I had a new set of bias ply tires put on the front of my I beam model A, and took the car on the freeway. Once I get above 60 or so, the front wheel (at least the one I can see!) starts hopping up and down, almost in a rythym. Only does it at higher speeds. I took the car back to the shop and had the Tires rebalanced with no change- Shop mentioned one of my front wheels is slightly bent- But my car never did this with the last set of tires (also bias plys). Whats next? Tire pressure? Check Shocks? Tire out of round? Thanks for your 2¢ on this... jay
I've had this happen. What is going on is tyre hysterisis (sp), or, the tyre rubber is acting like a second, undamped, spring and bouncing by itself when activated by a road bump. If you were to see your car from the front, the axle would be "walking" as you drove along. Cure?? New tyres, or adjust pressure LOWER. Higher pressure will make it worse, trust me. Give no heed to the pressure listed on the sidewall, all you need is enough pressure to keep the tyre looking like it should. Oh, and the same from side to side helps a bunch, too ;-) Cosmo
I've had the same problem on my roadster as long as I've been driving it. Four sets of bias plys, ballanced and unballanced, two axles, different amounts of caster, tube shocks, lever shocks, and no shocks....no effect. The only things that helped me was fixing a loose steering damper...which I don't really understand because it seems to be an up-down motion. And radial tires (which I wont run) got rid of it all together. I can usually get past the speed at which it shakes bad by driving about 90 or so.
One of my trucks was doing this. It was between about 60 and 75 miles per hour and drove me nuts. I fooled with tire balance, air pressure and the likes. I tried a pair of radial tires and it fixed it, but I wanted to go back to the bias plys. So as a last ditch effort I installed a set of off-road shocks (Bilstein 6100 series) and it was enough dampening to fix the problem. Wasn't cheap and my truck has fenders so you couldn't see the big yellow shocks. If it was a fenderless car I guess I could have painted them, but they would still have heim ends instead of traditional bushings...
Check to see if the tire are out of round. Put a floor jack under the axle on one side,raise the tire until it just spins. It should spin 360 degrees without touching.
One of the local Phoenix guys had this problem on the highway in his T bucket and I'm pretty sure he blamed the problem on his front spring, somehow. Maybe the heavy duty shocks would work.
What we do to correct that is to have our bias ply tires shaved. It's done on a machine the trues the tire (at the speed you want) by spinning the tire at that speed and then running a cutting tool accross the tread. It looks like you are removing a ton old tread but what it really is doing is making it round at that speed. You then need to index the tire on the rim so if you remove it, you put it back in the same location. The guys have done it for years and it sure makes a big difference.
Holy **** I'm not alone. My roadster has the same problem, it use to be very bad when I had lever shocks on it. I was able to improve the condition by running 40lbs in the front tires so that doesn't jive with the advice already given here. I may try to run it a lot lower once to see what that will do. I originally lowered it to about 20lbs but it got worse. I also added tube shocks which helped also. Mine starts the dance around 65-70 mph. I can drive out of it but that is really spinning the flathead so I usually stay just under it. My brother has the same problem with his A coupe and is trying to fix it as well. Things that we have tried include. 1. New tires. 2. Alignment 3. Checking to see if the axle is square with the frame and rear end. 4. Shocks 5. Checking to see if anything other than the tire is out of round such as the bolt pattern on the drums. 6. Varying amounts of tire pressure. 7. Caster and camber check. So let me know if anyone has any other ideas. It sounds like the problem is more common than I originally thought. My brother my try to mount up some radials to see ifn' that helps but is really not an option.
Thanks guys- This is all good advice. I have a year old set of Pete and Jakes hooded shocks on there right now. I'm going to rebalance somewhere else, and see about getting the tires "rounded". jay Killer- Jason man... Come along way from my stinkin' Lincoln (TSR #2), eh?
I deal with a lot of ride disturbance issues being in the tire business (30 yrs). A vibration from a tire that comes in at a SPECIFIC speed is an out of balance condition. An out of round tire, particularly with a bias tire, is out of round at any speed and the frequency increases with the tire rpm's. If the tire was balanced on a computer balancer, it might have the calibration off, or you are above the range that particular balancer actually balances the tire for. A sure-fire way is to find a shop that can spin the tire up on the car, with a strobe balancer. Not only can you see any run-out, but you can find the EXACT speed (rpm) that the tire starts hopping, and read the weight and the position at that rpm. If it calls for a lot of weight, rotate the tire 180 on the wheel, you might have the two heavy spots together. This will take care of the hop at that speed, but you may experience some inbalance at a lower speed, which you normally drive through very quickly. You will also be balancing all the rotating parts together; just index the wheel to the hub if you have to take it off.
hell Jay..slow down! Just because you got that jacket doesn't mean you have to drive like yer on the salt!
I had the same problem on my '54 Chevy, it ended up being a bad tire, I was running bias plys. I swapped 'em out for the radials on the '60 wagon, the problem miraculously dissappeared. I don't have a problem running radials on a custom or full fendered hot rod, but on your roadster they wouldn't look right. Maybe if there's a tire shop that can shave them concentric that would help. When I first built my '34 I had used tires up front and I terrifying wheel hop at speeds above 15 mph. It's maiden journey to my house, a mere 14 miles, was in complete white knuckle terror. New Cokers solved the problem, but I still have a bad vibration at 80 mph and above, it feels like it's in the drivetrain though.
I go along with the out of round comments. You'll probably have to hit an older tire shop to find a tire shaving machine. Along with that, any chance your front suspension is too stiff? Too strong a front spring coupled with a high tire pressure could accentuate the problem. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I know a lot of you guys love bias-plies, but there sure seem to be a lot of problems with them nowadays. Seems too, these same problems were a seldom seen event in the good ol daze. About the mid 70's is the only time I can remember having a bias tire with an out of round problem. Some judicious shopping can have your early car sitting on radials that are narrow enough to look like bias-plies. Granted, not close up, but I guess the difference is whether you want to drive the car or just look cool at the Saturday night rod run....
How about the brake drum being out of balance-did you grind off any factory balance weights to get your wheels on? Check to see if the wheel is seating correctly on the drum and that the lug nuts are really tight against the wheel-we had a bunch of incorrectly made lug nuts(Model A type)a few years ago that would not seat against the wheel. Good luck!
Lincoln? You may be thinking of the 50 Plymouth coupe if you're talking to me. Here's a pic of the 32 showing my latest little project on it. I made some billet adapters that take the small 32 hubcap. Looks better than the squary billet caps I had on it before.
Forgot to say that LuckyPabst bought the Plymouth summer before last. I understand it's up near San Francisco now. Here's a close-up of the cap and mag shown above. (Did you want pics of the 31? It hasn't changed much lately, the last bunch of projects I did on it was small, but time consuming stuff. I do have a lot of pics of it, anything in particular you'd like to see?
Since nobody else mentioned this, make sure your engine mounts are snug. I had this problem in my 30 coupe every time I reached 75 mph. Then I discovered a broken engine mount. After I fixed the mount, I had no more problems with tire bounce. I can't think of anything else I did that would have made the problem go away, but it did. Try the cheap solutions first
A long shot; I was experiencing what seemed to be "wheel hop." Tried EVERYTHING. No luck. Had it on a hoist for a safety inspection and one of the inspectors pointed out that one of the DRIVE SHAFT weights appeared to be missing. There was a bare patch on the drive shaft where a weight had been. Had the drive shaft rebalanced; problem disappeared.
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