johnnyrocket52

Hello, the car drives near perfect most of the time. Between 65-70 I get a very slight vibration and remains there as fast as I dare to drive. Most people who ride in the car don’t notice it, but I do.
Tires are approximately 6 years old and have excessive road downforce as measured by Discount Tires. ~35 lbs down force, like a truck.
I going to start replacing first fronts then the rears. See where that goes.

Is there a method to inspect the driveline for excessive wear? Is the driveline two pieces with a bearing in the middle?

A member mentioned they had a vibration in their S600 at 65mph, changed out the upper/lower control arms and that fixed the issue.
Is there a method to inspect the upper/lower control arms for excessive wear before spending boo coo money?

Low hanging fruit would be the tires…

Thanks,
Johnny

BOTUS

mine does it... comes and goes, at times its shocking, at others you forget its there - swapped tyres thought it helped but it came back

all the posts about prop shaft centre bearing support being tired jogged my mind the other day - maybe its this

nath_h

Lots of folks have had this problem, me included. What worked for me was changing out the control arms and tie rods, which took care of 95% of it. Then, I bought a new set of OEM wheels...problem gone. My old wheels which had been straightened were just not straight enough--despite what the wheel repair shop said.

vettebk

It is two problems. I had the same problems. Changed out the entire front end components with new FCP OEM parts. Upper and lower control arms, forward and rear, and tie rods. Technician also said the OEM wheels are easy to bend (duh!). He suggested wheel repair; I bought remanufactured for the right rear. That took care of it. Wheels were hard to find.

It is definitely those lower control arms. They are also particularly difficult to check for wear. You need to put a load on the suspension when you grab that wheel and shake hard. I replaced mine at 92K miles.

Arrie

I assume you use original wheels but if you don’t make sure centering rings are used when mounted on the hub.

BOTUS

.... I have an issue at the rear of the car - which is what I thought the OP was saying...

wheels offset on the hub is what makes the front play up

johnnyrocket52

Thanks folks for the suggestions.

To keep the costs in check, the repairs will need to be categorized by cost and historical evidence.

The age of the tires are ~ 7yrs, with very excessive road down force as measured. The rims look perfect. Could be reworked rims though.
New tires would reveal a fouled up rim.

Next on the list would be the upper/lower control arms. Probably not a weekend project, more a of a shop procedure?

Anyone have a drawing and procedure on the the driveshaft from transmission to rear differential?

Johnny

JohnLane

90+ percent of vibrations on the freeway are going to be tires/wheels. Seven year old tires? Toss them now before one decides to blow out for a torn up fender liner or worse. Very often a wheel that is not perfectly straight will make a mystery shake. It balances out OK on the machine but it shakes on the road.
Driveshaft vibrations are at Differential ratio times MPH for how fast it shakes. Figure Wheel speed X 2.5 roughly. Feels very different from a tire/wheel shake.
A C/V shake will be only under load. Usually at higher speeds. Lift the loud pedal and shake stops.
Suspension components that are soooo worn as to contribute to vibrations are a clear indicator of an owner who is not looking after his junk.... Also... Suspension parts will make a tire/wheel/brakes shake more dramatic.... not be the root cause of a shake.
Take care of your junk guys!

vettebk

Totally agree on the wheels. Our alloy wheels are made from chewing gum wrappers. I'd really like to find a decent looking set of non-OEM wheels that would fit in with the look and presence of my S600. My Mustang and SRT8 wheels never had any problems.

And it never helps when I clip curbs or hit dividers. Just bought a new rear wheel and one day later, backed into a curb. OEM 19 inch wheel from the dealer, $870 plus a core charge. It just never stops.

johnnyrocket52

Starting to make sense the different types of vibrations. If cruising at 70mph, vibration is constant, tap it into neutral, no torque loading, and vibration remains unchanged, it’s looking like rims/tires.
Gonna get 2 new front tires and verify road down force is measured low, under 10lbs, like it should be, and road test.

Johnny

JohnLane

What happens in the front of the car that is a useful diagnostic tool you ask?

There is a large round tool in front of the driver. It doesn't just instruct the car what direction to go but provides useful feedback to an attentive driver.

Where there is a vibration in the front of the car that large round tool in front of the driver will shake along with the front wheel(s).

No shake there? Where else might we look? Hmmmm

BOTUS

from gearbox to the back wheels

JohnLane

How many PSI do you run in your tires? Pro-tip.... Give them 44psi and aside from curb rash you won't be replacing wheels. A pothole will still wipe out a tire but the wheel has a LOT more protection. Yes, you will feel more bumps but if the goal were a pillow soft ride we'd get there with 15" wheels and an 80 aspect ratio tire and 30psi. LOTS of sidewall to deflect. Alas those won't fit over modern brakes.

JohnLane

Ladies and Gentleman we have a winner!

Overwhelming percentage will still be wheels and tires.

Good morning Botus. 14:00 for you?

BOTUS

yep (so good afternoon)