Pan Hard Bar

[azblazer]

It won't fix bumpsteer but fixing body roll might make a bigger difference, we have a bar just for that now. We purposely stay away from panhard bars and leaf springs because they force the axle to move side to side a lot more than most think. They get really hard on frame brackets and bushings. it's not a hard and fast rule but lower lift longer travel leaves are where a lot of problems pop up. A 40" bar that moves 10" vertical sweeps side to side about 1.25" and can be worse depending on ride height. Making your leaves match that without binding is a pretty tall order.

It actually did stop the tendency to want to dip to the right when braking and hitting non sooth surfaces in the road. The custom rear sway bar so far has made the most difference. I am going to see if that bar bracket is in the way of the bolt for the sway bar. I am dead certain that new sway bar of yours is going to be the final cure for road manners.

 

[Stephen]

The right pull on hard braking is crossover bumpsteer, plain and simple. As the suspension compresses the knuckle gets closer to the steering box and the draglink doesn't compress so either the steering wheel turns or the tires turn. Panhard bars fix that but at what expense?

I hate the fact that all of this keeps leading right to the need for links and round springs but that's the end game. You can control all the movements in the way you want when you separate the spring from axle location duties. And just for the record, even link systems have limits. They're farther out on the performance scale (unless stuff is just wrong with the link layout) but there are limits there too.

 

[JT88K5]

I am looking hard at trying one of your new sway bars. I think the primary issue with steering and no sway bar is due to the inability to keep the steering wheel from moving when the vehicle sways. Dips seem to be worse than bumps, dips during a turn on a narrow road at 50 make me pucker some times.

 

[sweetk30]

I am looking hard at trying one of your new sway bars. I think the primary issue with steering and no sway bar is due to the inability to keep the steering wheel from moving when the vehicle sways. Dips seem to be worse than bumps, dips during a turn on a narrow road at 50 make me pucker some times.

tag @Stephen in on this or better yet call him and ask . he has the info !

then let us know what he said if he dont chime in here .

 

[JT88K5]

Thanks @sweetk30 , I’m not sure that post came across like I meant it. I wasn’t trying to say the steering moves on it’s own or due to the road. More like when the k5 sways, I sway, and I can’t stop from turning the wheel my own self.

 

[sweetk30]

sounds to me like a sway bar will help as its the bars job to fix this i would think .

 

[Stephen]

Lots of things happen during body roll and I hadn't thought about the driver's body actually moving around but I can see that being a thing too!

One factor we think of that isn't super obvious is that there are axle steering effects that happen during one wheel bump (articulation or body roll) and leaf springs are generally pretty forgiving (compared to a link suspension, they need to be "righter" than a leaf) but anytime stuff changes it can feel unsettling. As the springs on the outside of the corner flatten, both axles steer to the outside of the corner, likely at different rates so you can get some weird wiggles going. Hence a swaybar, you get less change in suspension placement compared to the frame and body so less of that suspension geometry change making things move around in addition to just feeling better because the truck stays flatter.

Crossover steering is generally really good about roll steer which is where the steering linkage induces steering wheel movement in articulation or body roll. This is why we do crossover, it's really good at keeping things consistent in body roll and OK in pure bump. But I think there can be some roll steer effects if the suspension's roll center changes and doesn't match the steering. And again a really good way to fix it is to just limit body roll with a swaybar.

All this geek speak means there can be a lot of problems you didn't know you had that are solved with a swaybar. And in most leaf trucks, you can't really change the causes of the problems to try to make the root cause any better anyway.

And to talk about bumps and dips in corners, we ran into some CRAZY paved road bumps and dips on the drive through Canada to Alaska for the UA trip last summer. Their frost heave is no joke. There was one that made me really glad we have a fairly predictable truck with 2.5" shocks on it and that I apparently have more work to be done on this side of the grave. I saw the whoops coming in a blind corner so I couldn't use more road than just my lane so I steered where I wanted to go, held the wheel steady and counted on the truck to keep the rodeo going where it was supposed to. Turns out it worked but I checked up a little after that one!