Speed wobble

[freakdude]

I got problem with my RPU. If I get it out on the highway , the drivers front wheel gets a hop or maybe wobble to it. I got to get on the brakes and drop my speed to make it go away. I recently did the front bearings and im leaning towards a bent rim. My pickups is based on a 1990 Dodge D-50 chassis and im running 1940 Chevy car rims. Im gonna pull the wheel off and get it checked but im looking for any other possibilities as to a cause. The problem only seems to pop up on bumpy road at around 60 MPH. What do you think guys?

 

[Bonehead]

The dreaded, "High Speed Wobble" or "Death Wobble". Usually caused by an unbalanced tire, or bad tie rod, or combo of both. I would start by checking all the links from steering to the tie rods themselves. I usually jack up the front, and have someone rock the steering wheel back and forth while you inspect the connections. Allignment may also cause this, as tires alternate which one is doing most of the steering. Check everything.....twice.

 

[gassersgarage]

All of the above but also shocks. A shock broke on my 32' and the right front would bounce if I hit any irregularities in the road. When I got to the cruise spot and was cleaning my car, I discovered the shock rod had snapped.

 

[freakdude]

Yeah, shocks were my first guess. I changed them and unfortunately it did nothing to help. I think I can see a flat spot in the rim...

 

[35Mastr]

Swap the wheels left to right or front to back if you can.Then take it for the same ride.you will know right then if its the wheels.If not it sounds like you may need a steering stabalizer from SoCal.

 

[donsrods]

Strange that this thread came up now. My T from the day I finished it went straight down the road, even at 70+ on the interstate all the way to Daytona. The other day Dan and I took it to the store and a traffic light was changing so I kicked it to beat it. All of a sudden the front end went nuts, wheels shaking violently. I hit the brakes and it stopped, but it sure scared the bejesus out of me.

Just before we left the shop I wanted to check my toe in because a few days before when I took it to the beach for the photos it seemed to want to wander a little. I dialed in a little more toe in, and that was the only change I made. I borrowed a cresent wrench from the guys at the hardware store and set the toe in back to where it had been, and the ride home seemed ok, but it was white knuckle time all the way.

Don's T bucket is having a problem with the same thing. All the front end components are brand new and tight, and we have adjusted it every way possible. So what we have done is stripped the front end down to the bare axle and have ordered new spindles and Wilwood disc brakes for it. When we built it we used '69 GTO discs and we felt there might be too much rotating mass up there with those. The Wilwoods are lighter and smaller. We are going to remeasure and reset everything on his suspenstion and have all four wheels and tires rebalanced on a sophisticated machine a guy we know has. We are going right back to ground zero and making sure everything is set where it should be.

If you have never had this happen you can't imagine how violent it is. I have been doing research on it and this problem is pretty common, especially in the jacked up Jeeps with big mudders. Once it happens to you the fear of it happening again never leaves you. You have no way to know what pothole or dip will set it off again.

I am also going to check all the alignments on my T and have my front tires rebalanced again too. I don't ever want to have that happen again. I may also replace the front shocks just to be sure.

Don

 

[35Mastr]

Wow,Before you guys go nuts.Replacing everything under the sun.I would try a steering dampener.I know exactly what the death wobble is.It is very common in the Ford Super Dutys with a staright axle.It is also very common in Hot rods also.The only reason that alot of you never experinced it in the beginning is that the car never hit that right bump or had been accellerated to make it happen.I can almost bet money on this that a dampener will fix the problem.This has also been covered on another forum quite extensivley and the dampener fixed it.Conditions for Death Wobble will not be easily reproduced.Speed and road conditions will only determine when it will happen.On the push pill steering it is easily mounted to the tie rod form spindle to spindle and then to the frame or nearest point.This could be the best money you ever spent.They are not all that expensive.

 

[freakdude]

Hell mine wobbled soo badly I thought it was gonna spit out the motor! I know exactly what you mean. With mine its gotta be a bumpy road to set it off.

 

[35Mastr]

It has only happened to me maybe five or six times.But it is something that you will never forget.All of the times the car had to come to a complete stop before it would stop.Now when it happens.I know the dampener needs to be replaced.

 

[Willowbilly3]

I have seen the wobble on stock 4x4s with no loose parts and nice round, balanced tires, stabilizer always took care of it.
The worst I had was a 54 Dodge 5 window pickup with a 383 and wore out front end. It was pretty predictable at about 65-70 and you could barely keep it between the ditches.

 

[gassersgarage]

Never had a problem with the front end on my 32', however, I raised the front end 2" to clear the driveway. Then I took it to a shop that specialized in hot rod suspensions. Turns out, the front end was toed out and my tie rod was too long to adjust it correctly. Milled 1/8" off of each end. Now everything is true.

