VetteDrmr

With all the talk about single and double adjustable shocks, like many things, I begin to wonder if they would help me in my autocross events?

Well, the obvious answer is "Duh, of course!" But that assumes I know *how* to adjust them; something I've never seen discussed anywhere, in print, on the web, etc.

Chris Ingle, and many others, makes a great point about not modding the car while learning how to drive. I've been doing this for about 5 years now (feels like I'm still a newbie), and I'm just beginning to think about mods.

Anyway, last year I upgraded from Z51 to '04 Z06 shocks, and while the car seemed to handle a bounce better, I'd be hard pressed to tell you what made the difference. Better shock design or just less worn out shocks?

So, how do you learn? Surely there's got to be something better than just trial and error. If that's the case, I'm just going to stick with either the '04 Z06 or Bilstein Sport shocks and lessen the number of variables by about 16 (figuring that's how many ways I could screw up a shock adjustment).

TIA, and have a good one,
Mike

acrace

http://www.bimmerhaus.com/tech/shocktuningTN.html

http://www.farnorthracing.com/
Go to the "Tech" link and then to the "Autocross to Win" link.

http://www.grassrootsmotorsports.com/
Go to the archives link and look up "Shocking Behavior" for their shock article.

Challenge for autocrossers is getting enough test and tune time to learn what works best, and then having to know the car well enough so that when you go to a new place/new surface you can adapt quickly.

davidfarmer

All you can do, as a driver with limited test time, is set everything in the middle. THEN, adjust one end of the car as need. IE, soften the loose end, or tighten the end that has grip.

If you have 2 or 3- way shocks, it is a little more complicated. In other words, if your rear tires come loose under braking, that would be a rebound adjustment. If they are causing problems (again in the rear) under accel, it would be compression.

If you have 3-ways, then you have a high-speed and low speed adjustment. Basically, high speed affects how the car acts over bumps in the road, and low-speed affects how the suspension works in the corners. Bumps are instantanious changes in the travel, while rolling into a corner (or brakeing) moves the shock relatively slowly.

I have some other decent setup guides I'll dig up for you.

For Auto-x, I'd get a simple, 1-way shock. Just being able to make minor stifness adjustments can help a lot. As you've been instructed before, too many adjustments is a recipe for disaster.

XPC5R

Carroll Smith's Tune to Win book (and the Engineer in a pocket) Have great cause and effect lists of what chassis changes can influence.

Having rebound adjustability is a very useful tool, with something like the Koni or Penske single adjustable shocks being a very good bang for the buck. The shock valving really influences corner entry and transitions (slaloms, offsets). Once you reach mid corner and beyond, you are relying more on the basic spring and bar balance.

Changes are primarily reducing damping on the end of the car that is not gripping, stiffening damping on the end that is too planted. Occasionaly a specific race surface or tire will demand a different approach, but that is the basic method.

Testing just narrows down how much adjustment you need to dial in for the effect you want.

PS: One plus for the 2-3way adjustable shocks, they often, by design, have better (stronger) low speed damping, and more track oriented rates, which really improves the feel and response of the car in general.

yellow01

if there are 10 settings, 9 of 'em are wrong.

Disclaimer is the stock setting maybe way off too.

Good luck with it!

VetteDrmr

Yeah, that's the problem. I don't know if I can handle even one!

Thanks for all the references; now I've got some reading to do.

Thanks again, and have a good one,
Mike

davidfarmer

attached is a jpg of Page 17 of Penskes shock manual, giving a basic explaination of damper control, and more importantly, explains how to find a starting point.

I'm pretty sure you can download the entire manual from Penskes website, but I have it on pdf if anybody needs it

VetteDrmr

David,

Thanks for that page; it at least gave me a footing. I'll search Penske's site this weekend and I'll let you know if I run into any problems.

Have a good one,
Mike

7Bob3

George Lynch who has done the set-ups for his wife JoAnn's 11 national championships told me once the 04 shocks are 95+% 100% of the time. Adjustables are 100% 50% of the time until you have a bunch of experiance. Grip and temperature changes will require adjustments. If you PAX within 3/10s of Popp, Thomason, Berry, Isley or in your neck of the woods XPC5R or Strelniks on a 60 second course you may be ready for them. If not you can buy alot of tires for the price of Penskes or 2812s.

davidfarmer

Penske's site seems to be in construction, but unless you are rebuilding your own shocks, the page above is the only one you need.

Here is Koni's version of the same thing

http://www.koniracing.com/roadsetup.html

The T1 Sachs/04' Z06 are great shocks, but they don't last long under heavy use. I got less than one good season (20hrs) out of them before I could manually squish them up and down by hand.

Fortunately, they are cheap.

redvetracr

I think the term is "testing", lots and lots of testing.....the reason I use NON adjustable shocks...as well as non adjustable everything else.....
...redvetracr

John Shiels

THat is what I try to tell people stock shocks are nothing but a low bid contract to get you off the lot. I remember not to many years back the OEM were paying like 9 bucks for a car shock.

ghoffman

A few random thoughts on this. First of all, I was able to get a set of used Penske 8100 (supposedly originally from a Major Corvette tuner) for my C6Z for about a grand (all 4) off of this forum. They needed seals and the valving was way off. How did I know that? I went to depressurize the canister by depressing the schrader valve, and oil came out so for sure the canister piston seal was bad. I went over to Richard Strout's shop (www.lemd.com) he called Penske, and a rebuild kit showed up the next day (sorry David, my Penske service experience has been great). Then I discovered that the valving was not correct, another call to Penske and more parts show up in a day or 2. The way you tell that is to look in the Penske service manual and count washers and shims. The RF was different from the LF, and very weird anyway with no compression and huge rebound (A-, D+) In Penske speak, "A" is the minimum damping, "B" is more etc so you should see a sticker on the shock that says something like B-, C+. That means that the basic compression is B- and the rebound is C+. Richard has many years of experience with shocks of all brands so he suggested a setup. We refilled them with synthetic Royal Purple shock oil. I have Penske 8100's on my race car as well so I was familiar with these but having them on my street Vette has allowed me to play with them alot. I run them at one flat tighter (from the middle) on the rebound and full soft compression with 150 psi on the street. When I am going to the track I go to 250 PSI, compression on 3 or 4 to take out some of the bone crusher transitions in turns 3 and 10. Our tracks in the NE are rough because of the winter and NHIS has some rough transitions so what works one place is not what works somewhere else where the track is much more like a billiard table. It works pretty well, but I think that the piston should be changed (really easy to do on a Penske) to blow off at higher shaft speeds like braking on ripple bumps.
To answer the question that started the thread, I would recommend that you get them setup from someone who knows what they are doing and then it is all about seat time and testing. You go try it, change something and measure the change. That is why having the adjusters easy to get to is essential because if it a PITA, you wont bother. For me I open the hood and turn the ****. I bought these really cool canister mounts from Joe's Racing products. After all of the work, I have a first class setup for reasonable cost. Don't be afraid of getting used Penskes, the parts are very easy to get and doing your own rebuilds is very easy. I used to do this all the time on my bikes with Fox and Ohlins shocks so I found it pretty easy. I have only 4 special tools, a N2 tank with regulator (good for the tires too), a fill tool, a spanner wrench from Joe's as well and a vise.