TTB anti-dive

[skrape]

I just got a TTB truck - a '97 Ranger.
One of the big reasons I bought this is because my old leaf-sprung SAS-ed Toyota had a terrible bobbing motion when braking, and that drove me nuts.
If I stick a longarm kit on this truck (or make my own longer arms) is it going to "dive" worse than stock under braking?
I sort of understand "anti-dive", but I can't figure out how to project the instant center with a TTB. With a 4-link, for example, it's easy to project the arms back to the place where they intersect (like this) http://www.off-roadweb.com/tech/0909or_front_suspension_technology_link_basics_part_2/photo_02.html but I haven't quite figured it out for TTB.
I've searched a bit and haven't found the answer yet.
Do longer radius arms have worse anti-dive on a TTB?

 

[brinker88]

Not if you keep stiff coils in it, no.

 

[4x4junkie]

I'm sure longer radius arms would have less anti-dive than the stubby stock ones would, however it's not something I've ever thought to be a problem... I've never noticed excessive brake dive on either of my trucks (one with softer Jeep coils, the other with standard TTB lift coils).

Something that WILL cause excessive diving that you'll want to watch out for though is your steering linkage angle being out of phase with your axle beams.
A drop pitman arm that's too short for example will cause a toe-out condition to occur during braking, which will in turn "suck" the suspension down artificially because the front tires are trying to pull or drive away from each other (this causes everything to happen in reverse during accelerating as well). Making sure your steering is matched well to your lift should avoid this issue (I wrote this page a few years ago just to shed some light on this subject, as it is exceedingly common).


BTW, the "instant center" on a radius arm is normally exactly at the very end of it.

 

[Gacknar]

Do longer radius arms have worse anti-dive on a TTB?

Short answer, is yes.

The long answer is far more complicated.

Keep the steering in line with the beams and you probably wont notice it. As the front drops, the tires will toe, this will jack the beams back up, creating additional anti dive to compensate for the longer arms. If the tie rods are not in line with the axle beams, as the front dives the tires will toe.... creating more dive.

 

[4x4junkie]

Short answer, is yes.

The long answer is far more complicated.

Keep the steering in line with the beams and you probably wont notice it. As the front drops, the tires will toe, this will jack the beams back up, creating additional anti dive to compensate for the longer arms. If the tie rods are not in line with the axle beams, as the front dives the tires will toe.... creating more dive.

I don't follow that at all

Purpose of keeping the steering in phase is so that the toe changes as little as possible. Any significant change in toe is going to have a negative impact on handling, not to mention is murder on your tires.

The IC will be the same location as the mounting point of your radius arms (most link setups have the IC much further back). I think you'll be fine.