Just looked up Hunter Road Force machine. http://www.gsp9700.com/pub/features/how-1.cfm

These guys have obviously heard of RFV, and even state that balancing doesn't correct RFV which answers my concern re you CANT (I've just spotted that I put can earlier) balance whilst the wheel is loaded.
I'm concerned that they don't allude to what is done if the RFV (measured as the load or change of distance between the road wheel centre and the loading drum centre)
is considered unacceptable or howhey improve it.

The RFV machines that I have used used to " the tyre in a manner to offset the RFV high and Low spots. (Shave = Remove rubber from the tread area).

If this is what the Hunter does it is indeed a useful bit of ki. If after being measured, shaved and balanced (in that order) any input coming from the tyres should have been reduced to a level below the sensitivity level of the vehicle and therefore resolve the problem.

So if this is what they are doing, and the problem remains, you problem must lie elsewhere.

Engine mounts and transmission shaft come next in root cause determination.

Stuart.

They also state there machine can correct "Pull". Pull (if due to the tyres) is due to an effect known as Conicity and I wonder how they fix that??
...unless once again they "shave" the tyre with an appropriate conical effect on the tread.

Shaving does wonders for tread life!!

 

Stuart,
Thanks for the comments on the Hunter approach. From what I observed when mine were done, it does measure wheel center to tread, but does not 'shave'. I had thought about an out of round (OOR) previously, but discounted it, again, because the tires when new, and subsequent ride, for the first 6000 mileswas perfect.

On the Magic Fingers comment, you wouldn't find one of these at the Savoy! Very old relic of inexpensive roadside motels in the 60's-70's.
Thanks again for all your thoughtful replies.

Bob

 

So if they don't shave the tyre what do they do to improve RFV should it be bad.
Measuring it doesn't do anything to improve matters!

Just a thought.

Even if tyres are good when fitted they can become bad because of bad dampers etc but nowadays dampers etc are pretty reliable and last for 100,000 miles +

Still think its most likely wheel and tyre RFV / balance.

Stuart.

 

Couple of updates. My harmonic balancer was replaced under the recall. Second, took it to the Benz 'guru' who definitely feels the car isn't right. Harsh ride and transmitting/amplifying every road defect per him. I'm dropping it off Thursday for his ministrations. Hopefully I'll pick it back upand it will be healed without too much pain to my wallet.

While I was on my way there, I revved the engine to 4 grand to see if I had any vibration and the engine did a stumble, rubbery thump. Does it every time at 4 grand. Is that the governer/limiter kicking in or something I should be worried about? I forgot to mention it to the guru but I will on Thursday.

Mark

 

Hi Mark.

......and the engine did a stumble, rubbery thump?? Not sure what you mean here..
The throttle is electronic and has logic to prevent over rev when engine in neutral / stationary.
The normal driving rev limiter is the same device but comes into play under totally different conditions.
Both limit the revs by "cutting" the spark.

I'm becoming confused as to who has said what but I'm beginning to think your problems may be engine misfire orientated but without a clearer understanding and feel for the vibration, stumble or whatever i really can't add much more.

Stuart

 

Stuart,

I didn't mean to add to any confusion. After the harmonic balancer came up in the conversation, along with engine vibration, and while I was bored sitting at a stop light, I revved the engine while in park to see how smooth/rough the engine was through the RPM range. I never really revved it very high before while actually watching the tach so I thought I would shove it up pretty high. Silky smooth up to 4 grand and then kind of a large, rubbery, thump, stumble. Actually more of a thump, thump, stumble, stumble. Surprised the heck out of me. I repeated it half a dozen times and every time at 4 grand, same thing.I wasn't watching the tach to see if the RPMs decreased during the thump, thump, stumble, stumble,because I was concentrating on when it started and attempting to figure out the noise.The thought occured to me that it might just be agovernor/limiterof some sort because it happened exactly at the same RPM and the engine would run fine again from zero to 4 grand. Pure guesswork that it might have been somethingbuilt in to keep the engine from over revving without loadat that RPM. Emphasis on'pure guesswork'.Can somebody with an SL 500 try the same thing?Not sure if it is even related to my overall issue or just something new and interesting

Mark

 

Definitley a rev limiter. Hits 4 grand and won't go more regardless of the gas pedal travel. Absolutely no engine vibration up to that point.

Mark

 

M,

Its just the " when stationary" rev limiter kicking in.
It cuts the "ignition" so the engine coughs and stumbles but should maintain the 4000 or whatever the threshold limit is on the SL / engine type.
Like Formula 1 cars going thru the pits, cough splutter bang!! but in that instance the cars are limited to 40/50 mph for safety of personnel.

 

Hi guys. I just picked up my first MB, a 1996 SL600. I'm also new to the forum.

I have been researching the internet as I have the same "vibration" issue with my car. Was there any resolution to the one in this thread?

 

Welcome to the forum Doug and congrats on your new ride!

You're at the end of a very long thread where a number of potential solutions for 'vibrations' have been posted. It would help us help you if you would describe specifically what's happening in your car, i.e., Vibration at idle...or Vibration at X RPM's....or Vibration at X MPH...or All the above or none of the above!

Bob