how much pre-load is too much?

My front sway bar end links are a bit shorter than they should be to keep the bar's ends level. How much pre-load is too much?

I mentioned this in my other post about end links, so sorry if this is a double post.

I don't think there is any pre-load on the swaybar,... it floats freely with no end links attached. I believe the only issue is interference or hitting other components during it's full range of motion.
So if it doesn't clunk I don't think there is anything to be concerned about.

I don't think you are correct. The sway bar may float freely with no end links attached, but with them attached, there is load on it. I know there has been discussion in other threads about the effects of pre-load (sway bar angled upwards) on the rear sway.

I get what you mean but if both end links are the same length, there is really no pre-load (If the car is on level ground)
I remember reading that the guys were aiming towards having the sway bar level with the ground but it was a bigger issue to have them not hit anywhere and they were mostly talking about the rear sway bar.

The only relevance I can think of is having the pivot point of the sway bar as close to a right angle to the end link direction movement to help eliminate any "torque" effect. (I don't know if that makes sense so feel free to correct me).

pcb said:

I get what you mean but if both end links are the same length, there is really no pre-load (If the car is on level ground)
I remember reading that the guys were aiming towards having the sway bar level with the ground but it was a bigger issue to have them not hit anywhere and they were mostly talking about the rear sway bar.

Click to expand...

THIS.... you wont have any preload if its on level ground and BOTH endlinks are the same length.

OK, thanks for straightening me out, guys. So as long as the horseshoe part of the front sway bar isn't knocking against the chassis on bumps, I should be good. I am really loving my new suspension setup. I have Tein S-Tech springs, Stagg SHS struts, a Racing Beat rear sway bar with the clunk fix from the group buy, and AAC end links. It is still pretty comfortable for daily use, but now the car feels even more planted and predictable than it already did. I am falling in love with my P5 all over again.

just to clarify for future reference, adjustable end links don't really change the 'pre-load' of the sway bars...as mentioned, our suspension design doesn't support that because both front and rear bars pivot freely in the bushings (at least, to a certain degree)...

adjusting end link length DOES change the torque geometry the strut has on the bar, though...and this DOES have an effect on the overall suspension set up...Keeping the bar ends parallel to the ground (much like stock), gives the best geometry for the strut to load the bar...therefor gives the least amount of 'anti sway' during cornering...shortening the length of the end links will raise the bar end neutral positions...giving less of a mechanical torque advantage from the strut, overall giving the 'feel' of a thicker sway bar (more anit-sway)...lowering the neutral position past parallel to the ground (i.e. lengthening the end links considerably) has the same effect, but we're limited with room in that regard...the bar ends will come into contact with control arms, other supension parts, etc...

so, just pointing that out...shortening end link length from stock will give different handling characteristics...but its not because you're preloading the bar...you can't do that...but it does change suspension geometry enough to make a noticeable difference...especially in the rear...

the physics: the less angle between the strut end link tab and the sway bar end, the more difficult it is to push or pull the sway bar...and the higher the anti-sway properties...shortening the end links is the easiest way to reduce this angle of articulation...the 'softest' available option (i.e. the largest angle of articulation) will occur with sway bar ends positioned parallel to the ground (more specifically, perpendicular to the struts)...to get any softer than that would require a smaller diameter or softer metal sway bar entirely...so you can't reduce anti sway with adjustable links, as the stock end links keep the bars at that parallel position...but you can increase the anti sway properties considerably...

one last thing...be cautious if playing around with this stuff and using stock struts (as well as aftermarket replacements)...when you shorten the links, you're giving the sway bar more mechanical advantage...and that stress is going straight to those tiny little welded tabs on the struts...many members have snapped those right off, and this pre-load debate starts all over again...I wouldn't go very short on link length without some pretty meaty coil overs that have a large end link tab incorporated...especially if running a fatter sway bar already...

Thanks for the demisitification! I have been quite satisfied with the performance of my setup, so I think I will keep it as-is for the time being. The Staggs actually have remarkably beefy tabs for cheap-o struts, but I don't want to get overconfident.

^cool, and no problem...i just remember when AWR released their race spec 21.5mm rear bar and adjustable links...guys would shorten those out with that bar, and within a hundred miles or so...pull the tab right off the factory struts and/or blow the end links completely apart...I know my KYB replacement struts were not any different than stock in that regard...but my Tein SS coil overs have a huge reinforced tab for both front and rear...so if you're sure yours have good tabs to work with, go willy nilly with it...you can have a protege over steering in no time haha...

one last note i forgot to include:

Since our bars are connected on either end, biasing torque advantage to the bar will have a negative effect on non cornering related stuff...like uneven pavement, pot-holes etc...since the bar will hold the strut in place with more mechanical advantage, it will transfer more torsion to the other side...and will yank the other side all over the place because of it...its a tight line to get it decent between an improvement over stock...and simply too crazy for a street car...again, assuming your using an upgraded bar...stock bar, it won't make that big of a difference, but will still be noticeable...more advantage towards the bar will also reign terror on the bushings, so keep in mind you can develop annoying clunks a lot faster than leaving them at stock length...

Yeah, I have certainly noticed that non-cornering aspects have been affected, but not to the point of the car feeling excessively squirrelly. For instance, I three-wheel as I pull out of my steep driveway (I have to leave at a slant to keep from scraping).
I have a Racing Beat rear sway bar with a clunk-fix kit and urethane bushings, so hopefully those bushings won't go anytime soon. Up front, though, I have a stock sway bar with stock bushings, so I'm sure they will be strained a bit more than they are made to be. I have a Racing Beat front bar on hand, but have not gotten around to installing it. The AAC end links have spherical ends, so they clank a bit, but Noah is making available rubber caps to cover them, which should help a lot.

But yeah, it seems like the tabs on the strut are much beefier than stock so I hope they can take it. The rear sway bar is not biased much at all. It is nearly, if not completely, level to the ground. I have been having so much fun with this new setup. Sometimes I feel ridiculous for spending the time and money on a car with so many miles, but when I take a freeway on-ramp at 55 mph without any lost grip, or when I lift-throttle oversteer and keep it under control, it all seems worth it. That feeling is without parallel. I am falling in love with my P5 all over again, and I couldn't have done it without this online community.