Billy Johnson on rear stiff setup heheh
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From: montreal, qc, Canada
Re: Billy Johnson on rear stiff setup heheh
Rear was non-stock sway-bar, a huge one but i don't remember the exact size.
----
Here's some info that we received from them on March, 2009 regarding RSX setup:
Our suspension settings will be different since we use a different tire and were limited to a max 3degrees of camber. Also our ride height is 3.5" were CTCC is 3". Also we were allowed no aero, only oem style body pieces.
Here is a base line set up you can start with.
800lb front spring
2500lb rear spring
Front alignment -3 camber(you may want to go higher) 1/4inch toe out
Rear alignment -1.5 camber 1/8inch toe out
Shocks front LS comp 2, HS comp 5, Reb 8, canister 180psi
Shocks rear comp 10, reb 5, canister 240psi
Start your rear tire preasure (cold) 5psi higher in the rear. (Mosport try 3psi)
Last edited by djphoebus; Mar 7, 2012 at 03:07 AM.
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From: mars
Re: Billy Johnson on rear stiff setup heheh
That was not .RJ. If I remember correctly he didn't even have an ITR back then? It was Warren **** in his H2 ITR that you were pushing around.
It was my street CW ITR with stock unopened engine, bolt-on's and full interior. It's been too long I'm trying to remember the suspension specs. It was F18K R12K, 225/50-15 front and 205/50-15 rear. It was a fun fast car!
It was my street CW ITR with stock unopened engine, bolt-on's and full interior. It's been too long I'm trying to remember the suspension specs. It was F18K R12K, 225/50-15 front and 205/50-15 rear. It was a fun fast car!
epic fail on my memory. i'm old. :-( but i remember .rj was really angry about that pass for some reason. i remember arguing/debating with him about that very incident... hmm. i just remember we smoked the entire field. haha. ahh well, it was 9 freaking years ago... 2003. wow.
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From: Cogito ergo sum, Canada
Re: Billy Johnson on rear stiff setup heheh
I don't think you are going to be getting any tire data from any tire manufacturer about any of its sensitivities or stiffnesses anytime soon, nor any slip angle charts or camber charts or any other relevant data, unless you pay yourself and take some tires to the Calspan facility or similar.
http://www.millikenresearch.com/TTC_SAE_paper.pdf
So we can talk about slip angle all day, but we have no data to use. Nor are we installing any sets of multiple yaw sensors on the car to know the car's attitude angle as we tune it. Maybe some factory sponsored teams in Europe can afford that, as in WTCC and such, but in Grand-Am ST class Billy was writing about, I am guessing the tuning is done much more simply using what we on this forum have available. First would be the mass of the car, which is rules limited, so zero options there. Then there is the CoG location, and for a FWD car you want to get it as far back as possible to get the rear tires to work more and the front tires to work less. But with the gearbox and engine over the front axle, about the only heavy things you can move backward are the driver, battery and cage. Next things to consider are the moments of inertia. Unless you are designing the car from scratch, and can control the location of the masses, the moments of inertia are a limited tuning tool, and they are very hard to measure. It is hard enough trying to get the height of the CoG accurately by lifting up one end of the car having blocked the suspension and trying to not have the car fall off the scales. You can think you can get the moment of inertia from simple calculations, but what do you know about the weight of the shell at various points around the car? Only thing you can know accurately are the corner weights, and the vertical CoG location within an inch or two. So that is about all you can do with the static masses of the car, and since the tires are mandated, the only thing you can do to reduce the moment of inertia in yaw is to use lighter weight wheels or brakes. But since mass and power are regulated, all cars have the same energy to dissipate with the brakes, making brake disc weight pretty close between cars, unless some car has lower drag and then it will need bigger brakes.
