Technical Wheel/tire bounce - vibration

Need help with wheel bounce/vibration. Firestone Deluxe Champions 5.00/5.25 x 16 on steel wheels. Dropped axle frt end with Buick drums. Recently computer balanced and checked for out of round. Both on the money. At 65mph and above I get a vibration. Upon getting vibration, the front tires are dribbling up and down. Any suggestions ????

 

Shock absorbers. I'll bet you need new ones.

 

Using MG type rear lever shocks

 

Long shot but if you know anyone with an old spin balancer that balanced the tires on the car that would either confirm or deny that the whole enchilada was in balance.......process of elimination in other words.

 

I remember years back, where some shops would have a balancer that would roll up to the car tire and spin it at high speed while still mounted on the car.

 

I agree with 31Dodger.. Shocks.. Replace with regular shocks or friction shocks that you can adjust...

 

Has it always done this or did it just start recently.

 

Yes,check your on car balance.Often the hub and or brake drum is out of balance, if you can't find a shop that can spin n balance on car.; then try this,;jack up front axle so wheels are off the ground,back off brakes adjustmint,tell you can spin tire with your hand very EZ and it cost by it self. Let it stop on its own,with small little part of tape,add it too were the bottom of tire stoped,spin again and mark again with another if a def place=do it 3 times if all 3 tape parts are close to each other,your tire is rolling free enough,if not find if drag is comeing from brakes,or bearing are dragging an need to be backed off 1/8th turn/or going bad. If reading is nice an close=that bottom marked point of wheel is the heavy point/add some tire Wt. to top of rim,left marked spot up to 3;00 or 9;00{dose not mater} an see if the tape fall back to bottom again,take note of how fast or slow it falls=slow means your close,just add a tiny bit more next Wt. you added before.

Now about the shocks your using,take off link from axle and test by working arm up and down,if its real EZ,you need to work** on them or replace. Although the shock body is mounted OK,the arm and link is not,it is too far away from the tire{too close to center of car were it mounts to axles, Just a few in. more near the tire matters. **If shocks are too EZ,an you need to know how to get them better,ask? Some can't be fixed,but most can.

Added some info in post #19

 

Always --- I thought it was an out of round tire issue but ruled that out.

 

I'll try your balancing method.
With regard to the shocks, I was thinking of shortening the lever arm to get more shock travel action for a start.

 

You might also consider checking the toe in or toe out.

 

I'm surprised those Firestones are round.

 

I've tried various toe in and tow out measurements with no change in problem.

 

A tire can balance out just fine and still have a tire out of round or wheel out of round problem. Take them to a tire shop that has a Hunter roadforce 5000 machine. It will give you a road force number, anything in the 30s is bad and will never ride smooth even though it will balance. Most of todays radials usually have a road force number of 10 or below.

 

High speed vibrations can be caused by several thing or a combination of things. Some that come to mind beside shocks and balance are: cracked wheel, loose wheel bearings, loose steering components, insufficient caster.

Wheel and tire balance problems usually come and go and manifest themselves at the same speed and then go away.

I'd put my money on those shocks.

 

Is that the type of balancer that applies pressure to the tire as it'stands being spun?

 

Yes

 

Yep That's a Spin Balancer....Put beans on the table in college bustin tires, had the old bubble balancer and the Cadillac was a spin balancer. Looked kinda like a floor polish machine.

 

You said;"With regard to the shocks, I was thinking of shortening the lever arm to get more shock travel action for a start."

Fact is if all other things are OK,likely the shock,if its working by its self,can be OK as arm is,yet would be better if improved on.
You may find all runs find after fixing a hub/drum out of balance{IF you find one}an need not do anything but have fun driving.
Shock arm langth is not your shock prob,but that it goes in closer to center of car is a small part. Dose not mount out more too tire{that is if shock is working OK} Arm can be heated an bent outword an new link mount point made,but before even thinking about arm change,find if they are in fact working well by there self.
On MG they mount with in only a few in. away from tire,your frame is not that wide,so shock is inboard more,so even if its working well by its self,it acts weaker,it can't control the same load.
The arm shocks can be cleaned,so valving get no dirt in valve,plus can be made stronger just by using thicker shock oil in them=stiffer. For racing MGs back in the day,thay did that,plus some guys got fancy with shock spring valve settings. MG front shocks were in combo with "A"frame as one part with shock built in to it.
Don't cut the arm shorter,that will not help and it will also give less travel not more.

 

Does the vibration stop at 65 when decelerating?

 

Went through a mess with coker junk. Had to prove to them the roadforce numbers before they would send different tires or refund money. Ultimately returned the tires and purchased Diamond back tires. Smooth as a whistle.

 

Yes

 

Do you know your caster angles?

 

7 degrees positive

 

That should be plenty of caster if the frame rake is reasonable. I'm not too familiar with your shock set-up. Can you check them like a tube shock? You know, jouncing the car and see how many times it bounces. Does the vibration seem worse in hot weather? That would be an indicator of the shock also I think. We should really be calling it a dampener. Especially since the are an English design. LOL

 

Same results hot or cold.
Shocks are newly rebuilts. Have pretty good resistance. Front end doesn't keep dancing when jounced on. Shortening the arms should give me more resistance.

 

When you did the Buick drum swap did you remove the balancing weights that were on the Buick drums?

 

I'd hunt down someone or a shop that has an on the car spin balancer even if I had to drive a ways to do it. I have a Hunter that I picked up off a guy who used to have a full service service station that got tired of it being in the way. Can't remember the name but there is one out there that uses a strobe that is spot on accurate and doesn't use any attachments on the wheel meaning you can balance it with the hubcap on.
You might check with the truck shops in the area that do big trucks especially spring shops that work on trucks and motor homes as some of them have a bigger unit to use on the trucks. The main thing is spinning the tires on the rig to see if there is a balance issue even if you can't balance them there. They are either going to spin up and be smooth or shake and bake at a certain speed.

 

That I don't know. Someone else did the drums. I wouldn't know where the stock balance weights would be.

 

That would be ideal. Then everything is balanced as a unit. So many of the older shops are either gone or they trashed those old dinosaur floor machines. I'll have to put on a search in my area.