Can coil overs make my 3-Series ride like a 5-Series?

Howdy all,

I drive a 2016 BMW 328i xDrive with the standard suspension.

Can coil overs give my car the suspension comfort typically found in a larger car, such as a newer 5-Series, or older Lexus LS 430, for example?  Or even the ride and compliance of an economy car from the early 2000’s (something with lots of suspension travel that soaks up road imperfections)?  Basically I’m looking for less road imperfections to be transmitted to the body of the car – the idea being have the suspension to more of the work.   I’ve developed a medical condition (issue with my cerebellum) where quick up and down movements, like washboard roads, or re-occurring freeway expansion joints can totally whack me out.  

My hope is that a smoother ride is possible – and as my health improves I can firm up the suspension, as I can tolerate more body movement.  And if my health declines again, I can adjust the suspension for a softer ride.  I don’t care about lowering the car, and I’d rather not lower it, if possible -- but I’m guessing that any coil over kit I find will probably lower my car at least 10mm or so, which I can live with.  I still need some decent clearance though – as I live on a gravel road and my driveway is also decently banked.  

I already tried a softer shock in the rear of the car, which improved things about 10% -- but I need a little more compliance, still.    It seems logical to me that coil overs should be capable of this, although I realize what I’m trying to do is a bit unconventional – most people want to drop their cars and sacrifice ride comfort for handling.  Whereas I’m willing to sacrifice some handling for ride comfort, if necessary.

I’m hoping to find an off the shelf coil over system, as I’m guessing a custom coil over setup would be out of my price range.  I was hoping to keep it in the $2000 to $2500 range but could spend more if needed -- I'm really not sure what I need.  Of course, if something cheaper will accomplish my goals then even better.  

Any recommendations?   I’m not familiar with what brands and models would work best to accomplish my goals.  I’m guessing I’d want a coil over that lets me control both compression and rebound?

Thanks for all the help,

-Nathan
 

Unfortunately, I think you'll find that coilovers generally have significantly higher spring rates than the factory setup.  Ground control may be able to help you if you give them a ring, as they (last I heard) are still quite happy to discuss custom/unusual applications.

What wheel size/aspect ratio are you running?  

Assuming factory/rubber bushings? 

FWIW, my e39 was incredible on washboard dirt roads compared to anything else I've driven.  It would be tough to duplicate in a smaller car with less integrated isolation. 

Are you running stock run flat tires? If so, simply swapping to regular tires, preferably all season instead of performance summer,  can pay big dividends in ride comfort. 

More/softer sidewall

No, but it can make it ride like a riced out Civic.

Figure out what the smallest diameter wheel is that will fit the car and get the largest sidewall tires that will give you an overall package with the same diameter as stock. Sidewall will soak up road imperfections. And get tires described as "touring" from a well known brand. 

Coil-overs aren't exactly what you're looking for, but not because they can't help. It's a little bit like you're saying "My stove cooks food too fast, so would a new stove help?" Maybe, but what you really need to do is turn the heat down.

In your case, you need to lower spring rate and likely increase travel. And coil-overs could be a tool to do that, if only because they usually take standard springs that can be easily tuned to your application, and often have shocks that can be softened to match.

In your situation, I'd try to put small wheels/big tires on first (and get rid of run-flats). Then, I'd see if there is any parts-bin suspension stuff that could soften the car up. Next, I'd see if the springs are a generic enough format that something else can slot in there. Only after that, I'd do the math and order some coil-overs to hopefully increase travel and soften things up.

Full disclosure: It's probably cheaper and easier to trade for a 5-series. 

I had a pickup truck that rode too rough after back surgery.   I ended up putting bags of cement at the backend corners of the bed and they made the ride a lot more comfortable.  (someone lifted them for me).

My e39 540i with the sport suspension was one of the stiffest cars I've driven lol. 

I'd probably look for a Crown Vic or Town Car, cheaper than getting new wheels for you car. 

Nathan JansenvanDoorn said:

Unfortunately, I think you'll find that coilovers generally have significantly higher spring rates than the factory setup.  Ground control may be able to help you if you give them a ring, as they (last I heard) are still quite happy to discuss custom/unusual applications.

