Question for people with lowered tourings

[dannyzabolotny]

Hey all,

My 540it has the rear SLS and it’s been lowered a bit all around. It has new Koni shocks all around with Dinan springs in the front and lowering links in the rear. The subframe bushings have been replaced with Meyle HD bushings a while back. All of the rear control arms and ball joints are new, and I recently got a professional alignment.

My issue is that the ride is super harsh in the rear, meaning every single bump in the road is super obvious— I can feel the tiniest cracks in the road. Bigger bumps have a lot of crashiness, like the shocks are bottoming out. I’ve cut the bump stops in half to try and get some more suspension travel but that didn’t really help all that much. The tires in the rear are new Hankooks Ventus V12’s in 275/35/18 and the pressure is usually set to around 36psi.

I’ve noticed that the rear doesn’t have much suspension travel at all— is that due to being lowered, or could there be another underlying issue? I know the air springs set the spring rate so I wonder if that’s the issue, as my air springs are ancient. They don’t leak though.

Pic so you can see how the touring sits:

[claylakem6]

I have a similar suspension......lowered 1.5", Dinan front, new Koni's & Arnott in rear although i ride on the original style 66 17" wheels. I also find sudden bumps harsh but other transitions bearable. The tires (Michelin A/S 3+) were my initial blame. Others have said the ride is better with a load. Maybe softens rebound.

[dannyzabolotny]

Interesting... I swapped on some 17" style 32's to test it out and the ride quality wasn't much better, so I don't think it's due to the 18" wheels. I generally have the cargo area empty, but over the past few days I've had about a hundred pounds of stuff in the back, hasn't really changed the ride quality.

I'm wondering if the Meyle HD subframe bushings stiffen the rear up too much? Due to the way the touring's rear subframe attaches to the body, the subframe bushings are the only thing that connects the two (the shocks are mounted to the subframe and not the body of the car like in the E39 sedans). The Meyle HD bushings are solid rubber whereas the OEM Lemforder bushings are liquid-filled... maybe there's a reason for that.

[Dvbimmerk]

Similar setup on my end. Koni all around with H&R up front. Same harshness as you.

My new Lemforder subframe bushings go in next week. My air bags are factory.

Currently on 17” Style 32


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[dannyzabolotny]

Interesting how we all have Konis and also have this harshness... makes me wonder if the OE touring rear shocks are valved differently to compensate for the weird rear suspension setup. The Konis we're using were designed to be vertical, not at an angle...

[simmsled]

Have any of you tried adding more rebound damping?
Honestly it sounds like they don’t have enough low speed compression damping.

[simmsled]

I’m a former Indycar race engineer.
If it is shuddering, the damper is not controlling the spring and could be hitting the bump rubber on compression.
There is not much travel in the rear suspension, so this is plausible. It just depends on the profile of the bump.
Large bumps affect the low speed flow path of the damper, short moment bumps affect high speed damping circuit flow paths within a damper. You are using low pressure twin tube dampers valved for coil springs, not air springs. The compressive and recovery profile is different with air than metal. Koni Sport dampers have rebound adjustment built in, and the hysteresis profile changes as you adjust the needle.

If you are critically damped, then you will feel barely anything... if you are not, then you are either over or under damped.

So I will ask the question again... has anyone tried changing the adjustment on their rear shocks?

[dannyzabolotny]

I have my Konis set somewhere in the middle, but I will definitely try adjusting them. Koni calls it firm and soft, so I assume I should turn it to full firm to increase damping?

[blackknight530i]

I'll just add that I am also having the same harshness as Danny in my 530it/6 with new Koni Sport rears on SLS air springs and Meyle HD subframe bushings. large bumps absorb fine and smooth roads are perfect, but small bumps feel like there isn't much suspension there at all. I'm willing to take apart my rear shocks again to try increasing firmness if someone determines that fixes it. While my Ground Control rear strut is getting replaced on my M5, I'm down to the wagon being my only car, so would like to not have both down if possible.

