[bimmerhw]

I recently feel suspension of my 340i is somewhat loose especially when braking or accelerating.(I feel it's not tight and very integrated, somewhat feel myself/or the cabin itself being dragged with a delay when braking/accelerate which is not very pleasant) besides, somtimes in bumping road, my passenger seat got some rattle.

need your suggestions should I go for a new m340i/m2/m3 or upgrading my shock absorption simply can do the job?

Since it's my first bmw so not sure exactly it's just becuase it's not an m power/or even m performance tunned car(like m240i/m340i) i've been told that the m240i/m340i even it's not an m power, it's turnned by m department so the suspension and tunning is much better than a general 2/3 series.

I did some research around shock absorption, considered KV V3 LE but it seems overkill. so seems the KONI special active looks like fit my case perfectly and it's more affordable.

any thoughts guys? thanks!

[weehe126]

You are asking if you should replace your possibly worn shocks, or buy a brand new M3? <$1000 vs $80k+.

[cfm56d7b]

To be fair to the question, what is your budget for the suspension upgrade?

[bimmerhw]

Originally Posted by weehe126

You are asking if you should replace your possibly worn shocks, or buy a brand new M3? <$1000 vs $80k+.

yeah it sounds like a little bit unreasonable.

could be a used m340i.
while tbh I am mostly unsure what's the `loose` feeling coming from.
if it's the car itself(regardless the condition wear out), I can live with it and considering buying an better one in a few yrs(not necessarily immediately)

if replacing some of those worn rubbers or simple shock upgrade can make it better, that would be even better.

I think I may repalce those worn rubbers anyway in next service, see how it goes. and got some test drives of new m cars.

[bimmerhw]

Originally Posted by cfm56d7b

To be fair to the question, what is your budget for the suspension upgrade?

within A$2000(or usd$1300) I guess for now. it's my thoughts now.
I feel KV V3 LE is too much for my 340i.

[casualDIYer]

Originally Posted by bimmerhw

within A$2000(or usd$1300) I guess for now. it's my thoughts now.
I feel KV V3 LE is too much for my 340i.

You're mixing up products a bit here. You can
a) Do an OE replace with OE parts, keeping the static settings of BMW
b) Upgraded OE with static settings (typically stiffer). e.g. Koni Active (red), Bilstein B6/B8
c) Single variable setting (typically rebound but I swear compression is also affected). e.g. Koni Sport (yellow), BC, KW V2, Bilstein B16 (PSS10)
d) Dual variable settings (rebound + compression), KW V3, Ohlins
e) Multi-variate settings but this would be overkill for a street car

If you are primarily a city street/highway driver, a) or b) will be fine. If you do the occasional track/autoX day, you might want to go with c) but if are really interested in getting even more accurate settings for application then go d).

The price rises for each of these options, with a) the cheapest and d) the most expensive.

If you really want the car to have a more comfortable ride, get rid of the runflat tires (if you use them) and consider a wider tire and rim. BMW has to practically use pillows as suspension to hide the terrible ride quality of run flats.

[SpencerC_6MT]

You can definitely fix it with a suspension upgrade. I'd suggest you look into subframe bushings first, then control arm upgrades if it's still not where you want to be. Shocks do wear with time, but unless they're leaky, it's not the first place I'd look.

[bimmerhw]

Originally Posted by casualDIYer

You're mixing up products a bit here. You can
a) Do an OE replace with OE parts, keeping the static settings of BMW
b) Upgraded OE with static settings (typically stiffer). e.g. Koni Active (red), Bilstein B6/B8
c) Single variable setting (typically rebound but I swear compression is also affected). e.g. Koni Sport (yellow), BC, KW V2, Bilstein B16 (PSS10)
d) Dual variable settings (rebound + compression), KW V3, Ohlins
e) Multi-variate settings but this would be overkill for a street car

If you are primarily a city street/highway driver, a) or b) will be fine. If you do the occasional track/autoX day, you might want to go with c) but if are really interested in getting even more accurate settings for application then go d).

The price rises for each of these options, with a) the cheapest and d) the most expensive.

If you really want the car to have a more comfortable ride, get rid of the runflat tires (if you use them) and consider a wider tire and rim. BMW has to practically use pillows as suspension to hide the terrible ride quality of run flats.

Thanks! I still prefer not lowering it, so not much choice. I did find some very good feedbacks about KONI active so thinking of it and it's much cheaper than KV LE.

