discussion on optimal suspension setup for drag - Racing Forum

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discussion on optimal suspension setup for drag
Friday, November 06, 2009 7:55 PM
I'm trying to get a an idea of the basic front and rear suspension setup for drag racing. so far it seems what Ive been finding is pretty straight forward. stiff rear with firmness all the way up. fronts set to soft. whole car lowered but with the rear slightly higher to shift weight towards the front. also tire pressures high in the rear and low in the front. of course all of these are general ideas with settings that need fine tuning. but do I have the genral jist of it?


"boobs now with Riboflabin"
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Re: discussion on optimal suspension setup for drag
Saturday, November 07, 2009 8:01 PM
I was just going to start a topic on this. Listening.

currently my car is like 3-4 inches higher in the rear with some really stiff springs all the way around. doesn't seem to hook any better or any worse then stock.


- Your not-so-local, untrained, uncertified, backyard mechanic. But my @!#$ runs
Re: discussion on optimal suspension setup for drag
Sunday, November 08, 2009 9:42 PM
Interested to hear what people have to say...
Re: discussion on optimal suspension setup for drag
Wednesday, November 11, 2009 2:28 AM
I'm working on a special setup with a friend of mine who is as nuts about suspension as I am about engines.

we got some spring rates off of the STD coilovers I'm putting on the skwirl, and trying some different things.


your idea about the suspension setup is pretty much dead on for a FWD car.. want to minimize weight transfer as much as possible. keep the rear stiff, and the front soft to help the car hook.

some people also use limiting straps to prevent the front end from jumping around from the torque, or traction bars to limit suspension travel in front.. not sure what this means for us just yet, but I'll be doing some testing when the skwirl hits the track next year.

i should have an interesting thread on modifying coilovers to get what you want out of them very soon. the fact that our coilover systems use 2.5" springs makes it a lot easier to play with spring rates.. but its an ongoing process so I don't have anything definitive just yet.. but I will.






Re: discussion on optimal suspension setup for drag
Wednesday, November 11, 2009 3:38 PM
The T\G drag car went with stiff rear springs (put in insolators between coils) made it go all over the place out of the hole....


Chris




'02 Z-24 Supercharged
13.7 @102.45 MPH Third Place, 2007 GMSC Bash SOLD AS OF 01MAR08

Re: discussion on optimal suspension setup for drag
Friday, November 13, 2009 8:43 PM
ive been watching susp. setups on another thread, and ive read that having the raked stance doesnt work like you think, but when you launch what happens is weight transfers and your front matches your rear, but if your front is higer slightly its the highest point of gravity and keeps more weight over the front wheels.





R.I.P. Brian Klocke, you will never be forgotten
Re: discussion on optimal suspension setup for drag
Saturday, November 14, 2009 3:26 PM
Interesting, I have also read you want to keep the center of gravity as low as possible.


- Your not-so-local, untrained, uncertified, backyard mechanic. But my @!#$ runs
Re: discussion on optimal suspension setup for drag
Saturday, November 14, 2009 5:51 PM
just get some wheelie bars for the track if you are THAT concerned about it...



I must confess... I feel like a monster!
Re: discussion on optimal suspension setup for drag
Saturday, November 14, 2009 6:39 PM
Boosted2point4 wrote:ive been watching susp. setups on another thread, and ive read that having the raked stance doesnt work like you think, but when you launch what happens is weight transfers and your front matches your rear, but if your front is higer slightly its the highest point of gravity and keeps more weight over the front wheels.


Please expain more, physics is telling me this doesn't make sense, but maybe I'm not taking everything into consideration...
Re: discussion on optimal suspension setup for drag
Saturday, November 14, 2009 6:55 PM
Actually... I may understand what you meant, I was thinking more in terms of RWD, but a FWD car wouldn't have anywhere near as much force lifting the front as it accelerates...sucks that its really hard to apply physics to this. Its pretty easy to understand that you want the centre of mass as low as possible, but its pretty damn hard to imagine how tire pressure/size/traction, and spring um... springyness/height, come into play in terms of transfering weight forward/rearward.

Anyway, I still want you to explain what you said.. I sort of understand, but not really....
















WAIT IVE GOT IT!!!!!! PUT A HUGE ASS SPOILER ON THE FRONT OF THE CAR!!!!!
Re: discussion on optimal suspension setup for drag
Saturday, November 14, 2009 7:15 PM
I think mabey hes saying raking the rear up and the front down will still make it transfer weight. So when its in the process of tranfering you lose your traction. If you already have it transfered from the start it wont have anything to transfer

Re: discussion on optimal suspension setup for drag
Saturday, November 14, 2009 8:34 PM
sorry it was later and what i said really wasnt explained too well, so ill try again.

from reading threw on other forums, the raked stance of your rwd cars doesnt play out too well on fwd because you have your rear up in the air and when launching even with stiff springs your front is going to rise which takes weight off the front, because from what i read is the front will come up and match the rears. now what ive seen is that you lower the car as much as possible and if anything the front is higher it will already be the highest point of gravity and wont be as likely as to transfer all the weight off the front tires, also heard corner balancing the car helps but the rear is not as important to than the front. fwd cars go aginst physics...lol





R.I.P. Brian Klocke, you will never be forgotten
Re: discussion on optimal suspension setup for drag
Saturday, November 14, 2009 11:55 PM
I'm not a physicist nor a suspension wiz. So that being said...

