Pulling my hair out on my '49 Desoto

[Adam H P15 D30]

BTW, make sure the alignment shop (or you) set all the tire pressures first.  If they don't do this step or ask you first, find another shop.

[Sniper]

Another point, you NEVER hone an oillite bushing, it defeats the purpose of running an oilite bushing.  The FSM clearly says to ream it to specification.  Whatever shop honed it is a shop I would no longer use.  I got to wonder if reaming them twice after the hone job made them out of spec?  Did you measure?  I wonder if what is causing the galling is also what is keeping the steering from returning, because something is binding. 

[desoto1939]

Sniper: I know that on the pilot bushing for the input shaft is an oillite bushing and there is a specific tool that was produced by the Miller Tool company for MoPar dealershipa inwhich you put the oilite bushing on the end of the tool and then  hammered the bushing into the pilot bushing hole inthe flywheel and then this same tool would then be used to bush the oillite bushing to the proper size opening.

 

But on Kingpins these are bronze metal bushings that are also installed via a factory miller tool that pushed the metal bushings into the opening for the kingpins and then the service manual states that you need to line ream the bushings to the proper opening to insure a pefect fit.

 

I have botht he piolot bushing installer and removal tool and the miller king pin tools that were the factory tools that were used by the dealership

 

I can attach pictures of the tool and the miller tool instructions taken directly from the Miller Tool catalog.

 

Yes i agree that something does not seem correct and something is different after he changed the front suspension.

 

I asked the question does he have the same issue with Bias ply tires vs the radial tires and have not heard anything either way.

 

Rich hartung

desoto1939@aol.com

[Sniper]

Pretty sure on a 49 Desoto one end is a bearing, the other a bushing.  The FSM clearly states to ream to size. 

 

39 Desoto otoh may very well be bushings top and bottom and those should be line reamed.

 

Also pretty sure the Miller tool is a burnisher for the pilot bearing.

 

 

[desoto1939]

1 hour ago, Sniper said:

Pretty sure on a 49 Desoto one end is a bearing, the other a bushing.  The FSM clearly states to ream to size. 

 

39 Desoto otoh may very well be bushings top and bottom and those should be line reamed.

 

Also pretty sure the Miller tool is a burnisher for the pilot bearing.

 

 

Sniper as I stated the tool that is used to install the pilot oilite bushing is also used to burnish the pilot bushing to the proper size.  ANd on my 39 desoto there is exposed roller bushing onto of the kingpins.

 

I am not an expert but only trying to help with some input and maybe there isa difference inthe kingpin style

 

Rich Hartung

[James_Douglas]

On 7/23/2020 at 1:04 PM, Sniper said:

Another point, you NEVER hone an oillite bushing, it defeats the purpose of running an oilite bushing.  The FSM clearly says to ream it to specification.  Whatever shop honed it is a shop I would no longer use.  I got to wonder if reaming them twice after the hone job made them out of spec?  Did you measure?  I wonder if what is causing the galling is also what is keeping the steering from returning, because something is binding. 

 

As a rule you are correct. I think, but would have to go look at and check, the bushings are in fact a bimetallic part and not a true oillite.  The king pin side play, measured is well within specification. Now it is a moot point as the top has the factory correct needle bearing and the bottom bushing I reamed.

 

Given the large amounts of grease and the grease cut in the bushings...the lubrication effect of even a true oillite bushing would be of little consequence in a king pin installation with all that grease in there one would think.

 

James

 

[James_Douglas]

On 7/23/2020 at 2:06 PM, desoto1939 said:

Sniper: I know that on the pilot bushing for the input shaft is an oillite bushing and there is a specific tool that was produced by the Miller Tool company for MoPar dealershipa inwhich you put the oilite bushing on the end of the tool and then  hammered the bushing into the pilot bushing hole inthe flywheel and then this same tool would then be used to bush the oillite bushing to the proper size opening.

 

But on Kingpins these are bronze metal bushings that are also installed via a factory miller tool that pushed the metal bushings into the opening for the kingpins and then the service manual states that you need to line ream the bushings to the proper opening to insure a pefect fit.

 

I have botht he piolot bushing installer and removal tool and the miller king pin tools that were the factory tools that were used by the dealership

 

I can attach pictures of the tool and the miller tool instructions taken directly from the Miller Tool catalog.

