Using that diagram: If you take the 1st pic -no load- and that area is 20 inches long right. And 20 inches is a far as it will stretch. Now you put a 2 inch spacer inside that 20 inches. Now the coil has to be compressed more because now it only has 18 inches left inside that 20 inch space. Its still 20 inches because thats as far as the shock will stretch.
With that said, If you use the All-pro spacer on top as I mentioned earlier, then the coil still has its 20 inches and the spacer is on the outside, not inside, thus making the coil-over now 22 inches like in the 3rd pic.

 

I guess it all depends on what your definition of what "pre-load" is...

I understand what you are saying. Yes, off the truck the spring is more compressed with the spacer in. Is this "pre-load"? IMO, I think it is not, there is no "load". Once the downward weight of the truck is what is compressing the spring and not the restriction of the strut, then you have "pre-load". Any additonal weight is then "load".

Compare the length of a coil on the truck vs. on the truck with a spacer. It will be the same, I am almost positive.

 

When we say preload, it has nada to do with the weight of the vehicle. ...Never mind ....I give up.

Next.

 

Ah ha! hehe, both of you guys are saying the same thing and you are both correct that the spring is preloaded when the shock is not installed in the truck. You are also correct when you say the preload is increased when a spacer is installed.

However, once a spacer'd assembly is installed in the truck, the preload on the spring is the same as without a spacer. This is because the suspension is "floating". A 2 inch spacer extends the shock 2 inches. Think of it this way...if the spacer "preloaded" the spring and compressed it 2", then there would be no lift.

This is explained in figure 1, scenerio 2 and 3.

Edit: also as stated in my article:

 

Here's some more reading for this thesis defense: http://www.4x4wire.com/forums/showfl...=&fpart=1&vc=1

 

One last comment and I'll shut up. First, have you ever taken a coil-over out of a 4runner,tacoma, etc and actually taken it apart?
I don't claim to be an expert but I've worked for South East Toyota for nearly 6 years.
Putting a spacer inside the coil-over doesn't lengthen the over-all length. The length is only determined by the distance from the lower spring seat to the upper and the upper seat which is at the top shock bolt.
When a coil is compressed more than stock because of the spacer taking from its room, it becomes stiffer(preloaded) and that makes the coil-over now firmer which creates lift because now the vehicle sags less than stock because of the firmer suspension.
Just like turning torsion bars or loading torsion bars on 2nd gen. It makes the suspension stiffer creating lift.

Thats all I have to say about thaaat.

 

Shawn, me thinks you did not read the article or you just skimmed over it because what you are saying about cranking the torsion bars making the ride stiffer because of preload is incorrect too which is covered in the article.

I have installed coils in the front and rear of the 3rd gen 4runner 3 times, I am a mechanical engineer, and I was the front suspension team leader for the Cal Poly Solar car club back in college where my team designed and built the front suspension of this $250k vehicle. I've also had 2 fellow mechanical engineers who have a 1st gen 4runner and a taco to review the article and they both agree.

I genuinely would like for everybody to understand how suspension works and don't mind these long explanations. I understand your thought process and I would like to further explain why it is incorrect. I'll PM ya and we can discuss this further (unless you would rather not).

 

steve i havent read you article yet and will after this post. so when you say that torsion bars are not pre loaded then what you are saying is that the bars are indexed to a nuetral position and the torsional affect is whats keeping the vehicle from colapsing to the ground. from my experience the bars are indexed to a "preload" position in order to support the car, all cars i have played with are like this vw,porsche, nissan, toyota,gm. there are other industries that will use the preload termanololgy. and is basically the same from sector to sector. now its great that youve done things in a controled environment but out of the box is a little different. had a girlfriend that has a mechanical degree from m.i.t and she is still domb as a box of rocks (in a practicle sense) now i'm not calling you dumb just letting you know she was

off to read your article and donning nomex right about now

 

No no, I'm not saying there is no preload, all springs in suspensions are preloaded. I'm saying there is no change in preload when they are cranked. No nomex needed, I never flame.

Edit: oh, and calpoly's motto is "learn by doing." Most students who graduate from cal poly ME know how to weld, do a carbon fiber layup and machine...basically, we know how to build things, not just book smarts. Our club actually built just about everything on that car, from the wheels to the frame to the carbon fiber shell.

 

thanks for the no flame, i think its a trick in order for me to remove my flame retardant material so i would be burned later in the thread .

just read your article and i have to say OH;

 

Okay, didn't read the article but I will put my understanding in here.

