How is your 911 Track Car Setup??

[Devil Dog Mosport]

Hi All,
Just looking to do some comparisons and resolve some of my issues. (This does not include the "driver"), that's much harder to solve.

Anyway, I have an 84 911 Carerra 3.2L with the following suspension set up:

1. Front - 23mm TB's , ER polybronze , Bilsteins valved 23m , stock points, 19mm Targett Swaybar set mild, ER decambered ball joints, monoball strut brace, with -2.1 neg camber

• Rear - 33mm TB's ER polybronze bushings, Adjustable springplate, Bilsteins valved 33mm, stock points, 21mm Sway bar, with -2.0 neg camber
• Brakes - Stock Carerra calipers, stoptech rotors, pagid pads (orange/black)

• Tires - Front 225/50/16 Rear 245/45/16 BFG R1s

My issue is this on the track.. coming hot into entries of turns,, braking hard, the car seems to be unstable and easy loses the rear-end.. hence as typical , rear end wants to be up front!!
Question - could my suspension be too stiff, brakes uneven, tires too small, pads to aggressive??? Driver needs work?

Enquiring Minds

[wildcat077]

You could easily upgrade to 17 inch wheels with 225/45/17 and 255/40/17 tires,the choice is really good ... Dunlop Dirrezzas,Bridgestone RE11's and perhaps loosen up the rear swaybars to dial out oversteer.I would think you have too much of some stuff and not enough of other things like brake pads and rubber ... then again driver could use some work as well

More rubber contact is always good !

Cheers
Phil

[winders]

There is only one rear sway bar and it sounds like it might be a non-adjustable Factory unit. Are you sure the loose under braking issue is a chassis balance problem?

[Devil Dog Mosport]

No the rear sway bar is also a Targett Adjustable set about midway.. I don't usually have "any" understeer issues, but way too much oversteer.. Like I said, the asse breaks loose too often...

I need more rubber contact (as wildcat mentioned) or is the car (front / rear) too stiff?

[winders]

So you have a 22mm rear Tarrett bar? How does the car feel in the corners? Does it understeer or oversteer in high speed corners? Low speed corners? Is the car stable while threshold braking in a straight line?

Did you change the ride height of the car? Do you have an LSD?

Are you sure you are not just overdoing the trail braking?

[Devil Dog Mosport]

Yes, the rear is a 22mm Tarrett Bar. The car feels relatively stable in the corners. I can get good speed in high speed corners and low, yet I wish I had more "rubber" contact for enhanced grip. Why i mentioned would 17" smaller sidewalls wider rubber help me. Would hoosiers be more sticky than the BFG's... I've got some restrictions with NASA TT on width, before too many points.. GTS is not a problem..

Like any (rear engine) I most often feel or know when she's going to break.. most times I can catch it.. sometimes I don't.

The car is lowered at race heights and corner balanced. I do not have LSD.

It feels more stable in trail breaking... It's when I want to come in hot, get on the brakes firm "even" in a straight line she want to some out sideways...
s

[winders]

Well, if the car gets real loose under hard braking in a straight line, it could be any of a number of issues. The toe could be off...too much toe out front or not enough toe in at the rear. The alignment could be way off. The corner balance could be way off. You could have too much brake bias to the rear.

Something has to be off for the car to want to go sideways when braking in a straight line. After all, inertia dictates that at object will continue to travel straight unless acted upon by some other force.

[Devil Dog Mosport]

I hear ya! So, now that our season is over here in the NE... Going through all the "basics" again... Alignment, corner balance, brakes.

Believe I will also move up to 17" wheels, going wider rubber front and back.. Soften the suspension and start fresh.. Next season, refine one thing at a time to see the changes..

thanks for feedback

[racer]

I've not run pagids before.. is there a reason for running two different compounds front/rear? Maybe that is contributing to balance issues, especially if trailbraking?

[juanbenae]

Originally Posted by winders

Do you have an LSD?

Are you sure you are not just overdoing the trail braking?

paging doctor monson, paging doc matt of guard transmission........... what ive left from scott's quote are very relative to one another.... with an limited slip rear end you can over do the braking now and again and not pay a huge price.

when I try to explain driving 911 to the lay person I suggest they throw a dart backwards..

[KTL]

My first observation was the 23/33 combo. That's a bit stiff in the rear. A more common setup is 23/30 or 23/31

If it wants to swap ends braking in a straight line, it sounds like too much rear brake. But not so much rear brake that you are locking up the rears? You say you've got Carrera calipers all around. Do you still have the rear pressure reduction valve in place? If not, the Carrera calipers have a hyd. bias that's pretty aggressive at 1.3-something (going by memory here) which is pretty aggressive, especially if you don't have a limited slip to help stabilize the car under braking.

