 x 11 79mm, 305/30-19

Front, 19 x 9.5 56mm, 265/35-19 or 275/35-19
Rear, 20 x 11 79mm, 305/30-20

But front wheels will be found between 50mm and 58mm.

And rear wheels will be found between 74mm and 83mm.

The 305/30-20 rear tire is taller than the 305/30-19. And so the 305/30-19 can go a little more outward than 79mm

There is a reason not to go more inward than 79mm rear offset or more inward than 56mm front offset. Inward wheel offset reduces vehicle track width and vehicle track width works against the center-of-gravity height. (Changes in wheel offset affects vehicle track width and roll center height. Wheel width is just support for the tire and has no effect on suspension geometry.)

In fact several top tires are available in 305/30-19. The R-S3, the AD08 R, the Pilot Sport Cup 2, and the RE-11. (The AD08 R has a very square shoulder, extra wide tread width, and extremely stiff sidewall.)

If the Rival is wanted, it's available in 315/30-18 and 335/30-18.

Here's one setup:

Front, 18 x 10.5 58mm, C5 Z06 rear wheel, 315/30-18 tire size
Rear, 18 x 11 75mm, Oz Alleggerita, 315/30-18 tire size
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\Boost Monkey/

Here are your options per price:

$1-2K not including tires: Low pressure cast wheels, predetermined offsets. Not possible option for you that we know of at this time. Searching the internet might yield some results but you are the most restricted in this category.

$2-3K not including tires: Flow formed/rotary forged/spun forged wheels, customizable offsets to the 'mm' within certain large ranges. Possible for you with a 305 tire, no bigger a tire with Forgestar. HRE flowforms might be available with higher offsets, you need to speak with a rep or vendor for more information if they have an 11-12" wheel with offsets that go to +80's and +90's and can accommodate 305-325 tires on a C7.

$4-15k and beyond, not including tires: Forged wheels, totally customizable and can get you almost anything you want. They are expensive typically. No restrictions whatsoever here so you sometimes you have to pay to play to get exactly what you want.

A bit about each type of wheel in the above price points:

Low pressure cast wheels: weakest and heaviest off all wheels (minus gravity cast wheels but those are more rare these days). These wheels are considered "off the shelf" type multiple application wheels where one wheel/size is made to fit multiple vehicles. These are cheap(est) yet almost all OEM car manufacturer wheels are low pressure cast from the factory. They are strong enough, but when they break, they tend to fracture and break apart. Think of a brittle metal with this type.

Flow formed/spun forged/rotary forged wheels: Less weak and less heavy then cast, but not by much. Don't be fooled by the name, these are cast wheels also. The only difference is that the face is cast and quenched and the barrel is flow formed with the face in a special machine. This process (although still a cast wheel) creates a cast wheel with similar strength properties to forged wheels, but not as strong. These can still be brittle and crack (face for instance), but also the barrel bends when damaged like a forged wheel instead of fracturing like a cast wheel. These are good middle ground wheels.

Forged wheels: These are the lightest and strongest types of wheels. They can be a forged monoblock (forged from a single piece of metal) or forged 2 piece or 3 piece. For 2 piece the face is forged and the barrel is forged, and they are bolted together. For 3 piece the face is bolted to an outer lip and an inner lip (kinda like the barrel is split in 2 pieces). Forged monoblock are the lightest and strongest out of the 3 types. Forged wheels have a grain structure that makes them more malleable and less brittle so they tend to bend when they are damaged versus cracking like a cast wheel. Also, you get more strength per mass so it takes less metal to make a stronger wheel than a cast one. Because of the forging process versus using molds, these wheels are extremely customizable.

Hope this helps. I have done my good forum deed for the day. Please don't PM me or Higgs (no offense), a vendor such as Ben is more than capable (more so then us) to answer all of your exact questions when it comes time to buy and will be a better resource.

thegame

Got it none taken!!! Thank you very much for the info!!!

\Boost Monkey/

I agree partially with this being low risk at 10mm outboard (at stock height), however you are only 4mm away from a known rubbing setup at 14mm. This 4mm could easily be snatched up with a larger sidewall tire plus a lower ride height (how low is questionable). For OP, if he never drops the car, this MIGHT work.

