1970s 75' eldo ride quality

[_Cap_]

This could 100% just me being picky, but when I'm driving I tend to a lot of bumps when driving at higher speeds. Its especially prevalent between 70 and 80 mph, after around 85 is tones down
My wheels were balanced around 4 or 5 months ago, so I'm not too sure its that, and its been this way ever since I had the car.

Its nothing major at most speeds, it rides perfectly fine, just a very light shaking past around 55 and as stated between 70 and 80 it gets pretty bad
All shocks are new, and new rear springs, but everything else from my account is original 50 year old Cadillac suspension

Is there anything in particular that could be causing this problem? torsion bars, bushing etc? Or is it best to fork out the money and just change out everything before it gets worse?

[35-709]

First thing that comes to my mind is tire balance, or you have a tire going bad.  Were the tires new when you had them balanced 4 or 5 months ago, or older tires being rebalanced?  Radial tires have a finite life, not necessarily determined by mileage, but certainly by age.  7 years or so may be all you will get out of them regardless of mileage because the compounds used in their construction deteriorate with age, some a little less, some last a little more.  A visit to your tire store for an inspection and/or balance check is in store.

[Big Fins]

Bent rims comes to mind. Most tire shops try to remove the tires on the wrong side of the rim and the older tire machines with bead breakers on both sides would not meet the tire, but force the rim up against the hold down, bending them.

Mount a tire and rim on a rear position, lay anything next to the sidewall and spin it. I'll bet all 4 rims are bent to some degree. Been there, done that. They can be straightened with an old car or truck frame in a junk yard with the 5X5 bolt pattern and a small floor or bottle jack. The jack being placed between a frame rail and the rim to move it back into the proper position. Very time consuming to get all 4 just right.

These FWD cars are soooo sensitive to perfect rims and balance.

[James Landi]

"These FWD cars are soooo sensitive to perfect rims and balance."


The fifty-five mph "dance" is a classic tell, and "Big Fins" suggestion regarding the rims may be the answer. Geoff's suggestion regarding  tread separation is also a possibility. I've experienced both challenges, and spent way too much  money having shops sell me parts I didn't need.   If you can observe your car underway, you may be able to discern the bent rims without having to go through much additional trouble.  My "suggestion/question," your front end might be out of alignment... but as suggested above, start with a close inspection of rims and tire separation.

[The Tassie Devil(le)]

I too can relate to the bent rims.

I had a request from a fellow Eldorado owner here in Australia who had bent rims from the tyres being improperly replaced, and was lucky enough to have sufficient spares to get him back on the road.

Bruce.

[_Cap_]

Well, the problem I'm having is I used to work at that shop, and I balanced my own wheels, they were pretty well balanced
If there was any noticeable bend in the rim I'm sure someone at the shop would've caught it, They are brand new tires as well and i just got an alignment done about a year ago
Its also been this exact same way for around a year now, as long as i can remember
maybe a ball joint? but you'd think it would get worse quickly over time if it was a ball joint right?

[TJ Hopland]

Chances are good all your rubber suspension bushings are shot so that isn't going to help things. 

Were you able to get the original CAX weights?  They seem to give the best results.  If you can get a good balance without them great but I think what happens is since the machine is expecting them at their location and stickons can't go there you end up chasing it and the tech just blindly keeps adding weights or just gives up. 

I'm not sold on the bent rim thing.  Over the last 30 years with these cars at times I have had access to a dozen rims and every time a shop blamed the rims I grabbed different ones they were happy with and nothing really changed.  I'm sure over the years I have ended up using ones that had been rejected.  It seems to be that the tires themselves and or how they seat on the rim has more runout than the rims. 

Other observations since becoming part owner of tire machines is these rims don't fit in modern(ish) tire machines the way you would typically mount a modern rim and it seems like they are a tight fit to the tire so you end up fighting with them a little bit so that could at the least put the tech in a bad mood but also could be where the damage comes from.  Just think if you are already in a bad mood and hate the car how much patience you gonna have at the balance machine?

[_Cap_]

@TJ Hopland
I could be those bushings, they are definitely worn out.
The rim fit pretty well on the tire machines we used, you have to take the tires off upside-down however. The Eldorado rims are practically small duelly truck rims, so you gotta put them on the machine upside-down
But no i used just normal modern weights, Im going to be working there here in the next few months, so it might be worth going ahead and balancing them again and see if anything is changed

You think its worth trying to adjust or mess with the torsion bar?  I know they hardly ever go bad, but it is a 50 year old torsion bar. And the car was never really parked, it was driven ever since 1975 so it has an ungodly amount of miles on it

[Big Fins]

Personally, I wouldn't even bother with the torsion bars unless the ride height on the front is off. But raising or lowering the front also changes the camber settings.

