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Do Bump Rubbers Work The Same In '69 As Other Mods?

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#41 John Woods

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Posted Aug 03 2010 - 02:14 PM

Caught me guessing again.

But now I understand. When I spin, every other time I go faster. Thanks.

Edited by John Woods, Aug 03 2010 - 04:40 PM.

#42 grego



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Posted Aug 03 2010 - 03:18 PM

.............and i have found a nice way of spending time by keeping a spinn going using the wheel and the accelerator.
i used to do it just for some smokin fun and can keep the spinn going for many rotations.
who would have guessed it would make me into a champion racer .........................;)

Edited by grego, Aug 03 2010 - 03:19 PM.

#43 Wozza_UK


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Posted May 10 2016 - 01:22 PM

Firstly, I apologise for bumping an old thread but this is GPL and old threads can still be new ones right? No sense in creating a new thread when all the relevant info is held in this one.

Anyway I was greatly interested in the graph posted on page 2 by Lee200 that shows the bump/rebound settings in GPL. I have been trying to develop a new setup over the last week and this graph completely changes my opinion on how to use the dampers in GPL.

From my research on the web I am led to believe that rebound should always be higher than bump because in a car the sprung mass (body) is always heavier than the unsprung mass (wheel) etc etc. This graph shows me that I have been doing it wrong. I have been dutifully using settings like 3 bump and 4 rebound thinking I was doing it correctly, when I should have been using 3 bump and 2 rebound. :really:

Anyway, now to my question. Maybe some of you setup gurus can answer this: in a car, which set of dampers generally speaking should be stiffer, front or rear?

Logic tells me the dampers at the rear of a rear-engined car should be stiffer because they would support the weight of the engine. But how about in a front engined car? Would it be reversed?

Or is it be based on some other parameters?

Any help appreciated. :rolleyes:

#44 M Needforspeed

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Posted May 10 2016 - 02:02 PM

 Lee200, on Aug 03 2010 - 06:31 AM, said:

 MECH, on Aug 03 2010 - 04:48 AM, said:

Well that got my attention  :huh:
So they have the data for the head movement but failed to implement that?

Pity  :duh:

Mental note: must figure out a bypass to get the wheel turning applied to the head movement :think:

Hi Martin,

Have no idea how to do that.  Nigel did, but he's long gone now.

In fact, just before he left he was working on adding another two rigid bodies; one hub for each of the rear wheels in order to correct a bug where they weren't tilted properly.


thanks again Lee,

Five years after your post, you handled the work successfully and give us those great drivers heads movements . Or is it a shared work with Martin?

Edited by M Needforspeed, May 10 2016 - 02:04 PM.

#45 gregc


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Posted May 22 2016 - 06:47 AM

Wozza_UK - great thread, thanks for bumping.

#46 John Woods

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Posted May 22 2016 - 10:10 AM

Truly this thread has to be among the best ever.

One of my most favorite anyway. Mostly because I appreciate it very much when Lee explains things and he dumped a boatload on us here.

Thanks once again Lee for everything.
And Saiph for starting the thread.

Not that I really know enough to offer an expert opinion...but anyway...it took me many years to appreciate at least some little bit the interactions of various components relative to a car's motion.

It is still all questions and guesses.

Shocks are not the same as springs. They do not support a car's weight, (except for load leveler air shocks and height adjustable coil overs which we don't care about here).

Shocks dampen springs and all car suspension motion, so it all moves faster or slower depending on the shock setting. Shock settings determine the speed at which the springs are allowed to travel.

If springs are set at 100lbs, at 1inch of deflection the spring's resistant force will be 100lbs. This does not change due to shock settings, which controls how fast or slow it will take the spring to get there and back. Stiff shocks move faster.

The easiest way for me to think about it is from the POV of the car's center of gravity during a turn, (CG or CoG). First, the CG moves away from its static position, creating a dynamic center, then it moves back. There are subsidiary centers of gravity for the front and rear. So, three CGs to think about.

Ideally, the centers should only move out once, to the exact required position demanded by the car's position in the turn and the forces acting on it, then move back to the exact position of static center.

That's two moves only and this only happens when shocks are in tune with the rest of the car. If shocks are too soft, (allowing too much time), and unable to fully dampen the suspension, the car will bounce back and forth a few times before settling on static center.

The most important component to tune shocks to is the diff because it also controls the speed at which the car's rear moves to and back from a dynamic center. Shocks that are out of tune will fight the diff rather than complement it and allow it to do its job, which is to move the rear away from and back to static center by application of throttle.

This is how the car is steered with throttle...by controlling the diff.

If you let off, the car turns in. If you apply throttle, the car turns out because the diff causes understeer during acceleration. So, sometime during entry, using coast point the car to the inside of the apex then apply throttle which will hold the rear in place by increasing grip and move the front out by causing push.

The fastest diff setting in Grand Prix Legends, using Lee's Setup Manager, is 15/85. (Thanks Pete, for pointing this out awhile back). In other words, when using this setting, the diff is most capable of quickly moving the car's rear from static center to its dynamic center position and back. (If set at 15/15, it will quickly move out and slowly move back in).

The fastest shock setting is 5. No idea why, but I have found cars do not like a setting of 5 in bump...seems always slower with that, so now use 4/5 in front and 3/4 on the rear because RL racers suggest the rear shocks should be slower than the front. Maybe they are slowing the diff's influence on the car so it is easier to control the rear with throttle?

Whatever, (this isn't RL its Grand Prix Legends), and just my preference, when going into coast to set the car on line to accelerate past the apex, I want to be in coast the least amount of time, so I want the fastest diff I can handle and the quickest shocks.

When lifting throttle, the diff goes into coast and the rear moves out, turning the car as if using the steering wheel, (but not), which points the front toward the inside of a corner without using the steering wheel except to hold the car on the resulting line by applying a slight bit of countersteer and pushing the front into the track camber thru the turn. This is noted by tire sounds caused by slip.

More slip angle equals more tire sound. But too much slip will slow the car, so the ideal is some slip but not too much. In other words, if there is too much tire sound, there is too much slip and the car is scrubbing off speed it shouldn't be losing.

You might try this test: set the diff at 15/85 and try the shock settings 4/5F and 3/4R, then try 3/4F and 2/3R. Think you will note a distinct difference in how the car reacts thru a turn...it will move to and from dynamic center at a slower rate.

Then try 30/60, 45/45, 60/30 etc and you will sense the difference you are making in how the car sets itself thru a turn and what happens when you vary throttle. Any or either way, you want the fastest diff you can handle.

Somewhere in the middle of all that you will find a combination of shock and diff settings that is just right for you.

Then tune brake bias so you do not interrupt the diff's intention of taking the rear out to where it needs to be. It will go there by default and the springs will stop it if you let it all happen before freaking out and using the brakes.

Hope this helps, didn't edit it much...sure others will have a different opinion and will maybe/probably correct me on some of it.

Edited by John Woods, May 22 2016 - 10:24 AM.

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