Then you get to the suspension, which one assumes retains stock geometry more or less. So you can tune the ride height overall, and the rake. Ride height is limited by rules typically, limiting how low you can go. So you can tune the rake a bit to vary the roll stiffness as the moment arm length changes on one axle versus the other, but the higher you put one end, the more overall weight transfer you get, and that is bad as you want weight transfer overall as low as possible. Then you can tune the roll stiffness and suspension frequencies by changing springs and bars only, as you have very little option in tuning the masses. If you can change some of the bushings, you can limit suspension movement under load due to soft bushings deflecting. If you can change some of the arm lengths, you can change static alignment and dynamic alignment. Static camber, caster, toe and how they vary with roll and pitch will change how the tire reacts and heats up or not. And then there are tire pressures to tune response, but you still want to optimize the contact patch and have the whole tire working as much as possible, so extreme pressures are not a good choice. Leaving the dampers, as those are the hardest to tune and know what to do with. Nothing is easier than swapping out a spring or changing a roll bar or its arm length. But tuning dampers is first done with ***** if you have some, and then with re-valving, and of course the choice of damper in the first place. It seems that for years most pro teams have opted for Moton, JRZ, Penske and Koni's high end dampers.
What else can you tune?
http://www.millikenresearch.com/TTC_SAE_paper.pdf
So we can talk about slip angle all day, but we have no data to use. Nor are we installing any sets of multiple yaw sensors on the car to know the car's attitude angle as we tune it. Maybe some factory sponsored teams in Europe can afford that, as in WTCC and such, but in Grand-Am ST class Billy was writing about, I am guessing the tuning is done much more simply using what we on this forum have available. First would be the mass of the car, which is rules limited, so zero options there. Then there is the CoG location, and for a FWD car you want to get it as far back as possible to get the rear tires to work more and the front tires to work less. But with the gearbox and engine over the front axle, about the only heavy things you can move backward are the driver, battery and cage. Next things to consider are the moments of inertia. Unless you are designing the car from scratch, and can control the location of the masses, the moments of inertia are a limited tuning tool, and they are very hard to measure. It is hard enough trying to get the height of the CoG accurately by lifting up one end of the car having blocked the suspension and trying to not have the car fall off the scales. You can think you can get the moment of inertia from simple calculations, but what do you know about the weight of the shell at various points around the car? Only thing you can know accurately are the corner weights, and the vertical CoG location within an inch or two. So that is about all you can do with the static masses of the car, and since the tires are mandated, the only thing you can do to reduce the moment of inertia in yaw is to use lighter weight wheels or brakes. But since mass and power are regulated, all cars have the same energy to dissipate with the brakes, making brake disc weight pretty close between cars, unless some car has lower drag and then it will need bigger brakes.
Then you get to the suspension, which one assumes retains stock geometry more or less. So you can tune the ride height overall, and the rake. Ride height is limited by rules typically, limiting how low you can go. So you can tune the rake a bit to vary the roll stiffness as the moment arm length changes on one axle versus the other, but the higher you put one end, the more overall weight transfer you get, and that is bad as you want weight transfer overall as low as possible. Then you can tune the roll stiffness and suspension frequencies by changing springs and bars only, as you have very little option in tuning the masses. If you can change some of the bushings, you can limit suspension movement under load due to soft bushings deflecting. If you can change some of the arm lengths, you can change static alignment and dynamic alignment. Static camber, caster, toe and how they vary with roll and pitch will change how the tire reacts and heats up or not. And then there are tire pressures to tune response, but you still want to optimize the contact patch and have the whole tire working as much as possible, so extreme pressures are not a good choice. Leaving the dampers, as those are the hardest to tune and know what to do with. Nothing is easier than swapping out a spring or changing a roll bar or its arm length. But tuning dampers is first done with ***** if you have some, and then with re-valving, and of course the choice of damper in the first place. It seems that for years most pro teams have opted for Moton, JRZ, Penske and Koni's high end dampers.
What else can you tune?
