I was wondering if anyonce has put the K's / HICAS rear sway bar on. If so, did it promote snap oversteer?
stock sway bars for a 1990 240sxw/o sports package front 24mm rear 15mm
HICASfront 25mm rear 21mm
Larger Rear Sway Bar = Snap Oversteer?
Are you sure that you have that front sway measurement correct? IIRC the front is smaller than the non-HICAS and the rear was larger than the non-HICAS.
Regardless I know of a couple of guys running the HICAS rear bar and kouki S13 SE front bar w/o snap oversteer issues. That is my planned sway bar upgrade path....IF I could just find one for sale:(
Regardless I know of a couple of guys running the HICAS rear bar and kouki S13 SE front bar w/o snap oversteer issues. That is my planned sway bar upgrade path....IF I could just find one for sale:(
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Q45tech
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- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Snap oversteer usually shows up when rear bars exceed the safe rule of thumb of being equal or less stiff than the springs, since they overwhelm the shocks which are never upgrade to the overdamped stiffness.
Shocks are matched to springs and the extra stiffness is never considered.
Something like a rear 25-26mm bar is getting close to being EXCESSIVE since that would be twice as stiff as a 21mm bar. Roughly 100-120 pounds per inch of wheel rate vs 45-50 of the 21mm bar. Obviously soldid bars are 10-12% stiffer than hollow ones.....sometimes.Lowering springs buy you a little reserve since they are stiffer by at least 20%.
Tires are the main culprit in snap over steer. The usual solution is wider rear and softer compound rears............and learning to balance power transfer while turning.
The rear of a RWD car always has more friction in a turn [not counting that lost to acceleration] because the extra Front weight has overloaded the front tires......rear sway bars decrease the rear superiority and help reduce the load on the front tires...........obviously going too far has a negative effect.
Shocks are matched to springs and the extra stiffness is never considered.
Something like a rear 25-26mm bar is getting close to being EXCESSIVE since that would be twice as stiff as a 21mm bar. Roughly 100-120 pounds per inch of wheel rate vs 45-50 of the 21mm bar. Obviously soldid bars are 10-12% stiffer than hollow ones.....sometimes.Lowering springs buy you a little reserve since they are stiffer by at least 20%.
Tires are the main culprit in snap over steer. The usual solution is wider rear and softer compound rears............and learning to balance power transfer while turning.
The rear of a RWD car always has more friction in a turn [not counting that lost to acceleration] because the extra Front weight has overloaded the front tires......rear sway bars decrease the rear superiority and help reduce the load on the front tires...........obviously going too far has a negative effect.
Thanks for the reply. I wasn't sure if going from a 15mm to a 21mm rear would have negative effects. I thought that it would be OK in this instance because the HICAS cars came with the same bar. It didn't seem like HICAS would make it safer.
I'm not really sure why the non-HICAS car's came with a 6mm smaller bar. Do all of the K's have HICAS?
I'm not really sure why the non-HICAS car's came with a 6mm smaller bar. Do all of the K's have HICAS?
Hicas was part of (or came with) the sport suspension upgrade package, so the swaybar is larger and the struts/springs are sportier. It also came with a quicker steering rack that everyone tries to buy and abs (that I'm going to remove).
Sorry about the doughnut confusion...I thought you meant the 'drift pineapples' (because I thought they looked like doughnuts and the whole food thing...) which are rear subframe spacers and I was just making sure you weren't buying those with hopes of installing them on the front of your car!
Sorry about the doughnut confusion...I thought you meant the 'drift pineapples' (because I thought they looked like doughnuts and the whole food thing...) which are rear subframe spacers and I was just making sure you weren't buying those with hopes of installing them on the front of your car!
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Q45tech
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- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Using "500 lb/ft" might confuse some , the rear coil springs are on the order of 100-120 pounds per inch and adding the bar [say 40-50] means that in the compression phase where the shock stroke limit is 3.5" you have an NORMAL LINEAR stiffness of 3.5 x 150-170= 505-595 POUNDS in 3.5 INCHES.
IF the springs and or shocks reach the limit of the compressive range then the suspension is in fact nearly infinite EXCEPT the tires and the wheels have compliance [they bend] the tire can be 1000-1500 pounds per inch and the wheels are stiffner.
The job of the various bump stops is to have an INTERMEDIATE stiffness say 350-500 even 700 pounds per inch, before the final tire stiffness.
So inifinite stiffness is not really correct just that the stiffness at least suddenly doubles then triples and quadtruples.
Usually the highway departments don't allow big bumps in the middle of curves where these things could occur.
Snap oversteer is a problem in rain/snow/ice [at speed] where the tires are already operating at half friction or less........not usually in dry.........unless the shocks are worn or incorrect.
A light car like the SX doesn't create the body roll to usually exceed the 3.5" compression in the rear so owners who add SERIOUS rear sway bars are thought to be smart enough to use SERIOUS rear tires appropriate for road temperatures and friction conditions..........wider and stickier............like the 300zxtt used.
IF the springs and or shocks reach the limit of the compressive range then the suspension is in fact nearly infinite EXCEPT the tires and the wheels have compliance [they bend] the tire can be 1000-1500 pounds per inch and the wheels are stiffner.
The job of the various bump stops is to have an INTERMEDIATE stiffness say 350-500 even 700 pounds per inch, before the final tire stiffness.
So inifinite stiffness is not really correct just that the stiffness at least suddenly doubles then triples and quadtruples.
Usually the highway departments don't allow big bumps in the middle of curves where these things could occur.
Snap oversteer is a problem in rain/snow/ice [at speed] where the tires are already operating at half friction or less........not usually in dry.........unless the shocks are worn or incorrect.
