This is going to be a long read, so if you are not really interested in understanding the basic physics behind vehicle suspension components then click "back" now. If you are lifting it for "looks" (bubba) then click "back" now. If you are interested in gaining enough knowledge to make your own decision regarding suspension component selection (and knowing more than 97% of the rest of the world regarding suspension) then read on!
Oh, for those guys who worry about "nose dive" and "body roll," you really need to read this.

With the introduction of the TRD Pro series 4Runners, there have been quite a few comments and questions on the difference between the new suspension components and the traditional components. In addition, there are always questions from the new guys on shocks, springs and general suspension.
The purpose of this post is to provide a technical explanation of shocks, springs and general suspension components. I am not going to re invent the wheel here but am going to provide a few links that I feel adequately explain the concepts and componentry required to take our 4Runners on and off road.

First, let me start with a few basic definitions:
Springs:
Springs are primarily responsible for keeping the tire in contact with the road surface over bumps and dips.
In the realm of physics, springs are noted as being efficient machines for storing mechanical energy. When a spring is compressed, the energy required to perform the compression is stored. When the compression force is removed, the spring returns to its original shape. No additional energy input is required. A spring can also be stretched (to a point), and it will return to its original shape.

Shocks
The primary function of the shock is to dampen the oscillation of the springs after the wheel travels over bumps and dips.

Now that you are in the right frame of mind, read this:
Off Road Xtreme College 101: An Insiders Look At Shock Absorbers
This is a short description on shocks. The major brands many of you are looking at or using are described here. This also gives you a basic understanding of shock theory.

Now that you have read the basics, it's time to dive into the theory! "But wait 1engineer, do I need to understand suspension theory?" Not really, but this article is the basic, simplest explanation on our type of suspension out there. It is much better (...and clearer...and simpler...)than me writing it myself! So, if you are ready to learn
Coilover Bible
This is an exceptionally well written article that explains the whole gamut of suspension, from component description to basic suspension geometry and simplified mathematics needed to determine component selection.

I hope this helps the thousands of you that will read both links completely! Ha, just kidding. The "few of you" is more likely, but I have been wanting to post these links for some time and the introduction of the TRD Pro with the different shocks makes this as good as time as any. After reading, post to discuss. Enjoy!

Wow. That was some of the most interesting reading I've done in a long time. Now that I am not totally clueless about the workings of the shocks and springs, a second and third read are in order. It's always good to learn some thing new.Thanks for the info. Now i just have to find a way the sneak the wife's scale out of the bedroom with out being caught.

Okay, so which shocks and springs do I need to fit 285s w/o rubbing?




























Someone had to do it.

Holy CR#P, man! That is a dangerous question! I could just see everyone mid way through typing "search" already, before they saw it was a joke!

No, @eddiebx , AKA Richard Cranium, is just having fun at my expense. He knows I write these posts to answer these type questions or provide reference for future questions.

Don't worry, I doubt very many people take me seriously here, lol.

I was joking as well, but I bet you did catch a few momentarily. ;)
Good article.

To kind of bring this thread back on topic, and I'm sure someone out there other than me is wondering this (I hope); Greg, can you comment on the benefits of these upgraded TRD shocks? ie. larger pistons, shafts, etc.

Chart hijacked from @dekeman in the other thread:



I was looking at press release photos of the front shock and boy do they look beefy compared to my 5100s!

The larger a shock is in diameter, the larger its bore can be. The bore is the diameter of the piston and the inside diameter of the pressure tube. The larger the piston’s diameter, the larger its surface area. Since pressure is force divided by area, it stands to reason that the larger the area, the smaller the pressure generated by a given force. Inside a shock, the lower the pressure, the lower the temperature. In addition, a larger diameter shock can contain more oil to absorb and dissipate the heat generated, resulting in reduced internal operating temperatures for a given force. The result is, the larger the shock diameter, the cooler it will run and therefore the harder the shock can be worked before fading. The larger the rod the stronger it will be, given same material spec.

Thanks for posting how a shock and spring work, but being an Engineer I cant see how you left out a very important part in the two different types.


Digressive valving : In a digressive piston design, the shocks dampening capabilities are felt more rapidly because the piston is concaved and the shims are slightly bent (preloaded) into the dish shape of the piston. The benefit to this over using just heavier grade shims is that the dampening response is felt much quicker but the max yield doesn't really change.

As shaft speed increases, the valving gets softer. A digressive designed shock has a considerable amount of low-speed control and builds resistance as the shaft speed increases to a predetermined point where the rate digresses and stays the same as the speed increases. This type of design has good low-speed control and does not build ultra-high resistance with the high speeds associated with bumps and holes.

Digressive shocks :

CRAPCON aka ICON
Bilstein 4600/ 5100 /5125 / 5150 / 5160 / 5165
Rancho
Monroe
Skyjacker
Rough Country

You get the idea...



Progressive valve stack / Linear As the (shock) shaft speed increases, the valving gets stiffer. A linear shock has a piston that is designed to start out with low resistance and continue to build as the speed of the shaft movement increases in a linear fashion. This type of shock has very little low-speed control, but very much high-speed control.

