Suspension set up cheat sheet
12-11-2010, 03:35 PM
#106
I just now finished reading this thread after being away from Rennlist for a week (busy with work, family, etc) and all I can say is “Wow!”. There is a very informative discussion going on here. I really appreciate it when knowledgeable folks such as Larry, SundayDriver, Winders, Claykos and several others take the time to share information and opinions in a constructive manner. This discussion certainly has reminded of me how complex this stuff really is. And, it has introduced a concept that I had never really considered which is the fact that when making setup changes, an important consideration is where you are on the tire’s load curve. It sounds like if you are at or above the point where the tire’s grip falls off exponentially faster than the vertical load transfer (the “knee” of the load curve), you will proceed differently than if you were not yet at the “knee” of the load curve.
This discussion points out two more key areas that I would like to learn more about:
• Tire performance and grip – I would like to learn more about load curves and how tire grip really works.
• Roll centers – I would like to learn more about how to properly calculate the location of the front and rear roll centers and how the roll centers affect handling and chassis setup (including the possibility of changing the roll centers to change handling).
If anybody has any recommendations for books or websites that do a good job explaining the above two concepts (or further discussion in this thread to simplify the main aspects), please share. In addition, if you have any guidance regarding whether or not the various race tire manufacturers produce load curves for their tires and where I can find these load curves (or other important technical info), that would also be very helpful.
Regarding the load curves for tires, if there was some way we could install load cells on say the upper spring perch of each corner of our race cars, we could then conduct data acquisition that could really help us understand what is going on during any given corner. We could compare the loads on each corner of the car to the lateral Gs that many of us are already recording and maybe really learn something useful. Therefore, does anyone happen to know if such load cells exist and could be adapted to our race car suspensions??
Thanks,
Jeff
This discussion points out two more key areas that I would like to learn more about:
• Tire performance and grip – I would like to learn more about load curves and how tire grip really works.
• Roll centers – I would like to learn more about how to properly calculate the location of the front and rear roll centers and how the roll centers affect handling and chassis setup (including the possibility of changing the roll centers to change handling).
If anybody has any recommendations for books or websites that do a good job explaining the above two concepts (or further discussion in this thread to simplify the main aspects), please share. In addition, if you have any guidance regarding whether or not the various race tire manufacturers produce load curves for their tires and where I can find these load curves (or other important technical info), that would also be very helpful.
Regarding the load curves for tires, if there was some way we could install load cells on say the upper spring perch of each corner of our race cars, we could then conduct data acquisition that could really help us understand what is going on during any given corner. We could compare the loads on each corner of the car to the lateral Gs that many of us are already recording and maybe really learn something useful. Therefore, does anyone happen to know if such load cells exist and could be adapted to our race car suspensions??
Thanks,
Jeff
Circle track cars frequently use rear roll center adjustment to change the handling. When you hear them talking about a "track bar adjustment" in a pit stop this is what they are doing. Raising and lowering the rear roll center. Raising the roll center has the effect of stiffening that end of the car, but with some adverse effects also that would not happen by stiffening a sway bar or spring ("Jacking Forces").
As far as data acquisition, the simplest way is with shock travel sensors (linear potentiometers). If you know how much each corner is compressed/extended and you know the spring/bar rates and leverages (wheel rates) then you can back your way into the force on each tire.
12-11-2010, 03:44 PM
#107
Lifetime Rennlist Member
I just now finished reading this thread after being away from Rennlist for a week (busy with work, family, etc) and all I can say is “Wow!”. There is a very informative discussion going on here. I really appreciate it when knowledgeable folks such as Larry, SundayDriver, Winders, Claykos and several others take the time to share information and opinions in a constructive manner. This discussion certainly has reminded of me how complex this stuff really is. And, it has introduced a concept that I had never really considered which is the fact that when making setup changes, an important consideration is where you are on the tire’s load curve. It sounds like if you are at or above the point where the tire’s grip falls off exponentially faster than the vertical load transfer (the “knee” of the load curve), you will proceed differently than if you were not yet at the “knee” of the load curve.
This discussion points out two more key areas that I would like to learn more about:
• Tire performance and grip – I would like to learn more about load curves and how tire grip really works.
• Roll centers – I would like to learn more about how to properly calculate the location of the front and rear roll centers and how the roll centers affect handling and chassis setup (including the possibility of changing the roll centers to change handling).
If anybody has any recommendations for books or websites that do a good job explaining the above two concepts (or further discussion in this thread to simplify the main aspects), please share. In addition, if you have any guidance regarding whether or not the various race tire manufacturers produce load curves for their tires and where I can find these load curves (or other important technical info), that would also be very helpful.
Regarding the load curves for tires, if there was some way we could install load cells on say the upper spring perch of each corner of our race cars, we could then conduct data acquisition that could really help us understand what is going on during any given corner. We could compare the loads on each corner of the car to the lateral Gs that many of us are already recording and maybe really learn something useful. Therefore, does anyone happen to know if such load cells exist and could be adapted to our race car suspensions??
