Matt Harwood

Why does my 1929 Cadillac ride so poorly?

Recommended Posts

Reminds me of an article I read years ago by a guy who designed custom bodies in the twenties. He said they would order a chassis with appropriate springs for the weight of the car but always fine tuned them when the job was done. Road testing and trying different spring configurations. He recalled one Lincoln that defied their efforts to get a good ride. They tried 4 different sets of springs and 2 different shock absorbers. Finally they sent it out with the softest springs and both sets of shocks but it still wasn't quite right. He said, Franklins were the easiest to get a good ride.

 

You might show the car to your local spring expert and ask if they can calculate what springs it should have. You might run it over a weigh scale and weigh front and back separately. There must be some way to calculate spring rates and see if yours are too heavy. You never know what someone might have done over the years.

Share this post


Link to post
Share on other sites

Speaking of leaf springs going through an active life as they lurch down the lane, I recall a thought experiment I had some years ago.

Consider the leaf-sprung live rear axle, secured at the front by a pin and a bushing. At the rear, there is a shackle/pin/bushing affair, which amounts to a swivel which required to accommodate the lengthening and shortening of the spring pack as it compresses and relieves during its travel.

Consider further a steady-state corner wherein the car's roll causes the inside spring to pull up, possibly to the maximum of its travel. Conversely, the outboard spring flattens, perhaps to its limit.

Now think of the axle. By the unyielding mechanism of the shackle assembly, the axle is caused to move, or rotate, effectively shortening the wheelbase on he car's side closest to the center of the curve and extending the wheelbase on the outboard side.

These changes are slight, of course, but not insignificant. I expected that the wheelbase changes would produce a steering effect. I thought it might be fun, or at least instructive, to mount a half-baked gauge of some sort, probably involving a few pieces of scrap pine and a magic marker crudely scabbed onto the fender of the victim test vehicle to confirm. The readings from this would lead to an illustration of axle rotation under load. This would then show the rear axle's contribution to getting the car around the corner, or otherwise.

Sanity prevailed, but the the vision remained. I like to believe the Cadillac, Lincoln and Packard, et al chassis engineers chatted about this phenomenon "in the olden days".

This got kind of wordy, but I wanted to be clear. I should note I'm not an engineer, but I like to try to understand how things work and why they were were built the way they were. I enjoy old machines, from steam locomotives to pocket watches.

 

 

 

 

  • Like 1

Share this post


Link to post
Share on other sites

You are quite right, on a leaf sprung car the wheelbase does change as the springs flex. This is why the pivot is at the front of the spring. It means the wheelbase gets longer on the outside of the curve and shorter on the inside, automatically steering the car into the curve.

 

It also reduces shock when you hit a bump as the wheel can go back slightly as it goes up. Newer cars have large rubber spring mounts to allow more rearward compliance for smoother ride.

 

Torque tube drive pivots off the back of the transmission giving a longer arc and eliminating this effect. But it introduces another problem, of the Panhard rod which moves in a sideways arc. It must be carefully designed because on a washboard road in a curve it can cause the rear to move sideways .

 

Front springs were pivoted at the back so the spring line was parallel to the drag link. Good geometry here for good steering, bad geometry introduces bump steer.

 

Later they pivoted the front spring from the front for better ride but then they had to move the steering box forward of the axle.

 

There is quite a bit involved in chassis and suspension design even a primitive leaf sprung car.

 

The reason Franklins rode and handled so well was the full elliptic springs which have a lot of rearward compliance. Combined with the shock and vibration absorbing qualities of their wooden frame.

Share this post


Link to post
Share on other sites
2 hours ago, Rusty_OToole said:

Later they pivoted the front spring from the front for better ride but then they had to move the steering box forward of the axle

Can you elaborate please. 1930 Dodge Brothers 8 has springs pivoted at front and steering box is nearly a metre behind the front axle - long drag link required!

Share this post


Link to post
Share on other sites

Yes, I would like to learn more about this too.  My 25 Dodge has leaf springs in front, pivoted at the front but steering box is well aft of the axle (i.e. a drag link roughly 2 feet long is used).

Share this post


Link to post
Share on other sites
On 6/9/2018 at 3:59 PM, Spinneyhill said:

Can you elaborate please. 1930 Dodge Brothers 8 has springs pivoted at front and steering box is nearly a metre behind the front axle - long drag link required!

It's a matter of geometry. If a leaf spring has a fixed pivot at one end, that end of the spring will act like a lever 3/4 of its length. If the drag link is parallel and the same length there will be no bump steer.

