Suspension Theory/Chat Thread

[Sirbelch]

Originally Posted by Highrev1

Personally I think its a combination of a couple thigns First-The LSD Secondly the stock front sway bar. The Lsd cause it will acutally create more understeer than without one, It will allow for more power put down also, so that is a trade off. The bar cause the front is so tightly sprung do to that large bar causing inside "wheel spin."

Ok, so I'm getting back on the throttle smoothly but quickly coming out of a corner. The car starts to push until the outside front tire is loaded enough for the LSD to kick in and send power to the outside front wheel. When that happens, the car stops pushing and accelerates off the corner in the line i intended it to take. My old GSR with an open diff would only push coming out of a corner. So how does the LSD cause understeer? Everything i ever read said an LSD would help eliminate understeer.

[Sirbelch]

Originally Posted by Highrev1

Body roll is no indication of how well or poorly a car handles. Also Stiffer is NOT better, In fact almost the opposite. Read throught the suspension sticky at the top of the page as to why :)

I'm gonna have to some what disagree with you on that one. To stiff and the car won't roll enough to transfer enough weight to the outside tires in a corner to create enough grip. To soft and there will be to much weight transfer causing the car to over whelm the outside tires causing oversteer or understeer. Race cars are very stiff. Their suspensions have just enough body roll to load the outside tires properly. A stiffer suspension forces you to carry more corner speed in order to create enought g forces to create enough body roll to load up the outside tires. Thats how you go faster with a stiffer suspension. But, like i said earlier there is a too stiff but going soft is not going to make a car handle better.

[Highrev1]

Originally Posted by Sirbelch

Ok, so I'm getting back on the throttle smoothly but quickly coming out of a corner. The car starts to push until the outside front tire is loaded enough for the LSD to kick in and send power to the outside front wheel. When that happens, the car stops pushing and accelerates off the corner in the line i intended it to take. My old GSR with an open diff would only push coming out of a corner. So how does the LSD cause understeer? Everything i ever read said an LSD would help eliminate understeer.

True an LSD can help with corner exit acceleration, but they also tend to add to "throttle induced" understeer on corner exit as well. I should have gone into more detail with my last post sorry.

"For example, Take an open Diff FWD car accelerating out of a turn. The outside tire is heavily loaded (lots of traction) and the inside tire is lightly loaded (very little traction). In this instance the outside front is using 99% of its avalible traction making the car turn. Once the driver starts adding in throttle, thanks to the open diff, the front inside ends up getting most of the power = possible inside wheel spin, the outside gets a small fraction of power, and has to split its avalible traction between cornering and accelerating.. so you get a little more push and not much acceleration.

Add in an LSD... same instance as above, inside lightly loaded, outside heavy load... except in this case, thanks to the LSD, as the driver adds in throttle, the LSD now forces a lot more of the cars power to the tire thats heavliy loaded and not much to the tire thats lightly loaded... SO, now the front outside tire loses a substantial amount of the traction it was using to make the car turn in order to use it for acceleration, and the inside tire doesnt spin... So you've reduced/eliminated inside wheel spin and increased your rate of acceleration out of turns at the cost of increasing the amount of throttle on understeer the car has...

This only gets worse as you increase the effectiveness of the front anti-roll bar. Because the anti-roll bar effectivly increases the load on the outside front and decrease it more on the inside front... which means the car is relying even MORE on that outside front tire to make the car turn, and any loss in cornering traction in favor of acceleration = more push."

[Highrev1]

Originally Posted by Sirbelch

I'm gonna have to some what disagree with you on that one. To stiff and the car won't roll enough to transfer enough weight to the outside tires in a corner to create enough grip. To soft and there will be to much weight transfer causing the car to over whelm the outside tires causing oversteer or understeer. Race cars are very stiff. Their suspensions have just enough body roll to load the outside tires properly. A stiffer suspension forces you to carry more corner speed in order to create enought g forces to create enough body roll to load up the outside tires. Thats how you go faster with a stiffer suspension. But, like i said earlier there is a too stiff but going soft is not going to make a car handle better.

THere is a balance but generally you want to run as soft of a spring you can, this also depends on your alignment def. I haven't been detailed with my answers latlely I will start again. SUch as above not saying (Throttle incduced) I am speaking more in general terms overall kinda I will be more specific from now on

From the suspension sticky
"Let me start with the higher the suspension frequency grip decreases. SO WHAT? Well this frequencey is a measure of how many cyles per minute or in a second, the car would go through and bounce up and down on springs alone. This matters greatly to you because the stiffer the suspenion is the less contact pactch will be touching the ground over rough surfaces, and if the tires in the air your not gaining traction or grip. The more grip your tires can make, the more force your putting into the car so you will need to up the resistance to body roll to keep it at an acceptable level. Race tires need a much stiffer suspension than a street tire. Cause their grip is that much higher and will cause the body to roll, losing camber and reducing grip.
In simpler terms...you want to run the softest springs you can get away with that reduces body roll to an Livable level, and has an approperate roll couple balance to give you the oversteer/understeer charateristics you want with the most grip your car can achieve."

