I will tell you this I have been real impressed with the factory suspension using the spacers. Offroad the truck does a great job and on the road it handles extremely well. As a matter of fact I would even say my tiurck handles better than a Chrysler 300M I used to own and definitely much better than the Titan I had. I am thinking just the whole suspension setup on the F-150 is great.

Of course coilovers will be my next thing once the factories wear out but so far it has been over a year and not a single cv problem, alignment, rub or a vibration. Even the powdercoating on the lift looks like brand new.

 

The travel of the DL's are made for a 6" not a 8" so I think they might bottom out on some hard suspension flex.

BTW Fabtech also relocates the steering rack to maintain factory settings, Rancho might also but I'm not sure.

 

The steering rack looks to be in the stock position to me. They just put the mounts for the tie rod higher up on the knuckle. Yes this method does maintain the factory steering geometry, but it also makes the steering system work harder to turn the wheels therefore causing premature wear on the PS pump, steering rack, and tie rods... on top of this design flaw you're also adding the system (suspension lift) that carries this flaw to add bigger tires which will also cause excessive wear on all the same parts.

To obtain maximum leverage on the wheel assembly to be turned the steering linkage should:
1) Run on a horizontally flat plane and be centered between the upper and lower ball joints.
-and-
2) The point where the steering linkage attaches to the steering knuckle should also line up horizontally with the vertical center of the tire/wheel.

With the Fabtech (and other) kits you only meet the first criteria as you can see the tie rod attaches to the knuckle very high up on the tire. With the CST you meet both criteria.

I'm not saying the Fabtech kit is bad... the CST is just better, but that's why it costs more.

 

And another thing.

A rack and pinion steering system is not the choice steering setup for a truck in the first place, especially a truck with oversized tires. Look at what the Super Duties and all the other heavy duty trucks use; they all use recirculating ball steering systems.

A rack and pinion steering is historically a car steering system. I beleive the 2004 Heritage style F-150's and earlier all had recirculating ball systems. I know for sure the 1996 style and earlier did. Auto manufacturs started putting rack and pinion steering systems on light trucks when everyone and their brother jumped on the bandwagon and wanted to start driving one, but complained that they rode too rough and the steering had too much play compared to their old car. So hey... don't get a new vehicle, we'll make the vehicle fit your needs. That's also why they started putting P rated tires instead of LT rated tires on trucks.

This is another reason why the heim jointed steering with support linkage CST suspension is superior to others.

 

Can you please explain why number 2 needs to be satisfied to maximize leverage? To me, if I'm remembering my statics course correctly, it seems that the moment about the turning axis stays the same as long as you're located the same distance horizontally from this axis. Statics also says I can place this moment where ever I want along this vertical axis and it doesn't change the amount of torque needed to rotate. To me the CST and the fabtech steering systems seem have the same leverage for their steering system as long as they are mounted the same distance from the hinged point.

I’m visualizing a rigid door, hinged at the top and bottom. It doesn’t matter if I put the **** at the top, bottom, or middle of the door as long the distance from the hinges remain the same; It will still require the same force to open the door.

I’m not saying you’re wrong; I’m just confused because that statement made no sense to me. I’m sure I simplified something too much.

 

I know... I was kind of confusing myself thinking about it.

Ok the door is kind of a bad example to compare to a vehicle steering system, but it was the best thing I could think of. You're right about the force to open the door remaining constant regardless of the vertical position of the handle. The difference is that a door doesn't have a 2000 lbs load on top of it pushing it into the ground. If the tire were off the ground then it would make no difference, but it has the weight of the vehicle on top and the friction of the road on the bottom. These are roughly equalizing forces.

Ok lets go back to the door example. And for kicks say the door hinges can float vertically (like they're on a vertical track). Now put 2000 lbs on top of the door. So now the door has 2000 lbs. on top of it and its touching the ground at the bottom. Lets say this is a typical 7' tall door. Would you want the handle 1' from the top? If the handle was at the top and you applied a moment force in the Y plane I'm sure the door would move in the moment direction at the top a good couple inches before the bottom could break free of the friction at the bottom; or it may just break if it couldn't overcome the friction. You would want the handle in the center so the flexing above and below the handle would be equal and if anything you would want the handle mounted lower.

Again this is kind of a bad example because the force on the top of the door isn't the same as the force that would be on an upper ball joint. Also, the friction on the bottom of the door w/ 2000 lbs on top if it is going to be much greater than the friction from a footprint on a tire. The theory is there. You just kind of have to think of the system with rotation taking place in 3 places instead of just 2... the upper ball joint, lower ball joint, AND the tire to ground.

I'm not trying to be a know it all. I am a mechanical engineer, but I'm a newbie... only been out of school or 2 years. I could be wrong, but this is how I understand it to be.

 

Baja, all your arguments make sense to me, thanks for clarifying.

I too am a new mechanical engineer. I’ve been at it less time than you have; in fact I’m still in school. However, I think that since the knuckle is somewhat rigid, the only difference would be the stress in the knuckle itself, and not really affecting the leverage of the steering system. Assuming that the knuckle is rigid, I see not real added stress to the steering system in the Fabtech kit. I don’t mean to come off as an a$$ or a know it all either. I just haven’t really accepted argument 2 as a reason to say the CST kit is better.

 

I hear ya!

I also would like to think... or at least hope that the engineers at CST know more than I do. Therefore, they could save a lot of money in parts and production costs by just raising the steering linkage connection point on the knuckle like Fabtech does since they are after all designing and manufacturing the knuckle themselves; cost wise they could place that mount anywhere they wanted and it wouldn't cost any more or less money for them. Instead they decided to make some extravagent heim jointed bracketry to drop the steering. So like I said, they should know more than me and I agree with their theory, so I believe it's "better".

On a side note. If I was going to buy their kit I would definately upgrade to new shocks/springs and get rid of the spacer. The one downfall in their system IMO. The stock shocks and springs aren't rated to handle the additional weight of some 37" and aftermarket wheels that weigh 200lbs each like Josiah's!

 

Im not argueing that CST is one of the best lifts but why use a spacer!? I was going to go with the CST lift until I stumbled upon the spacer. Im sure its a good lift but come on. . for the price of the lift it should come with coilovers.

 

Agreed!

 

CST had no choice but to lower the steering system. If you look at the mounting point of the steering system to the knuckle, it’s located inside the rim. If you look at Fabtech’s lift, you will notice the mounting point is about as high as you could put it before interfering with the wheel. Now remember that the CST is an 8” lift, if you were to raise that point another 2” then it would interfere. Therefore CST had no option but to create a drop bracket for the steering system. Since they were dropping it, they just dropped it so it would be back at the factory location.

Is mounting the steering point on center with the wheel better? Maybe, but I don’t believe that Fabtech’s system adds any stress to the steering system.

 

A spacer sounds half done to me IMO. Like the Pro Comp. Heck If i'm paying all that darn money I want the full shabang.

 

to give you the country boy/farmer look hauling seed and sheet!

 

I don't mind it, I'm certainly not going to pay to level it out unless it's disturbing to sit like that. I really hate the way our rear seats sit upright, I wish they were "fixed" reclined like the Titan's (wish I could mod them to), the bulldog stance is an expensive way to achieve this

 

Since you know how to work on your own truck just purchase a larger rear block.They don't cost that much. Let me ask you this what size block came with yours?