Hi, all.
Infinitipartsusa.com has an item in their on-line catalog called a "Rear Stabilizer Kit" for a Q45 (from 1990 to 1996). The words in the description read
"Factory upgraded rear stablizer bar kit from the Active suspension models. This kit includes ALL parts needed to do the job."
Has anyone installed this in a Q (of course one without active suspension)? With good results?
The price shown is pretty good for the kit: $236.93 plus shipping and handling and tax and. If everything is included, this sounds like a good deal!
Z
Any experience with "Rear Stabilizer Kit" from Infinitipartsusa.com?
Re: Any experience with "Rear Stabilizer Kit" from Infinitipartsusa.com?
szhosain wrote:Hi, all.
Infinitipartsusa.com has an item in their on-line catalog called a "Rear Stabilizer Kit" for a Q45 (from 1990 to 1996). The words in the description read
"Factory upgraded rear stablizer bar kit from the Active suspension models. This kit includes ALL parts needed to do the job."
Has anyone installed this in a Q (of course one without active suspension)? With good results?
The price shown is pretty good for the kit: $236.93 plus shipping and handling and tax and. If everything is included, this sounds like a good deal!
Z
I installed one on my 95. It does have everything you need and is easy to install. With air tools, it goes on in under an hour since all the necessary holes are already there. It doesn't have instructions though (at least when I bought it) and if you've never installed a sway bar before, you'll want to figure out how the end links, bushings and washers all fit together before getting under the car since there are a lot of pieces. I didn't notice a huge difference in the balance of the car although I didn't really expect to with "normal" driving. It is easier to spin the inside tire exiting corners, which is one of the downsides of a rear roll bar. I'd like to take my car on a skidpad before I replace the tires to see how it affects the balance of the car. My 93 without a rear sway bar was very determined to understeer no matter what I did with the throttle.
When I bought the kit, they didn't invoice or send the bolts to mount the brackets to the body. When I asked, they sent them free. Later, I discovered that they sent shock busings instead of stabilizer-bar bushings. When I asked about that, they assured me that the shock bushings were sufficient.
Dennis differs as to the appropriateness of the shock bushings -- I'm caught in the middle. Bar-bushings are considerably more expensive, but dimensionally, nearly identical. I may go straight to urethane.
Installing the bar means dropping part of the exhaust. I have the parts, but priorities have put me off.
Dennis differs as to the appropriateness of the shock bushings -- I'm caught in the middle. Bar-bushings are considerably more expensive, but dimensionally, nearly identical. I may go straight to urethane.
Installing the bar means dropping part of the exhaust. I have the parts, but priorities have put me off.
i got it too, also missing the bolts to mount the bracket on the frame, but i used some bolts i had. easy to do, except i had to take a most the exhaust hangers for the tailpipes off, but that's because i don't have the stock exhaust. also installed front strut tower brace from stillen. virtually no body roll even with my worn shocks.
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Q45tech
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1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Members must realize that microscopic slack in the system is cumlative. 1/4" is tremendous as the bar will do nothing for the first 1" of roll [and 3.5-4.0" of roll is all you have].
If you have 4 bushings on each end link and the 2 support center bushings thats allows 0.25/10 or 0.025" of deflection on each bushing. Metal washers between the bar and bushings and additional washers between the top and bottom nuts will allow more than the stock compession allowing the bar to be set precisely and to start acting sooner than stock.
All in all urethane on the end links and rubber on the center supports is probably a good thing.
If the car does not sit level you must remove the preload from the bar to avoid differential side to side handling!
The whole system is designed to startout on the springs alone then progressive bring the front bar into play to increase understeer as the g forces rise.....1,1.5,2.0,2.5 inches of roll so the addition of the rear bar just slows down the amount of relative front to rear stiffness.The front bar can be as stiff as the front springs [depending on the front bushing deflection.A 24 mm rear bar would be needed to equal the rear springs [which with urethane bushings might gain stiffness faster than the front with its 2x2+2 = 6 rubber bushings.Urethane on the 20mm {rear A bar} is ok since the stock front [non A or T bar is 29mm].Again even urethane has some give [1/10 of rubber] as noted from the wear I've seen on the Urethane bushings on some Q.
Lots of Q's use soft single ply sidewall tires and the results with a rear bar will be much less noticable as the tires roll over from the 10% extra g force.
If your stock rear shocks have more than 30,000 miles on them they probably won't have enough reserve left to control the spring like action of a 20 mm much less a 24 mm rear bar!The blue shocks can make it to 60k unless lowering springs are used.
If you have 4 bushings on each end link and the 2 support center bushings thats allows 0.25/10 or 0.025" of deflection on each bushing. Metal washers between the bar and bushings and additional washers between the top and bottom nuts will allow more than the stock compession allowing the bar to be set precisely and to start acting sooner than stock.
All in all urethane on the end links and rubber on the center supports is probably a good thing.
If the car does not sit level you must remove the preload from the bar to avoid differential side to side handling!
