Rear suspension harshness problem

[lifespeed]

I rebuilt the entire suspension on my '04 about six months ago using Penske coilovers and shocks (see this thread (http://www.mercurymarauder.net/forums/showthread.php?t=84895) for details on the shocks) as well as Metco arms in the rear and Addco tubular sway bars. In the rear I decided to keep the stock links, but substituted the poly bushings instead of the through-bolt aftermarket arrangement. The rear bushings were just re-greased after about 4K miles.

Part of what prompted me to rebuild the suspension, aside from 100K miles and 9 years of wear, was the realization that ride quality had deteriorated dramatically with the stock suspension and shocks.

So now I have a car that rides beautifully in the front, but the rear is very harsh. The natural frequency of the rear seems too high. Compression seems to "bounce" the rear upwards off of the shock resistance. I have re-valved the Penske rears twice going softer each time, but I don't think they are soft enough. I also think they may need to be valved digressive (here is a brief description of valving (http://www.circletrack.com/techarticles/shock_absorber_shock_dyno/)). The original vendor of the Penske rears has stated they are not familiar with air springs, and I don't think they have changed the internal piston during their re-valve attempts. If you don't change much, the results don't change. :rolleyes:

I have driven alongside the Marauder to observe the suspension action on a bumpy freeway. It is plainly obvious how well the front works, and how stiff and high-frequency the rear response is. On the several occasions I have removed the Penske's for a re-valve, I have observed the stock blown-out shocks ride even worse than the Penske's.

My question is: Has anybody with Metco arms and/or Addco sway bars observed that freedom of movement of the rear suspension is high-friction? This would interfere with good ride quality and add to the damping rate in unpredictable ways. To be honest, I don't have a lot of reason to think this is the case, but I have worked on this several times without success.

Today I am shipping the rear Penske's off to a different vendor (RE suspension) to be re-valved digressive in the belief that limiting the maximum damping rate will reduce the harshness and allow free-er movement in the rear.

I am half tempted to buy a set of KYB's to try, as I once drove a members car with those in the rear and it seemed well-damped but not overly harsh. But I would think the correct valving in the Penske's should be better than KYBs . . .

[Mr. Man]

Are you using a "regular" sized tire, 55 or 50 series aspect? Thinner tires(spring rate) can add to the rough ride.

Try adding some weight in the trunk and see if the ride settles down. If it does you are on track to tone down the rebound.

You seem to have a good handle on how it all works. Perhaps some larger valving can allow the fluids to transfer a little quicker being the MM is such a heavy car. I'm no expert here but suspension set ups do interest me alot. Hope your next move improves the ride. :)

[Krytin]

Did you lower the rear?
Mine rear bounced a lot when I first lowered it until I looked at the rubber bump stops on the axle - they were hitting hard! That was only lowering it about 1.5".
Now that the car is all the way down I can only guess that they would have been riding on the frame!
I don't have any problem w/any bounce up off of major road deviations but you can "feel" them a little more mostly due to the 45 series sidewalls.

[lifespeed]

Are you using a "regular" sized tire, 55 or 50 series aspect? Thinner tires(spring rate) can add to the rough ride.

Try adding some weight in the trunk and see if the ride settles down. If it does you are on track to tone down the rebound.

You seem to have a good handle on how it all works. Perhaps some larger valving can allow the fluids to transfer a little quicker being the MM is such a heavy car. I'm no expert here but suspension set ups do interest me alot. Hope your next move improves the ride. :)

I have stock size Firestones all around. Either increased weight in the rear or driving at high speeds improve ride quality dramatically. So it does appear softer shocks are the right direction to go.

[lifespeed]

Did you lower the rear?
Mine rear bounced a lot when I first lowered it until I looked at the rubber bump stops on the axle - they were hitting hard! That was only lowering it about 1.5".
Now that the car is all the way down I can only guess that they would have been riding on the frame!
I don't have any problem w/any bounce up off of major road deviations but you can "feel" them a little more mostly due to the 45 series sidewalls.

