UPDATED: Replacing Rear Shocks: Reducing the rear end bounce.

[HuntingPudel]

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<SNIP>
Again, with such a short suspension travel that the MME has, going with softer springs means the car will bottom out very easily which is not a good thing. I think the springs that the car is designed with are ok for the weight it potentially needs to carry. It’s the shocks that need to be improved on. I have the GTPE with the Magneride active shocks and in the unbridle mode where the shocks are at their most firm setting, I get very little bounce.
<SNIP>

Yep. The guy from whom I learned the most about suspension (who was a GM engineer who took his wife’s 7 year old grocery getter into a competitive SCCA Trans Am race car - see my avatar) did not that the job of the springs is to support the car without bottoming. The job of the shocks is to control motion over undulations. Ford failed at the job of the shocks.

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[azerik]

I'm assuming the reason Ford failed with this was not fully grasping the design changes of the rear suspension on this car. I believe it's the first time so much rubber tensioned parts were put in one place. The front suspension has 2 rubber mounts. The very large doughnut hinge in the back of the lower A-Arm and the front pivot for that. The reason the front pogo's is theres just not enough weight and travel for the struts to do their thing. The rubber bushing'd factory sway bar also adds sprung tension. When the front bar is swapped out the front suspension can move slightly easier. If I had to guess it's seriously maybe 25 to 50 lbs less tension, the equiv. of moving 1 hole on the Steeda bar. It's not enough to make a noticeable difference I'd think.

The back has 9 points of rubber tension (or more, I've been off my game as I havn't been under the car for a few weeks because, well I can drive it and don't have to fart around with it daily anymore, plus it's nearly in the 100's here and that sucks for garage time) PER SIDE. Slowing down that amount of rebound is tough, even with nearly 2500lbs of weight. They built those bushings to last 100k. In return we got the ride we got. If these were on sealed bearings the springs/shocks would do much more of the work.

Putting weight in the trunk is putting more of that 2500 +(whatever you toss back there) over the rear wheels, thus slowing down the rear more. Passengers are in the balanced zone so all 4 wheels take a bit of that weight distro. However if you get into an accident with 250 lbs of sand (or shot) that becomes a 250lb projectile. Not sure the back of the back seat will protect you.

 

[dphunky]

I finished the koni rear replacement project on my premium extended range a few weeks back and tested the ride a bit before sharing my thoughts here. It definitely improves the ride in the back and reduces the oscillations dramatically compared to stock. As others mentioned, it is still a firm sporty ride but after the initial bounce, the konis absorp the subsequent bounces. I now notice the front bounce though now that the rear shocks have improved. I'm still on stock sway bars and did notice a slight improvement on the side to side movement in the rears.

Install was super simple with the instructions from @markboris and video from @azerik as long as you have the right tools. Thanks for everyone's hard work and testing with this. If anybody needs help in the east bay with this mod just let me know.

 

[markboris]

Thanks for another positive review of the Koni's and I'm glad they worked out well for you as it really does depend on the type of roads you drive on. Every time I see comments like this it makes me want to start working on getting some fronts going. I may start looking into this now. I have had a couple of member message me and would help me with any welding of brackets that would have to be added to the strut for the upper sway bar end links. Modifying front struts to work will not be nearly as easy as the rears were.

 

[azerik]

Just drove my RX for the first time in months. Yeesh that thing needs sway bars and rear shocks lol.

 

[HuntingPudel]

<SNIP>
However if you get into an accident with 250 lbs of sand (or shot) that becomes a 250lb projectile. Not sure the back of the back seat will protect you.

This is one of the reasons that most sanctioning bodies require that race car ballast is solid and encapsulated in the chassis of the car: Less chance of a projectile (either internal to the vehicle or external).

 

[phidauex]

I ordered parts and plan to do the swap in a few weeks when I get some time in my shop. Thanks so much for all the research, and the details down to the part number! Swap itself looks straightforward and I'm well equipped with step drills and the like for the necessary modifications. I've got 20k miles on my stock struts so I'm going to modify my stock mounts rather than order a 2nd pair - don't see myself swapping right back.

I'll report back once I've given it a go - I know my candidate bouncy roads around here...

 

[markboris]

I ordered parts and plan to do the swap in a few weeks when I get some time in my shop. Thanks so much for all the research, and the details down to the part number! Swap itself looks straightforward and I'm well equipped with step drills and the like for the necessary modifications. I've got 20k miles on my stock struts so I'm going to modify my stock mounts rather than order a 2nd pair - don't see myself swapping right back.

I'll report back once I've given it a go - I know my candidate bouncy roads around here...

Hey Sam, one thing of note that I have run into on a few cars is some play in the lower shock mount. I stated in the parts list to get two 1/2" washers and use them as spacers on either side of the lower mount when running the bolt through the lower control arm. There have been a few members that have had knocking noises due to not being able to tighten the bolt tight enough because even with the two washers (spacers) it does not quite fill the gap. Basically you may need a third washer that is thin to take up the space. Adding one extra regular thickness washer may not fit (too thick). I recently did this on John's car and this Sunday doing the same on another members car. Bottom line is once the lower mount is installed with the bolt not tightened, you don't want any side to side play or movement. If there is, add a third thin washer.

 

[txaggies07]

Hey Sam, one thing of note that I have run into on a few cars is some play in the lower shock mount. I stated in the parts list to get two 1/2" washers and use them as spacers on either side of the lower mount when running the bolt through the lower control arm. There have been a few members that have had knocking noises due to not being able to tighten the bolt tight enough because even with the two washers (spacers) it does not quite fill the gap. Basically you may need a third washer that is thin to take up the space. Adding one extra regular thickness washer may not fit (too thick). I recently did this on John's car and this Sunday doing the same on another members car. Bottom line is once the lower mount is installed with the bolt not tightened, you don't want any side to side play or movement. If there is, add a third thin washer.

Thanks for the info. I should be installing mine in a few weeks when work calms down a bit.

 

[mkindler]

Mark - thanks so much for your research and work on this. Very much appreciated.

I just had my local shop (Westchester, NY) install the Koni rear shocks as you specified. The bounce and control in the rear have been significantly improved. I don't hesitate to go over any bump in the road and the car recovers very quickly - very much more of a "together" feeling. What I did notice more than before (similar to other posts) is the slight bounce in the front. Perhaps the rear bounce prior to the change was the dominant feel and that is why I never really felt the front bounce. In no way is the front bounce of the same magnitude as what the rear bounce was. Very happy with having this done.

I still have the stock tires (Primacy AS 225/55R19) and will be playing around with the tire pressure (35 vs 43) to see if either extreme option can quiet down the front bounce without increasing any harsh aspect of the road. Interested to to hear if any other members who have installed the rear Koni shocks have tried experimenting with the tire pressure with regards to the slight front bounce.

Thanks !

 

[azerik]

What I found with the 19's was deflate the front, but leave the rear higher. If you deflate the rear too much the shocks don't work as much due to the tire taking the role of suspension. The front is annoying still and you'll notice the bounce of it because you're no longer bouncing around and not able to see it as clearly. I had at one point in my testing gotten to about 32/36 cold. Warmed, they'd add 3 or so psi. The first few minutes of a drive is kinda like having your stock shocks on there as it's a little bouncey and sway'y.

 

[phidauex]

I did this install today, and am initially pleased with the results!

The install itself was straightforward, thanks to all the great prep work by @markboris @azerik @eidbanger and others. A few notes and tips below.

Driving impressions: I have only driven back home from my workshop so far, but it includes a stretch of concrete road that was always quite bouncy for me, as well as a few railroad crossings. In both cases I noticed an improvement right away - still a stiff/sporty suspension, but it doesn't keep bouncing and swaying after going over the bump.

The real test will be when my wife and daughter ride back there, and I'm about to take a 1000 mile trip, so will report back after more miles, but for the amount of work and the low cost of the upgrade, I'm already quite happy.

Supplies: I used the stock shock mounts (drilled out), the Steeda bump stops, and spacers from https://www.extsw.com/.

The spacers are available in 316 stainless, and I went with these sizes:

• (2) 1/2" ID, 3/4" OD, 5/8" long: https://www.extsw.com/collections/1...g-304-stainless-spacer-standoff-free-shipping
• (2) 1/2" ID, 3/4" OD, 1" long: https://www.extsw.com/collections/1...-x-3-4-od-x-1-long-316-alloy-stainless-spacer
• (4) 1/2" washers (NOTE: I didn't end up needing them - see below): https://www.extsw.com/products/exts...washer-free-shipping-1?variant=31899909029942

The assembly of the shocks went as described in the OP. I used a step drill on a short extension to drill the 1/2" hole in the shock mounts (lube it with a bit of oil first), and a small pair of nippers to "fix" the plastic dome. I did put a small dab of RTV on the adjust tab after adjusting - if I ever need to adjust again it will pop free easily.

An air impact wrench makes short work of the bolts. The first side took me 1 hour, start to finish, the 2nd side took 20 minutes since now I had the routine and all the tools out on the bench.

A few tips to make the assembly easier:

1. Air impact wrench, baby.
2. I did NOT need the additional 1/2" fender washers - my shocks came with two conical washers each (pic below), and the two provided washers exactly filled the space in the lower shock mount, no additional spacers needed. I had 4 thick and 4 thin spacers, and now maybe I can make a necklace or something with them.
3. Re-assembling the lower shock mount is the trickiest part, but there are tips that help. My recommended process is:
   1. Put the shock assembly in place, and thread the two upper bolts in about 90% of the way, but where the shock can still swing and move around.
   2. Put a 2nd small jack under the lower suspension arm, and lift it up slightly until it aligns with the lower shock hole.
   3. Pro tip - use a dab of RTV to stick the washer onto the lower shock mount! But even if you didn't do that, slide the front washer into place, and slip the bolt into it. If it is being finicky, slip a small screwdriver in first from the other side to hold the washer in place, and then feed the bolt through.
   4. When the bolt is halfway in, slide the other washer into place, hold it there with the screwdriver shaft, then push the bolt the rest of the way through.
   5. Thread the tabbed nut back on, and thread the bolt to hand-tight.
   6. Release the 2nd jack, torque the upper bolts, then torque the lower bolt (81 ft-lbs).
4. While this is technically possible with the wheels in place, it is so much faster with the wheels off. Just do it right and remove the wheel.

All told, it was about the easiest shock swap I've done, and as long as you have an impact wrench, a good torque wrench, and a few sizes of extensions, you'll be good to go.

Drilling out the stock shock mounts. Step drill (a short extension will be needed in most cases), and a little lube for good measure.

Shock assembly back in place, you can barely see the dab of blue RTV over the adjuster tab (after adjusting, of course).

Lower shock assembly in place. You can see the conical washers in place.

My shocks came with two of these conical washers each. They were the perfect size for the shock mount, no additional spacers needed. Maybe they weren't included in some people's orders?

Tip for aligning the lower shock mount. The upper is threaded 90% of the way in but can still swing around. Use a jack to lift the lower suspension arm about 1/2" until the hole is perfectly aligned.

 

[markboris]

Thank you Sam for the compliments and the additional install info and photos. Glad this has helped smooth out some of the bounce for you.

About the conical washers that come with the Koni's, I had tried them out but found after a period of time with the suspension moving about as it does, the washers would actually flatten out a bit creating a space and would start to cause a knocking noise. This is why I went with flat washers so as not to have any issues down the road. I have seen slightly different thickness of those conical washers supplied with the Koni's and maybe you will have better luck than I did with them.

 

[phidauex]

About the conical washers that come with the Koni's, I had tried them out but found after a period of time with the suspension moving about as it does, the washers would actually flatten out a bit creating a space and would start to cause a knocking noise. This is why I went with flat washers so as not to have any issues down the road. I have seen slightly different thickness of those conical washers supplied with the Koni's and maybe you will have better luck than I did with them.

Ahh, uh oh… Well, in my case it did seem like a snug fit, so hopefully they are sized right. I’ll keep an eye out for any knocking and if I end up having to swap washers at least I have them handy, and will report back on the condition of the conicals.

 

[azerik]

When I’ve use those conical’s in the past, they usually compress down when bolting them down. The washers that Mark suggested pinch the metal, and when I’ve tighten them down in the past, they actually put marks into the washers, so there is a little bit of canter in the way that the shock lines up with the a arm. I’ve built shock mounts for the Vikings that include that 5 or so degrees of cant. They don’t work for the Koni’s as you can’t remove the metal from the rubber on the lower. (Viking development and testing is stalled due to summer, and another thread)

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