I just don't like the Carrera brake balance even when the pressure limiting valve is in place because it doesn't produce good feel. I've fiddled with the brake balance by swapping some different front brakes and I noticed a huge difference when going slightly larger in the front (VCI front Brembo kit with basic small 4 piston caliper and 299x28mm rotors) and removing the pressure reduction valve.

I don't think the 17s are a must. 225 and 245 is a pretty decent combo for a Carrera and as long as you've got good wheel widths (8 in front, 9 in rear would be ideal) you should have a well balanced car with a good grip threshold.

I had my '87 Carrera tuned sort of similar to yours.

23/31 torsions

TRG (Tarett rip-off copy) adjustable rear bar set around mid stiff, fixed stock front sway bar

Koni single adjustable shocks set almost fully firm (rebound)

Small Brembo brakes

16x8/9 BBS RS with 14mm rear spacers added and 225/50, 245/45 Victoracers

No limited slip

Corner weights with equal cross weighting

Not super light weight- around 2650 with me in the car

Aggressive/track-oriented alignment but not crazy. A teensy bit of toe out in the front, decent negative front camber, plenty of rear neg camber (I notice you have less in the rear compared to front- I would try for more rear on your car) plenty of rear toe-in

https://www.youtube.com/watch?v=--Br8BWBTmE

That footage isn't to show how fast I was. 1:22 is a decent lap. But not earth shattering. Heck, I go 4 seconds faster in my racecar. But I think it's a decent example of a mildly modified car getting around there fairly quickly with good balance.

Note the ride height of my car. Not real low. If you don't have the proper geometry up front, that very low ride height can induce a lot of bump steer- toe change due to suspension travel. The buttmunch chasing me in the silver 911 would constantly poke fun at me about my "Ranchero" ride height. Ha ha. Who's laughing when he's sawing at the wheel like a maniac in his very low "stock" car trying to catch me while I just steer like a normal person.


I think you are OK with the BFG R1. They are very comparable to the Hoosier R6. Also, if your car is light, you can easily get away with using the BFG R1-S. I ran the S in hellacious heat 40 min race on my '79 racecar and they did not "go-off" on me. I was shocked to say the least.

[Mahler9th]

Of course it makes sense to go over the car and make sure everything is working properly. And to make sure that alignment, corner balance and ride height/rake are what you intend.

I'd say the next step is to take a deep breath. Don't spend a dime or any time potentially chasing your tail without....

a benchmark.

At least one.

Your tracks, your car with the same or similar modifications and set up. Often this is possible via the PCA. If you do AX or track driving and can have an instructor that can act as a benchmark with his/her car, great. Or an instructor that has experience with your car and its mods and set up.

It may be getting harder to do nowadays with the air-cooled cars being so old, but it is achievable.

Also try to reference old materials like tech articles from issues from Excellence and Pano where they discuss and describe identical or similar recipes.

Be wary of advice from vendors that may make and sell worthwhile products but do not have a lot of experience with DE and/or racing. The old gang at SRP and folks like Cary Eisenlohr and Karl Poetl have been there and done that. However some popular vendors don't have any deep knowledge or experience with DE and/or racing.

To me, spending money and time to make more changes may not be the best course. Knowing what you have compared to some benchmark may be most gratifying.

I have been at this DE/racing Porsche thing for over 25 years and I have chased my own tail a time or two. No fun.

Places like these forums can be great, but in my experience nothing beats an appropriate benchmark.

[Devil Dog Mosport]

Originally Posted by KTL

My first observation was the 23/33 combo. That's a bit stiff in the rear. A more common setup is 23/30 or 23/31

If it wants to swap ends braking in a straight line, it sounds like too much rear brake. But not so much rear brake that you are locking up the rears? You say you've got Carrera calipers all around. Do you still have the rear pressure reduction valve in place? If not, the Carrera calipers have a hyd. bias that's pretty aggressive at 1.3-something (going by memory here) which is pretty aggressive, especially if you don't have a limited slip to help stabilize the car under braking..

Yes sir, I still have the standard Carrera calipers and PDV in place, nothing adjusted. For what's its worth.. I noticed the Hawk DC pads , whilst less grippy than the pagids and more mushy...tend to give me at least better control.. The pagids grip and hold on..

I like your thoughts about the stiffness.. this was my initial thought about the ass-end being too rigid and easy to rock around.. The tires have given good grip when I've dialed in the right temps/pressures...

