vibration--still can't find it

[sbmackie]

More data: came back from reputable tech with SSI's and an M and K two into one. Sweet. More on that in another post.

They inspected the entire front suspension and found nothing. Lubricated zercs fitted poly bronze bushings. They found and repaired a spring issue in the ebrake.

Today, 40 degree morning, driving to Birmingham for some nuclear family Christmas time (Mom is 86..Woohoo!) Took the back roads to I-20. I get all the way into Alabama before...you guessed it...droning and shaking commences. 25-30 miles later, all is well. Continues that way to destination. Car sits and cools for 4 hours. Depart for the home 'drome, temps now 65. After 10 minutes (pulling onto I-20 from I-459) presto, here we go again. 30 miles later at highway speeds (65-80) it stops. Smooth as glass at up to 90 and down to zero after.

As a reminder, discs/pads/calipers new or rebuilt, bearings under 10K and greased not wobbly.

I'm starting to think I've got a bad tire. I have tracked and autocrossed these tires. They are two and a half years old and have been in on the car as it sat in an unheated garage with temps occasionally below freezing.

Wouldn't a bent rim ALWAYS vibrate, and not go away? Wouldn't an alignment problem ALWAYS manifest itself?

AAARRRRGGHHH!

[jason2guy]

It's the tires. I went thru the same thing twice. Just as a side note, I've heard that alignment issues won't cause vibration. Well they will on a 911. My rear toe was out by a tad and it was annoying.

[Joe Bob]

Originally Posted by wayner

I had a similar problem with my truck. It turned out that although the services front callipers worked perfectly, the pistons of bores were beyond tolerance and the piston would be allowed to cock slightly sideways in the bore causing it to vibrate and moan when off the brakes and shimmy when on the brakes.

Just a thought.

AX is like masturbation.....why would you use race wheels at an AX?

[dshepp806]

Tires.


Doyle

[sbmackie]

OK, a few weeks ago I swapped the rear wheels with some donor's drove car, seemed to fix. So we just put new Bridgestone Potenza R-11a on the car, high speed balanced. On drive home...drone and vibration develops. AAAARRGGHHHH!

The three and half year old heat cycled out Direzza's needed replacing anyway, so that's OK.

This leaves alignment (the car tracks well and brakes straight and isn't twitchy), rear calipers (they release fine), half shafts, front and rear wheel bearing replace (fronts were done less then 10k ago and all are adjusted properly) and half shafts/axles, which co-incidentally were replaced by a shop that did shonky work a few months before this problem presented itself.

Any other ideas? This is getting time con$uming.

[kbruz]

Have you checked the shocks. I would think that this would occur all of the time and not intermittent.

[rattlsnak]

When its happening have you tried to turn hard back and forth to see if it changes when either side is loaded or unloaded? I'm leaning toward a caliper sticking or wheel bearing, but bearings usually make noise.

[sbmackie]

Marc,
Yes. I tried that on the recommendation of the tech at Goldcrest. No change in intensity or sound with loading. There is a "rumbling" or "drone" associated with the vibration. And, I can feel it both in my seat and in the steering wheel.

[dshepp806]

Wish you could load her up with brand new (matched) rubber on ALL corners. If she shows again, then it most probably won't be tire-related. If still there (and, as you described), I'd make sure the alignments are ON. This theme of time-based failure is indicative of (possibly) being a heat-related cause (rubber),......I'm still thinking the tires need to be ruled out WITH a NEW set at all corners.

Else, it's time to greasy and recheck the very items you (and others) have mentioned.

Have you made any progress on this?

Best,

Doyle

[rattlsnak]

Scott, when it happens again very lightly press on the brake pedal while keeping your other foot on the gas to maintain speed and see if it changes.

[Chuck.H]

I had my various vibrations significantly reduced when I returned my front suspension to the zero camber setting (required un-lowering my car a little to achieve). I like the solid feel better, knowing I'm giving up a more stick in the corners. After years of driving cars with 1 degree of camber, I really like the zero setting for street driving.

Chuck.H
'89 TurboLookTarga, 373k miles

[Flojo]

hm. you have a phono that "comes and goes"... strange.

nontheless: what about the bearings?!?!
did you check that (and their basins too)? if yes HOW did you?!

I did, as I hat this similar to your pheno... gone!

[sbmackie]

Doyle,
I just put four brand spankin' new RE-11A's on, road force high speed balance. Thought "that'll do it" Nope.
Half shaft, bearings, and rear calipers are next on the hit parade.

[tlarocque]

Originally Posted by rattlsnak

Scott, when it happens again very lightly press on the brake pedal while keeping your other foot on the gas to maintain speed and see if it changes.

Reviving this thread as my car also has developed a vibration in what feels like the right front. I also experience a humming sound with the vibration. Goes away if I brake. What does this mean???

TIA.

[sbmackie]

Did alignment and re-pack of the CV's and finally haven't heard or felt for several trips. Combination of worn Dunlops (not visibly but heat cycling/stress from AX and some track use) plus alignment me thinks.

Thanks for all the imputs and ideas. I hope this thread helps someone else.

By the way, the RE11's are very good tri-use tires. Sticky enough cold for AX use, predictable at speed on big track, comfy on the street.