Ed Hughes

I'm wondering if it's a legal thing, in that they didn't formally test the early 993's with 18" wheels, therefore cannot wholeheartedly bless it? Maybe the numbers of cars involved were too low to do so after-the-fact, and it didn't warrant the expediture to do so, with no value to Porsche? Along the vein of N series tires being the blessed tires. They don't test each and every non-N tire for corporate approval.

SleepRM3

Deleted

peter-997

Quote from the official TI:

"Vehicles were produced within the named VIN ranges which were not equipped with the body structure reinforcements necessary for 18-inch wheels"

Question is: Which kind of body structure reinforcement is that?

Regards Peter

cobalt

This brings me back to ask why they installed them on my 94 turbo which has no reinforcements over a stock 964 coupe. I have never heard of any 94T having issues.

IainM

thanks Peter for that new information. I’d like to read that TI document, can you cite the full title and any reference # so I can get a copy for myself.

Are the “named VIN ranges” it mentions the same as the forbidden ‘95 models in the tech bulletin I referenced in the opening post?

peter-997

Technical Information
6 cyl 1/04 4E 4440
Document 4440_2004_64014e.pdf

The range begins earlier but there are exceptions of further "forbidden" cars.

IainM

IainM

I got the part numbers off my old suspension parts and was doing some searching and ran into this.
this thread gets real interesting around post #50
https://rennlist.com/forums/993-foru...ml#post8143888
Erik & Calvin get into a discussion about rear suspension changes in the mid-95 production.

My part numbers are later so it looks like my PO may have replaced at some time.
Fascinating.


<edit> Calvins initial post is #40, but you get the jist.

IainM

My copy of Tech Bulletin 4440 is dated 2/98 and makes no mention of chassis stiffening. However,I never realized the TB's had so many versions, 911.uk lists 6!
Does anyone have a copy or maybe paste a snapshot of the relevant paragraph? Can't seem to find that specific version
TIA!

Paul Peters

Thread is very informative, My 993 C2 currently has 17" cup wheels, but I recently have acquired set of Hollow body 18" turbo twist wheels I had planned to put on.
From the comments, I've learned that my serial number matches the third production version of named vin serial numbers 99 SS 320478

IainM

Still researching this and now I have a little time (no front shocks) I’ll do a little more digging. I collected all the suspension part numbers from the parts I removed and what was used to replace and there are some significant differences. I’m hoping that this means that whatever kept the Weissach masters up at night was resolved through part updates.
the only unanswered question is whether there were any chassis changes through these VINs

IainM

BTW, the 17” cup wheels are about the lightest wheels out there. Plus 18” rubber weighs a LOT more means you will notice a hint of sluggishness with the 18s
you have to be a very good driver to take advantage of the extra grip from 18” tires

cobalt

I am sorry but I still don't understand the concern. If you look at these as a weight issue it is marginal at best in some cases.

I can only use 8's as a comparison since the 94 turbo came with 8" wide speedlines and that is usually the upgraded size and one of the heavier wheels they used during this time.
Legitimately the 7's drop weigh 2.42 pounds less than the 8's. If you want equal weight the 996 BBS 5 spoke many run are nearly the same weight as the 7" Cup II's but in 18"x8" sizes.

BTW if someone is looking for CupII's needing refurbishment I have a set but local pickup Northern NJ for a nominal fee.

The cup I's weigh 0.22 pounds more than the Cup II's and the 18" speedlines weigh 3.39 pounds more than the Cup II's my 18" fikse's weigh 5.5 pounds less than the Cup II's
If you run a 225 up front and using the weights of a Perelli Pzero Corsa the 18" weighs 0.22 pounds less than the 17's not more. Although you need to check the tire you are planning to use as they vary. This is just for comparison. A PZero has a much stiffer sidewall than a michelin which also is a consideration.

I can't use 7's as a comparison no doubt running a smaller 205 vs 225 would save weight and traction which I would not be comfortable with such a narrow tire up front.
17 x 8 Cup I's with 225/45/17 weigh 44.66 pounds
17 X 8 Cup II's with a 225/45/17 weigh 44.44 pounds
18 x 8 Speedlines with 225/40/18 weigh 47.39
18 x 8 Fikse with 225/40/18 weigh 38.50

There is a difference running the 18" fikse's compared to the speedlines or Cup I's in 8's which I run up front when I run 17's.

As I believe i said earlier I have been running 18's on both track and street for nearly 2 decades on a 964. The 18's are pushed to the limits on track and occasionally some back roads. I have to assume that Porsche didn't test the handling or get TUV approval until the specified date to run them and the lawyers stepped in. If my turbo doesn't have anything different to it than the standard 964 I can't see how there is any issue, just legal crap I suspect and something we don't have to deal with in the US. Although the suspensions did change slightly and the 993 was fitted with aluminum uprights vs the cast iron on the 964 they added additional unsprung weight by using the larger medium S4 caliper vs the standard 964 smaller caliper which basically negates any weight savings over the aluminum uprights.

Use what you want but I wouldn't stress over it.

geolab

hello Iain:

Do not regard the VIN noted in the bulletin. It was only meant for very few early 993's who had early chassis parts. Someone f@cked up with the translation

initial steering rack TSB followed and was part of this one:

https://members.rennlist.com/geolab/...994_640894.pdf

on the first page, the errors are huge regarding model years and you will understand why the phrase in the brace TSb was placed , to cover some changes in new chassis parts.
the error is in VIN model year. DEC93 and JAN94 model year should be RS and not SS, and so forth...