gandalfthegray.

I'm looking at a set of Cayman 19" wheels, the fronts are 19 x 8 with 57 offset and I know that works. The rears I believe (waiting for confirmation from seller) are 19 x 9.5 wit a 46 offset. I've got an 86 928. From what I've read the Boxster / Cayman wheels are 928 friendly but just hoping someone here can confirm fitment. I'm ok with using a spacer if needed.

Thanks!

FredR

When you use the word "works" what exactly do you mean? When it comes to wheels and offset there are two concepts- "fits" and "works". Fits means as the name suggests- they fit. "Works" in my vocabulary means they achieve the original Porsche design intent in terms of negative scrub radius and even that definition is "questionable" as Porsche were not consistent fitting front wheels with the same offset. Most factory fitted 928 front wheels have an offset of 65mm for a very specific reason and yet on models like the CS, The SE and the 89GT they fitted forged magnesium alloy wheels with ET60 up front.

The intent behind the NSR [negative scrub radius] is safety related. If one is zooming along at speed and hits standing water on the near side [as can often happen given the road profile in a wet climate is usually designed to drain water from the crown] the car will tend to yaw due to the additional drag on the near side rubber. The NSR concept by design negates the "yaw" component and thus a 928 with the correct NSR wants to carry on in a straight line if and when such happens

For whatever it is worth I have never come across a case where an accident happened because a 928 did not have the correct NSR on its front wheels but then if such did happen would they know and would they admit to such? Indeed for track cars I understand the car will handle slightly better with a small positive scrub radius such as ET52 will generate but then races do not take place in standing water do they? Do they even hold races in wet weather Stateside?- we do in Europe or they would never happen but they are deferred if there is standing water on the track.

A zero scrub radius [ET55] apparently leaves the car with a tendency to tramline. I have used front wheels with ET52 and personally did not like the way they felt but such offset with stock size rubber fills the front wheel well very nicely and looked excellent with 18 inch reverse spoke wheels that were off takes from a Boxster or whatever. I sold them to a friend for his 993 C4 and used the funds to purchase my three piece forged alloy wheels with ET68 up front but that is another matter.

Regarding whatever it is you intend to purchase all I can say is that from a personal perspective I hate the look of 19 inch wheels on a 928- they just do not look right and I would go for 18 inch rims for better tyre selection options. With offsets that are too small to start with the last thing you need are spacers. ET 57 will give a small NSR of 2mm - plenty of folks have used such and are perfectly happy with them. Do they fit?- yes they do- do they work?- not as Porsche intended.

I take the point of view that the last thing a 928 owner needs to find out is that he has the wrong offset front wheels when going sideways into a wall at 100 mph but that is just my way of thinking.- each to his own etc etc.

Mrmerlin

I would suggest that you find a set of 17 or 18 in wheels for your 928 .
Anything higher than 18 is a poor choice for many reasons

icsamerica

19's ? ... for looks or performance. If for performance... read on.

The offsets are OK, not ideal. The fronts will be close to rubbing on the fender lips, more so if lowered. If you have the OE spacer typically found on the rears of your year 928, the the rear might be ok but tight on the fender lip also. Bottom line those offsets are a real compromise, not ideal. Panamera with the 59 ET fronts are better.

I can tell you from experience the firmness of a 19" performance tire will make any deficiencies of the other rubber in your suspension very noticeable. You will also get a rough ride with 19's becasue you will need to run a very low aspect tires to get the diameter correct. 19's are Probably OK for the smooth roads down south but punishing on more northern roads. Keep in mind there are lots of 17 / 18 inch tires with high load ratings that will work great on a stock 928.

Full disclosure. I run 19" Cup 2's with a larger diameter than OE but I track my car and I also upgraded the majority of the bushings in my car with poly and have a re-worked rack to handle the loads. A 928 handles and feel amazing this way and I believe it's how Porsche should have built it. The ride is very acceptable because I'm running a taller tire. Somewhat necessary / advisable because Cup 2's are hard to find in certain sizes and easier to find in sizes typically found newer high performances cars.

I think what I'm trying to say is if you go down the 19" performance tire spiral all other aspects of the suspension really have to be up to snuff and / or upgraded IF you care how the car drives, feels and reacts to small steering inputs. Some of these upgrades are easy to do like the 4 rack bushings and front lower control arm. But some of the other ones that are really and very necessary like upper control arms and internal rack bushing additions / upgrades, are far more difficulty. Be prepared and possibly do the upgrades first.

Rich9928p

Wheels from other Porsche models don't fit the front of 928's. The standard Porsche 928 factory offset was 65 mm (front) through the entire 17+ year production run. It has a more advanced a-arm suspension...other Porsche models use "strut" front suspension, and those late model ones have tended to have offsets in the 52-55 mm range. Pushing the wheel OUT a half inch, when, if anything, it would be better to go IN!

The rear wheels Porsche 928 wheels are offset 50 - 55 mm.

Rich
928 Owners Club Membership Chairman
1993 928 GTS cover girl
1987 928 S4
1979 928 5-speed rescue cover girl
1979 928 Euro track beast

hacker-pschorr

Not quite..... also wheel width must be factored into the formula.

