Learned some very interesting Moton info at PRI
12-19-2009, 03:58 PM
#47
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To respond to CJ,
I'm simply noting that many teams at different levels of racing are moving away from the 'standard' rebound biased damper setup to a compression biased one, for the reasons given above.
My apologies to Larry for my patronizing language, won't happen again.
I'm simply noting that many teams at different levels of racing are moving away from the 'standard' rebound biased damper setup to a compression biased one, for the reasons given above.
My apologies to Larry for my patronizing language, won't happen again.
12-20-2009, 02:34 AM
#48
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I put my hand up as someone who had their car set too low. Couldn't figure out why I was getting so much push understeer in slow corners. Especially downhill, under brake load hairpins. Turns out it had run out of spring free travel and it was compressing into the bumpstops too much. Fought with shock settings and sway bars but it was 'Bandaid' fixes. Finally did some measurements and wound up raising the car by about 2cms. Hey Presto, problems pretty much solved. I have a set of CS with the 0-6 sitting on the shelf waiting to go into a new car. I think I'll be fine with 7 levels of adj by the sounds of it. 
12-20-2009, 08:47 AM
#49
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One thing that I have learned about racing is that there are no absolutes. From someone who has had a car that was properly built to sit VERY low, it can be done if everything is designed right from the start. The biggest mistake that I see is that most run too soft a spring for that. If it is going to be low, and there are good reasons for that, it must be 1500 lb+ stiff. My car was a dream to drive, and very forgiving, even in the wet.
The other thing that is not an absolute is that it is impossible to feel the finer gradation in shock settings. Once again, if you run softer springs, then yes the difference between clicks does not have as much effect, but with the really stiff springs, one click on a 15 setting Moton can be like night and day. I found that 3 click changes were massive.
The other thing that is not an absolute is that it is impossible to feel the finer gradation in shock settings. Once again, if you run softer springs, then yes the difference between clicks does not have as much effect, but with the really stiff springs, one click on a 15 setting Moton can be like night and day. I found that 3 click changes were massive.
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Larry Herman
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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.
12-20-2009, 09:07 AM
#50
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One thing that I have learned about racing is that there are no absolutes. From someone who has had a car that was properly built to sit VERY low, it can be done if everything is designed right from the start. The biggest mistake that I see is that most run too soft a spring for that. If it is going to be low, and there are good reasons for that, it must be 1500 lb+ stiff. My car was a dream to drive, and very forgiving, even in the wet.
The other thing that is not an absolute is that it is impossible to feel the finer gradation in shock settings. Once again, if you run softer springs, then yes the difference between clicks does not have as much effect, but with the really stiff springs, one click on a 15 setting Moton can be like night and day. I found that 3 click changes were massive.
The other thing that is not an absolute is that it is impossible to feel the finer gradation in shock settings. Once again, if you run softer springs, then yes the difference between clicks does not have as much effect, but with the really stiff springs, one click on a 15 setting Moton can be like night and day. I found that 3 click changes were massive.
12-20-2009, 09:35 AM
#51
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Very true SD, and stiffer springs can severely limit mechanical grip. More than a couple of Porsche teams have tried to increase rear grip by softening rear spring rate, only to find that the suspension now moves more, causing the car to feel 'squirrely' (indicating a kinematics issue with the rear suspension). The solution ended up being oversized tires, and moving the suspension pickup points.....
CJ mentioned frequency; that frequency content would be different from surface to surface. As cars circulate the track, the surface will be deformed at the hub mode frequency, around 3-4 cps. This is easy to see in braking zones where high-powered cars have been running, and can be seen on everyday roads as well where heavy truck traffic imparts the suspension frequency to the road surface.
At some point, this becomes a circular thing; as the road surface is distorted it becomes a forcing frequency. So this pattern is reinforced even in vehicles with different (higher) hub mode frequencies.
CJ mentioned frequency; that frequency content would be different from surface to surface. As cars circulate the track, the surface will be deformed at the hub mode frequency, around 3-4 cps. This is easy to see in braking zones where high-powered cars have been running, and can be seen on everyday roads as well where heavy truck traffic imparts the suspension frequency to the road surface.
At some point, this becomes a circular thing; as the road surface is distorted it becomes a forcing frequency. So this pattern is reinforced even in vehicles with different (higher) hub mode frequencies.
Last edited by the90; 12-21-2009 at 02:23 PM.
12-20-2009, 05:10 PM
#52
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t90, what is your technical background. You seem to have a fair grasp of all this, well enough to confound and convince me....no major feat mind you.
To touch on Larry's point about setting a car up from the get go. How do you actually do this in brief terms? What comes first, chicken or egg?
Assuming you have design parameters largely preset by the design of the car so choices like altering pickup points etc are unavailable. My guess is that you gather enough information based on precedent and you order your suspension 'kit' around these numbers. So for a 'kit' to work properly we need to stipulate springrates and then the manufacturer would setup the shock valving around these. What about ride height?
