Tires out of balance or what?
 

My 1984 190d at about 40mph started to shake a little bit - you know, like the tires are out of balance. I took her to have the tires rotated and balanced. The slight shake is still there, but at different speeds - 55, 45, 60, etc. Now, while I'm driving, say at 55 she shakes a little. I slow down and get back up to 55 and she's as smooth as silk. I guess what I'm trying to say is that some times she will, and sometimes she wont. When I had the work done I just mentioned I took her back because I thought they did not get the tires in balance. So, they did it again. If its not the tires, what in the world could be causing this??

Sincerely,

Hugh

shaking
 

I've had the same problem at high speed and went thru the tire balancing and rotation etc. like you are doing, at the end the problem went away when I replaced the steering dampener... My 2 cents

Shakes
 

Definately the steering dampener. Check the tie rod ends and Pitman while you're under there.

The steering dampener nor any other part in the front end can CAUSE a vibration. Bad parts can allow a vibration to be exacerbated, but only ROTATING parts can CAUSE vibrations.

The most common cause of vibrations are indeed tire related. Of the tire related causes, the most common cause is when the tire store kids do a static balance rather than a dynamic balance. A static balance involves putting a weight on the inside lip of the wheel only. This will prevent the wheel from hopping up and down, but on todays nimble suspensions this is not good enough.

A dynamic balance uses wheel weights on the inner and outer plane of the wheel and prevents the wheel from wobbling. The tire store kids avoid this because they get yelled at when they scratch alloy wheels with wheel weights. To dynamic balance WITHOUT scratching alloy wheels, a savvy wheel balancing tech will use tape weights just behind the spokes of the wheel for the balance of the outer plane.

If your tire store gives you a blank stare when you tell them that you want your wheels balanced this way, find another tire store.

As far as steering dampeners and other front end parts, I would not replace them until I got the vibration to go away. That way you have a system that will more easily tell you when a wheel is out of balance. Once the wheels are properly balanced then, of course, find and repair any loose or worn front end parts.

Good luck,

Shake
 

I agree with Larry. It could be poor balance. I got 4 new Goodyear tires recently, and the car shook as out-of-balance, yet the tires were spin-balanced on an electronic balancer. Found someone with a Hunter machine which measures road force (actually rolls the tire under load to check for uniform stiffness) and one new tire got junked.
My 420 was extremely sensitive to shake, to the point it was not drivable at speed, until I changed the steering damper; the old one offered no resistance when moved by hand. Everything fine now.

I would add that warped rotors will add to the harmony of vibration issues...

...though I have a number of front suspension parts that need attention, replacing the wheels,tires and all sorts of balancing did NOTHING to reduce the highway-speed vibration issues...until I finally replaced the original rotors on the car. Vibration reduced by about 95%!

It seems to me rotors would cause a vibration only when you braked. That's how I knew my rotors were shot in another vehicle. they were barely within spec, but got slightly warped.

Changed rotors, no problem.

I agree with the balance situation. I have had many tires balanced and it has been years since I have had a balance problem...and I dont' get tires balanced at any fancy place. I hope your ball joints or tie rod ends are not really, really worn.

Larry,
I've pretty much always agreed with you on most posts, because you are a professional and know your stuff, but I'm going have to disagree with this one. I too was tought during my apprenticeship that a loose front end component could allow shimmy but not cause it. I've had a couple of times and a 91 4matic wagon in particular where I couldn't find anything wrong. The steering shock on the wagon wasn't too yippy skippy, but I couldn't see how that could cause the intermittent shimmy. In desperation I changed it, and the problem disapeeared. I know, Larry, just when we think we know something, they change the rules.:D


Randy,
High speed tires are rated at higher speeds, because they are designed to control expansion at higher speeds. A tire will balance fine on any old balancer, but when the tire starts rotating at speeds that make the tire want to fly apart, an area of a defective tire will actually go out of round causing a deformity in the tire at high speeds. That special Hunter balancer you mentioned can detect the defect. It is funny you mentioned Goodyear, because that is one tire company that has had a problem in this area. For normal everyday balancing almot any balancer will work fine unless you encounter this problem. Then you need to seek out the Hunter. In fact my wheel balancer is a Snap-On that doesn't even spin the tire. You reach down and spin the tire a few revolutions by hand and wait till the LEDs tell you where to put the weights. I also have a Sun high speed balancer, and I don't see any difference between the two. Hope this helps.

