Alright, I've got some questions, and I'd like you knowledge guys/gals to teach me about what differences do what, and doing this makes this happen, and mounting here does this and all hat kind of stuff. But I'd also like to undersand how suspension (OEM, Aftermarket, good vs blown, etc) affects power getting to the wheels on a FWD car like ours, but also on a RWD truck or SUV (Like our jimmy). I'd also like to know when going aftermarket adjustable strut on our cars, how they should be set up for different uses. I have Yellows, and I've been driving around them basically 1/2 turn away from full hard. I read some other posts about the yellows, and there are people saying they have their 2 1/2 turns or something, but I only counted 2 full turns from full soft to full hard. So I'm a bit confused there. But, onto my questions.

First off, I'd like to start with OEM. If a factory set up, are the shocks on a car similar to ours set up to be softer than in the rear? Or are they harder in the front and softer in the rear? I'm speaking about struts/shocks specifically. Not springs. Now, why would the front or rear be softer than the others? What would be the purpose? Just comfort? I would assume it would have to be something besides comfort.
I know our cars kinda handle like @!#$ factory, so getting in the aftermarket segment with adjustable struts would you want softer front, harder rear? I know the purpose of strut tower bars, and sway bars/anti-roll bars etc. I'm speaking specifically to the struts.

Okay, second, How do shocks/struts affect power getting to the wheels going in a straight line? I understand that springs/shocks and all that are meant to keep the wheels against the ground. I understand in a factory setting thats what they are for. But how do aftermarket struts affect power? Lets say the struts are set harder, so when you've got a FWD car with the wheels pulling the weight, you give it throttle, the weight of the vehicle shifts backwards. Would having harder setting in the back keep the weight shift minimal? W're probably talking fractions of a second, but wouldn't that keep the weight over more of the center line, therefor less weight transfer, and a faster take off?
Now, same situation, but with a RWD SUV. Do you WANT the weight transfer for more traction? Wouldn't that slow down the take off though?
What if the struts are blown, or bad, or just really soft? Wouldn't that affect take off? Make it slower? softer shocks equals more weight transfer from front to back? I don't really understand how this affects a 1/4 time, but I know it affects something.

And third, how do you set up adjustable struts on our cars for daily driving? Softer front harder rear? Vice versa? What about an auto-x? How do you want to set that up? Just a idea is all I'm looking for.


Sorry about the long post, but I'm very curious about how this stuff works. If you have any links to info or something then please post. Thanks.

Ok, spring rates. They're higher in the front, why? Most of the weight of the car is in the front, ie the engine. Damping rates, ie shocks/struts need to match the springs that are mounted to them, but you can get different effects from amounts of damping on a spring, mostly turn in turn out effects. Damping rates effects how fast the natural spring oscillation are are quelled. If you're getting wheel hop its either from too much damping or not enough, almost alway not enough though.

For setting up a fwd car with adjustable coil overs I would jack the ride height and spring preload all the way up in the back and then tune the damping all the way up so that the car would not spring forward at random times going down the track. The fronts would be set at normal street height with the lower A arms parallel to the ground (how they should always be set all the time, might as well weld the spring perches to keep it there). No spring pre-load, this is generally bad. Medium damping. Now spring rates, which almost none of you will ever tune so I wont bother.

For RWD, max out the suspension travel on the rear to allow for maximum squatting. Low compression damping, SUPER high rebound damping. You want the car the squat and stay there. then mess with all the other stuff to keep the squat and stay there going, you dont want to hit the bottom too soon or too hard or you'll loose traction.


1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by: Kronos Performance

WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer

to the op: one thing to note is that the shocks do not change the amount of suspension travel or weight transfer. the shocks change the force they impart based on velocity of the motion of the suspension. as the suspension attempts to move faster, the shocks become more difficult to extend or retract. therefore, the amount of weight transfer, bump and droop, roll, etc., should be adjusted by the spring rate, roll center location, anti-roll bars, anti-squat/anti-dive, cg location, etc. the shocks should just be there to dampen the frequency of the suspension oscillations and keep all tires on the ground all of the time.





87 Firebird
All stock...........lol.

Sunfiretun3r wrote:Alright, I've got some questions, and I'd like you knowledge guys/gals to teach me about what differences do what, and doing this makes this happen, and mounting here does this and all hat kind of stuff. But I'd also like to undersand how suspension (OEM, Aftermarket, good vs blown, etc) affects power getting to the wheels on a FWD car like ours, but also on a RWD truck or SUV (Like our jimmy). I'd also like to know when going aftermarket adjustable strut on our cars, how they should be set up for different uses. I have Yellows, and I've been driving around them basically 1/2 turn away from full hard. I read some other posts about the yellows, and there are people saying they have their 2 1/2 turns or something, but I only counted 2 full turns from full soft to full hard. So I'm a bit confused there. But, onto my questions.

First off, I'd like to start with OEM. If a factory set up, are the shocks on a car similar to ours set up to be softer than in the rear? Or are they harder in the front and softer in the rear? I'm speaking about struts/shocks specifically. Not springs. Now, why would the front or rear be softer than the others? What would be the purpose? Just comfort? I would assume it would have to be something besides comfort.
I know our cars kinda handle like @!#$ factory, so getting in the aftermarket segment with adjustable struts would you want softer front, harder rear? I know the purpose of strut tower bars, and sway bars/anti-roll bars etc. I'm speaking specifically to the struts.

