High Speed Front Wheel Hop

I have a 1927 T. At about 70 mph I get a violent front wheel hop. Just like you would if you had an out of balance tire, but I don’t because I have tried 4 sets of new front rims and tires. I lived with it last year and usually drive past the hop; the only problem is most freeway traffic drives at “hop speed”. So I went down the list, I had my front drums balanced, new wheel bearings, new king pins, I went so far as to replace my vintage drop axle with a superbell and a new spring, Nothing. it still hops. I am running Armstrong lever shocks, and at one point I welded on shock mounts and had tube shocks and lever shocks. That’s 4 front shocks. My chassis is very stiff, originally built for a heated rocket motor, the motor in there now it a very light 2tc. I know, because I picked it up once, and I’m not that strong. Could my chassis be to light? Could toe in be a problem? I run a little over 3/16. Any Ideas would be greatly appreciated. here is a pic. so you can see the set up. spring behind with armstrong shock.

 

I would start checking the other things , rear wheels and tailshaft maybe it is bein transfered through the chassis and showing up at the front due to this having the most travel ? just a thought .

 

3/16" is too much Toe In.

Any oil in the Armstrong shocks ?

 

Yep cut the toe down to 1/16 and see how it goes.

 

What kind of brake set up are you running? In the good old days of large heavy drums we used to "spin" balance the whole assembly on the car to solve the kind of problem you speak of.

 

The armstongs have oil, there in great shape. playing with toe, is next on the list 1/8 then 1/16.

 

the brakes are F-1

 

I had the same problem, my lakes modified only weighs 1500 lb. It hopped from 60 to 70 and was so bad that my son said that he didn't feel safe. I tightened everything and played with shock tension ( friction shocks ). The hop went away after I took the wheels to a different shop to have them balanced.

 

I would suspect a drum has spit off its weight, or during the turning process has got a heavy spot. If you can't find a spin balancer you can check it out pretty close by taking off your hub and clean the grease out of the bearings loosen or remove the brake shoes and then use the hub to check the static balance. If one side drops to the bottom mark the spot and remove a little weight till it doesn't fall to the bottom anymore.

 

Tough to tell from the pics but, are you running a front panhard bar?

Flatman

 

Also check the front wheel bearing preload . The lighter the car is the more important this is.

 

I actually had the drums balanced to zero by a machine shop last month, on there crank balancer, they didnt use weights they drilled them, there is an old shop local that could balance the wheels on the car. I dont have a panhard, and dont realy want one. but I thought about that too.

 

3/16 toe in may be too much. Some T's even run a little toe out. These little cars can be very sensitive to front tire pressure. Try lowering tire pressures. Tire and/or wheel balance could also be the culprit but it you are driving thru it at 75 or 80 I doubt that it is balance. I do not think balance would go away that quick if at all.

I had violent wheel hop that started about 25 or30 when I first drove my car up the driveway and it was grossly out of alignment. I am only running 1/16 tow in.

I am also currently running a steering damper and all my problems went away.

Good luck and keep us posted

 

bias -ply tires ? let me guess they diddn't tale you when you ordered them , they had to be trued . I just got a whole new set in last week , bet they do the same thing ! Just like the last set I ordered ! no truing machines in Corsicana Tx ! You would think that if we could put a man on the moon , we could buy decent bias-ply tires that were round ! Michael L. Weaver 3070Fm 3243 Corsicana TX 75109-3669

 

off the subject, I know... but I love the hood! Is it polished aluminum?

AB

 

Bias tires are really picky about pressure. I had a front bounce and lowering the pressure on the front to 20# fixed it.

Also noticed a little bounce in the rear the other day, 80 degrees out, found my rear tires had gained about six pounds from the warm weather. Bled of down to 22# and it was fine.

 

what kind of car ?

 

I had a violent wheel hop at about 60. I removed 2 leafs from the front spring and it really helped. Im going to lower the tire pressure a bit also

 

I had the same problem on mine when I ran friction shocks. I tried tire pressure with no results. dumped the frictions and used F-1 shock mounts and hydralic shocks not gas filled. Problem cured. My car weighs 1500 lbs without my fat ass.