Also mostly drive on street and occassionally on track, so sounds like KONI active is enough.

[bimmerhw]

Originally Posted by SpencerC_6MT

You can definitely fix it with a suspension upgrade. I'd suggest you look into subframe bushings first, then control arm upgrades if it's still not where you want to be. Shocks do wear with time, but unless they're leaky, it's not the first place I'd look.

thanks! that's exactly what my mechanism told me too.
will check those first before replacing shocks.

[bimmerhw]

Found the source of the major rattle coming from passenger seat.
It's little bit stupid, it's a coin stuck underneath the plastic(no idea what is it, like a ventilation port).
Very little shakes would make it rattle.

Removed the coin and it's peaceful and quiet...
while still, will be figruing out those rubbers to be replaced.

[johnung]

I don’t know about that M dept tuning comment that you heard. Remember that M is also a BMW Marketing term that they use excessively, so don’t always assume it means any sort of superior engineering.

Remember also that the 340i is an F-Series and M340i is a G-Series. So there are chassis suspension differences making it much more difficult to compare & contrast various mods.

Below is a video from FaRKle! of a G-Series damper installation. It’s not meant to be a series comparison but it does show some differences especially with the bump stops that would be important to know if suspension modding.

https://youtu.be/weBiIzKM0YM?si=Ck1gGZ8jfZLp4J7r

[casualDIYer]

Originally Posted by bimmerhw

Thanks! I still prefer not lowering it, so not much choice. I did find some very good feedbacks about KONI active so thinking of it and it's much cheaper than KV LE.

Also mostly drive on street and occassionally on track, so sounds like KONI active is enough.

Keep in mind there are a couple of advantages coilovers have over the spring+damper setup. The simplest one is that damper and spring can be matched to work at an expected level of performance. Please note this does not mean you can't change the spring nor that every combo fits every car. One F30 owner pointed out he got the wrong spring for his heavier F30 on a set of KW coilovers and need to get a proper set later on.

The second advantage is that with the spring+damper, the height of the spring will determine fender height from the wheel. A spring manufacturer can shorten the spring by subtracting material. The problem with that method though is the spring, now shorter, will have less leverage. Alternatively, to get around that problem the manufacturer can widen the spring while shortening it, keeping the length the same but shortening the height. The challenge here is, widening the spring may interfere with the wheel. In the coilover, the manufacturer can use the same length of spring but by altering the bottom spring perch has the ability to raise and lower the fender height above the wheel and without widening the spring, avoiding wheel-spring contact.

Of course one can still make garbage coilovers despite their advantages so buyer beware.

[johnung]

Originally Posted by casualDIYer

Keep in mind there are a couple of advantages coilovers have over the spring+damper setup. The simplest one is that damper and spring can be matched to work at an expected level of performance. Please note this does not mean you can't change the spring nor that every combo fits every car. One F30 owner pointed out he got the wrong spring for his heavier F30 on a set of KW coilovers and need to get a proper set later on.

The second advantage is that with the spring+damper, the height of the spring will determine fender height from the wheel. A spring manufacturer can shorten the spring by subtracting material. The problem with that method though is the spring, now shorter, will have less leverage. Alternatively, to get around that problem the manufacturer can widen the spring while shortening it, keeping the length the same but shortening the height. The challenge here is, widening the spring may interfere with the wheel. In the coilover, the manufacturer can use the same length of spring but by altering the bottom spring perch has the ability to raise and lower the fender height above the wheel and without widening the spring, rising wheel-spring contact.

Of course one can still make garbage coilovers despite their advantages so buyer beware.

The criteria that manufacturers use to match dampers & springs varies widely. Coilovers designs were born out of tracking, so coilovers as a rule tend to ride more stiff and harsh. People don’t install coilovers thinking that the result will be a smoother, more comfortable ride.

An exception is KW who really seem to try to match their coilover dampers & springs to optimize both handling and comfort. I first heard about KW coilovers from a friend who mods a number exotic cars, like McLaren, Ferrari, Audi R8, etc. A customer brought him KW coilovers to install. He said that it was the first exotic that he had driven that didn’t have a super harsh/stiff ride. It caused him to ditch Bilstein coilovers and start installing KW coilovers on all of his own project cars.

Manufacturers of separate lowering springs do NOT change the diameter of the stock spring coil itself. That is a standard BMW value to mate properly with the stock spring perches and suspension components. There is absolutely zero chance for the width of a lowering spring to interfere with a wheel because it is exactly the same as stock. There is no coil outside diameter change.