Okay, second, How do shocks/struts affect power getting to the wheels going in a straight line? I understand that springs/shocks and all that are meant to keep the wheels against the ground. I understand in a factory setting thats what they are for. But how do aftermarket struts affect power? Lets say the struts are set harder, so when you've got a FWD car with the wheels pulling the weight, you give it throttle, the weight of the vehicle shifts backwards. Would having harder setting in the back keep the weight shift minimal? W're probably talking fractions of a second, but wouldn't that keep the weight over more of the center line, therefor less weight transfer, and a faster take off?
Now, same situation, but with a RWD SUV. Do you WANT the weight transfer for more traction? Wouldn't that slow down the take off though?
What if the struts are blown, or bad, or just really soft? Wouldn't that affect take off? Make it slower? softer shocks equals more weight transfer from front to back? I don't really understand how this affects a 1/4 time, but I know it affects something.

Stock spring rates are about 150front,100rear at a rough guess. Having the rear softer is critical for comfort because the weight of the car is mostly in the front. You can imagine a seesaw, where the center pivot is the front suspension of the car (because the engine is so heavy) and the person in the seat is the rear of the car, their legs the springs. If you have softer springs in the back, the up and down motion is smooth and slow. If you have high spring rate (ie: high energy) springs in the back, imagine the persons legs are incapable of flexing very easily. The impact with the ground is harder and more energy is transferred to the body. While it's not accurate entirely, imagine softer spring rates equating to more bend in the knees. Straight legs = replacing struts with steel rods.

For straight line racing in a FWD, rear spring rate should ideally be pretty high. For the reason you explained, being that the weight transfer to the rear wheels on launch would be offset by the energy in the springs pushing the rear end up (not as much squat). Leafy covered RWD application great, so I won't bother. Higher spring rate in the rear is also said to help in cornering, helping reduce understeer by keeping the weight towards the front of the vehicle, ie: more traction to the drive wheel.s

Your question about struts being blown effecting racing can be answered by defining a shock as a damper. That is, it doesn't make the spring harder or softer but limits the movement of the spring hydraulically. So a blown strut would hamper drag racing in, such as, when you get wheel hop off the line, the damper wouldn't slow the 'bounce' of the spring so the wheel hop wouldn't be controlled. Savvy?

Quote:


And third, how do you set up adjustable struts on our cars for daily driving? Softer front harder rear? Vice versa? What about an auto-x? How do you want to set that up? Just a idea is all I'm looking for.

For street (COMFORT) I'd say softer rear absolutely, for the reason I explained above. Also longer springs are a good thing when lowering the car.
For race it's generally heavier spring rates, higher damping (aside from the rebound stroke)

One thing I left off, a common shade tree trick for fwd cars is to jack the car up at the strip and put footballs somewhere in the rear suspension to jack it up more, with ours I'd bet on the trailing arm next to the shocks.


1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by: Kronos Performance

WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer

Footballs? That cant be safe. I can see the idea though. Hahaha.

Good info here.

The rule of thumb for tuning suspension for auto-x is- stiffen up the end that sticks. If you understeer, run higher rates in the rear (or lower in the front). Oversteer- just the opposite. Changing rates can be done with spring rates and sway bar rates. The adjustable damping comes into play only AFTER you've set your spring/bar rates, and have the same effect as changing the spring/bar rates. Stiffer= higher rate (slowing down oscillation more). Your overall tune process should go- spring, bar, extension, compression. Don't expect to see a ton of change in the damping adjustment. You can change things up a bit more by playing with tire pressure and size, and it's much more economically feasible for an daily driver/auto-x car to do that than it is to go out and buy double adjustable dampers. Rates to run will depend on each specific car. EX- my car has around 900lb linear front rates (spring and bar included) and around 700-1200lb progressive rear rates. I wanted higher rates up front, and I couldn't get neutral handling with anything less in the rear. I know other similar cars with rates around 300lbs, and they do just fine too.
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Thank you guys so much for the info. That answered my questions.

I understand that spring keeps the wheels in contact with the ground and the strut just dampens the spring oscillations, but I was curious how that's affected using different struts, different dampening forces, all that stuff. I get that the sprong rates in the front of a FWD car would be higher to support the heavier weight, but I was talking specifically of the struts. How the OEM stuff is set up. But I get all that now.

So daily driving you would want a bit softer in the rear, a bit harder in the front. For racing purposes in a straight line, basically full hard in the rear to prevent weight transfer as much as possible (within the springs abilities) and hard enough to prevent wheel hop in front, but not too hard as to make it worse. Got it.

Thanks again guys. You guys know so much, it's a pleasure to learn.

Stock damping rates will normally be designed based on the spring to a damping ratio of 3 I believe, which would mean that stock the car is designed to have 3 major oscillation before being completely damped. Wait 3 doesnt seem right, it must be larger than that.


1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by: Kronos Performance

WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer