JAB

Hi: 1999 RX300, 255K, original owner. Last year my RX began to vibrate while in motion (without braking). My independent mechanic suggested that my front calipers needed to be replaced, and my tires were quite old, despite sufficient tread. I recently replaced the tires and wheels with a used set in good condition, but that did not fix my problem. Any suggestions? I haven't yet replaced the calipers but don't believe they could be the cause of my problem. My struts, mounts, and sway bar end links and bushings have less than 100K on them. All ball joints and control arm bushings are original. CV joint perhaps? How do I make that diagnosis? TIA.

maxSteel

I would usually associate non-braking rolling shimmy with tire wear, tire pressure, wheel balance, steering linkage, or alignment.
Did the old tires show uneven wear?

Never heard of CV joints causing it.

salimshah

Jab:

What was done or happened before the vibration started.

Can you relate the vibration to spin of the wheel?

Any change as you move the wheels from left to right, front to back.

Salim

SVRX300

Does the vibration happen at any speed, or a particular speed?

JAB

Thanks folks for your responses. The problem is definitely not caused by tire wear, pressure, or balance, as I have eliminated those possible explanations by installing a completely different set of tires and wheels, with the same grumbling thumping speed-dependent result. Previous tires did not show any abnormal wear. Nothing happened such as a bad pothole, problem simply got progressively worse this year. I thought the newish set of wheels/tires would fix the problem, but after a few miles the problem returned so forcefully that I pulled off the road thinking that I had a flat tire. At this point I'm thinking tie rod, ball joint, front control arm bushing, or CV joint. But truly, I'm stumped.

maxSteel

It seems odd the previous tires would have no abnormal wear if they were shimmying.
Do you actually feel it or just hear it? Is it just something rubbing?

You can check the CV joints by jacking up the car and feeling for play.

JAB

It is a rotational thumping that you can both hear and feel.

salimshah

Since it is rational 'thump' then I aa 95% sure it is the tire. One or more. I would start swapping tires and even bring the spare in the loop.

I have always steered clear of used tires and their market value is due to relative good appearance but there may be a hidden (visibly) defect.

Salim

JAB

Salim: Ordinarily I would completely agree, but here I have simply removed that issue from the list of possible explanations by replacing all four wheels/tires with a used set of unblemished wheels with tires that have 95% of their tread remaining; problem persists unchanged. For further insight, I might also add that my RX is AWD and my sense is that this problem is with the front end.

salimshah

To clarify: I am not sure if the newer/currently_installed tires are good.
Suspension issue come evident when you have a change in direction [side to side and even up and down]. the rational issues can seem enhanced if the suspension has a play, but once again the root cause is the rational issue. I have been wrong many times and I could be wrong here too. I would suggest borrow tires if some can lend them to you.

Salim

JAB

After a thorough examination I have concluded that the passenger side front control arm bushing is shot. I will order replacement arms (I don't have the equipment to press old ones out and new ones in) and will report back. Many helpful DIY on this subject.