 

In the setup you describe the axle and steering will be moving in opposite directions. I should think bad bump steer would be inevitable. Unless the axle is free floating and controlled  by a radius rod parallel to the drag link.

Share this post


Link to post
Share on other sites

Hmmm. Good point. I haven't noticed bump steering but then there is 3/4" play in the steering. I suppose this is why the manufacturers were looking for alternative front suspension systems during the 30s. Studebaker and Ford had transverse springs, others went to some kind of wishbone or triangular system with coils, ending in Macpherson struts for many.

Share this post


Link to post
Share on other sites

I have a 29 Cad town sedan.  I have only had it for 3 years and my focus has been on the engine and just making it run. There is so much left to learn (I have only driven it around the block once) but I will share what I know about the shock absorber links. 

 

The shock links are a socket that fits over the ball on the axle housing. There is a cup shaped rubber pad that fits into the socket and SOMEHOW holds the socket onto the ball(?) I popped one off  accidentally and cant get it reattached(!)   To remove the link properly you should unbolt the ball from the axle. 😞 

 

Classic and Exotic Services reproduces the rubber socket part

https://www.classicandexotic.com/store/p-3775-cadillac-shock-link-rubber-inserts-v8-v12-v16.aspx 

 

I have yet to buy or install them on my car (my rubber has turned rock hard) but somehow I think that is what is needed to make the attachment.

 

Also it should be noted that the rear suspension on the 29 Cad is underslung so if you pull out a leaf you will not be able to raise it up with a block/shim at the axle. 

 

Because I had the engine out on my car I just went ahead and pulled the steering box. (I dont think it CAN come out with the engine in place). Glad I did this because upon disassembly I discovered that the lube had become so dry it was as if the box was packed in coal. (actual rocks) So never underestimate how dry old hydrocarbons can become. 

Edited by m-mman (see edit history)

Share this post


Link to post
Share on other sites
5 hours ago, m-mman said:

popped one off  accidentally and cant get it reattached(!)

Have you tried lubricating the rubber socket with water? It might be enough...

Share this post


Link to post
Share on other sites

I have a 1929 Graham Paige 827 with Bijur oiler system (SAE 30).  It has at least 9 rear springs, I am thinking more like 12 springs, the oiler lubricates both ends, liberally (do it on the way out of the driveway).  The Graham-Paige has an excellent ride with 5 large adults or just me.   The fact the Cadillac acts like it is bottoming out or binding makes me think the springs are stuck.  I would think any truck shop could pull the springs and clean them at a reasonable cost?

 

Good Luck

1929 Graham-Paige 827.jpg

Share this post


Link to post
Share on other sites

One, that's an extremely handsome Graham Paige!


Two, I got the leaf spring spreaders and I'm going to spend some time this week after work trying to clean and lubricate the springs (I'll probably just use wheel bearing grease, no?) and see what happens. The spreaders are smaller than i thought so I hope they have the muscle to pull those giant springs apart, but if I take the weight off them and put the car up on jack stands, hopefully it'll work.

 

I'll post back as I progress.

Share this post


Link to post
Share on other sites

Matt,

   You just gave me an interesting thought.  if you jack up the back of the car, not under the axel, you will be lucky to get the tires off the ground.   I can jack up the Graham at least 16 inches before the tires will come off the ground.  My guess is, if the weight is removed the springs, they will break free, I would use penetrating oil on them before jacking up the car.  Not sure if it is a huge spring arch? or the extremely heavy rear end?

 

Good luck

Share this post


Link to post
Share on other sites
1 hour ago, Matt Harwood said:

One, that's an extremely handsome Graham Paige!


Two, I got the leaf spring spreaders and I'm going to spend some time this week after work trying to clean and lubricate the springs (I'll probably just use wheel bearing grease, no?) and see what happens. The spreaders are smaller than i thought so I hope they have the muscle to pull those giant springs apart, but if I take the weight off them and put the car up on jack stands, hopefully it'll work.

 

I'll post back as I progress.

 

I think you will have better results using oil rather than heavy grease. Use the grease after things free up. jack it up under the frame and leave the wheels and springs hanging as Ghram Man suggests.

Share this post


Link to post
Share on other sites

Thanks for the advice. That's what I plan to do. Lift it up by the fame, let the wheels dangle, and shoot some penetrating oil on the springs first. There's a pretty good build-up of old grease between the leaves that almost feels like dried RTV silicone, so I'm going to scrape that off with a wire brush, then I'll hit it with penetrating oil and see what happens. I do have these leaf spring spreaders, though--should I use those and spray some cleaner in between the leaves just to dissolve the old grease, then shoot some fresh stuff in there? As long as I have the ability to get between the leaves, maybe I should clean it and then lube it with something with a little staying power--something like grease? What do you think?

