Sway bar pre-load
 

Can someone help me understand how pre-load on a sway bar affects handling? For example, I am lowered and have aftermarket sway bars but stock end links so I understand that since the upper mounting points of the endlinks are lower to the ground they put more downward pressure on the swaybar since the length of the endlink remains the same. I also understand that aftermarket endlinks exist and would correct this problem, but I’m trying to get a sense of how a pre-loaded bar front and/or rear changes the handling. Thanks for any input!

Preload is the force (tension/compression) on the sway bar when the car is at rest, before the load when cornering. Having the car lowered changes (increases) the amount of force on the sway bar, and in turn the end-links, because the different geometry of the suspension. I wouldn't worry about handling changes so much unless your racing competitively, they won't be big enough to notice unless your a professional driver. The stock end-links "should be" strong enough to handle street driving. I would consider upgrading when you have the chance though.

Stock height or lowered with the stock end links doesn't preload the sway bar that much. You use the adjustable end links to fine tune the handling, which 99% of drivers won't notice the difference. Also if you are lowered. The adjustables help eliminate preload if the car is not quite level from side to side. Besides the SPL's are stronger than the stock ones.

These really come in to play when using coilovers and you are corner balancing the car. It will affect the corner balance and you need adjustments on the swaybar endlinks when doing this. I watched it happened when my car was corner balanced. Crazy how sensitive it can be.

I'd never considered that... super helpful!

Some guys were talking about that at an autocross. Discussing taking the preload off with driver's weight....or rather, preloading that corner to offset driver(assuming adjustable endlinks).

The correct way to corner balance is with the drivers weight in the drivers seat. That is how my car was done. 180lbs in the drivers seat. The sway bars are connected while checking the weights, If the weight changes the lengths are not correct. It is time consuming and tedious to get them good to go.

When I corner-weight I disconnect the bars.

Corner weighting is done on a car lift and we use scale setup tables so we are sure that the tops of the scales are all in the same horizontal plane (I have clear plastic tube we fill with water to make sure of the levels and measure to within one mm).

Get the cross-weights, side/side and front/rear right and then re-connect the bars with car on its wheels - I use adjustable links with rod ends to make sure there is no "stiction"

Corner-weight session can take a minimum 2 hours and full alignment and corner weights can take ~ 4 hours.

At ride-height on levle ground there ought not to be any pre-load on the bars "if" you want to turn left and right equally.

Well, I guess I left off the part that during the corner balance the bars are disconnected. When connecting them back up is when you will check your weights to ensure your endlinks are set properly.