Oh boy.....should be in the 3*+ range from what I remember reading.

 

So, I said negative 0.6, but that wasn’t entirely true I guess. Here is the sheet. It appears to be +0.6. I’m guessing if it is supposed to be +3ish that would make even more sense.
I know more about motorcycle suspension and specs than vehicles.

 

Does that read 2.9* total then?


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UUUGGGhhhhhhhhh.....yea....you need to be 3*+ .....

Did you install new springs??

 

It looks like you are +0.6º compared to the spec. camber that this alignment shop is using, which based on the 4.7º & 2.3º limits on their scale, is set at 3.5º. So, your caster is 4.1º, according to this shop's report.

 

Ok....I think I am learning something here
Limits of 4.7 and 2.3 means the "middle" or "ideal" would be 3.5? (4.7 + 2.3) / 2 = 3.5?
If that is the case, to me, it looks like actual caster is 2.9° (bottom end of scale [2.3]+ positive caster [0.6]) = 2.9°
Or am I thinking too hard? Bottom line, I am trying to see if the Carli 2.5° bushings will be the key to getting caster in the proper range and making the steering less twitchy.

edit- @Roccafellas got in while I was typing. That's what I thought too, since the little arrow is above the bottom end of the scale.

 

Max 2.3* Negative Caster or Max 4.7* Positive Caster from the center axis of 0* Caster.

The - and + have nothing to do with the numbers. It's related to the vertical axis.

 

I see the report reading 0.6* of negative caster, you need to be 3* Positive caster or better.

Adding a 2.5* adjustment will get you to 2.1* Positive Caster.

I could be wrong as well, but something tells me we all will soon have a much better understanding....LOL

 

I see the report reading 0.6* of negative caster, you need to be 3* Positive caster or better.

Adding a 2.5* adjustment will get you to 2.1* Positive Caster.

I could be wrong as well, but something tells me we all will soon have a much better understanding....LOL

“Negative caster angle isn’t a setting used by modern road cars. The self-aligning torque and straight-line stability that is characteristic of positive caster are absent in a negative caster setting. In fact, a “loose” steering wheel and immense front wheel instability would result from a negative caster setup”

So that reading is from slightly positive to more positive. Because negative is impossible

So the reading is 2.9* which is 3.5-0.6 3.5* is the 0 axis as you call it which is the middle where it would be green.. the 0.6 is not negative otherwise it would have a - sign in front of it
Just like camber can actually be - or + but they do not show a + only a - if it is negative..

So this caster reading is set by their machine to read from slightly positive to more positive as negative is NOT used on these cars and is really impossible to have the wheel sitting behind the strut/coil. Whatever assembly the vehicle has..

so I believe the middle is 3.5* which is perfect caster in that measurement reading he is 0.6 to the right so take 0.6 from 3.5 and you are left with 2.9.. so i believe he has 2.9* of positive caster and 3.5* of positive caster is perfect. Which makes sense to what you are saying 3 or higher. But it’s not a negative 0.6 reading. It’s just 0.6 minus 3.5 the centreline.


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Caster

 

Reading that caster write up now.

 

Cool UK woman explaining it...

 

Okay...Caster needs to be within 2.3* to 4.7*, you are at 0.6*. Adding a 2.5* bushing should get you where you want to be.

My bad.

 

Red shading is "out of spec". So the "green" range is 2.3* to 4.7* for the shading to be green. Most SD owners want to see green AND a value of 3*+ caster.

So creep into the reading at 2.4* it would be green....just not optimal for the SD front end.

 

Actually, you need to be careful about what is removed and what is added. If your current bushing is 2*, and you swap it out for a 2.5* bushing you added .5*......

I'd go back to the alignment guys and ask for them to measure caster using 0* caster bushing. That would give you the true reading and what bushing to use to be within spec.

 

I think I’m actually going to go to my local dealer. They have a shop dedicated to the Super Duty and up Ford trucks. They have been really good to me so far with other odds and ends. Obviously, I will tell them what’s up first and make sure they either have or can get different bushings. They will also know what the truck came with in the beginning. Provided it has not been changed. But I got it at 28k so doubtful it has been messed with.