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From: mars
Re: Billy Johnson on rear stiff setup heheh
Just because I quoted your post, doesn't mean I was pointing the finger only at you. What I read from what Billy wrote was that the looseness he was describing from the high spring rates was due to skating - a phenomena directly related to the rapid variation in tire contact patch forces (i.e. the spring-rate effect in reducing mechanical grip). On the other hand, Billy didn't refer to any of the other ways to loosen a car which are directly related to spring rates.
For example, another way to loosen a car is by load transfer due to roll-stiffness distribution (F to R). This is fundamentally a different physical and material process than skating looseness. Load transfer looseness is both a slip angle effect as well as a tire load sensitivity (i.e. increasing grip at a decreasing rate with an increase in tire vertical (or normal) force. Thus, the tire and it's composition would need to be considered here. For example, the lateral grip vs. slip angle, the lateral grip verse vertical load on each tire, and these would need to be known at the dynamic camber angles of each tire. So the suspension's kinematics (static and dynamic) and tire properties, and not just physics are heavily involved in any discussion of oversteer/understeer balance.
Other tire properties which also are linked certainly include the particular tire's temperature sweet spot. If the fronts can be managed properly, then there can be a tendency toward oversteer balance because you are keeping the fronts in the high-grip sweet spot longer in corner and the rears might be in lower or even higher temperature range depending on setup and driver style. So this factor can't be ignored. Stiffer setups (springs/dampers) can lead to higher transient tire temps thanks to faster slip angle loading and the associated tire material property of hysteresis. If the tire has less hysteresis, than the tire temps will not build as fast and this will certainly affect the transient handling oversteer/understeer balance.
So Claude, I wasn't singling you out, I just wanted to state that no one can draw any conclusions about what Billy said strictly by reading what he wrote for that article. Sorry if you thought I was attacking you.
For example, another way to loosen a car is by load transfer due to roll-stiffness distribution (F to R). This is fundamentally a different physical and material process than skating looseness. Load transfer looseness is both a slip angle effect as well as a tire load sensitivity (i.e. increasing grip at a decreasing rate with an increase in tire vertical (or normal) force. Thus, the tire and it's composition would need to be considered here. For example, the lateral grip vs. slip angle, the lateral grip verse vertical load on each tire, and these would need to be known at the dynamic camber angles of each tire. So the suspension's kinematics (static and dynamic) and tire properties, and not just physics are heavily involved in any discussion of oversteer/understeer balance.
Other tire properties which also are linked certainly include the particular tire's temperature sweet spot. If the fronts can be managed properly, then there can be a tendency toward oversteer balance because you are keeping the fronts in the high-grip sweet spot longer in corner and the rears might be in lower or even higher temperature range depending on setup and driver style. So this factor can't be ignored. Stiffer setups (springs/dampers) can lead to higher transient tire temps thanks to faster slip angle loading and the associated tire material property of hysteresis. If the tire has less hysteresis, than the tire temps will not build as fast and this will certainly affect the transient handling oversteer/understeer balance.
So Claude, I wasn't singling you out, I just wanted to state that no one can draw any conclusions about what Billy said strictly by reading what he wrote for that article. Sorry if you thought I was attacking you.
i posted a question to billy on the nsx forum asking him to clarify what he meant by "new technologies". i think i'll just send him an email and maybe he will post a follow up.
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Re: Billy Johnson on rear stiff setup heheh
The really thing I would be curious about with some of these different setups, which was mentioned earlier, are the ride frequencies. You have to take into account weight distribution when you throw around spring rates as well. Frequencies take this all into account. Also, the tire impacts your overall frequency as well. If you were to calculate using weight transfer what the front and rear spring rates (or their ratio) were to be for a neutral balanced car... you would get front spring rates about 1.5x higher than the rear spring rates... maybe more. I know there is alot not considered using this method (the toe and camber curves, travel, etc.) but some baseline numbers from the different setups would be great to use to throw into spreadsheets. 2.2-2.5Hz, more?
