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?
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.
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.
"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.
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. >:D
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?
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?
@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
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.
Quote from: Big Fins on April 20, 2025, 12:03:59 PMLower 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
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.
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
115 mph is the mechanical limit of that car.
GPS speedometer begs to differ :P
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!
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
@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
Quote from: "Cadillac Kid" Greg Surfas 15364 on April 21, 2025, 11:51:38 AMWhen 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)
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.
IMO - 32 front and rear, with 35 being the max.
alirght, ill go ahead and drop my PSI once i get the chance, ill drop it down to 32 and then see how it rides, if needed ill see about dropping it down to 28 depending on how it looks
thanks!
-Morgan
If you are going to continue at the high speeds, then you need to have a chat to a proper tyre shop for the correct information and tyres.
The stupid factory pressures for 1971 and 1972 were way too low, BUT, gave beautiful riding for anything below the Speed Limits.
Plus, if wanting to travel fast, you need to have the correct speed-rated tyres.
Don't forget that the Factory recommends increasing the pressure by 4psi when travelling at prolonged high speeds. And I am pretty sure that the factory does not recommend exceeding the posted speed limits, even though the vehicle can easily exceed them.
Bruce. >:D
I recently put a set of the Vogue 1.5" WW's on my Eldorado. The Toyo tires I took off I always kept at 40psi front and 35psi rear. The Vogue tires list 50psi on the sidewall as max psi. This supports the weight of the car better and gives the tread a nice even wear across it.
Running 28 and 24psi will have you riding smooth and replacing the tires in 10,000 miles due to edge wear. Whatever is listed on the sidewall of the tires is what I run and have never had any issues with tire wear. YMMV! It's your car, do what you want too.
"The stupid factory pressures for 1971 and 1972 were way too low, BUT, gave beautiful riding for anything below the Speed Limits."
I always ran our '72 at those "stupid tire pressures" while cruising around our country roads... as Bruce states, (the factory tire specs")...gave beautiful riding." Indeed, the harshness of the suspension was dampened by the lower psi tire inflation. Once the Eldorado was entirely redesigned in '79 and "downsized," it also received the kind of updated suspension so standard tire inflation did NOT degrade the ride.
alright, so yeah probably around 32 front, 30 rear is where i wanna be. I cant run Toyos and such just because of the money, i couldn't even tell you what brand im running right now. The goal is eventually afford some coker tires, but thats later on.
Ill mess around with the tire pressures, see which is the best. Im willing to bet its not my only problem. My suspension definitely needs bushings and such replaced sooner or later
I'm about to swap out the rear axle for the one on a 76 Eldorado I have in the yard. It has disk breaks so i want to go ahead and get that installed. Might as well nock the rear end out and change all the bushings on it
-Morgan
I personally would not do any sort of sustained highway speeds at 28, even at 32 the tires get pretty hot. If you have an IR temp gun just try it. Its quite a big temp increase for every PSI you drop and that can't be safe.
As far as what the ride is like around 40 it depends on what you are used to and expecting. If you are used to a modernish car that basically has no sidewall like a 60 series or shorter then 40 psi probably feels normal to you. IF you drive a truck most of them ride like trucks too so again feels normal. I like and want that land yacht feel where you don't really feel the railroad tracks and only know you went over them if you had the windows down and heard it.
The lower pressure lower life I don't really see as a huge problem with how often most of us drive these cars. Age is usually the reason to replace tires and it just seems to get worse as time goes on. They may be 'better' tires within their life of 5-7 years but at 8 it seems more often than not they are falling apart. I'm not saying it was ever good to run say a 10-20 year old tire but I know we all have done it and it used to be fine.
In this case of being a daily driver things are a little different but if the lower pressure helps then perhaps that will just be the cost of comfort. Buying new tires every couple of years is still cheaper than a car payment.
I'm not sure I have heard of anyone doing rear disc swap in these cars. You could run into some issues up front. The disc cars used hydroboost like the trucks and diesels so if you just order the MC from a 76-78 you would want to make sure the pushrod length and such all matches your vacuum booster. You also have to wonder why they did the hydro boost? Vacuum not giving the desired performance so if you don't also do the hydro will you not get the gains you are hoping for? I think you really have to be careful with the amount of braking in the rear, it doesn't like to stay back there during heavy/panic braking.
I would also assume the prop valve is different between the disc and drum cars so you will likely want to replace that too. On the drum cars it seems like at least under light braking it sends a little pressure to the rear before any goes to the front. I'm not sure if this was a performance thing or maybe to just keep the car more level vs nose diving? Don't want to spill your champagne like the peasants in their Fords and Chevs. I don't recall noticing that delay when bleeding a rear disc car but its been a very long time. Maybe the delay was just due to drums and taking up the extra slack?
Also there is some little nugget in my brain about 75 axle being different in that it was a one year only that had some extra sway bar or something. It may be that you can't put a 75 in anything else so you may be fine putting something else in the 75.
thanks, yeah like you said its a trade off. As a daily drive tire wear is something to take into effect, same with highway speeds and opening her up every now and again. I don't have a temp gun but i do know someone who does so I might try barrowing it from them to see how my tire temperature behaves at different PSI
With the rear disk swap, I'm not really looking for any extra performance, but i do want the ease of changing out disk breaks over drums. Drum breaks are a nightmare to change and adjust. As far as i can tell the way my breaks are distributed is with a majority to the front wheels over the rear, 60 - 40 i think it is, might the more drastic then that.