• 1989 GT wheels are 8x16 et60 (backspacing of 162mm)
• D90's are 7.5x16 et65 (backspacing of 160mm)
• Phonedials are 7x16 et65 (backspacing of 154mm)
• 997 wheels 8x18 et57 (backspacing of 159mm)

The last time I checked, the 89GT wheels are very sought after.

I agree 19's are too big, if not for any other reason tire selection is very, very limited. 928's diameter is 25" all around, you don't want to go bigger.
The two front tire sizes without going over are:
225/30-19
235/30-19
The Tire Rack doesn't sell any tires these sizes so your only option is going 245/30-19 on the front, cheapest (of the only two tires available that size) is $288 each.

18" wheels open up a lot of tire options and 997's came with 18x8 et57 which a lot of us are running. There are other Boxster & Cayman wheels over the years which are 17" and 18".

gandalfthegray.

Lot's of good info, but I'm still not sure I understand. So I'm only using the car for a weekend cruiser, no track event or long drives. I've got a Boxster with 19's and another car with 20's so not to intimidated by a harsh ride. The 19's I'm looking at are the Carrera Classics which I felt we're the best looking wheel set up I found on the coolest wheels thread but I'm assuming the rear 9.5 wide 46 ET doesn't fit. Second choice was the 18" Carrera Light Weight 5 spoke wheels but they appear to have an offset of 51 on the fronts so I guess that doesn't work either. Don't really care for twists (which is what I have). Is there a 5 spoke wheel that works?

Peter F

I think you made a typo on this, should be 8x16 et60 not 17.

Not quite..... also wheel width must be factored into the formula.

• 1989 GT wheels are 8x17 et60 (backspacing of 162mm)

hacker-pschorr

The wheel size is only half the equation, you need to look at the tire size too.
A modern Boxster which comes equipped with 18, 19, and 20" wheels have an overall diameter over 26". A 928 maxes out at 25" So while a 718 Boxster with 19" wheels has a 235/40-19 tire, a 928 will need to be on a 235/30-19 tire (if you can even find a tire this size).
That's a full inch shorter in sidewall height.

Modern cars are running on much larger wheel / tire diameters.

Rear fitment there's a lot of wiggle room. An et that low you can use a spacer to gain more room. 9.5" wide is not problem on a 928. I'm running 11x18 et51 on the back of my 87.

It will "fit" depending on tire size you go with, but as others have pointed out, the further away you get from a stock combination the greater the chances you'll have negative handling effects.

There's a few 18" 5-spokes to pick from, here are a few.
On my 87 with 11's in the rear:
https://www.alloywheelsdirect.net/po...iii_wheel_1706
I'm tempted to buy a set of these:
https://www.alloywheelsdirect.net/po..._iv_wheel_1704

https://www.alloywheelsdirect.net/po...r_4_wheel_5966
https://www.alloywheelsdirect.net/po...n_3_wheel_5967


Nice catch, thank you.

gandalfthegray.

Hacker, thanks again for the info.

I decided when I got home last night to pull off a rear wheel and see what I had. The twist wheels have an offset of 47 and are 9" wide. This being the reason they don't fit. What I found interesting is the car has what appears to be an inch wide spacer and very long studs. Not really sure why they did this. Also to note, if you pull the spacer off the twist wheels fit perfectly on the car. Brake clearance is perfect as well. Removing this spacer would give a lot more wheel options. Has anyone done this? Could you not simply cut down or replace the long studs?

Mrmerlin

Hold on, your car has a wider track rear and it has factory spacers with the longer studs, this was factory option with the S package
you can buy open ended steel lug nuts with the ball seat if the studs are threaded down the shank you will need to fit a wheel without the spacer to see this.

NOTE cutting the studs will destroy them, and to fit new studs will mean the wheel bearing will need to be replaced,
this is not an easy task,
New wheel bearings are going for about 120.00 each and take a few hours to install with the proper tools.

FredR

If your only problem is the spacer on the rear wheels just remove the thing and then do one of the following-
1. Get 10 open lug nuts and bolt them up- would not appeal to everyone
2. Get a single open nut, thread that onto the stud and then cut the stud length by the width of the spacer using a dremel- remove the open lug nut to help clean up the threads.

I had a similar problem in that my non stock rear wheels when fitted to the GTS with the 38mm GTS spacer were marginal on fender clearance so I mounted a 24mm spacer and use open nuts. However in my case the differential was 14mm so not as profound and I also wanted to retain capability to use the stock GTS wheels in the future.

hacker-pschorr

Listen to Merlin, this is a factory option and open lug nuts are a much better option than cutting down those studs.

You have the ideal setup, in the event your new wheels need a spacer, you've got the extra stud lengths which are preferred over bolt on spacers (I have 1.5" bolt on spacers on my 79 with phone dials).

gandalfthegray.

Studs are threaded all the way down. They would have to be cleaned up however. The open nut would work but you will see the studs protruding out past the face of the wheel which won't look very good.

Aren't all 928s

'S' models in 1986?

Billu

You need to pull the spacer off to see if the threads go all the way.