More Caster/Alignment/drivability ideas?

[hsach]

This is a great discussion, I am learning a lot. My setup will be close to Torkman66's with lift and tires. After reading all of this, I can't wait to get mine on the road to see how my Caster angle measures. I am hoping I didn't guess wrong on my C bushings, I put 2 degree bushings in and now I think I should have gone with 0 degree rubber ones. My 67 has the Tom's dana 44 with 4 degrees of positive caster built in, and I put on the T-Rex arms, I think those have 4 degrees of positive caster.

I wasn't sure if I would need any drop pitman or track bar adjustments when I got it on the road, so I am glad to follow along to see how these things affect your driving/steering Torkman66, very nice build!

 

[Yeller]

or go all in, build a front axle for a different application with full hydraulic steering, then install it in a bronco with a steering box, hydraulic assist and have 11-1/2 degrees of caster, it takes effort to not go straight LOL

 

[Torkman66]

Being the original poster of this thread I have a few observations given all of the input.

1. There are folks in this community that have forgotten more about this subject than most of us will ever know.
2. 7* caster is optimum.
3. Cutting and turning Cs is the right way to fix it.
4. Solutions other than cut and turning are less than optimum.
5. Several other steering components play a part in drivability (none as much as caster).

Important to also recognize a few other considerations.
1. Not every owner has a shop to cut and turn, weld, and install the front axle.
2. Not every owner has the funds to have someone else do that work.
3. Not having the ability or funds does not detract from still wanting to improve drivability ie. leading to other “less optimum” alternatives
4. C wedges, eccentrics, drop arms, etc all improve caster when “the best options” are not attainable and thousands of folks have nice drivable rigs due to these creative alternatives.
5. Folks should do what they can, to whatever ability they have, as long as their decisions are based on good knowledge (obtained in threads like this).

For me, I have a shop, the time, and funds to cut and turn…but at the time I was building the front axle, I did not have the knowledge. I will likely cut and turn eventually, but I’m also very interested to see what effect a drop pitman and bracket will have…that knowledge may help those without the cut and turn option.

Great discussion!!!

 

[toddz69]

or go all in, build a front axle for a different application with full hydraulic steering, then install it in a bronco with a steering box, hydraulic assist and have 11-1/2 degrees of caster, it takes effort to not go straight LOL

We're not building road graders here .

Todd Z.

 

[jamesroney]

^^^this. I don't actually drive 75. My Bronco seems to prefer 80 with the big engine. Of course I have brakes that are up to the task. I have no idea what my tire pressure is right now- seriously. But meanwhile it's one thumb hooked over the steering wheel, completely stable. Ok, I don't have 7 degrees of caster either, only 6.5. Don't believe me? Come to Davis and try driving it.

I believe you.

 

[jamesroney]

Being the original poster of this thread I have a few observations given all of the input.

1. There are folks in this community that have forgotten more about this subject than most of us will ever know.
2. 7* caster is optimum.
3. Cutting and turning Cs is the right way to fix it.
4. Solutions other than cut and turning are less than optimum.
5. Several other steering components play a part in drivability (none as much as caster).

Important to also recognize a few other considerations.
1. Not every owner has a shop to cut and turn, weld, and install the front axle.
2. Not every owner has the funds to have someone else do that work.
3. Not having the ability or funds does not detract from still wanting to improve drivability ie. leading to other “less optimum” alternatives
4. C wedges, eccentrics, drop arms, etc all improve caster when “the best options” are not attainable and thousands of folks have nice drivable rigs due to these creative alternatives.
5. Folks should do what they can, to whatever ability they have, as long as their decisions are based on good knowledge (obtained in threads like this).

For me, I have a shop, the time, and funds to cut and turn…but at the time I was building the front axle, I did not have the knowledge. I will likely cut and turn eventually, but I’m also very interested to see what effect a drop pitman and bracket will have…that knowledge may help those without the cut and turn option.

Great discussion!!!

7 degrees of caster is the minimum for 33'ss. You get some additional centering force from the contact patch centerline moving forward with bigger tires. So with 35's...you can get away with 6.5 degrees.

The Big Mercedes, (and the Maybach) set factory caster at around 11 degrees. Those are big, nose-heavy rear wheel drive road floaters. They soak up miles on the Autobahn, and rarely do anything remotely resembling a dart. The more sporty BMW 7-series runs right at 6.5 degrees.

Someone at Ford decided that it was more important for your 10 year old to steer the Bronco around the farm than to drive the Bronco to the farm. In a cruel twist of fate, the alignment specification number was published in a book. For some reason, Ford Motor Corporation, their entire engineering team, and every automotive alignment expert seems to have more credibility than me.

Keep in mind that these are the same idiots that gave you a Dana 30, 28 spline rear axle shafts, ignored power steering, and didn't discover disc brakes for over 10 years.

You absolutely do NOT need to cut and turn to improve your handling. With Jim Cole's caster compensated radius arms (you call them Duff arms) and 7 degree bushings, you can get 11 degrees of additional caster using your factory un-cut housing. You just can't put a driveshaft in it.

