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larthe
Newbie


Joined: 18 Oct 2016
Posts: 6
Location: Linkoping, Sweden


PostPosted: Tue Oct 18, 2016 6:26 pm    Post subject: Fuchs 16" woes Reply with quote

Hi all!
Here's a problem that I have tried my best to ignore for the past 10 years: My Carrera -88 was originally delivered with 15" Fuchs rims, but since there was an option for 16" in the specs, I started a search for new rims. I soon found a set of beautiful 16" Fuchs that had once sat on a 944, but when put on my 911 I immediately saw that they would not work. That's how I learned about the ET (Einpress Tiefe, i.e. offset) specification. I returned the 944 rims and got my money back and finally located a set with the correct specification. (16"/7" ET 23.3 mm in front and 16"/8" ET 10,6 mm in rear as I recall, Porsche part numbers 911361020 44 and 911361020 43 respectively).

These worked well, but after wearing out the original set of tires and fitting Bridgestone Potenza S-03 my troubles began. Or at least I think that was when they began. I believe the tires are of the right size (205/55 ZR16 in front and 225/50 ZR16 in rear), but when I hit a compression in the road, the front tires will scuff against the fenders. It works well on the race track, so "normal" driving will not cause any harm, but apparently bumps in the road causes the suspension to compress more than does tight cornering. The way I drive this only happens perhaps once a year, but it removes some of the joy of driving. My current theory is that it's because the S-03's are quite bulgy and extend a good half inch outside the rim at the broadest point. This is good for protecting the rims from curb scratches, but bad for the fenders. So even though the S-03s have the right specification, they are unsuitable for the car.

Anyone who recognises this problem? I could of course roll in the fender edges, but I have tried to keep the car as stock as possible, so the next thing I would try is a set of new tires. The rear tires are almost worn to the limit anyway, but the front tires are good for many more years of driving so it is a bit annoying. Does this seem reasonable, or am I barking up the wrong tree?

Cheers!
/Lars
 
  
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Gazc2
Barcelona


Joined: 08 Nov 2003
Posts: 1406
Location: Scotland


PostPosted: Tue Oct 18, 2016 7:09 pm    Post subject: Reply with quote

Lars,

think you need to have a look at your suspension settings (Camber) condition etc, you should have no problems with that wheel/ tyre combination.

This was the same size as I had on my 89 3.2 targa

cheers

Gaz
_________________
2007 997 Turbo & 924s in progress
1990 964 C2
1989 3.2 targa
1987 3.2 Cab
1986 3.3 Turbo
1986 944 2.5 (later fitted with a 2.7 after wife went scuba diving in a flood and popped a piston through the block)
 
  
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igaffz
Albert Park


Joined: 27 Dec 2011
Posts: 1664
Location: Newcastle upon tyne


PostPosted: Tue Oct 18, 2016 9:43 pm    Post subject: Reply with quote

I agree with Gaz, put some new shocks and springs on, my 964 was catching till I fitted konl fsd's now it's fine.
_________________
Horizon blue, 964 carrera 2 tip, lowered on koni's, k&n, de-cat, cup pipe, leather trim and 18" 3 piece split rims.
Silver 928 S2, B reg, manual.
Guards red 944 lux, the new project!
 
  
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larthe
Newbie


Joined: 18 Oct 2016
Posts: 6
Location: Linkoping, Sweden


PostPosted: Tue Oct 18, 2016 9:58 pm    Post subject: Reply with quote

Thanks for the suggestion, I will take it up with my local Porsche garage. Maybe they can do some measurements. I didn't know you could make adjustments big enough to impact this problem, but it is definitely worth looking into. I didn't thinks of this as I would have expected uneven wear on the front tires if things where really off-

Thanks!
/Lars
 
  
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larthe
Newbie


Joined: 18 Oct 2016
Posts: 6
Location: Linkoping, Sweden


PostPosted: Fri Oct 21, 2016 1:05 pm    Post subject: Reply with quote

Hi again!
I feel a need to bump this thread after more carefully studying the specs. It says the Carrera is specified to have either 195/65 tires on either 6J or 7J x 15 rims, or 205/55 tires on 6J x 16 rims, so it seems my 205/55 on 7J x 16 rims are out of spec. There is no note of offset for any of these combinations in the Driver's Manual, but I would have expected it to be the same for all. I'm not quite sure where I initially got the 23.3 mm offset number, so if anyone could confirm or correct that I would be very grateful. I don't really understand why a 7J rim with the same offset as a 6J rim would cause a wider profile with the same 205/55 tire, but my guess would be that in my case the offset is wrong?

Looking at the Turbo and Turbo Look model, the spec calls for 205/55 on 7J x 16 rims in front and 245/45 on 9J x 16 rims in rear, so it seems my rear wheels are somewhere in between the Carrera and the Turbo, whereas my front wheels are standard Turbo. I know that the Turbo has wider fenders in rear, but does it also have wider fenders in front? That would (to some extent) explain my problem, but as I sad: why would a wider rim, with the same offset and the same tire, cause problems? Is it the offset that is wrong after all?

