To People who have bigger rear sway bar....
I love this stuff....
After reading "Competition Car Suspension" I can get a grasp on what Mark is talking about. But I don't have the experience to link the problem with the effects and the resulting solution.
I do know we are splitting hairs as Kevin's car is sooooooooo much fun to drive. Thats the whole reason I bought one myself...
Hopefully with all the evo's cropping up in the northeast in good hands we are all going to benefit.
Let me see if this makes sense...
Is part of the idea to keep more rubber down in the rear and allow more overall grip, at a potential cost to the balance of the car?
And since Macpherson strut suspension doesn't gain any camber under compression (bump), the reduction in body roll aids in keeping the outside tire at its optimum contact patch...?
After reading "Competition Car Suspension" I can get a grasp on what Mark is talking about. But I don't have the experience to link the problem with the effects and the resulting solution.
I do know we are splitting hairs as Kevin's car is sooooooooo much fun to drive. Thats the whole reason I bought one myself...
Hopefully with all the evo's cropping up in the northeast in good hands we are all going to benefit.
Let me see if this makes sense...
Is part of the idea to keep more rubber down in the rear and allow more overall grip, at a potential cost to the balance of the car?
And since Macpherson strut suspension doesn't gain any camber under compression (bump), the reduction in body roll aids in keeping the outside tire at its optimum contact patch...?
Actually, the point at the rear is that once the inside rear tire just comes off the ground, and you continue to increase cornering force, body roll increases, then inside rear comes up higher, causing the dynamic cg to get higher, causing more weight transfer that all goes to the outside front tire, causing understeer.
The point about camber under compression is exactly the other point I was making.
The point about camber under compression is exactly the other point I was making.
ahhh....I never thought of it this way. How I use to look at it is very simple, bigger rear bar lift the rear tires when decelerate and turns. Hense, less grip in the rear on one wheel. There for, better rotation into the corner. Getting out of the corner is another story, I'm still waiting for my Quaife.
We are getting awfully technical for what is a relatively simple question.
Basically what you are saying is that by stiffening the front bar, you will help keep the rear wheel on the ground. This, logically, increases the rubber that contacts the road and increases grip.
Unfortunately your logic is slightly flawed. By doing this you are also lifting up the inside front wheel as the opposite wheel comes under load, which actually reduces grip on this wheel, resulting in push. What you should be doing is actually stiffening the springs in the front which would result in less weight transfer and less dependence on the front sway. How is keeping a rear wheel on the ground and unloading a front going to help with push? – it will only make it worse.
Another note is that with the stiffer front sway the inside wheel is easier to lift on exit. This is a real problem unless you have a limited slip front diff.
If the Evo was lifting a rear wheel in a high speed turn then I would agree that you need a stiffer front. As it is the Evo usually lifts a wheel in a tight corner under heavy braking. This can actually be desirable as it can help rotate the car.
Front wheel and 4wd cars a notorious for push. I have actually heard of racers running narrower rubber in the rear, widening the front track and even running a harder compound in the rear to help deal with it.
Basically what you are saying is that by stiffening the front bar, you will help keep the rear wheel on the ground. This, logically, increases the rubber that contacts the road and increases grip.
Unfortunately your logic is slightly flawed. By doing this you are also lifting up the inside front wheel as the opposite wheel comes under load, which actually reduces grip on this wheel, resulting in push. What you should be doing is actually stiffening the springs in the front which would result in less weight transfer and less dependence on the front sway. How is keeping a rear wheel on the ground and unloading a front going to help with push? – it will only make it worse.
Another note is that with the stiffer front sway the inside wheel is easier to lift on exit. This is a real problem unless you have a limited slip front diff.
If the Evo was lifting a rear wheel in a high speed turn then I would agree that you need a stiffer front. As it is the Evo usually lifts a wheel in a tight corner under heavy braking. This can actually be desirable as it can help rotate the car.
Front wheel and 4wd cars a notorious for push. I have actually heard of racers running narrower rubber in the rear, widening the front track and even running a harder compound in the rear to help deal with it.
JTB said:"Unfortunately your logic is slightly flawed. By doing this you are also lifting up the inside front wheel as the opposite wheel comes under load, which actually reduces grip on this wheel, resulting in push. What you should be doing is actually stiffening the springs in the front which would result in less weight transfer and less dependence on the front sway. How is keeping a rear wheel on the ground and unloading a front going to help with push? – it will only make it worse."
Please go back and reread carefully and think about it. If you still don't get what I am saying, then we will agree to disagree.
Mark
Please go back and reread carefully and think about it. If you still don't get what I am saying, then we will agree to disagree.
Mark
Thanks for the "if you are too stupid to understand what I said" response
I am going to analyze the relative bits in what you said sentence by sentence.