I was wondering about this. Currently the fender lip is about 1/2" above the (stock) tire tread, so not lowered that much. I looked at the bump stop location and they appear to have 1-1/2" or 2" of travel before they contact the frame. The paint on the frame rail appears slightly polished from contact with the stops, but the paint is mostly still there.

I think I am probably not hitting the stops under most conditions, but I'll install the shorter stops you mentioned. If nothing else it is a relatively easy troubleshooting step.

[MOTOWN]

I have the Metco arms, Watts link with Addco solid bars front and rear, it definetly adds a more Rigid feel to the rear of the car, also the lower you set your ride height (less air in the bags) the harsher the ride, i adjusted mines to a higher ride height and the ride quality was night and day difference!

This may be part, but not all of your problem.

[Krytin]

I was wondering about this. Currently the fender lip is about 1/2" above the (stock) tire tread, so not lowered that much. I looked at the bump stop location and they appear to have 1-1/2" or 2" of travel before they contact the frame. The paint on the frame rail appears slightly polished from contact with the stops, but the paint is mostly still there.

I think I am probably not hitting the stops under most conditions, but I'll install the shorter stops you mentioned. If nothing else it is a relatively easy troubleshooting step.

Take a closer look at the top edge of the stop - I could see the rubber was actually starting to tear along the edge. There was also a "polished" section of frame rail. At this point I believe the top of the fender wheel arch was dead even w/the top of the oem size rear tires.
On a side note - I would be interested in what you find regarding the individual height of the oem stops when you look at them again or take them off.

[tbone]

When you installed your control arms, was the diff hanging down or did you place it in the loaded position? You may have a preload condition.

[Mr. Man]

When you installed your control arms, was the diff hanging down or did you place it in the loaded position? You may have a preload condition.
Can you explain this? The control arms swing up and down freely and are designed to control front to back movement. I don't see how the control arms would cause harsness in any way but I've seen a couple of people mention pre-load over the years. I can only see how pre-load would come into play if the conrol arms were to be bolted tight (no movement). :)

[tbone]

When I put my Metcos on I was advised to jack up the suspension before tightening the bolts to avoid pre-loading the bushings and causing premature wear. Not positive it would cause a super stiff ride. Just another item to cross off the list.

[lifespeed]

When I put my Metcos on I was advised to jack up the suspension before tightening the bolts to avoid pre-loading the bushings and causing premature wear. Not positive it would cause a super stiff ride. Just another item to cross off the list.

I have heard this advice in the context of rubber factory-style control arm bushings. I do not think it is applicable to free-floating greasable polyurethane bearings where the inner and outer shells float freely.

I hired a suspension shop to do the rebuild, so I'm not exactly sure what they did.

[lifespeed]

Take a closer look at the top edge of the stop - I could see the rubber was actually starting to tear along the edge. There was also a "polished" section of frame rail. At this point I believe the top of the fender wheel arch was dead even w/the top of the oem size rear tires.
On a side note - I would be interested in what you find regarding the individual height of the oem stops when you look at them again or take them off.

Both you and Motown Marauder have pointed out the potential lack of travel issue. I did previously raise the rear suspension slightly, but it was when I had the first version of rear shocks which were ridiculously stiff so hard to tell what was going on.

The 1-1/4" tall bump stops from McMaster-Carr are on order, so will look at this again when they arrive and report back.

It's going to be close to 3 weeks before I get the revised shocks back given one week shipping each way, coast to coast. Don't know why all the shock people are on the east coast. :dunno:

[burt ragio]

I agree the rear rides harsh with no control. Regardless of multiple upgrades & combinations I have found the same results. I feel larger shock valving would make a difference. I have been temped to look into the new magnetic shocks used in the cadillac & new camaro.

