PROBLEM: Crazy front end shake that won't give up. At certain speeds the front right only will begin to shake and bounce add on 5 MPH and then gone. It has broken off my shock mount. The car drives relatively straight. Pulls right depending on road crown. SET UP: I have a '30 model a Flathead, '39 tranny, model A rear, etc. The front end is a Possies "in da dirt" kit on split bones. The frame is essentially stock with some critical plates for motor and front end. Juice brake, stock A steering box (fairly tight- 1-3 degrees play). Pete and Jakes shocks. I have good steering geometry with no bump steer. A little shake in the wheel while braking, proly hot spots in drums. Pulls slightly right when braking hard, brake adjustment out. WHAT HAVE I DONE SO FAR: I have rotated/balanced the Bias tires. still there I have check the tires for roundness. still there I have checked and changed shocks. still there I have balanced the drums. still there Checked caster/camber. OK. still there Replaced all rod ends. still there Checked for frozen king pins. still there Greased the sh## out of it. still there Installed a dampner shock to drag link. still there Diss-assembled and rebuilt front spring. still there Removed spring and flipped around. still there Bought four new radials on steelies. slightly better Could my frame be flexing? I checked the caster at the bones, could my axle be twisted? HELP I am running out of solutions for this. Any comments or suggestion will be welcome. I am going to check to see if the axle is twisted this weekend. I am planning the 600 mile trip to Hunnert, just trying to make it a more plaesurable/safer ride there and back. Jim
A buddy and me were checking out your post and he suggest that you check the run out on your spindles. possibly bent.
Bent rim? Check the wheels while on the car. Your hub may be off center, causing it to run like a clown car. Bad wheel bearings? Good luck,I hope these may be of some help.
Pressure is a good one and also check axle inclanation. You said you checked your king pins ,but with that side jacked up do you have play in any direction?
Have you taken it to an alignment shop with good equipment and people who know how to use it ? I would. On my bent axle I had it aligned by a fellow who I thought knew straight axles and he and his pop have been in the business for 40 years. He MISSED it. I later had it aligned again at another place by a fellow with a hunter alignment machine and he missed it! But he did tell me he could not straighten out the caster but didnt know why. I started looking and found that the left spindle was bent 5 degrees back from the other one. A new axle and Im running fine. Here's a pic of what they missed.
Measure the length of each one of the wishbones...my buddy had the same issue and he had one of the bones that needed to be adjusted. one was longer then the other, simple fix of turning in or turning out the tie rod end
Thunder has a point. If one wheel is toe'd in an the other is straight, it might be doing the shopping cart boogie. I would also go one step further than Famous suggested. It's not just a matter of having the bones at equal length, but also having BOTH axles square to the chassis. If the rear is off slightly, the thrust angle will have the car dog tracking slightly crooked down the road. This means the front is out of square with the travel even if it is square with the chassis. Hope that helps. Good luck.
by shake and bounce, could you be referring to the good ol "shake of death"? Does this happen only at low speeds and then go away when you accelerate? Is it a bouce or side to side shake? assuming this is the problem here are a few things to try (i had a similar problem): 1. Tire pressure. Try dropping all tires to 20 just to start, see how this affects the problem. 2. Double check toe, make sure the car is on the ground, roll the car foward making sure your wheels are pefectly centered. You should see 1/8 to 1/4. recheck several times. 3. Check for play in any links. especially the tierod. also check play in steering box 4. Check the preload of your wheel bearings. if you are in between gaps in the castle nut you may need to put in a shim washer to find the sweet spot. You want to be able to slide your cotter in just as spindle nut is at perfect tightness (tighten down lightly with a wrench, back off, and then retighten by hand or chocked up close on the wrench). The shim washers helped my problem greatly. 5. Drag link, tie rod diameter. hopefully you didn't use 1/2 heims on 3/4" tubing. This size link will flex too much on anything bigger than a t bucket. Hopefully you went 5/8 heim or ford rod end on 7/8" tubing.
