The wheels I am looking to go with are 18" fronts/19" rears. I also want to close the gap between the tires and the wheel well without lowering. I have used a tire calculator to determine my tire sizes:

Fronts: 255/45-18, sidewall 4.5" diameter 27"
Rears: 285/40-19, sidewall 4.5" diameter 28"

These numbers are the same ratios as stock except sidewall is .25" taller. The tire height is 1.25" taller than stock. I am OK on the widths.

Question:

1. Are the tire diameters OK to fit the wheel wells without hitting?

I appreciate all responses.



[Modified by BHP, 8:23 PM 9/17/2003]

 

They should work....but IMO will look too big for the car. Yes, they will fill the tire-to-fender gap some, but will also raise the car the same amount...in other words you will not achieve a "lowered look" by doing this.

Also, have you looked or chosen a particular tire in these sizes? The only tire I can find made in both these sises is the Yokohama AVS Sport. A very good tire, and I would definitely recommend it, but that 285/40/19 is not a common size.

:cheers:

 

What I've learned so far - increasing the rotating mass on each corner - i.e. increasing weight via tire/rim size increase - is a bad idea. Effectively you will decrease the performance of your suspension and your brakes. The high and low response frequency guardband of your composite monoleaf spring / shock / bushing combination is the focus of serious engineering at Corvette. Same with the brakes, increasing the spinning mass that needs to be stopped without increasing the rotor / pad / piston combination is going to decrease performance...possibly to the point of unit failure. Further, if your Vette has an F45 suspension the shock travel actuators ( mounted on the frame rail directly in front of the upper control arm front and rear ) will come in contact with your rims and/or tires in the front...almost certainly at the worst possible times.

Also, when you lower the Vette the correct way you effectively limit your suspension travel in an amount equal to the loss of wheel travel space in the wheel well. What you're considering would maintain suspension travel while decreasing wheel well space. That would equal wheel to well contact. Might not be what you had in mind.

What I did, to maximize the performance of my suspension / brakes, I went to a combination of rim and tire that is lighter than stock. Consider a quality racing rim that even though it is larger it specs out lighter than stock ( I put Fikse FM/10's and Michelin Pilot Sports on my Vette while still increasing rim size / lowering tire profile in front. 18" all around w/ 265 front and 295 rear).

But I'm always collecting more data, so if you do choose the setup you're considering please let me know what happens.

-Johnny

 

Yes, Yoko's are the only tire in this size and seem to be a good performer.

I have seen quite a few forum members running the 18/19 combo. I have owned two C5's and just don't like the "big gap". It seems like the wheels are actually too small with the stock gap. Lowering seems increase ride stiffness (I have Z51). I chose the tire sizes to cut the the gap 1.25" which is about the same as lowering. The increased ride height is OK since this will help on the ground clearance.

The rotating mass is a good point and it is true that the suspension was tuned with factory size wheels.

If there is a different or better way of "closing the gap" I am open to comments.


[Modified by BHP, 9:40 PM 9/17/2003]

 

Hi BHP,

We're actually doing 255 front / 285 rear for our project car with 18/19 combo, although our goal was to try and get as close to stock diameters & ratio as possible, so this info wouldn't really apply to you, but it might be good for reference.

255/40ZR18 front, P285/35ZR19 rear tires.

Pirelli makes a PZero Rosso Direzionale in the front size and a PZero Rosso in the rear size.

They're ideal, because they have the PZero Rosso
Direzionale on the front, which is the tire made for handling on the wet + the PZero Rosso (asimmetrico) on the rear which is a very excellent dry tire. In combination, you get excellent handling on both wet and dry. These are non-runflat tires.
We've chosen this set with 18 x 9.5 front, 19 x 11 rear in mind, but a 19 x 10.5 is within the spec range for that rear tire as well (see below). You will find additional information on these tires on the following link: http://www.us.pirelli.com/en_US/tyre...=6100003&s4=-1

The reason for choosing the Rosso Direzionale on the front instead of the Rosso is for improved wet handling. It's part of the Pirelli Rosso system

The Pirelli IP Codes are as follows:

255/40ZR18 IP Code: 1119600 Approved Rims 8.5 - 10.0
285/35ZR19 IP Code: 1460100 Approved Rims 9.0 - 11.0

Comparison of tire diameters
----------------------------------
stock front = 25.681" [652.3 mm]
Pirelli front = 26.031" [661.2 mm]

stock rear = 26.661" [677.2 mm]
Pirelli rear = 26.854" [682.1 mm]

Difference in front tire diameter from rear tire diameter
----------------------------------------------------------------
stock = .98"
Pirelli = .823"

There's a .157" difference from stock (rear to front).

:cool:

 

Anyone know if the 27" diameter tires will clear the frame and not hit the wheel well under maximum compression?

Also same question for the rears 28" ?

 

Have you called John at CCW? He is the best! :yesnod: :yesnod: :yesnod: :yesnod: :smash: