hey,
i am thinking about a set of coilovers with 8kg/6kg spring rates (the JIC FLT A2), do you think this is too stiff for the street, practically? id like to be able to ride fast over somewhat ruff roads (not ruff, but no road is really smooth), i just dont want them to be unsafe and skate over bumps. its the only consideration i have for not getting them, i have been looking at less agressive coilovers from JIC and a few other brands, or maybe a set of coils and dampers but i want to make sure they match well. thanks for any help
too stiff for the road, where is the limit?
OMG just order the Jics already. If they are too stiff, sell them right away. You'll hardly lose anything! If not, you'll be happy and problem solved. It's not just spring rates. It's also how the dampers are valved.
As I've said 100x before, you're either gonna have to drive in someone else's car with them installed or take a chance. No one can answer this question for you, but you!!!
As I've said 100x before, you're either gonna have to drive in someone else's car with them installed or take a chance. No one can answer this question for you, but you!!!
Especially on the internet. This reminds me of the guy asking opinions on whether or not HE'LL notice a difference in speaker sound quality. How would I know...? Some things must be done in person.
Generally, a coilover is valved to provide response, not comfort. Softer settings aren't really soft. You'll do just fine with springs/struts:D
Generally, a coilover is valved to provide response, not comfort. Softer settings aren't really soft. You'll do just fine with springs/struts:D
there is an issue of Import Tuner where they install some Jic coilovers on a 96 s14. they said the ride from the street to the track was firm but not unbearable, just obviously watch out for potholes n such. you can make it quite a bit stiffer, but even on the softest setting is quite stiff. It was the march 03 import tuner, you can check out their site online.
ANyways, unfortunately, like all the above peeps said, its a matter of personal preference...-chet
Re: too stiff for the road, where is the limit?
I don't think you'll have to worry about skating with the JIC spring rate. I've *never* heard of anyone complain of that with the FLT-A2's. Uncomfortable maybe, but not unsafe. Like everyone said, ride quality is somewhat subjective.Ceptos wrote:i just dont want them to be unsafe and skate over bumps.
From what I've read, an 8 kg/mm front 6 kg/mm rear set up is a nice compromise between street and track. I was considering Tein HE's for my car and did a ton of research (same spring rate as the FLT-A2's), before some rather unfortunate compression test results changed my budget.
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turboweege
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hey mojo, could you please hit me up at [email protected] about your stock shock measurements....
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Q45tech
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6kg/mm rear = 335 pounds per inch roughly 215 pounds per inch stiffer than oem's normal 120 pounds
Normally one uses a rear sway bar that is sligthly less than equal to the rear spring stiffness to avoid/lessen the abrupt street impacts.
REAR Sway bar coupled wheel rates of 40-80 even 100 pounds per chassis roll inch with 120# springs to effectively create 160-200-220# rear springs in maneuvers.
Must be pretty exhusting to drive these sprung cars more than a hour or two considering the effects on human body of higher suspension natural frequency.
For a 240SX I calculate approximately 2.0 Hertz with the 8/6kgmm vs 1.2 Hertz for stock springs
http://www.smithees-racetech.c....html
"Natural Frequency [CPM - cycles per minute] = 187.8 times {square root of (wheel rate [lb/in] divided by sprung weight [lb])} Wheel Rate = Coil Rate [lb/in] divided by {suspension leverage raised to the second power} (Low leverages - MacPherson struts - mean that wheel rates are approximately the same as coil rates.) Since the tire is also a spring acting in series with the coil, you can take it into consideration by calculating: Reciprocal value of combined spring rate [lb/in] = reciprocal value of coil rate [lb/in] + reciprocal value of tire rate [lb/in] Tire Rate = say 1,500 lb/in Suspension Frequency values:60-80 for comfortable road cars 80-100 for firmer and sport suspension100-175 for non-ground effect racers In order to avoid uncontrollable pitching, the front frequency is 10 to 20 CPM lower than the rear frequency.
When designing the suspension, care has to be taken to divide the useful stroke of the shock absorber correctly between the bump and rebound. Adjustable spring perches do not automatically solve this. For instance, a higher preload on the spring will result in more bump and less rebound. "
Normally one uses a rear sway bar that is sligthly less than equal to the rear spring stiffness to avoid/lessen the abrupt street impacts.
REAR Sway bar coupled wheel rates of 40-80 even 100 pounds per chassis roll inch with 120# springs to effectively create 160-200-220# rear springs in maneuvers.
Must be pretty exhusting to drive these sprung cars more than a hour or two considering the effects on human body of higher suspension natural frequency.
