Topic: Tire Vibration or bounce at 55 MPH

[Red Once]

My Rat has a Vibration or bounce once you get to 55 mph. It is nice and smooth up to that point. Once you hit 55 it will start bouncing or so it seems to me. If you power on through it, it will smooth out at about 65 and 70mph.

It has a straight front axle and old International spring packs on it. It only happens on the passenger tire.
I do have shocks on it too.

I took it into the tire shop and the tire was only 1 ounce out of balance.
Before I took it in to the shop, it was bouncing at 30mph.. I took it home and let some of the air out of the tire and that's when the bounce moved to 55mph.

I talked to my Dad about it, and he said that the tire could be out of round, but you would think that the bounce would always be there.
It's not like my slicks on my Drag Car, once it sits for awhile it will flat spot but they all work out once I drive it around the pits. The Rat does not do that.

So.. What do you think the problem is or do you think that there is anything I can try to make it better ?


Thanks for your help.

[lowboy]

Have you tryed different rim/tire combinations? maybe swap front to rear?

[Red Once]

Have not tried that lowboy.  The back wheels and tires are way to big.. But I may see if I can find any other tires and wheels that might work and see what they do.. Thanks for the idea.

[naessdrawos]

90 percent of the time its a tire out of balance.

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[Rubberhead]

I don't recall who, but someone else here had a similar problem recently and I think that the cause turned out to be the front axle angle.

[hotwheels]

I had that problem with mine, but it was the entire front end wobbling, not just one tire. I had to set the front end, tilted back towards the cab at 7*'s.......Once i did that, i lost what is called the death wobble. Mine would start once you hit a bump in the road and hold on, cause it was out of control. Your dad may be right if it's just one tire. You may have a broken steel belt in the tire.

[miraclepieco]

Vibrates at one speed, then disappears at other speeds: classic tire imbalance, flat-spot or runout symptoms.  If you change front tires (wheel may be bad also) it will cure the problem.

I had a set of tires that balanced fine, but they were flat-spotted from prolonged sitting. They would bounce at 20 mph, smooth out, bounce at 50, smooth out, then bounce again at 70. Go figure...

[Red Once]

Thanks again for all the information !  Looks like I have a few things I need to investigate.

[Xlarashun]

Just went through that, found out that the rim on the balanced tire had been warped/bent Earlier in its life and was just out enough to mess with Me at about 65 - 70 mph. changed it out, Presto, NO wiggle, at least from That End!  _

[miraclepieco]

Balancing does not locate or cure runout or flat-spotting.  A tire shop could actually perfectly balance a square tire.