A suspension question for engineers

[1engineer]

I have nothing to add except this: "You had better be working on a vehicle you either never want to drive or you can convert back to original suspension geometry when you experiment with steering geometry for the first time."

Now with respect to engineers always saying they are engineers: Do you know why they are like this? Because that is the one sentence that gives credibility to an idea. Now, the next sentence could be BS but that is immaterial. Here is an example:

"That suspension design is terrible. I should know, I'm an accountant." or
"The thermal efficiency of your engine is only about 28% max. I'm a Paramedic and I work with them daily."

With that said, after designing stuff since 1989 I am ready to say "Hello, I cut lawns (sell cars, clean gutters, whatever) for a living." After 26 years I am getting pretty tired of it.

 

[1985taylor1925]

If you are actually interested in suspension design, look at the Caroll Smith series of books. He gives a really good explanation of a lot of important suspension design topics and explains what changing different parameters does to different ride qualities. I believe the book you want is either perform to win or engineer to win.

I did a little suspension deign in college and you are talking about a world where fractions of a degree or fractions of an inch change characteristics drastically. Attempting to reverse engineer suspension without a means of accurately measuring the vehicle is extremely difficult if not impossible.

Glad you found your bushings are shot, I'm sure it will ride better when they're replaced!

Thanks for that reference. I have always been fascinated by suspension designs. I think I will order that book

 

[ReconCmdr]

I have replaced every single component of my front end and still suffer from the same jumping/bouncing/horizontal effect when I hit any kind of bump while driving. Tires rotated and balanced and alignment within the last month and still there. I just assumed its a minor flaw in the design that I will have to live with...as I have lived with it since I bought it new off the lot at the end of 1997. But boy it would be nice for additional stability on the front end.

 

[1985taylor1925]

3rd gen suspension in real time

I took a video of the drivers side of the suspension to watch it in real time. I thought it would be cool to see things in motion. I also did one of the rear suspension, but haven't yet loaded it. My idea is to move the camera around and film different parts of the suspension. I bet if I take a video of the lca bushings it will be easy to see them moving excessively

 

[Unner]

After this thread I have paid more attention the the "front end" handling of my 4R. I can honestly say it drives just as good as my 2nd gen Tundra. As mentioned, the shorter wheel base and narrower body will tend to exaggerate any bump in comparison to the semi-long truck.

I barely need to hold onto the steering wheel of the 4R and find myself just keeping pressure on it with a finger or 2, despite any differing road conditions. The tundra likes to track around more, but I am attributing it to the wider tires and the larger wind area.

In comparison, I was able to let go of the steering wheel for a good couple blocks on the expressway and it tracked great with no input. My truck would had driven into the guardrail over the same distance.

My two side by side.

These pictures really show how massive the new tundras are compared to our 3rd Gens. Makes the 4Runner look like a toy...

Now with respect to engineers always saying they are engineers: Do you know why they are like this? Because that is the one sentence that gives credibility to an idea. Now, the next sentence could be BS but that is immaterial. Here is an example:

"That suspension design is terrible. I should know, I'm an accountant." or
"The thermal efficiency of your engine is only about 28% max. I'm a Paramedic and I work with them daily."

With that said, after designing stuff since 1989 I am ready to say "Hello, I cut lawns (sell cars, clean gutters, whatever) for a living." After 26 years I am getting pretty tired of it.

This was golden.

 

[A.Wilson013]

Now with respect to engineers always saying they are engineers: Do you know why they are like this? Because that is the one sentence that gives credibility to an idea. Now, the next sentence could be BS but that is immaterial. Here is an example:

"That suspension design is terrible. I should know, I'm an accountant." or
"The thermal efficiency of your engine is only about 28% max. I'm a Paramedic and I work with them daily."

With that said, after designing stuff since 1989 I am ready to say "Hello, I cut lawns (sell cars, clean gutters, whatever) for a living." After 26 years I am getting pretty tired of it.

Cool story, Greg, but I think that on a forum it serves no purpose other than to inflate the ego.

Unless you're on the 5th gen forum, of course. Then it makes you a god. Or a moderator, I see.

 

[D Farms]

Cool story, Greg, but I think that on a forum it serves no purpose other than to inflate the ego.

Unless you're on the 5th gen forum, of course. Then it makes you a god. Or a moderator, I see.

I should have mentioned that when i made my corola led retrofit in the 5th gen section.

 

[1985taylor1925]

I have nothing to add except this: "You had better be working on a vehicle you either never want to drive or you can convert back to original suspension geometry when you experiment with steering geometry for the first time."

Now with respect to engineers always saying they are engineers: Do you know why they are like this? Because that is the one sentence that gives credibility to an idea. Now, the next sentence could be BS but that is immaterial. Here is an example:

"That suspension design is terrible. I should know, I'm an accountant." or
"The thermal efficiency of your engine is only about 28% max. I'm a Paramedic and I work with them daily."

With that said, after designing stuff since 1989 I am ready to say "Hello, I cut lawns (sell cars, clean gutters, whatever) for a living." After 26 years I am getting pretty tired of it.

This, or course, in way describes me. The entire purpose of this thread was literally to ask engineers my question, not to tell them what I know. I have never claimed to know more than anyone, including the Toyota engineers or the engineers on this forum, or anyone else for that matter. The reason I stated Im a scientist was to express the fact that I DONT know everything about this topic.

But, I do know this. Every single person on this forum (including myself) who has added a suspension lift, has altered the original geometry and engineering of our trucks, including ackerman.