 

At 70mph plus a vibration caused by the spinning dynamics of the tire and the hub are a critical point. Since you have covered the tire balance question by swapping wheels and tires and encountered the same problem, the suggestion by Coupster of checking the drum/hub balance should be done. If you have swapped drums or redrilled drums to fit other hubs the spinning balance of the drums comes into play, if they are missing a balance weight or have been assembled off center or turned off center they will produce an out of true balance condition that escalates as the rotational speed increases. Most tire balance problems show up at lower speeds, since this is at a higher speed you should look further to the hub/drum area and follow the suggestion to check first the static balance of the hub drum assembly and then have the wheels checked on the vehicle with a spin balancer. The problem is to find a tire store/ repair shop that has a vehicle mount spin balancer.

The next scenario is to check the shock absorbers, with a leaf spring you should have a stiffer rebound on the shock than on compression. In other words the shock should go up easy but extend harder and there should be a good deal of stiffness to the shocks operation and require some effort for you to pull it apart or push it together. . If it is to soft with little or no dampening power you will get the same feel as an out of balance tire at high speed from the road bumps.

Since you are not having any tracking issues, toe in or out should not come into play however 3/16 is a little too much, it just scrubs off rubber. You should just recheck the caster on each side to make sure that it does not exceed 7* and you should make sure that your tire pressure is equal and not set too low.

 

I want to mention something here that I've recently tried and seem to be on the right track with.
Last week Fidgeter had a wobble problem we were all discusing and one of the items to look at was frozen spring shackles.
I didn't see how this would relate, but I've been also getting my wobble a little better, so I tried soaking my shackle rubber bushings with WD-40. This has made a major improvement in the ride (less harsh) no more noise from the springs clicking and snapping, and has so far eliminated the tendency to wobble.

So it seems that friction in the shackle bushings is no good.

Maybe the answer is to go to the origonal style of pins and metal bushings that are greasable.

Sorry to semi-hijack this thread, but I think these front end issues are all connected.

Frank

And I also had a high speed hop on the front which was solved by replacing the front shocks. The old ones seemed OK and not much different from the new ones. These are short hydraulics. The new ones from Speedway are very slightly stiffer. Enough to cure the issue.
I run 20 PSI on 5.00x16 dirt trackers on wires. now at 1/16 toe in.

 

I would first try 1/16 toe OUT. But I would guess you might want to add a damper...cheap and they solved my problem on my old track roadster....

 

'27 T Touring 16" wires, 5.50s on front, 7.00 rears. 348 Chevy, 40 front end set up suicide, cowl steering.

 

I had the same problem when I installed ribbed front tires on my RPU. I jacked the front wheels off the ground and spun them and eyballed the top of the tire from the side. Sure enough there was a high spot on each tire indicating they needed to be trued. Well no one around here trues tires anymore so I took my time and rigged up something to mark the high spot with a ball point pen and don't tell anybody but I removed it myself with a 36 grit sanding pad and the problem was cured, been fine ever since. I don't think I could have done it with regular tread but I think you should start by making sure your tire are perfectly round. They should be driven a few miles and warmed up before you jack the car up and check them.

 

Some good info. My T modified does the same thing around 60. About shit my self the first time it happened. A buddy told me to use a torque wrench when tightening friction shocks so both side are the same.

 

I have a 24T Roadster
Same issue
I could only go 2200 RPM in hi gear
I was in Southern Cal
Long Beach and found a guy that could true the tires and spin balance the rotating assembly
Wasn't cheep $50 tire
But BEST money I spent in years
I left the shop and headed down PCH found long straight wound up to 3400 RPM in hi
Smooth as glass
Good luck
Ray

 

I have a 24T Roadster
Same issue
I could only go 2200 RPM in hi gear
I was in Southern Cal
Long Beach and found a guy that could true the tires and spin balance the rotating assembly
Wasn't cheep $50 tire
But BEST money I spent in years
I left the shop and headed down PCH found long straight wound up to 3400 RPM in hi
Smooth as glass
Good luck
Ray

 

I know it has been a long time since you posted this, however, do you remember the shop or guy that trued your tires?

 

Check those wheels very carefully. I had a wire wheel that had a crack near the spokes and did the same thing at 40 MPH.

 

Measure wheelbase on both sides of the car. They need to be the same