Technical Violent front end shaking

I've found that it's a 1 degree to 1 degree change in caster to frame change. Lift the frame up 3 degrees, loose 3 degrees on your castor. YDMV

 

I couldn't find my protractor so not sure of the degrees, hope this can be converted. I placed my rafter square on the floor and against the front of the axle near the perch bolt boss and measured the difference. We tend to work in millimetres etc here, 5 mm is very close to 3/16 and 40 mm is very close to 1-7/16. JW

 

Ya got a smart or I phone? Download a compass app they have angle finders built right into the App. You just lay your phone up against the axle and read the screen. Nice.

 

7.133 degree's and for the record done without any smartphone thingy...
5mm = .197 40mm = 1.574 divide mm by 25.4 to convert.

 

My gosh . . . we're doing some basic geometry here today . . . we have MAD skills on the HAMB! LOL

Good work guys . . .

 

I get the same figure, roughly, but the conversion factor is immaterial as long as both measurements are in the same units. Likewise it's probably much of a muchness whether you use the arcsine or arctangent; it'll approximate much the same.

 

I started this post and what I really need is a professional somewhere in a reasonable distance of Johnstown Pa. Anybody out there?

 

I had another set of eyes on the car and Jack noticed the spring perch on the pass side is angled while the other one is straight. I assume these are what you use to set the angle on the axle. I don't think a picture will show this.

 

Did you replace the leaking shocks?

 

A close up pic of each spring perch maybe helpful. JW

 

Was just thinking of the effect of too much caster and how it will affect the scrub point as the centre line of the king pin will travel further out before reaching the ground. I don't think many understand just how important it is to have Camber, Caster and Kingpin Inclination all dialled in to make it all work together. JW

 

Ditto

 

I took this shot of a T Bucket front end at a show a couple years back as I just couldn't believe what I was looking at! There are so many things wrong and just because you can doesn't mean its correct.
I think from memory the centre of the tire where the scrub point should be a and the centre line of the kingpin is about 6 inches off the mark and with cross steer that will make things worse.
Also of note is that the wheel/tire is so far out it swings in an arc and on full lock it will stretch that brake hose and not to mention how much load is on the small outer wheel bearing and the tip of the stub axle.
Each tire has so much leverage over the steering control system that hitting apot hole etc would want to rip the wheel out of you hands.
I bet its heavy on corners as you would be pushing the outer (with the most load of the two) wheel/tire forward but the drag would be tying its hardest to go rearward. JW

 

As good photos are needed to work through the problem on the OP's ride we will just go round in circles discussing the rights and wrongs of front end geometry and componentry.
To the OP, please post clear shots of your front end taken from at least at a height of the front wheel centre line. JW

 

"Death wobble " is a combination of caster , worn parts, and roads

Bored and stroked touched on it talking about the dragsters

More caster makes the wheels want to point straight , which is great for 90 mph on the freeway , but at slow speeds when you hit a pot hole , or train track the tire that hit it wants to turn slightly, the caster corrects this bringing the wheel straight again, but what happens with worn parts or weak tie rod is a domino effect the wheel over corrects or starts moving the other wheel and they start a push pull argument and basically start slapping each other and taking up all the gaps in the worn areas of the system , that's why the vw dampner " fixes" the problem it covers up some of the voids from parts wearing or the steering box not being centered on the worm which is why most times DW happens while you are in a turn

I know Titus on here had a problem show up after getting a few thousand miles on his coupe he had 7-8* caster and dialed it back to about 4.5-5 * and didnt change anything else ... Problem went away

Don't take it as gospel but its the best I have come up with and Titus experiment is a bit of proof in the pudding

In the past I have used the vw steering stabilizer begrudgingly and went on my Marry way

I do think that steering arm is a bit long and possible providing quite a bit of extra leverage as the front tires want to " kick back all the harmonics" back into the steering box

 

The longer the steering arm is the less leverage it has on the steering box.
My RPU has a very worn F-1 steering box and the car only has a tendency to follow the curvature of the road surface. I even took it over railroad tracks today ...not a twitch, I even have deep dropped steering arms and what I do also have is a good amount of caster, correct camber and kingpin inclination producing a good tire scrub point topped off with correct toe in and good rod ends, even my spring shackles are at the correct angle and to top it all off I DONT have a damn DAMPENER. After over a 1000 miles of testing this car the front tires still have little Hedgehog ticklers on them. Im an ex Mechanic so I have a bit of knowledge on steering, I have no experience on the use of a Crystal Ball.
There is so much information on steering geometry out there, more people should learn it before they start slapping parts together and then oh crap....lets just fit a VW Dampener and call it FIXED. JW

 

Replace "leverage" with the word "movement" mistake in words my bad

Perfect geometry would also mandate the draglink and wishbone should travel in the same arc