This depends on tire width. a 325 on et.+83 might rub at 19mm outboard from stock at stock height, and definitely when lowered.


Where are you getting this magical 79mm offset number? I assume you are talking about "backspacing" and not inner offset. At what point is center of gravity height negatively affected by vehicle track width? You have this down to the 'mm'? Id love to hear how you got to that...seriously, i'm not being sarcastic.

These sizes you list will put somebody at 33mm (or over an inch) smaller tire diameter at the rear, and 8mm smaller diameter fronts (1/3" approx. inch), throw the speedo by like 3-4mph and will this affect the PTM system? I'm not sure, maybe not... I don't know.

Also, you will be 19mm more outboard then stock, but I agree with you that a MUCH (in this case) smaller diameter tire will allow more clearance and a more aggressive offset/tire fitment, but that can be easily nullified with an aggressive drop and damn at what cost...over an inch diameter smaller rear tire?? I def wouldn't do that to clear a larger width tire and more aggressive offset wheel.

B Stead

The OP began by wanting the same tire sizes as a GS.

That's an advanced setup but a 325/30-19 tire can be done at 79mm wheel offset. That's because lowering the car tucks the tops of the tires. Show-cars do this and race-cars do this.

So:

Front, 295/30-19 Pilot Sport Cup 2, 19 x 10.5 56mm wheel
Rear, 325/30-19, Pilot Sport Cup 2, 19 x 12 79mm wheel

Then the car is lowered 1" to tuck the tops of the tires. But also the lowered car needs stiffer springs. So this is likely the Bilstein or Penske coilovers that are needed. The spring rates should be either Z06 rates or T1 rates.

Strangely enough this is an easier rear setup than the 335/30-18 because an 18 x 12 79mm wheel might hit the control arms.

The 79mm rear wheel offset maintains vehicle track width and roll center heights
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Ben@WeaponX

These are actually one of my new wheels debuting next week. They're a forged duoblock and I can do 19/20s or 20/21s

Here's a sneak peak of a 20/21" setup with Pirelli 265/325s on Jody's sweet C7. They look amazing... can't wait for him to get it all cleaned up and ready for a shoot.

\Boost Monkey/

Again...

Why do you insist on recommending sizes that will rub for sure? First of all, if OP was going to go with a 325 tire, he should go with a 325/25 not a 325/30 as you suggested. A 25 will put him only 10mm diameter difference whereas a 30 will over double that and put him 24mm (or about an inch) larger diameter tire. The 25 puts him closer to proper stock diameter. Also, a larger diameter tire as you suggested will worsen the rubbing now that the suspension has less travel range before the sidewall contacts the fender lip. You are contradicting yourself now and what you said earlier about decreasing diameter to aid in clearance (which can be correct).

Also, racecars don't "tuck" the tires, the cars are very low to lower the center of gravity and since springrates are stiffened and dampening hardened on racecars the inherent increase in suspension stiffness allows them a lower wheelwell arch/less gap. But don't be mistaken, there is still plenty of travel room before the tire reaches the fender lip/arch. But in no way close would I consider them to have "tucked" tires in the same way the stance crowd (as you stated show cars...) considers a "tucked" tire.

Here is a picture of the Nismo GTR GT500 SuperGT racecar. Does this appear to be tucking to you?





The OP clearly stated he doesn't want to lower the car. Lowering the car will only make the rubbing worse and lowering the car only 1" from stock height will not tuck the tire, just reduce the wheelwell gap. To tuck the tire in the proper sense, he would have to go much lower than 1". Now on to stiffer springs. Yes the proper rule is to increase springrate stiffness and increase dampening when lowering the car but the OP is not corner balancing his car for the track every weekend (I assume). You are getting way technical for simply wanting to clear a proper wheel/tire setup, and only dropping the car 1" at that (even if he wanted to). If lowering the 1" (or like 3/4" stock bolts iirc) put the car in any danger of riding the bump stops, I would assume the Corvette team wouldn't have allowed adjustable ride height on the stock suspension. Your suggestions are a waste of money as the OP in concerned and you would be throwing money at trying to make an aggressive setup clear properly, and for all the wrong reasons.

Ok now I understand what you are trying to say. Increasing backspacing and thereby decreasing the stock track width with offsets higher than stock versus increasing track width to aid cornering (the typical route for wheel upgrades on other platforms that can afford lower offsets). But you are seriously splitting hairs here dude.