Dvbimmerk, I would be interested to hear if changing your subframe bushings to the Lemforders helps you at all as I bought my Meyle HDs from FCP and can swap them out with Lems easily as I have the tool as well.

Danny, are you up for adjusting your rear struts for the benefit of others in this thread ?

[BimmrMeUpSnotty]

Unlike all of you guys, my wagon has the coil springs with sport Sachs, the ride is great, this car is my beater, when loaded down with junk in the back, the car rides just as good. I never bottom out unless I have 2 big gorillas posing as friends in the back seat, I have felt the rear end bottom out, and when I checked, sure enough, the bumpers did have a clean spot, telling me I did bottom out. I know I've had more weight back there, then my two buddies in the back and never bottomed out, I don't know, I guess it was the road we were on that makes the differences. I was under the car yesterday doing some inspecting, and the subframe bushings are showing signs of wear, as I have recently noticed some beginnings of crashing sounds from the rear, car has over 204,000 miles on it.

Paul, what sub frame bushing tool kit do you have? I'm thinking I'll be doing this very soon. I'm just gunna order the tool and the bushings and be done with this. Glad you guys are comparing the differences between the Meyle HD's and the Lemmys, as I was trying to figure out which ones to go with myself.

[Dvbimmerk]

I'll just add that I am also having the same harshness as Danny in my 530it/6 with new Koni Sport rears on SLS air springs and Meyle HD subframe bushings. large bumps absorb fine and smooth roads are perfect, but small bumps feel like there isn't much suspension there at all. I'm willing to take apart my rear shocks again to try increasing firmness if someone determines that fixes it. While my Ground Control rear strut is getting replaced on my M5, I'm down to the wagon being my only car, so would like to not have both down if possible.

Dvbimmerk, I would be interested to hear if changing your subframe bushings to the Lemforders helps you at all as I bought my Meyle HDs from FCP and can swap them out with Lems easily as I have the tool as well.

Danny, are you up for adjusting your rear struts for the benefit of others in this thread ?

I am dropping car off at my Indy early next week to install Lemforder bushings. I will report back with findings.

For reference, i also have set the rears to mid-way.


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[blackknight530i]

Unlike all of you guys, my wagon has the coil springs with sport Sachs, the ride is great, this car is my beater, when loaded down with junk in the back, the car rides just as good. I never bottom out unless I have 2 big gorillas posing as friends in the back seat, I have felt the rear end bottom out, and when I checked, sure enough, the bumpers did have a clean spot, telling me I did bottom out. I know I've had more weight back there, then my two buddies in the back and never bottomed out, I don't know, I guess it was the road we were on that makes the differences. I was under the car yesterday doing some inspecting, and the subframe bushings are showing signs of wear, as I have recently noticed some beginnings of crashing sounds from the rear, car has over 204,000 miles on it.

Paul, what sub frame bushing tool kit do you have? I'm thinking I'll be doing this very soon. I'm just gunna order the tool and the bushings and be done with this. Glad you guys are comparing the differences between the Meyle HD's and the Lemmys, as I was trying to figure out which ones to go with myself.

I have the same tool as Jed. It does both sedan and wagon. It's from Koch Tools.

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[BimmrMeUpSnotty]

I have the same tool as Jed. It does both sedan and wagon. It's from Koch Tools.

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Ok, Koch Tools KT20356, $255 on eBay, Thanks man!

KT20356

[blackknight530i]

Ok, Koch Tools KT20356, $255 on eBay, Thanks man!

KT20356

I think I bought mine directly from Koch Tools. You might want to get stronger screws for the tabs on the ends as the original ones tend to stretch and break under pressure (mine broke after the third set of bushings). Jed said what kind of screws to get so I bought a bunch I think. If I have a bunch of spares, I can send them to you.

