Learned some very interesting Moton info at PRI
12-19-2009, 10:40 AM
#32
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Agree. Most can't feel pretty big changes. The MOST experienced can tune each corner independently from what they feel. I can't feel enough to do individual corners and rely on data to balance each corner from basic settings from what I feel.
12-19-2009, 10:45 AM
#33
Lifetime Rennlist Member
The relationship between spring stiffness and damping coefficient has an optimal value at the vehicle heave mode frequency, such that the damping stiffness is slightly greater than the spring stiffness.
We can (hopefully) agree that the time the CPL spends below its mean value should be minimized after an event, such as going over curbing or a depression or bump in the track surface. The characteristics required for this condition include a high ratio of spring stiffness to unsprung mass (yielding a high unsprung mass acceleration), and a high ratio of spring stiffness to damping force (giving a high terminal unsprung mass velocity). This suggests that a compression biased damping setup will minimize CPL variation about the mean, use less stroke, though at the expense of ride quality (perceived harshness), which is irrelevant to us.
We can (hopefully) agree that the time the CPL spends below its mean value should be minimized after an event, such as going over curbing or a depression or bump in the track surface. The characteristics required for this condition include a high ratio of spring stiffness to unsprung mass (yielding a high unsprung mass acceleration), and a high ratio of spring stiffness to damping force (giving a high terminal unsprung mass velocity). This suggests that a compression biased damping setup will minimize CPL variation about the mean, use less stroke, though at the expense of ride quality (perceived harshness), which is irrelevant to us.
12-19-2009, 10:51 AM
#34
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so 90 what you're saying is we should be able (or be trying) to use softer shock settings and super heavy springs to keep the contact patch at a greater amount over time in a fuller range of motion?
when you talk about frequency stuff I think that's interesting as obviously that is track and car model specific- i.e. a sport racer vs a GT3 cup vs a 944 turbo will all have much different needs for load transfer speeds- how does it apply?
finally- GT-something ALMS teams have relatively dummy proof shock settings: it literally has a different labeled **** for each adjustment on the new RSR. high speed rebound, low speed compression, etc are all written out on the shock! it's pretty easy to tune because you always know what direction or what adjustment you just made.
when you talk about frequency stuff I think that's interesting as obviously that is track and car model specific- i.e. a sport racer vs a GT3 cup vs a 944 turbo will all have much different needs for load transfer speeds- how does it apply?
finally- GT-something ALMS teams have relatively dummy proof shock settings: it literally has a different labeled **** for each adjustment on the new RSR. high speed rebound, low speed compression, etc are all written out on the shock! it's pretty easy to tune because you always know what direction or what adjustment you just made.
12-19-2009, 10:52 AM
#35
Team Owner
Thread Starter
And I have to say "Huh?" to this post, as well. If you are going to tune for curbs, you either have very adjustable shocks (e.g. 5-way with blow off circuits for curbs) or you are just tuning the best you can with big compromise. No serious pro team uses off the shelf valving unless the rules require it, and won't even use the same setup for different tracks or different conditions at the same track.
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12-19-2009, 11:26 AM
#37
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12-19-2009, 11:47 AM
#39
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I will pass on what I also learned from the Moton folks: namely, that they believe many racers/shops set ride heights way too low, especially in the rear, and then are constantly fiddling with the suspension to chase the bad traits that come from this.
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Really low ride heights (as in formula, sports racers or even some the ALMS GTs) are for ground effects. You need to be around 1" dynamic ride height and also need very stiff springs to do this. This kind of setup is bad for mechanical grip but the gain in aero more than makes up for this. But if you take a non-aero car and go really low and stiff, you give up balance and mechanical grip but get nothing in return.
The other very common mistake is to run shock settings that are too stiff. This tends to feel better, and there is the misconception that stiff shock settings are better. This poor adjustment may feel good but it also gives up mechanical grip.
12-19-2009, 11:50 AM
#40
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You see it in the BMW Club Race paddock all of the time. Front and rear. Lower CG is good, but not if the roll center and camber curves are shot to hell. You can introduce more roll, less suspension travel, bottoming, increased roll couple between front/rear, etc, etc. Look at the fastest cars around the paddock in Prepared (i.e. a class where you can't change suspension mounting points to improve geometry) and they are running quite a bit higher than the average DE car or slower club racer.
12-19-2009, 11:55 AM
#41
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+2 on Sunday & Bryan. Heck, you even see it in the pros. Look at photos of various Koni Challenge cars... 
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12-19-2009, 02:13 PM
#42
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The relationship between spring stiffness and damping coefficient has an optimal value at the vehicle heave mode frequency, such that the damping stiffness is slightly greater than the spring stiffness.
We can (hopefully) agree that the time the CPL spends below its mean value should be minimized after an event, such as going over curbing or a depression or bump in the track surface. The characteristics required for this condition include a high ratio of spring stiffness to unsprung mass (yielding a high unsprung mass acceleration), and a high ratio of spring stiffness to damping force (giving a high terminal unsprung mass velocity). This suggests that a compression biased damping setup will minimize CPL variation about the mean, use less stroke, though at the expense of ride quality (perceived harshness), which is irrelevant to us.
We can (hopefully) agree that the time the CPL spends below its mean value should be minimized after an event, such as going over curbing or a depression or bump in the track surface. The characteristics required for this condition include a high ratio of spring stiffness to unsprung mass (yielding a high unsprung mass acceleration), and a high ratio of spring stiffness to damping force (giving a high terminal unsprung mass velocity). This suggests that a compression biased damping setup will minimize CPL variation about the mean, use less stroke, though at the expense of ride quality (perceived harshness), which is irrelevant to us.
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Larry Herman
2016 Ford Transit Connect Titanium LWB
2018 Tesla Model 3 - Electricity can be fun!
Retired Club Racer & National PCA Instructor
Past Flames:
1994 RS America Club Racer
2004 GT3 Track Car
1984 911 Carrera Club Racer
1974 914/4 2.0 Track Car
CLICK HERE to see some of my ancient racing videos.
12-19-2009, 02:38 PM
#44
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12-19-2009, 02:53 PM
#45
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If the latter, that sheds a different light on things.
It is, btw, also an engineering abbreviation for plate stiffness but I don't see how that has much to do with this kind of suspension discussion.