Tie Rod Location

[Henry/Kokomo]

I attended a local car show on Memorial Day and was looking closely at some modified Ford Coupes (what else?). One of the coupes was lowered a lot and use what appeared to be early Ford suspension components, including a dropped front axle. To eliminate the interference between the tie rod and the wishbone that the dropped axle created, the builder had swapped the spindles side-for-side and put the tie rod in front of the axle. My first thought was that it was a clever solution to the problem. My second thought was to wonder what effect that had on the steering geometry. I'd be interested to hear what others think about this solution to the problem. Thanks.

[V8COOPMAN]

Originally Posted by Henry/Kokomo

My first thought was that it was a clever solution to the problem. My second thought was to wonder what effect that had on the steering geometry. I'd be interested to hear what others think about this solution to the problem. Thanks.

It's actually an awful solution for a mis-engineered and poorly-planned build. Although it looks "nifty", it totally destroys the geometry built into a front-end described as the "Ackerman theory". The next time you look at an old Ford spindle arm, notice that when the wheels are pointed straight ahead, the steering arms are bent such that the tie rod holes are located INBOARD of the king pin location. This is the design element that allows the inboard wheel/tire to turn more-sharply in a turn than the outboard wheel/tire, which must travel a larger radius than the inboard tire/wheel. When the spindles are reversed and the arms are located in front of axle without modification, turning the tires/wheels now has the opposite and incorrect effect as compared to when the arms were normally behind the axle. Steering will be awful. The pic below shows the effect encountered any time the wheels are not pointing straight ahead. DD

[woodiewagon46]

V8 is totally correct. Sometimes ether to look "cool" or to bypass other issues like oil pan clearance or a chassis that is too low, people do stupid things. Millions of dollars were spent by Ford engineering and guys do stuff like this!

[klicker]

I've always been curious about this. At least related to IFS... some have steering arms in front, some behind. Are the steering arms angled differently? or is there something else designed into the suspension? I guess the question is how do they set Ackerman with the steering in front?

[BILL WZOREK]

What would happen if you changed the caster on the axle ??

Food for thought >>>

[Mart]

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In the diagram above, imagine the two lines from the centre of the diff projected further forward in front of the axle. The steering arms would have to be angled outwards if at the front. The tie rod would be longer than the axle width. That's how they do it with the tie rod in front. It still works if designed properly. People who fit the ford spindles backwards cannot bend the steering arms outwards far enough to achieve this, (if they try to bend them at all) because of fouling the backplates. Normally these setups are poorly designed with regards to achieving correct ackerman. They still kinda work but with less than optimum tyre scrub anywhere away from the straight ahead condition.

Mart.

[woodiewagon46]

klicker, any time a car is designed all these factors are taken into consideration. There are "rear steer cars" and "front steer cars" meaning the steering components are front or back of the front end components. Sometimes people modify their cars and are unaware of the consequences. There is a post somewhere on this site that shows that someone actually flipped his spindles, in other words, installed them UPSIDEDOWN, this brought the steering arms out front. This of course changed the geometry of the spindle. He then asked how to correct the greatly exaggerated camber. I am not against modifying your car but use one of the many kits available to do it safely and correctly.

[V8COOPMAN]

Here is a drawing that shows the relative geometry and pivot points necessary for a "front-mounted" tie rod to work effectively. For those un-familiar with this theory, you'll note a line drawn STRAIGHT through the tie rod end, king pin, and terminating at CENTER of rear axle. Same applies with tie rod BEHIND axle. DD