 

Yes i agree that something does not seem correct and something is different after he changed the front suspension.

 

I asked the question does he have the same issue with Bias ply tires vs the radial tires and have not heard anything either way.

 

Rich hartung

desoto1939@aol.com

I do not have a second set of wheels or tires to test out your question...

 

James

[Jeff Balazs]

This is just a suggestion. Have you had these tires and wheels spun balanced recently. Might be worth a look see to see if anything is amiss with them.

Jeff

[50mech]

On 7/25/2020 at 12:23 PM, James_Douglas said:

 

As a rule you are correct. I think, but would have to go look at and check, the bushings are in fact a bimetallic part and not a true oillite.  The king pin side play, measured is well within specification. Now it is a moot point as the top has the factory correct needle bearing and the bottom bushing I reamed.

 

Given the large amounts of grease and the grease cut in the bushings...the lubrication effect of even a true oillite bushing would be of little consequence in a king pin installation with all that grease in there one would think.

 

James

 

So did the needle bearing make any difference?

[James_Douglas]

We got up to the house over the last few days. I was able to get the car off the rack and take it out for a drive. To recap, the changes I did were:

 

1. Changed from bushings to Torrington needle bearings in the upper of the spindles.

2. Screwed the eccentric all the way to the rear to provide as much Castor as I could. (I then set the camber)

 

The final readings were as follows:

KPI is 5.75 on the right and 6.25 on the left. In Theory the 6.25 is a 1/4 degree over.

Castor -1/4 on the right and -1 on the left.

Camber +1/4 and +1/4

Toe is zero or 1/16 in as per specifications.

 

Results.

 

A. On a right turn the wheels come back to center without any assistance from the driver.

B. On a left turn it requires a very little bit of assistance from the driver for the last 15 to 20 degrees before coming straight ahead. And, not much assistance at that.

C. At 55 MPH on a somewhat crowned, no too bad, but fairly fresh asphalt country road the car did not wander or seek.

 

So, it appears that either the Torrington Needle bearings and/or the bearings plus the change from -2 degrees castor to  -1/4 and -1  made a substantial difference.

 

My only issue is the eccentrics may be too close to the upper control arm (all the way back for maximum Castor) and could be rubbing and not "screwing" freely on the threaded pin. They warn about this in the service manual.  The next time I am up and have some time I want to take the car out onto the freeway and see if it is wandering at 65 MPH still or if I will get the same improvement I sensed going down that back road at 55 MPH.

 

My thinking is that I may unbolt the control arms at some point and and roll the pivot shafts some amount of turns to shift the eccentric so it is closer to the center of the space at the upper control arm. The question is how much would I do on the bottom and the top? A lot of trial and error work to hit it correct spot as after each change the KPI and the castor and the camber would all need to be checked again to see what the change did.

 

If I go down that path, anyone want to venture a guess as to how many turns on the shafts would equal how much change in the Castor?

 

James.

 

 

 

 

[James_Douglas]

On 7/27/2020 at 10:32 AM, Jeff Balazs said:

This is just a suggestion. Have you had these tires and wheels spun balanced recently. Might be worth a look see to see if anything is amiss with them.

Jeff

All new and checked and double checked.

[Adam H P15 D30]

Can you get any negative camber?  With positive camber you are riding on the edge of your tires. Pos camber is bad.

Adjust the toe to about 1/8 inch toe in. Will track a little better. With 0 or 1/16 toe you may also start wearing the inside of your tires. 

BUT with positive camber and more toe, you will eat the outside edges of your tires. 
 

[James_Douglas]

I wanted to circle back and report on the full road test. I managed to get out of SF and up to the house and get the car off the rack and drive it a good distance.

 

To recap. The car now has torrington needle bearings in the upper of the king pins in place of the bushings. I also managed to get -0.5 and -1 on the castor. The camber and toe are all within the published specifications.

 

The car was taken down a two lane back country road, some of which was relatively new pavement and some of it was bumpy. At 55 MPH the car steered very straight and did not wander like it has been. It also self centered after a turn like one would expect. I then ran it down the Interstate on a very long straight stretch. I ran the car up to 70 MPH and the car did not twitch nor wander like it had.

