Problems With 95 993 Handling?

[larrybard]

There's a disturbing (for me, since I own a stock 95 993) thread on Rennlist ("95 993 DE Car") concerning supposed handling problems in the 1995 993 that were apparently corrected in later models:

http://forums.rennlist.com/rennforums/sh...ge=1&pp=15

Among others, Joel Reiser (PCA Tech Committee) asserts that the car "can get into a mode where it suddenly tugs back & forth on you in a high speed corner. If that happens, you are in deep trouble. Porsche also found this problem during the testing during development of the 993 Turbo."  One theory is that this occurs because the "multi-link rear suspension design causes the (loaded) outside rear wheel to have additional toe-in during cornering"

Modifications possibly costing a few thousand dollars are suggested.

Needless to say this is disquieting.  Is anyone TR familiar with the alleged problem and have any opinion/guidance concerning it?  I know there are several 993 owners who track their cars (e.g., Jack), but am not sure whether they own stock 1995s.

Larry

[smankow]

Larry, sounds like a good reason to modify the car

 

[jakp993]

Larry,

I never tracked my 993 in a stock configuration.  I updated it to PSS9's before taking it out on the track. 

However, the issues they are talking about in the Rennlist thread really doesn't have anything to do with the shocks.  They are talking about the rear control arms and camber links in a lowered car.  I drove my lowered, early '95 (manufactured on '94) 993 on the track for a couple of years with the stock control arms and links.

I can honestly say I never felt that the rear of my 993 was "evil", even on our bumpiest tracks.  I have had my share of spins in the car, and as much as I would love to blame it on something inherently wrong with the car, I think driver error was probably more to blame.

However, I did experience very abnormal tire wear in the rear.  I would chew thru the inside edge of my rear tires in less than 2 weekends, sometimes in a single weekend.  It looked like someone took a file to the edge of the tire and hacked it away.

I consulted with several folks and decided to replace the stock rear camber links with ERP adjustables that use sperical bearings vs. rubber bushings prior to last year's season.  That did the trick as my rear tires now exhibit what I consider normal tire wear.  The car does feel more planted and stable, but it's impossible for me to say it's totally due to the ERP links as I also upgraded to Moton's at the same time.

One of the folks I consulted with was Bill Dougherty.  He did say that Scott Tuder's 993 was "evil" before they changed those links.  OTOH, I have not heard "evil" from folks like Bruce Reim, Chip Grimes, Jamie Allen, or John Raidy, all of which have competently driven early, lowered 993's with stock camber links.

Bottom line is swapping our the stock rear camber links can't be a bad thing.  However, from my personal experience, I would not call it essential.  I stress that this is only my personal experience and I would readily defer to an expert source like Joel Riser.

Take care,
Jack

[larrybard]

Jack,

Thanks for the helpful and somewhat comforting response.  Although I will never drive the way you do, and (for better or worse) it's unlikely I'll intentionally be driving at or in excess of 8/10ths, it would be disturbing to think that if I inadvertently approached or even exceeded the car's limits (as particularly green drivers probably do from time to time) I might encounter quirky, even dangerous handling.  So maybe, as sort of insurance, a few changes, e.g., replacing the rear camber links, merit serious consideration, especially if that change might have the ancillary benefit of increasing tire wear.

Larry

[Not Evil 993 - AFAIK]

[jakp993]

Larry,

FWIW - I didn't start having those tire wear issues until I really started to push the car.  It took me about a year to truly transition from the RX-7 to the 993 and to drive the 993 like a 993 not an RX-7.  That's when the tire wear issues started to crop up. 

The issues being discussed make sense when you look at the design of the 993 rear suspension.  It's complicated and I can understand that some undesirable characteristics could arise when compliant rubber bushings are combined wiith the high stresses placed on them at the track.  There must be a huge number of variables in play here.  I suspect the age & condition of the bushings have to be a factor as well as the underlying design. I also expect the style of the driver comes into play as well.  These variables probably explain why folks have issues and some do not.

Personally, I wouldn't be too stressed out about it.  Remember, these folks are talking about cars that have been significantly lowered.  But, if you are worried about it, the ERP camber links are a great way to go and are a sound investment.

Take care,
Jack

BTW - don't sell yourself short.  I was potentially the worlds worst novice student.  Seat time does wonderful things

[Tony356993]

Although I will never drive the way you do

Larry,

You are getting better each and every time on the track. You are enthusiastic, not afraid to ask questions and take instruction well. As Jack stated, seat time can cure a bunch of ills.

BTW - I never had any issues like you described. I have the PSS-9 setup now but I did run a season (though not all that fast) with the stock setup.

 

[bobt993]

Jack,  I have been speaking with Joel Rieser on related issues and have confirmed some early 993's have an "evil" stability issue.  It seems to stem from bushing tolerances and produces "snap steering" in hard cornering.  Car can go from under to over steer in a brief moment.   Porsche addressed this somewhat cryptically with some control arem upgrades.  See tech articles covered by Joel on this.  He feels strongly that a tracked 95 993 should be checked for the upgrades and implemented if not already done. 

[jakp993]

bobt993 wrote:

Jack, I have been speaking with Joel Rieser on related issues and have confirmed some early 993's have an "evil" stability issue. It seems to stem from bushing tolerances and produces "snap steering" in hard cornering. Car can go from under to over steer in a brief moment. Porsche addressed this somewhat cryptically with some control arem upgrades. See tech articles covered by Joel on this. He feels strongly that a tracked 95 993 should be checked for the upgrades and implemented if not already done.

Like I said, Joel is an expert, I'm not. All I can say is that my car was never "evil".

Bob, can't remember, is you car an early '95?

cya,
Jack

[bobt993]

It's a 96

 Jack, ironically I was interested in the 96 due to the 18inch/suspension upgrade and Varioram (which when working is great).  I am one day away from completing the moton,bump steer,front monoball installation.  I need to remind myself of the horror next time I want to do this.hock:  but it's near completion. 

[smankow]

just in time for VIR  

sounds like perfect timing

 

Steve