Seconded on consulting Ground Control. 

And coilovers don't have to use a higher spring rate. A setup like Ground Control's uses Eibach springs which can be anywhere from 100 lb/in to 2000 lb/in.

Yeah you can put soft springs on coilovers, but unless the dampers are way soft or have a ton of adjustment range it's just going to make the car stiff in a different way. Some custom valved dampers would help but you're probably looking at a few iterations to get something better than stock. Bushings and tires are a big part of small input nvh like you're talking about too, which coilovers aren't going to help with.

Thanks for the replies, all!

I'm running 225/45 18 inch regular go-flat tires.  I appreciate the suggestion to go to a smaller wheel with a higher sidewall, but I know that isn't going to give me the compliance I want -- have tried 17 inch wheels on this car already.   I've tried putting a bunch of weight in the trunk too, but haven't noticed a very big difference in ride quality either.  

I did try a softer rear shock already -- was able to put a previous year's 3-series shock on, before the mid-cycle refresh, where they returned them (and made them harsher).  Like I said, it did help things noticeably. The softer rear shock is close to working -- I just need a LITTLE more compliance, still.

It sounds like the best thing would be to do a consult with Ground Control -- I'll start heading in that direction -- thanks!  

-Nathan

For starters, I've never heard of any OEM 3-series shocks being considered the best option for ride quality. I've frequently heard of the right shocks improving both ride and handling over stock. For your application, I would be looking at the Koni Special Active with the stock springs as the 'best' available option, but still may not be enough to get you where you want to be.

The problem with taking it further is that softening springs means you also need some way to allow for added travel. On stock type suspension, that won't work because BMW uses the bump stops as an integral part of the suspension, going so far as to call them 'auxiliary springs' , not just to stop excess travel. It provides a strong rate progression, and allows them to run less suspension travel. Since you've hardly got any travel before hitting the bump stop, softening spring will just mean you'll have slightly softer initial travel followed by a harsher ramp in stiffness as you rely more on the bump stop.

Cutting the bump stop shorter may help on smaller bumps, but also may actually makes this effect even worse on larger bumps. Some people seem to also have had luck with shorter bunk stops from other BMW's.

BMW design constraints limit your options for shock travel with coilovers, as well as spring travel before bind. It also typically means going to a traditional bump stop. While shorter, freeing up potential shock travel, it's barely enough to compensate for significantly increased rates... Let alone reduced rate. I put considerable effort into custom spec-ing the coilovers for my 128i, and simply cannot make the numbers work for what you're asking. I doubt the results would come out any better on an F30 chassis, especially an xdrive which I believe may add even further constraints.

In reply to Driven5 :

Thanks Driven5. 

It sounds like you're pretty familiar with BMW suspensions.  Maybe there's something I'm misunderstanding about the suspension on my particular car though: It seems like there's room for a decent amount of suspension travel to me.  I've heard of BMW using the bump stops as part of the suspension on their newer cars but I'm pretty sure I'm not hitting the bump stops on mine.  I know the issue I'm experiencing with motion being transmitted into the cabin over washboard roads or broken pavement is not hitting the bump stops -- some of these ripples in the pavement are just too small to do that.  I don't think I need a ton more suspension travel than what I already have to solve my problem, as the softer (pre-LCI) shock in the rear helped a decent amount already.  And, yes, x-drive adds a complication in regards to going too low, but I don't want to go any lower than necessary, anyway.  

In reply to natesi :

Let's find out...

Go out to your car. Turn the wheels to full lock. Pull back the bellows covering the bump stops. Tell me how much of the shaft you see on each shock.

Parking the car on a slightly raised surface with the rear tires near the edge should allow you to crawl underneath to do similar for the rear shocks.

The bump stop is absolutely an active part of the suspension on that car...and basically any car designed since about the 1990s or maybe even 80s. I'd be surprised if there's much more than an inch of suspension travel before the stops engage. You might be able to solve your specific issue, but the problem is that you're going to push the issue down the road. You can fix the small impacts, but it's going to be at the cost of making medium and large impacts much harsher and probably adding some weird handling effects as well.