 

If I let go of the steering wheel, it is slowly drifting to the left, but it is not pulling to the left. One little finger on the wheel and it does not drift.

 

I have the adjuster cam as far to the rear as they will go. I am sure it is probably binding on the upper control arm which is warned about in the service manual.  I will need to pull them back a bit.

 

What I am thinking I am going to do is to drop the lower control arms at the inner pivots. I will take the front bushing out of the control arms and turn the pivot bars clockwise (looking from the front of the car) one or two turns. This will screw the pivot bar deeper into the rear bushing. Then I will screw in the removed bushing.  What this will do is shift the lower control arms forward causing more tilt of the king pins. This will increase the castor so that I can bring the adjuster cam closer to the center of the top control arm.

 

There is a service note someplace that warns that if you do not use the miller tool that you can get the lower control arm pivot installed incorrectly and affect the castor.  I am going to use that logic to try and get myself some more positive castor ability.

 

Since the needle bearing and the about 1.5 more degrees of castor did the trick, I know I am on the right track to getting this car to steer good. I have kept all the other adjustments the same on purpose so that I can know what is going on. Once I can get both sides to -0.5 degrees castor and the cam about middle of the range between the two ends of the upper control arm...then I will play with the camber to deal with the slight drift to the left, make sure the steering box (all new parts) is dialed in with the spring scale for worm and roller and get the worm gear (steering wheel) perfectly centered on the high spot. This last item is going to take some work.

 

It turns out that there are 3 published lengths for the drag link. I have confirmed that fact with Rare Parts.  It seems there was some supply issues back in the day as 1949 was a late start model wise.

 

I had set the tie rods to the exact same length as one is supposed to do with equal length tie rods...but the steering is a little off center. The "correct" answer is to set the drag link length so that the wheels are straight ahead with the tie rods at equal length. That is how this design is supposed to work. The problem is that for 1949 the drag link does not have adjustable ends. So I will either have to take careful measurements and have Rare Parts make me a drag link the correct length or I will have to set the tie rods to not equal lengths. That has implications for toe out on turns not being correct.

 

Did I mention how much fun this is?

 

Best, James.

 

 

 

 

[Tooljunkie]

As mentioned, toe plays almost as much a part in this as caster. 
and i dont recall 40 psi being the correct pressure for bias-ply tires. 
guess higher pressure lowers rolling resistance. 
seems you are getting close, and there are so many  variables. 
one change at a time, and make a note of the change. 
 

side note, my 2001 pt cruiser has only toe adjustment. After replacing a tie rod end with careful measurement it was difficult to drive,it took 1/2 turn on adjuster to make all the difference. 
 

changing caster or camber, toe is always reset last. 

[Sniper]

Someone here had an issue with their drag link adn we were able to work with him to get a replacement adjustable one made from parts bought at Speedway Motors.  Here's the link

 

 

[knuckleharley]

On 7/21/2020 at 11:26 AM, James_Douglas said:

I am running out of ideas on my restored 1949 Desoto Convertible. The steering sucks. I

 

 

 

No doubt I am missing something or it may be that this car was crap steering from the factory. My older brother, 15 years older, said that "the car never really did steer good". But, his memory is often not that good...

 

Any suggestions would be helpful.

 

James.

 

 

There is a lot of truth in what big brother told you. My 51 Victoria seems to be a good handling car until I forget what I am driving,and hit a curve in the road a little faster than I needed to be taking it.

These old cars handled good by 1950 standards,but we are used to cars that handle so much better these days and our standards are higher.

[Sniper]

All you need to do is look at the tie rod lengths on my 51 to see why it's twitchy sometimes.  Plenty of improvements in steering theory and design since those days.

[James_Douglas]

1 hour ago, Sniper said:

All you need to do is look at the tie rod lengths on my 51 to see why it's twitchy sometimes.  Plenty of improvements in steering theory and design since those days.

 

My 1947 Desoto steering as good or better than many modern cars. Of course the 139.5 inch wheelbase does not hurt...

 

And like I said on the last test run, all the twitchy went away.

 

I think it is a case of needing to test and "tune" and test and tune to get it dialed in.

 

James.