now i found this info on SE-R.net, so its not my own work but i felt that its a good read and some good info for people who want to understand the basics of FWD suspension tuning,
its a long read, and there will be some referances to the Nissan Sentra (B13 chassis) so in place of that...logically you could just as easily put "Civic" instead in order for the reading to make better sense.
heres the orignal link for the FULL article but i figured id proof read it first so that i can check and remove anything thats taking about modifing parts that our civics dont have and oter small stuff like that.
http://www.se-r.net/car_info/suspension_tuning.html
anyway, read, learn, and enjoy.
_________________________________________________________
Before we start we gotta have an explanation of common vehicle dynamics terms. We had better understand the common ways to describe the different aspects of vehicle dynamics before we even turn a wrench, so here we go: [http://www.ns.net/~seang/resource/steering.html]
Friction circle: This is basically a vehicles performance envelope. It's expressed in lateral G’s, accelerating and braking G’s. When graphed, the friction circle looks like an egg with the X axis lateral G’s and the Y access braking and accelerating G’s.
Understeer: This is when, at the limit of vehicle traction, the front of the car slides first before the rear. Race car drivers call this "push". This is the way that many cars come set up to behave from the factory as it is the most predictable for average drivers. The crash mode for understeer is that when the limit of adhesion is exceeded, the car will plow strait ahead off the road nose first. This is not the fast way to have your car set up but if you are a dork mode driver. When the car understeers you should regain control if you let off the gas, unless of course you run out of road first. That is what air bags are for. Even my uncoordinated evil twin sister could get that right, maybe. It is not efficient for extracting maximum lateral G’s because the car will dynamically use the front tires excessively for turning, overloading them while the rear tires basically just hold the back of the car up. Front wheel drive cars like ours tend to exhibit understeer as the final terminal mode of balance.
Oversteer: This is when, at the limit of vehicle traction, the rear of the car slides first before the front. Race car drivers call this "loose". The rest of us call this "spinning out", "spinning a s***ty", "doing a brodie" or even crashing. The final crash mode of oversteer is backwards, tail first into the woods or in the worst case spinning round and round with the driver as a helpless passenger. Since the infamous days of Ralph Nader and the Corvair, most auto manufactures avoid oversteer like the plague. Oversteer is difficult for a dork to handle because recovery requires judicious use of countersteering and throttle feathering to control; fine motor skills that only some of us can deal with. Although oversteer looks neat and macho it is really a slow way to drive except in pro-rally on the dirt which I don’t know too much about. Oversteer is slow on the pavement because hanging the tail out bleeds off a great deal of speed going through a corner. Conserving the momentum is the fast way around as turn.
Neutral: This is the fast way around a turn where all four wheels slide evenly. Since the total friction circle traction of each tire is being used, all the available grip that the tires have is being put to the ground. Racers call this "drifting". This not to be mistaken for the idiotic Japanese Option Magazine video stuff which makes a mockery of proper driving technique. Neutral is the fast way around a corner most of the time. Neutral is also the hardest handling mode to achieve for the suspension tuner.
Polar Moment of Inertia: Or PMI as we will refer to it, is a description of how a cars mass is distributed along the length of the vehicle. A car with a high PMI is like a rear engine, rear drive car like a Porsche 911 or a front engine, front wheel drive car like our beloved Civic, same thing only the poles are different, so to speak. A car with a low PMI would be a mid engine car like a Boxster. Low PMI cars have most of their mass about the middle, high PMI cars have the mass at one end or another. Low PMI cars are the easiest to get a neutral balance out of due to the balanced, centralized mass. High PMI cars like to oversteer, in the case of the 911 or understeer like our cars. To get a feel for this phenomena, hold a bowling ball in one hand and rotate it back and forth by twisting your wrist. Now get a set of dumbbells of the same weight, grab the middle of the bar and do the same thing. Bet the bowling ball wants to rotate easier right? Guess what type of car will be easier to get neutral!
Slip Angle: This is the wonderful thing that allows us to tune our cars suspensions despite the design limitations caused by the PMI. Proper manipulation of slip angle is the great equalizer and is what suspension tuning is all about. Slip angle is the difference in which a cars wheels are pointed vs the angle that the tires contact patch is placed on the road. The main thing that affects slip angle is the manipulation of the individual load placed on each wheel while cornering. This is the key for suspension tuning. A front wheel drive car has most of the weight on the front wheels. So the front wheels run at higher slip angles and develop understeer. Conversly the same for a rear wheel drive, rear engine car developing oversteer. That is also a reason why a mid engine car with equally loaded tires will be more or less neutral. Slip angles, weight distribution and PMI are the main factors in how a vehicle will handle.
