I have a 1966 GS Skylark nothing aftermarket, Trying to figure out a front end vibration at 65mph+ - Just installed New front Shocks - Bearings seem to have no play - Had the wheel/tires rebalanced not too old 2015 radials, -Steering an tie rods are old but don't have much play - Control arm bushings are old but not missing - Maybe ball joints?
Swap wheels/tires front to rear and test. Ball joints, center link and tie rods can have play that contributes to shimmy/vibration, and is not always easy to detect if you are not familiar with play. Drive and check the following. Do you feel it in the steering wheel? Does it increase or decrease on a smooth flat road if you put "tension" on the left to right of the steering wheel. (just tipping into the end of the "play" of the centered steering wheel) Does it increase or decrease if you get the steering wheel in the center "play" area. Pull left or right or "hunt"? Does the vibration go away if you start applying breaks while maintaining the speed at vibration? Does the vibration change in left or right cornering maintaining the vibration speed? But jacking up and having someone assist in holding one wheel, and/or steering wheel, can help isolate anything loose. If you can, have someone shadow you and observe each wheel/tire and see if it is obvious. I am going to hazard a guess that it is the balancing, depending on how it was done. Everything has harmonic vibration and tires are supposed to be balanced to put that in a rpm that is least likely to be felt in normal driving. A tire that has belt damage from impact, are often hard to detect, and not always apparent in balancing, as the road flex is what "changes" each time the tire rotates, and that does not occur in balancing. Rode motorcycles most of my life as "daily transportation" and learned the "feel" and after, the causes, so I can "whisper" a wheel tire problem better than I can explain it. (replaced many an aircraft tire for that reason)
All good advice & agree - My $ is on a wheel/tire issue. There are two m/l unrelated issues wrt wheel/tire vibrations: Out of balance (radial & lateral) & out of round. I say m/l because as you get the assembly rounder, the weight required to balance it will generally decrease. The other big issue (the wheel/tire industry sucks!) is having the wheel centered on the balancer the same way it's centered on the vehicle (in the case of out cars by the lug holes). By definition, if a vehicle has tapered seat lug nuts, it's a stud centered wheel. If a shop doesn't have the fixture pictured, go somewhere else! I don't even back cone them when using this type fixture as the cone & the fixture are fighting ea. other & have argued this point w/the fixture manufacturer but (big but) in order to do so the assembly must be supported when tightening down the spindle nut just as the assembly must be supported when tightening down your lug nuts. DO NOT use the taper on the lug nut to "pull" the wheel up & into place. This is why newer vehicles w/tapered seat lug nuts utilize the hub to "pre-center" the wheel - They have a big multi spindle lug wrench on the assembly line that tightens all the nuts at once so the wheel must be pre-centered. You have to look the wheel/tire as an assembly. All wheels and all tires are out of round (radial runout) - All of them (despite what Michelin says). A good dynamic balance will take care of all but the most extreme lateral (side to side) runout/balance issues as all wheels & tires also have lateral runout. As long as the wheel is fixtured properly & w/o getting too far in the weeds here, dynamic balancing is a pretty proven process. If you're doing a static balance because you don't want weights on the front, you're missing out on this as a static balance only takes care on the actual weight imbalance and not the side to side. You can generally get away with it only if the assembly runs very true and even then there could be imbalances within the tire that you cannot see. Basically, you "see" lateral runout (in my best southern accent, "it's a bent wheel"). But you feel radial runout! The best way to "see" the radial runout is to jack the car up w/the tire barely off the ground and spin it (on the car we know it's centered properly). Watch the gap between the tire & ground surface open & close. Or put a piece of tape around the circumference of the tire and put a dial indicator on it (this is how the old timers who knew what they were doing did it). It doesn't take a lot to cause a vibration and that amount varies from vehicle to vehicle & even tire to tire. Next is how do we fix that? Basically two ways (both can be utilized in conjunction): 1st is to match the runout in the wheel with runout in the tire. The wheel is solid but the tire is deformable and will conform to the shape of the wheel. In other words, the runout in the wheel will cancel out the runout in the tire. Even in an extreme case, an out of round tire and an out of round wheel in the hands of someone who k ows what they're doing, will ride perfectly smoothly. That's what the OE's do (some also sort wheels/tires by runout - mounting the worst tires on the worst wheels - I do this as well) and why every new car has a little sticker/dot on the wheel & a corresponding one on the tire (representing the average 1st harmonic low spot in the rim & 1st harmonic high spot in the center of the tire tread). It's also why new cars always ride smoothly but replacement tires rarely ride as nicely despite being "balanced." The 2nd way (preferably after the matching) is to true the tire or remove rubber to make the tire round (er). The OE's do this as well (both tire manufacturers & auto manufacturers) in extreme cases. If anyone wants their car (or truck, which are particularly susceptible) to ride like new (or probably better than new wrt our old cars) bring your stuff to me.... It's not even my main business but I've had ppl travel hundreds of miles to have me fix their vibration problems (I'm usually about the 4th or 5th one to try & have never had one I couldn't that's wheel/tire caused) and even had tire shops from around the country ship me their worst problems. Plus I won't scratch your wheels.
There are some pretty fancy wheel balaners made today. They can check the run0out of the wheel & the tire assembly seperately & where to mount the tires in relationship of the wheel. They ALSO offer Road Force balancing which puts pressure on the tire while in the balance mode. Tom T.
Dano, where are you located? Fixing vibrations on the east or west coast will not help me much. On the other hand I ordered new 15x7" rally wheels so I really don't want to spend time and money fixing the 60 year old 14" wheels.
Also, most wheel balancers have round off in their results which can be set. Quicky shops will use larger round off so when it shows "balanced" it is +/- 1/2 ounce! Ask them to set the machine to no round off.
For future consideration, sometimes, the +/- is not correct enough. U may need to find a balancer that cam measure to the quarter ounce.
I remember 40+ years ago when my Dad's shop first got the fancy new Hunter balancer. The factory tech showed us how to use it and it only balanced to the ounce level by default. He then showed us the "Easter egg" way to balance a troublesome customer's tires. The secret was to leave the safety cover up and press the balance button. This would then reveal where to place 10ths of an ounce to balance a wheel. Needless to say, I balanced my own tires to the point I was putting barely more than lead weight clips on the fronts and backs as indicated by the machine. My first car, a 71 GS 350 was smooth at 100MPH like nobodies business.