For the truly agnostic, I remove the front driveshaft and bring the front end to 7 degrees of caster. If they like how it drives, then we cut-and-turn.

 

[Shimmy]

I will likely cut and turn eventually, but I’m also very interested to see what effect a drop pitman and bracket will have…that knowledge may help those without the cut and turn option.

Great discussion!!!

those are different aspect, both will improve driveability tho. a drop pitman and bracket have nothing to do with caster. you likely know this, but wanted to clearly state that since some folks may think a cut and turn will solve bumpsteer/roll. it will not.

 

[Broncobowsher]

those are different aspect, both will improve driveability tho. a drop pitman and bracket have nothing to do with caster. you likely know this, but wanted to clearly state that since some folks may think a cut and turn will solve bumpsteer/roll. it will not.

That is correct.

And there is a whole other rabbit hole in modern alignments as the SAI (Kingpin inclination) has changed a lot on modern vehicles as well.

 

[Yeller]

Someone at Ford decided that it was more important for your 10 year old to steer the Bronco around the farm than to drive the Bronco to the farm. In a cruel twist of fate, the alignment specification number was published in a book. For some reason, Ford Motor Corporation, their entire engineering team, and every automotive alignment expert seems to have more credibility than me.

That is correct.

And there is a whole other rabbit hole in modern alignments as the SAI (Kingpin inclination) has changed a lot on modern vehicles as well.

Its still being perpetuated by Ford.... just look at the alignment specs for a brand new Super Duty. In regard to caster, if your truck is at the high end of the allowable tolerance, you are typically ok, if it is on the low end of the allowable tolerance, you are going to have death wabble, it is not a matter of if but when. Add some caster and magically it disappears, provided the tires are round. however, this is all a different rabbit hole, sort of, and more of a rant that just proves Ford has had and still has some jacked up engineering ideals, that are still jacked up today.

 

[ksagis]

Now, to answer a different question: "How can I reduce the darty-ness of my Bronco?"

1. Run 7 degrees of Caster.

I’m already north of 7 degrees of caster as measured by two alignment shops.

I’m hoping to get to something like @lars described, 75 mph and lovin it!

 

[jamesroney]

I’m already north of 7 degrees of caster as measured by two alignment shops.

I’m hoping to get to something like @lars described, 75 mph and lovin it!

Ok, your are at 7 degrees of caster, and still darty?

How does it drive with the power steering pump disconnected?

( Or coasting when the engine is turned off.)

 

[Torkman66]

@Shimmy agree and understand. I'm trying to determine if my steering with 4.1* caster is "OK" and the issue I am having relates to bump steer. It drives pretty well straight down the road. Does not wonder. But hit a dip or worse, hit a dip while in a turn, and it darts out of the lane. If that is a function of bump steer and the pitman and bracket improve that issue, I'd be OK with how it drives. If not, then I'll be taking apart my powder coated front 44 and doing the cut and turn.

 

[ntsqd]

I will suggest, based on posts within this thread, that 4.1° of Caster is not enough. It is almost, but not quite enough.

The changing direction on hitting a bump is Bump-Steer. We've been over what the relationship between the drag-link and the trac-bar needs to be to reduce or eliminate it. Don't be surprised if that finds you heating and bending or cold bending the pitman arm in a press to get the drag-link is the correct relationship.

 

[DirtDonk]

That’s not just your typical basic dartiness. What you are describing is actually bump steer!
OK, so that is darty. But now you have the cause.

I’m one of those that, while I know that up to a point more caster is better, I can drive my 71 at 80 miles an hour as well, and I only have 2° of caster.
I also have manual steering, 7 inch wide wheels, with 11 inch wide tires, in either 32 or 33 inch sizes. With about 3/16 inch toe in.
A 3.5 inch lift, with a track bar drop and a dropped Pitman Arm. Modified F150 steering links.
I should actually have bump steer, but the manual steering minimized it by allowing the steering box to react instead of the whole vehicle.
When the steering wheel wanted to move an inch or so, instead of holding it solid, I would just let it float through my hands.
Not actually a perfect set up, but it drove that way,

 

[DirtDonk]

Don't be surprised if that finds you heating and bending or cold bending the pitman arm in a press to get the drag-link is the correct relationship.

Or custom making a track bar drop that puts it in just the right spot.

 

[ntsqd]

Sometimes it's easier to bend something than it is to move some holes a 1/4"

 

[DirtDonk]

Sounds like experience talking…

 

[Johnnyb]

I am following this conversation with great interest. As I said before, I am pleased/surprised at how well mine handles. Even with 7° bushings and Duffs stock length T-Rex arms, I seem to end up with about 5° of caster?

-JB

 

[DirtDonk]

Seems reasonable.
Do the T-Rex arms add 4°? If so, essentially you added 11° of caster to whatever it would’ve been naturally. Something like -6!

So what year is your rig again? And how much lift?

 

[Johnnyb]

Seems reasonable.
Do the T-Rex arms add 4°? If so, essentially you added 11° of caster to whatever it would’ve been naturally. Something like -6!

So what year is your rig again? And how much lift?

It's a 71 with a Dana 44 out of a 76, it's got a two and a half inch wild horses lift and 7° bushings.