Total weight no, partial weight transfer – yes
I am assuming that you are referring to the height of the center of gravity depending on the tilt of the car due to load and suspension compression.
This is true assuming that you don’t unload the inside front too much. By doing so you lose the grip from the inside wheel. You also load up the outside tire more, if anything rolling the tire further past the “sweeter spot of dynamic tire camber”. This is assuming that the tire is not sliding. Push anyone?
Is it also possible that the Evos front bar is adequate to take the stock suspension to its limits? Or as you put it -- “very extremes of cornering force”
This becomes mute as you unload the inside wheel and are pushing.
If I am wrong, which is definitely possible as I am still learning, please correct me.
Perhaps I am missing the point you are trying to make. I can understand how stiffening the front sway can improve handling in many situations. I just don’t think you understand the dynamics of the stock Evo. It will push more with a stiffer bar up front with his configuration.
I guess my point is that you shouldn’t try and stiffen the springs with sway bars. The push that is being encountered is a limitation of the stock suspension. If you want to solve the lift of the tire in the rear you will need stiffer springs.
I am going to analyze the relative bits in what you said sentence by sentence.
Anti roll bars(ARB) have no effect on the total amount of weight transfer that will occur during cornering
Dynamic CG height, and track width are the determining factors
A larger front ARB will cause more weight to be transferred across the front of the vehicle during cornering than the rear, hense causing understeer. This is almost always the case except when the stiffer front ARB keeps the car in a sweeter spot of the dynamic tire camber at the front, and when an inside rear tire is off the ground, which is what we are addressing here.
My theory is that you should run as large a front bar as you need to keep the inside rear tire so that it only becomes unloaded at the very extremes of cornering force.
The larger bar in the front will cause the dynamic center of gravity height to be lower at an equivalent level of cornering force, which in turn means that you should have a higher limit of cornering with the larger front bar.
If I am wrong, which is definitely possible as I am still learning, please correct me.
Perhaps I am missing the point you are trying to make. I can understand how stiffening the front sway can improve handling in many situations. I just don’t think you understand the dynamics of the stock Evo. It will push more with a stiffer bar up front with his configuration.
I guess my point is that you shouldn’t try and stiffen the springs with sway bars. The push that is being encountered is a limitation of the stock suspension. If you want to solve the lift of the tire in the rear you will need stiffer springs.
Last edited by JTB; Jan 24, 2005 at 08:48 PM.
I didn't mean to offend you, it just didn't sound like you read what I had posted. His car has JIC coilovers, and higher spring rates. As far as cg height moving with body roll, that is exactly what I was referring to. Body roll is about 70% lift on the inside, and 30% compression on the outside. That is why in virtually all race cars you see very little body roll, and in sedans, very large front anti roll bars. We shall see how it works on my SM evo, as I plan on running lots of front bar. You have a very valid assessment on tire size as I have lots of seat time in Neons, and ran a larger front tire. I am not sure yet if this is a good option with the evo, as I have just begun my setup process.
Mark
Mark
Sorry that I took offense. I understand your answer if you assumed that I didn't read your response. I actually read your response carefully and previously understood the negatives associated with raising the CG.
You are correct about the stiffness of the bars on many race cars. The idea of stiffening the front might work assuming that he also increases the size of the rear bar.
Best of luck with your project.
You are correct about the stiffness of the bars on many race cars. The idea of stiffening the front might work assuming that he also increases the size of the rear bar.
Best of luck with your project.
I'm glad that I post this up, its amazing. I read this thread over and over and trying to digest everyone's post and the reason behind their theory. What makes it interesting is NO one is wrong here!! So what should I do, bigger bar in front or not? Then I finally found what I'm looking for (hint, no one ever mention it)! Thanks JTB, Mark and everyone! All you guys are awsome! Sometime the answer can be really simple....Hope everyone see the light soon! 
Last edited by kevo; Jan 24, 2005 at 09:20 PM.
Firstly cool thread
For those of you who don't recognize Marks name maybe his nick name "The Alien" (sorry Mark) will ring a bell. As well as his national titles, he won the "Mazda Rev-it-up" Autocross both years as well. In other words he knows his stuff (obvious by his posts). JTB also make good points and they are closer than they suspect
The things to remember are that this is not a black and white issue and it won’t be cured with just anti-roll-bars. Just to focus on the Evo's glaring problem; it’s the weight distribution, at 60f/40r your mid-corner speed is going to suffer and understeer will always be a problem. That means the driver can use various tools (adjust driving technique) to minimize the problem BUT if the corner has any sustained (steady state) cornering the understeer is going to rear it's ugly head no matter how good the driver is (Mark!). This understeer can be described as the front tires at maximum lateral grip (slip angle) and the rear tires significantly below their max (properly driven). This is why it's slow at this point in the corner. Picture now a BMW M3 at the same corner and for the sake of this comparison it has the exact same tire size and type as the EVO (we know it doesn’t in real life). Except the BMW has 50/50 weight distribution. At the same sustained mid-corner phase as the EVO it is balanced with equal load on both "axles" (fr/r). Front ties at 100% REAR @ 100% = higher corner speeds due to the better balance and maximizing all tires.
