OT Question on Improving the Ride of an SUV

daepp · 05-07-2008, 09:41 AM

No Porsche content - sorry.

I own a 2001 MBZ ML 430 with 200K miles on the clock.

When the OEM Dunlops tires were no longer available, I switched to Goodyear Forteras as I was still occasionally taking it on some pretty hard core off-road trips. I have since moved on, and I am letting my 16 y.o. daughter use the M Class.

When I went to the Forteras I felt the ride got a lot worse. I'm told they are very stiff tires. Anyone have any experience with Continental tires? And generally speaking, how long are original shocks good for? Would new shocks make the ride any better? At a Benz forum someone suggested that new shock would give a more compliant ride - but not being very suspension knowledgeable, I always thought new shock would be stiffer.

My wife has a GL 450 and my brother drives a late model ML350. Both have far superior rides. Of course, these two new cars are unibodies, and the GL has a much longer wheelbase. My ML 430 is built like a truck on a boxed ladder frame. I was ok with that for a long time, but now I wonder if there's anything that can be done to give it a better (softer?) ride.

Rot 911 · 05-07-2008, 10:36 AM

If you actually go off road your shocks were toast at 50K miles. Your old shocks probably are transmitting every bump they go over.

tcar · 05-07-2008, 10:41 AM

Quote:

Originally Posted by daepp

At a Benz forum someone suggested that new shock would give a more compliant ride - but not being very suspension knowledgeable, I always thought new shock would be stiffer.

Just the opposite. Replace them.

Also, your new tires will wear poorly w/ bad shocks.

daepp · 05-07-2008, 10:56 AM

Not a lot of miles off road but several day trips per year with my son. I think that I'll go ahead and change out the shocks and see how that turns out. I drove the car so long I guess I didn't notice the deterioration in ride quality. Now that my (ahem) princess is driving it I'm starting to hear about it.

daepp · 05-07-2008, 11:06 AM

Misc trips over the years...

gprsh924 · 05-07-2008, 11:21 AM

Come on, you at least have to get a tire in the air.

daepp · 05-07-2008, 12:09 PM

That's very cool!

I'm afraid my stupid stability control would make the up side drop like a rock - I know it does when I go off a curb etc.

gprsh924 · 05-07-2008, 12:44 PM

Yea the same type of thing happens in my Mom's Lexus.

I'm in the top picture...it was a little bit scary the first to get the wheel in the air, but you quickly get a feel of where the cars balance is and that was relatively safe. However, that is my friend in his Xterra in the second picture. He did not take the line that we had planned for him and he was teetering on the edge. We eventually had to hook up a safety strap to him to make sure that he did not flop it.

Tobra · Tobra's Garage

Bilstein

onewhippedpuppy · 05-07-2008, 01:01 PM

Shocks. Your OE ones were probably shot at 100k, but because it's a gradual decline you don't notice. Shocks absorb/dissipate the impacts, without shocks anything not absorbed by the tire or suspension bushings is sent right to your seat.

daepp · 05-07-2008, 01:08 PM

Thanks for all the help.

island911 · 05-07-2008, 01:16 PM

Quote:

Originally Posted by onewhippedpuppy

Shocks. Your OE ones were probably shot at 100k, but because it's a gradual decline you don't notice. Shocks absorb/dissipate the impacts, without shocks anything not absorbed by the tire or suspension bushings is sent right to your seat.

NO..."Shock absorbers" are there to control the springs. They ADD impact to the driver/passengers.

island911 · 05-07-2008, 01:21 PM

Quote:

Originally Posted by daepp

...My ML 430 is built like a truck on a boxed ladder frame. ....

There is the problem. And obviously the change MBz made to address the problem.

onewhippedpuppy · 05-07-2008, 01:29 PM

I didn't express that very well. More like absorb the motion, because they dissipate the kinetic energy of the wheel in motion. I'm not sure how they ADD impact though. They absorb the motion of the wheel such that it doesn't get translated to the vehicle. Unless we're saying the same thing in a different way.

island911 · 05-07-2008, 01:50 PM

While they do "absorb" energy, and convert it to heat, they transfer load while doing so(shock/bump/kinetic energy...) A softer (or missing) shock does less 'energy conversion, and thus, less transfered load. Consider the mounting points of a shock... when a shock is doing it's job, it transfers load from one mounting point to the other. If you take the shock out no load will be transmitted by the shock. Of course the spring will have to travel farther... fwiw, a shock (aka damper) produces a force as a function of speed (call it 'bump speed') whereas a spring produces force as a function of displacement (call it 'bump height')

onewhippedpuppy · 05-07-2008, 02:05 PM

But in most modern cars, that force will still be transferred from the spring to the body/suspension members/strut mount/etc. It's better to look at from an energy standpoint. Impact energy from bumps is transferred to the shock, which dissipates/absorbs much of the energy, changing kinetic energy to heat. Without a shock, this impact energy is transferred to the car itself.

island911 · 05-07-2008, 03:37 PM

Again, in absorbing energy, a "shock absorber" must transmit a force. --A softer "shock absorber" will transmitt less force/shock/impulse to the frame than a firm "shock absorber" ..for a given bump speed.

"Without a shock, this impact energy is transferred to the car itself." W/o a damper, the energy will be put into inertia of the unsprung mass which will, inturn deflect the spring farther. Spring energy is stored energy. ...the "problem" which a damper/"shock absorber" solves is not found in a diminished force to the frame, but rather to control the inertia of the unsprung weight ...so your wheel(s) don't 'Evil Kenivel' (catch big air) over each bump. ...and that the sprung weight doesn't baby-buggy rock with every accelaration.

"shock absorber" is a real misnomer.