[Mr. Man]

I agree the rear rides harsh with no control. Regardless of multiple upgrades & combinations I have found the same results. I feel larger shock valving would make a difference. I have been temped to look into the new magnetic shocks used in the cadillac & new camaro.Also used on the Corvette. I think they are computer controlled somehow. Be an interesting mod if you could figure it out.

[lifespeed]

I agree the rear rides harsh with no control. Regardless of multiple upgrades & combinations I have found the same results. I feel larger shock valving would make a difference. I have been temped to look into the new magnetic shocks used in the cadillac & new camaro.

They exist (Magneshock (http://www.magneshocks.com/streetrods.htm)), but if you thought Penske shocks were expensive . . .

I still think the correct rear shock, along with shorter bump stops and a reasonable ride height should do the trick. I bounced the rear suspension last night. I have a trailer hitch to stand on, so can get some pretty good movement. It came very close to touching the bump stop with 200 lbs jumping on it, so it most likely does hit the stops on big bumps.

Any time you hit the bump stops the suspension has stopped working, so that has to be eliminated first. As cool as it may look, I don't think we can lower these cars much at all. Even with the shorter stops.

[burt ragio]

What were your final settings on the front Penskee ?
Did you get the front re valved or just adjust the compression & rebound if so what were the final settings ?

[lifespeed]

What were your final settings on the front Penskee ?
Did you get the front re valved or just adjust the compression & rebound if so what were the final settings ?

The original valving in the front was correct. ANZE is very familiar with linear coil springs and shocks, so they knew what to do up front. They are set at 23 clicks from full stiff compression, 13 sweeps from full stiff rebound. This is about half way (the mechanism is slightly different for compression and rebound). The springs are 600 lbs/inch. It was completely obvious what the correct settings were. The travel is reduced compared to stock because of the adapter on top required to mount the standard coilover. Still, it only hits the stops on the most extreme bumps at high speeds.

The ride quality in the front is perfect. Firm, but still soaks up the bumps nicely.

[burt ragio]

So what is your ride height from ground to front center wheel well ?
How less is the suspension travel due to adapter ?
Did you ever compare & measure the oem spring length to the Penskee 600 LB spring ?
Do you think a taller 600 LB spring rate would prevent bottom out ? I had that issue with the Naake QA1s.

[lifespeed]

So what is your ride height from ground to front center wheel well ?
How less is the suspension travel due to adapter ?
Did you ever compare & measure the oem spring length to the Penskee 600 LB spring ?
Do you think a taller 600 LB spring rate would prevent bottom out ? I had that issue with the Naake QA1s.

27-1/2" ride height, or about 7/8" from the fender lip to the tire tread in the front. I have been contemplating adjusting it up 1/4" to 1/2".

Here is a huge photo of the shocks (http://home.comcast.net/~claybu//pics/marauder/Marauder-ANZE-vert.jpg) on 1" grid. You can see the adapter eats up about 2" of travel compared to stock. However, the stiffer 600 lb spring and shock means not as much travel is required. Also, a yellow progressive bump rubber is included on the shaft. Bump stops are actually a very important part of the suspension, and are in use more than most people realize. Some sports car designs actually have the bump rubber touching with the car sitting at static ride height!

The height of the spring that is on there now is correct. The travel is limited by the shock body and available installed height under the adapter, which in turn is a function of the overall length. The only way to get back the travel is to use the frame mount setup, which requires a stock-style spring and is more unsprung weight. It is very convenient to use a standard coilover spring. Any spring rate and height is available.

The 600 lb spring is totally appropriate for this car. Although it is true my Marauder is no longer an off-road vehicle, bottom-out events are rare and only result from the ridiculous highway paving we have here in the SF Bay Area. The spring, shock and bump stop control the car well. I can increase shock stiffness a bit and raise the ride height using the coilover spring perches if I want.