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[simmsled]

I have my Konis set somewhere in the middle, but I will definitely try adjusting them. Koni calls it firm and soft, so I assume I should turn it to full firm to increase damping?

You first need to index your current adjustment.
Turn towards full soft, count how many turns you go. If it helps, count in 1/4 turn (90 degree) increments.
That is your current damping adjustment.
Next, turn towards stiff back to your current adjustment.
Give it between 1/2 (180 degrees, or 2x 1/4 “clicks” if you will) and 3/4 turn.
Reinstall.

The difference will feel similar to a stiffer sway bar on initial turn-in due to additional low speed circuit rebound damping.
Because of Koni’s adjuster, it will also give you additional high speed circuit rebound damping.
This is where the harshness should subside a bit. Air springs are more progressive by nature, so this adjustment will give more control over the spring.

Give it a shot and see how it goes.

[dannyzabolotny]

Cool, thanks for the tip! The only annoying thing is that I need to remove the rear Konis to adjust them, versus having a handy adjustment knob like with the front Konis. On the bright side it's only 4 bolts to remove each rear shock and I don't have to tear apart the whole interior like in an E39 sedan.

I'll do the adjustments this weekend and will report back.

[claylakem6]

These are the instructions that came with mine. I turned to full soft and then counter turned 360 degrees hard.



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[cheapE46]

Just for reference:
I had super crashy ride when I bought mine with old Bilstein B6 shocks and cracked out rear bushings.
Now: I have new Lemforder bushings, new Bilstein B4 touring specific shocks and Arnotte air bags. The ride height is unchanged as well. Rides super comfy on highway speeds and handles the non-abrupt bumps just fine. Still feels slightly rough on abrupt bumps and on notchy concrete streets.

[simmsled]

Cool, thanks for the tip! The only annoying thing is that I need to remove the rear Konis to adjust them, versus having a handy adjustment knob like with the front Konis. On the bright side it's only 4 bolts to remove each rear shock and I don't have to tear apart the whole interior like in an E39 sedan.

I'll do the adjustments this weekend and will report back.

Its definitely worth the try.
I’ve thought about doing some damper development on the rears.
It’s easy enough to modify a Bilstein damper for development.
If I do it, I’ll definitely start a thread.
If there is no way to get the Konis to behave, they can be revalved as well.

I installed the Rein rear subframe bushings when I replaced rear ball joints, control arms, and installed Arnott air springs.
My stock Sachs sport suspension dampers have 140k on them, but still ride smooth.
The bump rubber is shot, however, and I’ll replace in spring.

One last thing... did all of you loosen the rear control arms (bushing side) and then re-tighten at lowered height so the bushings are not pre-loaded with the new ride height?

[BimmrMeUpSnotty]

I think I bought mine directly from Koch Tools. You might want to get stronger screws for the tabs on the ends as the original ones tend to stretch and break under pressure (mine broke after the third set of bushings). Jed said what kind of screws to get so I bought a bunch I think. If I have a bunch of spares, I can send them to you.

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Hey, just saw this, thanks for the tip. I'll go get Grade 8 bolts for it. Is that what you got? They're gold colored, right? Thanks for the offer, but hang on to them, you will need them in the future, whenever you use the tool.
Same thing for frame machines, when I was mounting wrecked cars on frame machines, stretching them back and forth, after a while, the Grade 8 bolts fatigue and I would just throw them away after 8 to 10 jobs. Always had to make sure we had fresh ones.

By the way, looks like I am back in the auto body business, should be starting on Monday. Will be working specifically on BMW, Audi, Porsche, Mercs, and anything aluminum for American stuff, specifically the new Ford F150's, the shop is certified for Aluminum, apparently, there's a shortage of them, so now, if you aren't, the insurance companies will not let you touch the cars if they're all aluminum. The new F150's are all aluminum. Purty cool shop, all high end, no hoopties, you don't get so dirty by the end of the day!

Sorry for the hi jack, Danny.