What fetter says makes sense initially, but when you get down to it, I would think the front end being higher is counterproductive (and thusly more inefficient) in a few ways.

1. Aerodynamics would blow and would create more drag on the car than you would make up on the line
2. Having our front end higher would put our axels at a more extreme angle = more broken axels
3. The car would still transfer weight backwards no matter what. That engine is essentially trying to come through the firewall at you whether its 3 degrees pitched up or down.
4. The ugly factor... that would be one weird ass car to look at.

What is happening is the front end suspension unloading, thus taking weight off the wheels that need the traction. Whether the front end is up or down, that suspension will still unload and take pressure off the wheels. So would lowering the car and having the front suspension upward travel maxed at where the car sits normally be the best option? I don't know but there are teams like GM that put millions of dollars of research into their FWD program. All the pics I see of Brian Ballard's Cobalt have the front end lower than the rear for instance.

You really don't have to get all that extreme to get the results you want from your suspension. The Sunfire was a conisitent 1.70 with an occasional 1.62 60 foot and the only suspension work was Eibach lowering springs front and rear and some old fashion spacers in the rear to stiffen it up, that's it. So to have the same setup as our car, you would spend $250 on Eibachs and $15 on the spacers from NAPA.

In all honesty, you have the basic idea, but your driving style will determine the answer for your application. How fast you release the clutch and how much throttle you have, how much power you make down low, the tire width height and compound, so on and so on. One positive aspect of that big GT40 we had on the Sunfire was it didnt hit all that hard off the line for a 700 hp FWD, and we just sprayed it in the low RPM's for 2nd, 3rd, and 4th gear to make up for that.





Street-Legal 2003 Sunfire 10.58 @ 139 MPH
Re: discussion on optimal suspension setup for drag
Sunday, November 15, 2009 2:15 PM
^^^^Very good point. I think the simple fact is that FWD just is not good no matter what. From my understanding dont "race cars" use wheelie bars to push back and keep the weight from transfering? Thats bad ass you guys dont have some crazy suspension setup. Which goes to say a driver is the biggest difference in the way a car can behave.
Re: discussion on optimal suspension setup for drag
Sunday, November 15, 2009 3:59 PM
Ugh, everytime I sit down to post something here I end up writing a physics essay, and changing my oppinion and starting over. But heres my theory, for those of you who have the patience to read it.

But I think Adam is right... sort of. I don't agree with the reasoning he gave for it (1 could be fixed with a lower bumper, 2 really is a financial drawback not a performance one, 3 makes sense, but any setup unde acceleration will do this, the question is what setup will do it the least, and 4 well, obviously that has nothing to do with performance). Regardless, I think what works for RWD cars will work for FWD. If you tihnk about it, a rwd car doing a wheelie is exactly what we are trying to prevent. However, our cars physicaly cannot do that, becaue if they tried to pivot at the front wheels the rear wheels would just press against the ground and nothing would happen. This is why we need a stiff rear, so it doesn't sink and let the front raise. Also as far height of the front and rear... well consider this:

You have a beam, it looks like this ```````^````````````````````````= (yes I know thats crappy, but the ^ is the fulcrum, and the = is a spring, the ` are where the beam is and it is resting on the srping.) Now the easiest way to compress the spring here would be to pull straight up on the front, that is pretty easy to understand. Now if the front was higher, the easiest way would be to push up and right (perpendicular to the beam). If the front was lower, you would want to push up and left to compress the spring. Now lets apply that to our cars . We DONT want to compress the rear, we want to resist the front lifting as much as possible. I magine the car is facing left, like the beam. When we accelerate the resistance is obviously pushing right. But there are several forces pushin up and down, so these all need to be considered. If the car were to be higher in the front, air would flow easily over the car, but would not flow easily under. This would cause more airpressure beneath the car, and would be taking weight off of the wheels. BUT, the lift under the car would not be appied evenely, because the suspension is not the same on both ends of the car. The softer side, would lift faster, resisting the other side from lifting aswell. So for that reason I think having the front slightly higher, would be beneficially, ONLY if the front springs were stiffer than the rear.


BUT, there are more forces at work than just airdrag. Remember what I said about our cars wanting to do a wheelie, but not physicaly capable because the rear wheels are already on the ground. I'm not sure where this would take effect, but at some point, the force of the front bumper wanting to lift over the accelerating tires (like a wheelie), is going to be much greater than airdrag. Obviously, the car cannot pivot in that way very far because it pushes the rear wheels into the ground. However, it is still taking weight off of the front wheels as it TRIES to lift them. So once this upward force is greater than the downward force of air, it becomes beneficial to lower the front to resist the upward motion. With the air resistance, the force was acting on the entire bottom of the car, so if could be directed with adjusting spring stiffness. With the wheelie force, it is only acting infront of the tires, if cannot be redirected, so it must instead be resisted as much as possible. To do this the car must be lowered in the front, the greater the upward force, the more the car must be angled. Idealy you want the car pointing directly into the force, but it would be extremely difficult to determine that exact angle. Stiffer rear springs would help resist that force even more.

