Changing a steering ratio using a longer pitman arm. need help.

OK My brain is frying!! If the steering shaft turns, say 90deg., the distance the end of a 5" pittman arm moves (amount the front wheels move) will be less than the end of a 6" shaft moves. Hence shorter arm= less steering movement for the same 90deg. of steering wheel movement. Does it steer harder with a longer arm because the longer arm generates more rotational torque that you have to overcome?? If that's true (and I suspect it is) I've been wrong for 50 years! Thank God for power steering!

 

you are correct.

 

Here's the problem with that thinking. In steering, unless there is a problem, the "Drive" end is always the steering wheel. When you turn the steering wheel any number of degrees, the output shaft ("driven") is going turn a given number of degrees, based solely on the internal ratio of the worm and sector. Changing the diameter of the steering wheel will not change this - It WILL change how much effort is required to turn the shaft, larger = easier, smaller = harder. It will also change how much movement there is at the outer most diameter of the steering wheel in circumferential inches, but NOT degrees of movement. 90 degrees is still 90 degrees etc. The ONLY way to speed up or slow down the steering movement is to either change the ratio of the box or change the pitman arm length.
Some people will say that changing steering wheel diameter makes it feel like the steering is faster or slower but really its just easier or harder. Purely laws of Physics.

 

Ya know, aside from ease in turning, the overall steering ratio doesn't mean a whole lot . . . and I'm talking about reasonable ratios for the street and not a dirt tracker.

You'll get used to it in a hurry.

My 32 does steer slow, but it turns the wheels far enough that a hard crank with one hand - without taking another bite on the steering wheel - will avoid a problem.
Another car coming into your lane, a piece of tire-eating steel etc.

Works on highway or in town.

First day I took my 32 to work - first trip anywhere in fact, it'd only been driven down the street and back once - the roads were damp, but didn't look like it.

I rolled the throttle on in 2nd gear on a country two laner and the car got out of shape rather quickly, mainly cuz I didn't expect it to get loose.
My fault with the damp road and too much power for the situation, but cranking the wheel over far as it would go with one hand broght the car back ok.
A little surprising since it was more than 45 degrees out.

Put the car together so that the proper relationships are there - IE: tie rod & drag link as near parallel as you can etc. - forget about all this ratio and effort stuff, drive the car and learn what it wants.

One of the biggest secrets with non-power steering cars is to have the car at least barely rolling when turning the steering wheel.
I can spin my 32 into an angle parking place with one finger when doing that.

Helps too that the tires are properly inflated.

And . . . properly inflated doesn't mean Max Sidewall pressure.

Pressures are for another post, but you may be surprised at what some folks run and end up with a good handling, good riding car...

 

Looking for some stuff on Vega pitman arms I found this old thread. Man do I miss Jay. :-(

 

5" Arm = 2-1 steering
6" Arm = 1 1/2 - 1 steering
Longer Arm = more turns Lock to Lock

 

Sorry but your answer is backwards.Longer arm outer end travels further for each turn of steering wheel.

 

Yep.

 

You might look into quickeners (1.5:1...2:1) Goes inline w/ steering column