135 bounces per minute on the highway

[K10-Kansas]

Originally Posted by LONGHAIR

A bounced like that is normally a tire issue, either very out of balance or a big ol knot, from a broken belt.
Balance problems start showing up around 45mph, but it depends on the diameter.

That ended up being the exact problem. I jacked up the truck, spun the tires and sure enough they weren't round.

So I took a bed frame, cut it up and welded it together with 2 sets of drawer slides and strapped a grinder to it. I put the truck on stands and ran it in 4 low lock and trued the tires. Worked perfect. I drove on the highway today and the bounce is gone!

Here is a video of it running https://youtu.be/m-gSHW6Vx88

[MS66]

Originally Posted by K10-Kansas

That ended up being the exact problem. I jacked up the truck, spun the tires and sure enough they weren't round.

So I took a bed frame, cut it up and welded it together with 2 sets of drawer slides and strapped a grinder to it. I put the truck on stands and ran it in 4 low lock and trued the tires. Worked perfect. I drove on the highway today and the bounce is gone!

Here is a video of it running https://youtu.be/m-gSHW6Vx88

I came in here to say this. I bought brand new Cooper tires a couple years ago with huge anticipation of a silky smooth ride in my '68 only to have basketballs dribbling down the road. Had me stumped for a minute. Got home, jacked the truck up and spun the tires, they weren't round. I ended up putting different tires on it.
Years ago retread tires were super popular. When pop bought retreads, they had a tire truing machine that cut the "egg" out of them after they were mounted on the wheel. I remember the mountains of rubber laying in there from cutting tires all day long.

Did you happen to measure how much run out they had before you began cutting on them?