The whole system is designed to startout on the springs alone then progressive bring the front bar into play to increase understeer as the g forces rise.....1,1.5,2.0,2.5 inches of roll so the addition of the rear bar just slows down the amount of relative front to rear stiffness.The front bar can be as stiff as the front springs [depending on the front bushing deflection.A 24 mm rear bar would be needed to equal the rear springs [which with urethane bushings might gain stiffness faster than the front with its 2x2+2 = 6 rubber bushings.Urethane on the 20mm {rear A bar} is ok since the stock front [non A or T bar is 29mm].Again even urethane has some give [1/10 of rubber] as noted from the wear I've seen on the Urethane bushings on some Q.
Lots of Q's use soft single ply sidewall tires and the results with a rear bar will be much less noticable as the tires roll over from the 10% extra g force.
If your stock rear shocks have more than 30,000 miles on them they probably won't have enough reserve left to control the spring like action of a 20 mm much less a 24 mm rear bar!The blue shocks can make it to 60k unless lowering springs are used.
911/Q45 wrote:I doubt that strut brace does much, but it was cheap, easy to install and pretty studly looking under the hood!
You're correct. Strut tower braces have no effect on body roll, and are of very limited usefulness on a car without struts (and it's debateable they do much even on a strut equipped car).
Now that somebody mentioned it, mine was missing the bolts for the center mounts too. Unfortunately, I have forgetten the necessary size/pitch.
I'll have to try adding additional washers one of these days now that the bushings have been compressed for awhile. I could barely get the nuts started on the end links with the stock washers. There's no way additional ones would have been put on at first.
I put the kit in in late August. Everything was included and the installation was simple. I was able to lift the car and remove the wheels so I didn't have to drop the exhausts.
You will notice a difference. With the stock bushings, the car takes a two stage set in a turn (Q45Tech's 1/4 inch of play causes that). Adding the stiffer bushings will limit the effect.
In looser footing, the rear bar will allow the limited slip to really bite. Look out for big understear in slow speed corners in the rain!
You will notice a difference. With the stock bushings, the car takes a two stage set in a turn (Q45Tech's 1/4 inch of play causes that). Adding the stiffer bushings will limit the effect.
In looser footing, the rear bar will allow the limited slip to really bite. Look out for big understear in slow speed corners in the rain!
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Q45tech
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1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Remember the springs are set up just right [54.4 vs 45.6] for the difference in front rear weight [assuming nothing in the trunk, half a tank of gas, and a 170 pound driver] so the front bar is what causes the understeer [while limiting body roll] and a rear bar helps remove some of it [understeer] by decreasing some of the excess rear traction. Understeer by definition means the rear has more [handling] traction [less tread slip] than the front!!!!!!!!!
The counterintuitive approach is to soften the front bar [a little] as you add or stiffen a rear bar........exactly what they do progressively on the Q45t and Q45a [the benefit is less impact harshness on the front from a softer bar over bumps]. But more on the rear!
You have your choice of 54.4% to 71% front roll ratio stiffness and every minute decimal point in between by mix and matching factory components [plus an assortment of urethane or rubber bushings and metal washers].
Be careful of Eibach springs since the rears are progressive vs the front which are linear. A lowered car will have a sudden decrease in understeer as the rear rolls from 2 to 3"......they are trying to do you a favor but don't just expect that the rear are 122 x 115%~~140 for every inch including the last one [125, 160, 200]......they actual increase the understeer in the first inch, decrease it in the second inch, and greatly decrease it in the 3rd inch.........They don't know how far you are going with your suspension mods so they try to make the springs feel like they are doing something besides just lowering the car.
Thanks for pointing out the two step feel of the Q --------this is designed to keep untrained drivers out of trouble.....body roll, more body roll hey dumbo slow down........the new BMW 745 shuts down the active roll bar system in rain [sensor] at 0.7 [dry]to 0.35 G [real wet/snow] depending on conditions and the learned response of WHICH drivers key is installed.
Maybe they should give you a two day driving course and give you programming to match you skill level!
The problem is sorting out the improved FEEL [from reduced roll] from the actual G cornering increase!
Don't expect miracles as 95% of the handling is tire selection related [vs the loaded weight] and 5% is the suspension ASSUMING that the alignment is set ABSOLUTELY CORRECT....bad alignment can reduce the tire capability by 10% or more [not to mention weird wear]!
Setting up suspension for a smooth racetrack is much easier than having one which can deal with normal city streets and highways......tracks don't have bumps and potholes.
Study tire racks suspension and tire tests you'll notice that from the Worst [BMW] stock to the best combination is not 10% improvement in track times.I'm sure a really obscene condition Q could be 20% worse than the best ones.
The point is suspension mods should not be attempted without understanding the trade offs .......each little thing might make a 1% change to the good or bad
The counterintuitive approach is to soften the front bar [a little] as you add or stiffen a rear bar........exactly what they do progressively on the Q45t and Q45a [the benefit is less impact harshness on the front from a softer bar over bumps]. But more on the rear!
