Wheel balance issue

Patient 2005 Subaru Legacy GT turbo, with the bigger oem brakes. Automatic.

Up hear in the northeast, I have snow tires on aftermarket rims. It's not uncommon to have dirt pile up in the rims, especially after cleaning the car, causing a wheel balance issue. I appeared to have this problem. No problem lets just toss on the oem rims with summer tires. Rims are clear of dirt, and all weights present. Still get a severe shake randomly at about 50-60mph. Easily felt through the steering wheel. Car is new to me this year, and spent exactly 50 miles on the summer rim/tire set. I don't remember any issues with balance. So I clean out the winter rims/tires. All weights are present. I put one on the right front, take for a test drive. Shake is still there. Replace the left front, shake is still there. Shake persist with either set of tires. I live on a hill. Have to drive up it on the return home from test drive, brakes really don't get used. I notice right side front brake is quite hot compared to the left.

Possible the rotor is warped? I always thought that was an urban legend, and that rotors didn't warp, but the braking surface would get pad build up. My only thought is that is the wheel mating surface is warped or not flat, causing the wheel to wobble. Rotors are old.

I had a similar issue with a car of mine. It turned out to be build up on the hub where the wheel mounted. I used a wire wheel on a drill to clean up the hub and the wheel and no more shake.

Is the Passenger side inner CV boot their? Rear main seal leaks tend to soften the rubber and off comes the boot. that joint only deals with up and down movement so play it it seems to just cause shake not the Click of most CV shafts. A new $80 CV shaft curried the wifes Forester after i got tired of dealingwith the shake

you could have crap behind the rotor making it seem warped, when changing the wheels the crud could move.

If the winter wheels use centering rings, make certain one did not stick to the hub. I had it happen when I changed my dad's wheels on his G37 in March. It shook at 65-70 mph.

No centering rings....I have had that happen too.

Cv shaft maybe.

Rotors do warp. Putting them on a brake lathe easily proves that. That being said, most of the time shimmy under braking is from uneven distribution of friction material on the rotor.

If your caliper is dragging slightly on one wheel it will cause the uneven spread of material AND cause a shimmy every time it "catches" that spot while dragging. If the rotor is still serviceable, it's worth the $15-$20 per rotor to have them machined for a fresh start. I would definitely spend time confirming that the caliper is dragging though.

A loose wheel bearing can cause all the same symptoms too (shimmy and brake dragging).

Dear GRM: I never believed that this could happen to me, but...

I have a perpetual problem with mystery vibrations in my Mazda. Turns out that one of the sources was slightly loose ball joints. Now, I know that something loose doesn't mean it will shake. Can't happen. The force has to come from somewhere.

Replaced the ball joints - shake gone.

Near as I can figure, my camber and toe are in just the right range where the wheel moves one way due to camber, then bounces off/changes force due to toe. It was bizarre in the way it would happen sometimes but not all the time.

Wheel bearing doesn't seem likely, I when I had each corner up, and no apparent play in the wheel.

I'm leaning towards CV being a contributing cause, however my rotors are due for a change anyway. Reason being is that the calipers seem to move fine. I think I get a little bind in reverse on tight turns that I only now notice after 44 dwarf mentioned it, and I test drove again.

It's raining, and I don't have a garage.....and I really don't want to deal with this today, cause I'm a weenie.

Oh these front rotors were on the car when i bought it. Cross drilled and slotted which I've had a bad experience with before, hence why I intend to change them anyway.

I diagnosed an S8 random strange vibration when I worked at Subaru (we got all kinds of random cars coming in because they decided to not pay us anything and give away work so they could get customers)
It turned out to be cradle bushings and a rear lower motor mount
at first it was thought to just be a wheel balance issue, but it turned out it was only when on throttle above 30mph, let off and there was no shake.
So this I ask you: is it throttle dependent or does it do it when you are cruising with no throttle also?

Low to no throttle. 50-60mph, in fifth gear, so very little throttle. Lower speeds, you can notice just a little shake if you are looking for it.

wow I thought I had you.
only suggestion I've got is get a dial indicator base on the spindle and turn the rotor really slowly with the indicator measuring runout, or warpage.
I haven't ever seen a shake that isn't tie rod ends or wheel balance, other than the one strange volvo i mentioned.
I did both front wheel bearings and an inner & outer tie rod on a caddy that had a shake at anything over 30mph, but that was just my luck of the draw at work. lol
but if it was a tie rod or a wb or a ball joint there would almost def be play. esp if it's a very noticeable shake.

Check your tire for being out of round. Broken belts in the tread could be your problem.