Wheel Sizing & Watch Outs for a 1st timer

heretolearn · 01:22 PM

Currently building out my first Porsche 911 ever. Very new to this journey and wanting to soak in as much knowledge as possible and there are a ton of gaps to fill.

I've dug around this forum and have read a lot of posts but figured it would be the most helpful for me to ask my questions directly to you all.

I am building out a 1971 911 with my own touches to it. My rear flares are 1-1.5inches wider than SC flares and I'm worried the Fuchs I have, 15x7s, may be a bit too small. Wanted to pick the brains of the experts here and ask about the following:

1. Are 15x7 all around going to be okay with the flares that I have?
2. Should I explore going slightly bigger in the rear, say 8s or 9s?
3. If I do explore going bigger in the rear, how will that affect the handling of the car? What are some other things I need to put into consideration?
4. What kind of effect do spacers have?
5. If I explore a wider rear tire size, would that be an alternative route?
6. What am I not thinking about that I should consider?

Thank you all for your input!

PTRL HD · PTRL HD's Garage

Quote:

Originally Posted by heretolearn

...My rear flares are 1-1.5inches wider than SC flares and I'm worried the Fuchs I have, 15x7s, may be a bit too small. Wanted to pick the brains of the experts here and ask about the following:

1. Are 15x7 all around going to be okay with the flares that I have?
2. Should I explore going slightly bigger in the rear, say 8s or 9s?
3. If I do explore going bigger in the rear, how will that affect the handling of the car? What are some other things I need to put into consideration?
4. What kind of effect do spacers have?
5. If I explore a wider rear tire size, would that be an alternative route?
6. What am I not thinking about that I should consider?

Thank you all for your input!

You don't say what you've done with your front flares, so I'm going to assume SC profile.

1. you can make a square setup work, but factory SC/Carrera typically had 1" wider rears. Turbos were 2" wider. You'll need a lot of rear spacer to make a 7" wheel work with that wide of flare
2. I would go wider in back. How much depends on your front flare setup, but you're probably going to want a turbo like setup with 7" front, 9" rears
3. better grip? It was how the factory did it on later cars so I don't see there being too many negatives
4. there are regular debates on spacers on many online forums. I use spacers to get the wheel/fender gap where I like it and have had no issues with it, but I don't track my car.
5. are you asking if you should keep the 7" wheels all around and just put wider tires in back? I don't think you'll safely fill the gap to the flare with just a tire change.
6. suspension travel - your flares look great but appear fairly flat compared to the bulge at the top of a factory turbo flare. The suspension in my car is old and soft and if I hit a bump during aggressive cornering the rear tire will travel enough to rub at the top of the turbo-ish size flare. You may want to upgrade your suspension to minimize this travel

Continue to do your research. There is a lot of good information on this forum!

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by heretolearn

Currently building out my first Porsche 911 ever. Very new to this journey and wanting to soak in as much knowledge as possible and there are a ton of gaps to fill.

I've dug around this forum and have read a lot of posts but figured it would be the most helpful for me to ask my questions directly to you all.

I am building out a 1971 911 with my own touches to it. My rear flares are 1-1.5inches wider than SC flares and I'm worried the Fuchs I have, 15x7s, may be a bit too small. Wanted to pick the brains of the experts here and ask about the following:

1. Are 15x7 all around going to be okay with the flares that I have?
2. Should I explore going slightly bigger in the rear, say 8s or 9s?
3. If I do explore going bigger in the rear, how will that affect the handling of the car? What are some other things I need to put into consideration?
4. What kind of effect do spacers have?
5. If I explore a wider rear tire size, would that be an alternative route?
6. What am I not thinking about that I should consider?

Thank you all for your input!

As noted what did you do in front?

You want a balanced wheel and tire setup, generally the rear wheels & tires will want to be 1 -2" greater than the fronts w/ roughly equal tire ODs, specifics of the drivetrain and use would nail that down better.

if staying w/ Fuchs you will need very large spacers
For fuchs no mater whether 15 or 16 you are very limited
all 7s are ET23.3 with a wheel front space of 2.93", the tire will usually add a bit to that f/s

all 911 8s are ET10.6, w/ a wheel f/s of 3.93"

all 944 8s are ET23.3 w/ a wheel f/s of 3.43"

all current 9s are ET15 w/ a wheel f/s of 4.22"

a stock SC/Carrera can fit up to a 9.5 ET19 w/ a wheel front space of 4.35", but w/ a 275/40 x 17 tire runs into issues mostly on the backspace but also a a bit on the front, a 255/40 x17 doesn't have this issue

so if you have fender lips sat 1" greater than an SC/Carrera you want 1" spacer w/ a 9.5ET19 or around a 1.42" spacer w/ a 7 ET23.3

there were some early 9ET3 and 11 ET -27 x15 wheels that are scarce and extremely expensive

for these
9 ET3 has a wheel f/s of 4.73"
11 ET -27 has a wheel f/s of 6.91"

tire availability also enters this ,

if it were my car w/ a pretty decent motor and reasonable gearing I'd want maybe 9 & 10 either 15 or 17 because the tire choices are better, in 17 245/40 on 9 and 275/35 on 10 would be close to ideal

in 15
235/45 on 8.5 or 9 and 285/40 on 10 or 10.5