You have your choice of 54.4% to 71% front roll ratio stiffness and every minute decimal point in between by mix and matching factory components [plus an assortment of urethane or rubber bushings and metal washers].
Be careful of Eibach springs since the rears are progressive vs the front which are linear. A lowered car will have a sudden decrease in understeer as the rear rolls from 2 to 3"......they are trying to do you a favor but don't just expect that the rear are 122 x 115%~~140 for every inch including the last one [125, 160, 200]......they actual increase the understeer in the first inch, decrease it in the second inch, and greatly decrease it in the 3rd inch.........They don't know how far you are going with your suspension mods so they try to make the springs feel like they are doing something besides just lowering the car.
Thanks for pointing out the two step feel of the Q --------this is designed to keep untrained drivers out of trouble.....body roll, more body roll hey dumbo slow down........the new BMW 745 shuts down the active roll bar system in rain [sensor] at 0.7 [dry]to 0.35 G [real wet/snow] depending on conditions and the learned response of WHICH drivers key is installed.
Maybe they should give you a two day driving course and give you programming to match you skill level!
The problem is sorting out the improved FEEL [from reduced roll] from the actual G cornering increase!
Don't expect miracles as 95% of the handling is tire selection related [vs the loaded weight] and 5% is the suspension ASSUMING that the alignment is set ABSOLUTELY CORRECT....bad alignment can reduce the tire capability by 10% or more [not to mention weird wear]!
Setting up suspension for a smooth racetrack is much easier than having one which can deal with normal city streets and highways......tracks don't have bumps and potholes.
Study tire racks suspension and tire tests you'll notice that from the Worst [BMW] stock to the best combination is not 10% improvement in track times.I'm sure a really obscene condition Q could be 20% worse than the best ones.
The point is suspension mods should not be attempted without understanding the trade offs .......each little thing might make a 1% change to the good or bad
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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
Getting a stock Q from 0.65-0.69G to 0.75 G is easy [$1500] going to 0.8G [like the new G35 is hard [due to extra 600 pounds] maybe $3,000. A 0.85G Q would be extremely unbareably hard on the street [$5,000] and body redesign to add 27-28" tires and somehow removing 300 pounds. Off course you could run special very very soft Slalom slick tires but they would be worthless on the street without treads and you would need rain tires and change them daily.
Getting it to 0.9G like an M3 or Corvette is impossible.
Getting it to 0.9G like an M3 or Corvette is impossible.
Absolute maximum lateral acceleration on the street is a pretty meaningless number (.8 or .9 Gs). For most of us, transition response and turn-in are the most noticable.
Transition response is a function of sway bar coupling, tire selection, and total mass of the vehicle. The first two are within our control. Not much we can do about the last. If you want to feel transition response at its best (and you can't find a Fourmula Ford) try a well set up Miata. Generaly good transition response will involve long suspension travel, softer springs, stiffer shocks, and heavy sway bars. A Q with minor tweaking and sticky tires can have excellent transition response. Or as good as 4400lbs can get.
Turn-in is a different matter. It is a factor of front geometry (The Q is pretty good here. Stiffer bushings help keep it stable and make the car ride like a farm wagon.), sway bar tuning (Luckily, if you optimise for transition response, your turn-in will be good), tire selection (No rules. Each tire brand and model is different. The same brand and model of tire will be different in different sizes. And the stability of each tire will vary with changing milage, temperature, and pressure. No rules. If you find one you like, stick with it.), and rear tracking.
Rear tracking is where the Q seems to be falling down. I find it almost impossible to get this thing to rotate in medium speed turns. Once you take the car's mass into account, this thing feels just like my 300ZXTT. Brake early, turn in early, let the suspension take a set, then power through the apex and out of the turn. I ended up killing off the ZXs HICAS just to get the thing to turn. There must be a TON of rear stear built into the Q, even without HICAS.
Sorry. This really was not intended to be meaningless rambling. Just the usual frustration of taking a good car with real potential and trying to find just the right setup. Unfortunately, "just the right setup" depends as much on individual tastes and driving style as on parts on the car.
Transition response is a function of sway bar coupling, tire selection, and total mass of the vehicle. The first two are within our control. Not much we can do about the last. If you want to feel transition response at its best (and you can't find a Fourmula Ford) try a well set up Miata. Generaly good transition response will involve long suspension travel, softer springs, stiffer shocks, and heavy sway bars. A Q with minor tweaking and sticky tires can have excellent transition response. Or as good as 4400lbs can get.
Turn-in is a different matter. It is a factor of front geometry (The Q is pretty good here. Stiffer bushings help keep it stable and make the car ride like a farm wagon.), sway bar tuning (Luckily, if you optimise for transition response, your turn-in will be good), tire selection (No rules. Each tire brand and model is different. The same brand and model of tire will be different in different sizes. And the stability of each tire will vary with changing milage, temperature, and pressure. No rules. If you find one you like, stick with it.), and rear tracking.
