I have an automatic 2005 Kia Rio with 65000 miles on it. The car has started handling extremely rough. The steering wheel shudders constantly unless I’m at a complete stop. It is much worse at 50-65 mph, but is noticeable at all speeds. It is virtually undrivable at speeds over 65 mph. Accelerating or braking doesn’t appear to make the problem any better or worse. I can feel the shudder through the gas pedal, as well.
I had a local shop look at it, but they said the couldn’t find anything wrong. I had them rotate and balance the tires anyway, but it didn’t help.
I appreciate any suggestions. I’m really afraid to drive it much more until the problem is fixed.
There are many possibilities, bad tires, bent rims, bad alignment, struts, tie rods, motor mounts, you need to try a garage that can properly diagnose and fix the problem. It is hard to pinpoint it without seeing it. Are they the original tires? any unusual wear patterns?
The technician at the shop said the tires look fine, no signs of unusual wear. I bought the car used at 45000 miles with the same tires that are on it now. They still have a fair amount of tread left, so I’m assuming they aren’t the originals.
Here’s the really strange part: there is a stretch of highway (about 1/5th of a mile long, no curves or hills) on my daily commute where the shudder almost (but not quite) stops. As soon as I pass that stretch of road, the shudder returns. This happens every day without fail, both going and coming from work.
I had thought about bad motor mounts, but the engine doesn’t shake on start up or when I shift into drive or reverse.
I took the car to another shop. Turns out the front passenger-side tire had a bad spot on the inside wall. I had both front tires replaced, and the car drives smooth now (well, as smooth as a Kia Rio gets, anyway). This makes me wonder exactly what the first shop really did when I left it with them, since they supposedly rotated my tires 
Thank you for the follow up post. We so rarely get them.
Happy motoring.