y8s

iTrader: (8)

partly, but also to control the rate at which the wheels move relative to the chassis.

AD70

YES, I see we are finally agreeing , Y8S and philMD have nailed it with regards to using the dampers to fine tune and control the rest of the suspension, dampers are not a band aid to a badly tuned suspension system.
Bernie S has been trying to say that all along , but I think he was way ahead of the curve and the posts have started to catch up to him.

wannafbody

iTrader: (1)

I think Bernie and Phil are in agreement somewhat. I've never seen a shock dyno with 0 compression. NA HD's have 50#, IIRC R Pack is about 100# and LG Billie racing coilovers for the Vette have about 100# compression.

Does the weight of the wheel/tire play a role in determining the amount of compression and rebound needed or is it simply a function of the springrate?

greeenteeee

Is the ride frequency the same as bounce frequency?

I've been using this to determine FRC:
http://www.fatcatmotorsports.com/FRC...MSDS_1_6NA.htm

How much of a higher rear frequency should we be looking for, and how should ride frequency be chosen in general? (I can only assume by tire compound)

Great thread guys, I am just trying to absorb as much info as I can.

emilio700

iTrader: (3)

In a perfect world, the damping rates would only be addressing wheel rate, not unsprung mass. In the real world though that mass and it's inertia need to be dealt with. Additionally, damping and wheel rates have to be tuned taking into account the "spring rate" of everything else in the car. A the amateur level like us, we don;t do that. At the other end of the spectrum, F1 say they're not only tuning the spring rate and damping characteristics of the tire itself, but the entire monocoque structure. They'll actually model the damping characteristics of the engine and transmission along with the tub. FWIW, state of the art open wheel race cars have been running virtually infinite front roll stiffness for some time. The tire is the only means of body roll up front.

In a Miata, the tub is flexing quite a bit, even with a roll bar. How this other level of damping might apply would be in a national level CSP car which will sustain about 1.6g on a good concrete surface with 275 A6's. Thos care are stripped of all OEM bracing and run upwards of 900lb front springs and no rear sway bar. In that extreme case, the torsional stiffness or resonant frequency of the tub is exceptionally low (bad). It's winding up and unloading. The roll couple bias is obviously affected and one of the main reason they need such massive springs to keep the cars neutral. While no shock designer adds that into the mix while selecting valving, the racer will continue to tune the car and request this or that valving. Unknowingly compensating for the fact that the actual tub of the car twisting is probably some crazy 15% of the otherwise undamped wheel rate at 1.6g.

Bernie S.

I think we are all coming to terms here.

I have been trying to point out since the beginning that we are trying to understand proper damping before we worry about manipulation. When you start to tune the suspension using the shocks for purposes other than dampers, that is manipulation. This is where you apply compression damping, excessive rebound damping and all sorts of other stuff to "dial" in your car.

emilio700

iTrader: (3)

In stock class autocross this is how it's done. Unorthodox valving spec to manhandle a car to get it to turn with too soft springs, too high ride height, too narrow wheels, too little roll stiffness, too weak a differential etc. Did a lot of that in my ES/DS/CS days back in the early 90's. Deliberately pumping down shocks, exaggerated knee points on one end, weird stuff.

cueball1

iTrader: (13)

I gotta say this thread is why I love MT. Vendors at Mnet rarely have such reasonable and informed discussions without it devolving into bashing each other, trying to undermine another's thought process, knowledge and products.

While MT.net is known to be hard on newbs, intolerant of dorifto jdm yo boyz and coarse in general, here are two great resources playing nice in the same sandbox. Are we the only forum using Multi-Cat litter?

flier129

iTrader: (7)

So outside of miata world here.....

Let's say I run an ST integra with koni yellows and 400f , 450r gc's and the car comes completely unsettled going over the slightest bit of road change. With only have the adjustabilty of compression tuning, what do I do? Turn the comp. down or get different springrates or what?

