I was thinking about swapping to a solid axle in my 83 F350 for better tire life, I just put the summer tires on, they have very low miles on them and the left front is about half gone on the outside edge. I knew these TTB's were bad on tires but wow maybe 4000 miles on the tires.

First thought was to just get rid of the TTB but after looking over the geometry last night and thinking about it over night I'm thinking maybe the easier fix is to change the steering geometry. I'll just copy over the posts from the original thread.

 

 

Everyone loves to hate on the IFS, but is it really that bad? Other than getting them aligned I'm pretty happy with it. My 85 f150 has one with a well built 300-6, 4 inch lift, 35 inch bfgs, and an aussie autolocker in the stock dana 44 carrier. Iv'e been driving it hard like this for a year and half now and haven't had any issues with it (it still has the junkyard wheel bearings). I just installed a new set of 35inch bfgs because I wore through my last set completely and they wore almost perfectly even.

Being yours is an f350 you probably have a stronger dana 50. Unless you have some serious torque under the hood or have massive tires I doubt you'd break the axle. I think spending a fortune on a solid axle, the parts to install it and the labor to do it all because of an alignment issue isn't worth it. See if a shop can align it (remind them of the next paragraph) or see if you can buy the adjusters and do it yourself.

Remember when these are aligned do not reverse, spin the steering, lift the truck etc. Just drive it straight forward, stop and take the measurements. If the truck needs re positioning back it way up and go straight forward again before parking. These suspensions do weird things you want the measurements taken as if you were driving it straight down the road.

Other than the tires wearing funny it sounds like something is worn out maybe. Check your ball joints, tie rod ends etc for play. Look for bad radius arm bushings... Mine with a 4 inch lift has nothing more than a dropped pitman arm with stock replacement tie rods, that's it, no stabilizers or anything else and it steers great.

 

Not hating on the IFS as a whole, just the steering, all my parts feel tight and it was aligned when I put the tires on it. The problem is in the designed in bump steer. With the tie rod on the left side being half the length of the swing arm there is no way to align it at anything other than the ride height it's sitting at when it's aligned. any change in ride height changes the toe, and on this design it will change it drastically. So if you load the truck you toe in and grind up the tires, if your truck never has a load in it it might be alright but my truck rarely runs empty and has a plow on the front in the winter so when I pick up the plow it toes in when I set it down it goes back etc. etc. its just a bad design.

Not thinking about breaking axles this is a on road truck and plow in the winter. Yea the swap would be overkill which is why I'm thinking about rebuilding the steering to correct the geometry so the wheels stay closer to parallel when if moves through it's travel. It has a 6.9 IDI under the hood.

Interesting and backs up my thinking, "These suspensions do weird things" is why they wear tires and have the bad rep. Changing the steering geometry should fix that for about the price of a couple tires.

There might be something worn in there but nothing moves using a pry bar from underneath, that is on the list for this summer to check it all out. I just think that a little work could make a big difference in how the steering works. and wondering if anyone has done this on theirs.

After a bunch more searching I've found several different ideas to help the BS issue, mostly on lifted trucks so I just need to do it for a stock height truck.

 

The factory steering geometry is as good as it gets. As long as the steering arm passes through the same point in space as the ttb pivot, then it's ok. Plus it is so long, that bumpsteer while still there, will not be noticeable. If you put another idler in there with short arms going down to the tie rods, you will have trouble then.

They do the same thing on the factory dana 60 steering setup. They go from the steering box on the driver's side, all the way over to the pass side spindle. While this arm does not jive with any pivot point(the axle goes somewhat straight up and down on the leaf springs) having the arm so long puts a lot of forgiveness in the design. The swing arc of the long arm is so large that bumpsteer is minimal.

 

Correct on the right side, the problem as I see it is on the left side where the tie rod is about half the length of the swing arm, that's where the bump steer comes in, and by the way only the left front tire has the bad wear, the right front shows uneven wear but not as bad. if you look at the pic above the idler allows the left tie rod to be as long as the swing arm and that should reduce the bump steer. When I get a chance I'll get out the bump steer gauges and run it through the travel range and see what it measures. And on the Dana 60 you have a solid tie rod from wheel to wheel and the drag link only moves it back and forth so any bump steer is a touch of right to left but as you stated very minimal because of the long length of the drag link. The TTB however the bump steer is toe in toe out not right to left much harder on the tires.

 

I will be curious to see what you get with your gauges. Most cars and trucks have a little bit, some more than others.

I get the impression bumpsteer affects driving feel more than tire wear though. You need to have a lot of travel in the steering system to even get any bumpsteer, and unless you drive on a very bumpy road all the time, I would think the suspension would not be moving very much a large percentage of the time on normal roads.