For a 240SX I calculate approximately 2.0 Hertz with the 8/6kgmm vs 1.2 Hertz for stock springs
http://www.smithees-racetech.c....html
"Natural Frequency [CPM - cycles per minute] = 187.8 times {square root of (wheel rate [lb/in] divided by sprung weight [lb])} Wheel Rate = Coil Rate [lb/in] divided by {suspension leverage raised to the second power} (Low leverages - MacPherson struts - mean that wheel rates are approximately the same as coil rates.) Since the tire is also a spring acting in series with the coil, you can take it into consideration by calculating: Reciprocal value of combined spring rate [lb/in] = reciprocal value of coil rate [lb/in] + reciprocal value of tire rate [lb/in] Tire Rate = say 1,500 lb/in Suspension Frequency values:60-80 for comfortable road cars 80-100 for firmer and sport suspension100-175 for non-ground effect racers In order to avoid uncontrollable pitching, the front frequency is 10 to 20 CPM lower than the rear frequency.
When designing the suspension, care has to be taken to divide the useful stroke of the shock absorber correctly between the bump and rebound. Adjustable spring perches do not automatically solve this. For instance, a higher preload on the spring will result in more bump and less rebound. "
Though my experience is with a different car, I think my observations would still be relevant here. I used to have a Mustang 5.0 with front spring rates that were 700-850lbs/inch progressive rates and the rear was a linear rate 200lb spring. That sounds like the rear was way too soft, but the rear suspension in Mustangs binds a lot through the travel so it's really more than the stated rate. Anyway, yes it was very stiff, but I had that car for about 5 years with those springs and loved every corner. It never skipped over bumps except for what you are to expect from a solid rear axle. So, the 8/6 rates would probably be very nice for a street car.
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Q45tech
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1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
People don't understand that WHERE the springs are attached to the lower suspension arm determines the wheel rate.
Your Mustang has the FRONT spring roughly in the middle of the lower arm so you divide the spring rate by 4.0 to find the wheel rate..........your front spring acted like 175-212 lb/inch at the wheels.The angle of MacPearson or coil overs from the pertendicular must be corrected for ................most unless more than 15% tilted inward use 0.9-1.0 correction factor .
Same with sway bar, the bar if connected to the middle of lower a arm via end links [like Nissan rear] is only transferring 25% to the wheel.
Most Nissan has the springs attached to the knuckle [effectively the wheel] and the rear bar at mid point and front bar at/to shock [except 90-96 Q45] so the arm length must be double [6">12"]to halve the rate.
The point is with out all the correction math [trig] you cannot compare springs/sway bars from different car designs to another car even within the same brand.
Almost all factory passenger cars have front effective wheel rates in the 120-160 lb/inch range and rears in the 100- 140 lb/in range. The fronts are almost always 1.2 times the rear.
Your Mustang has the FRONT spring roughly in the middle of the lower arm so you divide the spring rate by 4.0 to find the wheel rate..........your front spring acted like 175-212 lb/inch at the wheels.The angle of MacPearson or coil overs from the pertendicular must be corrected for ................most unless more than 15% tilted inward use 0.9-1.0 correction factor .
Same with sway bar, the bar if connected to the middle of lower a arm via end links [like Nissan rear] is only transferring 25% to the wheel.
Most Nissan has the springs attached to the knuckle [effectively the wheel] and the rear bar at mid point and front bar at/to shock [except 90-96 Q45] so the arm length must be double [6">12"]to halve the rate.
The point is with out all the correction math [trig] you cannot compare springs/sway bars from different car designs to another car even within the same brand.
Almost all factory passenger cars have front effective wheel rates in the 120-160 lb/inch range and rears in the 100- 140 lb/in range. The fronts are almost always 1.2 times the rear.
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Q45tech
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1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Simple measure the wheel arch with the tires off the ground then with the weight on the tire...........or spring free length [unmounted] and the compressed length with weight on the tire.
For example a Q45 [1990] has a front free length of 16.89" with roughly1110 pounds on the front [but 160 # is unsprung] so 1110- minus 160=950 shows a compression of 6.5"= 146 pounds per inch................we have measured springs and at stock height they are 140-150................the simple process works with reasonable accuracy if you know the cars weight and distribution.No car is perfect side to side and front to rear to side.
How much does you car drop with you in drivers seat .........probably 1/2">3/4" front and rear with oem springs.
For example a Q45 [1990] has a front free length of 16.89" with roughly1110 pounds on the front [but 160 # is unsprung] so 1110- minus 160=950 shows a compression of 6.5"= 146 pounds per inch................we have measured springs and at stock height they are 140-150................the simple process works with reasonable accuracy if you know the cars weight and distribution.No car is perfect side to side and front to rear to side.
How much does you car drop with you in drivers seat .........probably 1/2">3/4" front and rear with oem springs.
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Q45tech
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1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Generally changing the factory spring settings by more than 20% creates ride problems and doesn't improve handling [peak G's] to any degree. Changing the rear to front roll couple ratio can improve things by increasing the rear tire slip angles [trading off some of the excess rear traction compared to the front.You must know the suspension camber gain ciurves per inch of roll.
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Q45tech
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1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
You measure the camber [with a special magnetic or clip on gauge] with a jack/scales under the tire at different compressions/sags..........also chain hoist to pull the body down.........not the easiest thing to measure.
Hopefully the factory has designed in enough to compensate for the oem tire and size.
