Difficult to diagnose vibration

1998 Accord LX with 172,000 miles, 5-speed manual.

For about the last 40,000 miles, I've had a subtle vibration at around 60 mph. The funny thing about this is that it tends to go away after the car has been driven a while. I've gone through two sets of tires in a short time, however, because the tires start developing a wear pattern based on the vibration, and then it gets worse until I need to replace them.

I just dumpd over $500 into a set of tires and would like them to last. So, does anyone have any ideas what could be the cause? Here is a list of repairs that I've done with no effect on this vibration:

1. Complete front brake job, including new rotors
2. Rear drums turned
3. 4-wheel alignment
4. Had dealer check out all suspension bushings, tie-rod ends, linkages, etc -- no defects found.
5. Had dealer check wheel bearings -- no problems found.
6. Replaced tires -- multiple times
7. Balanced tires -- many, many times
8. Replaced warped wheel
9. Replaced front shocks (with OEM)

The machinist who just turned my rear drums said that sometimes it ends up being a warped hub. I asked if he knew how to test for that, but he didn't know.

I'm really perplexed by the tendency of this to go away after some driving. I have contemplated it being a slightly bad CV joint, but I get no sound out of the CVs at low speed. It seems there are two possibilities -- either the vibration is caused by something that loosens up as the suspension and tires heat up, or the vibration is caused by something rigid, and the tires absorb the vibration after they heat up and become more plyable.

I can't tell what region of the vehicle is giving rise to the vibration. It shows up as a slight vibration in the steering wheel and, very subtly, in the gas pedal. Nothing in the brake pedal. My wife says she can feel it in the seat.

I'm stumped. Any thoughts?

You need to see if you can find a certain type of factory manual, Ford calls it an NVH (noise, vibration and harshness) manual. It probably doesn't matter if it's for a Honda, as long as it is for a FWD vehicle with similar equipment.

They have very specific "flow chart" type diagnosis steps to quickly identify the type and location of the offending symptom.

Things that come to mind right away are motor mount, bent hub (like the guy said), unbalanced flywheel (if manual), out of round clutch pack drum (if auto), bent or unbalanced CV shaft.

The rear hub is easy to check, you simply measure the gap between the drum and the backing plate, and see if it changes as the wheel is rotated.

Also if the hubs are rusty around the wheel flange, it can cause the wheels/rotors/drums to not be true to the hub when tightened, causing a very slight wobble that can be felt. If rusty, wire wheel them with a drill to clean them.

If you have alloy wheels, make sure they are torqued evenly with a torque wrench, those torque sticks they use in shops don't always work right.

Last set of tires I had put on, the guy used those, and after noticing a vibe like you have, I went back over them with the torque wrench, and found them to be anywhere from 60-120 ft.lbs.

The spec on mine is 100 ft.lbs. The vibe was gone instantly.

Thanks -- that's very helpful. I have checked for rust on the hubs and everything is okay there. Also, torque on the lug bolts is where it should be.

I'll take a look for a warped rear hub. Any suggestions on how I can check whether the I have an out-of-balance driveshaft (on bent one)? The car hasn't had an accidents, so that would be wierd, but I'm kinda into the wierd scenarios now; all the usual ones have been checked.

Well, it's pretty hard to check for a very slight bend, and if you could see it, it'd probably be so bad it'd shake you to pieces. I agree if there has been no trauma, and no parts changed, that's unlikely. There is a procedure for checking balance on-car, but it's pretty time comsuming, but worth a try if you suspect it.

Basically, you put two heater hose clamps on the shaft, so the screws are opposite of each other, theoretically cancelling each other out, then drive and make sure it feels the same as before. Then you move one around slightly, to change the balance, and drive it again. If the vibe is better, you move the weight a little more that way. If you can balance it out like this, great. Just leave them where they are. Make they aren't going to hit on anything before you drive it.

If all you do is make a new vibration, that's not the problem. If you change the severity of the original vibe, you're on the right track.

Before we get to gung-ho on strange things, were you saying that you get abnormal tire wear since having the vibration? If so, which tire, what kind of pattern, and which area of the tires?

Yes, that's what I've been told, although the only way I could ever see a problem myself is if I put the front end on jack stands and run the engine in 5th gear--you could sight across the top edge of either front tire and watch it go up and down with each rotation.

Same thing could be observed after rotating the tires, so the wear was on all 4. And -- if you do the same experiment with the tires off the car, the hubs and rotors do not bounce.