Autozen,

I have seen something similar to what you describe in the case of the dampener correcting the vibration. This is a very unusual thing to see happen. In the case where I saw it, there was a combination of alignment anomalies that were causing it. If I remember correctly it was a previously crashed car that was way out in camber and a little toed out. The combination seemed to put the front wheel in a bind while going down the road straight and was causing the wheel to shimmy in and out.

Such an odd situation can cause all sorts of weird things to occur, but typically if the wheels and tires are properly balanced, no excessive RFV or lateral run out, you can take the dampener off and throw it away and not be able to tell the difference. That's just what I've found.

As with anything, there are almost always rare exceptions to the rule.


As far as todays Goodyear tires go, I would run wheels off of a covered wagon before I would spend my hard earned money for Goodyear tires. If I were going to sell Goodyear tires I would make DARN SURE that I had a GSP9700 in the shop with a maintenance contract on it because I would probably wear it out in short order.


BTW autozen, I know the Snap On manually turned balancer that you are talking about and I think that it is an OUTSTANDING unit. It does the very same thing as most any other spin balancer and does it in the same way. The difference is that you don't have an expensive drive motor to repair/replace/rebuild. The computer balancers don't need to spin the wheel fast to resolve the balance. I expect that they will work as good or better than any computer spin balancer. I have an old Coates 1001 and love it, mainly because I have learned how to fudge the settings for different situations such as using tape weights behind the spokes for balance of the outer plane. I would like to have found a Snap On like yours because not only does it do a great job, but I love the simplicity of these units.

My $0.02,

Getting a little off topic here, but my recently purchased Goodyear tires say " Made in Slovakia " on the sidewalls. :confused:
So far, so good.
On the steering dampener, it's always been my understanding, the function of it is to " soften", i.e. dampen the steeringwheel movement, whenever the frontwheels travel over bumps/ripples in the road.

I'm no pro, but I've certainly fought my share of vibration problems over the years. Most dampers aren't that expensive, so if the car has the miles, it could almost be considered a maintenance item.

In the majority of my cases, it turned out the be the result of tires with faulty belts - on brand new tires, on tires with 20k miles, and with worn tires.

Even if your wheels are properly balanced - statically and dynamically with weights on both sides - and the machine reads zero-zero on the check spin there is always a slight residual static and dynamic unbalance because modern machines only balance to within about 2-3 in.-oz.

I KNEW my steering damper was leaking, but I put it off, and the car on a couple of occasions went into the worst front end shimmy I have ever experienced, and the wheels were in good balance. Shame on me. That steering damper (not dampener or dampner) is there for a reason and an IFS with a lot of caster needs one.

If the damper is leaking, it needs to be replaced ASAP. It's also easy to disconnect one end and test it. Gas pressure should expand it and it should take a good 20 pounds of force to slowly compress it.

If it's leaking or limp - REPLACE IT!

Duke

Larry,
Snap-on likes to take credit for the concept, but I remember seeing a German unit at a local dealership about 25 years ago that operated the same way. I was awe struck at the time. Interestingly I was talking to a seasoned mechanic yesterday, and he said he can match any high speed balancer in a closed room with no drafts and a bubble balancer. I believe him and wouldn't put any of my money up to challenge him.:D

Your mechanic friend is correct in that he can achieve a STATIC balance with a bubble balancer as good as STATIC balance achieved by a spin balancer, but it is impossible to do a DYNAMIC balance on a bubble balancer.

I do believe that he can achieve a static balance with his bubble balancer that is equal to a static balance on a spin balancer, but that is not NEAR good enough with todays resilient suspensions.

Static balance only keeps the tire from hopping up and down while a dynamic balance given by a properly operating spin balancer, keeps the wheel from wobbling. If you only do a static balance for a wheel that is going on a Benz, you will have a vibration unless you are VERY lucky.

Have a great day,

That's always been my thinking. A bubble balancer will take out a heavy spot radially, but I don't see how it can differentiate axially. Again I wo't argue with him. I'll just keep using my spin balancers.:D