 

Ok.... got some good info from my neighbors dad who is a shop foreman down south. I’ll have to draw some things and post some photos in a sec.

 

My head hurts after reading this. I’m just going to sit here with my factory Michelin’s and hope PB Blaster saves my EGR pipe bolts.

 

Ok, So this is how he explained it....
The bar chart is misleading. They make it look like 2.3 is at the far left and 4.7 is at the far right. That is not the case. While those are the minimum and maximum per manufacturer spec, they really should be at the left and right of the “valley”. Not the bar. Also, the actual measurement ( in my case 0.6) is placed in the middle of the chart and really shouldn’t be. That is misleading as well.
He also said that you lose about a degree per inch of lift with radius arms. I was probably around 2.6 to 3 degrees before the level kit. After the kit, rolling the axle forward as it was moved away from the frame caused an effective loss of caster. The Carli shims will do the trick by adding 2* and giving me a net 2.6* caster. But.... he said that if I could find 3* it would be better. Or, go with 4* and have a shop set it up at 3*. I could eyeball it but that is not as easy as dropping the shim in at the max adjustment.

 

Exactly


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Follow up.... my head hurts. Lol.
So I got the truck back from the dealer. I have to say that the steering is 100% better. Tighter, not as twitchy feeling and does not wander when you hit grooves in the asphalt.
What hurts my noggin is the data sheet. Unless the other shop was jerking around while setting it up (possible), the measurements did not change by much. At least not to these novice eyes.

 

The middle line is 0 on every spec. Each increment to the left or right of that line you, are adding or subtracting from the number.

the 0 is the midpoint, calculating the midpoint is adding both numbers together and dividing it by 2 so the first sheet,

Is 4.7 + 2.3 = 7* divided by 2 is 3.5
3.5 is the centre which would read 0.

So if the black line in the first camber spec sheet was directly in the middle it would read 0 but the actual measurement would be 3.5* total. Make sense?

Like the first one is 0.6 to the LEFT of 2.3 so add that and it’s 2.9* see how it’s to the RIGHT of the centreline which is 3.5...

Keep moving it to the left and it would of read 0 but actually been 3.5

The second one is a lot easier, it automatically find the centreline and just adjusts it - or + to what it needs. You are looking at -5* total of negative camber, but it’s impossible to have negative camber.. or else the wheel would be behind the centreline (vertically) of the coil spring. It just took it to -5 of what the actual spec put in the computer reads of what the actual spec the wheel is.

Actual camber is 1.5*

 

So my true caster was 2.9* and is now 2.5??

 

Why does the top of the form read "Modified Specification"?

Didn't the other report someone posted show a different spec range for Caster???

 

Yea..the first sheet.......4.7*-2.3* is the accepted range that a measurement needs to be found to be Green "in range, in spec".

Your first round was 0.6* which threw the RED shade which is "out of range, out of spec".

Now the "range' is +3.0*- (-1.0*).....WTF.....

 

Modified because the vehicle is modified, which the first shop didn’t account for.


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LOL.....jeez....So he's still sitting at +0.5* Caster then.........Cause a range of +3.0*- (-1.0*) would have a middle of +1*...to which he is -0.5* off "middle" of that which is +0.5* Caster......

At least that's what I've picked up thru all this.....I think....LOL

 

I've learned way to much at this point and to STILL be confused is hard for me to grasp.....IF I'm confused!?!!????? LOL

 

Cool chick voice....

 

Not to mention IF the Caster specs listed on the "Modified Specifications" are true then HOW can there be a reading of less than 0* Caster??????????

Cause:

Because negative is impossible

Negative caster angle isn’t a setting used by modern road cars. The self-aligning torque and straight-line stability that is characteristic of positive caster are absent in a negative caster setting. In fact, a “loose” steering wheel and immense front wheel instability would result from a negative caster setup”