Hot Rods Crazy vibration in the front end

Hey all, I’m having a struggle and figured I’d ask for a little help. I just put an engine in my car and got it on the road. Sounds good, runs good. However, at about 45mph, I get an awful side to side shake in the front. Nothing at 40 mph, but as soon as I hit 45, it starts going crazy. I can see the front tires bouncing up and down and the grille shell is going back and forth like laundry in a windstorm.

The car is a model a ford coupe on an aftermarket 32 frame. Frame is boxed front to rear with tube crossmembers underneath. It runs split wishbones, gas shocks and no Panhard bar in the front. It has a new Borgeson Vega box and cross steer. About 3/16” of toe in, and 6 degrees of caster.

The rear is a triangulated 4 link with coilovers. Driveshaft is new and the rear and the trans output are both at 0 degrees. The driveshaft is down hill at 2.5 degrees (engine/trans higher than the rearend).

I expect that I need a Panhard bar on the front. It seems to be the consensus that it it necessary with cross steer. Could the lack of a Panhard bar cause the vibration? The car does not wander any more than any other straight axle car I’ve driven, nor does it bump steer or do anything odd while driving (except scare the shit out of me at 45mph). It does seems to calm down some if I drive through it to 50, but I only tried it once.

Thanks for the help fellas!

 

What tires are on there?

 

Firestone bias plies front and rear

 

Wheel bearings come to mind after seeing the front brakes. Everything correct and still adjusted as it should be?

 

Can't tell much from those pic's but looks like a ton of wheel weights on the left front. Get a panhard bar and try some other tires. Not related to vibration but I might want a little more back spacing on the wheels

 

I checked the wheel bearings this morning, that was the first thing I thought of.

I’m trying to hunt down another set of tires to swap in for a test. Can I throw radials on the front for s trip around the block?

 

There is a ton of wheel weights on all four corners. I have heard that ism-retry normal for the first one bias-plys

 

Tires/wheels balanced? If yes, there's still the possibility that a weight got tossed

 

I'd change the front tires and drive it again. I had Cokers on the front end of my roadster, bounced at 60 MPH like Dolly on a roller coaster. Put DB Auburns on it and it will hit 100 easy.

 

Try different tires and get those balanced by someone who knows how to balance a tire.

 

It is the tires. I threw a set of 215/70/15s on the front that were in my garage. Problem is almost completely gone. I expect the little that is left is the rears doing the same thing. Damn. Gotta find someone that knows about tire balancing…

Anybody have suggestion in the Detroit area?

 

Thanks everyone! What a wonderful resource this forum is. I really appreciate the responses and the advice. Once again HAMB for the win!

 

DB auburns you say? I’m not familiar with them?

 

glad you found your problem.... the tires aren't round...I remember some 65 years ago, dad would buy a set of tires from OK Rubber Welders.....they would have him drive them around town for awhile, then they would pull the tires and shave them round.
most of the bias tires, currently on the market. wobble too.....you can balance them to a point...but at some RPM they are going to turn into a basketball....
I've even waisted my money on 'road force' balancing....I did just as good with my old static bubble balancer
I'm giving up on bias ply tires on my cars that I drive a lot

Diamond Back radials with a bias look....Coker Classics also has a bias ply look radial

 

Hello,

You may replace all of the suspension suspected items and that is good. But, before you do all of that work, try this:

That funny handling of your tires may be as simple as your tires not being round. Yes, not round. It depends on the brand and quality of the casings, but the rubber sometimes gets thicker on one side or the other. The 50s-60s solution was to balance them with new weights. But, with new weights, you were just counter balancing and not making the tire ride in a round fashion.

So, the proper thing was to shave the tires. Sometimes the shavings left on the floor of the shop was horrendous. 1000s of miles seemed to be laying in a pile at the base of the tire shaving machine. But, it did make balancing simple and no mass quantities of weights. Now that the tire is round and balanced, the wheel alignment can take place.

If one just rebalances the wheel/tire and gets a new alignment, it still will give the same results. So, get those tires to a tire shaving place and watch how much rubber it takes to get it round. It will break your heart to see so much rubber on the ground.
Lion's Dragstrip 1958-59
We had all of our Firestone stock factory tires shaved and balanced on the 58 Impala. No one wants to go through the 1/4 mile with tire shaking. It definitely lowers the resistance as the tires were round.
Every time we got a new set of tires for any of our cars, tire shaving was the second thing done.

Jnaki


When I got a new set of Inglewood wide tires for my 65 El Camino, the shaving place was close by. So, I spent an hour of so getting those new tires shaved. My amazement was the rubber on the ground at the shop. But, the balancing took less weights and alignment made driving wonderful. No shakes, no drifting, added to the total miles cruising and long road trips until I got my second set. I put on more miles on my shaved tires, than my friend who just bought a new set the same time as I did and did not get the tire shaving. YRMV

 

Yep. They are round. I prefer that over Coker’s.

 

Damn that's nice car!

 

Diamondbacks are "Round, Not Brown".

 

That is exactly what I had to replace with less than 100 miles on them. Garbage. Utter garbage. I kid you not I thought I was going to lose control the first time those Coker Classics hit 60. Sheer terror.

I bolted those Auburns on and like @Moriarity says "smooth as a gravy sandwich". I was so impressed I bought four more for the wife's PU, this time with wide whites (that actually stayed white).

You could have a separation or something else going on but if the tires aren't round, no amount of weight will cure it at speed.

 

Put a dial indicator on one of the Coker Firestones. It had about .050” of runout. The test radial had about .030”. It is a tough measurement because the lugs make the indicator needle bounce all over, but I am in the neighborhood.

Front tires are 5.00/5.25-16
Rears are 7.50 -16s

They look killer. I may try to find someone to shave them locally.

 

In Detroit I'd say it is a fair bet you can find someone that still has the equipment and knowledge. Keep us informed.

 

So. I got a buddy that restores Duesenbergs and the like. His shop has a tire shaver and graciously offered to let me bring it by on Sat if I need to use it. Said I had to bring the hot rod, not just the tires. Seemed fair to me.

Anyway, in the meanwhile he suggested a tire guy they use and told me to bring him the tires and have him rebalance them. Dude was super cool and spun them up while I was standing there. First read was about 6 oz total. He then pulled all of the old lead off and spun it again. Needed about 2 oz total. He balanced both of the fronts and charged me $10 (can’t even buy lunch for $10 anymore).

Flew home from work, slapped the newly balanced tires on Beulah, and took her for a quick rip. ALL BETTER!!! No more issue! Hahaha!

 

Pics of Beulah for reference.

 

Gald to hear of the cure! A lot of guys post their trouble but never the fix and the end result.

 

She must have shook so hard it made her right eye droop.

 

You should still let your buddy shave 'em. Lost art... and you will notice the difference at higher speeds.

 

6 oz of weight on a front tire is a major red flag to me.... wow...

I guess that was spun balanced. I have always had decent results from those old Ammco bubble balancers.

When we went to the first spin balancers around 1977, they were problematic. We had to call service quite often. Those were not able to self calibrate, etc.

 

Haha! Ain’t that awful? It drives my buddy up a wall, he has to comment on it every time he sees it. Ah well, it is on the list for wintertime fix. But it is driving season now. Let’s rack up the miles!