Ideally you want a negative 0.5 degrees more than what ever amount positive the tire does under various amounts of body rollhttp://www.rahul.net/dennisp/s....htmlhttp://e ... p/asgp.htm
Take a moment to calculate your body roll! is it 3, 4, or 5 degrees at 1 G?
"Since available tire grip represents about 80 percent of the handling equation, the best way to get more grip is with stickier tires. Reducing body roll alone will not necessarily result in significant handling improvements, and the amount of acceptable roll varies with driver preference. Some roll is good to aid in your perception of where the car is relative to the limit of the envelope. Increased roll stiffness can improve transient response, but will also make the car less forgiving. The less compliant a car, the quicker it reacts and eventually you get to the point where the driver can't keep up because the feedback frequency is too high. That will have you spinning a lot! Keep in mind how you actually use the car and how harsh a ride you are willing to accept in exchange for improved handling and remember that tires make the biggest difference. If you have low performance tires adding roll stiffness is not going to make the car corner much better, but it will definitely make it harsher, more rattly, and less forgiving."
Hopefully the factory has designed in enough to compensate for the oem tire and size.
Ideally you want a negative 0.5 degrees more than what ever amount positive the tire does under various amounts of body rollhttp://www.rahul.net/dennisp/s....htmlhttp://e ... p/asgp.htm
Take a moment to calculate your body roll! is it 3, 4, or 5 degrees at 1 G?
"Since available tire grip represents about 80 percent of the handling equation, the best way to get more grip is with stickier tires. Reducing body roll alone will not necessarily result in significant handling improvements, and the amount of acceptable roll varies with driver preference. Some roll is good to aid in your perception of where the car is relative to the limit of the envelope. Increased roll stiffness can improve transient response, but will also make the car less forgiving. The less compliant a car, the quicker it reacts and eventually you get to the point where the driver can't keep up because the feedback frequency is too high. That will have you spinning a lot! Keep in mind how you actually use the car and how harsh a ride you are willing to accept in exchange for improved handling and remember that tires make the biggest difference. If you have low performance tires adding roll stiffness is not going to make the car corner much better, but it will definitely make it harsher, more rattly, and less forgiving."
went to Bobby Archer motorsports the other day. Bobby Archer is a pretty famous roadracer, raced the **** out of some vipers (le mans, etc.). anyways, his shop was saying that the info from Q45tech is good, but not necessary unless you are planning to build a race car. for the street, even some track time, if you wanted some coilovers with X swaybars and Y strut bars, you would still be good to go. no need to overkill street suspension. but that is still good info, and if you can understand it enough to apply it, and are a good enough driver for it to make a difference, then go for it, but not really necessary.
AJ, I think Q45tech's message is to steer us away from excessive suspension mods, instead focusing on grip. There's another similar thread which basically has the same info, in which Q45tech spelled all this out for us.
"Since available tire grip represents about 80 percent of the handling equation, the best way to get more grip is with stickier tires. Reducing body roll alone will not necessarily result in significant handling improvements" --lets all put this info to good use!
"Since available tire grip represents about 80 percent of the handling equation, the best way to get more grip is with stickier tires. Reducing body roll alone will not necessarily result in significant handling improvements" --lets all put this info to good use!
Exar, you say that ride harshness is a matter of personal preference? I disagree with this. I would be happy to set my coilovers to maximum stiffness if it would help my handling, but my car would probably skate over a good number of bumps and tires off the road dont help my handling (i think). hehe. does anyone have any suggestions for the highest possible stiffness setting for the street, based on physics, not ride quality? 
also i have a random question that isnt important enough to put in a seperate post - if i set my coilovers to 1 in the front and 16 in the back, what would happen? i would try it myself if i was in a parking lot, but alas i have to go to class in a couple hours.
also i have a random question that isnt important enough to put in a seperate post - if i set my coilovers to 1 in the front and 16 in the back, what would happen? i would try it myself if i was in a parking lot, but alas i have to go to class in a couple hours.
thats true, but for different enviroments(street, auto-cross, road race) differet stiffness settings are more/less usefull.
for instance, on a "rough" road, too stiff a setting may cause you to 'skate' over bumps, but for track use may be exactly what you need, given the tires and tracks condition(relatively sticky and smooth, respectively)
so its still all relative. even ammongst track prepped cars, some consider certain cars "stiff" and others "soft"...likewise, driving styles may differ, some prefer a softer setting, and make smoother transitions..other dont, and prefer softer setings, etc
in response to your post, you would probably oversteer so bad it wouldnt even be funny....-chet
for instance, on a "rough" road, too stiff a setting may cause you to 'skate' over bumps, but for track use may be exactly what you need, given the tires and tracks condition(relatively sticky and smooth, respectively)
so its still all relative. even ammongst track prepped cars, some consider certain cars "stiff" and others "soft"...likewise, driving styles may differ, some prefer a softer setting, and make smoother transitions..other dont, and prefer softer setings, etc
in response to your post, you would probably oversteer so bad it wouldnt even be funny....-chet