Assuming spring rates are the same and all other components on the Evo is stock:

How would the car behave with single adjustable shocks if the rears have more dampening than front?

If the front has more dampening than rear?

thanks.

 

ttt for insight.

 

Dampening is subjective.... using dampening to control roll rates and body movement is much easier when you can adjust compression and rebound separately. If you want to understand how shocks control body dynamics its easy to think of the tires being Velcro and the track also being Velcro so the slip of the tire is eliminated. Now imagine that the only way the car can go faster around a turn is to use body roll… roll=grip to a degree.

That said… more compression in the front will not allow the car to dive under braking and turn in. Less compression in front WILL allow the car to dive and hold on turn in.

Less rebound in the rear will allow the weight to transfer forward and also help in the process of grip in the front.

Now under acceleration, if you have high rates of rebound in the front, the piston won’t let the front of the car lift under acceleration keeping the front of the car down and weighted. Where high levels of compression in the rear will also aid in keeping the weight front moving to the rear. (the opposite of a drag car… soft in the rear to transfer weight to the back of the car).

The problem with using dampening to control vehicle dynamics is that there are usually two ways to achieve the same goal. As in some people would say that more compression in the front will transfer weight to the front faster = more grip.. so there is two ways of doing it. And there are so many other variables (weight distribution, roll center and sway bars).

I’m still learning as well… I’m having a custom set of 3 way adjustable Penske shocks made for my evo, so I’ve been reading and learning from the race team that’s building them.

Sorry if I didn’t explain this in an easy way to understand…

-Kyle

 

I have to disagree with that. Weight transfer *happens*, pretty much regardless of how the suspension responds to it. Fore-aft weight transfer is governed by the (instantaneous) height of the center of gravity and the wheel base. If you have very high rebound damping in front then under hard acceleration you'll pull somewhat more weight off the front tires as they move with the rest of the body.

Anyway, Mike, I know you just got the Zeals, so don't over-think this! Set 'em around the middle of their range, or whatever Zeal recommends, try it, and experiment. These are hobbyist dampers, so no matter how many "clicks" they have, you don't have independent compression and rebound, and you really can't be certain what's going on inside when you turn the dial. If you really want to get in to this stuff, fork out the bucks and pick up the Millikens' "Race Car Vehicle Dynamics." Like the crew chief talking about his too-picky driver: "At some point you just gotta say, 'Nancy, get in the car and drive!'"

Dave

 

True... but dampers will aid in weight transfer a bit, pitch, roll and squat.

Weight distribution, CG, springs, swaybars, allignment and corner weights all together make up 90% of weight transfer dampers are 5-10% of the mix.

Millikens' "Race Car Vehicle Dynamics." is a bit "old school". Good book, but it doesnt have enough on dampers.

-Kyle

 

I would have to agree, and say that high front rebound will aid in slowing the rear-ward transfer of load during a hard launch. While the same *amount* of weight will be transferred, in theory, higher rebound will slow the rate at which that load is transferred to the rear, all other factors remaining equal.

Since rebound is usually thought of in terms of controlling sprung weight, and not unpsrung, I do not see high rebound as being able to "pull" weight off the front tires at all.

For all it's complexity in other areas, I felt that RCVD did a pretty good job in covering the basics of damping in an understandable way; if not *how* to design valving, it at least described some of the concepts behind dampers. Yeah it seems dated due to what it doesn't cover, which you can easily find all over the internet nowadays. BUT the question is, which internet sources can you trust as much as RCVD or the Milliken's?

 

Typically the higher the damping rate the more quickly weight is transferred. Sure, the chassis doesn't pitch as quickly, but the weight transfer is there. Suppose you had a rigid "suspension" (what you'd have in the limit of infinite damping rate) there would be no pitch (except for that allowed by the deformation of the tires, assuming they don't lift completely off the ground!) but, again, you'd still have weight transfer, and you'd have it fast!

I know Mike, hence suggesting RCVD. There's a reason why half the book is about tires and model systems and only a chapter on dampers -- without the basic physics a lot of advanced detail wouldn't be useful. Also, on a mostly stock car, with squishy bushings all over the place, some of the finer points that you guys might have to deal with are going to be washed out. I think I see the point you're getting at, but there are a lot of folks who think that by going to high spring and damping rates to minimize pitch and roll they're actually reducing weight transfer -- pitch and roll are an effect, not a cause!

Since the original question was about how the car will behave if... The best thing to do is just try it and see. I've seen a few posts about "what setting should I use on..." Not that there's anything wrong with asking what works for other people, but if someone buys zillion-way adjustable coilovers and can't tell for themselves what settings work better than others, then they probably didn't need them.

Dave

 

Dave you're right. I'm looking way too deep into this, since it is only a single-adjustable system. This weekend is my first chance for a "test and tune" session, so I'll just have to find out with real world experience.