Because our cars are front heavy, front tire overloaded, front wheel drive cars, does that mean that we are condemned to econobox hell for driving fun? Heck no! By design we can not change the basic layout of our cars to significantly change the PMI or weight distribution but we can sure tweek the slip angles of the tires to achieve world class handling out of our killer econo transportation units.
The easy way to tweek the slip angles are with anti-sway bars and springs. Shock absorbers, going against what people think that they do, are not really for changing the handling balance. Shocks mostly act as spring dampers and affect understeer/oversteer balance mostly only in transient (which is big word for a change from straight line travel to turning) maneuvers like initial turn-in and zig zaging around slalom cones.
Changing to heavier springs changes the slip angle differential by resisting the cars tendency to roll on the end of the car that they are installed on. The resistance of the heavier spring to compression causes more weight to be transferred to the outside wheel of the end of the car that they are installed on as the car tries to lean over in a corner. This causes that wheel to proportionally run at a higher slip angle than it normally would. If you put heavier than stock springs in the rear of your Civic while not changing the spring rate of the front, the car would tend to understeer less.
Antisway bars work in much the same way. Antisway bars are torsion bars attached to the cars chassis and are linked to the right and left control arms. Antisway bars offer resistance to independent side to side wheel movement. This is how these bars limit sway in the turns and hence their name. While limiting sway, the antisway bars also cause weight transfer to the outside wheels. By altering the diameter of the antisway bars or installing them where there were none before adds yet another chassis tuning element. If you were to increase the size of the rear antisway bar on an Civic you would be increasing the amount of weight transfer to the outside rear wheel, thus causing it to run a bigger slip angle. This would give you more oversteer.
Tire pressure also can affect the slip angle. Higher pressures reduce the slip angle and lower pressures increase it. A great deal of suspension tuning can be done for free by adjusting the tires pressure.
Alignment also has a great deal of effect on a vehicles handling balance. Caster and camber affect how a tires contact patch is positioned on the ground by compensating for a tires tendency to flex and lift the inside tread while cornering, By helping keep the tread flat, these settings can increase or decrease the available friction circle traction on an end of a car thus affecting balance. Toe in or out can affect balance also by changing how a vehicle turns in.
Here is a rough and general matrix on how different parts and adjustments of the suspension and how the adjustments can affect your cars balance. Civic’s do not have all of these factors adjustable but an Civic can be modified to have most of these items adjustable.
You might want to print this table out and put it in your toolbox.
the information below should be a table, but i couldnt figure out how to do that so it goes in the same order as the portion in " *** ***" just below this
***Suspension adjustment
Affect on vehicle balance, extreme useable adjustment limit
Symptom of TOO MUCH adjustment***
Front spring rate increase: More understeer Terminal understeer, front of car hops in corners, excess wheelspin in FWD car
Front spring rate decrease: Less understeer Too much oversteer, oversteer then understeer if spring is so soft that the car bottoms under lean, car bottom excessively with a jolting ride
Rear spring rate increase: More oversteer Too much oversteer, hop in corners, twitchy
Rear spring rate decrease: Less oversteer Car understeers, if way to soft car understeers then oversteers as car bottoms out under lean, car bottoms out excessively with a jolting ride
Front antisway bar stiffer: More understeer Terminal understeer, Lifts inside front tire off the ground which can cause massive wheelspin, also not good for most effective tire usage as inside wheel is now doing nothing
Front antisway bar softer Less understeer Oversteer
Rear antisway bar stiffer: More oversteer Big time oversteer, Can cause the inside rear tie to lift off the ground which is not two bad on a FWD car. On Classics, if this happens while trail braking into a turn, the abs can shut the brakes down which can be a bit scary
Rear antisway bar softer: Less oversteer understeer
Front tire pressure higher: Less understeer
Except with BFG R-1 tires. They will grip less and understeer more if the pressures are increased within a reasonable amount.
No traction as tire is crowned so more understeer, bad wheel spin, jarring ride, center of tires wears out
Front tire pressure lower: More understeer
Except with BFG R-1 tires. They will grip more and understeer less if the pressures are decreased within a reasonable amount.
Edges of tires wear quickly because tire is folding over, feels mushy, tires chunk because low pressure means more heat build up
Rear tire pressures higher: Less oversteer
Except with BFG R-1 tires. They will grip less and oversteer more if the pressures are increased within a reasonable amount.
No traction as tire is crowned so more oversteer, bad wheel spin on RWD cars, jarring ride, center of tire wears out
Rear tire pressures lower: More oversteer
Except with BFG R-1 tires.
