Can a poorley dropped or slightly bent axle be the cause? Im Tired & running out of beer$$ buying parts. Help I have a shake that starts around 30mph on straight rough roads & wont stop. I Have done the usual- tires/balance, tie rod ends, king pins, bearings,sterring box, etc, no luck. ITs a AV8, reverse main leaf, 15" ford steels w 165 radials(had bias ply) & f1 brakes, old dropped 38 axle & split bones. I just checked the front end measurments. 5 deg caster(ok), 1/8" toe in(ok, radial tires), but the camber leans out(away from the car) on the pass & leans in(twards the motor) on the drivers side. I just measured the diff from the lower lip on the rim to the top lip of the rim (with a straight edge) & came up with 1/8 on the pass & 3/16 on the driver when the car is on the ground. im sure those numbers will increase when the entire height of thr tire/wheel (26.5") is taken into account. Brad
If your front tires lean out on one side at the top and lean in at the top on the other side, you have either a bent axle or a bent spindle, or both. The axle can be bent to correct camber settings at a truck frontend shop. The spindle can be checked and, if bent, replaced.
definately sounds like too much positive camber. that can screw up a hole buncha stuff. even your camber out a little better and see how that works. keep us posted!
I measured with a large square & the car on the ground. The diff was between the top of the rim lip and the bottom of the lip(15" rim). I know its lame but the axle never seemed to look staright & its the only way i could figure to measure with the cars weight on the ground. The tires were just balanced. I have no history on the car other than it was a 60 build that never was quite finished. thanks in advance
I'd start by getting the camber the same on both sides, use stock spec's then reduce toe, gradualy to as much as 1/16" out then increase caster to about 7 degrees one step at a time
Camber is more on the right to make up for "road crown"...Toe is usually in to "preload the suspension".
I can only tell you what works for me what the geometry of the steering look like? pictures might help
Its a 1929 highboy phaeton pu(custom). partial box stock frame, 327\powerglide & 63 chev rear end. F1 brakes & spindels, jeep (ross) box on top of frame.
Why don't you try putting some Coker bias ply tires on it.....maybe the roadforce dynamics of your vehicle would be offset by the tires idiosyncrasies and everthing will smooth out.
The death wobble I've experienced in our land speed racing roadster ('28 on '32 rails) came from low speeds and excessive caster. The wheels try to flop over at low speeds and surprisingly enough you can actually "drive through" the wobble. Above a certain speed the wobble goes away. I assume this has to do in part with the gyroscopic effect that develops as the wheel speed increases. The fact that your wobble happens above 30 mph and doesn't go away with higher speeds seems to point to something else besides the standard excessive caster problem. How is your steering setup? Panhard bar?
highboy phaeton pu(custom)???????????????? I think we are dealing with other issues from the original post?
According to the original Ford specs, Caster should be 4 1/2 to 9 degrees, camber should be 1/4 to 1 degree positive and toe in 1/16 to 1/8 inch for radials and 1/8 to 3/16 for bias ply. From the description you have given of your set up and symptoms, I would check the axle first and if, as you suspect, it is bent then have it straightened before you go all over the map trying to fix the problem. Do it methodically starting with the axle and work from there. Good Luck.
I agree with Beef Stew, it sounds like you have a balance/out of round problem not a wobble problem. A real "death wobble" us usually at fairly low speeds and you can either stop and try again or just go faster and the gyro affect will make it stop. My roadster will occasionally do it if I hit something with one wheel when I am going slow. Stand on the gas and it goes away. I have Coke/Firestone ribbed dirt tire fronts and when I first got my car on the road at 60 the tires would start bouncing up and down, and I had them balanced! and if you happen to put the brakes on hard they would literally start jumping of the ground! I had them shaved and the problem wen away, so maybe your fronts are not round. Rex
In a review of what information you have posted, the issue most glaring is the difference in camber split. The positive camber on one side versus the negative camber on the other side creates to different tire contact patterns as the vehicle operates. As the wheel spins the rotating effects try to find the center, since one tire contact patch varies from the other they continually fight each other, as the speed increases the shake continues. Remember that tires are air pressure sensitive also so make sure that the tires are at equal pressures when you are evaluating test runs and its also important to check the condition of the shock absorbers. Since you are aware of the difference in camber this is the first area to address before you go cranking in caster or toe adjustments.