So how do we fix the EVO? First realize it will never have the mid-corner speed of the BMW but don't worry it doesn’t have to be faster! We do want to optimize mid-corner speed by INCREASING front end grip but to go faster we also need to take advantage of the AWD system on the way out and the weight bias on the way in.
As we discussed above the more weight you have towards the rear (up to 50%) the higher your mid-corner speed will be but...but the more spin prone you car will be on entry! So we can be faster than the M3 from turn in to apex. We can brake later and carry more brake into the corner (yes the infamous "trail braking"). On the way out of the turn (described as when you start to unwind the wheel) we can (if you lined the car up properly with the trail brake in the turn-in the phase) progressively get into the power and put it down more efficiently than the M3. Our line (path through the corner) should minimize time spent at steady-state, which means a generally later apex that the M3. That's how a 271hp well driven EVO can beat a 333hp M3 as long as the course is not a skidpad or a bunch of connected steady state corners.
Now about mid-corner speeds. There are two ways to increase overall grip, one is easy and get you a small increase the other is much more complicated but the car is much faster after all that hard work and $$$. BTW we have talked about this all before so I apologize to all that are experiencing a sense of Deja' Vu right know
1. Easy way: reduce rear grip to balance (by putting on a bigger rear bar and/or increasing rear tire pressure reducing rear toe etc.). This will actually make your mid-corner speed slightly higher but where the speed increase comes from is how much more efficiently you can "rotate" the car on the brakes during corner entry and therefore open the wheel up sooner (therefore get on the gas sooner etc.). So yes you have slightly increase overall grip (witness the higher skidpad number over stock) but the car could be faster still…
2. Proper way: increase front grip to balance the car. Simple things; lower the front relative to the rear, widen front track (this can be overdone and increase understeer if geometry issues are not accounted for), increase spring rate (front) so we can soften the front bar and reduce lateral load transfer, increase rebound (front). More complicated things...measure bump-steer up front then fix issues and optimize alignment specs (through testing). Notice that it is all done at the front (there is nothing wrong with the back!). There is more but it requires a shock dyno or 7k shocks and a big testing budget! Obvious is moving everything to the trunk that you can and lighten the front of the car as much as possible. Never give up trying to increase front grip! And then add…
Diffs can make a huge difference as well (again the gains are a quicker turning car not a huge increase in mid-corner speed). The testing I have been lucky enough to do has shown that clutch type "one-ways" (no locking on decel) are the best. We have not yet tested the latest torsions however. Taller rear tires in the rear also trick the car into biasing more power to the back and put a little desirable rake into the car (not so center diff friendly so I wouldn't do a cross-country drive that way!). After it's all said and done you will probably end up with a bigger rear bar anyway BUT it won't need to be full stiff and you will have the ability to run a much less aggressive alignment which will give you a car that is a lot less spin prone (think slalom). To get back on topic your front bar on a fully modded car will be about half as stiff as stock...
There is no magic pill for good handling no single mod that makes it work. Its 20 different things tuned and tested to work together with the particular car/driver, those pesky laws of physics and the particular track. We created a car that turns a lot quicker (but is just as stable in transitions) that have much better overall grip and oh yea, because it turns so efficiently it doesn’t sit at steady state for long (in relative terms) so we have minimized the effect of that lousy weight distribution and used to our advantage where possible. Time to fly!
Hope this helps and I’m sure I forgot some things and goofed up others. Please point them out (like I have to ask
)
For those of you who don't recognize Marks name maybe his nick name "The Alien" (sorry Mark) will ring a bell. As well as his national titles, he won the "Mazda Rev-it-up" Autocross both years as well. In other words he knows his stuff (obvious by his posts). JTB also make good points and they are closer than they suspect
The things to remember are that this is not a black and white issue and it won’t be cured with just anti-roll-bars. Just to focus on the Evo's glaring problem; it’s the weight distribution, at 60f/40r your mid-corner speed is going to suffer and understeer will always be a problem. That means the driver can use various tools (adjust driving technique) to minimize the problem BUT if the corner has any sustained (steady state) cornering the understeer is going to rear it's ugly head no matter how good the driver is (Mark!). This understeer can be described as the front tires at maximum lateral grip (slip angle) and the rear tires significantly below their max (properly driven). This is why it's slow at this point in the corner. Picture now a BMW M3 at the same corner and for the sake of this comparison it has the exact same tire size and type as the EVO (we know it doesn’t in real life). Except the BMW has 50/50 weight distribution. At the same sustained mid-corner phase as the EVO it is balanced with equal load on both "axles" (fr/r). Front ties at 100% REAR @ 100% = higher corner speeds due to the better balance and maximizing all tires.
