Independent Suspension Alignment

[pcampbell]

I've been contemplating tackling putting independent suspension on an upcoming trailer project. I've seen brief mention on wheel alignment suggestions, but have not seen a dedicated thread with in depth information.

So, if you have some good information, specs, or thoughts, please share. The goal is obviously a straight towing trailer with no sway, and no goofy "self steering" characteristics.

Some fuel for the fire...

1) How much toe?
2) Does trailer track width and/or wheelbase make any difference on the alignment settings?
3) What about camber?
4) How did you, or would you, design in adjustments for alignment? Or just get it all right the first time and leave no adjustment?

:coffeedrink:

 

[UK4X4]

1) How much toe?

its a trailer no toe in required-

2) Does trailer track width and/or wheelbase make any difference on the alignment settings? no

3) What about camber? none although you could pre stress to take into account the movement in the steel

4) How did you, or would you, design in adjustments for alignment? Or just get it all right the first time and leave no adjustment?

Aim to get it right first time measure measure measure- tack weld beat back into place and continue.

I used a complete straight 3500lbs axle tacked in place, then welded the arms , then cut out the middle

Mine is bolted on with 4 off 12 mm bolts per side

So can adjust by either using shims for camber
slotting holes for toe in alighnment

Bump steer is part and parcel of a flexible off road suspension on a trailer

I used gas shocks--which i think was a mistake as they are sprung loaded as such and pushing the same way as the air bags.

One day i'll replace with oil.

This is not a cheap or quick route, the benifets off road are great but a nicely shocked leaf spring setup would suffice for all but the narliest trail.

Thats a long set of leafs from a samurai - yj or similar not the standard 24" think 36"- nice long pivots- and matched oil shocks- rancho 6000-9000

On this motorcycle trailer I built I used the 2 largest leafs from a Hilux pickup

Holds to desert setp CRF450X with 20-24 ltr tanks and still has flex.

On a recent unladed desert dash I hit a sand dune and launched 4 wheels off with this in tow, ripping off the wheel arch on one side, making the other one circular and destroying the front dolly wheel completely....so yep flexi !

 

[ntsqd]

With an IRS there is a toe setting. Mostly this is to offset bushing deflection, but there are likely some stability or handling trait nuances to just how much. For a trailer I've stopped thinking about toe-in once any bushing deflection is accounted for.

I'd not worry about camber, and I would set the trailing arm pivot axis perpendicular to the frame's centerline. Any angle other than 90* relative to the centerline will introduce both toe changes and camber changes in wheel travel. While there may be something to be gained from looking at a camber curve for a trailer I suspect that it will be so far out at the fringe edge of normal use as to not be something to worry about.

What ever your adjustment method is, it should feature positive control of how far you move it. A slotted hole works, but only by maintaining tight fasteners does the setting stay in place. I'm more inclined to use a tie rod end or something similar for the adjustment. Then something has to spin around the threads for the setting to change.

 

[R_Lefebvre]

I would think that a bit of toe in on the trailer would actually help it track straighter and prevent sway, much the same way it helps on the rear of vehicles.