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The heavy braking flex is an interesting concept, and likely very valid, especially with a lot of wheel offset, however in your case, are you pretty confident that was soley responsible for your improvement?

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I did an entire suspension overhaul

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I don't doubt an improvement, but what percentage the TR's played, would be really hard to pin down, if any.

And anyone that thinks my guess of ".33%" is likely 50% wrong, is 100% wrong. I meant .33%. Those good at grammar sometimes struggle at math, and of course the reverse can also be true.

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So I did some quick calculations on tie rod assembly flex. If we assume the assembly is 14" (?), and it flexes in one direction 1/4" off center, the change in length (toe out) is approx .012" at the tie rod. If both assemblies L & R wheel flex the same, that totals .024" and with a 1/16" being .031", I would say that brake induced flex resulting in a change in noticeable handling is "busted". And anyone that thinks a 1/4" of flex in a tie rod assembly is normal or OK, should seriously reconsider.

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I'm not an engineer, nor do I play one on TV. I do see a few things i would like to comment on. 012" at the tierod, would be more than that at the tire because the pivot point is at the end of the steering arm at the point where the ball joints pivot. Also a larger diameter tube is more resistant to flex than a smaller diameter one. The increasing size of motorcycle fork tubes are a prime example of this. I would be more interested in the forces needed to turn the wheels off center at speed rather than braking forces. That nasty gyrosope effect and all. Lastly and most importantly if the smaller size was adequate why did Ma Mopar bother to update it to the larger size even on the a body sized Volares and Aspens?

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So I did some quick calculations on tie rod assembly flex. If we assume the assembly is 14" (?), and it flexes in one direction 1/4" off center, the change in length (toe out) is approx .012" at the tie rod. If both assemblies L & R wheel flex the same, that totals .024" and with a 1/16" being .031", I would say that brake induced flex resulting in a change in noticeable handling is "busted". And anyone that thinks a 1/4" of flex in a tie rod assembly is normal or OK, should seriously reconsider.

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I'm not an engineer, nor do I play one on TV. I do see a few things i would like to comment on. 012" at the tierod, would be more than that at the tire because the pivot point is at the end of the steering arm at the point where the ball joints pivot. Also a larger diameter tube is more resistant to flex than a smaller diameter one. The increasing size of motorcycle fork tubes are a prime example of this. I would be more interested in the forces needed to turn the wheels off center at speed rather than braking forces. That nasty gyrosope effect and all. Lastly and most importantly if the smaller size was adequate why did Ma Mopar bother to update it to the larger size even on the a body sized Volares and Aspens?

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Well technically, regarding what really matters regarding Toe in is angle, not a distance, since as you mentioned, the distance would change depending on where you measure, but the angle always stays the same, and the diameter of the tire then comes into play, and measuring at say the leading edge of the tire is only a relative measurement since it only contacts air.

Stating a larger tube likely flexes less then a smaller one is a no brainer argument.

Determining the steering forces at speed is something that would likely have to be measured/tested to get an accurate measurement with tire scrub, gryro, hub, rotor, aero, etc forces involved, I would guess. However those forces would put one tie rod in compression, and the other in tension, where tube diameter plays little importance. No one ever complains their car is harder to steer at high speed vs low speed.

Not sure why Mopar would have later have (which I have no experience with) used a larger Tr, maybe to cut inventory in half, maybe as others have stated they are cheaper, maybe someone hit a kids foot when striking a curb and some SA lawyer wanted to know why moapr used such a small puny 9/16" TR, and nobody spoke up. Anybody know why Ford used a similiar sized TR on millions of Fox bodies in the 80's. I think these questions lose focus on the original question of why is a 11/16" "needed" in place of a 9/16" TR.

Regardless, you OK with a TR flexing 1/4" in compression to give .012" change in toe? I really don't think that is likely.

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You are correct that toe is an angle, not a distance, but small differences in toe make a difference that people can detect in the way the car drives. The only way we can set toe is at the outer edge of the tires. If you are saying that a 1/4" of flex results in a change of length of 012" for the rod sleeve assembly, I'm saying that the difference in the toe measurement would be a larger number.

At high speeds most steering input is very small so effort is really not the issue so much as the feel or precision of the steering.

Chuck a sleeve rod assembly in a vice at one end. I bet you can deflect it a measureable amount with just pressure from your hand.

I dont mess around with Fords, but dont Fox body cars use a rack? If so the inner rod is a ball inline with the sleeve which would take 50% of the offset force out of the picture.

I dont think its a question of "need" at all. People who make this upgrade are looking to improve how their car drives. This upgrade goes with poly bushings, bigger wider tires, braced k frames, firm feel steering boxes etc. If you dont do a least some of these other upgrades than you are correct. It would be a waste, if there were much of a price difference.

My guess as to why Ma did this would be the difference in tires. Narrow 14's with traction close to pressed cardboard as opposed to wide 15" radials.

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Chuck a sleeve rod assembly in a vice at one end. I bet you can deflect it a measureable amount with just pressure from your hand.

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Even though your example would correct about bending, I don't think that test represents the situation. A TR assembly is not really being bent, it is only distorting from a compressive force applied in line with its almost center axis. I hate to use this example because others will try to use it incorrectly, but it you take a straw and put it in a vice, yes you can bend it easily, but if you take your flat hand and compress it in a straight line along its long axis, it will take considerable more force before bending and buckling, which describes the hypothetic mentioned 1/4" deflection. A slightly more accurate test would be to take a TR assembly and put each end in a vise/fixture and use your hand (or anything) to push against the center of the assembly, not likely IMO to get a 1/4" deflection.


I thought the mustang TR has the exact same issues, except it is front steer, and the issue as others desrcibed would then be tension, not compressive under braking. My main point with the 5.0 was the TR outboard end is a single shear design, with a lot of offset, and likely way worse then mopar ever designed, regardless it seems to be accepted and work.

Hope no one mistakes being thorough as being personal

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Lets say that at the sector shaft this results in a movement of 2 degrees before the tires change direction. I cant recall offhand the ratio of a manual steering box, I want to say 24 to 1 but lets go with 20 to 1. This would translate to 40 degrees of movement at the steering wheel. While not a huge amount I would say this is s.omething that a person familiar with their own vehicle would notice a change in.

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That is the first time that multiplier effect has been mentioned and I think has a lot of merit and adds to the discussion