[adm750]

Danny -
I may have missed this in the post as I am reading this rather briskly, but have you verified that you are contacting the bump stops ? Maybe paint the tops of those and see if it's getting rubbed off ??

I am not chiming in from my huge knowledge base regarding suspension adjustments. I'm simply noting it as a part of the process. I am sure you have already determined that you are contacting them, and proceeded to cut them down for that reason. I just don't recall that ever being stated in the threads...or if it was noted that you are still hitting the stops at times.

Forum: would understanding that part influence the thought process behind the adjustments....?

[blackknight530i]

Hey, just saw this, thanks for the tip. I'll go get Grade 8 bolts for it. Is that what you got? They're gold colored, right? Thanks for the offer, but hang on to them, you will need them in the future, whenever you use the tool.
Same thing for frame machines, when I was mounting wrecked cars on frame machines, stretching them back and forth, after a while, the Grade 8 bolts fatigue and I would just throw them away after 8 to 10 jobs. Always had to make sure we had fresh ones.

By the way, looks like I am back in the auto body business, should be starting on Monday. Will be working specifically on BMW, Audi, Porsche, Mercs, and anything aluminum for American stuff, specifically the new Ford F150's, the shop is certified for Aluminum, apparently, there's a shortage of them, so now, if you aren't, the insurance companies will not let you touch the cars if they're all aluminum. The new F150's are all aluminum. Purty cool shop, all high end, no hoopties, you don't get so dirty by the end of the day!

Sorry for the hi jack, Danny.

No, I bought Grade 10.9 bolts from McMaster Carr. I bought a bag of 100 of them and just opened them, LOL. When they broke on the first set, the screw shanks were sheared off in the arms and I had no way of getting them out, so Koch Tools warrantied them and sent me a new set of arms that have the bolts in them as well. I'll replace all the screws with the 10.9 ones and still have like 90 of them left.

[dannyzabolotny]

Its definitely worth the try.
I’ve thought about doing some damper development on the rears.
It’s easy enough to modify a Bilstein damper for development.
If I do it, I’ll definitely start a thread.
If there is no way to get the Konis to behave, they can be revalved as well.

I installed the Rein rear subframe bushings when I replaced rear ball joints, control arms, and installed Arnott air springs.
My stock Sachs sport suspension dampers have 140k on them, but still ride smooth.
The bump rubber is shot, however, and I’ll replace in spring.

One last thing... did all of you loosen the rear control arms (bushing side) and then re-tighten at lowered height so the bushings are not pre-loaded with the new ride height?

What's interesting is that my ride didn't significantly improve since upgrading from stock rear shocks at 194k miles. I installed the rear control arms after the car was already lowered, so the bushings were tightened at the current ride height. Same goes for the front bushings.

[BimmrMeUpSnotty]

No, I bought Grade 10.9 bolts from McMaster Carr. I bought a bag of 100 of them and just opened them, LOL. When they broke on the first set, the screw shanks were sheared off in the arms and I had no way of getting them out, so Koch Tools warrantied them and sent me a new set of arms that have the bolts in them as well. I'll replace all the screws with the 10.9 ones and still have like 90 of them left.

Holy crap!!! Ok, I'll reach out to you when I get the tool, will be a few weeks before I can get it, damn credit cards are kinda maxed out.right now A 100 bolts!!! Lol

[AquilaBMW]

Interesting thread. My wagon is lowered, but currently running Biltstein suspension set up front and rear. The ride was actually rather pleasant on this set even though firm. I was happy with the ride with 18' Style 65's on the car. I have recently been running 19' DINAN Wheels and the ride is certainly harsher. I am running 36 PSI up front and 40 PSI on the rears and the ride can now be considered "harsh" on bumps - but more so up front.

There is a difference in gross vehicle weight compared to your's though Danny as my wagon is currently still a 525iT and your's is a 540, so it is possible that has an affect on the ride.