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SSLance
06-14-2014, 04:57 AM
I've been slowly but surely over the years chasing down every single little vibration issue on my car to make it as smooth as possible at highway speeds and I've got it pretty dern good now...but I'm still fighting one thing and I'm stumped over what it can be.

So I'm posting this question to see if anyone else has an issue like this and if it is common or unusual in my case.

When I take my car out of the garage and go down the highway, initially it'll have the typical flat spot feel from the tires sitting in one spot. It generally only takes about 3 or 4 miles of highway time for that to go away though...then the car is super smooth wherever I go with it. There is virtually no vibration at any speed when the car starts out cold like that.

But say I drive it to work, and it sits in the sun all day...on the trip home it'll have a shudder that feels like it's coming from all 4 tires between 60 and 70 mph. I can drive through it, or raising or lowering the speed just a bit will make it come or go, but it'll settle back in and not go away. It's not bad enough to make the rear view mirror unusable, but it is certainly noticeable. I first started noticing it on the way home from an autocross event, it scared me pretty good the first time because I thought I broke something in the rear end. But I drove the car again a couple of days later and she was smooth as silk again. The shudder only happens after the car has sat outside in the heat for a while after the tires have been heated up.

It is definitely tire or drivetrain related, pushing the clutch in and coasting doesn't change the vibration at all. and I feel it in the steering wheel and my butt, so it feels like it's comes from the front and the rear. Is this just a trait of 200 tread wear performance tires? Do the rest of you that run a high end sticky street tire have this happen as well?

All of my wheel bearings are fresh and tight, the Falken 615Ks have about 750 miles or so on them, everything else on the suspension is tight and fresh and even the rear axle and clutch have all been freshly rebuilt with no change in this attribute...it almost HAS to be the tires themselves right?

And I'm okay with it...as long as I know that's what it is. If there is something I can do to help it I'm in, or I can just deal with it.

andrewb70
06-14-2014, 09:49 AM
Lance,

is it more of a thump...thump...thump....or a buzz?

Andrew

SSLance
06-14-2014, 10:35 AM
A quick thump thump thump thump... It really feels like a tire out of balance but it comes equally from the front and the back.

I should add, if I leave my car in the garage at work, and drive home that evening, it's fine. It only happens when the car has been sitting out in the sun\heat for a while. And it does not go away until the car has been parked back inside and cooled off.

Bob in St. Louis
06-14-2014, 10:56 AM
Do you have access to a set of wheels and tires to try for a couple days?

SSLance
06-14-2014, 11:06 AM
The only other set I have on hand is the old stock rims with 15 year old tires on them. They probably have their own set of issues with them so I'm not sure how much I could learn by swapping them on. I am thinking about having Discount Tire rebalance all four tires just because I can.

Bob in St. Louis
06-14-2014, 11:06 AM
Just a swag.......what about the driveshaft warping due to heat?

Bob in St. Louis
06-14-2014, 11:07 AM
Yea, I wouldn't try those old tires. Good point.
Does Discount Tire have a Road Force Balance machine?

SSLance
06-14-2014, 11:08 AM
It's a newer 3.5" steel driveshaft, haven't thought about that happening.

SSLance
06-14-2014, 11:32 AM
Yea, I wouldn't try those old tires. Good point.
Does Discount Tire have a Road Force Balance machine?



I don't think so, but I do have a friend with shop that does have one.

Bob in St. Louis
06-14-2014, 11:44 AM
I would definitely use the RFB machine, especially since you're fighting an unusual problem.
To take it a step further, you could even place the tires/wheels out on the hot parking lot before he balances them.

The driveshaft theory is a bit "out there", but it's the only other thing that spins at road speed that I could envision doing somethign weird. Particularly if it's one of those "shaft inside a shaft" type units.

Cobra 498
06-14-2014, 12:02 PM
The tires are most likely flat spotting in the heat, if it goes away after driving for a given distance. This used to be a big problem on bias ply nylon tires, they would shake like hell after being parked for more than a day or two. Try moving the car a small distance every hour or so say 1' at a time during the day and see if that reduces the vibration, if it does, you have found the problem. You could also switch to Michelin PS2 or Super Sports because their construction is not as susceptible to flat spotting in the heat.

SSLance
06-14-2014, 12:38 PM
Try moving the car a small distance every hour or so say 1' at a time during the day and see if that reduces the vibration, if it does, you have found the problem.

That's a pretty good idea, I can try that for sure.

SSLance
06-16-2014, 07:09 PM
The vibration became consistent so I began chasing things down again tonight. Found a loose axle bearing in the driver's side rear. Pissed because it's a brand new part, just a couple weeks old but happy that I found it and it makes sense. Not knowing is worse.

I'll get a new bearing ordered tomorrow and get it swapped out later this week. Thanks for all of the help and ideas of how to chase it down everyone.

Bob in St. Louis
06-17-2014, 04:23 AM
I didn't see that coming.
Congrats on getting it fixed though.

SSLance
06-17-2014, 04:26 AM
Yeah, me either...especially since I just completely rebuilt the whole rear end. I guess if a part is going to fail, it is going to fail right away. I'm going to try to get a warranty on the bearing.


https://www.youtube.com/watch?v=sTVeoQqdFuw

Bob in St. Louis
06-17-2014, 04:51 AM
The fact it seemed to be temperature related was throwing me off. That's weird.
The video you embedded is listed as 'private' though.

SSLance
06-17-2014, 07:31 AM
Should be fixed now... Sorry about that.

Moser explained to me that I can get a better bearing from Napa than from them... They use Green Bearing company bearings whereas I can get National Federal Mogul or Timken bearings from the parts houses. Better bearings but won't have the o-ring seals on them. I ordered a pair of them, will be here tomorrow. Will fix the driver side then keep a real close eye on the passenger side. I don't want to change it out unless I have to as it's the one that was so hard to get sealed up.

minendrews68
06-17-2014, 05:20 PM
Be sure to post if this fixes the problem. I'm sure everyone would like to know..

Bob in St. Louis
06-17-2014, 05:23 PM
Wow, that's a CRAZY amount of play in that bearing.
I'm surprised it "didn't" vibrate some of the time!!

SSLance
06-17-2014, 05:48 PM
The last day I drove it it was vibrating all of the time...even when cold. That's when I decided I had to tear into it to find it.

I can wiggle the outer race back and forth in my hand now that the axle is out of the housing. Unbelievable how bad it got so quickly. Was a little bit of gear oil between the seal and bearing and it looked clean, no metal in it and no metal in the axle housing.

Hopefully get the new bearing pressed on tomorrow.