Limited steering in both directions

[Tmooreheadf]

I have a 24 Touring car we have had for 15 years. It has always had a steering issue so I have decided to figure out what's causing the issue and a possible remedy.
The car drives well, runs straight, no tire wear, but takes a lot of area to turn it around either left or right. It has a 4:1 steering ratio and is easy to drive except when turning in tight spaces. The steering gear box is centered in the slot and the pitman arm is facing straight down, similar to the other T's when sitting with the wheels facing straight forward. Pitman arm is the same length as the other T's. Toe in is set 1/16" as described in the manual.
King pins and all the rest of the steering components are tight with minimal play.
So, if anyone has an idea what might be going on, I'd appreciate any thoughts. Like I said earlier, this car has always had this issue and I've always just put up with it. Driving on a recent tour, other T's behind me had to wait while I turned around. Time to get it fixed!!!
Thanks
Tom

[Stephen_heatherly]

Tom, I would begin by the front wheels as far as they will go in both directions. Note if the spindle arms come into contact with the back of the front axle. Let us know what you find.

Stephen

[Scott_Conger]

Tom, there are several versions of pitman arms, so to say yours is like everyone else's, is probably due to small sample size. If you truely have 4:1 steering, you have the shorter "arc" safety groove in your gear case, then the limiting factor in your turning would be a too-short pitman arm.

On the other hand if you really have 5:1 gears in the thing because it was "improved" by someone (and you don't realize it), you will be limited by the shorter groove in the older gearcase. This is something missed by EVERYONE who updates their steering from 4:1 to 5:1.

Here's an example of the two different gearboxes...

late and early case with groove .jpg (27.56 KiB) Viewed 1152 times

photo courtesy of Dan Treace.

[TRDxB2]

Pictures always help to visualize potential issues.
Questions:
Is the turning radius the same when making a left u-turn versus a right u-turn?
Have you checked to see if there is any interference of the steering components hitting the frame or wishbone limiting steering?
Are there any modifications to steering components, including APCO spring loaded ball caps?

[Tmooreheadf]

Yes both sides are the same.

[Art M]

Scott
Thanks for the information. I never realize this difference the groove.

Art Mirtes

[Scott_Conger]

Art

you are welcome. It's a distinction lost on many if not most people. I myself have forgotten to mention is in the past on several occasions in which it may have been pertinent. Maybe this will keep my memory jogged. Dan Treace was kind enough to provide photo-documentation of this some time back and I have found it useful more than once.

[TXGOAT2]

One of the Model Ts strong points is its low speed maneuverability.

[Wayne Sheldon]

I have been aware of the difference in the length of the groove for a long time, although it wasn't until about two decades ago that I found which way it was connected to the gear ratio. And, certainly, the shorter groove can and likely will limit the turning radius somewhat. Maybe. What reason the 5/1 has the long groove and the 4/1 has the short groove? I don't know. It does help in identifying the gearcase for better fitting of proper gears. The outer gear cuts are slightly different, and although either 5/1 or 4/1 can work in either case, they do work better if properly matched.
I would recommend checking to see which case and gears you have! Mostly just to know what you are dealing with.

HOWEVER! Irrespective and regardless! And while there MAY be some minor limitation added by the shorter groove? The gear ratio DOES NOT have an effect on the limitation of travel! That limitation of travel is FIXED to the steering main shaft! The only thing that the gear ratio does is change the number of degrees the steering wheel has to be turned between the limits. The pitman arm in turn is FIXED to the main steering shaft, so its limitation is also unchanged by the gear ratio. Again, plain and simple, the only thing the gear ratio difference will change will be the number of degrees rotation needed between whatever limits are placed by other steering components, and in turn the leverage advantages and again in turn to some degree the amount of control (faster versus slower response).

It is a bit difficult to visualize. However, three dimensional angles and geometry do affect steering speed and limits quite a bit. I suspect this is where your trouble is.
I have had a couple of model T speedsters with larger than normal turning radiuses. This was due to the higher speeds and types of driving I tend to do with the speedsters. A lot of winding mountain roads at higher speeds makes me appreciate the self centering of added front wheel caster. The car tracks straighter and returns more quickly to the straight road after pushing through turns. To accomplish this, I add considerable caster to the front axle. If I recall the numbers correctly or close? Recommended caster is about 1 to 1 1/2 degrees or about an inch straight down from the king pin to where the kingpin points forward. I basically double that! I usually set them by eyeball, then drive it to see if it works the way I like it! One time, a car's first Endurance Run was a tough drive because I began with too much caster. It steered fine up to about fifteen miles per hour, and anything over twenty was murder! After the Run, I altered the wishbone to reduce the caster and the car drove beautifully ever since!
The side effect of added caster on all those cars, was a larger turning radius than a stock T had. It didn't take long to realize that the way the caster changed the contact angle of the tires, resulted in a loss steering angle on the road surface. Visualize it this way. The steering was in fact "tipping" the tires as much as it was steering them. It is somewhat amazing how much a small amount of change in the caster can reduce the tightness of the steering. It is all in that three dimensional geometry.

And by the way? That small amount of larger groove way out on the end of about a 160 degree arc? It is like a bell curve on a graph. A few degrees near the middle makes a big difference. The same number of degrees out on the ends make almost no difference. Three dimensional geometry.

[Scott_Conger]

The pitman arm in turn is FIXED to the main steering shaft, so its limitation is also unchanged by the gear ratio.

Yes, it is fixed. The pitman arm during that era is also modestly shorter as well. The greater rotational input allowed by the later gearbox allows it to swing a greater arc and with the shorter length, higher gear ratio, and a much larger steering wheel, steering ease is enhanced. Leverage; No mystery.

The whole thing is a system and we often treat the components as being wholly unassociated (often to our detriment).

[Scott_Conger]

as far as the machined arc is concerned, Mark Nunn provided the following information in an old post (thank you Mark)

02-23-22 Changed angle between centerline of case and the center of 13/64” radius at ends of slot for stop pin from 45 degrees to 51 degrees.
05-27-24 Changed angle between centerline and ends of stop slot from 51 degrees to 60 degrees.
09-27-24 Changed angle between centerline and right hand end of slot from 60 degrees to 65 degrees. Specified for 1925.
10-07-25 Changed angle between centerline and ends of stop slot from 60 to 62 degrees on left side and 55 to 67 degrees on right side

I'm not going to do the research, but I'll bet that drag link lengths were changed within days at the same time (there were several versions/lengths of drag links, having gone through several iterations over the years) to account for varying pitman arm length and increased/decreased/biased rotational input at the steering wheel.

Finally, ride height over the axle makes a difference and is compensated for between the '25 and the Improved Ford versions. Pooped out front spring can induce odd results vs a fresh spring holding the frame at the correct height.

[TRDxB2]

Since the issue existed at the time you purchased the car perhaps some of he steering components were changed. Also if other members in the club don't have the issue then I would compare your components having the same Model Year as you have. You did say that the pit man arm was the same as other's but what are the dimensions? As you know previous owners may have replaced things over the years
Still wondering if your drag link or tie rod are hitting something to cause a stop.

Drag link.png (162.23 KiB) Viewed 915 times

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[John kuehn]

It’s interesting about the pitman arms. The suppliers sell arm # 3547 which according to them fits 09-27. Are they aware there some year differences? Or is the difference not enough to cause any issues? But for some it can be? Maybe some of the tie rods were changed?

https://www.modeltford.com/item/3547.aspx