If the car is using the bumps most of the time, the solution is stiffer springs and appropriate shocks. That'll mean less time spent on the stops. It seems counterintuitive, but it works.

My wife's f31 wagon is quite softly sprung. I wonder if the wagon springs are softer or the longer wheelbase on the wagon helps here. 

Might be worth researching the wagon spring rates. Hers is 328xd, not sure if the rear differs much from the sedan, but the front should be the same. 

In reply to Driven5 :

I was unable to lift the rubber boot up with the car on the ground -- but I did poke the outside of the boot to find the top of the strut body and the bottom of the bump stop.  It seemed like there was only an inch or so -- which seems crazy.  I pulled the bump stop and attached bell housing down at the rear of the car and it only traveled about an inch and a quarter before it touched the top of the shock body.  So not much room before hitting the bump stops in these.  But the bump stops are long in both cases, too.

I found a thread below, where Fortune Auto says that the F30 chassis has 97mm of shock stroke in the front though -- which is like 4 inches.  That must be including the travel of the bump stop area, as well -- the bumpstops at the front of the car are quite big (see pic I found from youtube video).

F30 post quoting Fortune Auto's 97mm of shock stoke: https://f30.bimmerpost.com/forums/showpost.php?p=26658886&postcount=62

Someone also mentioned Fat Cat Motorsports -- which can build a custom set of coil overs with different technolgies added on, ala carte ("ripple reducer" and/or "kerb blow off").  As of 2020, it sounds like each coil over could be built for about $450 with "ripple reducer" (probably what I need).  But that doesn't include the price of the actual coilover bodies and hardware.  So a person would have to buy new Bilsteins or, if they are lucky, buy an old pair for cheap and have FCM rework them. https://f30.bimmerpost.com/forums/showpost.php?p=26664133&postcount=73

The main downside is that to explore what FCM can do, and if it will be viable on your car, you have to pay a $125 consultation fee, first.

In reply to Slippery :

It depends on the year of the F30.  Pre-LCI had softer shocks and struts, at least in the sedan.  I already put a pair of pre-LCI shocks in the rear, which helped a bit, but not quite enough.  

In reply to natesi :

Shocks are there to control the springs. Cutting the damping might help (especially if BMW has overdamped the car to give the illusion of a sporty ride), but usually you'll want to change the rate and then shocks to match.

I'd stay away from Bilsteins, regardless of valving, if ride quality is the primary goal. They tend to have a lot of high frequency noise in the ride, we call it "the Bilstein jiggle". 

In reply to Keith Tanner :

Good to know -- thanks!

In reply to natesi :

I'm actually surprised you have a whole 1 inch of free travel. Normally it's claimed to be closer to 1/2 inch, and for some chassis the rear are even claimed to be on the bump stops at factory ride height. Most of those are 'sport' suspension though, so I guess your 'standard' suspension doesn't get proportionally longer bump stops.

The 97mm quoted by Fortune Auto appears to be their own coilover stroke, not the factory stroke. Otherwise, with the ~3.25" F30 bump stop and only a little over half an inch of free bump travel, there would be ZERO remaining for droop travel!

You need wheel travel to get a good ride. Stock E8X/E9X struts have a little over 5.5" total stroke, and that isn't very much. That's not just bump travel, that's total shock travel. Split some percentage to droop, some percentage to bump, and some percentage to the bump stop. The soft spring rates BMW uses would naturally require ~6" of travel just for the unrestricted droop, plus something like that again for bump to be unrestricted and kept off the bump stop. So they run a bunch of preload, a soft spring rate for a tiny amount of travel right around ride height, and a huge bumpstop that is engaging so much of the time people can't even tell when it is/isn't happening.  

So the long bump stop is already functionally increasing your spring rate much of the time. This is why Keith mentions that increasing spring rate (without bump stop interaction) can actually improve overall ride quality when combined with the right damping. However, I'd caution that to go for free travel rather than tuned active bump stops you'll still need it enough stiffer that it will be overly firm (even if not harsh) for what you're asking. Based on my E8X/E9X experience, I'd guess you won't be able to go much less than double the factory rates (and stiffer than even M3/M4) without the custom struts being so long as to substantially lift your car, and even then also ending up with the same spring bind problem that FA talks about.

