17MM 20MM 24MM 28MM 29MM Which Sway Bar is right for you?

[PopPop]

Which combo works best under what condition? I know we talked about this before and not too long ago but, which combo is right for your car? 28MM front and 20MM rear seems to be the best all around combo for everyday driving conditions but, what about cars that have performance MOD's? This may be the most likely way to go for a stock set-up but, what about people who are making more HP or better yet more Torque? I know for a fact that you will get a rougher ride out of a stiff poly suspension set-up for everyday use it's hard on the car and you! People with 400 plus HP need a bigger rear and front sway bar set-up for weight transfer reasons! Right or Wrong? For this reason I would think it better for cars with high HP and high Torque output to use a 29MM front SB and 24mm Stillen SB in the rear! The weight transfer will be better and you won't lose Quarter Mile time because of so much suspension give under launch and shift point loads! Now this is for cars that are raced a lot and not driven daily but, for street application 28MM / 20MM is the better choice for every day driving conditions!

[Rex]

A few excerpts

Both the t and a versions of the 90-95Q Q use the smaller 28 mm front sway bar with a sloppy 2x2 rubber bushing set up that in effect doesn't engage the bar till the body rolls at least 1.0", to minimize street bumps and pitching.

The front rear spring ratio is roughly equal to the weight ratio 146/123 so the car steers neutrally until the front bar starts engaging progressively as the bushing compress............neutral to slight under steer, medium understeer to extreme understeer as the body rolls 1>2>2.5>3".

Hopefully you can see why a softer front bar creates LESS understeer.....why the engineers chose a 13% less stiff bar and added a mild rear bar........the rear bar doesn't have to be as stiff if the front is softer......makes for a better rear ride on the street.

Eibach springs are 15% stiffer front [linear] but progressive in rear so the car has more understeer in the beginning of body roll that switches more towards neutral as the rear body rolls then can approach oversteer at the extreme on body roll.

The optimum bar ratio didn't have a lot to do with the extra active weight on the front as that is taken care [matched ] of by springs active struts.

Bars are a way of fine tuning fore aft weight ratios.

A 28 front and 20mm rear works great for the street/ interstate........not that a 22mm rear wouldn't work a tiny bit better but unavailable.

Since it was brought up in this thread.

Careful ask if it is only the miniscule 15.9mm rear t bar instead of the desirable 20mm active bar?

If the front bar came from a car with either rear bar it is the disirable 28mm instead on the conventional 29mm.

It takes the 28mm front and the 15.9mm rear in combination to shift the roll couple ratio : 6.5% off the front and add 10% roll stiffness to the rear........totalling 16.5%/~~2= 8% change vs 19.5% with the stiffer 20 mm rear bar and softer front bar.

The oem front bar on all standard Q is 29 mm in diameter, the oem rear bars are designed assumming that the front bar diameter is REDUCED to the 28 mm version used on "T" and "Active" Q.Why just adding the 15.9 mm rear "t" bar does little good without the 13% reduction in front roll bar stiffness [the total springs plus bar drops by 6.5% at max roll = 3.5"].

Hard to feel a 6-7% rear increase in Net total stiffness from a 15.9 mm bar, HARDER yet to just feel a 3% change without the smaller front bar] but a 20-25% rear increase from the 20 mm bar is noticeable...........but more noticeable with the smaller front bar.

The ideal [aggressive] rear bar size is 22mm [with a 28 mm front bar] but that doesn't exist.

The rear bars are rubber isolated [mounts and end links] so little happens in the 1st inch till all the rubber compresses. Why the above numbers are not 10% and 33%.

Nothing wrong with front body roll since the upper link compensates for tire camber changes........if the tires can stand it [sidewall stiffness].

See the 6.5% from the front reduction and the 6.5% from the rear addition make a 13% shift towards the rear but 13% of say 75% [forward bias] is not much ~~ say 67% and the 20mm addition gets you to 61-62% forward stiifness ratio with a 54% front vehicle weight.................7-8% above the critical level [when dry is neutral steering]........enough to still be safe in rain and power on curves at 0.55G lateral [if the tires can handle it].

You can buy either/all bars from Scottsdale, most people chose the larger diameter 20mm ACTIVE REAR bar to purchase..............which is a significant increase the rear oem stiffness [ 25%>32.5% if installed and coupled correctly].