 

You aren't looking at the whole system. The inside end of the left tie rod is pretty much right where the two traction beams cross. That's where you want it to prevent bump steer. If it was farther to the right as you are asking for, then as the passenger side tire came down it would push the driver's side out. That would give you bump steer. Stock there really isn't any.

What does get messed up as the tires move up and down is camber. There's no getting around that, and if you change the load on your front end a lot you can get more tire wear. But other than hanging a plow on, the load on the front axle usually doesn't change all that much, so even that usually isn't a problem.

And the "these suspensions do weird things" was specifically speaking to making sure you pull straight forward and have full weight on the tires when aligning it. If you try to align it after backing up, or with the tires hanging, or after setting it back down you won't get the same thing when you are driving forward. So sure it does weird things when backing up or when the truck is on a lift. But so what? What does it matter if the alignment is a little wonky when you back up or are on a lift?

The TTB isn't a great system, but it's nowhere near as bad as it's often made out to be. I got 50K miles each on 3 sets of tires on my '85 F-250, with about 40% of the tread left on the 4th set with 30K on them. They all wore evenly. I moved tires around a little too much on my '95 F-150 to know how many miles any particular set had. But they certainly didn't seem to wear out fast and again, they all wore evenly. And now I have 20K miles on the tires on my '97 F-250. They are also wearing evenly and have a lot of tread left.

If your truck ate a tire in only 4K miles, that's something that can be fixed by aligning, balancing or replacing worn components, not by screwing up the steering geometry.

 

I can't find my bump gauges, I'll have to build another set. normally I pull the springs to check bump through the travel but that's going to be a bit tough with leaf's, have to figure out how to compress the suspension to measure the compression side of the curve, the rebound side is easy.

Feel and stability both, Most of my driving is on rough back roads, almost never sees any highway miles. I need to check out the front end myself and see whats going on not rely on someone else. the place that aligned it supposedly knew these front ends, I took it to them because it had tire wear on it when I bought it, they said it was all good and tight and didn't need an alignment as it was all in spec.

 

 

You're right, I was looking at it as 2 separate tie rods so that does make it better. I'll get it in the shop and measure things out instead of looking at pictures with the combined affects in mind, I still don't think it's optimal but I'll keep an open mind until I measure the bump steer.
When I was talking about the pivot point being further to the right that was with an idler arm and a cross link and both tie rods would be independent with that setup and would be equal length and parallel to to the swing arm.

True but camber isn't nearly as bad on tire wear as toe is. The load on the front end may not change much but if the steering worked the way I originally pictured it it would have been enough. LOL

Most suspensions are a bit wonky when backing up but should settle out when on the bearing plates, I'm still having trouble understanding how the direction it's rolled onto the bearing plate would make a difference, once it hits the free floating plate it should settle out.

That sounds promising I'll see if I can find something wrong in mine.

Don't worry I wasn't going to screw it up, it would have been modeled in cad and proven before any modifications were made. Thanks for pointing out the error in my thinking.

 

You have a good point there, that's why I don't normally hire anything done but I farmed this out because I didn't want to work on it.... I know better. most of my test gear is way to light for this thing, the front end weighs more than any of the cars I work on...lol

 

I think you should be able to see any camber issues by eye. Drive it down the road and stop and carefully eyeball it. Mine wears 35inch tires very slightly uneven and I can see it. Toe angle will amplify the wear.

If it goes to a shop for alignment I would stress directly to the mechanic that it be driven forward, stopped, and measured. Mine goes so wonky when backed up the guy at kaltire a few days ago thought I was coming in for an alignment from what he saw from the counter as I parked.... It handles great and is on good alignment going forward though.

 

That linkage thing you showed a picture of looks like it could work. But it's a lot more complicated than the factory setup, and the factory setup is pretty good. I could imagine the linkage being better in extreme travel situations (like with one tire stuffed and the other drooped). But it seems completely unnecessary for most use.

With toe in, as the vehicle rolls forward the tires try to squeeze closer together. With TTB, they can move closer together if they also droop. So pulling forward tends to extend the suspension.

Conversely, when backing up toe in makes the tires try to spread further apart, which the TTB allows if they also move up.

Obviously if there's no load from pulling forward or backing up, then the tires won't be trying to move in or out, so they'll also be in a more neutral position up and down as well.

Since you will primarily be using the alignment when driving forward, you want the alignment to be correct when the suspension is being pulled down, not when neutral or being pushed up.

 

Putting the vehicle up in the air and letting the suspension hang is not the proper way to check for wear in the suspension. That takes almost every joint out of it's normal everyday position. The proper way is to support the suspension right underneath the lower balljoint, just enough so the tire is off the ground just a little bit.