The air pushing up on the entire bottom of the car, could be redirected to the rear by having stiffer front springs. Pushing up on the back, pushes down on the front, like a seesaw. But at some point that redirected force will not overcome the lift on the nose of the car causes by the bumper wanting to lift over the front wheels. How much power your car needs before that happens, I don't know. But I doubt it is very much, for our cars stock, it MAY be beneficial to have a higher front with softer rear springs, but any decent amount of power, and I would think the opposite is a better set up.

PS: I'm not a drag expert, I've never even been to a drag strip, I'm looking at this only from a physics perspective (unfortunetely I'm not a physicist either). If anybody has any arguments for the front higher, I'd love to hear them, and I'm sure others would aswell. And yes I concidered what Boosted2point4 said, but based on what I said above, if the car was lower in the front, and when accelerating the front still lifted, you would have to lower the front even more, because the angle of the car is not matching the angle that the force is being applied at. The closer the force is to perpendicular, the greater the effect it will have, like opening a door.
Re: discussion on optimal suspension setup for drag
Sunday, November 15, 2009 4:00 PM
WOW... didn't realize how long that was until I posted... nobody is going to read that lol....
Re: discussion on optimal suspension setup for drag
Sunday, November 15, 2009 5:51 PM
I did. Suspension set-up is a big part of your car.


- Your not-so-local, untrained, uncertified, backyard mechanic. But my @!#$ runs
Re: discussion on optimal suspension setup for drag
Sunday, November 15, 2009 5:54 PM
Oedwards wrote:I did. Suspension set-up is a big part of your car.


What worries me, is I'm talking purely in theory, if someone replies with practical examples, and theory... well I'm just going to be here all day... I can't wait to see what PJ does with his car, and hear his reasoning...
Re: discussion on optimal suspension setup for drag
Sunday, November 15, 2009 8:20 PM
ok found it finally, here is where my info came from, not my theory but seems to work, my car is slightly lower in the rear with the skinnies on the rear, but alot of gain was from preloading the car. link to thread-> http://honda-tech.com/showthread.php?t=2244782




R.I.P. Brian Klocke, you will never be forgotten
Re: discussion on optimal suspension setup for drag
Sunday, November 15, 2009 11:37 PM
I see what that Honda guy is saying, and though he seems to make a valid point with his 60-foot times... lets not forget that Honda weighs about 75% less than our Sunfire and should be pulling off equal or better 60 foots. Also, he did not intend to set the car up like that, it was merely a product of different height wheels front to back.

Fact is, the higher the front end is lifted in the air, the more drag it will have in all aspects, not just underneath the car. Demonstration (cause I liked his):
Push a wall through water thats 6 inches long. Now push a wall through water 7 inches long, I guarantee the 7 inch wall will have more resistance. Plain and simple.

As far as those rebuttals by daniel,
1. Lower bumper = more of a wall and would hurt aerodynamics.
2. When you're putting down 500 HP, the axles needed are quite expensive, though not a performance drawback... I would rather run 10.50 all day no axels breaking than 10.48 breaking axles more often.



Street-Legal 2003 Sunfire 10.58 @ 139 MPH
Re: discussion on optimal suspension setup for drag
Monday, November 16, 2009 5:27 AM
the main people talking in that thread was 2 neon guys, but i know what your saying, next year i plan on messing around with suspension and setup alot more, are you going to come out and play next year adam?




R.I.P. Brian Klocke, you will never be forgotten

Re: discussion on optimal suspension setup for drag
Monday, November 16, 2009 6:28 AM
Adam Hahn wrote: In all honesty, your driving style will determine the answer for your application. How fast you release the clutch and how much throttle you have, how much power you make down low, the tire width height and compound, so on and so on.


+1....

It has been proven time and again...

I have a 16G with nitto radials!
I pull down decent times






Re: discussion on optimal suspension setup for drag
Tuesday, November 17, 2009 3:48 PM
I like the discussion going on in here.


I really don't want to reveal what I'm doing until I have some results to share.. going on theory alone is sort of weak sauce, thats why I'm being tight lipped at the moment.

but I would agree the most with people saying keep the ride height level, as low as possible, and stiffen the rear as much as possible.





Re: discussion on optimal suspension setup for drag
Tuesday, November 17, 2009 7:41 PM
im going to a turbo/chassis class in jan. chassis portion is tought by chris rados crew cheif, ill be putting some of that info to use next year.




R.I.P. Brian Klocke, you will never be forgotten
Re: discussion on optimal suspension setup for drag
Thursday, November 19, 2009 10:43 AM
I've been thinking about this a lot and I just can not get my head around the fact that if the front is higher you cant transfer as much weight, and that raising the rear actually takes weight off the front.. It just seems against the rules of nature.


- Your not-so-local, untrained, uncertified, backyard mechanic. But my @!#$ runs
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