I remember ordering my KW Competition kit and you fill out a question sheet. Things like intended use of car (track, rally, hillclimb etc) power, weight, corner weights etc. Do all companies cover this off? Perhaps more comprehensively I'm sure.
To digress (in context), I have a set of Moton CS that I bought unused from someone else. They have spring rates of 750/850 and I am going to want to increase these. Do I need to have the shocks sent back to have revalved?
To touch on Larry's point about setting a car up from the get go. How do you actually do this in brief terms? What comes first, chicken or egg?
Assuming you have design parameters largely preset by the design of the car so choices like altering pickup points etc are unavailable. My guess is that you gather enough information based on precedent and you order your suspension 'kit' around these numbers. So for a 'kit' to work properly we need to stipulate springrates and then the manufacturer would setup the shock valving around these. What about ride height?
I remember ordering my KW Competition kit and you fill out a question sheet. Things like intended use of car (track, rally, hillclimb etc) power, weight, corner weights etc. Do all companies cover this off? Perhaps more comprehensively I'm sure.
To digress (in context), I have a set of Moton CS that I bought unused from someone else. They have spring rates of 750/850 and I am going to want to increase these. Do I need to have the shocks sent back to have revalved?
12-20-2009, 11:33 PM
#53
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t90, what is your technical background. You seem to have a fair grasp of all this, well enough to confound and convince me....no major feat mind you.
To touch on Larry's point about setting a car up from the get go. How do you actually do this in brief terms? What comes first, chicken or egg?
Assuming you have design parameters largely preset by the design of the car so choices like altering pickup points etc are unavailable. My guess is that you gather enough information based on precedent and you order your suspension 'kit' around these numbers. So for a 'kit' to work properly we need to stipulate springrates and then the manufacturer would setup the shock valving around these. What about ride height?
I remember ordering my KW Competition kit and you fill out a question sheet. Things like intended use of car (track, rally, hillclimb etc) power, weight, corner weights etc. Do all companies cover this off? Perhaps more comprehensively I'm sure.
To digress (in context), I have a set of Moton CS that I bought unused from someone else. They have spring rates of 750/850 and I am going to want to increase these. Do I need to have the shocks sent back to have revalved?
To touch on Larry's point about setting a car up from the get go. How do you actually do this in brief terms? What comes first, chicken or egg?
Assuming you have design parameters largely preset by the design of the car so choices like altering pickup points etc are unavailable. My guess is that you gather enough information based on precedent and you order your suspension 'kit' around these numbers. So for a 'kit' to work properly we need to stipulate springrates and then the manufacturer would setup the shock valving around these. What about ride height?
I remember ordering my KW Competition kit and you fill out a question sheet. Things like intended use of car (track, rally, hillclimb etc) power, weight, corner weights etc. Do all companies cover this off? Perhaps more comprehensively I'm sure.
To digress (in context), I have a set of Moton CS that I bought unused from someone else. They have spring rates of 750/850 and I am going to want to increase these. Do I need to have the shocks sent back to have revalved?
As far as setup, you need to determine where you are racing the car most (big smooth tracks, little twisty tracks, smooth, bumpy etc) and how well designed your suspension is. No question that too stiff can sacrifice ultimate grip on smooth sweepers, but on tracks with lots of transitions, or cars with compromised geometry, stiffer springs can produce lower lap times.
For ride height, I think that it is a balance between having a lower car and the pluses (less weight transfer, better aero) and minuses (compromised geometry at the lower height, altered roll centers, reduced suspension travel) it entails vs having a higher car with exactly the opposite strengths and weaknesses. I would say that first you want to pick the spring rates, because that will be the determining factor in how low you can go, and then decide how low you want to go.
Last edited by Larry Herman; 12-21-2009 at 12:18 AM.
12-21-2009, 05:49 AM
#54
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glad to read this discussion as opposed to some of the garbage that's been on the forum lately...
I'm really thinking about what kind of goals the suspension in my next race car will shoot for...I'm doing a relatively clean sheet porsche for Thunderhill 2010
I'm really thinking about what kind of goals the suspension in my next race car will shoot for...I'm doing a relatively clean sheet porsche for Thunderhill 2010
12-21-2009, 02:22 PM
#56
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Patrick,
your question is a good one, and one that we should (and will) take some time to address. Being at work now I can't give the attention it deserves, so I'll come back to it....hopefully this evening. Suffice to say, the word 'kit' should cause some concern, as I think it does.
Just for the sake of precision and clarity, units for spring rate (stiffness) are n/m, or lb/in, for damping they are n-s/m or lb-s/in.
your question is a good one, and one that we should (and will) take some time to address. Being at work now I can't give the attention it deserves, so I'll come back to it....hopefully this evening. Suffice to say, the word 'kit' should cause some concern, as I think it does.
Just for the sake of precision and clarity, units for spring rate (stiffness) are n/m, or lb/in, for damping they are n-s/m or lb-s/in.
12-21-2009, 04:53 PM
#57
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12-21-2009, 05:15 PM
#59
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