So how do we fix the EVO? First realize it will never have the mid-corner speed of the BMW but don't worry it doesn’t have to be faster! We do want to optimize mid-corner speed by INCREASING front end grip but to go faster we also need to take advantage of the AWD system on the way out and the weight bias on the way in.
As we discussed above the more weight you have towards the rear (up to 50%) the higher your mid-corner speed will be but...but the more spin prone you car will be on entry! So we can be faster than the M3 from turn in to apex. We can brake later and carry more brake into the corner (yes the infamous "trail braking"). On the way out of the turn (described as when you start to unwind the wheel) we can (if you lined the car up properly with the trail brake in the turn-in the phase) progressively get into the power and put it down more efficiently than the M3. Our line (path through the corner) should minimize time spent at steady-state, which means a generally later apex that the M3. That's how a 271hp well driven EVO can beat a 333hp M3 as long as the course is not a skidpad or a bunch of connected steady state corners.
Now about mid-corner speeds. There are two ways to increase overall grip, one is easy and get you a small increase the other is much more complicated but the car is much faster after all that hard work and $$$. BTW we have talked about this all before so I apologize to all that are experiencing a sense of Deja' Vu right know
1. Easy way: reduce rear grip to balance (by putting on a bigger rear bar and/or increasing rear tire pressure reducing rear toe etc.). This will actually make your mid-corner speed slightly higher but where the speed increase comes from is how much more efficiently you can "rotate" the car on the brakes during corner entry and therefore open the wheel up sooner (therefore get on the gas sooner etc.). So yes you have slightly increase overall grip (witness the higher skidpad number over stock) but the car could be faster still…
2. Proper way: increase front grip to balance the car. Simple things; lower the front relative to the rear, widen front track (this can be overdone and increase understeer if geometry issues are not accounted for), increase spring rate (front) so we can soften the front bar and reduce lateral load transfer, increase rebound (front). More complicated things...measure bump-steer up front then fix issues and optimize alignment specs (through testing). Notice that it is all done at the front (there is nothing wrong with the back!). There is more but it requires a shock dyno or 7k shocks and a big testing budget! Obvious is moving everything to the trunk that you can and lighten the front of the car as much as possible. Never give up trying to increase front grip! And then add…
Diffs can make a huge difference as well (again the gains are a quicker turning car not a huge increase in mid-corner speed). The testing I have been lucky enough to do has shown that clutch type "one-ways" (no locking on decel) are the best. We have not yet tested the latest torsions however. Taller rear tires in the rear also trick the car into biasing more power to the back and put a little desirable rake into the car (not so center diff friendly so I wouldn't do a cross-country drive that way!). After it's all said and done you will probably end up with a bigger rear bar anyway BUT it won't need to be full stiff and you will have the ability to run a much less aggressive alignment which will give you a car that is a lot less spin prone (think slalom). To get back on topic your front bar on a fully modded car will be about half as stiff as stock...
There is no magic pill for good handling no single mod that makes it work. Its 20 different things tuned and tested to work together with the particular car/driver, those pesky laws of physics and the particular track
. We created a car that turns a lot quicker (but is just as stable in transitions) that have much better overall grip and oh yea, because it turns so efficiently it doesn’t sit at steady state for long (in relative terms) so we have minimized the effect of that lousy weight distribution and used to our advantage where possible. Time to fly! Hope this helps and I’m sure I forgot some things and goofed up others. Please point them out (like I have to ask
)
Last edited by chronohunter; Jan 25, 2005 at 08:13 AM.
I hate you! I hate you! you spoiled my thread!! People are supose to think for themself
! Nice right up 
. You should make it more simple though and keep it fun by asking " Should I left foot brake or not?" 
! Nice right up . You should make it more simple though and keep it fun by asking " Should I left foot brake or not?"
Originally Posted by kevo
I hate you! I hate you! you spoiled my thread!! People are supose to think for themself! Nice right up . You should make it more simple though and keep it fun by asking " Should I left foot brake or not?"
! Nice right up . You should make it more simple though and keep it fun by asking " Should I left foot brake or not?" 
. I should have learned by now 
Saving this thread right now, for a clueless guy like me, this info is very valuable. Forget about the bars, I'm leaving them as is..... I've more important things to concentrate on. Thanks again guys!
Last edited by kevo; Jan 25, 2005 at 01:39 AM.