You can also purchase the smaller diameter front bar and center support bushings. For the further 6.5% change most people skip this step as it is counterintuitive and they don't understand the benefits.

Active cars are rarer in the junk yards since only 15% of total 90-94Q were sold in US with that option [maybe 9,000 were sold].

Balancing the chassis: changing the gross understeer more towards neutral is MUCH MUCH MORE EFFECTIVE THAN 1-1.5" LOWERING SPRINGS which tend to carry/maintain the understeer rato except at the extremes and are aburpt [progressive] in the last 1" of rear compression.

The 24 mm solid [not available new anymore Stillen] rear bar could be manipulated to have the "dead zone" by using one or two rubber [out of 4] [urethane bushings supplied] on each end link.One inch of wheel movement translated to 1/4" of movement at the endlink attachment point so 1/8"/2= 1/16" of variable rubber squish per bushing..............hard to get right , harder to keep right but a pleasure between the weekly adjustment periods...........Perfection is hard to achieve and harder to maintain.

Hate the way Nissan chose to attach the bars [changed on the 2002 Q/M]...........not really stable in adjustments as the precision required was just too great for most ........a quarter of a turn on a nut was radical change!

Gives me something to do each week, tweek the bars to compensate for changes in the bushings......temperature and wear.

The rear sway is designed to warn/stop non professional drivers from out driving the tires they chose.A properly adjusted set of bars should be feelable in transistion, you should be able to feel the bars load up and resist the sway in even a 10degree change of steering wheel [the 90-92 rack ratio] maybe 15 degrees in the 94 and later racks.

[maxnix]

Wow, Rex, way to show the power of a good search!

Will you do all my future searches for me too? Please, please?

[JedCoop]

Yeah Rex, putting all that info in one place is great! I really appreciate it, and I learned something too.

[PopPop]

Already read these before as I said when Im started this post but, there are still a lot of questions un-answered! If you have a car with more HP and more Torque the even larger stillen bar would be even better for a person for weight transfer when racing! Someone like Wes, Rob, John D, and myself who often goes to the track would benefit from a larger rear Sway bar! This is the main question that I was concerned about! I know what's best for street application but, was wondering if someone could give a figure on what would be best front to rear ratio for cars making over 400 HP with appropriate Torque increases? If anyone can figure this out or has the formula for this please respond!

[Q45tech]

The more power you have and apply [in the instant] to rear tires the less reserve you have for turning.

If you have wider [235/245/255/265/275] and/or softer [oem 160 treadware index] than oem tires you can use a stiffer rear sway bar in dry weather.

Just don't use a rear bar stiffer than what ever rear springs you use

[elwesso]

If you want to control squat under hard acceleraiton its best to get a set of the subframe spacers like I have.....

[Rex]

If you want to control squat under hard acceleraiton its best to get a set of the subframe spacers like I have.....

I thought you were unhappy with the sub-frame spacers?

[elwesso]

Not at all!!!! I thought they were my source of vibration, but based on others accounts i highly doubt they are...

I should be doing a diff swap in the next month or so, which i hope will take care of it. if that doesnt work, im going to change ALL drivetrain mounts (engine, trans, and diff)

[Q45tech]

We installed the hard bushings on a 96 and the owner came back 3 days later and bought a new subframe.......Serious vibrations felt.

[RobertsnewQ]

I just installed a 20mm Active bar and I am VERY pleased with the difference in handling. I do need to replace my front swaybar bushings, so it may be more pronounced than I expected, but it is a nice change.

Anyway, before I actually got it, I never knew they were hollow!

[elwesso]

We installed the hard bushings on a 96 and the owner came back 3 days later and bought a new subframe.......Serious vibrations felt.

are you talking about the poly subframe bushings?

[Q45tech]

YES............awful [wheel/tire] vibration compared to a brand new oem subframe........of course this depends on road design, coarseness and compound........tire brand and type.

They used the two front silicone bushings for a reason.

[maxnix]

YES............awful [wheel/tire] vibration compared to a brand new oem subframe........of course this depends on road design, coarseness and compound........tire brand and type.

They used the two front silicone bushings for a reason.

Man, I love it when someone else experiments on their dollar!

[sicarius82]

bumpers