3-link vs 4-link suspension

[Ecranu]

I'm currently running my Wraith on a 3-link suspension up front.

I primarily enjoy trail-riding and crawling, but might look into increasing speed down the road. What are the advantages/disadvantages between a 3-link and 4-link?

TIA

 

[3stage]

Would like to see the responses to this question. I personally prefer 4 link design over the 3 link (with CMS).. I always believe the 4 link will be more rigid and axle mounted servo will be more responsive for high speed.

 

[altd896]

Main advantage of 4 link is it gets rid of the drag link & panhard being tied to the chassis & them limiting suspension travel.
That of course is countered by the fact you then have the servo on the axle getting into the chassis instead of the draglink/panhard & it's not very scale, if that's your thing.
You can get around that if use a Dlux truss with the servo behind the axle.

Set-up correctly, neither will make any difference to your steering response or power, unless you have to change servo arm length to get one set-up to work over the other.
As for handling at speed, I don't think it's coincidence that most U4/KOH style truck seem to use 4 link & axle mount ram power steer.

 

[Ecranu]

Did some additional research. I don't know how much this applies to RC, but at 1:1 scale, the 3-link is viewed as an upgrade.

4-link is preferred for straight-line racing/drag. 3-link offers an improvement in cornering.

Thoughts?

 

[fyrstormer]

A panhard link will always force the axle to move sideways when the suspension moves up or down. Given long-enough suspension travel, the amount that the axle moves sideways could become problematic.

 

[maslin]

Did some additional research. I don't know how much this applies to RC, but at 1:1 scale, the 3-link is viewed as an upgrade.

4-link is preferred for straight-line racing/drag. 3-link offers an improvement in cornering.

Thoughts?

We aren't dealing with straight line, drag racing, or performance cornering. Full hydro steering is the standard on serious offroad trucks. Some of the faster U4 guys have been playing with other systems, but their problems aren't the same as ours. The down side of full hydro is speed and steering feed back. Our servos are plenty fast, and steering feel is a non issue on RCs.

A panhard link will always force the axle to move sideways when the suspension moves up or down. Given long-enough suspension travel, the amount that the axle moves sideways could become problematic.

Very true. Even if you set your steering and panhard up correctly to eliminate bump steer, the entire assembly shifts side to side throughout suspension travel.

 

[3stage]

What about steering geometry? I've read it is ideal to have the drag link parallel to the tie rod for best performance..

 

[maslin]

What about steering geometry? I've read it is ideal to have the drag link parallel to the tie rod for best performance..

Drag link parallel to panhard bar, assuming you have a chassis mounted servo (or a steering box in 1:1 world.)

The closer to parallel the tie rod is to the drag link the better, but you're only talking about the force pushing at an angle vs straight. Not that big of a deal in our application.

With an axle mounted servo the drag link and tie rod will be very close to parallel, usually.

 

[fyrstormer]

If you can't get the steering link and the panhard link to be parallel, you shouldn't bother with 3-link suspension at all. Every time the axle moves up or down or tilts to one side, the steering angle will change, and you'll have to fight it.