89TripleWhite

so i got eibach pro kit on there, lowered it about 1.1in so it looks pretty decent and doesnt scrape which i like, just wondering if 18x10 in the rear will fill up the fenderwell gap more than say 17x10.5 with 315s? i would like more of the gap filled but if its that much more for tires and what not, or some people have 18s wtih 285...just not sure how it looks? i want it to be flush with the fender you know? so its not like a wide boat with small tires look...which is has because the wheels are stock...any ideas? or side pics of 18s vs 17s? i know 17s look good if you really lower it, but im not going to lower it anymore for now, Virginia has bad roads lol, i cant lower it without it being dangerous...so any ideas? thanks! also im thinking stealth black fr500

Sonic Mustang

When comparing, remember that all tires of a given size are not the same physical dimensions. Some 315s are wider than others and the diameters can vary, too. Search manufacturer websites to find the actual dimensions and don't forget to check F/R diameters. Mine are really close and I've heard of problems with the ABS when the delta gets too big.

Offset is a big factor in how a tire /wheel combination fills out the wheel well. The offset can make a relatively narrow tire/wheel combination look much wider.

This is a 17" X 9 1/2" Team III Halibrand replica with a Toyo 275/40 on it. This Mach 1 has H&R SuperSport springs with Maximum Motorsports height adjustable LCAs.



Same wheel with a different Toyo 275/40 on a Mach 1 with STOCK SUSPENSION.



The above car with H&R SuperSport springs and Maximum Motorsports height adjustable LCAs.



These wheels are a custom offset designed to make the 9 1/2" wheel and 275/40 tire fill the rear wheel well. The white Mach with H&R SuperSport springs and Maximum MotorSports height adjustable LCAs was actually used to test fit different offsets at Team III Wheels before coming up with the right one.

Most tire/wheel threads refer to tires without regard to the actual physical sizes differences across manufacturers and wheels are rarely identified precisely. There are several manufacturers building various replica wheels, so when somebody refers to a FR500 or Mach1 or Saleen replica wheel, it's a good idea to identify the source.

One of the reasons I chose these wheels and tires because they were custom fitted to the identical car with the identical suspension modifications I have. Among other things I wanted no interference/rubbing whatsoever at full suspension travel and steering lock.

If I remember correctly, the stock Mach 1 suspension is 3/4" lower than a stock GT. Did you measure the actual drop of your springs or is the 1.1" drop Eibach's measurement? If Eibach says the springs are a 1.1" drop, is that compared to a stock GT or Mach 1?

If rough roads are a concern, I'd stick with 17"s to put more rubber between the pothole and wheel.

i almost forgot. Both cars are running stock isolators.

89TripleWhite

oh awesome man thanks! yah Eibach states 1.1, but i used to have about a 4 finger wide gap in the front tire between the fender and tire, now its scrapes with a 3 finger gap, like top and bottom finger are squeezing in. so im assuming its about 1.1in or so. i just know that if i get 315/35 its going to be the same diameter as a stock tire i have now as per tirerack.com....i dont want the same height i want it to fill in the gap a little more, but will 18s fill in the gap like THAT much more you know? or is it hardly noticeable?

Sonic Mustang

Unless you're a world champion bartender, finger measurements are worthless. On top of everything else, you're measuring at an angle between the edge of the tire and the edge of the fender lip.

245/45 17 = 25.7" diameter OEM F/R
275/40 17 = 25.7" diameter (Rears on 9 1/2" wheels on white and gray Machs in above photos)
315/35 17 = 25.7" diameter
275/35 18 = 25.7' diameter (TireRack suggested rear staggered application on 10" wide wheel)
285/35 18 = 25.9" diameter (size of rear tire in American Muscle's 18" staggered package)

A 285/35/18 is only .2" taller than your original size F/R tires. divide .2 by 2 = .1 This tire will only fill the gap between the fender and tire by an extra one tenth of an inch. All the tires sizes above have essentially the same diameter (although manufacturer to manufacturer differences may apply).

Eighteen inch wheels / tires will not fill the fender gap any more than seventeen inch combinations. It looks like 285/35/18s on a ten in rear wheel are only two tenths of an inch taller than 315/35/17s on a ten and one half inch wheel. Wider tires, however, will make that vertical gap look smaller.

As I indicated in my first post, wheel OFFSET and width and tire width "fills" the fender wells. Tire width gets rid of the "too narrow" look. I don't think you're going to close that vertical gap without going to a over sized tire that may be too wide. If it does fit, a taller tire will lower your 3.55 stock rear end to:

(OEM Tire Diameter) 25.7" = 3.55

25.9" =3.48

26.25" = 3.44

Don't forget, a taller tire may rub inside the fender well. The stock OEM 245/45 17" diameter tire has a .55" vertical gap between its top and the edge of the front fender lip on my H&R SS equipped Mach 1.

Take a yard stick and measure the height of your fender openings. Park your Mach 1 on level ground and make sure the yard stick is vertical and make sure it is aligned with the dead center of the wheel hub. How many inches from the ground to the edge of the fender lip? Measure all four.

I'll go out and measure my car (Dark Shadow Gray in above photos). I'm quite sure my H&R SuperSports are lower than your Eibachs.

My fender lip heights with 3/8s of a tank of fuel are:

F LEFT 26.25"
F RIGHT 26.25"
R LEFT 26.75"
R LEFT 26.90"

The ground to fender lip measurements confirm perceived "gap" isn't vertical and therefore has more to do with tire width than diameter. My tire are 25.7" diameter front and rear. The vertical gap between the top of the tire and highest point of the fender lip is only .55 inches front (That's with an OEM diameter and OEM offset custom wheel running an OEM size 245/45 17" tire) and averages 1.125" rear.

Just my opinion: Stick with 17"s for rough roads and leave the ride height where it is. I'd swap a little gap for not tearing bits off the undercarriage or bent wheels any day.