Quick Question about Dampers

[scottnorbury]

Hi,
I'd first like to introduce myself, and say a big hello to you all. Also THANK YOU for so much great information about racing sims on this forum.
I have been driving sims for a while GTR in its various guises, rFactor, Richard Burns, LFS, neKar Pro etc.
Now i have reached my limit, I'd like to learn a little about tuning using the motec tool. I've got most of it, as it's pretty straight forward, I'm just bewildered by springs and dampers. I've read lots of info on here and elsewhere, I just can't get the various settings and their effects sorted in my head.

Could any one explain these in really simple terms?

One thing that confuses me the most is dampers, I've read about using motec to help fine tune them. I just can't workout which way to adjust them so if the chart is blue do i click the plus or the minus, on the bump or the rebound the fast or the slow. Speeding them up or slowing them down doesn't help that's what got me confused. Just wheather to click the plus to turn my chart blue or yellow?

Hope that makes sense it's 3am and i've been driving round the Nordschliffe for hours.

Thanks for any help in advance.

Scott

[m0ng0l]

They are bewildering because they can produce the same effect when pushed to either extreme (soft, hard), and if you get the pairs mixed up, you sometimes really have no idea where to go.

Tweaking the dampers should be one of the last things you do when setting up the car. Take care of the gearing, wings, brake balance and temperature and other tidbits, and pay special attention to differential locks, because they have a lot to say about understeer and oversteer and affect the car into, out of and through corners. Camber and pressure will have to be tweaked several times as each change of the setup will affect tyres. Caster and AntiRoll Bars can completely change the way the front wheels behave while cornering. All this can create problems for damper settings and you could lose your mind trying to fix everything that went wrong at once.

For example if you had the brakes setup wrong, and you fixed it, your car would now have much better deceleration, and that would cause weight transfer to be different under braking and corner entry, so the dampers would need adjusting. You can see why it's better to take care of all things that demand damper adjustments before you try to find ideal damper settings.

I prefer my dampers very stiff and the suspension average-below average stiffnes while i'm working on a setup. Then when i get the car to behave the way i like, i fine tune the dampers. Based on experience i might even "guess" where the dampers should be, but until the rest of the car is fit for the track and handleing to my liking, i won't adjust the dampers.

Instead of looking at the suspension histograms...

- take a look at ride height to see if the car is bottoming out
If it is, raise ride height or stiffen the suspension.
If it never comes close, lower ride height to lower the center of gravity

- keep checking the tyre temperatures
Inside should be 5-7 degrees higher than outside (front), or 3-5 degrees (rear)
Keep adjusting camber untill you get those temperatures. (keep in mind that one side of the car works harder because the number of left and right handed corners isn't equal)
Middle temp should be between inside and outside. That indicates correct pressure. Just remember that when you adjust camber, you will probably have to adjust pressure as well.
On tracks with long straights, pressure can be a bitch to set right. You have to focus on the turns where the car leans to one side, and check the temperatures there, not the straights.
Having tryes that correctly grip the surface is more important than most other settings.

I also suggest you check your differential before you go for dampers.
- a low cost lock allows the rear wheels to have a greater difference in speed (when no throttle is applied), which greatly helps the car turn into corners, but it can can cause massive oversteer if the car turns in too easily and the rear tyres loose grip. High coast lock settings doesn't allow such a difference in wheelspeed so the car doesn't turn in so well but also doesn't spin so easily. A badly set coast lock can develop oversteer or understeer on an otherwise neutral car.
- low power lock also allows a greater difference in wheelspeed but this time only when under power (throttle is applied). This is bad because some of the power is wasted and the car is not so fast when exiting corners, but if there is no wheelspeed difference (100% power lock), there is no cornering benefit while the car is still exiting the corner. In fact the car may develop massive understeer and force you to get on the throttle much later through a corner.
To see what i mean, try a 0% coast and 100% power lock.
- low preload makes the effects of coast and power lock more pronounced. High preload subdues the effects of coast and power lock. It's not quite that simple but that's the jist of it.

I hope you see how differential can affect everything from lap times, corner entry/exit and even your driving line.

I apologize for a complicated reply, but i hope it was usefull.

[scottnorbury]

Hi m0ng0l,

Thank you for a very detailed reply.

I seem to be able to get a good balance to the car and a nice feel, but I'm not sure if this gives good times.
I started looking in to the damper settings out of curiosity more than anything as it was a weak area of my understanding and like you said there's lots of cause and effect on these settings.
I understand that the fast bump/rebound controls the small sharp fluctuations and that the slow bump/rebound effects how the mass is controlled.
So the fast rebound should be a lower number than the fast bump to allow the tyre to return quickly to the surface?
The slow bump on the front should be raised and the slow rebound on the rear raised to control the transfer of mass under braking?
Just checking that my understanding is somewhere near.
Your explanation on diff settings helped, mine is a lot clearer now. I seem to have a good balance on the diff as I like the car to turn in nicely off throttle and just a hint of oversteer on throttle. I try to have preload set so I don't get snap lift off oversteer.

I've found as I have been experimenting with damper settings that I do revise these diff settings occasionally as the grip in\mid\exit of the corner improves.

Tyre temps, pressures, camber I have got. Castor is a bit vague so is toe in\out, helps turn in?

Thanks again for your reply. I hope you or others can assist me in the other areas that I'm not to sure on. If I have any other issues I'll post back here.