Regular wheel weights can be used IF you have the later wheel covers that have sections specifically made to place over the weights, unless you have a 4" section of weight in that spot. If you do, the tires were improperly mounted. If a balance requires more than 2 1/2 oz of weight in any given spot, the tire needs to be moved on the rim. If they are new tires, the dots need to be aligned with the valve stems. People that aren't tire educated poo-poo this idea, simply due to lack of education.

Lower ball joints on these cars take a serious beating. You have the entire weight of the front of the car on them. With the use of the thin chassis grease used by shops today, they need to be greased every 1500 miles. If you use the high fiber/high heat red grease, that's usually good for the 3000 mile oil change interval. It doesn't break down as bad.

Tread separation can be felt more at slow speeds. The car will wobble side to side as the separation gets worse.

[_Cap_]

Lower ball joints on these cars take a serious beating. You have the entire weight of the front of the car on them. With the use of the thin chassis grease used by shops today, they need to be greased every 1500 miles. If you use the high fiber/high heat red grease, that's usually good for the 3000 mile oil change interval. It doesn't break down as bad.

Thanks, ill definitely take a look at those ball joints once i get the chance, its been a hot minute since I've greased them.
Ill also go ahead and get the balancing Ironed out, If they aren't busy i may just balance them myself and make sure.

Bushing do definitely need to be changed, but yeah i doubt its the reason for the shaking. Most likely its what's causing the squeaking suspension though

[tcom2027]

Find a shop that does Road force Balancing. If the shop does it correctly. It's  uswd for balancing tires on modern performance cars. Expect to pay a bit more.

Driving a heavy car with old tires at 85 is crazy. I've driven fast cars most of my life, the last two, a BMW M roadster and the last a  BMW 750iL, 12 Cylinder, both capable of 140. Nuf said?

THey had speed rated tires that were less than four years old. THe roadster left because I had trouble getting in and out. I no longer drive fast as my reactions have slowed as I've aged.

When I bought my '02 65K Eldo four years ago it rode like a hard rubber tired fork lift in a dirt lot and was terrible in the rain. Tires were eight and nine years old. Took it to our local tire shop tire shop for road force balancing. Owner said, "Tony, get them off, now, they are shot. Look at the cracks at the bottom of the grooves, and that's only the obvious problem. "

I put a set of soft compound Continentals on and the car  rides, drives and handles like new.

 

[_Cap_]

yeah, that's why i got brand new tires on her. Surprisingly for her age she will still hit some speed. Not too long ago i was on a few mile straight at around midnight, got her up to i think 130 before she hit her limit
For the original engine and transition, and how many miles is on her she has been holding up very well.
Shows what happens when you don't let a car sit, and actually use them. She is my daily, and my only car, so she gets some wear on her, I've put about 16k miles on her, over the past like 1 and a half years of driving give or take

[Big Fins]

115 mph is the mechanical limit of that car.

[_Cap_]

GPS speedometer begs to differ 

[Big Fins]

I'll take your word for it then. I don't think you'll find me out there looking to go that fast. 110 in my '59 seemed to be just getting the oil warmed up, it held the road like a lead sled. My '76 is uncomfortable at 90. Or it's just me getting old, IDK!

["Cadillac Kid" Greg Surfas 15364]

FWIW I'd check that GPS. Stock motor just about runs out of HP at 3800 pushing an Eldo at 115 MPH. Eldo front end starts to lift at over 100 making it a bit squirrel y. ANY wear in the front end suspension, steering, or drive line just from natural wear and tear makes for less than an ideal ride. When my 72 was new I was comfortable at over 100 ( back way from Hwy 10 to Palm Springs), but 10 years later 85 was that comfort speed.
Greg Surfas

[_Cap_]

@Big Fins
yeah is that weird uncomfortableness i wanna rule out at those kind a speeds. for me at 90 it smooths out, but lower then 90 it gets weirdly bumpy, like i said around 70 to 80 ish is where it gets bad
but even through that I feel a lot of bumps and stuff in the road that im pretty sure i shouldn't feel in a Cadillac

It still floats most times (excluding the 70 to 80) but it has a very light shaking to it that i wanna get sorted

also speaking of this, question, for tire air pressure. The car says fronts at 28 psi and rears at 26. This is incredibly low with modern tires. Personally I run 40 in the front and 35 in the rear.  Is this something i should be doing, or is it actually good to run the 28 and 26 numbers in modern tires. The car came stock with Radials, but again a early and old design of radials

[_Cap_]

When my 72 was new I was comfortable at over 100 ( back way from Hwy 10 to Palm Springs), but 10 years later 85 was that comfort speed.

You think its possible that's what i could be experiencing, wear and tear on bushings and such, making the car iron out less bumps? I mean my shocks and springs are all brand new, and my level ride system is working perfectly (after i rebuilt the sucker) but all the bushings and joints are still probably from 75, except 2 ball joints which i changed out (the others seemed in pretty good shape)

[TJ Hopland]

40 psi has to make it ride like a heavy duty truck.  2-4 psi seems to make quite a difference in the ride of these cars. 

[35-709]

IMO - 32 front and rear, with 35 being the max.