So, can you tell me exactly how much the OP would be increasing LLTD by decreasing track width say 18mm center to center? That would show us how with a 9mm positive offset increase per corner and moving the track width less 18mm would decrease outside grip. Ill bet you my house that the approximate less than .7" decrease would be insignificant compared to the traction he would gain by being able to run a 325 tire versus a 305. 20mm more contact surface per corner versus losing 18mm track width. You see where I am going here? If anything, if we are splitting hairs, I would be more worried about keeping the front to rear track width ratio correct than minimally decreasing track width in the rear.

This is the same weak argument as those not wanting to increase negative offset because of increasing load on the bearings. The sky is falling if we push the wheel out!! Everything in moderation, my friend.

Mr Guns

I really like the Rays Forged wheels. They seem to have good fitment in the pics, but on their site, they list the specs as follows:

Front Spec: 19×9.5 +55mm
Rear Spec: 20×11.0 +69mm

If the rears were truly 11" with a +69 offset, wouldn't they stick out?

\Boost Monkey/

I am a HUGE fan of Rays/Volk/Gram Lights etc as I come from an import/euro background. They are one of my favorite wheel brands. Very well made, state of the art facilities and equipment (a wheel industry leader with the likes of HRE and such IMHO) and even supply some of the OEM wheels for Nissan (GTR, 370Z) and other Japanese manufacturers.

Anyway yes I can see for sure in the second pic that these (rear) do appear aggressive in offset and sit about where I would expect to see them sit. The first pic is kind of misleading and not a good angle.

To answer a possible concern of how they are fitting:

It appears to me they are using OEM tire sizes (285/30/20) which is creating a stretched tire on an 11" wide wheel. On top of that, Toyo's are one of the brands that run a pretty narrow sidewall like Falken's (Check that other thread "Max tire width" or whatever where Theta confirmed his 888's ran narrow) and Toyo has always been a preferred brand by the "stance" crowd because they stretch well and narrow. Because the tire is stretched and not bulged out from the wheel, that allows more clearance for an aggressive offset.

He is dropped as well. But it doesn't surprise me that a narrow brand tire that is stretched one size will allow him to clear on this setup. On top of that, with the setup he is running:

20x11 et.+69 285/30/20 equals +10mm outboard from stock.

10mm outboard from stock has shown to be a low risk setup as we discussed earlier. Couple that with a narrow brand and stretched tire as mentioned above, and this guy is good to go.

I like those wheel a lot also. I just hate waiting for slow boats and L.A. port customs. I once waited 6 months for a set of Volk GTS's.

Mr Guns

Good assessment. Thanks. Looking at them more closely, I could see how a fatter tire would stick out a lot more. I wonder if the camber was adjusted as well to make them more flush?

I also heard about long wait times. I don't think I could wait that long on a set of wheels. I'm too impatient.

\Boost Monkey/

Who (vendor) you get them from is very important, trust me.

No way to tell on camber from these pics, but honestly it doesn't look noticeably cambered over what stock looks like. If I had to guess, I would say he is well within stock (non track settings) range.

B Stead

One of the vendors here runs a 305/30-19 rear tire on a 19 x 10.5 65mm wheel.

You say that a 285 tire will not work on a 10.5" wide wheel at 65mm offset.

Now how is the 305/30-19 rear tire run on a 19 x 10.5 66mm wheel ?
They lower the car 1" or more with their coilover system and that tucks the tops of the tires. Then they control bump suspension travel with stiffer springs.

There's just a poster jumping around here that doesn't understand how aggressive fitments or motorsports fitments are done.

To get the 325/30-19 rear tire on a 19 x 12 79mm wheel does require lowering the car to tuck the tops of the tires and also requires stiffer springs. And actually the setup could be done easier at 85mm offset just like I showed in my chart. Furthermore, there are some recently posted 325/30-19 rear tire setups here.

But I don't insist on the 325/30-19 rear tire. I more often recommend the 305/30-19 rear tire on a 19 x 11 75mm to 79mm wheel and that to the average car.

The OP asked about the 325/30-19 rear tire because that's the GS size
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B Stead

It doesn't matter if the wheel sticks out only if the top of the tire sticks out.

