Awestruck,

I think we are talking about the same thing. I was moving the lower control arm towards the front of the vehicle (creating the same net effect on caster). However, caster is set by moving the upper contol arm on the Lightning! So you are right, this will reduce the wheelbase on the higher number like you said but the difference is very small. I've been sitting there trying to see what about the geometry would make the truck pull towards the lower number???????? I think the extremely small difference in wheel base is not the reason for the pull, it's got to have something to do with the way the wheels want to pull back around to negative caster. I think the one that's closer to 0 has a little more leverage thus the pull to that side.

Also, shopping carts have negative caster, the wheels lag behind the centerline thus causing them to self center themselves. Here's what I mean.

Negative Caster (shopping cart example)

-->..+ (upper contol arm)
....+ (wheel spindle) <<---
..+ (theoretical lower control arm)

(the ... is to get the + to line up)

The <<--- indicates the force applied to the wheel (spindle) by forward motion. That's why it self centers.
The --> indicates the force applied when you apply the brakes. There is essentually nothing to supply a reactive force to the forward thrust so the vehicle will drop the front end a lot i.e. poor anti-dive charactoristics.

Positive Caster (most cars)

-->+ (upper contol arm)
......+ (spindle) <<---
........+ (lower control arm)

With positive caster the force of forward motion <<--- wants to spin the wheel around. Not exactly what you want but it helps turn in. Braking force --> now has something to work against so the front end drops less, i.e. better anti-dive charactoristics.

Caster also effects camber in a turn. Positive caster helps keep negative camber on the outside wheel thus increasing the tires grip (actually helps keep the tread flat)

Blacklite,

The numbers I got were the best all around numbers. The higher caster numbers will help ultimate handling at the expense of tire wear and on center feel. The SVE engineer I talked to said that the ultimate grip was obtained with the higher caster numbers and setting the toe out but the feel in normal driving was marginal. Using the higher caster with toe in will help, that's probably why LightningKid is happy with his setup. Also, because of the geometry of the suspension camber numbers beyond -0.5 don't improve handling much and it really wears out the insides of the tires.

As for crowned roads, most 4+ lane highways are crowned from the center divider to the shoulder. That way water runs off and doesn't collect in the median. Of course, if that's not the case then you are right, the truck will pull to the left when you are in the left lane. Typically this crown is not as severe as on 2 lane roads or the right lane of a freeway so the compensation in the settings are less noticable.

Kid,

You are right, the stock steering box is more to blame for the numbness than the suspension settings. He also said you need to lube the steering stops every time you change the oil or the front end will clunk. It's not as noticable on normal F-150's or crown vics because their tires give enough to absorb the stress. On the Lightnings the stiff tires push back harder, if the stop isn't lubed so it can slide the suspension binds. Again, a result of the steering box design.

The numbers I gave out were this SVE suspension engineer's idea of ideal numbers. There were 10 people on the team so it doesn't surprise me that 2 of them may have different opinions

Sorry for the lecture......I was bored tonight.

BTW, I'm a EE not a suspension engineer so I could be wrong about all of this


------------------
Mark Whatman
mwhatman@worldnet.att.net

• 99.5 White Lightning (stock)
• 99 Buell S3 Thunderbolt (not stock!)
• 98 F-150 Lariat (Flowmaster)
• 96 26' Velocity Offshore Race Boat (far from stock!!!)

[This message has been edited by Mark W (edited 12-10-1999).]

 

WHTLIGHTN
I think this will answer your questions about alignment.

 

Man o man, more alignment values...these were the ones I had collected earlier:

I had reposted these values earlier, here's all of them collected into one spot:

Ford Alignement spec:
L.H. Caster: 6.9, +/- 1.0 Deg.
R.H. Caster: 7.4, +/- 1.0 Deg.
L.H. Camber: -0.5, +/- 0.7 Deg.
R.H. Camber: -0.5, +/- 0.7 Deg.
L.H. Toe: -0.05, +/- 0.15
R.H. Toe: -0.05, +/- 0.15

Base F150: (tolerances same as above)
L.H. Caster: 6.2
R.H. Caster: 6.7
L.H. Camber: -0.3
R.H. Camber: -0.3
L.H. Toe: 0.03
R.H. Toe: 0.03

Lightning Owner prefered:
LH Caster 6.7
RH Caster 7.2
LH Camber -0.5
RH Camber -0.5
LH Toe -0.05 (slight toe in)
RH Toe -0.05 (same)

Lightning Owner autocross prefered specs:
LH Camber -0.7
RH Camber -0.7
LH Toe OUT 0.05
RH Toe OUT 0.05

Daniel

 

thx so much for all of the great info here folks. This is what I was looking for. I had my truck re-aligned after I put my Eibach springs in but unfortunately I wasn't able to get the cam bolts because I wasn't sure if one was to replace all four on the arms or just the front set. Now at least I know and will order them.

Thx again!

Paul G.

 

Hey guys - looks like a lot of great info. However, after having my truck lowered by Roush, my dealership said they cannot do an alignment - the beams hit the front airdam because the truck sits much lower. Right now the Bolt has a major right side tug. I'm trying to get in touch with Roush (no luck so far) to see if they have revised alignment specs after lowering. Does anyone on our board have any info on this scenario? Thanks!!

Chuck
*********************************************
Red Gen. II #0763 (with a few mods & ends)