stownsen914

In his book Drive to Win or Tune to Win, Carroll Smith describes the procedure that he used for setting up his race cars. I am not sure if that information is dated now ...

Scott

beentherebaby

OP-

As you can see there are many perspectives on this subject... and it's a complicated and comprehensive subject as a change in one area effects several others. If you haven't read the basics of chassis engineering Herb Adam's or similar books is a requirement IMO. If you do know the basics then you need to work methodically with one end of the vehicle at a time and record changes and effects.

It's a lengthy process to properly dial in spring rates, damper rates, damper settings, anti-roll bars, (ARBs), tire pressures, etc. Some of these settings are based on driver preference, car model, track layout, etc. There is no perfect set-up, only a best set-up for the situation - which changes all the time.

In regards to your original question bumpy tracks won't tolerate excessive spring rates or damping forces as the tires will skip across the uneven surface. Engineering is the art of compromise. Finding the best balance for any car is part science and part art or SWAG. Testing is the only means to be sure what effect the change actually made.

Jan Zuijdijk's Vehicle Dynamics and Damping book is good if you can understand the language translation issues and you have an excellent technical understanding of vehicle dynamics/physics to begin with.

outline

perhaps the subjective nature of the term "very high spring rates" is where the disagreement is there also.
if you are running serious large spring rates then i very much see that these could indeed override the inputs from the other components itself and jans statement would hold.
perhaps what larry views as being high spring rates from porsche, jan would consider still soft in relation to his statement about too much spring eventually becoming counterproductive and theres actually no deviation at all in theory.
just a thought.

my 996 cups also had a secondary linear soft spring (70N/mm and 60N/mm) that wasnt quite fully compressed under static load. this allows a touch of compliance in the suspension before the hard springs come into play. i copied this over onto my road car and have something very tolerable indeed.

bobt993

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Neil, that is exactly how the stiff spring setup works best. Secondary springs tune with the shocks for proper travel on a track surface. I take more and more curbing everytime I hit the track now even with very stiff main springs. Now once you use up the .5 inches of compression............ you better have had your caffeine shot to make a wheel adjustment.

Larry Herman

That is exactly right. It is something that one needs to grow into as their skills hopefully get to that level.

Brinkley

Thank you all for your input on this topic. I am reading as much as you guys can refer me in an attempt to build a foundation of knowledge.

I do have a question that is confusing, some have said shock adjustment is like sway bar adjustment, softer bar gives you better grip while stiffer bar gives you less grip. Is the adjustment of shock bump the same? Stiffer shocks give less grip while softer bump settings give higher grip. Is this right or am I off track?

I've read about the diagonal understanding of shock settings/adjusting and that; adjusting for one turn might negatively affect another turn.

Clearly there is a lot more for me to read, understand and then put into practice. Thanks again to all and please keep the info coming.

Jimbo951

Very simple answer:

Stiffer bump produces less grip when the shock is compressing, i.e. weight is transfering to that corner.

Stiffer rebound producess less grip with the shock is extending, i.e. weight is transfering away from that corner.

Stiffer swaybar produces less grip at that end (front or rear) when the car has body roll.

Veloce Raptor

None of this is always true. You will find that sometimes stiffer bump works better on smoother track--more grip while allowing more use of curbs--while softer bump works better on bumpier and/or off camber track. Also, sometimes a stiffer chassis (for example, adding a cage to an uncaged car) works better with more rebound than prior to the stiffening. In general, you want to try the least bump you can get away with and the most rebound you can get away with, and see how that works.








Professional Racing and Driving Coach

Larry Herman

Wow, there is a lot of conflicting information here. I won't even try to sort it out.

Brinkley, my best advice for you is to find someone that you know who drives very well, knows why they are fast, and knows why their car works so well, and learn from them. My knowledge took a quantum leap when I did that.

One other thing to keep in mind about advice is that there are different driving styles, and someone who actively throws a car into the corner will want a different setup than one who rolls it in.

fatbillybob

Larry,

Are shocks matched to springs? So if this developing driver uses a significantly softer spring to start does he also need a new set of shocks to go with the later stiff springs he grows into? It seems that the Art gets really black when there are thosands of different valvings that can be had in any set of penskes, motons etc...

Larry Herman

My experience is limited to Motons, but I would think that most other remote reservoir shocks will have enough adjustability to handle a fairly wide range of springs. IIRC the Moton Club Sport shocks can accommodate springs from 400 lbs to 1200 lbs, so it is easy to start soft and then step up the spring rates as desired. Of course, it is always best to check with the mfg to know exactly what spring ranges their shocks are designed for.

BGB Motorsports

Gents,

There are way too many variables with all of these cars to have a secret recipe for success. Spring rates can be dicated by car's mass, tires and drive comfort and no 3 variables net the same set in stone setup. I can't stress enough that one setup just won't work for everyone.

Put in it's most simple form, high speed adjustments on Moton and JRZ triples are used to tune your car over the bumps and once in the window, need to be adjusted for spring changes and bar changes, with a click here and there. After that, unless you're going from Sebring to Miller Motorsports Park, bumpy surface to a pool table surface, you don't have to change the high speed adjustments that often.

As far as rates go, if you have a shock valved for an 800 lb. spring and you put a 1400 lb. spring on there, the shock will need to be either adjusted or re-valved if you don't have enough adjustment. An undervalved shock will yield no feeling of adjustments. If it can't slowly release the spring once it absorbs its energy, you'll have to re-valve or turn ***** a lot to feel anything.

Most simply put, if you have triples with remote reservoirs you can either increase/decrease the can pressure of the nitrogen to produce a SIMULATED feel in spring rate change. Other than that, the low-speed bump control is an ubelievable tool for inducing a tigther or looser feeling for the car, once you're in the window you should be able to achieve great strides by changing sway bars and low-speed clicks to improve the balance.

I can't tell you enough, there just aren't any set spring rates for these cars. We've run rates all over the place with dozens of different pro drivers and those guys have trouble telling what feels better or doesn't. You'd be amazed how little people understand about this stuff and how much drivers/engineers regurgitate the wrong information.

If it feels good, and the tires don't burn off in 20 minutes then let it rip, other than that, don't listen to anyone else unless you absolutely hate driving your own car and have moved every ****, rate, angle, or adjustment from lock to lock!

Gary R.

I'm going with that tidbit, thanks John!

mark kibort

I know , huh!!

mark kibort

Yep, quite simply, you set the bump so your teeth dont fall out and set the rebuound so that the car doesnt jack down.. this will change on every track and driver style, performance level of both the car or driver, and on an on. Then, start adding factors like high speed bump and you see, it becomes an art form, just as picking spring rates, swaybar settings, tire pressures, and many other factors.