RyanPerrella

Hello again,

Need to replace front tires and was going to go with 235 fronts, but am having availability issues and am considering 245's in front now to go with the 255 rears. I know some people will never suggest deviating from stock sizes, but what I would like to know is if they will fit without clearance issues. I wish I could measure the fender to tire gap of the car but I am now in Austin TX, and the car is in CA still waiting to be shipped to me. So I have no refrence now. Also I am not sure if the front cup II's are 8 or 7.5" wide.

I know some have gone to 235, and I would prefer that but I am trying to put feelers out there as to wether or not i am good to go with 245's. I really prefer a wider front tire, I think 225 is pretty small for a sports car weighing over 3500 lbs.

Any other thoughts????? I'm all ears.

PS: I did a search and see allot about rear tires but not much about fronts, I think people sometimes just ignore the fronts.

worf928

A 928 front Cup II wheel will be 7.5". That's a bit narrow for a 245 front tire IMO. I wouldn't do it.

I run 255 on my 9" fronts. And yes, adding some meat to the front is a good thing.

928Myles

Hi,
I am running 235/45/17 on 7.5" 65mm offset cups with no clerance issues. I would think that 245's would not cause any issues. Most tyre shops I have talked to would fit 245's on a 7.5" rim.

Myles

ew928

Searching through the TireRack specs suggest 235/45-17 to be the fattest front fitment for 7.5" width wheel.
At least that's the recommended minimal wheel width.

A Homer Simpson Hmmmmmmm. 255 wide front tires. Better than donuts.

Ernest (NYC) Only 245 on 8" wheel fronts.

IcemanG17

245 is a bit too wide for a 7.5" rim.....using the .86 aspect ratio (rim width to tire width)....the widest you should run is a 225 on a 7.5" rim? Even that is .846....

RyanPerrella

so if going for a 235 (again availability is the issue, i am trying to match the rears that i have which are still good.) what aspect ratio would i go, would it still be 45 or is that now too tall and a 40 aspect ratio is prefered?

Gary Knox

Ryan,

I have 245/40's on 8" wheels - no clearance problems. However, They are a bit small in diamter compared to the 225/45's. The best "upgrade in size" that maintaines equal size tires front and rear is probably 235/45's on the front and 265/40 (both 17) on the rear. These are about 25.5" in diameter, which is 0.25 in radius greater than stock, while they are 0.4" wider both front and rear.

Gary Knox
West Chester, PA

Mark

According to the tire spec charts I've seen - 245/40 requires a minimum of 8".
HOWEVER - you CAN put a 245/45 on a 7.5".

John Veninger

Yes, you can get that tire to onto that rim and inflate it, but why would drive on it? Especially if there is an issue and the investigators find out you had tires mounted on a rim to small based on the tire manufactures specifications.

The main reason for larger tires on the front is to improve handling and braking. Putting on larger than recommended tires on a wheel reduces any value to using a larger tire except bragging rights.

I run 255's on 9" fronts since that wheel and tire size match my need for better handling/braking on the street.

Mark

John - my statement about the fitment was based on the Tire mfg specs!
I did a quick check of BFG, B'stone, Kumho and Michelin....they all show a 7.5" min. rim width for the 245/45-17...

Mark

Some interesting reading from TireRack...

Rim Width Range

Because tires have flexible sidewalls, a single tire size will fit on a variety of rim widths. A tire's rim width range identifies the narrowest to the widest rim widths that the tire is designed to fit. The width of the rim will influence the width of the tire. A tire mounted on a narrow rim would be "narrower" than if the same size tire was mounted on a wide rim. NOTE: Because the overall diameter of a steel belted radial is determined by the steel belts, there is little, if any, change to the overall diameter of the tire due to differences in rim width.

The industry rule of thumb is that for every 1/2" change in rim width, the tire's section width will correspondingly change by approximately 2/10".

For example: a tire in the P205/60R15 size is measured on a 6.0" wide wheel and this size tire has an approved rim width range from 5.5" to 7.5" wide. The tire has a section width of 8.23" (209mm) when mounted on a 6.0" wide wheel. If that tire were mounted on all of the rims within its range, the tire's approximate section width would change as follows:

Difference from
Measuring Rim Rim
Width Approximate Tire
section width
0.5" narrower 5.5" 8.03"
Measuring Rim 6.0" 8.23"
0.5" wider 6.5" 8.43"
1.0" wider 7.0" 8.63"
1.5" wider 7.5" 8.83"

Because of the different wheel widths used in the above example, there is a 8/10" projected difference in tire section width when comparing a tire mounted on the narrowest rim to the widest rim within its range. This may affect fenderwell and frame clearances when selecting optional aftermarket wheel and tire packages

Additionally, some vehicle manufacturers and tire companies have permitted rim widths that are not within the tire's original approved rim width range. For example: BMW has combined 235/40R17 sized tires on 17x7.5" rims (which are 0.5" less than the narrowest 8.0" wide rim listed for the size) on certain M3 models; and Chevrolet has combined P255/50R16 sized tires on optional 16x9.5" rims (which are 0.5" wider than the 9.0" wide rim now listed for the size) on certain Corvette models. While these applications have received the approval of the vehicle and tire manufacturers, staying within the approved rim width range helps assure that the tire's internal stresses are within its design parameters.