Do you have a cross steer setup or a drag link setup? If you have a cross steer setup do you have a steering dampener on it.......If you have a drag link setup is your draglink level or do you have a severe angle from the steering box to the steering arm, you say you have a shake on straight rough roads at 30 mph. is it bumpsteer ???. Does it do it on smooth pavement??
How do you know the floor is level where you're taking a reading? You can read alignment specs pretty accurately at home with an electronic digital level. The 2' long models work well and you can do it ok with a 4' model. I used the 4' model to check out the frame table and frame when I built the 31's 32 frame. It really told the tale on level and twist as was used many times while the welding was going on. Sweetie bought a 4' digital level for Christmas for me several years back and I'm thinking of cutting it down to 2' and simply taping or bungeeing a straight piece of aluminum angle or channel to it for use on longer items. Stacking a standard 4' level on the cut-down 2' digital would be the easiest way out when you want to read a longer piece. Cut yourself a pair of matched blocks so the level can contact the wheel rim and hold the level off the tire surface while the tire is mounted. Anyway, I wouldn't use the floor as a reference for somewhat minute angles etc. If you do and measure caster, reverse the car in the same spot measure again and see what you get. Garage floors in houses are usually tipped 1* towards the door so liquids will flow out. A couple other things you could look at is a tire out of round. While you're at it, check the wheel and see if it runs true from side to side and is not out of round in the vertical plane. Both easily done with jackstand and pointer taped to it and spin the wheel by hand while it's off the ground. One last one to look at although I think 30 mph is a little low for it to start wobbling is an out of plane imbalance between inside and outside of the wheel. Something you can end up with when using a bubble balancer. Modern dynamic balancers will point to using a different wheel weight on each side of the wheel. Got a pair of known good wheel/tires you can try? That could tell you quite a bit.
Thanks for everyones input!! Looks like im in the market for a axle. any one got a straight droped 37-41, 2 1/4 in so cal? send me a PM Brad
Why dont you just straiten the axle, take it to a "real" alignment shop, preferably a truck alignment shop and have them set the chamber, they just bend the axle cold, its really not a big deal. after that is done, then start over and go down the line, caster, toe in, get the tire balanced ON THE CAR, not just balanced, then check out you shocks, if you have levers they suck most of the time, rebuilt them, or get rebuilt ones, or switch to tube shocks, soounds like they would fit the style of the car. jeff
Everyone talks about balancing tires on the vehicle, but who does that? I don't know of anyone around here. Is it a speciality shop?
Would love to find a "REAL" front end shop in so cal (no luck so far) Thats why i was moving twards the replacement part. Does anyone know of a shop/person around here? Thanks
Can't you have it straigtened? The only time I've had a bad shimmy is from running reversed wheels on the front. If it were me, I'd first check to see that the axle is in the chassis squarely. Next if you don't already have one, get a panhard bar for the front, they do help. Then have it aligned, the best setup I have found is 8 degrees of caster, zero camber and 1/8" toe in. All aftermarket axles I have seen have an excessive amount of positive camber and need to be bent (once the car is assembled) to get it back to zero.
try a truck repair shop, they usually do on the car tire balancing, we have a couple of old time tire shops around that still do it. jeff
As usual, C9 has a good idea of what to look for, and his info is clearly detailed and accurate. However, I've not see anyone ask this question: Is the wobble more noticable on one side before it 'infects' the entire front end? If so, you might start with swapping the tires from side to side and see if that changes the beginning of the vibration/wobble. You can check the tire to see if it is out of round by using a jackstand. Jack up the car where you can rotate the tire, and place the jackstand close to the tread. Then spin the tire. If your tire is nice and round, it'll stay the same distance from the stand as it rotates. If not... then the problem should be obvious. I don't know how new your tires are, but what about a possible broken belt in the tire? They can cause all sorts of wobbles, but I think you'd notice those problems below 30mph as you stated where your problem starts. Like C9 said... try another set of wheels and tires and see if the problem goes away. My bet is that it will be something on the more simple side.
I have had bad wobble on 2 different model A's. It ended up being the tie rod itself. The original type tie rod that has a split in the tube for some reason must flex. Once I put a new tie rod with jam nuts on the tie rod ends it solved it both times?? Just a thought
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