To make that fitment, lower the car 1" or more to tuck the tops of the tires and then add stiffer springs to control bump suspension travel. (That's Bilstein or Penske coilovers with Z06 spring rates or T1 spring rates.)

Well, does the car in the photo look like its been lowered ?

One problem is that the 305/30-20 rear tire is 1/2" more radius than the 305/30-19 tire. For a fitment a little easier to live-with find something for the 305/30-19 rear tire. That's a rear wheel at 19 x 11 75mm to 79mm. And no suspension changes needed.
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\Boost Monkey/

Which vendor? Can you show me pictures of the setup? That's put his wheel about 23mm outboard from stock. AGAIN...countless guys have stated a 14mm outboard setup rubs...even some at stock height. This is documented proof. I don't understand how you are arguing documented proof of what setups have rubbed?

Yes, and it appears that you are that poster.

You are spitting out random suspension facts here and there that don't pertain to the subject of why this thread started. Its like arguing with someone with suspension fact tourettes syndrome.

For someone that appears to have the answers, you have answered none of my previous questions nor attempted to negate anything I have said. You just keep spitting out random repetitive suspension related crap and ill fitting setups for a guy who wants zero possibility of rubbing.

Again, you recommend a +20mm to +24mm setup when a simple +14mm has shown to rub on many guys setups, even at stock height.

From the other thread right next to this one, without even having to search and find a thread that proves:

I'm done man, that's the last time i'm going to say that.

B Stead

Here's the setups I most often recommend:

Front, 18 x 9.5 56mm, 265/35-18
Front, 19 x 9.5 56mm, 275/30-19
Rear, 19 x 11 79mm, 305/30-19

Front, 19 x 9.5 56mm, 265/35-19 or 275/35-19
Rear, 20 x 11 79mm, 305/30-20

But front wheels will be found between 50mm and 58mm.

And rear wheels will be found between 74mm and 83mm.


Now just post the setup that you are recommending. Don't debate everything and everyone on the planet but just post your setup
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\Boost Monkey/

YES...The top of the tire tucking inward is negative camber...When you lower a car, you increase negative camber so you must get an alignment to dial back in the proper camber specs. When you dial back in the proper camber specs (assuming you don't need a camber kit to do so), that moves the top of the tire back outward towards to fender line (like it was previous to the drop)so you can stay within factory range and not increase inner tire wear.


I agree with the last part partly, the sizes you list are right on the borderline of what has shown to rub for some guys though, 75mm would rub for some guys. It already has, no need to prove it.

First you were dead set on this setup with a 75mm (+14mm outboard) now you are saying "awww well 75-79mm would work".

Higgs Boson

There is a reason I am on a +83 11 inch rear rim......NOT a 75-79mm.

BTDT.

B Stead

You said your suspension was the base suspension lowered 1" with aftermarket bolts ? That's not really a good setup. It's softer than the Z51 and then lowering with lowering bolts gives up too much spring pre-load in addition
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Higgs Boson

no its not lowered with aftermarket bolts. my suspension is base springs but with Z51 shocks and sway bars. it's a horrible setup that MANY people are running that did not want a dry sump oil system.

and even that is beside the point. just as they have from the beginning, your posts indicate you have read a lot about wheel fitment theory but have no real world experience, and certainly none with the Corvette. "lower the car to tuck the tires" guess what, doesn't work! mine has been every height from lifted to slammed. if the wheel doesn't fit, it doesn't fit.

additionally, if you think that people should CHANGE THEIR ENTIRE SUSPENSION to run your recommended offsets you are crazy! a properly fitted wheel does not need to have extensive modifications to work. not every one wants to be on the brink of disaster for the sake of a few mms.

B Stead

Front, 265/35-18, 18 x 9.5, 56mm to 52mm
Front, 275/30-19, 19 x 9.5, 56mm to 52mm
Rear, 305/30-19, 19 x 11, 79mm to 75mm

That setup doesn't require any suspension changes.


Now take a look at the Volk wheel setup in the posts above. That car is lowered to tuck the tops of the tires. It's a very well known technique. (But don't lower with the lowering bolts because that gives up spring pre-load. Coilovers with stiffer springs are needed for a setup like that.)
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