Rear tracking is where the Q seems to be falling down. I find it almost impossible to get this thing to rotate in medium speed turns. Once you take the car's mass into account, this thing feels just like my 300ZXTT. Brake early, turn in early, let the suspension take a set, then power through the apex and out of the turn. I ended up killing off the ZXs HICAS just to get the thing to turn. There must be a TON of rear stear built into the Q, even without HICAS.
Sorry. This really was not intended to be meaningless rambling. Just the usual frustration of taking a good car with real potential and trying to find just the right setup. Unfortunately, "just the right setup" depends as much on individual tastes and driving style as on parts on the 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
Rear steer - hopefully the rear suspension bushings are still in good shape and all you get is the Designed toe in out changes from acceleration and deceleration.Now in a decelerating curve there is some difference between sides if you are not at the proper entry angle but the toe differences should be slight compared to the tire slip angles [from non performance tires].
Set the rear toe to perfect [sitting still] and at 60 mph there is zero toe [to reduce tire scrub friction and improve mpg]. When you let off, brake,etc there is more than the static toe in set up....the faster you brake the more rear toe in.....to help plant the rear and aid in deceleration.
Getting the Q rear to rotate is a matter of finding shocks that work [remember the rebound rate is [should be] more than twice the compression. The rebound wears faster than compression so the opposite shock really controls the roll rate.
The factory rears are gone [rebound] by 40k or sooner.Many adjustable shocks only adjust rebound because the compression rate is a narrow function of the spring stiffness and weight on the spring to achieve optimum just slightly underdamped.
Many inexpensive non adjustable aftermarket shocks add compression stiffness but pass on adding much rebound.....as most equate a stiff compression to a better shock [not true in most cases].
Anyone tried using aftermarket adjustable 300zxtt rear shocks they are an approximate fit with modifications.
Set the rear toe to perfect [sitting still] and at 60 mph there is zero toe [to reduce tire scrub friction and improve mpg]. When you let off, brake,etc there is more than the static toe in set up....the faster you brake the more rear toe in.....to help plant the rear and aid in deceleration.
Getting the Q rear to rotate is a matter of finding shocks that work [remember the rebound rate is [should be] more than twice the compression. The rebound wears faster than compression so the opposite shock really controls the roll rate.
The factory rears are gone [rebound] by 40k or sooner.Many adjustable shocks only adjust rebound because the compression rate is a narrow function of the spring stiffness and weight on the spring to achieve optimum just slightly underdamped.
Many inexpensive non adjustable aftermarket shocks add compression stiffness but pass on adding much rebound.....as most equate a stiff compression to a better shock [not true in most cases].
Anyone tried using aftermarket adjustable 300zxtt rear shocks they are an approximate fit with modifications.
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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
""Compression controls the motion of the unsprung weight. Rebound controls the motion of the sprung weight.
If the car has too much shock the ride will be harsh and will not absorb road irregularities. Too much bump and the car slides, rather than sticks; too much rebound and the wheels will not return quickly to the road surface and the car may "jack down" over long corners.
Soft shocks allow the suspension to move fast enough to keep the tire in contact with the road. But too little shock and the car floats, oscillates, dives, rolls and feels generally unresponsive.
Jacking down is a situation that occurs when the shock, after hitting a bump and compressing the spring, does not allow the spring to return to its neutral position before the next bump.
Repeated bumps will lower the car, there will be a dramatic increase in roll stiffness and the car will understeer or oversteer depending which end is effected. Adjust for bump (compression) first.
Bump controls the upward movement of the suspension when hitting a bump. It should not be used to control downward movements, roll or bottoming. Bump is set when "side hop" or "walking" in a bumpy corner is minimal and the ride is not overly harsh. The car should feel positive on turn in. If bump is too soft the nose will dive under braking.
Rebound adjustments has the greater effect on the drivers feel of the car. Rebound controls roll and lean when entering or exiting a corner and limits how fast the motion occurs. Rear shock rebound effects corner entry, front shock rebound effects corner exit.
Set rebound for smooth entry without excessive leaning. The driver can set the rebound for their preference of oversteer or understeer in corner entry without effecting corner exit.
Too much rebound will cause initial loss of lateral acceleration (understeer or oversteer depending which end) and will lead to jacking down. Shocks will control the timing of this motion.
Shock rates are a measurement of resistance, determined by the movement of the piston inside the shock body. Stiff shocks slow down the motion and speed up the rate of transfer. Soft shocks allow the suspension to respond quickly and slow the rate of transfer. The total amount (weight) transferred is determined by the spring. "
http://thundervalleyracing.com....html
If the car has too much shock the ride will be harsh and will not absorb road irregularities. Too much bump and the car slides, rather than sticks; too much rebound and the wheels will not return quickly to the road surface and the car may "jack down" over long corners.
