Post Lift Caster Question (bump steer) - Ford Powerstroke Diesel Forum
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post #1 of 9 Old 07-25-2016, 05:07 AM Thread Starter
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Post Lift Caster Question (bump steer)

I've searched through a bunch of posts but can't seem to find what I'm looking for. I just installed a Carli 4.5 lift, and now I am fighting significant bump steer and a little bit of wobble on a couple of sections of road. It's not full blown death wobble, though I did have that at first until I went back through everything to make sure it was all tight. I had the truck aligned, and the caster was set to 3.7 and 3.9 without using the 1deg sleeves that came with the Carli equip. I've seen a couple of references to using 4deg as the target. Since I know everything is torqued properly and the geometry of drag link vs track bar has not changed, it would seem to me that I would benefit from more caster. My question is how much? Anyone on here run 4.5 or 5 on the castor? I have the 1deg sleeves from Carli, which would put me at 4.7 and 4.9. Is that too much??
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post #2 of 9 Old 07-26-2016, 03:21 PM
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Nothing wrong with about 4.5 degrees of caster. You should ask the carli guys what they think. But I don't think the caster is the reason you have death wobble and bump steer.

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post #3 of 9 Old 07-26-2016, 07:32 PM Thread Starter
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Appreciate the reply. I checked with them right away after my alignment, and they said close to 4 should be fine. I went back through everything and found two items that I think were the cause of my woes. #1 The tie rod end at the axle was out of alignment. When I reclocked the steering wheel and tightened down the sleeve on the drag link, I didn't pay attention to the orientation of the rod end. It was rotated all the way forward. #2 was very similar in that the axle end of the new track bar was rotated as far as possible toward the axle and the frame side of the track bar was rotated all the way toward the front of the truck. I'm guessing it was causing a bind on the track bar when moving with the bumps in the road. I straightened both of those out and the ride is 100% better.

I've been in and out from underneath the truck so much the list week, I guess it was a classic case of not seeing the forest for the trees.
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post #4 of 9 Old 07-29-2016, 04:23 PM
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When you speak of bump steer. If you hit a bump the truck turns? Or does the wheel move a little but the truck stay straight?

Post some pictures of your set up. What tires are you running? Size and load range?

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post #5 of 9 Old 08-02-2016, 02:42 PM Thread Starter
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Sorry for the delayed response, but I was on a road trip. I drove the truck from Dallas to Houston and back and have a better feel for things.
I thought I had it straightened out, but unfortunately I'm still fighting the bump steer. When I hit a bump or a dip in the road, the wheel turns left or right. I have no wobble, that I'm sure of. I did when I first installed, but that was self inflicted and was soon corrected. I also realize that some bump steer is to be expected, but I think mine is a bit excessive. Trying to figure out what to try next.

I fully understand the cause based on geometry, so I've crawled under and measured everything to figure out what's off. The drag link measures at about a 6.6deg angle and the track bar is at 15.3deg. The track bar has a dro pin height of 10" over the 38" length, and the drag bar has a drop of 4" over a 38" measured length. So, there is a significant difference, with the track bar being at a steeper angle. I'm tempted to try a drop bracket since they are bolt on replacements for the stock bracket and I can always go back to stock ifit makes it worse.

I'm running some BFG 35x12.50x20. I will be changing wheels and tires in a few weeks. Unfortunately, no pics yet...
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post #6 of 9 Old 08-02-2016, 03:23 PM
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What all came with this kit?

As far as your geometry goes, go look at a stock truck and nothing is parallel and same length. You got to kind of get that out of your head and I go round and round with guys on here about that.
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post #7 of 9 Old 08-03-2016, 08:24 AM
 
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Quote:
Originally Posted by charbaugh View Post
Sorry for the delayed response, but I was on a road trip. I drove the truck from Dallas to Houston and back and have a better feel for things.
I thought I had it straightened out, but unfortunately I'm still fighting the bump steer. When I hit a bump or a dip in the road, the wheel turns left or right. I have no wobble, that I'm sure of. I did when I first installed, but that was self inflicted and was soon corrected. I also realize that some bump steer is to be expected, but I think mine is a bit excessive. Trying to figure out what to try next.

I fully understand the cause based on geometry, so I've crawled under and measured everything to figure out what's off. The drag link measures at about a 6.6deg angle and the track bar is at 15.3deg. The track bar has a dro pin height of 10" over the 38" length, and the drag bar has a drop of 4" over a 38" measured length. So, there is a significant difference, with the track bar being at a steeper angle. I'm tempted to try a drop bracket since they are bolt on replacements for the stock bracket and I can always go back to stock ifit makes it worse.

I'm running some BFG 35x12.50x20. I will be changing wheels and tires in a few weeks. Unfortunately, no pics yet...
Like Layson said,

There's more to it than a couple of simple measurements. Assuming that you installed the 4.5" Carli system as supplied and started with a stock truck, your track bar to drag link relationship will be about the same as stock. Both angles will have increased with the lift but at pretty much equal amounts. Based on Fords design, this relationship isn't perfect on paper but works fine for most situations. As you increase the lift height the small difference in the stock design becomes a little more apparent especially with increased suspension travel but generally not very noticeable if everything else is in spec.

How many miles are on your BFG's? I've battled quite a few handling and steering issues over the years that were exaggerated by tire issues. BFG's have been the cause in more than a handful of cases.

Also what are you running for wheel specs and a steering stabilizer?


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post #8 of 9 Old 08-03-2016, 01:24 PM Thread Starter
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Appreciate the guidance.

The BFG's are at the end of their life. I don't know the mileage on them, because they were on the truck when I bought it last year. I've put about 18K on them. But, I can tell you there isn't much tread left, and there is some uneven wear, though not major. Rims are stock 20". Both the rims and tires are up for replacement later this month or early next. I haven't decided on the tire yet, but will be moving to a 17" rim and 37" tires. Stabilizer is stock. So, would I be better off leaving it alone until the tire/wheel change? Maybe just a stabilizer between now and then?

Before installing the Carli, the truck had a 2" Revtek kit on it from the previous owner. Track bar and steering components were stock.
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post #9 of 9 Old 08-04-2016, 01:37 PM
 
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Quote:
Originally Posted by charbaugh View Post
Appreciate the guidance.

The BFG's are at the end of their life. I don't know the mileage on them, because they were on the truck when I bought it last year. I've put about 18K on them. But, I can tell you there isn't much tread left, and there is some uneven wear, though not major. Rims are stock 20". Both the rims and tires are up for replacement later this month or early next. I haven't decided on the tire yet, but will be moving to a 17" rim and 37" tires. Stabilizer is stock. So, would I be better off leaving it alone until the tire/wheel change? Maybe just a stabilizer between now and then?

Before installing the Carli, the truck had a 2" Revtek kit on it from the previous owner. Track bar and steering components were stock.
I would toss a better stabilizer on it like the Carli High Mount. The factory stabilizer on these trucks is tiny and it has a hard time controlling tires much bigger than stock.

If your truck is getting to the point that you are bordering on death wobble I would do the tires ASAP. Every time the truck experiences DW it puts a lot of stress and wear on all of the steering components not to mention the driver and passengers.


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