oversteer problem, one more question

[taipan53]

as i mentioned in an earlier post I have a 1966 ffr mk III. I intend to replace the rack. 15:1 to a 20:1. i'm coming up with part numbers that appear to be from a fox body mustang from where I think the current rack came. part # 712571. the agr rack listed in the same ad. shows a 20:1 part # 711061. could this possibly be the one i'm looking for or am I just lost in the woods. as before, any help would be greatly appreciated.

p.s. i'm told that a number of parts in my car came from the fox body.

[Tom Wells]

taipan53,

First, here's a page that gives what I think you are asking for: info about the various AGR racks -> Ford Applications - AGR Performance - MB Motorsports

You can compare the two.

I admit to being curious about why you think this would affect "oversteer?" Maybe you are using the term differently; it usually refers to the response of the car to a throttle and/or steering input, not the ratio of the rack itself.

Tom

[taipan53]

thanks tom,

perhaps I am using the wrong terminology. let me say it this way. a very slight movement of the steering wheel results in a dramatic change of car direction. in other words a sneeze can = a lane change. I like to call the steering "twitchy". am I making better sense?

[Tommy]

Those of us who read your original thread understood that you were talking about overly sensitive steering. The term oversteer means something else. It describes a car that tends to have the rear end slide toward the outside of a turn causing the car to turn more aggressively into the turn than the driver intended.

[Tom Wells]

taipan53,

Aaaahhh, now I see.

I have the 15:1 power rack in my Cobra. The guy who did the final assembly drove it and used exactly the same word (15 years ago!); twitchy!

He was used to the 20:1 non-power steering so it was a kind of "step change" for him. He liked to "wind" the wheel to get the car to change direction.

After driving mine 35K+ miles, it is enjoyable to me - I do some track time, so it suits my style to think about a corner and have the car follow my thoughts exactly with a slight turn of the wheel. Agreed, it would be problematic to have unsought lane changes - so attention must be paid. I didn't agree to the twitchy behavior - just need to have calm hands and the car is stable as it can be.

So it suits my driving style to a tee, but maybe not yours. As my wife's grandmother used to say "Thank goodness everybody has different tastes, otherwise they'd all be after my old man."

Set it up to suit yourself; don't let anyone else's opinion override your preferences!

Tom

PS: Another factor in "suddenness" of direction change is alignment. If it's off, it can make the turning behavior squirrely. Have you checked your car to be sure?

[taipan53]

Tom,

I had the alignment checked. guys said it was spot on with nothing worn, loose etc. also the link you sent me appears to be exactly what i'm looking for. thank you again.

p.s. I like your grandma's style!

[Morris]

Originally Posted by taipan53

thanks tom,

perhaps I am using the wrong terminology. let me say it this way. a very slight movement of the steering wheel results in a dramatic change of car direction. in other words a sneeze can = a lane change. I like to call the steering "twitchy". am I making better sense?

You have a bump steer problem.....and it needs to be addressed....changing the rack will have no effect on the car changing lanes as you have steering input.....the twitchy steering is the results of the front wheels toeing in or out as they go up and down thru the bump and rebound cycle of the front suspension....I've seen as much as 1/2" in 1" of bump travel ....and that is when the car changes lanes ....most of the MFG's don't know anything about bump steer.....

[taipan53]

tommy,

thanks for the clarification. you are exactly right. I should know from watching nascar races. oversteer/understeer going into the turns. and going out of them as well I suppose.

[taipan53]

morris,

thanks for the input. i'm working with an alignment guy as we speak. he seems to know something about bump steer and the issue of toe in/out is being checked. thanks again.

[Tommy]

taipan53,
You are into one of those areas where ordinary car mechanics are typically not up to the task. They are used to setting things back to the way they left the factory. ... Your car likely needs a race car or custom hodrod mechanic. You need someone who can look at what you've got, drive the car and determine whether the symptom is coming from a worn part, an incorrect part, or the design and layout of the suspension. As several other people mentioned, I too have a car with very quick turning response. The original builder wanted that because it was built as a dedicated race car. It took some time to get used to it, but I like it now. ... But it doesn't change directions just because I hit a bump (bump steer). You need to find out from someone who knows race cars whether your car was built wrong or was just built to provide very quick steering response.

[mdross1]

Toe in and caster both make a big difference in how these cars handle. Wide tires and the cars balance (scale) also greatly affect handling. As Tom mentioned, calm hands is also a very important factor. Get everything right you will be in for an exhilarating ride.