Most everything else you've got and said, I have covered off on.. I would like to go up to 17s still I think, if nothing else to get a smaller side-wall and prevent any tire roll I might get there..

Great Feedback.. thank you!

[Devil Dog Mosport]

Originally Posted by racer

I've not run pagids before.. is there a reason for running two different compounds front/rear? Maybe that is contributing to balance issues, especially if trailbraking?

Recommended in this configuration by Pagid for this application. As do most Brake Pad companies..

Remember the majority of braking is done "up front" , hence the different compounds have different characteristics to give you better balance and more even braking.

[Devil Dog Mosport]

Originally Posted by Mahler9th

Of course it makes sense to go over the car and make sure everything is working properly. And to make sure that alignment, corner balance and ride height/rake are what you intend.

I'd say the next step is to take a deep breath. Don't spend a dime or any time potentially chasing your tail without....

a benchmark.

At least one.

Your tracks, your car with the same or similar modifications and set up. Often this is possible via the PCA. If you do AX or track driving and can have an instructor that can act as a benchmark with his/her car, great. Or an instructor that has experience with your car and its mods and set up.

It may be getting harder to do nowadays with the air-cooled cars being so old, but it is achievable.

Also try to reference old materials like tech articles from issues from Excellence and Pano where they discuss and describe identical or similar recipes.

Be wary of advice from vendors that may make and sell worthwhile products but do not have a lot of experience with DE and/or racing. The old gang at SRP and folks like Cary Eisenlohr and Karl Poetl have been there and done that. However some popular vendors don't have any deep knowledge or experience with DE and/or racing.

To me, spending money and time to make more changes may not be the best course. Knowing what you have compared to some benchmark may be most gratifying.

I have been at this DE/racing Porsche thing for over 25 years and I have chased my own tail a time or two. No fun.

Places like these forums can be great, but in my experience nothing beats an appropriate benchmark.

Agreed and a logical approach!

[Devil Dog Mosport]

Originally Posted by car 311

paging doctor monson, paging doc matt of guard transmission........... what ive left from scott's quote are very relative to one another.... with an limited slip rear end you can over do the braking now and again and not pay a huge price.

when I try to explain driving 911 to the lay person I suggest they throw a dart backwards..

Perfect !!

[Plavan]

I'm using 22/31 on my torsion bars. Works great. Front sway bar 1/4" from Full Still, Rear bar- Full Soft. I would think about replacing the Polybronze at some point down the road- You will understand when you remove them and look at them. As for Pads, Raybestos compound ST43 hands down.

Most of all- just get seat time.


Oh yeah- Get a Guard LSD too!

[Devil Dog Mosport]

Originally Posted by Plavan

I'm using 22/31 on my torsion bars. Works great. Front sway bar 1/4" from Full Still, Rear bar- Full Soft. I would think about replacing the Polybronze at some point down the road- You will understand when you remove them and look at them. As for Pads, Raybestos compound ST43 hands down.

Most of all- just get seat time.


Oh yeah- Get a Guard LSD too!

Checked your "smurf" mobile...nice! I forgot some stats also... 3.2L , 205 RWHP @ 2758 with driver (245lbs) I run NASA TT and GTS and would actually like to have SWong chip it for less HP.. Right now at the bottom of the class and those darn M3's kick my butt...

Agree on the TB's, think it's too stiff and can soften that up for sure.. Less TB in the rear and adjust sway bars... Also think I will stay with the 16" wheels after all.. Not enough HP to turn too much rubber anyway..

Still like to widen out the rear however , so what about "spacers".. I bet I could go as much as 30-45mm and still stay in the fender well... Anyone using these?

As before mentioned. think the setup could use some work too.. I'd like to get more negative camber but limited by my ER de-cambered top plates now.. Have to talk to Chuck about that.. Also not sure if I have the suggested "toe out" set either.. Back to the rack !!

Agree on the LSD also.. think this certainly would be the single biggest change/investment..

Thanks

[wildcat077]

I have -2.8 front camber with Tarett camber plates and ER decambered ball joints ... still trying for -3.0 but it's difficult ... and -2.6 in the rear with ER Cambermax adjusters,looking to get more rear camber somehow !

Cheers
Phil

[Mehoff]

Originally Posted by KTL

My first observation was the 23/33 combo. That's a bit stiff in the rear. A more common setup is 23/30 or 23/31

.

Curious on the thought process for this. The POC "E" equivalent cars are running 23/33tb's with 31/27 smart sways and these cars are rocket ships. My car is dead neutral and I can easily input oversteer/understeer by moving the sways.

I think OP's issue is a missed suspension set up (and no LSD).