Self adjusting deflective valving is pretty much standard issue in any decently made after market shock (sway-away, fox, etc.) It's essentially like the digressive shock described above (uses a piston with multiple shims stacked in a pyramid on both sides for dampening) only the piston is NOT digressive (concaved). This is known as progressive/linear valving.

Progressive Shocks :

KING
FOX
RADFLO
Camburg
Sway-Away
Walker evans
Bilstein 6100 / 7100 / 9100 / 9300
All the big boy shocks...


Digressive valving works great for sports cars, minivans, street trucks, ect, where you're looking for on road feel and a smooth ride. Digressive valving will have a firmer feel to it and this is what most people relate to them feeling a harsher ride than over a Linear shock. This type of shock is CHEAPER to build, easier to R&D, less maintenance required, more of a 1 size fits all attitude.


Then look at any trophy truck, class 1 car or any shocks built by the big boys that have thousands of hours in testing and racing and you will see why they run a linear/progressive valving/piston setup.

This is primarily why I HATE ICON so much, it is nothing more glorified than any of the other cheap digressive shocks, just at an over inflated price to make it look like it is in the same category as the well known big boys. Go to any desert race and try to find even one team with this brand, you wont and there's a reason why.

(P.S. Doesn't that TRD PRO model sound SWEEEET, yeah LOL. It will be the same models of bilsteins as the Tacoma Baja TX 5100,s out front and 5165's out back, ow yea plus the cool TRD stickers on them LOL.

There are several reasons I did not explain or post links for shock valving design. The main one being is this is meant to be a simple guide to the general operation of suspension components and not a detailed one.
Also application and economics dictate shock type, not valving design. It would be pretty silly to install 9100's on a vehicle that I drove on the interstate every day except for a few times I go slow on trails and over rocks each month. Conversely it would be silly to think I can hit a ramp and jump 80 feet with my stock TE. Well, I could, but the results wouldn't be pretty.

If there is enough interest I would be happy to include the valving design later. I will even do it in a non biased way.

Well in that case, thank you for re-posting an article that you read on the internet. That "Off Road Xtreme College" seems like a real winner. The Pirate is a good start for beginners to read, but considering it is 6+ years old and 10,000,000+ views I don't think it's nothing that hasn't been posted before. Just more people posting "what they read" and now act like they know it all. Ever since the internet has sprung up many years ago, their is more and more internet faber's and Engineers it seems these days.

I guess I was mislead by the title of this thread then, and that it was only meant to be a simple explanation of how coils and shocks work. But one would think an engineer could simplify it to a much greater detail. I mean those links are a head spinner for most right?


I totally agree, different strokes for different folks and that 9100's on a street queen would be overkill. You have to justify what you are buying to what you intend to do/use-it-for. Just like that TRD Pro suspension you are raving about, (which is overpriced for what it actually is) go and actually put that suspension threw it's paces and "break something". See how much Toyota is willing to honor you're all high and might warranty now even though how it was marketed.

Also if you're valving explanation later includes more "links to stuff you read", just please spare me the details....

Somebody didn't hit the back button when they were told to

I love technical discussions of suspension design.

It will be significantly more beefy than a set of 5100s. The front piston of those Pros being 60mm, should be the equivalent of a 2.5" diameter shock, and the rears with their 46mm piston are about the same as a 2.0" diameter shock.

The 5100s also use a 46mm piston and are a 2.0" diameter shock also, but obviously has more of a street setup. And honestly, from a shock design perspective, there's really very little you can do in terms of high quality for a set of 4 shocks that sell for $300. If anything, there's a really slim margin on those. Higher quality designs require more money.

I'm a little surprised they didn't go with a 2.5" diameter shock for the rear, but the added external reservoir is nice surprise.

Looking through all the aftermarket shocks that Bilstein offers, I don't see anything that matches these, especially that 18mm front shock shaft, usually most of these OEM applications are just a slightly modified current design. Bilstein seems to use 14mm and 22mm shafts generally.

It's always hard to tell what the damping goals for the Pro were, although since this is from Toyota, I wouldn't be surprised if this was tuned more for the street.

I don't expect these to be as good as all of the good coilovers from Fox/King/Radflo, but they should be significantly better than a set of 5100s. Without any additional specs from them we'll just have to wait for reviews.

I do like that they added a 1.5" lift for the front, honestly stock was way too low and you could easily bottom it out over speedbumps, but I still feel a higher amount of lift is needed to put the suspension travel in the correct zone for offroad use. Although for Toyota that would require a new set of UCAs to get the alignment within spec again, and rollover safety issues also would come up.

I'm also impressed with the 1/4" plate aluminum skid plate. That's the same thickness that budbuilt offers and should be strong enough to take a good amount of hit.

I went ahead and read all this and am looking forward to seeing where this goes, especially in terms of brand technical differences and what that actually means to the end user.

For example I use my 4R to get to hunting/camping locations and trail heads so I don't "need" a lift or a new suspension until I start dragging stuff off the vehicle. Once I have the need it'll be nice to be able to make an informed decision.

At least that's my theory. So by all means keep this going.