[lifespeed]

I am going to try the Energy Suspension 9.9154 (http://www.prothane-suspension.com/proddetail.asp?prod=9.9154) as it looks like it will provide a nicer arrest of the rear suspension and may be a good fit for our cars. The tab will have to be cut off and the axle mounting bracket drilled for the 3/8" bolt vs M8 stocker.

http://www.carid.com/images/energy-suspension/suspension-systems/9-9154g.jpg

[Krytin]

Those look very good!
I don't think you will need to drill out the mounts for the 3/8" bolts - the McMaster-Carr bumpers I used have 3/8" bolts and I don't remember having to drill the mounts out.

Good luck - keep up the great mods & info!

[lifespeed]

Those look very good!
I don't think you will need to drill out the mounts for the 3/8" bolts - the McMaster-Carr bumpers I used have 3/8" bolts and I don't remember having to drill the mounts out.

Good luck - keep up the great mods & info!

Have you compressed the rear enough so your shorter bump stops touch the frame? Is there still sufficient clearance between the axle and frame, driveshaft and floor, etc? 2-1/2" more movement of the axle towards the car is quite a bit, hence the question.

The Energy Suspension bump stops will arrive today, so I'll install them tonight. RE suspension has completed one shock using a digressive/linear piston for compression/rebound. This should be much softer over the "slow" range of suspension velocity and provide a comfortable, yet well controlled ride. Getting close to trying what I hope is the final configuration.

[Krytin]

There is about 1.5 to 1.75 " of travel between the bump stop and frame - it does not appear to be hitting enough to leave a mark on the red poly. The rear takes speed bumps and heaves in the road w/no problems with the exception of the cast aluminum diff. cover/girdle and the Addco sway bar. There is a small spot on the cover where the bar must rub once in a while but I don't hear or feel it.

Good luck with your set-up. I hope you get what you're looking for!

[lifespeed]

Shorter bump stops are in. They did require drilling the mounting hole to 3/8". Not much change, I suspect they were only hitting from the worst bumps. The OEM bumpers were good as new, aftermarket units are 2" shorter.

One week till the re-valved shocks get here. First I'll remove the OEM shocks, put the car back down, and bounce the rear without any shocks installed to try and get an idea if the Metco control arm bushings have too much friction.

[burt ragio]

Do you recall the rear oem travel distance between bump stops & axle ? What results did lower ride height achieve ?


There is about 1.5 to 1.75 " of travel between the bump stop and frame - it does not appear to be hitting enough to leave a mark on the red poly. The rear takes speed bumps and heaves in the road w/no problems with the exception of the cast aluminum diff. cover/girdle and the Addco sway bar. There is a small spot on the cover where the bar must rub once in a while but I don't hear or feel it.

Good luck with your set-up. I hope you get what you're looking for!

[Krytin]

The free travel now is close to the oem. It has been over 8 years now since I changed it.

Lowered front and back - back lowered more than front so that the car sits level.

The front to rear weight distribution has shifted a little more to the rear and you can really feel it in the steering wheel - it doesn't "plow" into the turns anymore.
The car actually goes around corners VERY nice now!

I also prefer the stance/look. Four door sedans never looked good to me w/any kind of rake to it.

[Dobs]

http://www.mercurymarauder.net/forums/showthread.php?t=88492

[lifespeed]

Just put the digressive/linear rear shocks on. Huge improvement over the linear valving. I'll comment further after having a little drive time on them.

I do think I am getting some stiction from the non-greasable polyurethane sway bar bushings. I think I even hear them squeaking when I bounce the rear. I will drill some zerk fittings and make them greasable.

The suspension needs low-friction freedom of movement. I recall there was a marked change in ride when I put that rear bar on, so perhaps this is a good place to look.

[Mr. Man]

How old are the bags? I doubt a person could tell the difference but I imagine as the bags get older they may harden up a bit, slowing down the cush feel.

[lifespeed]

How old are the bags? I doubt a person could tell the difference but I imagine as the bags get older they may harden up a bit, slowing down the cush feel.

The air bags (like everything else) are new.