/end ramblings
/end ramblings
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From: mars
Re: Billy Johnson on rear stiff setup heheh
FD2 chassis can be considered "new technology"... i happen to be watching this video earlier... and it makes me want to move n1's fd2 project up ahead in schedule... anyone have first hand experience with fd2 chassis vs. eg/dc? comments?
http://www.youtube.com/watch?v=ndaUTJUEzDg
http://www.youtube.com/watch?v=ndaUTJUEzDg
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From: Cerritos, CA, USA
Re: Billy Johnson on rear stiff setup heheh
I don't think you are going to be getting any tire data from any tire manufacturer about any of its sensitivities or stiffnesses anytime soon, nor any slip angle charts or camber charts or any other relevant data, unless you pay yourself and take some tires to the Calspan facility or similar.
http://www.millikenresearch.com/TTC_SAE_paper.pdf
So we can talk about slip angle all day, but we have no data to use. Nor are we installing any sets of multiple yaw sensors on the car to know the car's attitude angle as we tune it. Maybe some factory sponsored teams in Europe can afford that, as in WTCC and such, but in Grand-Am ST class Billy was writing about, I am guessing the tuning is done much more simply using what we on this forum have available. First would be the mass of the car, which is rules limited, so zero options there. Then there is the CoG location, and for a FWD car you want to get it as far back as possible to get the rear tires to work more and the front tires to work less. But with the gearbox and engine over the front axle, about the only heavy things you can move backward are the driver, battery and cage. Next things to consider are the moments of inertia. Unless you are designing the car from scratch, and can control the location of the masses, the moments of inertia are a limited tuning tool, and they are very hard to measure. It is hard enough trying to get the height of the CoG accurately by lifting up one end of the car having blocked the suspension and trying to not have the car fall off the scales. You can think you can get the moment of inertia from simple calculations, but what do you know about the weight of the shell at various points around the car? Only thing you can know accurately are the corner weights, and the vertical CoG location within an inch or two. So that is about all you can do with the static masses of the car, and since the tires are mandated, the only thing you can do to reduce the moment of inertia in yaw is to use lighter weight wheels or brakes. But since mass and power are regulated, all cars have the same energy to dissipate with the brakes, making brake disc weight pretty close between cars, unless some car has lower drag and then it will need bigger brakes.
Then you get to the suspension, which one assumes retains stock geometry more or less. So you can tune the ride height overall, and the rake. Ride height is limited by rules typically, limiting how low you can go. So you can tune the rake a bit to vary the roll stiffness as the moment arm length changes on one axle versus the other, but the higher you put one end, the more overall weight transfer you get, and that is bad as you want weight transfer overall as low as possible. Then you can tune the roll stiffness and suspension frequencies by changing springs and bars only, as you have very little option in tuning the masses. If you can change some of the bushings, you can limit suspension movement under load due to soft bushings deflecting. If you can change some of the arm lengths, you can change static alignment and dynamic alignment. Static camber, caster, toe and how they vary with roll and pitch will change how the tire reacts and heats up or not. And then there are tire pressures to tune response, but you still want to optimize the contact patch and have the whole tire working as much as possible, so extreme pressures are not a good choice. Leaving the dampers, as those are the hardest to tune and know what to do with. Nothing is easier than swapping out a spring or changing a roll bar or its arm length. But tuning dampers is first done with ***** if you have some, and then with re-valving, and of course the choice of damper in the first place. It seems that for years most pro teams have opted for Moton, JRZ, Penske and Koni's high end dampers.
What else can you tune?