Cheers

Scott

[Damper]

Dampers +1

(couldn't resist)

[Nectaria]

Caster can easily be explained by imagining the front fork of a motorcycle. The angle where the fork is in is the amount of caster, the sharper, the more direct the steering input, the lower the better the straightline stability. Compared a Suzuki GSX 1000 R to any Harley Davidson and you'll understand why one turns in faster then the other. That's just the caster that does that. Overdoing this will create a very twitchy car with little stability.

Toe in is generally what you will be working with in GTR2, the more you toe-out your tires, the more direct your initial steering into the corner will be. That's generally at the front. You would be working toe-in at the rear to increase that straight line stability, and increase top speed. Overdoing these will cause excessive tire wear and instability.

[m0ng0l]

You're absolutely right. A car that is closer to the "edge" is definetly faster but it can be really difficult to drive. A setup should evolve from something that is comfortable and easy to handle towards a faster, less compromising setup. So long as it doesnt hurt the drivers confidence in attacking the track, when it becomes counter-productive.

And the dampers... actually the spring pushes the wheel down, and the road pushes it up (well the weight of the car does but...). The dampers act on the spring to control how quickly the spring can be compressed/extended. A stiff damper offers extra resistance when the spring is being compressed and it resists the spring itself, when it extends. A soft damper would not resist the energy that is compressing the spring as much, and it would not resist the spring as it's extending as much as a stiff damper would. That's relatively straightforward but, the results on car handleing differ quite a bit when the springs themselves are soft or hard.

It's not allways ideal to have a damper that equally resists spring compression and extension, that's why some dampers can be set differently for bump(compression), and rebound(extension). Typically rebound settings should be stiffer or equal. Typically...

Just remember that it's the spring that actually absorbs/releases energy, not the dampers. They control the speed of the process. The idea is to let the springs absorb/release energy in a way that doesn't cause the car to lose speed or stability. Yeah, easier said than done...

Raising the slow rebound on the rear will resist the energy being released by the rear springs, and raising soft bump in front will resist the energy compressing the front springs. That doesn't really say much. How hard are the front springs? How hard are the rear springs? Softer springs allow more damper travel, and ride height changes. Even camber can be affected, but i think the most important question is not about dampers but about grip. How's the grip front and back? Front wheels with more grip will naturally cause oversteer, while rear wheels with more grip cause understeer.

As the grip into/mid/out of corners changes, use dampers (or something else) to make sure a pair of wheels isn't getting more or less grip than it needs. I say more or less, because improving grip usually means upsetting the balance somewhere. Since differential adjustments can reduce or improve grip on the rear wheels, you might have to adjust dampers (or something else) to alter grip for the front wheels.

In the end it's all about grip and how to balance it.

Caster i usually don't muck about with. I know that more is better but too much interferes with front ride height difference, and can prevent the inside front wheel from reaching the road as the car leans away from the corner. I tend to keep it as is.

And toes... well they can deal with some undesireable effects caused by left/righ pairs of wheels. An outside front wheel travelling around the corner typically has good grip since the camber helps it grip the road well, the weight of the car pushes it down nicely, there is no differential coupleing to connect it with the inside wheel, and since it is the hardest working wheel in that case, you logically want it have good grip. So what does the bastard do with all the grip? It pulls away from the corner... It not quite understeer since it's not caused by the rear wheels pushing straight forward, but the effect is similar. So toe can be used to help that wheel turn in more. On the straights, it is not desireable because it causes something similar to having thinner tyres. The surface of the tyre that offers good grip is smaller. This is unwanted in rear wheels since they deliver all the nice horsepower, but if a track has few or no straights and a lot of corners toe can be a good idea.

I'm allways happy to offer my thoughts on these things, because honestly, it helpes me as well. I also despair at silly readings in MoTeC and wonder what the hell it will take to improve a stubborn setup. In fact, your toe question just gave me an idea to try out.

So thanks.

[scottnorbury]

Thanks Folks for your help in getting my brain to understand all this. It's finally sinking in.

I'm been having a play with the Alzen(?) Porsche in Race On round the Nordschliffe with the GP circuit started of around the 9min mark and came down after every adjustment which to me says I'm heading in the right direction with my tuning, dialed out the initial straight line wandering of the default with some toe in balanced the car a bit more to my liking and it started to feel more comfortable which translated into more confidence to attack, and to carry more speed into and through turns where I'd previously have lifted off or even braked. Definitely a better setup.

Thanks for your help.

Scott

[darock]

About the only value messing with shock settings will give is the practice you get screwing with them.

If you'd like to test how effective they are, do something I was told back in the day when first driving a race car, a real one. While changing the settings in the paddock during practice day before a weekend event an old sage suggested I run a few laps with a "bad shock" at each corner. He said I'd learn a lot. I adjusted that shock to minimums and ran a lap or two. Came in and set it right and did the other front to maximums and ran another lap. A couple of years ago, when screwing around with settings in the sim, I decided to see if it simulated. Try it yourself.

An eye opener to try....... Set one front to minimums, the other to maxs. Do the opposite to the rears. Run a few laps, or as many as you want. Because you're going to be running the same lap times you did up to then, that is, if you can keep the idea that shocks work in the sim from messing up your driving.

And if you have followed the MoTeC discussions about shocks you might have already have come to the conclusion that they certainly don't have any clear, logical way to set them. Basically you can set anything and unless it screws up your mind, you won't see any lap time changes good or bad.