911 widebody wheel fitment help / sizes and offsets 17s

[jimtweet]

I am not the first bit knowledgeable when it comes to offset and such and have been trying to search and haven't found much

I have a customer trying to order some custom wheels

1982 911, 911 stock front suspension with 993TT big read brakes
rear also has 993 brakes.

Car has been flared with stock 930 flares.

he is looking at 17x9 up front maybe 9.5 and 17x11 or 11.5 in rear.

I would like to avoid wheel spacers if possible since new studs have all been installed, but if need to be changed so be it.

[chucksmith]

I got this from Paul at Braid
How we measure:
Rear. Walk up to the car from the side armed with a tape measure extended 20". insert the tape at the top of the arch until it contacts the inner fender wall, missing any oil or ac lines. Look straight down and take the measurement to the outside of the fender. I would expect to see about 14.5"
https://drive.google.com/file/d/1MP1vXu2M5HyR5QgEqU4sl5PvXPXFjV9V/view?usp=sharing




FRONT.
Same idea as the rear except we measure to the flange around the upper strut mount as it's very consistent. I'd expect to see about 11.75".

https://drive.google.com/file/d/1u7xVAE_zUgjHlCaijsBYfp6SzQvVF5_C/view?usp=sharing

[chucksmith]

It is the way he advised on how to measure for a car with aftermarket 930 flares since it can be very variable. If you compare that measurement to turbo or m491 then you can very accurately fit your car . Of course, choice of tires is important also.

[Bill Verburg]

I can provide #s that I've collected over the years,
j
in back the trailing arm adjusters and the oil line on the right are the limiting factors for b/s, no mater the 911 max b/s is ~6", you can gain some extra room by shaving the hardware and relocating the oil line. This is w/ stock 911 rear suspension, the 930 semi trialing arms move the hub out and gain an additional 60mm/side

This s lets you put a huge tire on the back.


The front space is limited by the fender lip, and SC max is ~4.5", 930 fenders add ~2" to that

so max wheel on a 911 suspension/930 body is ~ 6.5"f/s + 6" b/s = ~12.5" w/ a little wiggle room

most don't use the max b/s but want an aggressive lip relation so do use the max f/s or close to it

The question is do you really want to put a huge tire in the back? In 17 there are up to 335//30s available, there are 25.9" OD tires and weigh 32# ea, in other words that suck the energy away from chassis acceleration/deceleration/turning and put it into just spinning up/down/turning the tires. W/ a big motor this may be a desirable tradeoff, but w/ a stockish 3.0, not so much.


I'd have discussion w/ the client about tires before deciding on wheels, choose the tires first then choose the wheels to make the tire fit right




In front you make a similar decision
in the front of a 911 suspension car the backspace is limited by the shocks and the in a turn the inner chassis wall, the shorter the tire the more room, max b/s is ~5.75 "

930 front hubs add 21mm to that
front space on a 911 is ~3.5", 930 fender add ~30mm to that or a little more than 4.5"

so max wheel in front is ~5.75 + 4.5 = 10.25

here is what some other guys ended up w/ the names are withheld to protect the guilty
9x17 ET8 245/40
11x17 ET-31 275/40

9.5 ET23 255/40
10.5 ET6 285/35

9 ET-3 255/40
11 ET-20(aggressive) or-25(less aggressive) 315*35

9 ET5
11 ET17

9 ET17 245/40
11 ET -13 275/40

and lastly '73 RSR
9 ET-3 230/600
11 ET -27 260/600