http://www.millikenresearch.com/TTC_SAE_paper.pdf
So we can talk about slip angle all day, but we have no data to use. Nor are we installing any sets of multiple yaw sensors on the car to know the car's attitude angle as we tune it. Maybe some factory sponsored teams in Europe can afford that, as in WTCC and such, but in Grand-Am ST class Billy was writing about, I am guessing the tuning is done much more simply using what we on this forum have available. First would be the mass of the car, which is rules limited, so zero options there. Then there is the CoG location, and for a FWD car you want to get it as far back as possible to get the rear tires to work more and the front tires to work less. But with the gearbox and engine over the front axle, about the only heavy things you can move backward are the driver, battery and cage. Next things to consider are the moments of inertia. Unless you are designing the car from scratch, and can control the location of the masses, the moments of inertia are a limited tuning tool, and they are very hard to measure. It is hard enough trying to get the height of the CoG accurately by lifting up one end of the car having blocked the suspension and trying to not have the car fall off the scales. You can think you can get the moment of inertia from simple calculations, but what do you know about the weight of the shell at various points around the car? Only thing you can know accurately are the corner weights, and the vertical CoG location within an inch or two. So that is about all you can do with the static masses of the car, and since the tires are mandated, the only thing you can do to reduce the moment of inertia in yaw is to use lighter weight wheels or brakes. But since mass and power are regulated, all cars have the same energy to dissipate with the brakes, making brake disc weight pretty close between cars, unless some car has lower drag and then it will need bigger brakes.
Then you get to the suspension, which one assumes retains stock geometry more or less. So you can tune the ride height overall, and the rake. Ride height is limited by rules typically, limiting how low you can go. So you can tune the rake a bit to vary the roll stiffness as the moment arm length changes on one axle versus the other, but the higher you put one end, the more overall weight transfer you get, and that is bad as you want weight transfer overall as low as possible. Then you can tune the roll stiffness and suspension frequencies by changing springs and bars only, as you have very little option in tuning the masses. If you can change some of the bushings, you can limit suspension movement under load due to soft bushings deflecting. If you can change some of the arm lengths, you can change static alignment and dynamic alignment. Static camber, caster, toe and how they vary with roll and pitch will change how the tire reacts and heats up or not. And then there are tire pressures to tune response, but you still want to optimize the contact patch and have the whole tire working as much as possible, so extreme pressures are not a good choice. Leaving the dampers, as those are the hardest to tune and know what to do with. Nothing is easier than swapping out a spring or changing a roll bar or its arm length. But tuning dampers is first done with ***** if you have some, and then with re-valving, and of course the choice of damper in the first place. It seems that for years most pro teams have opted for Moton, JRZ, Penske and Koni's high end dampers.
What else can you tune?
Making a car handle better or differently isn't about knowing the tire's mathematical performance data, but you must have some idea about how the change you made to the car will affect how the tire will now operate. If you don't know this, you will easily get lost. Sometimes, especially when you haven't ever used a particular tire before, you must go out and test to find out things like what hot pressure works best on the particular car you're working on. You are not finding out what the tire data is for this particular tire, but rather you are determining one or more of these tire performance trends that will help you optimize the tire you're using. And of course, when you are testing you should try to isolate each tire trend one at a time, because if you make more than one change (even if you thought you were only making one change) then you may have introduced more variables into the equation that will make finding your tire trend data either very difficult or impossible.
Last edited by Johnny Mac; Mar 7, 2012 at 09:17 AM.
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From: Scotts Valley, CA
Re: Billy Johnson on rear stiff setup heheh
It's nice to see the "rear stiff" myth breaking down. I am one of those drivers that like to carry more speed and a little more front load down to the apex(the opposite of flick and stab), so my cars have always had softer rears than my competitors in similar cars. Now I guess they can all stop making fun of me.
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From: Cerritos, CA, USA
Re: Billy Johnson on rear stiff setup heheh
It's nice to see the "rear stiff" myth breaking down. I am one of those drivers that like to carry more speed and a little more front load down to the apex(the opposite of flick and stab), so my cars have always had softer rears than my competitors in similar cars. Now I guess they can all stop making fun of me.
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Re: Billy Johnson on rear stiff setup heheh
Re: Billy Johnson on rear stiff setup heheh
Changing my setup from 400/500 to 500/800 made it easier to rotate the car for me.
I do not like how the car feels with higher front rates for MY setup.
I think some of these comments are a bit extreme, but yes you can accomplish the same thing with different methods. I would say you cant argue with the success of some of the FWD teams, and club racers that WIN with the typical high rear rate bias.
