Wheel and Tire Size Advice

[rarelement]

A couple of years ago I purchased this glorious ‘75 911 S Targa that had been breathed on by Farnbacher Loles, improving the 2.7 to RS spec with twin plug heads ported, polished and flowed, ’73 S cams, overhauled transmission with short shift, Targa chassis braces, anti-roll bars, adjustable torsion bars, and, among too many other mods to mention here, four Michelin Pilot Sport tires mounted to beautiful 16x7 black on black Fuchs with stainless rims.

When I got the car, almost immediately, I heard something whirring/rubbing. Especially if someone was riding in the car with me and more especially if anyone was in the passenger side back seat (come on, everyone wanted a ride!). Basically, the right rear tire sidewall was rubbing on the inside of the wheel well body. Then it wasn’t just there but the sidewall of the driver side front wheel. That alarms me because – turning!

http://forums.pelicanparts.com/uploads24/photo+21429558653.jpg


I’ve taken it to a couple reputable local vintage Porsche shops but there doesn’t seem to be a huge consensus to what the problem really is. So the issue I have is, should the car have these size wheels and tires? It almost seems like I should reduce the wheel diameter or tire width but one complication I’m sure is the ’84 Carrera front rotors with aluminum calipers (I told you there were many other mods). Did they oversize the wheels to fit the later rotors and calipers? Obviously Farnbacher Loles is long gone so I can’t ask them.

I wouldn’t be outraged to resize, especially if I could add my own touch to the car – specifically a set of Group 4 replica PAG wheels in the right size – and get the Fuchs to a good home that would appreciate them. Or is it just a tire size issue? What am I missing? What do you recommend?

[Arne2]

What tire sizes are you running? That is at least as important as the wheel size.

[Ayles]

Only problem is the pags only come in 15" sizes right now. I want them but tire choices are SLIM.

Post some more pics, sounds like a sweet car!

[Bill Verburg]

Originally Posted by rarelement

A couple of years ago I purchased this glorious ‘75 911 S Targa that had been breathed on by Farnbacher Loles, improving the 2.7 to RS spec with twin plug heads ported, polished and flowed, ’73 S cams, overhauled transmission with short shift, Targa chassis braces, anti-roll bars, adjustable torsion bars, and, among too many other mods to mention here, four Michelin Pilot Sport tires mounted to beautiful 16x7 black on black Fuchs with stainless rims.

When I got the car, almost immediately, I heard something whirring/rubbing. Especially if someone was riding in the car with me and more especially if anyone was in the passenger side back seat (come on, everyone wanted a ride!). Basically, the right rear tire sidewall was rubbing on the inside of the wheel well body. Then it wasn’t just there but the sidewall of the driver side front wheel. That alarms me because – turning!

http://forums.pelicanparts.com/uploads24/photo+21429558653.jpg


I’ve taken it to a couple reputable local vintage Porsche shops but there doesn’t seem to be a huge consensus to what the problem really is. So the issue I have is, should the car have these size wheels and tires? It almost seems like I should reduce the wheel diameter or tire width but one complication I’m sure is the ’84 Carrera front rotors with aluminum calipers (I told you there were many other mods). Did they oversize the wheels to fit the later rotors and calipers? Obviously Farnbacher Loles is long gone so I can’t ask them.

I wouldn’t be outraged to resize, especially if I could add my own touch to the car – specifically a set of Group 4 replica PAG wheels in the right size – and get the Fuchs to a good home that would appreciate them. Or is it just a tire size issue? What am I missing? What do you recommend?

wheel width and offset as well as tire width and height determine fitment
from the pic it looks like the correct o/s rear flares aren't fitted, this will further limit wheel and tire choice

I suspect that the rear wheels may be 8ET23.3


w/ correct SC/Carrera rear flares you would use 8ET10.6 or 9ET15 rear wheels which have inner lips that sit further out board but which also have outer lips that sit further outboard and require that the flares be present to provide room.

the ET23.3 issue is probably compounded by a wider than usual tire.

w/ out adding flares eben a 7ET23.3 is a tough fit and would want as short a tire as possible to avoid hitting the fender or lips.

Best solution is to add SC/Carrera rear flares and use spacer on the existing wheels or get correct 8ET10.6 or 9ET15 wheels

[rarelement]

Originally Posted by Bill Verburg

wheel width and offset as well as tire width and height determine fitment
from the pic it looks like the correct o/s rear flares aren't fitted, this will further limit wheel and tire choice

I suspect that the rear wheels may be 8ET23.3

w/ correct SC/Carrera rear flares you would use 8ET10.6 or 9ET15 rear wheels which have inner lips that sit further out board but which also have outer lips that sit further outboard and require that the flares be present to provide room.

the ET23.3 issue is probably compounded by a wider than usual tire.

w/ out adding flares eben a 7ET23.3 is a tough fit and would want as short a tire as possible to avoid hitting the fender or lips.

Best solution is to add SC/Carrera rear flares and use spacer on the existing wheels or get correct 8ET10.6 or 9ET15 wheels

Thanks everyone, I did regretfully omit the tire size which is 205/55 ZR16. The previous owner even had 225/50s mounted in the back which bumped the flare, dimpling it and convincing him to go to the smaller tire (which obviously still don't work).

I didn't do enough homework before posting this but seeing your reply about the 7ET23.3 got me doing my research and I came upon this post: 15x8 fuch wheels up front? which has been very helpful.

The car is originally an S Targa, so I imagine the flares are not SC/Carrera and without going through a whole bodywork exercise, I think the smaller wheel/smaller tire route is preferred. Even just this single post How to make widebody 911 steering feel like a narrowbody 911? shows how out of my league this decision is. I don't know what Farnbacher Loles did to the suspension so I may need to start from scratch with some forensic measurements before making a final decision.

For what it's worth, here's my post in "Show us your browns" for more photos of the Targa: Show us your browns