Department Of Boost
Alpha Geek
- Joined
- May 26, 2010
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Right after you measure how much bumpsteer you have and determine that it needs correction.
FACT^^^^^^^^^^^^^^
Right after you measure how much bumpsteer you have and determine that it needs correction.
Not sure why that happened either. The OP was asking if a bump steer kit is required just because you are lowered and the answer is no.
It's a pet peeve of mine... the BULK of the issues with a Panhard (it's a guy's name) bar is in the bushings. Minimize the deflection from those bushings, and it tightens right the hell up. Stock pencil-eraser to poly is a night and day difference, and my preferred bushing material, steel (rod ends!!), is night and day again.
In the end, both a PHB and a Watts do the same job, that of lateral axle location. Yes, the Watts does it better over a wide range of motion, but if you do the math, a rod-ended PHB only allows something like .080" of lateral deflection with a nominal 1" bump...
Bold for emphasis.
With a taller ball joint, you will need the bumpsteer kit. You changed the geometry, you need to correct it.
Did you measure bumpsteer without the taller ball joints?
I figured you had a grasp on in, others reading might not see the correlation between the tall ball joints and the need for bumpsteer correction at that point, that was all.
I think we have to look at all of the forces that might be involved as you're driving the car.Time to break out Socrates...
Given: We can prove, mathematically, that the actual motion of the axle relative to the chassis is only on the order of 0.060" total on a hard slalom.
Given: Tire carcass deflection will be an order of magnitude (or more!) greater than 0.060."
Therefore, I think it's safe to assume that Panhard bar arc and poly bushing deflection are essentially "noise" within tire carcass shift, and possibly even wheel deformation at those kinds of loads.
So, if we assume that drivers CAN feel the difference between a Watts and a Panhard in a slalom, what exactly is the difference? Is it in the bushings? Nope. Is it in the actual degree of lateral location of the axle relative to the chassis? I highly doubt it. So, what else is left? I'll submit, that even if all other variables remain constant (tires, bar rate, spring rate, dampers, AS%) that there isn't a Watts kit on the planet that puts the roll center in the same spot as the stock Panhard bar location. Is it possible that roll center migration is the real "culprit" here? Let's assume a Panhard bar that is parallel to the ground at static ride-height. In a right-turn, the roll center on a PHB moves up and to the right. Slightly. On a left-turn, the roll center on a PHB moves down and to the right. Slightly. Is it possible that this migration of the roll center in an arc is what the drivers are feeling when the say the PHB makes the car darty compared to a Watts? The vertical change alone could easily account for the difference in "feel" between rights and lefts. Bud doesn't that same thing happen with the different styles of Watts (chassis vs. axle mounted)? But is there anything in that minute lateral motion of the roll center that that Watts constrains, but the PHB doesn't? Or is it perhaps the gross overall effect of a (relatively) massive relocation of the roll center that makes the Watts car feel "planted?" Hmmmm....
I think we might be paralyzing by analyzing.
I just need two sentences....I put a Watt's on the car, and then it slalomed better. I don't really care how or why it worked.
I think we might be paralyzing by analyzing.
I just need two sentences....I put a Watt's on the car, and then ran it on a track, and it was no better. I guess it isn't worth much.
There. Fixed it for you...
And that's why "why" is so important.
Tire deflection at the top is going to be a function of sidewall stiffness in the lateral direction and I think pretty heavily dependent on wheel width vs tire section. Basically, if you've got a significant amount of sidewall 'bulge' out past the wheel flanges (like you get with tires on rims near, at, or below min-recommended width), the entire tire tread is going to try to migrate laterally a whole lot more than if it's on a max-recommended width wheel.I tried to draw this all out on paper, and still can't see how tire deflection at the contact patch results in the huge swings in and out..at the top of the wheel well.....as depicted in the video. What would be interesting is to repeat the go-pro camera video.... with the camera mounted in the same position, but with a WL watts link installed /fays /steeda etc.
I tried to draw this all out on paper, and still can't see how tire deflection at the contact patch results in the huge swings in and out..at the top of the wheel well.....as depicted in the video. What would be interesting is to repeat the go-pro camera video.... with the camera mounted in the same position, but with a WL watts link installed /fays /steeda etc.
I believe the PHB video was using an adjustable BMR PHB + mating BMR phb brace. I had the same setup (which had greasable poly ends) on my 2010 for 2 yrs then switched to the WL-watts link. However, the WL-watts link was installed the same day as the Eaton tru-trac. The effects I'm seeing are a combo of the watts link + tru-trac. That makes it difficult to evaluate, since both were installed simultaneously. The net effect however, imo, is a big improvement over the adj BMR PHB + brace + oem ford traction lock differential.