I do not like how the car feels with higher front rates for MY setup.
I think some of these comments are a bit extreme, but yes you can accomplish the same thing with different methods. I would say you cant argue with the success of some of the FWD teams, and club racers that WIN with the typical high rear rate bias.
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Re: Billy Johnson on rear stiff setup heheh
My CRX started life with the following frequencies Front 1.97 and rear 2.31. That was with a spring setup that most of ya'll would consider front stiff, go figure. It was also undrivable on the street so I have since dropped the rate down to 1.46 and 1.88 and my current setup would be considered rear stiff by the basic spring designation.
On my time trial car, I have run as high as 2.24 front and 3.37 rear. It worked on a hatch. (the frequencies change radically when compare to a CRX) On my ITA car I think the frequencies were 2.3 and 3.1 ( plugged in my spring rates but my unsprung weight was probably lower on the ITA car than my street CRX)
On my time trial car, I have run as high as 2.24 front and 3.37 rear. It worked on a hatch. (the frequencies change radically when compare to a CRX) On my ITA car I think the frequencies were 2.3 and 3.1 ( plugged in my spring rates but my unsprung weight was probably lower on the ITA car than my street CRX)
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From: Cogito ergo sum, Canada
Re: Billy Johnson on rear stiff setup heheh
Here is some analysis for FSAE teams with generic tire data for Avon slicks as they published their tire data on their web site. This data was used for the article. Curves for the tires in terms of slip angle and aligning torque are typical of small race tires. How they compare to R compounds is anyone's guess, but trends would be similar.
http://www.engr.colostate.edu/pts/Jo...20Modeling.pdf
You can get Michelin's FSAE tire data as they have published it on their own site, see last two links on the bottom of this page:
http://www.michelinman.com/sites/mic...challenge.page
http://www.engr.colostate.edu/pts/Jo...20Modeling.pdf
You can get Michelin's FSAE tire data as they have published it on their own site, see last two links on the bottom of this page:
http://www.michelinman.com/sites/mic...challenge.page
Last edited by descartesfool; Mar 8, 2012 at 02:09 AM.
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From: MI, USA
Re: Billy Johnson on rear stiff setup heheh
My CRX started life with the following frequencies Front 1.97 and rear 2.31. That was with a spring setup that most of ya'll would consider front stiff, go figure. It was also undrivable on the street so I have since dropped the rate down to 1.46 and 1.88 and my current setup would be considered rear stiff by the basic spring designation.
On my time trial car, I have run as high as 2.24 front and 3.37 rear. It worked on a hatch. (the frequencies change radically when compare to a CRX) On my ITA car I think the frequencies were 2.3 and 3.1 ( plugged in my spring rates but my unsprung weight was probably lower on the ITA car than my street CRX)
On my time trial car, I have run as high as 2.24 front and 3.37 rear. It worked on a hatch. (the frequencies change radically when compare to a CRX) On my ITA car I think the frequencies were 2.3 and 3.1 ( plugged in my spring rates but my unsprung weight was probably lower on the ITA car than my street CRX)
Mine looks like roughly 2.5Hz Front, 3.1Hz rear with a "front stiff" spring setup. Switches to 2.4/3.5 with "rear stiff".... so basically it's not soft in the rear at all it's still much more stiff than the front... just the rates are uneven.
Last edited by VTECIntegra9; Mar 8, 2012 at 05:40 AM. Reason: because racecar
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Re: Billy Johnson on rear stiff setup heheh
So since VTECIntegra, 914Racer and perhaps others would like the conversation to be in terms of frequencies vs spring rates, could someone give a quick overview on how we determine those frequencies? Please and thank in advance for this humble request.
Is there a way to determine the Hz or CPM of my spring without doing the "bounce" test as I don't know how to mount my spring in the car without the shocks installed.
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From: mars
Re: Billy Johnson on rear stiff setup heheh
i laugh at the frequencies... there's a direct relationship between lbs and the frequency rate. it's purely academic. i guess some ppl think they are cooler if they talk that way...