Cheers!
/Lars
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911 Carrera 1988
 
  
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Marky911
Imola


Joined: 04 Jun 2009
Posts: 850



PostPosted: Fri Oct 21, 2016 3:27 pm    Post subject: Reply with quote

The Turbo does have wider fenders allround but it also has wider suspension arms, driveshafts etc, so turbo wheels usually always fit the narrow bodied cars too.
It sounds to me like your static sag, ride height when still is too low, which once on the move is even lower due to bumps and compression, or as mentioned your shocks are worn out. Or both.

Your car doesn't have springs it has torsion bars. The positive of this is that you can simply wind a nut on them to raise or lower the car. Try winding them up 5mm and see how you go until you can fit new shocks.
 
  
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larthe
Newbie


Joined: 18 Oct 2016
Posts: 6
Location: Linkoping, Sweden


PostPosted: Tue Oct 25, 2016 10:12 am    Post subject: Reply with quote

I can't really see how the ride height would have any impact on this, provided that the scuffing does not occur on even roads, regardless of steering angle. The suspension has a certain geometry in its movements that won't change with ride height. Even if I jack up the ride heigth, I might still hit a bigger bump, causing the suspension to compress more and be back where I started.

So I still think the problem is the offset, or possibly camber angle.

Thanks!
/Lars
_________________
911 Carrera 1988
 
  
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grbspeedster
Nürburgring


Joined: 11 Nov 2007
Posts: 460
Location: Rugby


PostPosted: Tue Oct 25, 2016 10:51 am    Post subject: Reply with quote

Many years ago I had a similar issue on my SC again after changing tyres. I was pointed to a document on tyre specs ETRTO which effectively had a standard for tyre manufacturers to produce to. I believe my issue was new tyres were at top of spec on width hence causing issue. Do you know anyone with same car you could swap wheels for test?
_________________
Geoff
996 X50 turbo cab
Jaguar XE R Sport
IQ3
Lunar Motorhome
 
  
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larthe
Newbie


Joined: 18 Oct 2016
Posts: 6
Location: Linkoping, Sweden


PostPosted: Tue Oct 25, 2016 11:10 am    Post subject: Reply with quote

Thanks for the tip! I found the document and here it says the offset should NOT be 23.3 as I have thought, but rather 36! The 7Jx16 I have, with 23.3 mm offset are for the Turbo front or the Carrera rear. There you have it, I will have to start looking for new rims.

Odd that I never had any problems with my 8Jx16 in the rear...

Thanks!
/Lars
_________________
911 Carrera 1988
 
  
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g7jhp
Trainee


Joined: 04 Sep 2005
Posts: 91
Location: Herts


PostPosted: Mon Nov 07, 2016 3:35 pm    Post subject: Reply with quote

I ran turbo 7x16(f) & 9x16(r) wheels on my 1987 3.2 Carrera coupe with no issues. They do make the steering heavier but I had no rubbing, even over speed bumps.

The 6x16(f) and 7x16(r) were standard (plus 8x16r on later 88/89) narrow bodied 3.2 Carrera.
_________________
Current:
996 turbo X50

Previous:
3.2 Carrera (No.1), 993 C4, 3.2 Carrera (No.2)
 
  
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IMI A
Österreich


Joined: 02 Aug 2014
Posts: 996
Location: United Kingdom


PostPosted: Mon Nov 07, 2016 6:18 pm    Post subject: Reply with quote

g7jhp wrote:
I ran turbo 7x16(f) & 9x16(r) wheels on my 1987 3.2 Carrera coupe with no issues. They do make the steering heavier but I had no rubbing, even over speed bumps.



+1 no probs at all road and track with turbo 7x16(f) & 9x16(r) on Carrera 3.2 including the 245 rear and 205 front tyres. I also run Bridgestone S03 Confused
 



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86wasagoodyear
Newbie


Joined: 13 Jan 2017
Posts: 2



PostPosted: Fri Jan 13, 2017 6:37 pm    Post subject: Reply with quote

I have an 86 3.2 with a wheel story similar to yours.

When I bought it, it was on 17" 964 Cup wheels, far too big for the car, steering was impossible & I had wheel arch rubbing when cornering hard. Clearly new wheels were needed.

Since Fuchs don't make new 16" wheels nowadays, and original Fuchs cost a fortune, I got Braid BZ replica Fuchs from Design911 in UK, 16x6J ET35 front & 16x7J ET23 rear. My tyres are Bridgestone S02 205/55 front & 225/50 rear.

This setup is great, matching original spec very closely. The BZ wheels are also very lightweight. Problems solved :-)
 
  
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