Soft shocks allow the suspension to move fast enough to keep the tire in contact with the road. But too little shock and the car floats, oscillates, dives, rolls and feels generally unresponsive.
Jacking down is a situation that occurs when the shock, after hitting a bump and compressing the spring, does not allow the spring to return to its neutral position before the next bump.
Repeated bumps will lower the car, there will be a dramatic increase in roll stiffness and the car will understeer or oversteer depending which end is effected. Adjust for bump (compression) first.
Bump controls the upward movement of the suspension when hitting a bump. It should not be used to control downward movements, roll or bottoming. Bump is set when "side hop" or "walking" in a bumpy corner is minimal and the ride is not overly harsh. The car should feel positive on turn in. If bump is too soft the nose will dive under braking.
Rebound adjustments has the greater effect on the drivers feel of the car. Rebound controls roll and lean when entering or exiting a corner and limits how fast the motion occurs. Rear shock rebound effects corner entry, front shock rebound effects corner exit.
Set rebound for smooth entry without excessive leaning. The driver can set the rebound for their preference of oversteer or understeer in corner entry without effecting corner exit.
Too much rebound will cause initial loss of lateral acceleration (understeer or oversteer depending which end) and will lead to jacking down. Shocks will control the timing of this motion.
Shock rates are a measurement of resistance, determined by the movement of the piston inside the shock body. Stiff shocks slow down the motion and speed up the rate of transfer. Soft shocks allow the suspension to respond quickly and slow the rate of transfer. The total amount (weight) transferred is determined by the spring. "
http://thundervalleyracing.com....html
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Q45tech
- Moderator
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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
http://members.aol.com/sccacuda/cars/adjshk1.html
Something I didn't know is that the elastic modulus of steel coil springs changes 2.2% for a 10F temperature increase, assumming things are measured at 68-72F summer can change the rates by 10% softer and winter by 10% stiffer.The above is in addition to the viscosity [and nitrogen pressure] changes of the shocks with temperature which are also at least +-10%.
So at 90F outside what is your spring shock temperature and how does it vary with road roughness .......at least 15% softer and in winter at least 20% stiffer.
http://members.aol.com/sccacuda/cars/1SmthTa.html
http://e30m3performance.com/te...k.htm
the above shows how little compression is used on a rear shock so how can you test a shock by simply pushing down, you need 2- 300 pound half backs to simultaneously pull the rear up fast!!!
Something I didn't know is that the elastic modulus of steel coil springs changes 2.2% for a 10F temperature increase, assumming things are measured at 68-72F summer can change the rates by 10% softer and winter by 10% stiffer.The above is in addition to the viscosity [and nitrogen pressure] changes of the shocks with temperature which are also at least +-10%.
So at 90F outside what is your spring shock temperature and how does it vary with road roughness .......at least 15% softer and in winter at least 20% stiffer.
http://members.aol.com/sccacuda/cars/1SmthTa.html
http://e30m3performance.com/te...k.htm
the above shows how little compression is used on a rear shock so how can you test a shock by simply pushing down, you need 2- 300 pound half backs to simultaneously pull the rear up fast!!!
It sounds like we are bumping into the same problem most weekend racers run into. About the only way we have to describe what your car is doing is with terms that only mean something to the person using them. Jacking, bite, rotation, two stage set. I know what I am trying to describe, but I doubt if anyone else does. One critical skill a successfull driver has is the ability to convey EXACTLY what the car is doing to his engineers. Very few drivers develop that ability.
I am very happy with the way I have this car set up. Its a daily driver and I put 25K to 30K a year on it. Its a 94 Q, basic setup, no HICAS (A good thing in my opinion), the Active rear sway bar, nylon bushings on the sway bars, Tokico Blues front and rear, 245/45-16s AVS Intermediates on 16x8.5 wheels.
Steady state cornering is great. Going 7 tenths through the back roads with no heavy braking and this car is great!
Push harder with heavy braking intering a corner and this car WILL NOT rotate. From just before the apex to the exit, this car romps (2and gear, 4500 rpm, power oversteer offset by LSD induced understeer). This thing must have some big rear toe-in under heavy braking. Its like the rear wants to turn more than the front. I don't want less rear sway bar, the car's steady state cornering is too good to loose.
How much bushing induced rear toe-in does this car have? Maybe stiffer concentric bushings will help.
I am very happy with the way I have this car set up. Its a daily driver and I put 25K to 30K a year on it. Its a 94 Q, basic setup, no HICAS (A good thing in my opinion), the Active rear sway bar, nylon bushings on the sway bars, Tokico Blues front and rear, 245/45-16s AVS Intermediates on 16x8.5 wheels.
Steady state cornering is great. Going 7 tenths through the back roads with no heavy braking and this car is great!
Push harder with heavy braking intering a corner and this car WILL NOT rotate. From just before the apex to the exit, this car romps (2and gear, 4500 rpm, power oversteer offset by LSD induced understeer). This thing must have some big rear toe-in under heavy braking. Its like the rear wants to turn more than the front. I don't want less rear sway bar, the car's steady state cornering is too good to loose.