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Re: Billy Johnson on rear stiff setup heheh
Are these calculations right?
2.5Hz Front and 3.1Hz Rear that makes your F/R ratio: 1:1.24 (aka front stiff)
2.4Hz Front and 3.5Hz Rear that makes your F/R ration: 1:1.45 (aka rear stiff)
And now I go back to my original question, how did you determine your spring frequency? Calculations or the "bounce" test?
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Re: Billy Johnson on rear stiff setup heheh
Frequencies allow all of us to be on the same page. When you factor in unsprung weights, sprung weights, weigh distribution, etc, you can then communicate with each other more effectively. You can't compare spring rates on an ITA CRX an H1 Honda Challenge CRX. There will be radical differences. So if you just looked at the spring rates, you would get the wrong idea about the set up.
Lets take my current CRX setup for example. This is a street car, yet I am using DA uprights, TypeR calipers and Prelude Rotors. This setup will be heavier than someone running a Stock SI upright and brakes. My weight distribution will be different than someone not running a B series engine, with no interior. My car has a full interior, sunroof, etc. This will generate a different frequency than say a light weight EG or even EF hatch. My EF hatch has a different frequency even when running the same spring rates as my CRX or the ITA CRX. Frequencies get everyone on the same page.
Lets take my current CRX setup for example. This is a street car, yet I am using DA uprights, TypeR calipers and Prelude Rotors. This setup will be heavier than someone running a Stock SI upright and brakes. My weight distribution will be different than someone not running a B series engine, with no interior. My car has a full interior, sunroof, etc. This will generate a different frequency than say a light weight EG or even EF hatch. My EF hatch has a different frequency even when running the same spring rates as my CRX or the ITA CRX. Frequencies get everyone on the same page.
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Re: Billy Johnson on rear stiff setup heheh
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Re: Billy Johnson on rear stiff setup heheh
Re: Billy Johnson on rear stiff setup heheh
I just went through this on a buddies Locash (lotus super 7), hypercoil has a pretty good calculator on their site if you have the geometry and weights needed.
Purely academic....ok ghetto
Purely academic....ok ghetto
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Re: Billy Johnson on rear stiff setup heheh
BTW I am still over his recommendations for a reasonably sporty street car. His recommendation was 1.25 front and 1.45 rear, tune the rear to balance. So my current setup is still stiffer than what he recommended starting with and yet compared to some of you guys, the rates that would generate those numbers would be couch comfy
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From: mars
Re: Billy Johnson on rear stiff setup heheh
ultimate it is academic because all we are really interested is in setups the works for the driver. that will mean different things to different people. when a driver through trial and error figures out he likes the rear spring to be at say, 650 lbs and not 900 lbs via. data acq. or lap times, does it matter if you know or don't know what that translate to in suspension frequency?
when you talk to racers it is more straight forward to discuss rates in lbs/" or kg/mm. to talk in frequency you have to translate the rates into that...
but whatever floats your boat...
when you talk to racers it is more straight forward to discuss rates in lbs/" or kg/mm. to talk in frequency you have to translate the rates into that...
but whatever floats your boat...
Re: Billy Johnson on rear stiff setup heheh
Ok, so you posted up this info from Billy but dont want to hear whats really behind finding the proper rates to at least start with?
Do you think that some of the REAL race teams go hey Joe Smith driver this month what spring rates do you think feel the best when the car might exchange hands throughout that race to at least an additional driver?
How did these teams come to find out they needed 3000lb rears etc? Not from the driver saying hey stiffen it up from the factory because the forum guys say thats what works. The base line can be done and then the vehicle can be tested, and I know thats what they did with the laguna mustang because I watched the documentary they released on it.
Budget racers are going by feel and what they like with their cars and I get that, I do as well because I do this for fun and dont have the resources a team would. The article, and the discussion is about upper echelon teams finding ways to get the car to rotate. The conversation and the physics involved is that "secret" or "new technologies". Its important that is realized, nobody is trying to just sound smart.
