Matt, Did you do any special break-in for the Rivals? On tire tests they seem to be the best alternative to DOT tires. Dwight Mitchell recommends eliminating and checking for any sway bar binding...he also has 10 other recommendations I should send you...I can't remember them now.

Is Dwight still around? I remember autocrossing with him in the early '90's. I beat him in his ASP 911 a few times with my '78 Targa. Fun times!

Also, consider Jae Lee here in San Diego ( he Builds the 3.8s for Singer) as he is a suspension guru, and Bilstein is located here.


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This Dwight Mitchell?
http://lh3.ggpht.com/-xq16tv61Mz8/Sq...4/DSC_5073.jpg

I was told to seek him out waaaay back when I started my project.

As far as the Rivals, no special break in. Bolted them on, drove a few hundred miles, ran them, then drove back. The small diameter kind of sucks on the freeway so I bring them separate now if I'm going to try them at an event.

I had HUGE swaybar bind that I found and eliminated. I wonder what those other tips are...

Lots of chatter in this thread, some useful and some not so much. That said, I use this sheet plenty and I'm surprised it hasn't been shared in the thread yet.

http://forums.pelicanparts.com/uploa...1438701062.jpg

I've seen that chart several times and it's pretty helpful. My car oversteers sometimes, understeers sometimes, and others is perfectly neutral. I would say that statement is true for almost every fast race car ever.

The next derivative in the equation is in phases of the corner.

- Corner entry is very dependent on the front end of the car. I run a touch of toe out up front to build slip angle in the tires to speed turn in. I run a large front bar to transfer weight quickly.
- Mid corner is spring rates and alignment. My car leans a fair amount, so I run big camber. The TBs and bars work together to create a certain balance of loads on the tires for a certain grip balance.
- Corner exit transfers some focus to the rear. I have a touch of rear toe in for stability in power down and to keep it from being too "snappy" should I overwhelm the rears.

Then the next derivative beyond that is transition.

An AX car spends a HUGE amount of time in transition. A car on a race track sees transition as well, but the percentage of time in transition is much lower. This is where my car needs help. It's control of the rate of weight transfer. A good example of where this is supremely important in AX is a slalom:

http://www.sccawiregrass.org/images/slalom.JPG

An AX car never reaches steady state in a slalom, it's constantly transferring loads from the left tires to the right and back again. This is where shocks (dampers) become extremely important. They can control the speed at which those loads move from one of those little tire patches to another. Compared the the STR cars I've driven, my car is as lethargic as molasses. So much lag time between input and reaction. The ways to speed that is by either more spring rate, more bar, more compression damping, or a combination of those.

What's worse, there's virtually no free lunch. Every change has both an upside and a potential downside. There's no perfect car, there's no perfect setup. And everything changes with every surface, every course, even the weather. Oh, and every driver is different - driver A may be faster with a loose car, where driver B may be faster in a tight car.

Like Captain Ahab, we're all chasing a white whale that is both a curse and an adventure.

Still love this thread, and thank you Matt for maintaining it and being so open to discussion.

Just did my 4th event ever (all 4 in the 911), and finally put down times that were encouraging. Just ordered 225/45/16 Z2 Star Specs for my 7s and 8s (the cheapest option for me right now) to see if I can get anywhere in CS. Strong likelihood I will join you in STR sooner than later because I want to add STR bits to the car in general (Recaros, SW chip, etc).

This is why having at least one adjustable sway bar is really important. When I autocrossed, I was adjusting a sway bar at just about every event. No two courses were the same and the car needed to be adjusted so it did not have too little or too much oversteer.

!!!

Awesome!

Not that I've thought about it, but if I were to play by C Street rules I would get really creative with the bumpstop rules the way they are written and factory ride height adjustment...

I am operating at a lower level (CS for SCCA and Production for PCA) but working on making my car and myself better at A/X. The latest improvement I made was to install Koni Sport (Yellow) shocks with external adjusters. I am running stock TBs (18 and 25 mm), stock sways and have a strut brace. Front toe is zero, front camber is -1.4, rear toe is +.30, rear camber is -2.0 and caster is +5.8. I have run BFG Rivals 225/45-15 on 7&8x15 Fuchs and I have Hankook R-S3v2 225/45-17 and 255/40-17 on 7&9x17 Euromeisters. Tires make a huge difference, alignment makes a huge difference.

