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Tuning Method Guide
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mike gt3
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PostPosted: Tue Dec 18, 2007 12:14 pm    Post subject:  Reply with quote

AH HA!

Thanks for that great explanation Shiny, this is starting to make some sense.  I've only thought about phases A, C, and E before - but if I'm understanding phase D right, during light acceleration you are increasing the longitudinal transfer some, but you're increasing the lateral transfer more.  Increasing the front rebound damping will help slow this lateral transfer and focus it more on the front end.  Essentially, this should reduce the traction at the front a little, therefore BALANCING traction at the front and rear of the car and reducing oversteer... yeah, that's making some sense (I think).

I guess this explains why you're working on oversteer in phase E using the rear bump, because you're using front rebound to correct for oversteer in phase D.  

FWIW, this may explain some of my tuning issues.  There have been a few cars (like the BMW in the new DLC pack) I've given up on because I just couldn't sort out oversteer.  I'll get the car to turn in well and hold good corner speed until apex, but as I start to gently ease on the gas, I start to lose the back end and have to back off.  I can't get the tune right using my usual approach (Of course, I'm *positive* that it's not my driving :smt001).  Stiffening the F rebound for phase D might be the answer - I'll have to go back to the BMW and give it a shot.
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Shiny Side Up!
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PostPosted: Tue Dec 18, 2007 1:37 pm    Post subject: Reply with quote

I have no idea if this will help you sort your BMW or not... typically, I would expect to see small improvements with that rebound change aimed at the part-throttle pickup exiting a slow corner.  If that is where the oversteer is stemming from, I would still expect softer rear bump to be more beneficial - but if you need something else to adjust, the front rebound increase may indeed be just the ticket!

Please let me know how it goes... personally, it has been a while since I tackled this particular problem, and I am interested to see how the adjustment works out for you!  :smt045
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Munkyworm
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PostPosted: Thu Jan 28, 2010 4:48 pm    Post subject: Reply with quote

I really feel I've mastered suspension tuning with FM3.  Currently i'm working on a better feel for my tire settings tuning (caster, toe, camber, pressure).

Anyway, onto the main point - this site is the key to shock tuning...
http://www.ozebiz.com.au/racetech/theory/shocktune1.html


Additionally, I combine one other shock tuning technique with this guide.  Because all race suspensions are coil-over in Forza, the lever arms for the dampers and the springs are the same.  This means that the ratios of front to rear stiffness hold with the sliders for springs and dampers.  In other words, for a rear wheel to have the same damping characteristics as a front wheel, the ratio of damping for front to rear should match the front/rear ratio you have on your springs.  I'll make an argument for doing things this way a bit later.

Here's an example.  Say your springs are currently 340 front and 500 rear.  This results in a front/rear ratio of 340/500 = 0.68.  To make the front and the rear of the car behave the same way over bumps and abrupt steering movements, you should preserve this ratio in front to rear  damping (both for bump and rebound).  So lets say you arbitrarily choose 4.3 for your front bump damper.  Your rear bump damper should then be 4.3 / 0.68 = 6.3.  You can then separately choose a rebound value for the front and calculate what the rear value should be in the exact same way.


By keeping the above as a constraint, you really only have 2 variables with dampers to adjust.  These are the overall level of damping (relative to the spring rates), and the balance of bump to rebound damping.

You may question the practice of making the front and rear behave the same over bumps.  First of all, I've found it works great in practice.  That should speak enough by itself, but additionally, think about what balance does to the car anytime you put transient forces on it.  For example, your car will behave the same way on corner exit as it does on corner entry, resulting in a very stable platform where you can really focus on hitting your marks instead of spinning out.  I promise - your car will never feel better going over bumps.

By doing the method I just prescribed, you can put emphasis on getting your spring ratios right (adjusting your dampers correctly to match with every spring change) without having the dampers front/rear ratio clouding your tuning judgement.

(There is actually a really good way to definitively set your spring front/rear ratio to the correct values too, but that's a trade secret of mine :P  (and it's not just taking the front/rear weight distribution and calculating it out).  If you're curious, my only hint is that I couldn't use this method in FM2.)
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kindadeadlikeme
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PostPosted: Sun Jul 31, 2011 2:44 am    Post subject: Reply with quote

Thanks
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PPS TurkScorpio
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PostPosted: Mon Nov 21, 2016 11:31 am    Post subject: Reply with quote

Im not sure about all this opposite stuff that you guys are on about, but it sounds like your forgetting a few things.  So I will try to simplify everything with concerns to oversteer.

There are three types of oversteer. And each type may have it's own sub categories, but I will keep it simple.  

Type 1 is Entering the Corner Oversteer
Type 2 is Mid-Corner Oversteer
Type 3 is Exiting the Corner Oversteer

Now each type of oversteer has different ways to correct it, These types of oversteers can also be affected by the type of car that you drive (Front, Mid, Rear engine cars).

However, I think everybody should realize that tuning isn't everything.  It helps, but you need to realize that your driving may also be the problem.  Every car is different.

If anybody needs help Tuning hit me up Ill do my best to help you out.
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