Do you think that some of the REAL race teams go hey Joe Smith driver this month what spring rates do you think feel the best when the car might exchange hands throughout that race to at least an additional driver?
How did these teams come to find out they needed 3000lb rears etc? Not from the driver saying hey stiffen it up from the factory because the forum guys say thats what works. The base line can be done and then the vehicle can be tested, and I know thats what they did with the laguna mustang because I watched the documentary they released on it.
Budget racers are going by feel and what they like with their cars and I get that, I do as well because I do this for fun and dont have the resources a team would. The article, and the discussion is about upper echelon teams finding ways to get the car to rotate. The conversation and the physics involved is that "secret" or "new technologies". Its important that is realized, nobody is trying to just sound smart.
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Re: Billy Johnson on rear stiff setup heheh
Exactly. I am using these terms because I have used them in school. after I took my vehicle dynamics and vehicle structures classes (which has a drastic impact on the vehicle's dynamics through tortional stiffness, compliance, etc), it became a common way to thing of it. We could analyze any type of car and in the end calculate where stiffness needs to be added/subtracted.
Another note - spring rates are most commonly used to determine a correct bounce center and pitch center and less about cornering. The balance is the corrected, after the ride dynamics are set, with anti-roll bars.
In regards to that thread linked above IT IS NOT CORRECT! He for some reason divided the spring rate by the motion ration squared and the spring inclination angle factor... those have to be multiplied by the spring rate to determine the wheel rate. The spring would have to be mounting upright and at the center of the contact patch (on our cars type of suspension) to not have to use these. Even a .75 motion ratio makes my 1000lb rate into a 750lb rate at the wheel.
Okay I'm rambling again. Not trying to nerd it up but this isnt a thread about here racer use this springrate... it's about differences between 'front stiff' and 'rear stiff' setups. I am saying that spring rates that are more stiff in the front than the rear does not make the car's dynamics a front biased roll stiffness. You have to account for the weight and its distribution in the car.... Which led to frequencies because they take the vehicle out of the discussion and turn it into a scenario where you can compare setups accurately.
Also about the academic thing - one of my best friends is now working in vehicle suspension simulations at chrysler and he relates to all of this terminology and more that's over my head now (I used to be the 'expert' of the group in school with him)... We built a kinematics and compliance machine for our project and these terms/strategies are used widely in industry and my field - vehicle testing. Now the engine people I work with don't know squat about them and the chassis component people don't...
Why am I rambling so much in this thread? What's my point? Because racecar that's what.
Another note - spring rates are most commonly used to determine a correct bounce center and pitch center and less about cornering. The balance is the corrected, after the ride dynamics are set, with anti-roll bars.
In regards to that thread linked above IT IS NOT CORRECT! He for some reason divided the spring rate by the motion ration squared and the spring inclination angle factor... those have to be multiplied by the spring rate to determine the wheel rate. The spring would have to be mounting upright and at the center of the contact patch (on our cars type of suspension) to not have to use these. Even a .75 motion ratio makes my 1000lb rate into a 750lb rate at the wheel.
Okay I'm rambling again. Not trying to nerd it up but this isnt a thread about here racer use this springrate... it's about differences between 'front stiff' and 'rear stiff' setups. I am saying that spring rates that are more stiff in the front than the rear does not make the car's dynamics a front biased roll stiffness. You have to account for the weight and its distribution in the car.... Which led to frequencies because they take the vehicle out of the discussion and turn it into a scenario where you can compare setups accurately.
Also about the academic thing - one of my best friends is now working in vehicle suspension simulations at chrysler and he relates to all of this terminology and more that's over my head now (I used to be the 'expert' of the group in school with him)... We built a kinematics and compliance machine for our project and these terms/strategies are used widely in industry and my field - vehicle testing. Now the engine people I work with don't know squat about them and the chassis component people don't...
Why am I rambling so much in this thread? What's my point? Because racecar that's what.