They will grip more and oversteer less if the pressures are decreased within a reasonable amount.
Edges of tires wear quickly because tire is folding over and cupping upward, feels loose in back, tires chunk because low pressure means more heat build up
More negative camber on front wheels: Less understeer/ -3 degrees Poor braking, car is road crown sensitive, twitchy, tires wear out on the inside edge
Positive camber on front wheels: More understeer, a little can make the tires last a little longer Poor braking, car is road crown sensitive, twitchy, tires wear out on the outside edge You almost never want to have positive camber unless you are a dweeb.
More negative camber on rear wheels: Less oversteer, more rear grip, less breakaway warning when limit is exceeded/-3 degrees More oversteer, car feels twitchy in back, tires wear out on inside edge
More positive camber at rear :More oversteer, more forgiving at limit Car feels twichy in the back, tires wear out on outside edge
Ride height to low: rice boy style Car twitchy with unpredictable dynamics, don’t race on when you see it because they will crash, taking you out Everything that could possibly be wrong, sudden over or understeer, twichy due to bumpsteer
Toe-in front of Car: is stable while going straight. Turn in is average/1/8 inch total toe-in Car has slow twichyness under braking, feels odd, kills the outside edge of tires
Toe-in rear of car: is less likely to suddenly oversteer when throttle is lifted/1/8 inch total toe-in Weird slow rocking movement in back, feels slow but still unstable, wears the outside edge of tires
Toe-out front of car: turns in well, works pretty good in FWD cars as they tend to toe-in under load/1/4 inch total toe out Car is real twitchy under braking, car is very road crown sensitive, car wanders on straight road, kills inside edge of tires.
Toe-out rear of car: Helps the car rotate, useful on tight low speed courses and slalom events/1/8 inch total toe out Not to good for street driving, causes lift throttle oversteer, car makes violent side to side rocking motions in rear, tires wear more on insides
Positive front caster: Helps both stability, steady state cornering and turn in because the suspension will get more negative camber when the wheel is turned/ 6-7 degrees positive.
Negative caster: is not useable Can increase understeer, especially in cars with wide, low profile tires due to a non linear increase in corner weight. Increases steering effort, Civics are not easily modified to make this adjustable, FWD cars can see an increase of torque steer with excessive positive caster
its a long read, and there will be some referances to the Nissan Sentra (B13 chassis) so in place of that...logically you could just as easily put "Civic" instead in order for the reading to make better sense.
heres the orignal link for the FULL article but i figured id proof read it first so that i can check and remove anything thats taking about modifing parts that our civics dont have and oter small stuff like that.
http://www.se-r.net/car_info/suspension_tuning.html
anyway, read, learn, and enjoy.
_________________________________________________________
Before we start we gotta have an explanation of common vehicle dynamics terms. We had better understand the common ways to describe the different aspects of vehicle dynamics before we even turn a wrench, so here we go: [http://www.ns.net/~seang/resource/steering.html]
Friction circle: This is basically a vehicles performance envelope. It's expressed in lateral G’s, accelerating and braking G’s. When graphed, the friction circle looks like an egg with the X axis lateral G’s and the Y access braking and accelerating G’s.
Understeer: This is when, at the limit of vehicle traction, the front of the car slides first before the rear. Race car drivers call this "push". This is the way that many cars come set up to behave from the factory as it is the most predictable for average drivers. The crash mode for understeer is that when the limit of adhesion is exceeded, the car will plow strait ahead off the road nose first. This is not the fast way to have your car set up but if you are a dork mode driver. When the car understeers you should regain control if you let off the gas, unless of course you run out of road first. That is what air bags are for. Even my uncoordinated evil twin sister could get that right, maybe. It is not efficient for extracting maximum lateral G’s because the car will dynamically use the front tires excessively for turning, overloading them while the rear tires basically just hold the back of the car up. Front wheel drive cars like ours tend to exhibit understeer as the final terminal mode of balance.
Oversteer: This is when, at the limit of vehicle traction, the rear of the car slides first before the front. Race car drivers call this "loose". The rest of us call this "spinning out", "spinning a s***ty", "doing a brodie" or even crashing. The final crash mode of oversteer is backwards, tail first into the woods or in the worst case spinning round and round with the driver as a helpless passenger. Since the infamous days of Ralph Nader and the Corvair, most auto manufactures avoid oversteer like the plague. Oversteer is difficult for a dork to handle because recovery requires judicious use of countersteering and throttle feathering to control; fine motor skills that only some of us can deal with. Although oversteer looks neat and macho it is really a slow way to drive except in pro-rally on the dirt which I don’t know too much about. Oversteer is slow on the pavement because hanging the tail out bleeds off a great deal of speed going through a corner. Conserving the momentum is the fast way around as turn.
