F31 340i Touring - coilover options?

[tomprestriidge]

I’ve collected a 2017 340i Touring and it’s got the M Performance splitter, side skirts, and rear diffuser. The car is currently on its stock suspension, so it sits quite high, which doesn’t compliment the body styling bits.

I’ve also just come from a 2016 M240i, so the 340i feels softer and less keen to turn in. I don’t want to lose more than, say, 25% of the ride comfort, but would appreciate improved turn in.

I’ve done a little research into coilover options (I’ve never modified a car’s suspension before):

• - Bilstein B14 kit - Reputable brand at a decent price; I’ve seen another forum post that approves this kit () and the ride height looks great.
• - HSD Dualtech kit - I’m aware of this kit as I follow DriftWorks on YouTube, so trust their experience, but am worried this kit will be too firm, and I’ve not seen any photos of F31s equipped with it.

I’m looking for a lower ride height without compromising too much ride comfort and quality. Budget is £1000.

Does anyone have any thoughts or experience?

[danb79]

tomprestriidge said:

I ve collected a 2017 340i Touring and it s got the M Performance splitter, side skirts, and rear diffuser. The car is currently on its stock suspension, so it sits quite high, which doesn t compliment the body styling bits.

I ve also just come from a 2016 M240i, so the 340i feels softer and less keen to turn in. I don t want to lose more than, say, 25% of the ride comfort, but would appreciate improved turn in.

I ve done a little research into coilover options (I ve never modified a car s suspension before):

• - Bilstein B14 kit - Reputable brand at a decent price; I ve seen another forum post that approves this kit () and the ride height looks great.
• - HSD Dualtech kit - I m aware of this kit as I follow DriftWorks on YouTube, so trust their experience, but am worried this kit will be too firm, and I ve not seen any photos of F31s equipped with it.

I m looking for a lower ride height without compromising too much ride comfort and quality. Budget is £1000.

Does anyone have any thoughts or experience?

I ran the Bilstein B14s on my previous E81 130i LE and they were superb; fitted as part of a full suspension overhaul (literally every part) with all new OEM BMW top mounts etc

I also run Bilstein B4S shocks with Eibach pro-kit springs on our F31 and for an every day car; that suspension is superb. Smooth, quiet; but handles and drives much better than OEM M Sport suspension did; plus it sits a lot better too

For £1k, personally; I'd go either the B14s if you can get them at that price with all new top mounts all round etc, or maybe consider the likes of the Bilstein B4S or B8 shocks with the Eibach pro kit springs and again, new top mounts all round etc

I personally wouldn't touch anything from HSD - they're cheap budget coilovers and your 340i deserves better

[tomprestriidge]

Thank you for the advice!

I was under the impression that B4 weren’t to be used with lowering springs, or have I misunderstood?

I’ve read that B4 with lowering springs reduce the life of the shocks; B6 and B8 are for lowering springs.

[Pizzaeatingking]

I really liked the B14s on my saloon. Rode well, less crashy than stock but certainly firmer, I ran them for 5 years without issue.

[danb79]

tomprestriidge said:

Thank you for the advice!

I was under the impression that B4 weren t to be used with lowering springs, or have I misunderstood?

I ve read that B4 with lowering springs reduce the life of the shocks; B6 and B8 are for lowering springs.

B4S are absolutely fine with the likes of Eibach pro-kit springs as they don't lower aggressively; 10-15mm max more than M Sport

B8s would be needed a) if you want a firmer ride and b) if you were to go with the likes of H&R springs or the Eibach Sportline springs which can lower 35mm or more - that's when B4s would be no good

This is our F31 as it stands:

[danb79]

Pizzaeatingking said:

I really liked the B14s on my saloon. Rode well, less crashy than stock but certainly firmer, I ran them for 5 years without issue.

They are superb; very tempted with them for my E39 - but want to see how I get on with the Sachs/Eibach combo first

[Cheddarbang]

I would personally stick to the tried and test B12 kit and save some cash.

Bilstein coilovers are the terrible for seizing up, which is useless on a daily driver.

The improvements to handling come from more than just struts/springs. Camber, tyre choice, body stiffening etc etc all come into play.

Doing just the struts/springs only addresses BMW's poor setup choices and damper quality of the stock M sport suspension.

There is a whole lot more on the table with the F3x platform to be tapped into, but with only £1000 budget, you're not ready to go down that rabbit hole.

[mmm-five]

Cheddarbang said:

I would personally stick to the tried and test B12 kit and save some cash.

Bilstein coilovers are the terrible for seizing up, which is useless on a daily driver.

The improvements to handling come from more than just struts/springs. Camber, tyre choice, body stiffening etc etc all come into play.

Doing just the struts/springs only addresses BMW's poor setup choices and damper quality of the stock M sport suspension.

There is a whole lot more on the table with the F3x platform to be tapped into, but with only £1000 budget, you're not ready to go down that rabbit hole.

I've had my B16s on my Z4MC for over 10 years and 60,000 miles...not seized up yet...but they're checked & cleaned every year when I get my annual Inspection I.

Maybe the cheaper kits are worse, or maybe Bilstein quality has degraded over the last decade...'cos Brexit

[danb79]

Cheddarbang said:

I would personally stick to the tried and test B12 kit and save some cash.

Bilstein coilovers are the terrible for seizing up, which is useless on a daily driver.

The improvements to handling come from more than just struts/springs. Camber, tyre choice, body stiffening etc etc all come into play.

Doing just the struts/springs only addresses BMW's poor setup choices and damper quality of the stock M sport suspension.

There is a whole lot more on the table with the F3x platform to be tapped into, but with only £1000 budget, you're not ready to go down that rabbit hole.

I know plenty of folk running B14s and B16s with zero issues. Look after them, clean them and treat them with the likes of BH DYNAX UC and they won't corrode nor seize...

Same with any coilovers really...

But don't do the above and they'll be fubar in a year or so...

And for me, the B12 kit on the F3x platform is just too stiff. Even with Eibach Pro kit springs.

I test drove an F30 330D with the B12 kit and it was superb on the country lanes when pushing on.. But driving back on normal roads doing normal speeds, and the car was bouncy and didn't take rough roads well at all... That was on 19s with Michelin non RFTs.

Everyone's different, but for every day driving and even pushing on, the B4S shocks with Eibach Pro kit springs work much better. Still firm, but have more compliance compared to the B12 kit

[Cheddarbang]

That is kind of my point. Who can be ar$ed to unwind the threads every year and relubricate the spring perches? That's why the B12 is better suited to daily drivers, and the inch or less of lowering keeps the roll centre sensible, and therefore bump steer to acceptable levels.

I don't believe any anecdotal "A mate of a mate's is fine" examples because I've been through many coilover brands and done all the anti seizing diligence, and they still effing seize up after the 2nd winter without fail, even the KWs with Inox bodies and composite perches.

If you use a car for 50-100 miles every day all year around, there is no way in hell coilovers don't seize up, unless you're out there regularly greasing the sodding things, or use some exotic greases like Metaflux.

19s and non-run flats is probably where you're going wrong then. I run 18" run flats and the B12 isn't bouncy in the slightest. Bouncy is a twin tube trait. Monotubes are the exact opposite. If the car is bouncing then either the dampers are shot, or its way over sprung.

B14s are over twice the spring rate of the B12, so I find it very hard to believe the B12 is crashy and the B14 isn't.

[Jamescrs]

I've seen on youtube recently people fitting a type of cover on coilovers to protect the threads and stop them seizing, I have no evidence they work but it seems like a good idea in theory