Panic stops, hard acceleration and pot holes. Nothing affects the front end and I don't use a dampener.

 

[donsrods]

Yeah, if I had a conventional I beam front end with the spring on top of the axle I would add a stabilizer, but both my Son Don and I are running suicide front ends with the tie rod out front. It would look goofy on those, I think.

I am going to start with having all of our tires rebalanced on that good machine. I had them done at Tire Kingdom, and am not sold on the job they did. My T hit every kind of rough, uneven road surface on the 5 hour trip to Daytona, and it never moved an inch. Steered like an arrow. This just developed and like I said I just added some toe in prior to that drive.

Things might be loosening up also with some miles on it, like wheel bearings, so I will recheck those too. All I know is, I DON'T WANT TO HAVE IT HAPPEN AGAIN.

Don

 

[gassersgarage]

Don, please keep us updated on the verdict. I'd like to know the problem in case I have to trouble shoot.

 

[35Mastr]

The problem is caused by Lateral movement.I would check everthing under that car.This will all be suspension related.Brakes will not cause the issue.

 

[donsrods]

The reason we are changing the brakes is because I had a conversation with Mickey at Total Performance before we put the brakes on and he said not to do it. They feel that passenger car disc brakes are too big and heavy on the front of a T and have found they create some shake at certain speeds. We went against his advice since ours were all chromed and stuff, and it looks like we should have followed his advice. His words were "you aren't going to like them."

Another thing we need to look at is shocks. Don is running friction shocks as opposed to hydraulic ones, and I am not sure they are able to dampen out any harmonics that are created. I am running hydraulic shocks, but I may need some shorter ones to get the shock into the middle of it's operating range. Right now, because of the car being so low, the shocks are pretty bottomed out.

I've been doing a lot of internet reading on this problem, and so many factors can contribute.........caster, toe in, loose components, tire wear and balance, etc. I just have to get back to ground zero and recheck everything.

I also miked the spindles and found the drivers side one was turned 5-6 thousandths too much on the outer wheel bearing area. I bought these off of Ebay, they had been already modified for later disc brakes and freshly chromed, so we assumed they were done right. I noticed some slop in the wheel bearings when I jacked the car up and shook the wheel, and the mike confirmed there was slop there. We have ordered new ones from Speedway and are scrapping the chromed ones.

Don

 

[freakdude]

Could it be in the tires? I havent had much experience with these bias plys. They seem rounded were the contact patch is. The ones if seen in magazines etc. have a flat tread. I know my fronts aren't motorcycle tires so the tread should be nice and flat right? And on that note does anyone have a suggestion as to where you can get the best deal on a pair of tires? I see Coker tire mentioned alot and have been to their website. Is anywhere else more affordable? Im running 5.50x16s and plan to drop it to a 4.50x16 to lower the nose a bit.

 

[donsrods]

We've always dealt with Coker. Good prices and great people to deal with. BTW, if you are a HAMB Alliance member you get 10 percent off. My Son Dan is a member and it has paid for the $ 50 fee a bunch of times over.

Well, I think I got my wobble problem figured out. I knew it wasn't something engineering-wise, because the car ran so straight and shakefree right from the start. When I drove to Daytona I hit some really rough patches of highway that tossed the car around a lot, and it never had any problems.

So tonight I started to go over everything. I readjusted my wheel bearings (they were loosening up a little) and I reset my toe in (it was off a quarter of an inch). Then I shook one of the front tires and had Dan look to see what was moving. Turns out everything had loosened up from driving it. The pitman arm nut was slightly loose, and all the bolts and nuts on the steering linkage and tie rod ends were loose too. I impacted the heck out of them all, and when I was done there was zero play in anything.

I even checked air pressure, and it was exactly the same as it always was, and every tire was just the same. I also found that at two nuts that secure the front wishbones to the axle were very loose. That would have allowed my axle to move around a little.

Now everything seems tight again so I hope I am back in good shape. I am going to go over the rest of the car and nut and bolt every fastner just to be sure. I probably have a couple thousand miles on it by now, so it makes sense that stuff is loosening up somewhat.

Don

 

[gassersgarage]

Sometimes the easy fix is the simple things. I was street racing my Suzuki 1100E and smoked my competition. It was a drag Kawaski 1000. He beat me out of the hole but I got him on top end. They I hit the breaks to slow down. Spectators said they never saw a speed wobble as bad as mine, they someone walked away from. I couldn't power through it and I couldn't hit the brakes. I just held on for dear life and coasted out of it.

The next day, I discovered the front tire pressure was down to 10 lbs. Filled the tire and the bike ran fine, however, after that, I quit racing my motorcycle.