Custom Suspensions Tech - Revisited

[Herzog]

This subject seems to have been beaten to death in the past. With all the new advancements in our hobby / sport, I think it is time to revisit the subject.

Let's talk about:

• Coilovers vs. Airshocks
• 3 links, 4 links, triangulation methods, back to trackbars, etc... What advancements have been made?
• Leaf spring tech: why flatter springs are better than highly arched springs, methods to improve leaf spring performance, why revolvers bit the dust, etc...
• Is too much flex bad / over-rated?
• Discuss new suspension joints and other new technologies...
• Hydrostatic suspensions? Useful or overcomplicated and useless?
• Designing for slow and fast terrain

The list goes on. Lets get technical and revisit suspensions!

If we get some really good discussion out of this, I will later seperate them into their own threads as to keep them flowing and on topic.

 

[troutbum]

• Designing for slow and fast terrain

I started over with my rig because I wanted something more dual sport...I don't know if it is truly possible to have a solid 4+ trail rig and a rally, 75+ MPH whoops and jumping rig. But I would like to get as close as possible...seeing the video from the BFE comp, where they were airing out a lot of those rigs makes me think a guy could get close.

I would like to hear from anyone who thinks their rig is good at both...

 

[AINT SKEERED]

[*]Is too much flex bad / over-rated?

Although I dont think you can have "too" much flex, I think its highly overrated. Its about traction, always has been always will be. Flex can lead to traction, but it can also hinder, i.e. axlewrap, flexsteer.

[*]Designing for slow and fast terrain

I'd like to hear what people think about IFS and IRS suspensions as they relate to the XRRA.

 

[Herzog]

Although I dont think you can have "too" much flex, I think its highly overrated. Its about traction, always has been always will be. Flex can lead to traction, but it can also hinder, i.e. axlewrap, flexsteer.

I have always believed in an Optimum for everything. Too little flex and you won't get the traction and stability that you need. Too much flex causes other problems INCLUDING instability.

I've never been a fan of the RTI ramp and I believe it should not be a goal setter for suspension building. In my past experience, the more flex I built into a vehicle, the more I limited it later on because of its behavior on the trails. Travel is good... too much travel is silly. And yet, every vehicle is different with how it acts accordingly to the amount of travel it has. I just don't think the amount of flex your vehicle has is a show off point anymore.

 

[Herzog]

I started over with my rig because I wanted something more dual sport...I don't know if it is truly possible to have a solid 4+ trail rig and a rally, 75+ MPH whoops and jumping rig. But I would like to get as close as possible...seeing the video from the BFE comp, where they were airing out a lot of those rigs makes me think a guy could get close.

I would like to hear from anyone who thinks their rig is good at both...

I would too. Mine can cruise down the trails fast, but by no means can it actually "rally". In my mind, I think one of the biggest obsticals to get over would be tuning a suspension that would soak up the big speed hits and yet be limber and soft enough to traverse rocky terrain at a required slow speed.

It would be cool to see some actually numbers and tech pertaining to a similar scenario.

 

[Milner]

Talk about opening Pandora's Box!!

All I have to say is; It is all a compromise and there is NO ideal setup everything/everyone. Set it up to YOUR liking.

 

[Herzog]

Talk about opening Pandora's Box!!

All I have to say is; It is all a compromise and there is NO ideal setup everything/everyone. Set it up to YOUR liking.

This is true... but it's fun to talk about!

I really want to see some new concepts and why people believe it is working well for them. We haven't had a good suspension thread in ages!

 

[Shawn]

I am so happy with my 4 link I'm like a gitty school girl. It works and I think it works well. One thing that I found that was important in the link design was the lenth. Carl told me when I was building it to make the links as long as possible, well I did, and it worked, no rear steer. Also, I have had a hard time changing over to coilovers in the front. The current set up with 44044's works really well. Good stability and flex. If I could just stop bending the springs I would be happy.

 

[Bart]

Hmmm, so many points to cover.
Yes, I think there is such a thing as too much flex, as seen in many "floppy" rigs
I'd run coil overs over air shocks if the room was available, because I feel they are more predictable.
There are plusses and mineses to 4 links and 3 links, but I still like both.
My TJ will eventually run a 4 link in the rear with coils, and a 3 link in the front with coil overs.
Bump stops and limiting straps solve many suspension problems.

 

[BlackDog]

So, can this get broken down to a suspension 101 type thread?
for example, one of the other Utah based boards that I cruise, some of the guys are here as well, the rig I am thinking of has a cornicopia of springs, waggy, then chevy then so on and so forth per each spring pack.

Why? Better flex would be the obvious
How did he come up with that? trial and error, numerical calculations off of spring rate and temper calibrations?
How does the weight of the rig effect spring choice? you would think alot, but if Toyota guys, say are running Chevy half ton springs in their 4cyl. truck, then ...... that throws the originally designed weight load of the spring being a hindrance out of the equation.
Lastly, if all springs are center pinned and held together in the pack differently per mfr., then how do you swip and swap and have it hold?

