Eplebnista

A search of past threads on the subject of spacers produces evidence that many, if not all, USA 86.5's emerged from the factory with extended lugs and 21mm spacers.

This adds another dimension to the much discussed topic of offsets, how to calculate the same, scrub radius and various ways one can sin when fitting other wheels on a 928.

This leads to a number of hypotheses and questions if one owns an 86.5.

1. Question - Should we assume that the omniscient technical overlords in Stuttgart determined the optimum offset for 86.5's with extended lugs and spacers was 65 as is the commonly accepted stock offset or is there some other optimum offset for 86.5's??????
My car had 16 X 7 65mm manhole covers on the front when I bought it.

2. Hypothesis - since adding spacers ordinarily reduces positive offset, removing a spacer effectively adds positive offset.

3. Question - Is there an argument to be made that if you remove the big fat spacer from the front on your extended lug 86.5 you could mount a wheel with a positive offset as low as 44 ?

I must confess that I may have sinned at least twice. I have mounted front wheels on my 86.5 with 55 and 52 offsets, both times with the OE spacers removed. In both instances if my car suffered from tramlining and other negative impacts of forbidden offsets I was too dull witted to detect it.

Thoughts, opinions, facts and even condemnation are all welcome.

Thanks

FredR

No 928 ever left the factory with a spacer on the front wheels. The offset determines the effective NSR [ Negative Scrub Radius]. As I am aware earlier models have a NSR of 13mm and later models had a NSR of 10mm both achieved by using wheels with an offset of 65mm and different steering geometries. There were a few exceptions in that the CS, SE and 89GT models were equipped with wheel offsets of 60mm but no one seems to know why. The NSR is required to achieve a characteristic intended to enhance safety in that with the correct NSR the car will continue to travel in a straight line if a yaw effect is generated on the front wheels such as when hitting standing water on one side. The earlier models also had a different brake circuit arrangement and this may explain why they specified a greater NSR. The chances of needing this feature are doubtless pretty slim but going sideways at 100 mph with midships heading for a tree is no time to find out it that it was in fact a good idea.

Some models were fitted with rear wheel spacers and appropriate length studs- specifically the GT models with 17mm [?] spacers and the GTS with 38mm spacers. Some earlier models also had rear wheel spacers. Not sure what the 86.5 model had at the rear

Mrmerlin

Happy New Year Otto.
First the front hubs dont have spacers, never did .
The car was designed with ET 65 wheels front and back.
NOTE the wider track changes the Center Of Gravity a bit.
NOTE the rear wheels with the sucked in look are made to accommodate tire chains.
NOTE with a car with factory spacers the studs are also longer
NOTE you will still need a spacer if you fit a ET 45 as the studs will stick further through the lug bolt holes without spacers,
Depending on how much the grip length is on the hub of the wheel will determine if their will be enough threads to screw the lug nuts on if you dont use the spacer,
since the the lug studs are not fully threaded.
NOTE you can use bolt on bolt on spacers on top of the factory spacers if you have a ET65 wheel and want the rim to be kicked out further in the back.

Does that answer everything?

davek9

Otto, did/do you mean Rear spacers, I own a few 85 and 86.5's and never have seen extended lugs and or spacers on the Front wheels, only on the rear wheels starting in 1985 (US).
I use the open lug nuts on the Rear wheels when fitting wider rims then cap them off with standard lug nuts for the stock look.

As far as the offset questions, I cannot address those questions, however I do notice more wondering on worn-out roads with wider front tires.

Dave K.

EDIT: Happy New Year All, looks like I'm typing too slow once again!

Eplebnista

ok, my bad. I saw threads where everyone with an 86.5 said they had spacers. But the threads were about rear spacers.

My car has long studs all around and had 21mm spacers at all four corners. The front wheels were manhole covers with a 65 offset. Therefore when I bought my car was I driving around with a 44 offset?