[Mr. Man]

I figured as much considering all that you've been doing, was just a thought. :)

[lifespeed]

I drilled and tapped the factory sway bar brackets for grease fittings. There was evidence of friction on the bushing surface, not to mention squeaking. All better now.

When I had the sway bar disconnected from the stock end links I noticed only 1-1/2" to 2" of compression would put the sway bar in contact with the rear diff cover. So this is likely the "hard stop" I have been hitting on occasion.

I thought the factory end links were a little nicer than the aftermarket ones, so used the factory stud with the poly bushings. I did not think to check the overall length. Oops. The Addco links are shorter, which is what would be needed to prevent this contact. Also, this is the tubular bar which has a different shape than the solid bar. Already had to replace the exhaust to get the driver tailpipe off the sway bar. :rolleyes:

Too late to crawl under the car again tonight, I'll put them in tomorrow.

[MOTOWN]

The oem rear end links dont come close to the quality (or size) of Energy suspension end links, which is what i used to pull my Addco bar further away from my aftermarket rear diff cover.

[lifespeed]

So the stock end links are too long for a lowered rear end and Addco #2271 tubular sway bar. The sway bar would hit the cover partway into compression travel acting like an early bump stop.

Not to mention the sticky urethane bushings that need to be modified for a grease fitting.

So now the rear moves freely and the car rides the best so far. I can easily move the rear up and down using my foot on the trailer hitch. And the ride is pretty good. Handling is awesome! Better than a big old heavy car has any right to. Reminds me of the old '70 GTO.

Now that the suspension movement is resolved, I'm back to examining shock valving. For that, I'll post shock details in the shock thread (http://www.mercurymarauder.net/forums/showthread.php?p=1329064#post1 329064)if anyone is interested. Cliff notes version: very close, but still a little too much rebound and the piston should be digressive/digressive instead of digressive/linear. Sigh . . . so close.

Edit: after further review, it appears likely digressive/linear is indeed correct.

[BUCKWHEAT]

but trash the Penske shocks and the poly bushings. I had harsh ride before and after putting on the Metco Watts & rear control arms. I did have adjustable Tokiko shocks. I went to the Monroe step-up quality hd shocks & immediately noticed a dramatic improvement in the ride. Wife loved it & it made no difference with my 60 foot times. The ride is best with the OEM equivalent tires, but gets a little worse when I put on the summer DOT drag radials.

[lifespeed]

but trash the Penske shocks and the poly bushings. I had harsh ride before and after putting on the Metco Watts & rear control arms. I did have adjustable Tokiko shocks. I went to the Monroe step-up quality hd shocks & immediately noticed a dramatic improvement in the ride. Wife loved it & it made no difference with my 60 foot times. The ride is best with the OEM equivalent tires, but gets a little worse when I put on the summer DOT drag radials.

You posted at the end of this troubleshooting thread which concluded it was sway bar friction and binding. It is all fixed - rides and handles great. Thanks for sharing the experiences on the Monroes. Of the few off-the-shelf options, many people appear to be satisfied with them. But $40 Monroes can't hold a candle to properly-valved race car shocks.

I think the Metco's contribute little harshness but a great deal of rigidity and are a good trade off in ride quality for performance. It also appears they move freely without binding and make a greasy mess under the car.

At the moment I am happy with the car, it's better than new and takes corners much faster and sure-footed with a smooth but well-controlled ride

[RKHiPerformance]

...I think the Metco's contribute little harshness but a great deal of rigidity and are a good trade off in ride quality for performance. It also appears they move freely without binding and make a greasy mess under the car...



The Metco parts use a much stiffer control arm body, as well as a much stiffer bushing at each attachment point. The intent is to reduce the flex in the links so the springs and shocks can do their job properly. A secondary result of the stronger materials used in the control arms is a slight increase in road feel.
The poly we use in our suspension components represents the best in this technology, and we have found that it works exceptionally well in applications like the Panther. Based on the description of your search for optimum ride quality, I'm glad you resisted the temptation to replace the poly bushings with Delrin.