I have an idiot confession !! (keep it a secret though) On our way up to this years aasphalt invitational, the rpu was havin some shakes and tracking problems. we were up at Pat's that night, lookin over the car before the return drive, and noticed serious tie rod rub on the radius rods. Well I had been caught up tryin to get the 40 running, so the rpu was always just a sollid driver with small issues, so didn't really look at it too closely for a while. Anyway, we're looking at the front end, and the tie rod is bent like almost 2 inches, kinda like a Jack had been set on the tie rod instead of the axle/frame! (one of the problems working at night across street from cirkle K) doh! the alignment was off so the wheels were splayed out about 1/4"+ (they are sposed to point inwards a tiny bit) so we straightened it out, actually Pat straightened it out with his work truck (thanks!) and after 20 miles or so, the tires warmed up to their correct position, and we were fighting as to who got to drive it the 350 miles back (2 cars 3 drivers) so... the moral of the story, ALIGNMENT - TP
yep what these guys have been saying, my hotrod used to get the shakes, I found the best tyre pressure was 18psi in the radials, enough to keep them on the rims as well as not cause sidewall damage/wear. spring shackle length and angle may be a factor, although you say you are running a Posies set up which should be right from the start....
Check the balance and run out on the rear tires. On those old frames, a rear wheel being out of round or out of balance or a bent rear axle will act like a front end shake.
Well thanks for all the advise. I have double checked the caster angle both sides reading around 5 degrees, Toe in about 1/4 inch. Measured bone lengths within 1/16 in. Measured left rear to front right and right rear to left front, within an 1/8 inch. Switched hubs, drums, and rod ends from side to side, no change. Checked drums and hubs for roundness and true, all OK. Checked the drag link and cross link all are fairly parallel to the bones and road. The cross (spindle to spindle) link has a slight bow in it for crank pulley clearences??? Maybe the cause. Ran out of time this weekend to play with air pressures. As for rims and tire all check out, on the Bias tires (Deluxe 7.00x16) all are same size and made many rotations and positions never made a difference. When running Bias @ 25-26 PSI (cold) the front right would begin to bounce and shake around 45 MPH and disapear at 49 ish MPH and and return around 60 MPH. When the radials are on @ 29-31 PSI the front right would begin the same dance at 50MPH and stop around 54MPH and return around 64MPH. But the shake is much less severe (hardly noticable) with the radials. But when the Bias are mounted, I am waitng for the radiator jump out of the shell. This week I am going to check the axle for straightness and play with tire pressures. Have any other ideas thoughts or comments? I have an appointment with a very reputable front end shop late thursday, hoping that I can find issue and cancel. If I have to take to shop there goes my travel money to come to HUNNERT!!! Any Ideas at all? Thanks in advance, Jim
i used to have that problem if i hit a bad spot in the road. found a fix on fordbarn.com. switched front tires from one side to the other, cured problem. got rid of crappy tires. i normally run mine at 30lbs. (radials)
"cross (spindle to spindle) link has a slight bow in it for crank pulley clearences??? Maybe the cause." That could definitely be it. When you put a bend in a link it is no longer in pure compression or tension. You are actually transmitting a bending moment through the link!! Remove this link and put in a straight one before you troubleshoot any further. This would also explain why your problem is mainly from the right front. Your driverside wheel is more or less being held steady by the draglink, you passenger side is shaking while the tie rod flexes! If you need clearance for the crank pulley I suggest the following: 1. Space your tie rod from your steering arms using a spacer between the heim and the steering arm with a longer bolt. 2. Heat and bend your steering arm downward. If either of these methods causes additional interference you may have to rethink things in the front a bit. A posible solution may be converting to front steer.
i think its crappy tires....mine are just a blur at 65-70 looks like a basketball bouncing down the road. those 'stones are made for 500 mile a year stockers at 45 mph.
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