increased tire psi to 40,now have a shake at 60mph WHY

 

What tires do you have?

 

increased tire pressure = stiffer ride

 

Is it a shake or hop ? I think I have the same problem. Mine is more like a bed bounce though. I have read other post obout this. I have the BFG's on 18" wheels. 35 psi is the max press. I went down to 30 psi to see if it would help amd it doesnt. My bed bounce's after going over a small bump in the road or a road joint. On a very smooth black top, it is silkly smooth. I normally drive around town at 45 (speed limit). Thats where I notice it mostly.

 

My bed bounces a bit on rough roads or going over bumps but I thought this was normal since the whole truck bounces.

 

I too had the pronounced bed shake or whatever name you want to give it. While I know this is a relatively expensive solution, but if you were thinking about getting a spray-in bedliner and were just waiting for a good excuse to do so, I think this is it. I had mine sprayed a week ago now and I can see a huge reduction in the amount of bed shake I have. Will this work for everyone? I don't know but it sure did with me.

 

Got any aftermarket exhaust on you truck? This was causing a hella shake in my bed...

 

Your bed might shake like that because of the stiffer frame. I dunno. Just guessing.

 

here we go again. Truck beds shake. Your truck bed shakes because the frame shakes. The cab is isolated from the frame, while the bed is solidly bolted to the frame. The cab and everything attached to it (your butt, your mirrors, etc. are moving at different rates than the bed and frame.
The comfortable ride you get driving for several hours? well, your bed doesn't have that luxury. It's a truck. They do this. exactly what damage does it do?

 

I have a spray in liner and mine still shakes. It's not real bad though. The other trucks I've driven over the same raods didnt shake like this. It's a strange kinda bounce. Other trucks go over the bump and it sounds like "BAM" and it's over. My F-150 goes over the bump and sounds like "Thump, Thump, Thump". Yeah, sounds korny, but dont know how to explain it. I think it has something to do with the stiff frame and leaf springs. Maybe a stiffer shock will help. My bed bounce is not to where I'm too concerned yet. In SC, we have mostly very smooth roads.

 

Wanna see something cool? Drive mine after it sits for a day or two. You'll think the bed is alive like one of those lowrider trucks with hydraulics. But it stops after a few miles worth of driving, after the tires get warmed up I guess. I'm not too terribly picky, so I'll file that one under uneven tailgate straps, I ain't gonna worry about it unless the bed flies off the truck while I'm going down the road.

Edited to add: And higher tire pressures exaggerate any imperfections in the road.

 

another thing to consider on the shake is how much deeper our beds are. With an extra 6 inches or so of sidewall height, the top of the bed will move more distance with the same degree of angular movement. Also, the extra height puts the top of the bed right in the middle of our line of sight as we look into the mirrors. Both these facts stand to reason why the shake is so much more noticeable than other trucks...

Also, our cabs are much better isolated from the bouncing frame.

 

I told my service manager about the bed shake and mentioned that some people who had the vibration damper put on noticed that it reduced the bed shake. I asked him if they would put a damper on my truck and he said sure, that they had them in stock. When I drove the truck home this evening from the dealership, the bed shake was almost completely gone! The damper also reduced the vibration felt just after hitting a bump(almost like an echo or reflection of the bump). I am pleased with the result. Keep in mind that these are completely subjective observations, your mileage may vary.

 

my regular cab FX4 acts like the bed is bolted on with Jello bushings. It jiggles like crazy. I'm probably only getting 1/2" or so movement at the top of the bed rails. I took it to the dealer about this because I thought this is also why it rattles so loud sometimes. The dealer claimed he had the mechanic put the truck on a lift and check the bed bolts. All were too tight to move. So, if the bed is bolted on tight, must just be the the way it's supposed to be

 

again, your bed is bolted solid to the frame. It is your CAB that is on Jello Bushings. That's why the ride is so nice and soft. The more you isolate the cab from the frame, the more comfortable things will be. Everything that is attached to the cab (your butt, the mirrors, etc) is moving at a different rate than the rest of the truck. This is why it looks like the bed is shaking. Have someone else drive your truck on a bumpy road while you are sitting in the bed, and you will think that the cab is shaking out of control. If you want to reduce the cab isolation, you will see less 'bed shake', but you will have a stiffer ride. Stop worrying about it and enjoy the comfort.