Perplexed about Packers

I thought I knew how to setup the relationship of ride height and packers, but now I'm beggining to wonder.

It has been my thought that packers should be a lower number than the ride height.

1) Set ride Height
2) Check to see if your bottoming out under high speed
3) If yes, add packers until you are riding on THEM, instead of the plank, in high speed sections
4) Watch trace in high speed corners
5) If your riding on the packers in corner, raise ride height.

In this way I often have a ride height roughly 3mm higher than packer number in the front , and a good bit more in the back. Probably 10-15 is the difference between ride height and packers.

Of late, I've seen some setups where the packer level is more than the ride height level. If that is TRUE, then my whole idea is crap! I'd think that you would be in a constant state of bump rubbers and the packer level would over ride any ride height.

Somebody set me straight.


JohnW

i run packers higher than the ground hieght.

run as much packers as possible until you are not being effected by them in the high speed bumps on the track.

basically,

do a few laps with your original setup. then download lap to telemetry and trace it.

then adjust packers by adding more/less then download to telemetry and then superimpose both of the laps.

use the functions to see(suspension travel) where you have bottomed out on the packers, and if you have then reduce packers.

the last thing you want is to hit a bump in the track at 200mph for your suspension to compress so much that you hit the packers. this would then cause a big shock thru the car and make it unstable. especially in the corners.

JohnW, your idea isn't crap. There are just some thing that you don't know about GP4.

1) Putting 35mm of packers into a space that is 24mm is physically impossible. But GP4 still allows for that to be done, and the physics should model rock hard suspension for every wheel at all times on the track (more about that later). That it still can be done, can be called a flaw in the setup menu of the GPx series, and it has been present since god knows when. That somebody have found a system that works for them, which uses this doesn't make your understanding invalid. The numbers that your approach delivers sound very reasonable and are very similar to those I use and also got out of gp3 and gp32k. I would rather say, that those that use "impossible" amounts of packers found a loophole in the physics.

2) the ride height and available suspension travel traces in GP4 are suspect to say the least. Try and put front and rear ride height at 40mm and give the car 39mm of packers and then do a lap at 10kph, just to make sure that nothing compresses the suspension. Then check the traces and you will see what I mean. Ride height should only vary between 40 and 39 mm and available suspension travel should vary between 1mm and 0mm. But they don't. I have posted my method to work with this problem elsewhere on this forum, but I have not posted my latest developments. They will come. However, I feel pretty confident that someone else will come up something better, so it would be great if others did the same.

3) packers (or bump rubbers) are solid and not flexible. However GP4 seems to allow the packers to compress as the amount of force on the suspension is increased. I have no idea if this is realistic, but every description I have seen of bump rubbers say that they don't. However, I can understand why some would argue that rubber that experiences 3 tons of pressure does compress no matter how hard it is. Whatever the case may be, just plan with the fact that in GP3 they didn't and in GP4 the do compress at the extreme end of the performance curve.

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It's only after we've lost everything, that we are free to do anything.

Run as much packers as possible - yep thats correct.

By the way - remember that you get a much harder chassis settings and this can cause problems on some tracks where you need softly chassis settings. Thats the same on wet races. Its nearly impossible to get good laptimes if you use high packer settings.




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One problem with packers, run to many u can not use curbs as u end up with no susspension travel and u spin.

SchimmyMike,

Would you care to be more descriptive ?
I could run at MAX packers, but I suspect I would have a very stiff suspension and very little mechanical grip , in the corners.

Morbid,

I've wondered about the telemetry. I was working on a Barcelona setup, but I couldn't seem to keep the car off the packers in the long right hander , which is the third corner. I kept raising the ride and lowering the packers, but I was still on them.

Here is a blurb from the setup guide , in GP4.
" ...if your lower the car 3mm you need to increase the packers by 3mm . "

That seems very odd to me.

Perhaps I need to know WHERE the packers actually are, within the suspension. I think that most of the springs , dampers, and packers are all laying above the drivers legs , in the nose of the car. Even though the wheels go up and down, this is translated into forward and back motion in the nose.

I've always thought that you could envision a formula like ( Ride Height - Plank thickness ) = packers

So, if the plank is 10mm and your ride height was 25mm, then you could put in a max of 15mm of packers. Of course you'd constantly be on them, since there is no play left in the suspension travel.

Since lowering the car gains "free" downforce, getting the car as low as possible is a GOOD thing. Keeping it low , but of the plank is more difficult. Keeping it low, off the plank, AND off the packers , in the corners, is an ART.


JohnW

It took me ages to get a good setup for spain and austria but i won in spain and got pole and am leading in austria.

If anyone wants them email me and i will send.

You are right, go as low in ride height as you can, because the undercar downforce is drag free, and of extreme value. Especially in Spain, with the two last corners being very difficult high speed corners. The alternative to free undercar downforce is more wing, and the rear wing increases drag and hence lowers top speed on the straight.

Here is a blurb from the setup guide , in GP4.
" ...if your lower the car 3mm you need to increase the packers by 3mm . "

Yup, I remember that part. Page 99 of the manual. I remember having some disturbed thoughts about that in the dark hours of night. I can't make sense of it. The only way it could make sense is if the buttom of the shaft (or whatever gizmo it is) that holds the springs was extended with 3mm when ride height gets lower by 3mm. That would make the sentence meaningful.

But it isn't like that. You original concept of how the packers are placed is correct. You can check that, by looking at the videos in GPedia for gp32k (might still be present in GP4, can't remember) where Mark shows how the packers are placed in the suspension of the Arrows car.

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It's only after we've lost everything, that we are free to do anything.

Hmmm,

I couldn't get GP32K, here in the states, so I have the original GP3, and now GP4.

Here's where my thoughts on the whole packer thing sort of go off. If the plank is 10mm, then if I set the ride height at 10mm and assume no suspension movement, then I should be just scraping the plank, all the way around. If I then raise the ride height to 20mm for instance, and assume no suspension travel, I should have 10mm of clearance. Ok, so far. Now, I actualy WANT suspension movement , but just how much ? Let's say I want 5mm of movement. That means I should be able to set the ride height at 20mm, and put in 15mm of packers. That means the suspension can travel from 20mm above the ground to 15mm above the ground, ( Where it hits the packers. ) and still have 5mm of clearance, before the plank starts getting scraped away. It all sounds correct, but I can never get the settings this low. In fact, it is more often the case that anything lower than about 24mm of packers will allow the plank to drag. This may vary, based on how stiff the springs are, I think.

So either the plank is thicker than I thought, or the packers allow a lot more movement past their height than I figured on, OR...the settings are just roughly simulated.


JohnW

Nice thread title by the way.



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