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

[toddz69]

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.

Since I often participate in tangents in these threads - here's an interesting one that I learned of a few days ago. Some of you are probably aware of the Ineos Grenadier rigs that were introduced a year or two ago. Apparently they were designed with very little caster in their front ends - like 1-2 deg. positive. Owners are complaining about on-road wandering, lack of return to center, etc. The suspension design allows caster to be adjusted about 2 deg. but it's still not enough. Apparently their engineers didn't get the memo.

Todd Z.

 

[dmoses42]

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

Then, too little caster always caused me skinned knees and elbows... LOL

That analogy makes a lot of sense though, and now I understand the reasoning for cutting and turning the inner C's. Thanks.

 

[Bustedbroc]

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.

Ah thanks, didn't see your reply until after (vacation!) and the job was done with 7 degree bushings as suggested earlier in the thread. Did it alone and job was not terrible taking my time. Bushing and bolt kit from WH. Thanks to ALL for the tips on this website.
That was my thought, that caster is lost as the bushings wear. Initial drive around the block seems very good. I need to bring it back for final alignment check and then update this post with the specs. I will also post axle to frame numbers. We will see if pinion angle is going to be an issue but I don't think so. The only bind with the driveshaft I saw was with the truck jacked up and front end hanging down. Turning the shaft by hand there was some interference at the xfer case CV joint. ONce on the ground it was fine and I have no intention of doing any real off roading with it.
One funny thing I noticed, only one of the radius rods had a hole for a safety cotter pin. Not that a nut torqued to 120 lbs should be coming loose any time soon. I double nutted that one.

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

 

[DirtDonk]

One funny thing I noticed, only one of the radius rods had a hole for a safety cotter pin.

Two scenarios I can think of.
One is that, over the years, one of the previous owners had to change out a radius arm. Either for being bent, rusted, or otherwise compromised.
The other is that, being a 74, that’s right about the time a lot of things were changing. Little details, such as going from cotter pins to lock nuts perhaps.

I don’t remember if, during the discussions about this change, we ever narrowed down just what year the arms changed.
But I know when people have a 74 they have to be extra careful when ordering certain parts. Don’t know if radius arms should be added to that list.

 

[Bustedbroc]

UPDATE: Back from the alignment shop. After 7 degree C-Bushings install I now have 5 1/4 positive caster. Truck drives SO much better! They had to take some toe out to correct. Toe is now sitting at 11/64. Left camber is a bit off, (minus 1) while left is +1. I measured axle tube to frame front and rear, measured 9" all around EXCEPT for right rear which was 8". That explains why when viewed from the rear that back right corner appears just a bit drooped. Always did, even before any work done. I do see a weld repair was done on the on the left front part of the frame right at the steering box mount. As if maybe in it's life it took a shot from an accident.

Thanks to all the help here, as always everyone was spot on.