Neutral: This is the fast way around a turn where all four wheels slide evenly. Since the total friction circle traction of each tire is being used, all the available grip that the tires have is being put to the ground. Racers call this "drifting". This not to be mistaken for the idiotic Japanese Option Magazine video stuff which makes a mockery of proper driving technique. Neutral is the fast way around a corner most of the time. Neutral is also the hardest handling mode to achieve for the suspension tuner.
Polar Moment of Inertia: Or PMI as we will refer to it, is a description of how a cars mass is distributed along the length of the vehicle. A car with a high PMI is like a rear engine, rear drive car like a Porsche 911 or a front engine, front wheel drive car like our beloved Civic, same thing only the poles are different, so to speak. A car with a low PMI would be a mid engine car like a Boxster. Low PMI cars have most of their mass about the middle, high PMI cars have the mass at one end or another. Low PMI cars are the easiest to get a neutral balance out of due to the balanced, centralized mass. High PMI cars like to oversteer, in the case of the 911 or understeer like our cars. To get a feel for this phenomena, hold a bowling ball in one hand and rotate it back and forth by twisting your wrist. Now get a set of dumbbells of the same weight, grab the middle of the bar and do the same thing. Bet the bowling ball wants to rotate easier right? Guess what type of car will be easier to get neutral!
Slip Angle: This is the wonderful thing that allows us to tune our cars suspensions despite the design limitations caused by the PMI. Proper manipulation of slip angle is the great equalizer and is what suspension tuning is all about. Slip angle is the difference in which a cars wheels are pointed vs the angle that the tires contact patch is placed on the road. The main thing that affects slip angle is the manipulation of the individual load placed on each wheel while cornering. This is the key for suspension tuning. A front wheel drive car has most of the weight on the front wheels. So the front wheels run at higher slip angles and develop understeer. Conversly the same for a rear wheel drive, rear engine car developing oversteer. That is also a reason why a mid engine car with equally loaded tires will be more or less neutral. Slip angles, weight distribution and PMI are the main factors in how a vehicle will handle.
Because our cars are front heavy, front tire overloaded, front wheel drive cars, does that mean that we are condemned to econobox hell for driving fun? Heck no! By design we can not change the basic layout of our cars to significantly change the PMI or weight distribution but we can sure tweek the slip angles of the tires to achieve world class handling out of our killer econo transportation units.
The easy way to tweek the slip angles are with anti-sway bars and springs. Shock absorbers, going against what people think that they do, are not really for changing the handling balance. Shocks mostly act as spring dampers and affect understeer/oversteer balance mostly only in transient (which is big word for a change from straight line travel to turning) maneuvers like initial turn-in and zig zaging around slalom cones.
Changing to heavier springs changes the slip angle differential by resisting the cars tendency to roll on the end of the car that they are installed on. The resistance of the heavier spring to compression causes more weight to be transferred to the outside wheel of the end of the car that they are installed on as the car tries to lean over in a corner. This causes that wheel to proportionally run at a higher slip angle than it normally would. If you put heavier than stock springs in the rear of your Civic while not changing the spring rate of the front, the car would tend to understeer less.
Antisway bars work in much the same way. Antisway bars are torsion bars attached to the cars chassis and are linked to the right and left control arms. Antisway bars offer resistance to independent side to side wheel movement. This is how these bars limit sway in the turns and hence their name. While limiting sway, the antisway bars also cause weight transfer to the outside wheels. By altering the diameter of the antisway bars or installing them where there were none before adds yet another chassis tuning element. If you were to increase the size of the rear antisway bar on an Civic you would be increasing the amount of weight transfer to the outside rear wheel, thus causing it to run a bigger slip angle. This would give you more oversteer.
Tire pressure also can affect the slip angle. Higher pressures reduce the slip angle and lower pressures increase it. A great deal of suspension tuning can be done for free by adjusting the tires pressure.
Alignment also has a great deal of effect on a vehicles handling balance. Caster and camber affect how a tires contact patch is positioned on the ground by compensating for a tires tendency to flex and lift the inside tread while cornering, By helping keep the tread flat, these settings can increase or decrease the available friction circle traction on an end of a car thus affecting balance. Toe in or out can affect balance also by changing how a vehicle turns in.