Preload yes, change in ride no, lift yes.

Look at it this way. Take a stock coilover and look at it at rest. It will be close to extended, let's just take a number and say 25". When you put the weight of the truck on it, let's say it drops down to 21". This is because the weight of the truck is compressing the spring. Let's say we have a weight of 2,000 lbs(again just pulled out of the air for easy use), on the springs. They are being compressed by that much weight.

Now add the spacer. At rest the spring will be compressed more than usual and let's just say the pack is 3". The spring will now be compressed to 22", but still the total length of 25". At rest off the vehicle there will be a significant preload. The preload will be close to the regular weight of the front half of the vehicle because the spring is compressed by one inch less in length. Now put the coilover back on the vehicle. The weight of the vehicle will take over the "preload". The only load now is the weight of the vehicle again, however there is an additional 3" spacer which when loaded acts like an extra 3" of spring. This will effectively raise the vehicle by 3" also, regardless of whether it is inside or outside the coilover. This will not however increase droop. The droop will still be limited by the max extension of the coilover, so your tires will droop 3" LESS, because they are already dropped by that distance.

So, to get a lift and keep the same uptravel and downtravel you want to put the spacer above the coilover unit. This will give you the lift by changing your mounting points and leave the travel the same.

Does that make sense for those of you that don't understand??

 

Steve, I just read your site...(quick glance over more like it...)

"Having said all this, there IS a way to increase the preload without adding weight. A coil spacer long enough or the torsion bars cranked enough to completely extend the suspension all the way to the bumpstops will start to increase the preload on the spring. Of course, this means the one would be riding around on the bumpstops all the time and that would make for a very rough ride."

I had to laugh.... this is how I got my truck. The bumpstops were squished and the ride was VERY rough. I very quickly added some blocks to the rear and lowered the front by 2" to fix the ride. Much much better!

 

ok, 2 stupid questions. with the coil overs being shocks with coils, and my 94 IFS pickup just having shocks front and rear, i can put the coil overs on my truck, front and rear, correct or no? and if i do that, and add spacers, that will lift the truck? and if i can only put them in the rear, with a spacer adding lift, and i already have a suspension lift, how do i compesate for the rear lift for the front? sorry to question this, im just kinda confused i guess.

 

No, you cannot use coilovers in your truck. You want to lift it more than 4in?

 

i would like to get another 2 inches or so, but don't want to do a body lift. i was thinking that way or bushwacker cutouts. i guess the cutouts will be the way to go. how come the coil overs wouldn't work?

 

one reason i'm going with the daystar spacers on the rear of my 90 (light duty downey 1.5" coils), vs a taller coil, like a 4" taller than stock coil, is to prevent that increased swaying feeling.

and yes, it is cheaper...

 

Hopefully, this will illustrate what I (and Robinhood150) was trying to say about the 3rd Gen. front. I'm trying to clarify what the unit does when installed on the truck, and not what it does laying on a table. The spacer doesn't extend down travel and it doesn't effect the spring once the weight of the vehicle is applied.

 

They make custom make coilovers to any size you need. Yes to your question, but only for the rear. All it takes is some fabrication.

There is a BIG difference in the suspension of your solar car and a 4Runner. That's like comparing a sk8board to a golf cart.....

The coil pack is preloaded before instalation, and it has the same preload after it is installed.

"The spacer doesn't extend down travel and it doesn't effect the spring once the weight of the vehicle is applied"
Down travel is determined by the shock length in these coilovers.
Any thing you do to a suspension will eventually effect it when it is installed.
I know the # are way off but say the spacer needs 50lbs of pressure to fit into the pack. You put 200lbs of weight on the spring when installed. The coil is now being pushed down to a rate of 250lbs instead of 200lbs with out the spacer.
This increases the stiffness (preload) of the coilover and doesn't allow the suspension to droop with excess weight.
That is where the lift comes from.....

 

uhm... okay

okay

How do you come up with that conclusion?

That initial "50lbs" of pressure is only due to the restricted length of strut. Once the weight of the vehicle is applied, there is no restriction. The "200lbs" is still "200lbs". Why is this not clear?

 

Okay, I don't want to dog on you.... but you are contradicting the laws of physics. If you are in school, take this to a physics teacher for an explanation. The pack will only add it's own weight to the compression once the vehicle is added. This is rudimentary physics.