Better shocks make at least as much of a difference in raw times. At the last PCA A/X I was struggling to run decent times. Suddenly I remembered that I had forgotten to readjust the shocks from full soft (for driving on the street). I cranked the front and back shocks to full stiff and dropped 2+ from a 60 sec run. The difference was CLEARLY in transition. The car changed direction right now instead of leaning, grabbing and then changing direction. I need to add an item to my A/X prep list. Check the shock adjustment.

Better dampers help a stock setup but they can only do so much and are not better than changing the spring rates and sway bars to something more appropriate.

As far as alignment goes, I want a little bit of toe out at the front and a little bit of toe in at the rear. Camber settings all depend on the tire being used.

=================
I'm sure you are right. I plan to upgrade the t-bars and add an adjustable rear sway bar for next season. Those are things I can do and not move to a tougher class like STR or Improved. I will install better bushings when I replace the t-bars.

I don't think TB changes (or bushings for that matter) are allowed in Street? Just one swaybar.

I've read the rules many a time, but not sure what you're referring to about bumpstops. I definitely take advantage of ride height adjustment, a nice advantage we have over cars w/ coil springs.

If I understand it right, the digressive valving gets you a good tradeoff. AX lots are often much less smooth than race tracks, so stiffer springs aren't always the answer. Big low speed compression with a heavy digressive cut nets you a boost in spring rate when you want it, while allowing you to retain a softer spring for bump compliance when you don't.

I guess the super pimp top of the line race car tech these days is regressive valving:
http://qrgarage.ca/wp-content/upload...ivepiston2.jpg

Tremendous low speed control that somehow softens at high velocities. Idea is race drivers can just blast curbing and the suspension frees up enough to soak it up. No idea what kind of piston witchcraft they do to pull that off.

Wow that is cool, I wonder when the Regressive will filter down to mortals? I wonder if it would even be pleasant in a street/DE car? seems like it would.

Speaking of Witchcraft recently Ford released some track videos of the forthcoming Mustang GT 350 R (I think thats what its called). I believe thats a 3600 pound car with the new flat plane crank V8. Anyway, it has the magnetic particle shocks, the flat cornering and ability to absorb bumps by that thing is amazing. They show it coming over a big hump in the track and it just eats it up and takes an set in the next corner at huge speed - no drama. Really amazing. Worth a look.

I had adjustable bars on both the front and rear when I ran my 911 seriously. The goal was to just slightly lift the inside wheel. Maybe an inch at some point in the turn. I usually adjusted one bar or the other after each run. Today with data acquisition this should be a walk in the park.

I'm reminded that marque folks have alway had a really rough time in SCCA Solo competition. The fast guys just buy whatever is the fastest car in the class. They set it up the same way the fastest guy in the class sets his up. They win a lot.

People with marque loyalty spend a ton of money and never win. They do though have a lot of fun. That might be the real point.

Richard Newton
My 911 in Action

Looks like Penske sells a regressive piston for consumers now:
Penske Shocks / Accessories / ASSM, REGRESSIVE VALVE COMPRESSION
Not clear if that's one or a pair, but $500 on top of a $2000 per corner shock, before tuning, is pretty big money.

MR is nuts. I guess when you turn on an electromagnet it changes the effective viscosity of the oil. So in theory you can have whatever damping you want at any time. As that tech develops further, sensors get more accurate, processing power gets faster, and algorithms get better, that'll be pretty gnarly.

I run a Flowmaster spun cat. Light, high flow, meets the rules.

http://2.bp.blogspot.com/-CMxceo-kq3.../642-54959.jpg

The MR dampers react so fast that they change the damping dependent on suspension travel, not just the speed. I think it was one of the new GM cars that I read can adjust the damping every inch of travel for a bump at 60 mph.

FYI, the pic posted earlier is not normal cornering attitude for my car, just a well timed shot from a talented photographer. Here's immediately before and after. Either a bump or in transition it goes all awesome.

https://lh3.googleusercontent.com/-U...eels%2Bbro.jpg