[Sirbelch]

Originally Posted by Highrev1

This only gets worse as you increase the effectiveness of the front anti-roll bar. Because the anti-roll bar effectivly increases the load on the outside front and decrease it more on the inside front... which means the car is relying even MORE on that outside front tire to make the car turn, and any loss in cornering traction in favor of acceleration = more push."

I get what you are saying about the LSD from a physics stand point, it just doesn't match my experance with my own car or any racing seires where they have FWD cars. Maybe its my driving style.

If you increase the effectiveness of the front anti roll bar, the bar is trying to level the car out by pushing down on the outside tire of the car which causes the outside of the car to come up, which in turn, causes the inside of the car to go down, which in turn, causes the inside tire to get pushed down. This would increase the grip of the inside tire allowing more power to go to that inside tire which takes away some of the burden of the outside tire which is tring to turn and accelerate the car. So this should allow for more power to be put down with less understeer when coming out of a corner.

[Sirbelch]

Originally Posted by Highrev1

In simpler terms...you want to run the softest springs you can get away with that reduces body roll to an Livable level, and has an approperate roll couple balance to give you the oversteer/understeer charateristics you want with the most grip your car can achieve."

So we just said the same thing in our own words. Great minds think alike.

[Highrev1]

Originally Posted by Sirbelch

I get what you are saying about the LSD from a physics stand point, it just doesn't match my experance with my own car or any racing seires where they have FWD cars. Maybe its my driving style.

If you increase the effectiveness of the front anti roll bar, the bar is trying to level the car out by pushing down on the outside tire of the car which causes the outside of the car to come up, which in turn, causes the inside of the car to go down, which in turn, causes the inside tire to get pushed down. This would increase the grip of the inside tire allowing more power to go to that inside tire which takes away some of the burden of the outside tire which is tring to turn and accelerate the car. So this should allow for more power to be put down with less understeer when coming out of a corner.

I have raced with the stock LSD...IMO and my CO-drivers ITS GARBAGE. Just my and my co-drivers opinion. I am ordering a different one

"1. your tieing both rear suspensions together, makeing them act more like a solid rear axel.

and

2. when the car leans, the anti-roll bar pushes up on the inside wheel compressing the inside wheels spring a bit (thats where it gets the extra force to resist body roll) How well the bar resists twisting determins how much force it has to compress the inside spring.

they also artificially increase the amount of load on the outside tire. which, given the way tires make traction, means that there is a Net reduction in the total amount of traction that end of the car can make (the end with the anti-roll bar). So... in some cases, it may be advantagious to reduce the effectiveness of an antiroll bar. Such as on the front of a FWD car.

As weight is increased on a tire that tire generates a greater amount of traction, HOWEVER, that tires coeffecent of friction decreases as weight is applied. Meaning traction increases at a decreasing rate as weight is applied, so there will be a point where the amount of traction gained is less then the amount of weight on the tire, and the tire slips.

This also means that a tire will gain traction at a slower rate as weight is applied then it will lose traction as weight is removed.

Meaning, weight transfer = an overall reduction in the amount of traction a car can make.... Sad way to think about it is that as your car sits in its parking spot, that is the most traction that its going to make."

Excellent discussion!! Can't give u any more +rep :)

[Sirbelch]

Originally Posted by Highrev1

Meaning, weight transfer = an overall reduction in the amount of traction a car can make:)

So, if weight transfer = an overall reduction in the amount of traction a car can make, wouldn't reducing weight trasfer though stiffer springs, dampers, anti roll bars increase the level of grip a car has? Or would it not increase grip but increase the amount of speed the car can maintain in a corner at that level of grip? i.e. the same number of g's but a higher speed (if that is even possible.)

I'd give you rep to but i cant either.

[Sirbelch]

I'm not trying to disprove everything you say, i'm just trying to get a better understanding of the black art of suspension tuning through a great point counter point discussion.

[Highrev1]

Originally Posted by Sirbelch

So, if weight transfer = an overall reduction in the amount of traction a car can make, wouldn't reducing weight trasfer though stiffer springs, dampers, anti roll bars increase the level of grip a car has? Or would it not increase grip but increase the amount of speed the car can maintain in a corner at that level of grip? i.e. the same number of g's but a higher speed (if that is even possible.)

I'd give you rep to but i cant either.

NO NO Nothing Negative here :) I enjoy this, I have been bored for weeks now.

Check out http://www.turnfast.com/index.shtml Sure its more for basice racing theories and strategies but the books they have listed are great.

"Its a matter of do you stand to gain more by increasing the potential traction of the front end by reducing lateral load transfer with running a soft or no front anti rollbar, Vs what traction you gain by having low suspension frequencys due to low spring rates.

and the answer to that would be, How rough of a Road/Track are you running on and how much static negitive camber can you run. Given that smoother track/streets will allow you to get away with stiffer springs, where rough tracks will require you to run soft springs. and static camber settings will help determin how much chassis roll is acceptible.

So, given a rough road (requireing soft springs) on a car with low amounts of static camber then Yes, you probably will gain more by stabilizing the tires contact patchs by running a stiff front bar. You'll see this alot in the stock Autox classes. Alternatly, in the same instance but with increased static camber, you could afford to run a softer front bar and ultimatly have a higher amount of potential traction because you are reducing the lateral load transfer accross the nose.

its all about comprimise on a FWD setup.

