Finding caster angle with an angle-finder...

[dremu]

okay, we presume that my steering arms on the 10b with crossover are, in fact, level to the axle, and hopefully perpendicular to the axis of turning, i.e. caster.

What *else* do I measure against? Level? How do I determine if my truck is level, i.e. my driveway has a slight incline to it?

-- A

 

[thedrip]

What you're really interested in is caster as it exists while you're driving, so you really need to park the truck on level ground. If the frames not level, it doesn't matter, its not level when you drive. Having a truck that sits way ass high gives you less caster, and having a truck that's all cali style ass draggin pre runner gives you more caster.

Simply.. Caster should be measured in relation to the ground if you want a true measurement of what it's like when you drive.

 

[dremu]

What you're really interested in is caster as it exists while you're driving, so you really need to park the truck on level ground. If the frames not level, it doesn't matter, its not level when you drive. Having a truck that sits way ass high gives you less caster, and having a truck that's all cali style ass draggin pre runner gives you more caster.

Simply.. Caster should be measured in relation to the ground if you want a true measurement of what it's like when you drive.

Well, crap. That makes sense I was figgering to measure the caster axis angle against the axle somehow. Leave to an engineer-wannabe to find the hard way

Thanks!

-- A

 

[DEMON44]

Castor is actually the relationship of the axis of your kingpins OR balljoints in relation to true vertical. Thats where you get positive castor negative castor or zero castor (perfectly vertical kingpins)

 

[dremu]

Well, that was easier than I thought. Mind you, it's a bit vague as I don't want to take the tierod and draglink off (something about air tools at 11PM irks the neighbours )

So, *assuming* that the steering arms' top surface is perpendicular to the axis of the balljoints... and even accounting for my driveway being slightly off level, looks like I have 10+ degrees of caster. And I wonder why the steering is oversensitive!

So I'll see about shims.

Anyway, thanks all!

-- A

 

[Greg72]

10 degrees which way...... positive or negative?

 

[dremu]

10 degrees which way...... positive or negative?

Ack!

I've been re-reading your nice post with the pix...

http://coloradok5.com/forums/showpost.php?p=1730313&postcount=19

Negative. The pointer of the angle finder is off the vertical, towards the front of the truck, which means the pinion end is up too high, right?

I guess those front spring hangers I made may have been a bit excessive. Seems like a lot of angle to fix by shim; hate to cut and re-weld the perches (work!)... maybe I'll try switching back to the original spring hangers (i.e. move the pinion down again), see if things improve.

-- A

 

[DEMON44]

So, your top kingpin is over center towards the front of the truck by 10 degrees????

That would be negative 10 castor, thats a long ways out.

Are you certain your reading is correct? Just have to make sure.

 

[thedrip]

If the pinion is moved up as much as you say, and you really do have 10 degrees negative caster.... the truck should be almost undriveable at speed.

 

[dremu]

As it's a 10-bolt, no kingpins, but yeah, the angle finder is pointing forward.

And yeah, it's iffy at speed. Really iffy. Which is why I'm doing this.

-- A

 

[dremu]

Hold The Presses!

Just had an epiphany in the shower -- no, that doesn't mean I need to clean anything up -- and the caster is in fact POSITIVE. The pointer on the angle finder is the vertical, and the 0* mark on the finder is to the rear of the truck, i.e. indicating that the line through the balljoints is also going to the back of the truck at the top, i.e. positive caster.

Whew.

Still too much, and I gotta drop it a bit, but that's doable with shims.

-- A

 

[thedrip]

What crossover arm do you have? I remember mine having quite a taper to it front to back.

 

[dremu]

What crossover arm do you have? I remember mine having quite a taper to it front to back.

Well, crap. I switched from a single crossover arm to two highsteer/crossover arms when I got outsmarted by the whole tie rod thing, so I'm getting confused in my memory. Pix of them both look like they have various side-to-side tapers, but no front-to-back ... I'll go look at the truck and verify.

Good point!

-- A