I also know that the rear mount steering rack is a more unstable design. Hence the reason Toyota changed it to front mount on the 4th gen.

 

[A.Wilson013]

T .

What the... T4R tells me my signature pic is too big, then you pop in here with that?!

 

[1985taylor1925]

What the... T4R tells me my signature pic is too big, then you pop in here with that?!

Haha. That was an accident. I don't know why it was that big. I cropped it

 

[RoyBell]

This, or course, in way describes me. The entire purpose of this thread was literally to ask engineers my question, not to tell them what I know. I have never claimed to know more than anyone, including the Toyota engineers or the engineers on this forum, or anyone else for that matter. The reason I stated Im a scientist was to express the fact that I DONT know everything about this topic.

But, I do know this. Every single person on this forum (including myself) who has added a suspension lift, has altered the original geometry and engineering of our trucks, including ackerman.

I also know that the rear mount steering rack is a more unstable design. Hence the reason Toyota changed it to front mount on the 4th gen.

Is your only source of it being bad because it's been discontinued?

They also discontinued the V6 in the Rav4
They also discontinued the V8 in the 4Runner.

Both I would say were excellent designs, and unfortunate they had to die (EPA?)

 

[1985taylor1925]

Is your only source of it being bad because it's been discontinued?

They also discontinued the V6 in the Rav4
They also discontinued the V8 in the 4Runner.

Both I would say were excellent designs, and unfortunate they had to die (EPA?)

Read through the thread

 

[RoyBell]

Read through the thread

I did read it. All I could conclude was your bushings are worn and you are blaming the steering rack :rofl:

Is it Friday yet?

 

[1985taylor1925]

I did read it. All I could conclude was your bushings are worn and you are blaming the steering rack :rofl:

Is it Friday yet?

I do think my bushings need to be replaced, which Ill probable get to within the next few weeks.

As far as the steering rack, its not the rack that's an issue, but the location.

"rearward steering arms are not as good as front steering arms on well designed systems".

That's directly from 4ripcord, a suspension engineer who works for Honda. And that is the reason Toyota switched to a front mount design. Im not saying the rear mount is an incorrect design, or even a bad design, its just not as steady as a front mount.

 

[1985taylor1925]

Also, which way is it wanting to wander after bumps? The trac bar in the rear pushes the rear of the body to the right making the truck feel like it is turning left.

I have another suspension question, and figured you would be a good person to ask. Though, any info from anyone who know this topic is appreciated.

I understand the difference between linear rate, progressive, and dual rated coils.

A 500lb linear coil for example, requires 500lbs of force to compress the coil 1", correct?

So beyond that first inch, does that mean than it will take an additional 500lbs of force to compress the coil another inch? I.e., 1000lbs to compress 2", 1500lbs to compress 3", etc.?

 

[4-Ripcord]

I have another suspension question, and figured you would be a good person to ask. Though, any info from anyone who know this topic is appreciated.

I understand the difference between linear rate, progressive, and dual rated coils.

A 500lb linear coil for example, requires 500lbs of force to compress the coil 1", correct?

So beyond that first inch, does that mean than it will take an additional 500lbs of force to compress the coil another inch? I.e., 1000lbs to compress 2", 1500lbs to compress 3", etc.?

For a linear rate spring, Correct.

That is the reason coils like the OME 861 and 891 are progressive. They get more stiff as they compress to handle cargo loads better than a linear rate coil.

 

[1985taylor1925]

I hate to say it, but until you replace those bushings (both upper and lower), this thread is meaningless. I assure you, the difference will be astounding. I mean, its fair to assume these vehicles would've never garnered the reputation that they have, if they were sloppy and unstable beasts from the factory. Bushings are cheap on Amazon, and don't take too long to install. Get on it

This is what you want.

Finally got going on changing the bushing. To this point it has been a massive pain! I only have one control arm off, and havent pressed out the bushings yet. Was trying to use the bottle jack to press them out, and it literally broke.

Anyway, did you re-use the metal sleeve the bushings slide in? And if so, and advice on how to separate it from the rubber? torch im guessing

 

[absalom]

Finally got going on changing the bushing. To this point it has been a massive pain! I only have one control arm off, and havent pressed out the bushings yet. Was trying to use the bottle jack to press them out, and it literally broke.

Anyway, did you re-use the metal sleeve the bushings slide in? And if so, and advice on how to separate it from the rubber? torch im guessing

Pop on down to home Depot and get a propane torch and some map gas. Start burning and yes, you'll reuse IIRC.

 

[4-Ripcord]

Finally got going on changing the bushing. To this point it has been a massive pain! I only have one control arm off, and havent pressed out the bushings yet. Was trying to use the bottle jack to press them out, and it literally broke.

Anyway, did you re-use the metal sleeve the bushings slide in? And if so, and advice on how to separate it from the rubber? torch im guessing

I recently went through the same ordeal when changing to poly bushings.

Yes you leave the outer sleeve in the arm. You must press apart the inner collar (it has a press fit washer on one end) then remove it and torch or scrape out the rest of the rubber.

Use this thread and scroll down to when he starts talking about the lowers:
https://www.tacomaworld.com/threads/how-to-replace-upper-lower-control-arm-bushings.280375/

 

[PATCO]

A little late to the party. Something is definitely wrong with your runner! It sounds like you might have it figured out. If you really hate the rack you could do a rear swing-set with a box like this Tacoma!