BTW, it doesnt just hurt putting power down. Increasing lateral load transfer actually reduces the potential traction that end of the car can make in any particular part of the turn. It deals with how tires make traction and the non-liniar function of Weight Vs traction. Basically as weight is applied to a tire the amount of traction it creates increases, but at a decreasing rate. This is due to the tire compounds Coefficient of friction decreasing as weight increases. So, given that relationship, as weight is transfered in a turn, the outside tire will have an increase in traction slower then the inside tire will have a decrease in traction. Resulting in an overall reduction in traction.

The nose of these cars will allways be the limiting factor in the amount of traction you can make in a turn, so any thing that can be done to maximize the potential traction should be done."

[Sirbelch]

Man, why did you have to give me homework. I hate homework.

[Highrev1]

The biggest bit of homework I could give is go to 5-10 Atuox's. You WILL bring your car to its maximum handling potential and then understand more things about the car and what you really want to change in order to make you faster. A well setup race/autox car is almost scary on the street, and its definetly a challenge in inciment weather.
I will tell you every winter I learn more about my car...I make sure I go out and drive around in the snow before they plow, it helps bring me back to basics, Brake in a straight line, gas at apex, etc. Its all about know what the car while its at its limits then the driver adjusting for it.

Start reading then start There is alot to take into account when your dealing with this black art.

I am out for the night LATER

[Sirbelch]

Uhhhhhh it doesn't snow in this part of California. But i did spend 10 minutes in my GSR in a snow coverd parking lot on a snowboarding trip spining my car in all sorts of ways. I learned sooooooooo much about car control in that 10 minutes. I need a helmet and then i can start auto x. This is my DD so all the suspention parts i get are adjustable so i can run what i brung and still be able to get it home. I'm not looking for a national auto x championship, just some good fun in a car that mostly does what i want it to.

[Andrei'sCivic]

Originally Posted by bossman

If you just installed a stut tower bar( if that is what you mean) then his car would still roll,all a tower bar does is stiffen up the front between the left and right side,kinda like a sway bar for chassis flex..I would have to say just about any old vehicle with leaf springs is a beast to try an handle..predictably.

When I installed the front upper strut bar on my dads 2003 Nissan Sentra XE and when I installed the Carbing front upper strut bar the front of the car felt really rigid/ responsive. Less Chassis flex, huh... His car still had a lot of that as well. But since I didn't drive my friends Corolla before the instalation I didn't get the full "image".

[Andrei'sCivic]

Originally Posted by Highrev1

Body roll is no indication of how well or poorly a car handles. Also Stiffer is NOT better, In fact almost the opposite. Read throught the suspension sticky at the top of the page as to why :)

I know you want soft springs and appropriatly tuned dampners, so that you don't bounce when you hit an imperfection in the road or compromise your comfort. But my friends Corolla needs better dampners. But they don't quite need replacing. I pushed down hard on his front corner of his car, his car too easily moves up and down. It continues to move up and down almost twice after you stop pushing dwnward on a specific corner. His car needs new dampners- definetly, stiffer springs cause his shit is just plain too soft (not that much stiffer than stock) Like I said stock spring rates on his Corolla are: 150lbs./in up front and 130lbs./in in the rear. He also needs larger slid sway bars, a rear lower tie bar and whatever is available for his suspension/chassis. Drive a 2000 Toyota Corolla base trim level and you will see what I mean.
-I know that Tein rebuilds there own dampners upon request but if they only sell springs for a certain application then will they rebuild the stock dampners? I emailed them this question and am waiting for there response.

[Highrev1]

"Chasses braces dont really alter the way the car handles much, What they do is remove the variable of chassis flex from the tuning equation, allowing the car to be more precicely tuned. And this is the important aspect from a compitition stand point. As being able to finely tune the chassis = better lap times. But in most cases your talking about a few tenths. So on a street car this really doesnt apply, as with out a timeing system your never going to notice if you were a tenth of a second faster in a given turn.DON"T WASTE YOUR MONEY.

[exhaust_note]

Originally Posted by Highrev1

The biggest bit of homework I could give is go to 5-10 Atuox's. You WILL bring your car to its maximum handling potential and then understand more things about the car and what you really want to change in order to make you faster. A well setup race/autox car is almost scary on the street, and its definetly a challenge in inciment weather.
I will tell you every winter I learn more about my car...I make sure I go out and drive around in the snow before they plow, it helps bring me back to basics, Brake in a straight line, gas at apex, etc. Its all about know what the car while its at its limits then the driver adjusting for it.

Start reading then start There is alot to take into account when your dealing with this black art.

I am out for the night LATER

my man know whats he's talking about. people should listen to this type of person.

ive done a few autoX's and i have a track day next weekend.

i have comptech springs and i know thats not enough. im just waiting and waiting for Koni's for be release because they will make a world of difference. ive had coilovers before and are pointless for a daily driven car. ill find out this comming weekend how the car handles with just springs and tire upgrade to determine w/ mods are needs.