How much bushing induced rear toe-in does this car have? Maybe stiffer concentric bushings will help.
oops!!
Just went back and re-read Q45Tech's post at the end of the last page. Edit the above as appropriate. Sorry.
Under full braking, I get the feeling that the rear shocks are way into rebound and there is LOTTS of toe-in. Add in the initial body roll from the first steering input and the rear wants to turn more than the front. As the rear bushings age and wear, do they allow the designed in toe-in to show up sooner?
I will look into the 300ZXTT shocks. There is every imaginable compression and rebound setting available in the aftermarket.
Just went back and re-read Q45Tech's post at the end of the last page. Edit the above as appropriate. Sorry.
Under full braking, I get the feeling that the rear shocks are way into rebound and there is LOTTS of toe-in. Add in the initial body roll from the first steering input and the rear wants to turn more than the front. As the rear bushings age and wear, do they allow the designed in toe-in to show up sooner?
I will look into the 300ZXTT shocks. There is every imaginable compression and rebound setting available in the aftermarket.
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greg_atlanta
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- Car: 2008 G35 Journey Sedan, silver/black (no sunroof), 1992 Q45 (in a past life)
JUST DO IT!!!
Biggest advantage is sharper steering, esp. at highway speeds.
I have 23mm stillen bar with urethane bushings (recent addition)... some say it's too harsh, but I think I'd be happier if it were stiffer. Very little negative impact on ride, very positive impact on so many other things!
Rear end bites better and easier to have fun, spin tires, fishtail.......
Biggest advantage is sharper steering, esp. at highway speeds.
I have 23mm stillen bar with urethane bushings (recent addition)... some say it's too harsh, but I think I'd be happier if it were stiffer. Very little negative impact on ride, very positive impact on so many other things!
Rear end bites better and easier to have fun, spin tires, fishtail.......
reggiegsd wrote:
Push harder with heavy braking intering a corner and this car WILL NOT rotate. From just before the apex to the exit, this car romps (2and gear, 4500 rpm, power oversteer offset by LSD induced understeer). This thing must have some big rear toe-in under heavy braking. Its like the rear wants to turn more than the front. I don't want less rear sway bar, the car's steady state cornering is too good to loose.
How much bushing induced rear toe-in does this car have? Maybe stiffer concentric bushings will help.
I'd guess you're probably right. I used to own an AWD Talon, that had passive rear steering built into the trailing arm via a bushing that created lots of toe in under load. To get the car to handle properly, and rotate predictably, you have to weld the trailing arm to eliminate the compliance. If you increased rear roll stiffness enough to compensate for the toe-in, the car was WAY too loose on transitional stuff. Rear wheel steering in either passive or active form is just plain evil.
I've never had my 95 on a skidpad or racetrack, but my 93 understeered badly at the limit no matter what I did with the thottle or brakes. I'm giving some thought to taking my 95 up to a track event next month to see how it does. Brakes will be a big problem, so I'll have to take it easy on them. I'll report back later if I do.
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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
At different speeds on different curves the side forces are different. It is impossible to make a non active suspension perfect at more than one speed or g force. Why NASCAR has such an easy time of it ---always turning left and always at roughly the same speed. Each track has its own set of adjustments.
The factory Q was set for the average driver in average situations.Understeer is the name of the game and all my mods are designed to reduce it.
The front sway bar is what causes all of it [except for that caused by the 54% front weight - making the front tires slip more than the rear]. The spring ratio is perfectly balanced to the weight distribution so just 4% understeer. As the roll starts to take up the slack on the front bar bushings the understeer increases as the front bar starts to resist the roll. The slack is set with new bushings by the fact that the bar link has only so many threads [to not allow the bushings to be overly compressed]. As the bushings wear the slack gets worse, allowing the car to be more neutral until a higher and higher roll angle as the space [slack] gets worse. Opposite of what most think as far as the understeer relationship.
Installing urethane bushings on the front will make the understeer worse [as the bar engages with no slack and could almost immediately raise the understeer by 20% to a peak roll stiffness of 70%] [instead of something like 64% with the rubber and slack]..............and the ride [impact over small bumps] becomes much worse.Before you do anything on the front install a strut tower brace [as the tower twist and movement is significant which changes the camber]. The extra camber causes the load wheel to go more negative and reduce its traction making the understeer worse.
Installing a smaller 28 mm front bar reduces the roll resistance by 4-5% [assumming same bushings] and reduces the understeer by the same amount at full roll. [which gets 0.16" worse]If you have a rear bar it [smaller front bar] is the functional equivalent of making it [the rear bar] slightly stiffer.
