Front axle geometry / driveshaft binding

[DirtDonk]

...That angle is a slight scrub that the tire will have with the ground. Diameter means nothing to that angle...

That's a good point right there. But that also may mean that wheel offset (as it differs from stock especially) may have a pretty decent effect on how a vehicle responds to toe settings too. More so than tire diameter.
Which I think we have assumed all along anyway, but the whole scrub thing puts it up high on the list for conversation purposes I'm thinkin'.

Paul

 

[tmbuehrer]

the caster measurements I posted in earlier posts was my own preferences and i'll explain why. our broncos are not usually high speed machines, but in my anything over 1.5 degrees positive caster works excellent. when you get to high of caster the tires tend to lean more when turning. starts to rub on shock and other items. also when at full lock could minimize tire contact to ground if caster was excessive. and as broncobowsher said the machine goes off angle, does not know what what tire size. they angles they specify are for stock tire sizes. so alignment angles need to be modified per vehicle. so the larger the tire the vehicle needs less toe, but in my experience 0 toe is not always good. if there is any looseness 0 toe can cause wandering.

 

[tmbuehrer]

I checked the alignment specs on my machine today and it blew my mine. same as yours, 1.5 camber, 3.50 caster. there is no way I would set mine up with 1.5 camber. anything with a straight axle from 1980 and up camber has been set at .0-.3 and they drive wonderful and wear tires good. 1.5 camber would wear the outside edges awfully. I even check the big bronco's(78-79) and same specs. I have a 78 dana 44 in mine and with new ball joints the camber is .3 on both sides.

 

[Broncobowsher]

+1.5° camber was a very common spec from long ago.
But I also prefer a more modern spec closer to 0°

We are running much wider radial tires today as compared to skinny bias ply tires that were the norm back when the specs were wrote.

 

[u10072]

In regards to the original post. If you are going to have a long travel EB -- which is what you have-- you need 1 of 2 things. 1. you rotate the outer C's on the axles so that you can actually have some nice caster nubmers and point the driveshaft at the transfer case. 2. you run a high pinion front end. If you dont use either then what simply is going to happen--you are going to kill the driveshaft as it becomes the limiting strap-- driveshafts make very expensive limiting straps In case you were wondering-- I have 14" travel shocks that fully cycle and with the shocks completely extended with a high pinion Dana 44 I still have more available downward travel in the driveshaft. To me the high pinion is really the way to go but I am able to narrow one and set it up and most cant. Its not cheap really but it is really nice to not have to worry about killing $350 driveshafts-- especially when a narrowed bare front end is about $450.

 

[surfer-b]

Each Bronco is gonna drive/handle a little diff, however when seeting mine up I shoot for camber +.25 on driver, +~.1 pass, I like less camber than spec, tires wear much better. I get good results with toe set at 1/16" pos.
For caster I use the 7* bushings to start with and if I get good return to center I leave it along, if not I will replace with a 4* bushing, get my specs then rotate the yokes and go for 7~8* pos caster. Just keep in mind that when you rotate the yokes back you can loose a little bit of camber.
All these specs are what I use on mine and both have new tie rods and ball joints, 2.5" lifts with TRO's and riser on trac-bar.

 

[driveshafter]

driveshafts

thers a couple places in phx that can accomidate youre travel issues hint my name 20yrs exp

 

[76Broncofromhell]

with out looking at the specs, I can tell you where I would have mine. camber .0 +/-.3 degrees. caster at 2.0 +/-.5 degrees, and total toe .1 to .2 degrees. that's what my ideal specs would be. but I will get ford specs tomorrow at some point. by the way I am a ford master diesel technician and have been doing alignments for years.

I think you need a bit more practice. Ford master techs couldn't figure out why my F-350 pulled to the right from the factory, because all they know how to do is compare specs - not understand them. On my rig, it turned out it was the slight caster difference right to left from the factory - which I would like to add were "within spec" according to all the Ford techs. I fixed it and called back the dealer to get a refund.

Big tires need much more caster than factory specs. Wheelbase also plays a huge part in how much caster will affect driveability. 2 degrees, 35s, 8000 lbs and 140 inches of wheel base is far different than 2 degrees, 35s, 4000 lbs and 92" of wheelbase. A lifted Bronco with 35+" tires will behave much better with between 5-8* of caster. Camber is more of a function of tire wear on a SFA rig, it doesn't have much affect on road manners.

Each Bronco is gonna drive/handle a little diff, however when seeting mine up I shoot for camber +.25 on driver, +~.1 pass, I like less camber than spec, tires wear much better. I get good results with toe set at 1/16" pos.
For caster I use the 7* bushings to start with and if I get good return to center I leave it along, if not I will replace with a 4* bushing, get my specs then rotate the yokes and go for 7~8* pos caster. Just keep in mind that when you rotate the yokes back you can loose a little bit of camber.
All these specs are what I use on mine and both have new tie rods and ball joints, 2.5" lifts with TRO's and riser on trac-bar.

That sounds like a good starting point. If you're looking at DS bind, I would seriously explore the Toyota 4Runner/Pickup driveline option. They are stronger than your stock shafts and plentiful. Plus the factory fronts on the solid axle trucks are close to stock EB lengths.