I would love to also switch to the hydro boost breaks, I have all of the lines to do it with in the 76 eldo, however they only made a limited run of those boosters for i think 3 or 4 years. And I can only find 1 or 2 for sale online each for like $300. This puts me at a choice, since im going to be driving this car for a long time as a daily, I don't want any essential parts, I.E. breaks to be imposable to get if they go out. And they still sell rebuilt vacuum boosters for like $70 online, and there is a big stock because of how many cars they were used in, so for the time being they are really easy to get ahold of. If it wasn't for that problem I'd already have the hydro boost in my car
I did not know that thing about the extra sway bar, I guess ima have to jack both cars up and compare them, I figured it would be the same thing just different style hubs and a different end to the axle. now that I think about it, im going to have to make sure the level ride system can hook up in the same place, It should be the same, the system looks the same, but now im unsure
Thanks for that information, might have just saved me a LOT of time
Have you worked with rear discs with the parking brake built into the caliper? They are not as easy as a front ones and way less reliable.
Several years ago I was told by a shop that there are like 2 hydroboost rebuild kits that cover 90% of the boosters made for a 40 some year range so most of the time they are easy to rebuild.
Ive worked with those kind so much as changing them out on a Miata, and yea they are a pain to get set right, but that miata also had very little adjustment for the parking break
I know i can get brand new calipers for it, and i believe its just a matter of setting up the parking break right? Like its a pain, but not near to the pain of drum breaks i would think.
Are you saying the parking break isn't as reliable as the drums?
I might try that, if i can rebuild the booster I already have then it might be worth switching over. I know a guy who actually might be able to find a kit to do that with
The calipers don't tend to be as reliable because of the added parts and seal involved in the parking brake. Perhaps if you use it all the time on a daily driver they are more reliable? I keep forgetting this is a daily driver. Sitting and not using em are hard on em and they tend to get stuck.
The boosters are still used on the heavy light trucks and diesels so there are shops that rebuild them you just have to find one.
ok, yeah that makes sense. Sitting does horrible things to any car, and i can see unused seals just going bad if not used consistently.
If i can get the better breaking from the hydro boost and the ease of changing breaks from the disk breaks that would be ideal. Ill see about getting one of those rebuilt kits and rebuilding the booster. It cant be that hard if I got all the right seals and such. Might have to get all of the rubber lines re-made however, that 76 was not kept in good condition and i don't trust those lines one bit.
and yeah its a daily, as in i take her to school, to town or just to go to a friends house. she's my only car and gets a lot more wear then most other classics now-a-days, but also means stuff stays in use and doesn't sit and go bad. The car was always like this, im the second owner of the car, the woman who owned it before me last titled it in 2016 and there is some evidence that she drove it consistently at least until 2005, which probably explains why explains why everything was still in pretty good condition when i got it, and the engine and transmission are still original and still running like a champ
FWIW my experience with Eldo rear brakes is that even the drum brakes will lock up with hard braking. There is so little weight on the rear end and much less when the car nose dives on a very hard stop. In the (something like) 500,00 miles I put on my '72 the rear brakes sasw so little wear I believe I changed the shoes 3 times.
Greg Surfas
I changed what I assume were original shoes in my 73 when I got it with around 50k on it. I don't recall why, I'm thinking the lining had come loose or cracked on one side or the other. Its now got like 120k that included some trailer towing and last time I checked there was still like 3/4 of the lining material left. I too think they lock up fairly easily.
Yeah my experience reflects that, with them locking up easily, sometimes even when you don't think your breaking that hard they just decide to. I bet the disk breaks will do the same. I'm just hoping the disks and the hydro boost can improve the breaking a bit. Everyone seems to always slam on there breaks last moment, and in newer cars that works out but in my boat its cut close sometimes, with the people in front of me slamming on their breaks at the sense of a turn
Also earlier today I was able to look under both cars and can say there is no difference in the axles. Sway bars and all are the same from what I saw. The axle off of the 76 was rusty as all hell and needs to be cleaned up a lot. Also needs new metal break-lines, but i figured that. The parking break system also looks very easy to swap out, as they connect to the main line in the same spot as on my 75.
The only thing i need now are calipers pads and rotors, and the seal kit for the hydro boost as well as new lines for that. Then its just a matter of re-building everything and swapping it over
Vehicles have brakes. B-R-A-K-E-S.
Break means to have something come apart.
Cap,
My 72 with the discs up front and drums in the rear is, in my experience, a very strong system--- If I apply the brakes hard, I can make the car skid. Your original system might simply be old, out of adjustment and needing a total refresh. I owned a '67 Eldo (daily) with drums all around, and it was frightening in a panic stop or a high speed slow down, so that I was always careful to leave enough room. James
I too have pushed my '72 Eldo with stock brakes, and have never had a problem with them, even in panic stops, and hard braking.
But, I would be very wary of hitting the brakes at high speeds, like the ones you were referring to.
Plus, my car has the Track Master Brake option. I found that my previous '72 Eldo Coupe also had the Track Master, and that saved my twice, once on a heavily cambered road, in the wet at a junction, and another time, on the highway, pulling off onto the verge, which put two wheels in the gravel, whilst the other two were on the bitumen. Both times, the car stopped straight and true. I didn't realise the car had the option, and was shocked just how good it was. This made me look for that option when I was looking years later for the Convertible.
Bruce. >:D
Alright, im looking for better breaking, but if it isn't really going to make that whole lotta difference then ill save my money and put it elsewhere. She still needs some body work to iron out rust spots, a paintjob and a new vinal top, plus a bunch of small things still anyways, and I need to rebuild a 500 engine and transmission soon to swap in her, and i know that's going to cost me a pretty penny
at the very least ill think about it, I still want to do the rear disk swap just for future proofing, even if it doesn't improve breaking. Might just put it off for a minute until i get my ducks in a row. The hydro boost system is still something i want, but again, lots of money into something that wont help a whole lot so probably going to push it all back until i got the spare cash for it