Suspension question: Preload

Hey TW, not exactly crystal clear what preload is and what it does and affects. I have some questions below. Hopefully, you guys can answer them

Sorry if some of them are dumb questions.

1. Does preload affect ride quality (stiffness)?
2. Does preload affect ride height?
3. Does preload affect alignment?
4. Does preload affect suspension travel?
5. Does preload affect handling?

6. Also, would it be better, instead of setting preload, to just get stiffer coils?

Thanks, guys, your input is appreciated.

 

That’s easy. Yes to all

 

So, would I be better off with no preload and stiffer coils instead?

 

I'm not sure if I'd say 'stiffer' coils rather than maybe longer coils paired with the proper shocks. For example, you could add a coil rated for 800lbs (stiff) and you'd bounce all over the road. get the coils recommended for your set of shocks to give you the lift you're looking for where you don't need preload to achieve the lift. This is a good example for the 5100s -- https://www.headstrongoffroad.com/store/p449/HS_2"-2.5"_Lift_Coils_(Pair)_-_HS-TT05503-2LC.html -- the coils have the same spring rate (stiffness) but my guess is the 2.5 is longer. I'm sure someone will correct me if that's not accurate

 

https://accutuneoffroad.com/articles/coilover-spring-rates-for-toyota-tacoma-4runner/

good read here.

 

Pre-load means squeezing a spring to increase its spring rate before it is installed on the vehicle.

This is most often seen on aftermarket coilover setups for track race/autocross cars, there will be a threaded adjustment collar above and below the coil spring. This allows you to squeeze the spring and make it stiffer even before the coilover assembly is installed on the car.

Most of the coilovers for our trucks only have one adjustment collar. This is for setting the ride height only. The spring rate is unaffected by just moving the lower or upper spring perch up and down.

The term Preload is often used on TW to talk about ride height but its the wrong term.

 

1. Yes, but not the way you may think. Adding too much preload on a coilover shock will put the extended travel of the shock closer to being maxed out/fully extended. This will result in the coilover shock "topping out" very quickly and abruptly causing a harsh ride.
2. Yes, preload affects ride height. More preload = more height. This is the benefit from having an adjustable coilover.
3. More preload, more lift height will affect alignment. Usually recommended to get an alignment after adjusting lift height significantly.
4. NO, springs have no affect on the shock travel. Unless you are in coil bind or something wild like that.
5. For handling, shock valving, sway bar, spring rate all play a roll.
6. Depends on what you are trying to accomplish, shock travel and vehicle weight all play a roll on choosing the proper spring.

Adding preload DOES NOT change the spring rate. Springs compress due to the weight of the vehicle sitting on them. Springs are rated to compress X amount per inch. So for a 700lb spring, it takes 700lb of weight to compress that spring 1 inch. You cannot compress that spring more, at ride height, same vehicle weight by adding more preload. Adding preload will just lift the truck more. If you do start to compress that spring by adding preload, then that shock would have to be topped out.

TECH: Tacoma / 4Runner - Coilover Preload FAQ

TECH: Suspension Setup for OEM Fir Front Coilovers

 

Yes is an accurate answer, but 'stiffer' may (or may not) be the right phrase.

You'd be accurate to say 'select the correct coil for the purpose'. That may be a higher spring rate, a longer spring, or even both.

You haven't really said what you are trying to accomplish. But if it's lift like 98.34% of the posts around here, selecting the correct spring to accomplish that, with the correct damper to control it, will give you better results than preload or spacers.

OTOH, if it's just a lift for looks and you are on pavement 99% of the time, the less expensive methods will work too.

 

Accutune this is a super helpful post. The graphics and both links! Thanks.

Question - how could someone do too much pre-load? Why would a manufacturer have a setting that even makes it possible? Example: Bilstein 6112s (I know you don't sell them) have a 2" lift setting. Assuming the vehicle is not over-weight, is it possible to preload it too much considering there is a maximum to how much you can set for pre-load?

 

That would be a better question for the manufacturer. Threads on the shock body allow for a lot of adjustment and various spring rates. Threaded body allows for very minor changed also so lots of good things about having that much adjustability. In general, I suppose when there are adjustments like this, you could always have too much or too little. I assume that 2" lift setting is for stock weight? Which model Tacoma? 4cyl or 6cyl? short bed or long bed? As you can see, the variances go on and on which is why those adjustments are nice to have. This is also why we do not adjust preload prior to sending out the shocks, there are always minor changes that need to be made

 

It is interesting that "stored energy" does not get discussed or even mentioned. The door is open when raising the subject off "topping out".