Good thread...Congrats on the resolution.
:beer:

[lifespeed]

For those who install the tubular Addco #2271 (http://www.neverenoughauto.com/p-6125-addco-rear-anti-sway-bar-2271.aspx) tubular rear sway bar, here is the rundown on sway bar links. I can't comment on diff/bar interference with the solid #650 (http://www.neverenoughauto.com/p-6123-addco-rear-anti-sway-bar-650.aspx) rear bar, but suggest you look at it during install by pivoting the bar with the suspension loaded, end links disconnected and observe the bind point.

Addco-supplied links, part number unknown. About 4.9" center-to-center. Possibly OK at stock height. I am lowered with the fender lip about 1/2" above the stock tires so these would provide a "sway bar bump stop" when the diff loop hit the cover under compression.

Energy suspension 9.8118 about 4.4" center-to-center. Probably a better idea for slight or no lowering. Should keep you from bottoming.

Energy suspension 9.8117 about 4.1" Correct height for lowered cars. Have not experienced any binding with these links. Note these are too short for stock-height cars.

[justbob]

I used 9.8121 on my lowered car without fail until I added my girdle cover. I then could see it was making contact and bottoming out. Since I am a cheap azz, I simply put a die in the vise and doubled the threads and cut about an inch or so out of the spacer and reinstalled. Problem solved in under 10 minutes. While under there I also added 1" lateral locks to keep the bar centered as it favored the passenger side by a out 3/8", which is why it was rubbing only the drivers side.

I would imagine either fix would have solved it, but only wanted to look at it once. I almost forgot just how good of a ride she had.


Self proclaimed Builder Of Badassery.

Buy it, Break it, Build it BETTER.
"Since 2004"

[lifespeed]

I would imagine either fix would have solved it, but only wanted to look at it once. I almost forgot just how good of a ride she had.

Had? Which shocks do you use?

[justbob]

Had? Which shocks do you use?

Monroe. Rides like a caddy. They handled Atlanta Motor Speedway at 95 all the way up the wall and the car begged for so much more. Damn driveshaft vibration kept me from well into the triples that the rest of the car had zero issues conquering. I was ready to fall asleep from boredom. Seriously, it felt like a Sunday drive.

So yes, had. I had been driving with the harshness for a couple months. Glad to have a nice smooth lowered ride again.


Self proclaimed Builder Of Badassery.

Buy it, Break it, Build it BETTER.
"Since 2004"

[lifespeed]

Monroe. Rides like a caddy. They handled Atlanta Motor Speedway at 95 all the way up the wall and the car begged for so much more. Damn driveshaft vibration kept me from well into the triples that the rest of the car had zero issues conquering. I was ready to fall asleep from boredom.

Don't you have enough power that your car would still be plenty fast with 3.55 gears?

[justbob]

Probably so. My issue stems from a design flaw in the shaft and trusting driveline shops with their "experience". I have now been to three different shops in two different states and they just lay blame on the last shop, and take my money for a rebalance. Hell, the one I went to in Atlanta showed me the shaft before and after on the lathe to calm me and took down all my specs to put together a price for their race version. I even mentioned at this point price don't matter.. Did they ever call me with the info? Nope.
I am going straight to Mark Williams and probably Denny's as well and let them have a crack at it now. I wouldn't even mind going to a two piece if needed. I'm open to suggestions. All I know is this style the others keep pushing me obviously won't work. One spirited run up to 4th and it deflects just enough to not return and I get the dreaded shakes again. I agree when they claim this shaft is good for almost 2 thousand HP, but probably best in a truck crawling up rocks, but not in 490 pounds of torque up past 100. 3rd doesn't even hit 6000 till around 118.

I'll get this figured out after I've had some rest. At least everything else has held up rock solid with zero signs of wear.


Self proclaimed Builder Of Badassery.

Buy it, Break it, Build it BETTER.
"Since 2004"