Front end wander

BUFFALO · 11-29-2016, 10:50 AM

Hi all,

The short story is that I would like to add some caster to the front end which currently has about 2*.
The question is how much?

The longer story is that it is a Salem Kroger leaf sprung conversion with a 2000 F350 ball joint Dana 60. It has the shackles at the front and a trac bar.

I know there are issues with these conversions and I'm not trying to make it significantly better. But some improvement would be nice if I can.

It was just aligned and has 2* of caster now and camber and toe are at 0.

It has 4 new ball joints.
The drag link and tie rods are tight although they do twist and I am going to try and 'clock' the tie rod so it doesn't rotate as much.

The steering also has a bit of play and I am going to see about tightening the box a bit. I have had success on other vehicles even though I've read horror stories about the steering for some people locking up.

I may be getting some bump steer from the drag link angle but short of doing a high steer, I can't do much about that now.
The van is lifted somewhere between 4-6 inches maybe.

I would like to install some caster sleeves to get some more caster. I have read that 4-5* and even up to 6* in some instances works well for people.

I was thinking about going for the 3* sleeves first to see how the high end of it feels.

What do you guys think? Should I start with smaller adjustments?
Does anyone have personal experience with the adjuster sleeves that can provide any info on how things changed?

Thanks a lot.

mgmetalworks · 11-29-2016, 12:01 PM

3.5 deg will be a big improvement. My kit's baseline is 3.5 deg and the vans handle really well. We can also add in another couple degrees with some minor mods or ball joint bushings and get up to 4.5-5.5 deg. Steering effort increases slightly but it's not an issue. At 6 deg you'll have quick return to center but more steering effort and driveline angles start to get funky. My opinion is that much caster isn't necessary. My van started at 1.5deg and with my suspension upgrade, I got up to 3.5. Huge improvement! I'll probably set up for 4.5-5 once its back on the road.

MountainBikeRoamer · 11-29-2016, 12:36 PM

Not to hijack this thread -- but I'm paying attention here too...

Just got my 2WD van back from having a lift-kit installed, and even with the caster angles set to the higher end of the range (somewhere around 4.5 degrees on the right, 3.7 on the left), the van is a lot more prone to wandering now than it was before. It drives straight when you let go of the wheel, but it has a lot of twitchy "bump steer" wander and deflection that needs to be paid attention to.

Of course, at the same time, the tire size has now been also increased significantly (went up from 245/75r16 to 285/70r17) and I'm guessing that the "extra tire leverage" magnifies any tendency in the front suspension to be pushed left/right and wander when hitting bumps or road imperfections.

Previously the van tracked great --- I think it had a lot more caster built into it (my alignment guy has a long history of working on E-series vans and recommended really maxing out the caster to get a great-tracking result for highway cruising.) Hoping to gain back a lot of that caster with another alignment attempt in the next month or so.

I think Ford's officially-spec'd "acceptable range" of caster angle (for the 2WD) is between 2 degrees and 7 degrees, but most people seem to aim for the higher end of the range (at least 5 degrees) to really "cure" the wandering symptoms of these vans. Is that the same "ideal number" for you guys with 4WD?

MountainBikeRoamer · 11-29-2016, 12:46 PM

I keep coming across this same information in various RV threads...

.....does this opinion (and set of tech numbers) sound on-par with most of your experience/preferences/results?

From this thread:
E350/E450 Handling Problems are caused by too little + CASTER

"Our 2004 E450 28 Foot handled terrible until we added additional + Caster to the front wheels.

The Ford Spec for front end CASTER is:

LH +1.3 to +6.8 Degrees
RH +1.8 to +7.3 Degrees

Our unit was:
LH +3.3 Degrees
RH +3.5 Degrees

We added + 2.0 degrees, so we are now at:
LH +5.3 Degrees
RH +5.5 Degrees.

Alignment problems on the E series follow the 80/20 rule in the sense that TOE and CAMBER is 20% of the story while CASTER is 80% of the story. TOO LITTLE CASTER will amplify any external force many fold to the detriment of stability.

If your unit feels like the steering box needs to be tightened up it is because of TOO LITTLE + CASTER.
If cross winds and wind gusts cause havoc it is because of TOO LITTLE + CASTER.
If you think the tail is wagging the dog it is because of TOO LITTLE + CASTER.
If you are needing to drive it all day and never relax it is because of TOO LITTLE + CASTER.

If your unit drives GREAT, like an SUV, it is because you have a proper amout of + CASTER which I am guestimating to be about +5.0 degrees or more. (Note: The RH caster is always more then LH (CROSS CASTER = LH - RH))"

mgmetalworks · 11-29-2016, 12:57 PM

Straight axles don't behave the same way as independent suspensions. It's easy to set up a straight axle to drive nice. TTBs are a different story.

carringb · 11-29-2016, 01:05 PM

You can add caster with shims on leaf springs. An easier but less precise way to change caster angle.

carringb · 11-29-2016, 01:10 PM

MountainBikeRoamer - Did you ever adjust your tire pressure down after installing the new tires? If you kept tire pressure the same, you contact patch will be smaller, and that will make your steering feel vague, even when you have enough caster.

MountainBikeRoamer · 11-29-2016, 01:51 PM

Quote:

Originally Posted by carringb

MountainBikeRoamer - Did you ever adjust your tire pressure down after installing the new tires? If you kept tire pressure the same, you contact patch will be smaller, and that will make your steering feel vague, even when you have enough caster.

Hey thanks for the tip there carringb. I haven't experimented with the tire pressure yet, but now you're the second person to mention that. I'll definitely have to see what effect that has.

Right now, the 285/70r17 KO2 tires (front and rear) are all at 50 psi. Van is weighing in pretty evenly at around 3500 pounds per axle.

carringb · 11-29-2016, 02:19 PM

Quote:

Originally Posted by MountainBikeRoamer

Right now, the 285/70r17 KO2 tires (front and rear) are all at 50 psi. Van is weighing in pretty evenly at around 3500 pounds per axle.

Looks like you really only need 30 psi for those wide tires. 35 psi would give you 2,105 pounds per tire, so enough for some extra payload. 40 psi would bump you up to 2,315 per tire if you plan on running even heavier.

MountainBikeRoamer · 11-29-2016, 02:31 PM

Quote:

Originally Posted by carringb

Looks like you really only need 30 psi for those wide tires. 35 psi would give you 2,105 pounds per tire, so enough for some extra payload. 40 psi would bump you up to 2,315 per tire if you plan on running even heavier.

Hey that's good info to have!

For future reference --- can I ask where you're finding those load/inflation specs?

I looked on BFG's website and was only able to find a downloadable .pdf file that gave "max load/max psi" numbers for each tire, but couldn't seem to find any kind of an indexed/scaled "load vs. pressure" range for each tire size.