If that's true, we somehow both survived until I pulled the spacers off.

I am dealing with the long lugs by using open lug nuts and covering them up with chinesium lug nut covers painted to match my wheels.

Bertrand Daoust

I would say yes to answer your question.
Now, how was the car driving with that set-up compare to now without the spacers and 65 mm offset?
Btw, a Happy New Year to you and Robin!

FredR

Offset is defined by the wheels and whether you use a spacer is irrelevant to the offset concept.
A spacer impacts the track (width) of how the wheels sit on the road.
If a previous owner fitted longer studs and 21mm spacers upfront that would change the scrub radius by 21mm and thus transform the value from a negative value to a positive value. I suspect your MY has the same steering geometry as the S4 and if correct that would transform a NSR of 10mm to a positive value of 11mm. That might be useful for a track centric 928 but not a good idea for a street car driven in all kinds of conditions.

Eplebnista

You are correct sir. I perhaps should have said "effective offset."

928cs

For the CS/SE/1989 GT, 944 Turbo 17mm spacers were fitted on the rear axle, with regular studs, as they are double-bolted spacers.

linderpat

Interesting. Like Dave and Fred said, the fronts did not come from the factory with front spacers. Once you remedy this, you may notice a big difference in how your car drives and handles.

Babado

Hi guys, I want to make sure I understand what I need for my 86.5, please help me out, I'm confused!!

I just purchased ET65 16x7 and ET60 16x9 Club Sport wheels, I know the front are fine but now I'm curious about the rear. I assume after looking at my original window sticker ( wide track option) I have 21mm rear spacers, current 7x16 have 225/50x16 tires, which measure 9.2" in width, the new tire 245/45x16 will measure 9.6" wide. I currently have more than .6" between my current tire and the wheel well. ET60 is 5mm = .197"

So, as I figure it, I'll have .597" of additional tire width in the wheel well?

Will these mount up without additional lugs, smaller spacer removing the spacer, etc?

I do not want to roll the fenders if I don't have to.

Thank you

Mrmerlin

to figure out the size spacer you need for the rear,
put on the wheels tire package you have chosen then settle the car
measure from the outer tire side wall to the inner edge of the outer fender lip. convert this to MM
Measure both sides with your car you should be able to fit the 21mm factory spacers and wheels.
use the measurement that is lower,
EG Left side 18 MM Right side 22MM
Then subtract 5 MM from the lower number.
EG 18mm - 5 mm = 13mm
this will give you the max spacer that you should fit = 13mm

NOTE if the wheel /tire is closer than 5 MM from the fender edge,
then get leather gloves and put both of your hands side by side inside the fender lip,
and gently pull the lower edge of the fender work a wide area front to back ,
so that things are even.
You will see the fender edge come out away from the tire by about 4 to 5 mm.
NOTE use both hands so your pulling force is widely distributed.
You can add on bolt on spacers to the factory spacers

IIRC the thinnest bolt on bolt on spacers are 17mm
HnR makes good bolt on bolt on spacers in a few different sizes

NOTE the rear wheels work in an arc ,
so as the wheel is compressed up,
it has the top outer edge of the tire arcing inwards

Babado

My simple brain says current tire and stock wheel measures ( tire 9.2" wide) 1.25" from inside wheel well, new tire is 9.6" plus the .197" increase in wheel push out .197" ( et65-et60) is .597" .

I should be good with .5"+ from wheel well?

Thanks Stan or anyone else who responds, can't test fit for awhile and want to have anything I might need.

Mrmerlin

make sure to test fit the wheel/ tires before you get the spacers.
it will be easier if you convert your measurements to mm,
as thats what the spacers and wheels are

Babado

21mm spacers are a standard option on my 86.5 (installed, widened rear track) currently 31.75mm inside lip to tire. New tire, additional 10.16mm + .5mm for ET60mm from ET65mm, 31.75mm -15.16mm = 16.59mm I should be good to go correct?