Time for C-Bushings. Which degree should I get?

[Bustedbroc]

74 EB U15. 302 V8 3 speed with Koenig PTO winch. Pretty much bone stock except a previous owner removed the full top and added a half cab with roadster inserts. Front end good and tight, new ball joints up/down, New springs front and rear. Front end was professionally aligned after work was done. I DID NOT replace the C bushings yet. Maybe 300 miles driven since.
Currently the trucks drives pretty good but can wander with a little speed and rough roads. The AFTER alignment specs show that I need to get Positive Caster back. Specs read:
CAMBER 1 degree (L), 1 3/8 (R)
TOE 13/64 (total) 3/32 (L), 7/64 (R)
CASTER - 1 1/2 (L+R)
Truck does NOT have a lift kit on it but may sit a bit higher than normal (hard for me to tell, see attached picture. FYI, 31" tires) since it does not have a full top and with the Koenig winch the front springs I had to use these from Jeff's BG, https://shop.broncograveyard.com/19...l-Springs-1-1_2-2-1_2-Lift/productinfo/13201/. These are approx 2" taller that the stock 16" spring and matched what was removed from the truck. See my previous post: "Front coil spring puzzle"
I am of the thought that 4 degree bushings would be the correct choice to get me back within spec of 2-4 degree positive. Question, when these C-bushings get old and tired does the truck start to lose positive caster?

Suggestions and comments on which
C-bushings to get greatly appreciated.

on which

 

[DirtDonk]

You’re in a great position to do this, since it is currently driving. But also even better, because you have the current caster specific settings from a previous read out.
Have the c-bushings ever been changed? Can you tell if they’re still stock rubber, or if they are polyurethane? If you don’t know, shoot a picture of the bushing area and let us see it.
Which bushings you have now will help dictate which bushings you need.

 

[Broncobowsher]

Next question, do you have power steering?

If the bushings are stock rubber (0°) I would guess you would want 4° bushings with manual steering and 7° bushings with power steering.

 

[Bustedbroc]

Wow, you guys are quick! Here is a pic of the old ( I would be shocked if they were not original) rubber bushing. And yes, I have power steering. I have been soaking the bolts with PB Blaster praying the bolts don't snap on me.

 

[Bustedbroc]

You’re in a great position to do this, since it is currently driving. But also even better, because you have the current caster specific settings from a previous read out.
Have the c-bushings ever been changed? Can you tell if they’re still stock rubber, or if they are polyurethane? If you don’t know, shoot a picture of the bushing area and let us see it.
Which bushings you have now will help dictate which bushings you need.

Old rubber, pls see pic

 

[bronco italiano]

Originals!!!

 

[DirtDonk]

Well, next question is, do you ever use four-wheel-drive in high range?
And the final question (I think) is, are those numbers on the alignment sheet positive or negative?
Presumably they’re positive, and 1.5° is about normal for your year.
If you add 7° bushings, you’ll be in the high 8° range at that point. Way more than enough caster for a happy driving experience. But possibly too much for your front pinion angle to keep a U-joint happy.

4° bushings give you 5 1/2, which is pretty darn good. So keep the pinion angle in mind when you are choosing.
Nothing wrong with having 8+ degrees of caster! Just that you have to compromise sometimes to make everything work nice together.

 

[Bustedbroc]

Well, next question is, do you ever use four-wheel-drive in high range?
And the final question (I think) is, are those numbers on the alignment sheet positive or negative?
Presumably they’re positive, and 1.5° is about normal for your year.
If you add 7° bushings, you’ll be in the high 8° range at that point. Way more than enough caster for a happy driving experience. But possibly too much for your front pinion angle to keep a U-joint happy.

4° bushings give you 5 1/2, which is pretty darn good. So keep the pinion angle in mind when you are choosing.
Nothing wrong with having 8+ degrees of caster! Just that you have to compromise sometimes to make everything work nice together.

To answer your good questions, the chances of using 4 wheel in high range is slim to none. This is my summer toy. Those alignment numbers for CASTER are NEgative! That is kinda why I inquired about old C bushings losing positive caster over time? I was under the impression 2-4 degrees positive was factory and a target #. to shoot for. If the degraded C bushings made it now negative (or the possible slight lift), 4 degrees would put me right in the sweet zone?

 

[DirtDonk]

The 2 to 4 was the factory target. Rarely reached, as far as we’ve been able to discover.
Member James Roney seems to have had good luck finding stock Broncos with reasonable caster numbers. But none that I’ve ever had or worked on, and many of those here on the forum, have very low numbers as well.
Yours are a little crazy though, being negative, even with the stock bronco!
Unless perhaps the rear end is stinkbug high, which would skew the readings.

But if those are truly negative numbers, then I would just default to the 7° bushings as was recommended before. Get as much of it back as you can, and then worry about the opinion later.
And as you may have read around here, the ultimate alternative, if this doesn’t work out, is to cut and turn the steering yokes so that you can have both good caster and goodpinion angle.

 

[Broncobowsher]

2-4 was factory target when manual steering was standard. Step up to '78 specs and the caster numbers go way up once power steering was standard. I want to say around 6° without finding my books on it. A +7° correction bushing on a -1½° would give a very nice driving +5½° of caster.

