crazy slow speed death wobble

ok fellas here is a new one for me. ive read many post regarding death wobble, but none at super low speed. maybe someone has an idea. i just got my 36 chevy truck to where i can putt putt around and ive got a nasty case of death wobble at about 10 mph. heres the stats. corvair box, all new heims all tight, superbell 4", spring behind, hairpins. caster is about 9*. toe is at 1/8" in. heres where i think the problem may lay. my spindles have new roller bearings insted of bushings, but they must be slightly worn because there is obvious lateral play. what do you guys think?

 

Pictures?

 

my photobucket account is being weird, here you can see a basic layout minus the draglink. it runs parallel with the centerline of the hairpin.

 

only got 3 lugnuts so throwing **** outta' balance

since you think you know what the probem is, I'd start with that.
how much play do you have in the steering box

 

Tube tires ?

 

thats an old pic, all 5 lug nuts tight. no play in box. the tires are coker tubless.

 

whats your ackerman look like?
and if you have excessive play in your spindles..that might be the first place to try and tighten things up there.

 

Slow speed wobble is most often caused by worn kingpin bushings, and worn steering box, incorrectly adjusted too. Since you say the box and all other components are either new or good your first option would then be the kingpins.
What "needle bearing" setup is that you have on early Ford spindles? Does it require non-stock kingpins too?

 

Probably not too good being that the tierod is ahead.


BTW, death wobble is low speed. If it were 45 mph or more, a lot of us would not be here



I wish you would say "I can easily adjust my caster to 4"... (I just can't tell if you have the adjustability in that pic)

Like I said in the last thread, I'd like to see someone who has lots of caster, just adjust that first to the minimum, to see how it reacts. i'm not saying that's your problem but I just wonder about excessive caster.

 

you can still achieve a good or close ackerman..even running the tie rod up front.

its doo- able..maybe not a perfect ackerman..but one that will work better then no ackerman at all.
understand im not saying this is all thats wrong here..if hes got loose spindles,and or kingpins..I'd attack that **** first.

 

With the wheels off the ground, how much play do you think you are getting at the top of the tire when you move it in and out, .020", 1/16", 1/8" ? Also, are you sure the wheel bearings are tight enough and have you had your tires balanced?

 

Put a block of wood between the frame and the inside-rear of both front tires. Have a helper rack back and forth on the steering wheel, watch the action. Do it both with weight on tires and with frame jacked up with suspension hanging free.

 

not to diss anyones help or suggestions but at..10 mph....? IMO, balance "should" mean nothing at 10?

 

yeah, its the ssbc roller bearings. i just ordered new spindles with pins, because as it turns out, the bore for the kingpin is whats wallowed out. VRF brought up ackeran, mine ****ed because i had the run the tie rod up front. on my new spindles i have to use bolt on arms. which arms can i get to clear this stupid spring behind?

 

common problem, lots of possibilities covered here

http://www.jalopyjournal.com/forum/showthread.php?t=385556&highlight=death+wobble

 

It's hard to tell by that pic angle, but it looks like the batwings and friction shock linkage is blocking any path for a rear steer tierod?

I took notice of what KL just said about the rake difference changing his tire size..and his ***umption that the caster changed just enough to go from perfect to wobble.

 

I used to do a bunch of front end alignments, and as some of the previous posts mentioned, there are a few common things to check, and in this order (most to least common):
1.) Excessive play in steering. This can be from any worn/loose component.
2.) Tire/wheel wobble. Sometimes tread separation can initiate this, or a bent rim.
3.) Excessive caster. As caster gets more positive, the wheels get harder to turn from straight. They essentially want to "snap back" anytime they are turned. If caster is too high, and there is something that starts an oscillation ( Railroad tracks, or #'s 1 and/or 2 above) the whole steering system can shake violently until you almost come to a stop. 9 degrees is pretty high for a street car. This is my first post, and I hope you find something useful in it.

 

^ good info man, thanks! good first post. thanks guys i hope i get it soon, dixie fried is in about a week. im going to pull a little caster out of her, and with the new spindles i hope im good. today was my first run and so far ive got to fix my wobble, and make my valve covers stop leaking, so much for those 30 dollar fel pro gaskets. all in all good day though.

