Gentlemen,

I have been tracking (DE's) my -01 996TT for a long time. With miscellaneous other issues out of the way I am now focusing more on the suspension. What drives this, in addition to need for speed, is severe tire wear on the inside edges, especially in the rear. I run:
- PSS 10's lowered appr. 1 1/2"., Hoosier R7 315/30-18 and 275/35-18, pressures hot 38/33 (trying to keep them from wearing edges).
- Camber 2 1/2 deg. front and rear, Total toe 1.5mm front and 4.8mm rear.
- Stock sway bars and no limited slip. PSM shut totally off with switch.
- Most bushings are more rigid than stock by now.

I am looking for advice on setup with the primary intent of reducing tire wear. At Sebring I just ran a set of rears through the inside edges in 200 miles. Am I just simply running too much camber?

In addition to just alignment and soft rear sway bar I am concerned that the wheel spin on the inside rear coming out of corners contributes. Has anyone seen this as a cause for tire wear?

 

pwdrhound is the resident suspension/brake guru so reach out to him.

i will tell you the psm isnt shut off just by the switch. it still lurks in the bac kground. and also the pss10 is a decent street setup but if your going into track duty jrz or moton is were you need be. and a lsd is almost mandatory

 

need to dial back the toe and get monoball'd/solid at least in the LCA's....and get a LSD.

 

My current setup is very nice for a street/weekend warrior car besides my coilovers which I'm going to upgrade this year as well. This is what I run.
eibach adjustable sway bars with hd end links
solid adjustable thrust bushings
solid rear subframe bushings
95a poly pca bushing
95a poly toe arm bushing
lca and toe essentric locker plates (elephant racing)
torque solution dog box arms
torque solutions engine and transmission mounts
h&r street coilovers
wavetrac diff

outside the the h&r coilovers being to soft, the rest of the setup is supper tight and just complient enough for comfortable street use.

you want full track though monoball everything is the way to go.

 

Thanks 32krazy!, 993GT, and flewis763.

My front end is elephant racing so it is very adjustable, and I do fully shut off the PSM by switching off the power to the pump under the brake fluid container. I can't recall which and how stiff my bushings are as they have been replaced gradually.

It sounds on the above like sway bars and LSD are next.
Do I need to replace both front and rear sway bar, or is the rear enough?
Which LSD is recommended?
Can you pls provide recommendations for camber, and toe?

TIA,
Ola

 

I would be interested in seeing how you shut off the psm. Are you getting dash lites when you do?

 

I wouldn't say you need sway bars, but is a nice upgrade for adjustability/balance
LSD is must, GT2/3 stock with upgraded internals(P.M. or Guard), Porsche Motorsports unit, or Guard plate unit is the way to go IMHO
Alignment is something you will have to work on, everyone likes a different feel and parts are different...how is your rear tire wearing? even wear except for the inside edge or..?

 

To 32krazy!: I just put a switch on the power to the PSM pump. This is something I read about on this list. It also has the advantage of lowering the incidence of ABS shutdown which I commonly get when running over curbs under power requiring me to shut down and restart to get a reset. Very scary since braking is very limited when ABS shuts down. Yes, the PSM light stays on and is now taped over.
To 993GT: The rear tire wear is fairly even except the inside edge going very quickly. This is what causes me to theorize that the wear is caused by inside rear wheel spin. No pictures now since the car is 2,000 miles away.

 

if there is a taper to the wear, bring camber down a bit, if it is most noticeable on the inner inch or so of the tire then it is a toe issue....I would consider getting your rear LCA's monoball'd and solid/metal thrust bushed, this will control axle movement/toe-control...if you run with an open diff for the time being, I'd consider leaving toe higher to stabilize under braking...LSD, get the toe dialed back a bit.

 

Full lsd is a bit harsh for street duty. If its not a dedicated track car look at the wavetrac. Its a nice compromise from a full locker and only about half the cost

 

highly recommend front and rear adjustable sway bars with hd links. Gives you most most and fast way to make quick handling changes to the car depending on the needs at the track

 

I'll disagree with Steve/32 about Wavetrac for your usage...clutch/plate style LSD is what you want/need as they add a ton of stability and are 'consistent'/'constant' and except for some very small scrub when turning around in a tight driveway etc there's no drivability issues with them. While a Wavetrac has it's applications and will still be a solid improvement vs open diff, it is not a roadcourse/handling biased setup

 

ask ccjimmyb about his full guard unit. turning even the largest of curves he feels the unit locking. also its very expensive. its a great unit for racing but for the street its akin to running a sequential or dogbone trans. it can be done but its not very pleasant. the wavetrac is a very capable unit. may not be well known in the porsche world but vette and mustang racers know it well. unless its a full track car ill stand by my post its a very capable unit for double duty

 

what locking ratio/preload did he go with? IIRC, he was building a drag/mile car?
you want that locking preload for chassis stability...while the Torsen/Wavetrac/Quiafe/etc diff works well for Vette/Mustang/fwd/etc cars, the 911's typically do not want a 'free wheeling' diff, again for handling/track setup. Wavetrac would probably do well for autocross.
I'll leave it at that

 

i agree they are 2 different types of diffs. that being said there arent many street cars being sold with full lockers. even the gt3 is more geared towards track than street. the wavetrac also has a single feature that no other diff has. a LIFETIME warrenty. break it, send it back they fix it no questions. my buddy snapped a ring gear and destroyed the wavetrac with the shards. sent it back wavetrac rebuilt and shipped oit back no cost. wasnt even their issue. that is what sells me.

and yes jimmys car is a straight line car and the shop installed what i believe is a 80/20 guard unit. well built solid unit and he hates it ion the street.