 

[dmoses42]

2-4 was factory target when manual steering was standard. Step up to '78 specs and the caster numbers go way up once power steering was standard. I want to say around 6° without finding my books on it. A +7° correction bushing on a -1½° would give a very nice driving +5½° of caster.

Since I'm not knowledgeable really at all on caster and camber numbers, except for what I've read here on CB, why would there be different target numbers for a vehicle with manual steering as opposed to power steering? I'm trying to learn more every day. Thanks.

Don

 

[Broncobowsher]

Within reason, higher caster will want to self center more. Takes more force to turns the wheels off a straight line. Makes them want to drive straight down the road. Power steering has the power to overcome this and you don't notice it. It is still easy to turn. But without steering input it will want to drive in a straight line. The steering will naturally want to go straight.

With manual steering the efforts would be noticablely higher. Reducing the caster removes the self centering action and allows easier steering. You are not fighting the steering wanting to self center as much. To some extent, you have to turn the steering to get out of a turn where more caster will straighten itself. This is where the dartyness starts happening. There is no, or little, self centering and it starts wanting to be in a turn and not go straight. So you are chasing it putting steering inputs in to nudge it back into a straight line.

 

[Bustedbroc]

Within reason, higher caster will want to self center more. Takes more force to turns the wheels off a straight line. Makes them want to drive straight down the road. Power steering has the power to overcome this and you don't notice it. It is still easy to turn. But without steering input it will want to drive in a straight line. The steering will naturally want to go straight.

With manual steering the efforts would be noticablely higher. Reducing the caster removes the self centering action and allows easier steering. You are not fighting the steering wanting to self center as much. To some extent, you have to turn the steering to get out of a turn where more caster will straighten itself. This is where the dartyness starts happening. There is no, or little, self centering and it starts wanting to be in a turn and not go straight. So you are chasing it putting steering inputs in to nudge it back into a straight line.

Thanks ALL. I am starting to understand. I have only owned this truck for 1 1/2 years but I can't help but wonder what happened to whatever positive caster it should have had.

 

[Bustedbroc]

Should I go POLY or RUBBER for ease of installation?

 

[Broncobowsher]

The camber correction bushings are only available in poly.
There is no camber correction option in rubber bushings.

 

[Bustedbroc]

OK, thanks.

 

[DirtDonk]

Nor caster correction either!

 

[jamesroney]

Thanks ALL. I am starting to understand. I have only owned this truck for 1 1/2 years but I can't help but wonder what happened to whatever positive caster it should have had.

Until you confirm the height of your lift kit...you will continue to wonder. (and wander...) I know you think you don't have a lift kit...but you do.

Measure the distance from the top of the axle tube to the bottom of the frame, and compare that number to the one's posted by @DirtDonk (Factory was 7 in the front, 6 in the rear.)

Factory rubber bushings tend to wear out and cause decreased caster. I can see where your old bushings are squished. The axle wants to roll forward in the c-mount. Disc brakes makes this much worse. (because the Bronco actually has braking force...) Putting new disc brakes on old rubber c-bushings will actually change caster in just a few miles.

This is why I never trust alignment measurements on old bushings.

Tell me your ride height, (distance from front axle to frame, and distance from rear axle to frame) and I will tell you which POLY bushings you want. The Bronco vendors have gone to great lengths to improve the suspension on these old Broncos. You can benefit from their research.

 

[dmoses42]

Within reason, higher caster will want to self center more. Takes more force to turns the wheels off a straight line. Makes them want to drive straight down the road. Power steering has the power to overcome this and you don't notice it. It is still easy to turn. But without steering input it will want to drive in a straight line. The steering will naturally want to go straight.

With manual steering the efforts would be noticablely higher. Reducing the caster removes the self centering action and allows easier steering. You are not fighting the steering wanting to self center as much. To some extent, you have to turn the steering to get out of a turn where more caster will straighten itself. This is where the dartyness starts happening. There is no, or little, self centering and it starts wanting to be in a turn and not go straight. So you are chasing it putting steering inputs in to nudge it back into a straight line.

This makes sense. Thanks.

Don

 

[jamesroney]

Since I'm not knowledgeable really at all on caster and camber numbers, except for what I've read here on CB, why would there be different target numbers for a vehicle with manual steering as opposed to power steering? I'm trying to learn more every day. Thanks.

Don

Think mountain bicycle vs road bicycle... or dirt bike vs street motorcycle. The more vertical the front fork, the easier it is to turn.

The reason for this is because the angle of the fork causes the frame to lift when turning. The more angle, the more lift. So the weight of the bike forces the wheel to go straight. Conversely, every time you steer away from center...you are raising up your Bronco.

If you've ever tried to ride with no-hands on your mountain bike, you know exactly what too-little caster feels like.

Same rider, same weight, same speed, same tires on your old 10-speed...and totally stable with no-hands.

Keep in mind that as the wheelbase increases, and the weight increases, you can get by with less caster.

The Early Bronco caster specification was invented in 1966 with manual steering, 6 inch wide bias ply tires with "modest" steering effort. It was never right.