Thanks,
Jeff
This discussion points out two more key areas that I would like to learn more about:
• Tire performance and grip – I would like to learn more about load curves and how tire grip really works.
• Roll centers – I would like to learn more about how to properly calculate the location of the front and rear roll centers and how the roll centers affect handling and chassis setup (including the possibility of changing the roll centers to change handling).
If anybody has any recommendations for books or websites that do a good job explaining the above two concepts (or further discussion in this thread to simplify the main aspects), please share. In addition, if you have any guidance regarding whether or not the various race tire manufacturers produce load curves for their tires and where I can find these load curves (or other important technical info), that would also be very helpful.
Regarding the load curves for tires, if there was some way we could install load cells on say the upper spring perch of each corner of our race cars, we could then conduct data acquisition that could really help us understand what is going on during any given corner. We could compare the loads on each corner of the car to the lateral Gs that many of us are already recording and maybe really learn something useful. Therefore, does anyone happen to know if such load cells exist and could be adapted to our race car suspensions??
Thanks,
Jeff
Same book talks about tires, but I have not found a single reference that really does a good job. You need to read a lot of different stuff. Most that I have seen is wrong in one way or another, so you have to synthesize the info in a way that makes sense to you.
Milliken & Milliken is the "bible" but it is very heavy math and close to 900 pages. I also like 'Introduction to Race Car Engineering' by Rowley - that is a series of articles with some good stuff in there plus it comes with a trial copy of Wm Mitchell's WinGeo software to model suspensions.
IMO though, no book exists that explains this stuff in the manner that most club racers & serious DE folks can digest without a strong technical background.
Load Cells - All the load goes through the suspension, so what is generally done is to put strain gauges in the appropriate location. But is you have a good Data system with shock travel measurement, then you can calculate that info. I had that on my Stohr and it is pretty educational. You can see the weight transfer in corners and what happens with crests in the road and things like uphill braking.
Edit - I didn't see claykos' post when I started mine (I had to go pull some books for titles and authors) so take my post mostly as "^^What he said".
12-11-2010, 03:57 PM
#108
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Claykos and SundayDriver, thanks a bunch for your replies. I need to buy those books you recommended and do some reading . . .
In addition, the point Claykos made about using the shock travel sensors and spring rates to determine load is a great idea. It is another one of those common sense things where once I heard the suggestion, I thought to myself "why didn't I think of that??!!??"
Jeff
In addition, the point Claykos made about using the shock travel sensors and spring rates to determine load is a great idea. It is another one of those common sense things where once I heard the suggestion, I thought to myself "why didn't I think of that??!!??"
Jeff
12-11-2010, 04:01 PM
#109
Lifetime Rennlist Member
Claykos and SundayDriver, thanks a bunch for your replies. I need to buy those books you recommended and do some reading . . .
In addition, the point Claykos made about using the shock travel sensors and spring rates to determine load is a great idea. It is another one of those common sense things where once I heard the suggestion, I thought to myself "why didn't I think of that??!!??"
Jeff
In addition, the point Claykos made about using the shock travel sensors and spring rates to determine load is a great idea. It is another one of those common sense things where once I heard the suggestion, I thought to myself "why didn't I think of that??!!??"
Jeff
12-11-2010, 05:57 PM
#110
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One of the items that Mark & I have discussed was tire loading and that optimal grip can and should be above what the static weight is on the tire. My question is how you find out what the optimal tire loading is? Seems like it would be MFG proprietary information; not readily given out.
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Retired Club Racer & National PCA Instructor
Past Flames:
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CLICK HERE to see some of my ancient racing videos.
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.
12-11-2010, 10:50 PM
#112
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Fred Puhn's HTMYCH is much more useful versus Carroll Smith's Tune To Win. Puhn's a more deliberate teacher and better writer compared to Smith's wordy, indirect style.
Smith's main effort covers open wheeled cars with double wishbone suspensions. The sections defining unfamiliar terms is very good.
Worth it to own both.
Smith's main effort covers open wheeled cars with double wishbone suspensions. The sections defining unfamiliar terms is very good.
Worth it to own both.
12-12-2010, 12:55 PM
#113
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I really like the Rowley book (Introduction to Race Car Engineering), a good friend of mine was the 'mathematics editor' for the current edition. The Milliken book is the bible, but it is a little different given its aerospace/control systems approach. Once you become acquainted with that, it's a brilliant book...After all, vehicle dynamics is a control systems engineering topic (open and closed loop control of stable and unstable systems). John Dixons book Tires, Suspension, and Handling is a really good intro, BTW. By all means, read the 'Force and Moment' analysis section of Race Car Vehicle Dynamics; great stuff, and it discusses trim at the limit, and differentiates between OS and US as a function of slip angle (which occurs in the linear region of tire lateral force generation), and 'push' and 'spin' in the frictional/breakaway region of force generation.
I would avoid the Staniforth book.
I would avoid the Staniforth book.