Guess I'm looking for more of a quick fix I could do between autox runs.

Bernie S.

The quick fix would be trying to dial out the compression before replacing springs.

wannafbody

iTrader: (1)

I think there is a mistake here, Koni yellows only adjust rebound unless you have the DA's which have a seperate compression adjustment. I have Koni montubes on the rear of my TA. At the softesst setting they are like butter. The rear of the car just glides but that comes at a price-understeer and a floaty feeling at 65mph. I recently adjusted them up 1 click which is +20% on the rebound. The understeer and floaty feeling is gone but the seams in the road are more pronounced. The ride is firmer.

flier129

iTrader: (7)

Yeah your right, my mistake, rebound only.

So could I raise the hide height a tad and up the rebound? So then the energy would be released less violently?

PhilMD

Yes, they should be, but looking at the spreadsheet it looks like there's a calculation error; I've got under 1Hz for the stock spring rates....In general, look for a 7-10% increase in frequency for the rear.

I know that a lot use the FRC calculation, but it doesn't tell the whole story. It would be fine if we all drove around at steady state, but that's seldom the case. Because you have one damper per corner, you need to ensure that both ride springs and sways are matched properly if you want proper damping in ride (one spring) and roll (two springs).

P

PhilMD

Have a look at the ride height first, and see whether there's an issue with bump stop contact far too early. A combination of raising the height and spec'ing the bump stops for a softer transition may work.

Phil

JustinHoMi

Oh, good thread! Here's a simple question:

For a dual purpose car, can a shock be revalved such that it has maximum performance (autocross) and maximum comfort (street)? This assumes a given spring rate.

If not, what specific compromises must be made?

I understand, of course, that many other aspects of a race car will sacrifice ride quality on the street (bushings, springs, anti-roll bars, seat, etc). Edit: To be clear, I'm asking regarding the *shock valving* alone, on a car that has a high spring rate.

miatauser884

iTrader: (11)

I have SD revalved bilsteins on my car. I changed from kyb AGX and FM springs so I can't comment on a stock setup. I've used both setups at Barber motorsports park. The revalves are head and shoulders above the old setup for DD and track. Are there compromises. I'm sure there are. There was another thread that was referencing stock springs and not FM (which I have). Bernie was able to do a revalve that was endorsed by a pretty exceptional review. I have stiffer springs, and was going to revalve again until I used the car at the track. My car does not ride like a cadillac on the street, but when driven hard it is solid right up to the limit. As a dd it rides more like a BMW M. I hope this helps. If you have any more questions, send me a PM. I don't want to fill this thread up with off topic speak.

Disaster

iTrader: (1)

Impossible. There will always be a compromise. You have to decide how far you want to go.

Ride on the street. Handling on the AutoX. Ride height.

I've seen it happen over and over again. A guy starts out with a car that is "fun" in AutoX but finally gets to a point where he can't compete with cars with more purposeful setups. He starts incrementally changing the car till it is very competitive, but horrible on the street.

You have to decide if you need to win...or just have fun. IMHO, if you really want to compete to win it is best to get a car purposely designed for AutoX and a separate DD. The DD doesn't have to be boring. I know a few guys who have a pair of Miatas...one set up for the track, another for a DD.

JustinHoMi

You don't understand the question. I'm talking about performance pertaining to the shock valving alone. And I'm looking for specifics regarding the compromises that might have to be made to the shock valving.

FYI my car (with high spring rates) and Koni RACE shocks is great on the street. I have few complaints. As far as my class goes (Street Touring Sport), you can definitely have a winning car that is also a joy to drive on the street. But that's not exactly what I'm asking.

Disaster

iTrader: (1)

One specific I've seen, is specifically designing with too much rebound damping. This causes the suspension to ride down. This is commonly used in stock classes where you have limited suspension variables. Great for an AutoX course. Horrible for the street.

JustinHoMi

Yep, but like I said... I'm not talking about stock spring rates.