paalw

Interesting thing this X38 option. We (Jaktomaten and myself) measured the fenders width on his X38 compared to my regular GTS and they come in at the exact same 435mm from hood to top of wheel arch, in horizontal line. On the X38 fender there's "38" stamped in the fender where it meets the frame under the hood. So surely there must be some difference.

Jaktomaten

The width of the fender itself seems to be the same. Is it maybe a difference in design? I will meet up with som other 928 owners in the coming week and will try to figure it out.

Jaktomaten

You are probably right. Just wishful thinking from my side. Would be fun to track the others down. By the way, mine also has the “passenger side console phone mount” but it’s not specified as X21 for my car.

Darklands

I discussed the x 38 front fenders with Jochen today and he is the meaning it‘s only a layed edge on the wheel house from factory., nothing more!

German language is difficult, in Robs German advertise card on the picture the meaning of the extension could also be the rear fender.

“The body has fender extensions (there?) and 8*17 front wheels!“

Arnoud

Here is my 0,028€ , given that my car also has the X38 option from the factory.
1. These X38 front fenders, that have a metal number stamp "38" in them around the middle where the cross-brace is , are made from aluminum - being the same as the normal front fenders. Easy to test with a magnet, etc.
2. Having checked the contour of the widest point (during June 2011 already), I found absolutely no difference with several other GTS's normal front fenders at that time.

3. My car did came with 8" wide front rims Cup-II's, instead of the normal 7.5". I can not remember the offset "from the top of my head"...

Jerry Feather

I wonder if the difference is that the "wider" Fenders are actually wider on the inside rather than the outside. That would probably mean that the wheel arches on the 38, are rolled under and perhaps with a bead rolled inside the edge, giving a wider inside for more wheel/tire clearance.

Jerry Feather

[QUOTE=Darklands;. . . it‘s only a layed edge on the wheel house from factory., nothing more!“[/QUOTE]
. .
Karsten had it figured out also. I didn't catch his post about it because here we commonly refer to this kind of thing as being "rolled" rather than "layed" (laid).

Darklands

I‘m native German speaker, need to shake my head to find the right words!

Michael Benno

Thanks for helping to decode the specifics of the X38 option as a rolled fender for extra clearance to use the wider and more offset rim 8Jx17 ET52 noted above. What is interesting to me is that I have used that exact dimension rim on two 928's. Neither car had the X38 option nor had the fender rolled. Neither car had issues using that size wheel. Maybe there is less gap tolerance but no evidence of rubbing.

Jerry Feather

Michael, I suspect that the Factory has a much wider tolerance for these kind of things -- tire and fender clearance -- than you and I and many of us, probably based on warranty and liability considerations, and that would give rise to the X38 fenders for those wider wheels and tires.

Bigfoot928

anyone have the profile of the backside for reference with the fender liner removed? later cars had rolled rear fenders and this might have become a standard feature at some point.

Gary Knox

3. My car did came with 8" wide front rims Cup-II's, instead of the normal 7.5". I can not remember the offset "from the top of my head"...[/QUOTE]
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The 8" cup II wheels have an et 70 offset. They primarily were used as the 'winter wheel' for the rear of 911's (standard wheel was the good old 9" like 928's have). Narrower wheel, narrower tire, better tire/road contact in the snow was the reason for their development. I have a set of these 8" wheels for the front of my '95 (and had a set also for the previous '94, which I sold with the car).

Gary

Jaktomaten

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The 8" cup II wheels have an et 70 offset. They primarily were used as the 'winter wheel' for the rear of 911's (standard wheel was the good old 9" like 928's have). Narrower wheel, narrower tire, better tire/road contact in the snow was the reason for their development. I have a set of these 8" wheels for the front of my '95 (and had a set also for the previous '94, which I sold with the car).

Gary[/QUOTE]

Here are some photos of my “X38” front rims. I’m not by the car right now so I can’t check the wheel arches. I’m pretty sure the edge on the inside feels rounded or tight folded in on the top, definitely not a 90° angle.

Gary Knox

Hmmmmm! that 8" et 52 wheel would have been strange as original equipment on the 928, as that offset significantly changes the scrub radius for the steering (I also have a set of 18" OE Porsche Sport Design wheels with 8" et 52 offset for the front)

The 17X8 et 70 offset CupII wheel essentially locates the center of the front wheel in exactly the same place as the 17X7.5 et 65. Therefore the scrub radius is unchanged. I drive the '95 with both the 17" Cup II wheels and the 18" Sport Design wheels. I like the appearance of the Sport Design wheels on the car (avatar pix), but it drives much better with the Cup II's (either 7.5 et65 or 8 et70 on the front).

Gary

hernanca

Let's be careful with our terminology. I agree the 8x17 et70 wheel is great for the 928 at the front. However, by definition the et70 places the wheel centerline 5mm further inward which most seem to agree is good for a street driven 928. This will give a 5mm (I believe) more negative scrub radius than an et65 wheel.

The important 8inch et70 fitment which ends up within1.35mm of the et65 7.5 inch wheel is the location of the outer face of the wheel. I believe that is the "essentially...same location" that Gary is referring to.

Calculations: The et70 wheel is a half an inch wider than the et65 wheel, so the et70 is 12.7mm wider. That additional width is split in two to determine where the new face location and inner wheel location sits relative to the centerline, giving us 6.35mm further out for each relative to the wheel centerline. If the wheel centerline were in the same location (that is, if it were an et65 8 inch wheel), then that would place the face 6.35mm further out than the 7 5 inch wheel. However, since the et70 tucks the wheel in further into the wheel well by 5mm, it only brings the wheel face 1.35mm out.

rennlist scrub-radius thread


^^^ 928 S4 Suspension


^^^ Note location of centerline wrt left (inner) end of spindle shaft