Rair Lt1

Ok, long time listener first time caller here in the Tech section...
I was doing some maintenance on my 72 and noticed that I could feel a bit more "play" in the drivers side rear wheel bearing than the passenger side. The P/S has almost no noticeable play at all.
So I decided to have a closer look, first I attached a dial indicator to the control arm ahead of the bearing hub and put the dial indicator both on the center of the hub and then on the rotor like I was checking for runout (see my picture for the setup if this isnt clear). On the passenger side there was hardly any measurable movement - say less than .002" anywhere. The drivers side was a bit sloppier. When the indicator was measuring the movement "in and out" in a straight line, there was very little play, maybe .002" - .003" endplay.
However, when I grabbed the rotor at the 6 and 9 O'clock positions and "rocked" it back and forth (like I was trying to pull it off)I could get around .007" to .008" measured movement on the dial indicator positioned as shown in about the 9 O'clock position near the edge of the rotor. I looked up the spec in my FSM and it shows a range of .001" to .008" end play!
So My question is: is this OK? the rear bearings were replaced almost 20 years and 30,000 mileas ago, they arent making any noise or showing signs of problems, but I can "feel" that .007" movement when I rock the tire/wheel back and forth.
Sorry for the long winded description.
I believe it is within tolerance but the real world may be different
Thanks for any feedback!

FireballXL5

My passenger rear tire, when jacked up and with the tire on, I could grab the tire at 12 and 6 and get considerable 'play' perhaps 1/8-1/4 inch! My bearings were definitely shot! Removed trailing arms both sides, brought em to the local vette shop for bearing/seal and bushing replacement... For what it cost, I would've bought offset trailing arms that had all the work done already, plus they come with new brake hardware and rotors... My work to rebuild was almost $1,100... Offset trailing arms with no core , were $1,300... Would suggest going that route next time... Unless you are very handy, have the right specialty tools, and a proper garage/experience to do the job yourself to save some bucks...

Tom454

Tighten a couple of lug nuts onto the rotor/spindle to stabilize it during the test.

Rair Lt1

Thanks for the quick response Fireball,
I read most of your thread when I was doing a forum search on this topic. I just wanted to actually measure what I was feeling and compare that to the allowed tolerance.
If I need to, I'll probably send both trailing arms off to be rebuilt, but I would prefer not to unless necessary.

Rair Lt1

Tom454, I neglected to mention that I did have three lug nuts torqued to about 50lbs holding the rotor onto the hub. I was just getting ready to put the tire back on when I snapped this picture. I also pulled the brake pads during my measuring to prevent any contact with the rotor.

Mike Ward

Position the dial indicator on the end of the spindle, not on the rotor surface, to take the measurements.

With 30K miles, they're more less due for overhaul anyway.

Rair Lt1

Mike, that is the first measurement I took, three lug nuts holding the rotor to the spindle, brake pads out so as not to interfere with any movement, and the dial indicator on the hub center. That result was less than .003" end play. the measurement at the rotor edge was simply the maximum measurable "rock" or movement I could get out of the spindle/bearings.

I was just surprised at the difference between the passenger and drivers side.

30,000 miles between bearing services, really? that seems pretty conservative...but I'm not a Corvette expert,that's why I'm asking

Richard Cooper

Mike Ward

'Rocking' the spindle with the dial indicator on the outer edge of the rotor will give a greatly exaggerated number, not representative of true linear end play.

If you've got .003" that's fine.

The rear bearings live a miserable life. I'm surprised that they last as long as they do.

doorgunner

Mike Ward......

Rookie is wondering if one of those infrared heat detector guns would show a big difference in heat after an hour's drive on a road like the Interstate where little braking would be needed.

Would the heat difference between the passenger's side and the driver's side be a big factor in deciding if the spindle bearings were going bad or the grease was not doing it's job any more?

Mike Ward

My experience is that dry bearings go from normal temp to hot to overheated to 'hey- look somebody lost a wheel!' in a very short period of time.

doorgunner

LOL!


Thanks for the info.....rookie needs all the help he can get...that fact makes me haaaaappy that I re-packed the T/A bearings "just because".