B Codes V2
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Joined: Oct 2003
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From: Tulsa, OK
my rake is probably about like yours. I stated I have about 2 to 2.5" more height in back than front.
I was not sure what the trac bar is used for, so I looked it up. It's job is to keep the axle centered. I can imagine with more than stock lift in front, the trac bar could become off-center, and need to be adjustable.
while perusing the Ford factory shop manual, I realized something. Excessive rake (higher rear than the front) would also reduce caster. Caster as most of us know, helps with the straight-line feel. The more caster, the more the truck will tend to want to stay going straight. Too much caster, and you can barely even steer the truck on the highway. Too little, and it feels like you're driving on ice, constantly correcting.
A low-slung long forked chopper has a ton of caster. a Ricer bike with it's almost straight fork has almost none, comparitively.
as far as I can tell, caster is not adjustable on our trucks. I might be wrong. But if I am correct, then ride height, from front to rear, is important to keep track of. It's the one way it "can" be adjusted.
Too much extra height in back compared to front, will reduce caster and make the truck feel more wandering in a straight line. Even the manual talks about caster and frame angle. This might be why the folks who use 2" hangers in front, report their straight line feel is suddenly so much better. I believe it.
But, then--if you have the front and rear the same hieght, having any serious load in back results in it sagging. I voted for having some headroom for large loads in back, for now. But I am seriously contemplating having my machinist friend shave the rear 2" blocks down to 1" and keep the bump-stop arms. I'll also check Ford and see if there's a stock piece that does this job at 1" instead of 2".
I have noticed, since I did the rear B codes, and have 2-2.5" of rake, that the straight-line feel is not as nice.
I was not sure what the trac bar is used for, so I looked it up. It's job is to keep the axle centered. I can imagine with more than stock lift in front, the trac bar could become off-center, and need to be adjustable.
while perusing the Ford factory shop manual, I realized something. Excessive rake (higher rear than the front) would also reduce caster. Caster as most of us know, helps with the straight-line feel. The more caster, the more the truck will tend to want to stay going straight. Too much caster, and you can barely even steer the truck on the highway. Too little, and it feels like you're driving on ice, constantly correcting.
A low-slung long forked chopper has a ton of caster. a Ricer bike with it's almost straight fork has almost none, comparitively.
as far as I can tell, caster is not adjustable on our trucks. I might be wrong. But if I am correct, then ride height, from front to rear, is important to keep track of. It's the one way it "can" be adjusted.
Too much extra height in back compared to front, will reduce caster and make the truck feel more wandering in a straight line. Even the manual talks about caster and frame angle. This might be why the folks who use 2" hangers in front, report their straight line feel is suddenly so much better. I believe it.
But, then--if you have the front and rear the same hieght, having any serious load in back results in it sagging. I voted for having some headroom for large loads in back, for now. But I am seriously contemplating having my machinist friend shave the rear 2" blocks down to 1" and keep the bump-stop arms. I'll also check Ford and see if there's a stock piece that does this job at 1" instead of 2".
I have noticed, since I did the rear B codes, and have 2-2.5" of rake, that the straight-line feel is not as nice.
It IS possible to adjust caster angle, but it is not easy. You need an alignment shop that can install a 1 or 2 degree shim between the springs and the axle mount pad. I have not done this, but maybe someone is online that has done it.
I can't advise shaving the rear block. It is cast iron/steel and is hollow. You need to keep the strength. Perhaps it would be easier to make a block from scratch(?). Also, keep in mind that 1" decrease in rear axle block height over the 137" wheelbase gives only about 0.42 degree improvement (increase) in caster angle. This is the arcsin of 1/137.
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From: San Martin
Great math, thanks!
Excellent analysis. This is one of the hazards of raising the rear height too much. I have noticed that my Ex seems more directionally stable (less wander) when I am carrying a good load on the rear springs (increasing caster).
It IS possible to adjust caster angle, but it is not easy. You need an alignment shop that can install a 1 or 2 degree shim between the springs and the axle mount pad. I have not done this, but maybe someone is online that has done it.
I can't advise shaving the rear block. It is cast iron/steel and is hollow. You need to keep the strength. Perhaps it would be easier to make a block from scratch(?). Also, keep in mind that 1" decrease in rear axle block height over the 137" wheelbase gives only about 0.42 degree improvement (increase) in caster angle. This is the arcsin of 1/137.
It IS possible to adjust caster angle, but it is not easy. You need an alignment shop that can install a 1 or 2 degree shim between the springs and the axle mount pad. I have not done this, but maybe someone is online that has done it.
I can't advise shaving the rear block. It is cast iron/steel and is hollow. You need to keep the strength. Perhaps it would be easier to make a block from scratch(?). Also, keep in mind that 1" decrease in rear axle block height over the 137" wheelbase gives only about 0.42 degree improvement (increase) in caster angle. This is the arcsin of 1/137.
I agree with you on the iron spacer with the slapper arm for the bump stop. Once I looked more at it, the casting for the slapper arm is also 2" thick at it's base. You could not shave it down, either. And the honeycomb casting would become weak as you mention.
I was thinking maybe some 3/8" or 1/2" plate, as the spacer and the slapper arm--all in one peice. It could be cut out easily with a bandsaw. If you wanted the locater hole, you could drill, and if you wanted the locater nub on the other side, you could weld a little nut or something round onto it. The nubs are the buttons on top of the leafs in this picture
ExcursionBcode - mwsmith's Photos
The locater hole/nub is not essential, since it's not what's holding the spacer in place. Friction is.
Yes, plate steel might bend. Not sure if I care.
Bear in mind, all this is to avoid removing the slapper spring leaf all together to lose some height. Removing the entire spring and reconfiguring it is not something I want to do again, in case it does not work out.
Jacking up the rear and undoing the U-bolts and sneaking the 2" spacer out and replacing it with something lower, is barely 15 minutes per side, and can easily be undone.
And I really don't want to raise the front end.
I'll start looking at changing caster angle. Thanks for the tip. I have weekend racer Longacre-brand tools for measuring camber, toe, and caster. I just have not tried it on something this big.
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