The 'ripple reducer' blow-off on the FCM shocks is the reason I recommended Koni Special Active for an otherwise stock suspension, as they have a similar blow-off functionality.

After having put extensive effort into mathing out the specs for the custom coilovers that allowed softer (but not soft) front springs on my 128i than any other reputable coilover offering without losing functionality, I strongly believe the chances are quite high of spending a lot of money on something likely to still not suit your needs or make you happy. Personally, if set on sticking with the F30, I would start with Koni SA's and then start looking at shorter bump stops options to try tuning with them. It still has its shortcomings, and will just as likely take considerable time/effort to dial in via trial-and-error with no guaranteed payoff, but at least that way the cost of failure is lower.

Beyond that, you'll be time and money ahead by just looking for a 5-series or Lexus LS430 that you can drive as for long as this issue persists, then selling for up to (less than) a $2k loss. If it's really just short term, you might even be able to pick up a Panther chassis car for similar to what you're talking about spending on a big experiment, and just light it on fire when you're done with it.

Driven5 said:

The 'ripple reducer' blow-off on the FCM shocks is the reason I recommended Koni Special Active for an otherwise stock suspension, as they have a similar blow-off functionality.

Similar, but much more effective (the koni system that is).

In reply to Driven5 :

Thanks for all the time, effort, thorough, and thoughtful responses - much appreciated.  

I've been doing a lot of reading on the Koni Special Active for my car.  It's hard to draw conclusions on this shock's behavior, as there are at least 3 different suspensions for the F30 sedan -- and on top of that almost no one is changing to just the Koni SA shocks -- everyone seems to have changed springs along with the Koni SA shocks.  With so many variables it's very hard to interpret the changes people are reporting -- although most reports are good.
Overall, it sounds like they are described as firm, but they remove the small imperfections and ripples out of the road.  I'm a bit concerned with the "firm" aspect, but removing the ripple effects and small road imperfections is what is driving me crazy and whacks-out my cerebellum the most while driving.    

I agree - this is probably my best bet.  

Bump stop tuning is interesting – maybe something I could even try before the Koni SA.  If I do decide to cut my bump stops, there's no way to "glue it back in" is there?  I’m asking because taking the struts out to replace the bump stops seems nightmarish.  xDrive adds more difficulty to removing the struts as well.

PS: I'm not particularly attached to my F30 2016 328i xDrive.  It's just that the miles are low (52K), I've had the car since new, there’s nothing wrong with it, it's paid off, I know the history, and it's been insanely reliable (oddly enough, for a BMW).  The only issue I've had with the car is that a rock broke out one of the auxiliary coolers on the freeway -- which isn't totally the car's fault, although the bumper inlet leading to the auxiliary cooler will let anything just under the size of a golf ball, in there.  So: Really stupid design.  Other than that the HVAC use to have a mind of it's own when not on "auto" but I had the dealership flash the computer under warranty and that took care of it.  I know oil leaks are coming though -- not delusional to the maintenance costs ahead of me.  = )    

But the thought of getting an old used car is a bit scary to me.  I've been seriously considering it but it's a bit of a wild card.  Even the most reliable cars can be money pits and huge time wasters if you get a bad one.  Like, how do you know whatever used car your buying doesn't burn 2 quarts of oil between oil changes; how do you know the trans won't go out next week; how do you know they didn't dump in 60 weight oil to hide rod knock; how do you know there's no intermittent electrical issue the previous owner couldn't solve, etc?  The other thing is: No one wants to play ball with my trade-in.  They don't dispute the value of the trade or that the car isn't in great shape (I take excellent care of my stuff).  They just say they can't make money off it -- as the retail vs trade delta isn't big enough.  If my current car got totaled, I'd risk buying an old LS 430, panther platform car, or something like that -- maybe I still will.  Just feeling the financial pressure of skyrocketing medical bills and loss of income from health issues -- so a bit risk averse to buying another car.  I'll spend at least 17K this year on health expenses at a minimum -- more likely $25K, or more.  With savings evaporating quickly, I can't afford to have two cars at once, unless it was very temporary (like selling the BMW after I get something different).  

Thanks again for all the help!
-Nathan.