The 5% front reduction and the 11% rear increase makes the Q45t handle better [0.02-0.03 G's]. There is a limit to the trick of softening the front and stiffening the rear.........whenever the static weight balance becomes equal.....shifting say 172 pounds of roll stiffness to the rear over and above that added by the front bar...............Eibach rear springs [at full 3" compression as they are progressive] and a 24 mm rear bar with urethane on a Q45t with a smaller front bar and rubber bushings is as close to neutral as you can get in the dry............too close for me since I have been known to not slow down in the wet.
The factory Q was set for the average driver in average situations.Understeer is the name of the game and all my mods are designed to reduce it.
The front sway bar is what causes all of it [except for that caused by the 54% front weight - making the front tires slip more than the rear]. The spring ratio is perfectly balanced to the weight distribution so just 4% understeer. As the roll starts to take up the slack on the front bar bushings the understeer increases as the front bar starts to resist the roll. The slack is set with new bushings by the fact that the bar link has only so many threads [to not allow the bushings to be overly compressed]. As the bushings wear the slack gets worse, allowing the car to be more neutral until a higher and higher roll angle as the space [slack] gets worse. Opposite of what most think as far as the understeer relationship.
Installing urethane bushings on the front will make the understeer worse [as the bar engages with no slack and could almost immediately raise the understeer by 20% to a peak roll stiffness of 70%] [instead of something like 64% with the rubber and slack]..............and the ride [impact over small bumps] becomes much worse.Before you do anything on the front install a strut tower brace [as the tower twist and movement is significant which changes the camber]. The extra camber causes the load wheel to go more negative and reduce its traction making the understeer worse.
Installing a smaller 28 mm front bar reduces the roll resistance by 4-5% [assumming same bushings] and reduces the understeer by the same amount at full roll. [which gets 0.16" worse]If you have a rear bar it [smaller front bar] is the functional equivalent of making it [the rear bar] slightly stiffer.
The 5% front reduction and the 11% rear increase makes the Q45t handle better [0.02-0.03 G's]. There is a limit to the trick of softening the front and stiffening the rear.........whenever the static weight balance becomes equal.....shifting say 172 pounds of roll stiffness to the rear over and above that added by the front bar...............Eibach rear springs [at full 3" compression as they are progressive] and a 24 mm rear bar with urethane on a Q45t with a smaller front bar and rubber bushings is as close to neutral as you can get in the dry............too close for me since I have been known to not slow down in the wet.
The more I play with this suspension, the more I like it.
Have any members done research on the 300ZX suspension. It appears many of the components are either interchangable or very close to it. The after market makes virtually every piece of the ZX suspension in adjustable or static versions. Adjustable sway bars, front and rear upper links, tension compression rods, electricly adjustable shocks, and such. Has anyone really looked to see what fits and what doesn't?
Have any members done research on the 300ZX suspension. It appears many of the components are either interchangable or very close to it. The after market makes virtually every piece of the ZX suspension in adjustable or static versions. Adjustable sway bars, front and rear upper links, tension compression rods, electricly adjustable shocks, and such. Has anyone really looked to see what fits and what doesn't?
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OhTwoAltimaSE
- Posts: 11
- Joined: Wed Aug 28, 2002 7:03 am
palmerwmd wrote:A couple of members have this installed, including Q45tech, though I suspect he had his own sources.I also have a rear stabilizer though I am unsure if its the exact one as the "a" model or a different version, as the previous owner installed it.
Fred...
Fred,
you have the 24mm bar from EGR Goldrush. They are no longer produced. Stillen also resold this bar, but does not any longer.
I put a "T" bar on first, and that helped, but the difference is night and day between the two.
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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
Again the suspension can only do so much even if you spend $5,000 for mods. Assuming you don't change the pickup points.Tires are 90% of what's possible without weight reduction and the range from best to worst tires in standard sizes [26" diameter] is not 10%. Larger diameter tires will help the most but you have a hard time fitting much more than 26.5-27".
Lots of adjustments will [could] make the handling worse while feeling better.
In the last 10 years 4,000 pound cars have not improved much as once the setup is right [correct] little can be done.
It's ashamed that owners of Q45a wouldn't put up with the repair/maintenance costs to keep the cars operating as designed.But it has been the same with all makes who tried something similar. I'm sure they would have kept redesigning it lighter and better.
Lots of adjustments will [could] make the handling worse while feeling better.
In the last 10 years 4,000 pound cars have not improved much as once the setup is right [correct] little can be done.
It's ashamed that owners of Q45a wouldn't put up with the repair/maintenance costs to keep the cars operating as designed.But it has been the same with all makes who tried something similar. I'm sure they would have kept redesigning it lighter and better.
I have a 22mm custom bar with Energy Suspension urethane (red) bushings. I really, really like the way the car handles now. As soon as I get them installed, I tested it around the rotary and boy does it make a big difference. I had a 20mm active bar and the improvement was nice. Coming from a 15mm standard bar the difference would be huge!
BTW, I was selling some of these bars but I no longer have any available. Sorry guys.
I hope some of the folks who purchased this bar will chime in with their feelings about the 22mm bar and urethane bushings.
BTW, I was selling some of these bars but I no longer have any available. Sorry guys.