If you are thinking of the actual wire diameter, any changes to those are tiny. For example a front spring on a RWD car might use a wire (to form its spring) that is 13.0mm in diameter. To handle the extra front end weight of AWD components, an XDrive car may use a front spring made from wire with a 13.2mm diameter. But both springs are wound to the exact same outside diameter to fit perfectly on the stock spring perches and to have the same clearances from other car components.

Most people do not realize that separate stock size springs and coilover springs are not the same diameter so they are not interchangeable. If someone buys coilovers and decides to change springs they must choose from aftermarket springs made to that same coilover diameter.

Damper manufacturers like Koni and Bilstein test, certify and sell combo kits using spring kits from spring manufacturers like Eibach. So by purchasing separate dampers and springs from well known manufacturers, there is little chance of a spring/damper combination being tremendously unmatched.

Having said that, aftermarket spring manufacturers have different philosophies. H&R and Dinan tend to use dramatically higher spring rates than stock, often 50% more. So they ride more stiff/harsh. They also tend to use the same spring part number across an entire chassis line despite there being many models with different weight engines, equipment and axle weights.

Eibach springs stand out in the aftermarket because Eibach designs spring kits for different models depending on their stock ride heights, and their specific front & rear axle weights. Eibach spring rates are typically a little more than stock with the goal of adding more control without harshness.

Also Eibach typically designs their spring kits to lower the front more than the rear. This eliminates some of the BMW reverse rake which on my car means that the front tire/fender gap is about 3/4” more than the rear tire/fender gap.

Note: H&R and Dinan springs often lower the same F&R or sometimes even lower the rear more, creating more reverse rake and even a look like the front is up in the air and the rear is sitting on its tires.

I did a thorough evaluation of separate springs, dampers and coilovers for my car. The spring rates followed exactly as I had said. They got much stiffer/harsher in order:
Stock->Eibach->KW->Dinan/H&R->Bilstein

My conclusions in each category were:

Springs: Eibach spring kits had proper spring rates and drops for better handling with comfort.

H&R and Dinan used very high spring rates and poorly designed drops. Many reported stiff/harsh rides.

Dampers: Koni Special Active and Koni Sport Yellow (user adjustable for comfort) provided both handling and comfort. SA’s oriented towards daily driving. Sport Yellows also oriented towards the track, they directly compete with B8’s.

Bilstein B6/B8 actually increased the front tire/fender gap and were setup stiff/harsh from the factory with no adjustment capability.

Coilovers: KW has the best combination of high quality materials, handling, and comfort with smartly chosen spring rates and dampers. KW V2 Street Comfort has best height adjustment range for XDrive along with user adjustments for comfort. KW V1/V2/V3 have great handling and comfort with increasing levels of user selectivity.

Most coilovers use cheap materials that rust quickly, have spring rates that are too high, have dampers that poorly match springs and have really poor drop ranges, especially for XDrive.

IMO the prices of separate springs & dampers, and coilovers really do not overlap. For example if separate Koni dampers and Eibach springs total $1,000, most of the coilovers anywhere near that price are crap for one or more reasons. The prices of the KW V1 and KW V2 Street Comfort are the starting point of coilovers that tick off all of the necessary requirements for me.

(If an XDrive coilover kit does not have minimum drops of at least Front 1.5” and Rear 0.8”, or less- then the car could risk breaking front drive shafts or looking like it’s sitting on its rear tires.)

Bilstein has a philosophy of setting up many of its products to be stiff/harsh from the factory- more for tracking where those things are less of a concern. The Bilstein B16 coilovers especially are known for extremely high spring rates that make for a very harsh ride.

Hope this helps someone!

[casualDIYer]

Another plus for the KW seems to be better supply management. This is not exclusive to KW by no means but how many stories do you have to hear about Bilstein not fulfilling an order week after week to wonder if your order won't be delayed? Of course forums do tend to be a place where people will share negative experiences but it seems, at least for BMW owners, 'Bilstein' and 'delay' just seem to happen more than 'rarely'. If you can wait, what would be the harm in waiting for the product you really want? But if you have a leaking strut and the ride is awful, waiting week after week is really going to test your patience. I would say whatever your choice is, if possible, have a backup. Product availability, outrageous shipping charges, never ending excuses over delays, can also be factors in choosing parts.