(told you this was a 101 type post)

 

[Herzog]

So, can this get broken down to a suspension 101 type thread?
for example, one of the other Utah based boards that I cruise, some of the guys are here as well, the rig I am thinking of has a cornicopia of springs, waggy, then chevy then so on and so forth per each spring pack.

Why? Better flex would be the obvious
How did he come up with that? trial and error, numerical calculations off of spring rate and temper calibrations?
How does the weight of the rig effect spring choice? you would think alot, but if Toyota guys, say are running Chevy half ton springs in their 4cyl. truck, then ...... that throws the originally designed weight load of the spring being a hindrance out of the equation.
Lastly, if all springs are center pinned and held together in the pack differently per mfr., then how do you swip and swap and have it hold?

(told you this was a 101 type post)

I would have to say trial and error on that. To simply take particular leafs out of individual packs and essentially create a custom spring with a rate to your liking would be mind numbing mathematically to figure perfect rates.

Usually you can figure out what you need by eyeball estimation and see if it works for you. You already know that a spring rate of a leaf under a heavier vehicle will be higher, a lighter vehicle will be a different rate... so you compile accordingly.

But you need to be carefull, because when you come up with a flexy soft riding spring under a considerably heavy trail rig the chances of bending or breaking those springs increase. (ie: you wouldn't put jeep YJ leafs under a 1 Ton chassis and see them last very long, although the ride would be incredibly soft.)

As for center pins, I've seen people drill out center pins and use larger sizes to bring all of the holes in pack to the same size. I don't know if this weakens the integrity of the pack at the center or not, I would assume that it does.

 

[BlackDog]

Thanks.

 

[Herzog]

Thanks.

I honestly don't know if I answered your question or not.

 

[I Lean]

There is a solution to every problem, and a problem with every solution when it comes to suspension design.

Regarding linked suspensions, you have many options to choose from to control your axle and allow travel and articulation. In general, you need something to keep the axle from twisting around the axle shafts ("axle wrap" for leaf sprung applications), something to keep it from moving side to side, and something to keep it from moving front to back. Those can be seperate, dedicated links to do each job (like a 4 or 5 link system including a panhard bar) or the links can "share" jobs like a triangulated 3 or 4 link.

As long as you have the control you need, now you need to determine if your system will allow the axle to move in the directions you DO want it to, up and down for suspension bump and droop, and twisting for articulation. Some setups will allow basically unrestricted motion in those areas, some bind. (a little bind may or may not be a bad thing, that depends on the joints chosen for the end of the links though)

Now that you have both your control and your freedom figured out, you need to determine how the axle will move during both compression/droop and articulation. Even if your setup allows unrestricted travel throughout the range of motion you desire, it may move in ways that aren't good for the handling of the vehicle. You may have unacceptable amounts of axle steer, it may tend to "jack" the vehicle under power or braking, etc.

Now that you have all that figured out and are happy with it, you can decide what you want to use to hold the vehicle up. Coil springs, leaf springs (either semi-elliptic or 1/4-ellliptic), airshox, airbags, anti-gravity. The shock absorbers can be seperate from the shock, they can be packaged together in the form of a coilover shock, or combined in the case of an airshock. (where the pressure of the nitrogen inside the shock actually holds the weight)

All have their pros and cons, but it's really hard to say that one is superior to another in every circumstance. A great link setup can perform poorly with the wrong shock/spring selection, and a poor one could be OK with carefully planned spring rate and shock valving.

Coilover shocks are generally regarded as "best", but I think that's primarily because you get a very high-quality shock in the package, and very adjustable spring rate and shock valving. They're nice to use for packaging reasons, since they're small and self-contained. Airshox are nice for the same reasons, but don't have nearly as much available tuning options since the spring and shock are not seperate. A seperate coil spring and high-quality shock will perform every bit as well as a coilover shock, all other things being equal.

Any questions? I'll bet I raised more than I answered....

 

[I Lean]

I started over with my rig because I wanted something more dual sport...I don't know if it is truly possible to have a solid 4+ trail rig and a rally, 75+ MPH whoops and jumping rig. But I would like to get as close as possible...seeing the video from the BFE comp, where they were airing out a lot of those rigs makes me think a guy could get close.

I would like to hear from anyone who thinks their rig is good at both...

In regard to this, I do think my rig is good at both--it definitely does the slow speed stuff very well, and feels great at higher speeds--but higher speed to me doesn't mean 75+ MPH, either. I'm sure I couldn't begin to keep up with a dedicated go-fast machine in the terrain it was designed for, and vice versa.

 

[Tacoma]

There is a solution to every problem, and a problem with every solution when it comes to suspension design.

true enough. The monster truck is getting leaf springs, and for the money and ease of installation they're great, but they're not perfect. Being so long, the axle is going to move around a little, which means clearancing body and drivetrain to take that into account. That also means super axle-wrap, esp. with a big block and Rockwells. So I need to make some kind of appropriate axlewrap-limiting device.

If I had my druthers I'd link it, but that's a boatload of work for that rig, and it's just not worth the time, expense, and general complexity. For the kind of use it's going to get, long flexy leaves will do just fine.

Moon buggies are a great example of the engineering having to fit the purpose and what kind of result you get.