I hope some of the folks who purchased this bar will chime in with their feelings about the 22mm bar and urethane bushings.
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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
The 22 vs 20 bar is double or about 40 extra pounds [around 80 total per inch] per inch of body roll.Remember the rear springs are 122 per inch so the 22 mm would still be in the very safe zone of the bar not being as stiff or stiffer than the springs-------roughly a third less.
The 22mm rear with urethane will mean the rear roll stiffness is 200 vs the front 146 [before the front bar engages] so it will oversteer slightly in the first inch of body roll, go neutral in the 2nd inch and transition to understeer in the 3rd inch............really a function of how tight the front bar is!
One could shim the front bar to engage faster than stock by 1/16-1/8" so it would produce a balanced steer at 1"......tough to get it right half a turn at a time. You roughly want the front bar to move 0.36-0.4" in a total of 3" body roll instead of a full 0.75" if the front was connected without a rubber bushing.
I know this is complicated and impossible to do in the real world but you have to understand the art of fine tuning and how minute changes will affect the front.
Just shows you the variation in stock Q possible with the front sway bar 2 end link bushings alone [good to bad, tight to loose]......15-40% or more variation in front sway and propensity to understeer more or less. Couple this with tires and shocks and you see the possibilites!
Most more modern designs use a less stiff bar and couple it to the strut directly instead of the middle of the suspension arms decreasing the bushing sensitivity by 1/4 reducing variations to 4-10% good to bad bushing!
The 22mm rear with urethane will mean the rear roll stiffness is 200 vs the front 146 [before the front bar engages] so it will oversteer slightly in the first inch of body roll, go neutral in the 2nd inch and transition to understeer in the 3rd inch............really a function of how tight the front bar is!
One could shim the front bar to engage faster than stock by 1/16-1/8" so it would produce a balanced steer at 1"......tough to get it right half a turn at a time. You roughly want the front bar to move 0.36-0.4" in a total of 3" body roll instead of a full 0.75" if the front was connected without a rubber bushing.
I know this is complicated and impossible to do in the real world but you have to understand the art of fine tuning and how minute changes will affect the front.
Just shows you the variation in stock Q possible with the front sway bar 2 end link bushings alone [good to bad, tight to loose]......15-40% or more variation in front sway and propensity to understeer more or less. Couple this with tires and shocks and you see the possibilites!
Most more modern designs use a less stiff bar and couple it to the strut directly instead of the middle of the suspension arms decreasing the bushing sensitivity by 1/4 reducing variations to 4-10% good to bad bushing!
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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
The 97 and later Q use this method [of reducing bushing play sensitivity] by lengthening the front sway bar 90 deg. arm from 6" to 22" and connecting it to the lower strut mount with only one isolated joint. The effect is roughly the same, in that the bar's wheel rate is close to that of the 90-96 Q except it is linear from the beginning.Due to slightly lower front weight the springs and bar are slightly softer than the 94-96.
The 97 Q rear sway bar is slightly narrower [due to tread width] so it is slightly stiffer than the 90-96 20 mm bar. But they both mount the same on the rear.
All in all the suspensions of the 90-01 Q have roughly the same roll stiffness if the 20 mm rear bar is installed on the 90-96.
The front camber of the 97 and later is more towards ZERO than the upper linked 90-96 and radial tires need negative camber to function well. The 97 has an isolated front subframe which twists as it isolates the front from bumps and vibrations. These two things are the major reasons the lighter Q handles less well.The factory upgrade of adding a front strut tower brace standard on the 97 adds an improved feel to the turnin!
The 97 Q rear sway bar is slightly narrower [due to tread width] so it is slightly stiffer than the 90-96 20 mm bar. But they both mount the same on the rear.
All in all the suspensions of the 90-01 Q have roughly the same roll stiffness if the 20 mm rear bar is installed on the 90-96.
The front camber of the 97 and later is more towards ZERO than the upper linked 90-96 and radial tires need negative camber to function well. The 97 has an isolated front subframe which twists as it isolates the front from bumps and vibrations. These two things are the major reasons the lighter Q handles less well.The factory upgrade of adding a front strut tower brace standard on the 97 adds an improved feel to the turnin!
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szh
- Posts: 15932
- Joined: Tue Jul 23, 2002 12:54 pm
- Car: 2018 Tesla Model 3.
Unfortunately, no longer a Nissan or Infiniti, but continuing here at NICO! - Location: San Jose, CA
palmerwmd wrote:I wouldn't hesitate to put an "a" model rear stabilizer into my car if I didnt have one in it.
Fred...
Hmmm ... a dumb question from me (so what else is new?): I have been assuming that a stock 1995 Q does not have a rear sway bar as standard equipment. Am I wrong about this? I.e., this is one reason to get the bar kit from Infinitipartsusa.com!
I suppose I could out into the parking lot and look, but people usually respond pretty quickly to my stupid questions around here! :ylsuper
Z