Quick questions Re: sway endlinks.

[slipnfall]

Hi Folks, I'll admit first off that suspension geometries is a mirky area to me and though I am trying to learn, I could just use some sound advice on this topic. The last time I pulled my front sway bar I noticed that the end-links doughnuts and D-bushings were really bad. The D's were cracked and squeezing out from the bracket, and the doughnuts were permanently deformed(think wedge-shaped). The rear seemed to be just as bad if not worse.

From what I understand, simply stiffening the bushings introduces an 'artificial' sway bar size increase. Would I see any benefit from just replacing the bushings? I know a buddy who installed a stiffer front sway bar on his hatch, and said he noticed absolutely no difference untill he installed new end-links. So I'm thinking instead of dishing out the money right now for new sway bars, why not work with what I have so far? BTW this is a '92 240sx with the non-hicas bars.

I was thinking about the white-line poly. units: do I want to just grease the mating surface with a lithium-based grease?

Thanks,Jamie

[slipnfall]

I guess I should add that this car is used [primarily] as a daily driver, but weekend road-coarse racer. Current suspension is AGX/s-techs, NISMO T/C bushings, SPL subframe spacers, NISMO rubber components on rear shock assembly.

[Q45tech]

When a sway bar attaches inward from hub, say in middle like rear does, the motion range is quartered.

If the wheel moves 1 inch the bar twists 1/4". A bar with 160 lb/in stiffness actually provides 40 lbs of stiffness because it only moves 1/4".

Bushing stiffness is critical until the bushing is FULLY compressed.

Rubber is used so that the 8 bushings [4 per side] together provide slack [an amount of wheel movement when the bar does little or nothing] to deal with street bumps.

For a 1" wheel bump you need 1/4" of total bushing slack in each direction.So the springs alone control body roll until the bushings start to compress, the bushings are less stiff than the bar, therefore the rate while rising starts off tiny.

Even stiff urethane has some give initially.

[corn322]

The new bushings will make the sway bar react quicker, because the stiffer bushings don't absorb as much of the motion.

[cdlong]

Q45 tech is great at giving technical info, but now to actually answer the question with real world experience. my car is set up similar to yours (though it's an S14) and i installed all poly bushings on the sway bars. i couldn't tell the slightest difference. save your money and time and get aftermarket sway bars when you can afford them.

[slipnfall]

Thanks for the response cdlong - The whiteline bushings aren't expensive at all(roughly $40-50 for the whole set), so that's not really an issue. Besides I'd need them anyways if I did get an upgraded bar. I'm a little dissapointed you didn't feel any difference, but maybe yours were in OK shape before?

Q45: from what I read, the rule of thumb is to never let the sway bar rate exceed the spring rate... is there any way of guestimating the 'spring' rate of a bar based on the diameter? The S-techs spring are rated at:

3.7kg/mm => 207 lb/in Front3.2kg/mm => 179 lb/in Rear

with: 24mm front bar, 16mm rear

So how close of an optimum match would I get with poly. bushings, stock bars, mated to the Tein S-tech spring rates? Is there an upper limit in bar size that I should never exceed with those spring rates?

One last thing while I have you here: for the purpose of a shock/strut's longevity, should the damper setting be higher or lower than the optimum 'matched' spring rate?

Thanks everyone!'slip

[McRussellPants]

Q45 tech is great at giving technical info, but now to actually answer the question with real world experience. my car is set up similar to yours (though it's an S14) and i installed all poly bushings on the sway bars. i couldn't tell the slightest difference. save your money and time and get aftermarket sway bars when you can afford them.

Thats because you have shocks and springs... You won't feel it as much since you've got an *** ton of body roll...

If you have a stiff suspension you'll feel them more since the bushings flex for a larger percentage of the travel.

http://www.ziptied.com/forum/viewtopic.php?t=6990

There ya go. if you want good endlinks make those. 50$ per axle is funky fresh.

I'll prolly get the Largus ones from SPL since I'm a ricer.

[cdlong]

don't new sway bars usually come with all new bushings?

[ddgsxr504]

Yes but they don't all come with Poly bushings.

[Zion8561]

The Whiteline bars look really good, and I am going to pick them up after I take care of some other things on my car first. I like that they are adjustable rate and I can 'fine tune' over/understeer with them, although spring rates make the most difference.

Anyway, you can get the set for $400. Spending $50 on just the bushings seems like a waste if you are planning on getting the bars later IMO. I am sure you have other things that the $350 could be spent on though

[Q45tech]

From some measurements on a Q45 rear bar:

15.9mm bar = 50 lb/in for bar but coupled thru solid urethane mounts and into hub= 12 lb/in after 1" of hub motion

20mm bar = 160 lb/in or 40 lb/in at wheel/hub remember the rule of thumb ratio must use hub/wheel numbers not the as published spring numbers.

You must correct spring numbers for rubber mounts, mount angle, and mount location distance from hub.

RWD Nissan use similar rear suspension only track width and arm length and spring offset and angle differ between models.

A Q45 rear spring mounted around an oem shock loses 20% of its published spec stiffness to the hub offset and angle. So 123lb/in x 0.8=~98-102 lb/in of roll stiffness applied to the tire. The tire stiffness [depends on inflation and model] and is in series with the spring....say 93-95 lb/in of total rear stiffness from body to the road.

A 20 mm rear bar adds ~~40 lb/in to hub again the tire loss say 37, so the bar and spring create 37 +94= 131 lb/in of which the 20mm bar represents 28-30%of the total rear roll stiffness..............40/142=28%

A 22 mm rear bar is roughly 46% stiffer than a 20mm..say 60 lb/in [rounded up]. With the same springs new stiffness would be 94+60 = 154 lb/in at hub/tire ...........60/154=~39-40% from the bar..........60/160=37%

Again you cannot go by published spring rates as how they mount and attach to suspension arm/hub softens them significantly.

Why stiffer than stock % means little until you know what stock is and how much is loses in mounting process.

A 24 mm bar would be 208% of a 20mm bar ~~84 lb/in is getting pretty close to spring.

The above is for oem hollow bars which might be only 90% of solid bars.

The above is probably +-10% accurate depend on bar length with convolutions and right angle arm ratio.

[S14KoukiMonster]

I installed the energy suspension poly bushings and end links on my car w/the stock sway bar. I'd previously lowered the car myself, and I DID notice a difference between bushings after the install. I didn't even have to fully drop the sway bar. The kit was only $38 can., which is like $30 us. Definately worth it for the $$$ in my opinion. Just make sure to lube the D shaped bushings really well because poly bushings tend to squeak.