Share this post


Link to post
Share on other sites

I would clean off the grease/silicone with the wire brush on the ground.  I would spray them with a good penetrating oil, or brush on the atf/oil mix everybody likes to free up fasteners.  I would reapply for several days in a row, then take the car for a slow ride...they should break free.  There is a lot of force on the springs.  If they do not break free, I would plan on having a truck shop remove and cleaned up the springs.  

 

The pressure on the springs scares me, if you hang the rear end there will be a lot of potential energy stored in the rusted together springs, they will not be safe till they are apart.   A good big truck shop is used to that kind of problem, and will know how to safely handle them.

 

Good luck

Share this post


Link to post
Share on other sites

Just for an experiment, I went out and tried those new spreader tools on the springs. They work great! I was able to separate one of the bigger leafs from its neighbor and then sprayed a bunch of brake cleaner in there. Lots of rusty goo came out. Good sign, I guess. At least I know the spreaders will work and that there's rust in there. I hope the springs aren't rusty and pitted enough to lock them together.

 

That clears the way for the next step: get it in the air, take the pressure off the springs, and start spreading the leafs and cleaning the gunk out from between them. Still not quite sure what kind of lubricant to use--I'm still leaning towards grease which will be a bit more permanent than a thin oil and might be better if the surface is really rough, but maybe a penetrating oil would be better at working into all the little nooks and crannies where I can't get the spreaders.

 

I'll think on it...

 

 

Edited by Matt Harwood
Typo (see edit history)
  • Like 1

Share this post


Link to post
Share on other sites

If you are going to clean them up then use a good grease. The idea behind the oil was to drive it around oiled and the oil lets the rust liquify and springs to move. And then clean as you wish to do, then grease.

Share this post


Link to post
Share on other sites

Whatever you use, it must be kept lubricated. If you use a chassis grease with molybdenum disulphide in it, it will also have corrosion inhibitors coz MoS2 is corrosive. It must not be allowed to dry out - do those corrosion inhibitors work when it is dry?

 

Future maintenance is much easier if they are not lubricated. There have been posts on these fora of PTFE etc. pads being inserted between the springs. The clamps will need to be bigger coz the spring tower will be taller. Otherwise, just clean them and leave them dry works. Most cars are like that!

Share this post


Link to post
Share on other sites
3 hours ago, Spinneyhill said:

Whatever you use, it must be kept lubricated. If you use a chassis grease with molybdenum disulphide in it, it will also have corrosion inhibitors coz MoS2 is corrosive. It must not be allowed to dry out - do those corrosion inhibitors work when it is dry?

 

Future maintenance is much easier if they are not lubricated. There have been posts on these fora of PTFE etc. pads being inserted between the springs. The clamps will need to be bigger coz the spring tower will be taller. Otherwise, just clean them and leave them dry works. Most cars are like that!

 

You seem to be upside down, springs like lubrication  on this side of the Earth. To each their own!

Share this post


Link to post
Share on other sites

Not sure on the lubrication I seem to remember being told if you don’t have gators on your springs you do not use grease or was it oil because it will catch the dust etc and the act as a grinding paste and cause excessive wear, anyway I’m sure someone will chime in and clarify the situation 

Share this post


Link to post
Share on other sites

Grease and oil does attract debris, that is a given. Good maintenance is required to keep things clean and well greased. Gators are great additions if they are not originally equipped on the car. When cars were first introduced everything was open, the clutch, brakes, springs, valves, & Etc. The motorist was advised to keep things clean and well oiled. Of course we also don't drive our collector cars on dirt as often as when they were new.

Edited by JFranklin (see edit history)

Share this post


Link to post
Share on other sites

Matt, where did you get the spring spreaders? Evil bay?  

 

My my experience with Reyco and Mack Camelback HEAVY spring suspensions on big trucks is this: if the springs are noticeably rusted, as yours seem to be, the pack HAS to come apart and be blasted smooth, and leaves painted. The rust pits tend to "lock" the leaves together and not allow them to move independently of each other (think of Velcro and you have the basic result). I think all you will do with the spray cleaning is postpone the inevitable.....

 

Best,

Jase

Share this post


Link to post
Share on other sites

Oil is a wetting agent so will hold any dust that hits it. Grease is far less so and takes much longer to turn into grinding past.

Share this post


Link to post
Share on other sites

Matt,

 

Back in the day when I was turning wrenches on trucks we used a product called DRISLIDE on leaf springs.

         Bob

                

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now