Shimmy, hop, bounce?

[CommrclDiver]

Ok I just replaced the bushings in my '71 F-100 with poly and it feels great but at around 35-40 mph it starts to Shimmy or hop or bounce. It feels kinda like your riding in a Heavy Duty truck like a wrecker or something like that. After about 40 mph it stops but it starts to do it again around 70 and this time a little more violent. I'm thinking that the tires are out of round because of sitting for 3 years. Anything else I should keep my eye out for? I am going to take it this morning to get the tires balanced.

[Mancar1]

Let us know how it does after the balance. Sitting for 3 years, outdoors? How old are the tires? Often even with a lot of tread left tires should be replaced.

[CommrclDiver]

It was stored inside a garage. The tires look great. No checking or anything. I'll keep yall informed.

[CommrclDiver]

Well the balance helped a little bit but I believe the hop is there because there is no bed on it right now. I am in the process of building a stake side. When that goes on I'm sure it will even out the weight balance issue.

[fordman]

poly will give you a harder ride than the original rubber bushings. i am not sure what else to say about a shimmy hop or bounce. where is this coming from the front or the rear? i assumed the front a few days ago when i first read this. but now you are saying the bed if off so that gives me a clue that it could be coming from the rear end. please clarify so maybe help can be had.

[CommrclDiver]

Can't quite tell. The whole truck does it. Moving forward on the stakeside today though. Hopefully it's a weight thing.