 

I was always told to set caster at 7 deg. on solid axles, and adjust from there if needed.so far 7 worked for me.

 

With front wheels pointed straight ahead, is the steering box centered half way between lock and lock? This is the "high point" on your ball-nut and sector gear. Also, this position could be worn out - typical on high mileage steering boxes. Check it out.

 

Looking from here it seems the kingpins are vertical.

Do you have positive caster?
Positive meaning the tops of the kingpins lean to the back?

Negative caster can give weird results.


Where and how are you measuring caster?

Are you comparing it against a flat area of the frame or a level floor?

It should be compared to a level floor.

 

i hope that works.i had the same thing happen to me{everything new]i put a steering stabelizer on it and it never happened again.this has also happened to don{rebel reaper}and dave{littlman}they also put s.s.on there cars and it went away.it is very common with straight axels.when it happened to me it bent alot of stuff so check everything again.

 

This was a fix for us @ the Dragstrip..We are loading/unloading our ch***is's...my Truck never did it until it had more power bolted between the frame rails....The front end was violent at times coming out of the burnout or off the line.......but before the Truck ever hit the track I never had a problem w/ the front end, logged many miles........so when you have this problem on the street, you have an issue w/ something and a steering stabilizer I have alway's looked at them as a band aid....possibly covering up another simple issue that can be hard to figure out at times......just my thoughts, Littleman

 

Yes, I find it useful. That statement, along with what was said in the wobble thread a week ago, makes me pretty sure caster is the main issue.

In that thread, **** talked about the "caster trail", and I think that is the relationship of the imaginary line drawn through the center of the kingpin to where it contacts the road. And with lots of caster, the actual tire contact point on the road is way behind that imaginary line.

I am not good at explaining things, but apparently the length of that "trail" makes a tire want to be someplace else ...and when the right shaped bump comes along, both tires start fighting each other, trying to be someplace else. That would explain why Tudor and 777 "fixed" their wobble by beefed up tierods. In their cars, one wheel is fighting the other and then gets so strong that now the tierod flexes so much that the tires are no longer in relationship to each other.....and it snowballs.

When a wobble begins to start, or when it has almost stopped, you can actually sense that the tires are steering on their own.

I will go out on a limb and say that a small amount of wear in steering components has absolutely no bearing on what is the root cause of the wobble. Yes, it would be more prone to let a wobble start, but the real cause is not worn components.

 

i def.agree with the caster angle and caster trail, makes lots of sense. i feel like a stabilizer would be hiding a real bad problem. i used a stiff stab. on an OT jeep i had to cover up some wobble and one day running about 45 the thraded stud sheared off the body and it shook like all hell and i bout lost it. set caster and it was fixed. C9, im measuring caster with an angle finder off of the top of the kingpin boss. that is a pic from about 2 months ago, pre body work and ***embly. i actually didnt realize my caster was that much until i set it on the wheels. in the pic the caster is about 5* psitive. this may sound crazy, but after all the wobbles (about 4 times) i feel like my new pro 1 heims have some play. i think since i got new spindles, im going to go to tie rod ends like i should have before.

 

I would say since its a low-speed wobble its most likely not a death wobble. Hardly a serious injury wobble.

 

Set toe at 1/4" and try again. Front steer and big castor numbers likely need more tension than you're getting with an 1/8"

 

Thanks for the kind words F&J. An earler post had a link to an older thread, and I noticed some people had gone to 1/4" toe out, which seemed to cure the problem. Like a steering damper, it likely just masks the problem. On a RWD vehicle, normally about 1/8" tow in will result in the wheels being closer to straight when going down the road. On a FWD, usually they are set toed-out for the exact same reason. If you set up a RWD with 1/4" toe-out, it's probably closer to 1/2" out on the road. That induced outward force would definitely alter the dynamics of the ocillating system, but not really the way you want to do it!

I'm thinking that a high caster angle will work in some cases, if everything is otherwise perfect. I've only seen this "death-wobble" at lower speeds, as I'm guessing that there's an increasing gyroscopic effect as you go faster.

All the cases I've experienced were from loose/broken/worn out stuff, though. IMHO, high caster just increases the sensitivity. But, I guess when you get your new spindles and tie rod ends, you'll let us know.