G50 Q45 active sway bars front and rear question
G50 Q45 active sway bars front and rear question
I've found a seller with an "active" Q that is willing to part the sway bars. I know I need the rears for better performance, so I'm interested in getting that. However do I actually need the fronts from the "active" Q, or is my base model Q sway bar the same as the "active" Q's front sway bar?
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maxnix
- Posts: 22627
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- Car: 1995 Infiniti Q45
1995 Infiniti Q45t
2000 Infiniti Q45
Re: G50 Q45 active sway bars front and rear question (SFBayQ45)
No the standard front is actually 1 mm thicker, so a little more understeer is dialed in.
Get both and replace the front when you replace the bushings.
Modified by maxnix at 3:16 PM 7/8/2008
Get both and replace the front when you replace the bushings.
Modified by maxnix at 3:16 PM 7/8/2008
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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
Re: G50 Q45 active sway bars front and rear question (maxnix)
A 1 mm thinner front sway bar has the same ratio changing effect as making a 20mm rear bar a 20.5mm rear bar. As far as the change in roll stiffness ratio is concerned.
13% softer front or 13% stiffer rear. Remember the front bar [and rear] are /act in parallel with springs so 13% softer front bar is ~~ 6.5% less stiff front in totality since springs don't change.
Remember the front bar is ~~ 180 lb/in [or 156 lb/in = 28mm] while rear 20mm is only 40 lb/in WHEN the bushings are final compressed after 1" of body roll. Hopefully you can see that the front bar then becomes ~4 times stiffer than the rear creating the understeer after 1".
Just adding a rear 20mm bar makes the rear eventually [after 1"] 32% stiffer but when the front bar starts working [after 1"] the front becomes 100% stiffer still have significant understeer just less.
To make the car 100% neutral [a dangerous situation if you accelerate in damp road conditions] after 1" body roll you would need a rear bar as stiff as the rear springs 123 lb/in or a combination of stiffer rear springs and bar ...................somewhere around 260-270 lb/in.
Eibach rear springs are progressive and can achieve 200 lb/in after a 2" roll so with a 20mm rear bar you can get might close 200+40 = 240 lb/in.But the Eibach stiffness from 1>2" is not 200 maybe 160.
Progressive rear springs can be very squirrely abd suddenly surprising in that you go from neutral to understeer to near neutral under extreme handling.
My old Q has had Eibach's and 28/20 mm sway bars for 14 years but I am use to the weirdness and think about it in advance every time it rains or I get frisky and back off a little in curves.
A stiffer than 20mm rear bar will/could/can reduce body roll so that the Eibach's never get compressed 3", so the 200 spring stiffness rate never occurs. Why Stillen made and sold a 24mm [120 lb/in] rear bar with urethane bushings and stronger end links for use with Eibach's springs.
Not for use with oem rear sized tires they sold an entire package with 255/50/16 or 255/45/17.
The above are math number [pretty accurate] but you must use scales and jacks to get the 100% real as installed roll stiffness in each increment of inches to see what bushings, and tires subtract from theory.
This is why race cars have adjustable from cockpit while driving methods to change the stiffness of rear sway bars as the tires change and the fuel is used dropping upto 125 pounds of rear weight.
13% softer front or 13% stiffer rear. Remember the front bar [and rear] are /act in parallel with springs so 13% softer front bar is ~~ 6.5% less stiff front in totality since springs don't change.
Remember the front bar is ~~ 180 lb/in [or 156 lb/in = 28mm] while rear 20mm is only 40 lb/in WHEN the bushings are final compressed after 1" of body roll. Hopefully you can see that the front bar then becomes ~4 times stiffer than the rear creating the understeer after 1".
Just adding a rear 20mm bar makes the rear eventually [after 1"] 32% stiffer but when the front bar starts working [after 1"] the front becomes 100% stiffer still have significant understeer just less.
To make the car 100% neutral [a dangerous situation if you accelerate in damp road conditions] after 1" body roll you would need a rear bar as stiff as the rear springs 123 lb/in or a combination of stiffer rear springs and bar ...................somewhere around 260-270 lb/in.
Eibach rear springs are progressive and can achieve 200 lb/in after a 2" roll so with a 20mm rear bar you can get might close 200+40 = 240 lb/in.But the Eibach stiffness from 1>2" is not 200 maybe 160.
Progressive rear springs can be very squirrely abd suddenly surprising in that you go from neutral to understeer to near neutral under extreme handling.
My old Q has had Eibach's and 28/20 mm sway bars for 14 years but I am use to the weirdness and think about it in advance every time it rains or I get frisky and back off a little in curves.
A stiffer than 20mm rear bar will/could/can reduce body roll so that the Eibach's never get compressed 3", so the 200 spring stiffness rate never occurs. Why Stillen made and sold a 24mm [120 lb/in] rear bar with urethane bushings and stronger end links for use with Eibach's springs.
Not for use with oem rear sized tires they sold an entire package with 255/50/16 or 255/45/17.
The above are math number [pretty accurate] but you must use scales and jacks to get the 100% real as installed roll stiffness in each increment of inches to see what bushings, and tires subtract from theory.
This is why race cars have adjustable from cockpit while driving methods to change the stiffness of rear sway bars as the tires change and the fuel is used dropping upto 125 pounds of rear weight.
Re: G50 Q45 active sway bars front and rear question (Q45tech)
Geez, I will just stick with the stock setup and keep it fresh and worry about other things!
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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
Re: G50 Q45 active sway bars front and rear question (qship96)
Why most people just install the rear 20mm bar and new Tokico shocks and bushings and say that's enough.
Squeezing out the last 0.05G in a slalom or 3 mph in a curve or cones requires some math and work.
Remember tires are 85% of what's possible and suspension is 10% at best.The last 5% depends on moon phases.
Squeezing out the last 0.05G in a slalom or 3 mph in a curve or cones requires some math and work.
Remember tires are 85% of what's possible and suspension is 10% at best.The last 5% depends on moon phases.
Re: G50 Q45 active sway bars front and rear question (Q45tech)
Right now I'm driving with no front sway bar because I found out the bushings are gone and torn on the left side... The car is comfortable but I was wondering if it would be better to go with a 29mm FSB with eibach springs/factory shocks I already have a 20mm rear sway bar.
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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
Re: G50 Q45 active sway bars front and rear question (Kiven422)
The Eibach front springs are LINEAR and ~~ 12.5% stiffer than oem:
146 vs 165 lb/in, so by using the 28mm [155 lb/in] bar you maintain oem front roll stiffness vs stock standard Q. The sum of the two [springs + bar] is ~~ 320 pound /inches after the bar compresses the bushings.
Remember the stock rear springs are 123 + 40 [for 20mm bar] =166 lb/in
This makes a 65% forward understeer bias for rear 20mm vs a 76% without rear bar
55% would be perfectly NEUTRAL until you try to accelerate [wet could be fatal] then the rear tires would lose grip and oversteer.
Hopefully you can see what I'm promoting split the difference between oem and disaster
146 vs 165 lb/in, so by using the 28mm [155 lb/in] bar you maintain oem front roll stiffness vs stock standard Q. The sum of the two [springs + bar] is ~~ 320 pound /inches after the bar compresses the bushings.
Remember the stock rear springs are 123 + 40 [for 20mm bar] =166 lb/in
This makes a 65% forward understeer bias for rear 20mm vs a 76% without rear bar
55% would be perfectly NEUTRAL until you try to accelerate [wet could be fatal] then the rear tires would lose grip and oversteer.
Hopefully you can see what I'm promoting split the difference between oem and disaster