A light car like the SX doesn't create the body roll to usually exceed the 3.5" compression in the rear so owners who add SERIOUS rear sway bars are thought to be smart enough to use SERIOUS rear tires appropriate for road temperatures and friction conditions..........wider and stickier............like the 300zxtt used.
lol.....
I recently destroyed my front d-brackets for the front swaybar when I bottomed out while driving through a parking lot gutter. The new brackets should be here tomorrow via UPS.
Anyway, all this "snap-oversteer" talk is funny because I currently only have a front strut tower bar with a rear strut tower bar and Whiteline rear swaybar!!! You want to talk about snap oversteer!!
I recently destroyed my front d-brackets for the front swaybar when I bottomed out while driving through a parking lot gutter. The new brackets should be here tomorrow via UPS.
Anyway, all this "snap-oversteer" talk is funny because I currently only have a front strut tower bar with a rear strut tower bar and Whiteline rear swaybar!!! You want to talk about snap oversteer!!
What D bushings did you use for the sway bar? Where did you get 21mm bushings at?
Also, the sway bar that I finally found has the endlinks on it still, but I would like to replace the bushings. Can I just get the same bushings that are used for the stock endlinks? Like the Whiteline ones that PDM sells?
Also, the sway bar that I finally found has the endlinks on it still, but I would like to replace the bushings. Can I just get the same bushings that are used for the stock endlinks? Like the Whiteline ones that PDM sells?
rico05 wrote:What D bushings did you use for the sway bar? Where did you get 21mm bushings at?
Also, the sway bar that I finally found has the endlinks on it still, but I would like to replace the bushings. Can I just get the same bushings that are used for the stock endlinks? Like the Whiteline ones that PDM sells?
I used the stock D bushings.You can use the energy suspension bushings (8 pack for $10 w/ new washers) or the whiteline. Without the new endlinks it may be a tight fit.
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Nismo_Freak
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Dystopia wrote:q45tech what size swaybar woudl you recomend for 12kg/mm front and 10kg/mm so 672/560. i know these are very high spring rates....
I'd recommend using an OEM bar set from an SE. Upgrading to larger sways is going to overwealm any street compound tire you put on the car.
Those spring rates are ENTIRELY too high for a car to be driven on the street... seriously.
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Q45tech
- Moderator
- Posts: 14296
- Joined: Tue Apr 30, 2002 3:19 am
- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
"what size swaybar woudl you recomend for 12kg/mm front and 10kg/mm so 672/560".........With springs 5 times stiffer than oem do you really need sway bars and if you had bars would they do anything is the question.
A 4300 pound Q has 146 lb/in front springs and sways 3.5 " [the limit of the shock stroke]. The 16" springs compress 8" with body weight so the spring natural frequency is 1.1Hz.........these same springs on a 240sx [lighter] might compress 7" yielding a 1.185 Hz frequency.
A 300 lb/in spring would be 1.675 Hz, a 620 lb/in spring would compress only 1.648" and have a natural frequency 0f 2.44 Hz.
Nissan uses a setup that has a progressive bar engagement on the rear [the amount of body roll required to compress the rubber bushings and mounts] so the 15 mm rear bar only gets up to 10% of the spring rate, the 21mm bar maybe gets to 40% of the 120 # spring rate.
My guess is 40% of spring rates on the rear and at least 50% on the front...........they don't make bars that large in diameter as a 24mm rear bar would only have a wheel rate of 120 lb/in because of the way the rear bar attaches in the middle of lower arm.
Any bars available would be insignificant compared to the springs but they would allow you to fine tune the springs ----just think bigger steps. A 21mm rear [fully coupled] might be 8-10% stiffer vs just the springs.
A 4300 pound Q has 146 lb/in front springs and sways 3.5 " [the limit of the shock stroke]. The 16" springs compress 8" with body weight so the spring natural frequency is 1.1Hz.........these same springs on a 240sx [lighter] might compress 7" yielding a 1.185 Hz frequency.
A 300 lb/in spring would be 1.675 Hz, a 620 lb/in spring would compress only 1.648" and have a natural frequency 0f 2.44 Hz.
Nissan uses a setup that has a progressive bar engagement on the rear [the amount of body roll required to compress the rubber bushings and mounts] so the 15 mm rear bar only gets up to 10% of the spring rate, the 21mm bar maybe gets to 40% of the 120 # spring rate.
My guess is 40% of spring rates on the rear and at least 50% on the front...........they don't make bars that large in diameter as a 24mm rear bar would only have a wheel rate of 120 lb/in because of the way the rear bar attaches in the middle of lower arm.
Any bars available would be insignificant compared to the springs but they would allow you to fine tune the springs ----just think bigger steps. A 21mm rear [fully coupled] might be 8-10% stiffer vs just the springs.
Nismo_Freak wrote:Those spring rates are ENTIRELY too high for a car to be driven on the street... seriously.
i have had them on my car for daily driving for almost a year, they do fine for me, i am used to it now, i normally run larger side walls for daily driving.
fine tuning is all i am really looking to do, i have little to no boddy roll mostly tire flex. I was thinking about the whiteline ajustable swaybars, do you think it would be worth it or should i go with smething larger like the cusco units...
rico05 wrote:Well, the whiteline part numbers for the D bushings are specific for non HICAS cars, but the endlink bushings do not have that stipulation, so I hope that they fit. Thanks for all your help, and I am sorry if I quasi jacked your thread;)
np.You should be able to get 21mm D bushings from ES.If you use the OEM endlinks, it just may be a little difficult to compress the bushings to get the washer and nut on. I would also be sure to new washers or just use the ES kit that comes with the bushings and washers.