Here is a rough and general matrix on how different parts and adjustments of the suspension and how the adjustments can affect your cars balance. Civic’s do not have all of these factors adjustable but an Civic can be modified to have most of these items adjustable.
You might want to print this table out and put it in your toolbox.
the information below should be a table, but i couldnt figure out how to do that so it goes in the same order as the portion in " *** ***" just below this
***Suspension adjustment
Affect on vehicle balance, extreme useable adjustment limit
Symptom of TOO MUCH adjustment***
Front spring rate increase: More understeer Terminal understeer, front of car hops in corners, excess wheelspin in FWD car
Front spring rate decrease: Less understeer Too much oversteer, oversteer then understeer if spring is so soft that the car bottoms under lean, car bottom excessively with a jolting ride
Rear spring rate increase: More oversteer Too much oversteer, hop in corners, twitchy
Rear spring rate decrease: Less oversteer Car understeers, if way to soft car understeers then oversteers as car bottoms out under lean, car bottoms out excessively with a jolting ride
Front antisway bar stiffer: More understeer Terminal understeer, Lifts inside front tire off the ground which can cause massive wheelspin, also not good for most effective tire usage as inside wheel is now doing nothing
Front antisway bar softer Less understeer Oversteer
Rear antisway bar stiffer: More oversteer Big time oversteer, Can cause the inside rear tie to lift off the ground which is not two bad on a FWD car. On Classics, if this happens while trail braking into a turn, the abs can shut the brakes down which can be a bit scary
Rear antisway bar softer: Less oversteer understeer
Front tire pressure higher: Less understeer
Except with BFG R-1 tires. They will grip less and understeer more if the pressures are increased within a reasonable amount.
No traction as tire is crowned so more understeer, bad wheel spin, jarring ride, center of tires wears out
Front tire pressure lower: More understeer
Except with BFG R-1 tires. They will grip more and understeer less if the pressures are decreased within a reasonable amount.
Edges of tires wear quickly because tire is folding over, feels mushy, tires chunk because low pressure means more heat build up
Rear tire pressures higher: Less oversteer
Except with BFG R-1 tires. They will grip less and oversteer more if the pressures are increased within a reasonable amount.
No traction as tire is crowned so more oversteer, bad wheel spin on RWD cars, jarring ride, center of tire wears out
Rear tire pressures lower: More oversteer
Except with BFG R-1 tires.
They will grip more and oversteer less if the pressures are decreased within a reasonable amount.
Edges of tires wear quickly because tire is folding over and cupping upward, feels loose in back, tires chunk because low pressure means more heat build up
More negative camber on front wheels: Less understeer/ -3 degrees Poor braking, car is road crown sensitive, twitchy, tires wear out on the inside edge
Positive camber on front wheels: More understeer, a little can make the tires last a little longer Poor braking, car is road crown sensitive, twitchy, tires wear out on the outside edge You almost never want to have positive camber unless you are a dweeb.
More negative camber on rear wheels: Less oversteer, more rear grip, less breakaway warning when limit is exceeded/-3 degrees More oversteer, car feels twitchy in back, tires wear out on inside edge
More positive camber at rear :More oversteer, more forgiving at limit Car feels twichy in the back, tires wear out on outside edge
Ride height to low: rice boy style Car twitchy with unpredictable dynamics, don’t race on when you see it because they will crash, taking you out Everything that could possibly be wrong, sudden over or understeer, twichy due to bumpsteer
Toe-in front of Car: is stable while going straight. Turn in is average/1/8 inch total toe-in Car has slow twichyness under braking, feels odd, kills the outside edge of tires
Toe-in rear of car: is less likely to suddenly oversteer when throttle is lifted/1/8 inch total toe-in Weird slow rocking movement in back, feels slow but still unstable, wears the outside edge of tires
Toe-out front of car: turns in well, works pretty good in FWD cars as they tend to toe-in under load/1/4 inch total toe out Car is real twitchy under braking, car is very road crown sensitive, car wanders on straight road, kills inside edge of tires.
Toe-out rear of car: Helps the car rotate, useful on tight low speed courses and slalom events/1/8 inch total toe out Not to good for street driving, causes lift throttle oversteer, car makes violent side to side rocking motions in rear, tires wear more on insides
Positive front caster: Helps both stability, steady state cornering and turn in because the suspension will get more negative camber when the wheel is turned/ 6-7 degrees positive.
Negative caster: is not useable Can increase understeer, especially in cars with wide, low profile tires due to a non linear increase in corner weight. Increases steering effort, Civics are not easily modified to make this adjustable, FWD cars can see an increase of torque steer with excessive positive caster
