Modifying your suspension - how does it change your car?
10-14-2010, 02:11 PM
#31
Race Director
Nice Larry,
Does your later information include the impact of an LSD on handling? I know that many of our customers go into the purchase of an LSD having no idea that it's going to change the handling of the vehicle and that they may need to make new suspension adjustments to the car and new behaviour adjustments to the driver to put the LSD to full use.
Does your later information include the impact of an LSD on handling? I know that many of our customers go into the purchase of an LSD having no idea that it's going to change the handling of the vehicle and that they may need to make new suspension adjustments to the car and new behaviour adjustments to the driver to put the LSD to full use.
10-14-2010, 03:04 PM
#32
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Nice Larry,
Does your later information include the impact of an LSD on handling? I know that many of our customers go into the purchase of an LSD having no idea that it's going to change the handling of the vehicle and that they may need to make new suspension adjustments to the car and new behaviour adjustments to the driver to put the LSD to full use.
Does your later information include the impact of an LSD on handling? I know that many of our customers go into the purchase of an LSD having no idea that it's going to change the handling of the vehicle and that they may need to make new suspension adjustments to the car and new behaviour adjustments to the driver to put the LSD to full use.
Anyway it has been my experience that a typical clutch type LSD will create more understeer under both acceleration and deceleration. The greater the lockup ratios, the greater the understeer. Under acceleration, adding power to the inside wheel the way a clutch type LSD does will tend to try and drive the car straighter. You can compensate for this by increasing the roll rate at the back of the car. Where the LSD is even more beneficial, unbeknownst to many, is under braking and corner entry, where the LSD forces the outside wheel to turn slower than it wants to, effectively straightening the car. This allows you to brake much farther into the corner and/or carry more off-throttle speed towards the apex. This will help corner entry as well as mid-corner speed.
For comparison I did have a Quaife type LSD in my old Carrera, and though it was much better than the open rear at putting down the power without any added understeer, it was of no effect under braking.
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Larry Herman
2016 Ford Transit Connect Titanium LWB
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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.
10-14-2010, 05:35 PM
#33
Three Wheelin'
There is a very good article from Taylor Race Engineering about differentials, their respective strengths and weaknesses, and the tuning compromises involved.http://www.taylor-race.com/pdf/under...ferentials.pdf
11-02-2010, 08:56 AM
#34
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larry i am relatively new at this so please excuse the simplicity of my querstion. lets say one makes a change to their car (stiffer back springs) that makes the back end stiffer and everything else is kept constant . based on you graph above it would seem that at any particular slip angle more load can be generated or handled by the back end . however,i am also told that the stiffer back end would tend towards more oversteer .this seems like a contradiction to me . can you explain . thanks
11-02-2010, 11:37 AM
#35
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larry i am relatively new at this so please excuse the simplicity of my querstion. lets say one makes a change to their car (stiffer back springs) that makes the back end stiffer and everything else is kept constant . based on you graph above it would seem that at any particular slip angle more load can be generated or handled by the back end .
however,i am also told that the stiffer back end would tend towards more oversteer .this seems like a contradiction to me . can you explain . thanks
11-02-2010, 03:27 PM
#36
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The stiffest corner loses traction first as it reaches tire saturation sooner.
"Chassis Engineering: by Herb Adams, any of Carroll Smith's books on handling, Fred Puhn's "How to Make Your Car Handle" are all good references to learn basic vehicle dynamics/physics which apply to all cars.
"Chassis Engineering: by Herb Adams, any of Carroll Smith's books on handling, Fred Puhn's "How to Make Your Car Handle" are all good references to learn basic vehicle dynamics/physics which apply to all cars.
11-02-2010, 03:31 PM
#37
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11-02-2010, 08:37 PM
#38
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The 'stiffer' end of the car will see a greater percentage of the total lateral load transfer; an unevenly loaded pair of tires (across an axle) will have less grip than an evenly loaded one, due to the load sensitivity of the coefficient of friction of tires (this has been attributed to tire heating, but the jury is still out). Same principle that ARBs work on. As always, much of this is so general it's almost dangerous....
Stiffer springs can actually help a car gain grip if there is a suspension geometry issue at that end of the car, by reducing suspension movement. They (stiffer springs) also increase the rate of heat input to the tires, as do digressively valved shocks.
Stiffer springs can actually help a car gain grip if there is a suspension geometry issue at that end of the car, by reducing suspension movement. They (stiffer springs) also increase the rate of heat input to the tires, as do digressively valved shocks.
11-02-2010, 09:22 PM
#39
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Sorry that I did not get back to you sooner. After writing the article I kind of ran out of room. Maybe a 3rd one is in order to discuss items like that.
Anyway it has been my experience that a typical clutch type LSD will create more understeer under both acceleration and deceleration. The greater the lockup ratios, the greater the understeer. Under acceleration, adding power to the inside wheel the way a clutch type LSD does will tend to try and drive the car straighter. You can compensate for this by increasing the roll rate at the back of the car. Where the LSD is even more beneficial, unbeknownst to many, is under braking and corner entry, where the LSD forces the outside wheel to turn slower than it wants to, effectively straightening the car. This allows you to brake much farther into the corner and/or carry more off-throttle speed towards the apex. This will help corner entry as well as mid-corner speed.
For comparison I did have a Quaife type LSD in my old Carrera, and though it was much better than the open rear at putting down the power without any added understeer, it was of no effect under braking.
Anyway it has been my experience that a typical clutch type LSD will create more understeer under both acceleration and deceleration. The greater the lockup ratios, the greater the understeer. Under acceleration, adding power to the inside wheel the way a clutch type LSD does will tend to try and drive the car straighter. You can compensate for this by increasing the roll rate at the back of the car. Where the LSD is even more beneficial, unbeknownst to many, is under braking and corner entry, where the LSD forces the outside wheel to turn slower than it wants to, effectively straightening the car. This allows you to brake much farther into the corner and/or carry more off-throttle speed towards the apex. This will help corner entry as well as mid-corner speed.
For comparison I did have a Quaife type LSD in my old Carrera, and though it was much better than the open rear at putting down the power without any added understeer, it was of no effect under braking.
.Really liked the article(s) Larry, thx for posting.
And as someone else mentioned here, Fred Puhn's book is great reading.