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  • Petrolheads/car nerds – monotube shocks
  • Premier Icon molgrips
    Full Member

    Has anyone got experience of going from twin tube shocks to monotube? I think the OEM ones on the Merc are twin because the rod is thin, whereas in the pictures of the Bilstein B6 that say they are monotube it’s a thick tube.

    Monotube is meant to give better ride quality, which is good, but this is wrapped up in all sorts of ‘performance’ bollocks which suggests they are firmer, which I don’t want. The car has sport suspension already and I don’t want to make it any firmer than it already is.

    Premier Icon snotrag
    Full Member

    The car has sport suspension already and I don’t want to make it any firmer than it already is

    You want Bilstein B4s, not B6’s then.

    I would strongly, strongly reccomend Koni Special Active though if they are available. They are like magic (Platform/Digressive type damping which you will recognise from the bike world!).

    Premier Icon molgrips
    Full Member

    But I don’t know if B4s are softer than what I have now?

    Also, if B4s are twin tube will they actually be less plush?

    I would strongly, strongly reccomend Koni Special Active though if they are available. They are like magic (Platform/Digressive type damping which you will recognise from the bike world!).

    I will take a look. Although Bilstein have ‘dampmatic’ which is the opposite of what I’m used to from bikes. Less low speed compression and more high speed. This means that it is nice and supple over normal road undulations, which makes it pretty comfortable on motorways and good roads, but it firms up on bumps which keeps it controlled. This is noticeable when driving to the point where I’d figured this out before I’d read about it.

    Basically I want to keep or improve the combination of suppleness/firmness when required, I don’t want it to be actually a sports car.

    Premier Icon crogthomas
    Free Member

    On Bilsteins the ‘thick’ rod you refer to is usually the damper itself. They are mounted upside down. The thin rod still exists, but is inside the yellow metal casing along with the bump stops.

    Premier Icon molgrips
    Full Member

    Doesn’t look like Koni have my car in their model list.

    Premier Icon patagonian
    Full Member

    According to the Bilstien website B4’s are direct OE replacement parts and B6’s are uprated to give a sporty ride.
    Given your requirements I’d avoid the B6’s.

    Premier Icon Gribs
    Full Member

    Going off replacing the shocks on my Saab Aero if you have sports suspension fitted you need the B6’s as the B4’s are too soft to work properly and are meant for the standard suspension.

    Premier Icon molgrips
    Full Member

    Well I’m not sure if Bilstein are aware that my car already has sports suspension, this is the issue. They seem to offer me B4s then say they are for ‘standard’ suspension but then it says that on the B6s too and B8s are for ‘sports’.

    Premier Icon patagonian
    Full Member

    Again according to the Bilstein website B4 & B6 are the same length and B8’s are shorter for lower springs. I think you need to ring Bilstein directly.

    Premier Icon molgrips
    Full Member

    Beginning to think that.

    I contacted Sachs when I replaced the ones on the Passat and got the ones in their catalogue, they were quite a bit firmer than the OEM ones. Not sure if that was just age or what. Firmer but more supple on small bumps due to being new I guess.

    I suppose the only way to guarantee they’re not going to end up sportier is to go with Merc – aftermarket might be worse… but they might be better!

    Premier Icon MarkyG82
    Full Member

    B4 – OEM replacement for standard suspension
    B6 – sports dampers for stock height
    B8 – same damping and performance as B6 but shorter for low ride height.

    B6 can accommodate lowering springs like eibach prokit. Much more and you should probably go for B8.
    Many car man’s sport suspension is merely a lower ride height with no damper change. B6 would be a good upgrade and are quite comfortable with a little more stiffness but the added support is sublime compared to worn stock shocks.
    Currently on koni special actives and not as impressed as I was with B6 on the old car.

    Something to bear in mind is that B6 damptronic are twin tubes. Same design as B4 but stiffer damping. If you have that type I would suggest going with B4 damptronic as they are much cheaper. Or bin off the electronic bits and go full B6.

    Premier Icon molgrips
    Full Member

    Cheers MarkyG82. I don’t have damptronic but I do have dampmatic. Although supposedly all Bilsteins have it?

    And as for stock height – I’m not sure if the OEM lowered suspension counts as stock or not.

    Problem is that I need the car to be a comfy mile muncher for the family more than a sporty fun thing, but I don’t want to wreck the handling by fitting too squishy dampers.

    Premier Icon bsims
    Free Member

    The B2 are the OEM replacement, The B4 are slightly stiffer OEM replacement. Bilstein Germany told me that for my Sport damper I should replace with the B8 not the B6.

    I don’t know about twintube but compared to the VW sport damper the B8 was better in ride quality but firmer. Not in a bad way, but you could feel what was going on more and the cornering was ridiculous compared to OEM. The only thing that was really apparent was going over short steep bumps like the rubber speed bumps and ripples in worn road surfaces.

    I can’t answer the comparison with your own dampers but having driven with the B8s and then going to standard damping, in our Passat highline. I was going to get b6s for it until some **** wrote it off. Unless you know someone with them fitted you will have to suck it and see.

    edit – The b4 seem to be gas and not all models are stiffer

    Premier Icon MarkyG82
    Full Member

    I hadn’t heard of the B2 until you mentioned it. Looks to be a more budget option. B4 is still listed as OEM replacement. I would avoid the B8 unless you specifically know they would fit the current springs. I doubt factory lowered springs would be so loose on the shocks that they would need shorter shocks.

    Premier Icon molgrips
    Full Member

    Unless you know someone with them fitted you will have to suck it and see.

    Yeah it’s a tough one. Autodoc only lists B4 for mine but maybe that reflects that it’s already on sports dampers? The big choice is between Mercedes own (also made by Bilstein) or B6s I think. Both B6 and B8 are listed in parts catalogues for my reg number.

    Premier Icon bsims
    Free Member

    @Marky G82 – I would agree. I was unsure when looking, so emailed Bilstein in Germany and went with their recommendation. The B2 do look more budget and just mentions oil so ride comfort would be inferior to B4.


    @molgrips
    – you could try contacting Bilstein Germany. For reference the Bilstein B8 were cheaper than VW OEM replacements made by Sachs so that sealed it for me. Bilstein said that for the VW parts i was looking at the damping was the same it was just the B8 were shorter.

    Edit – Based on my experience I would say get the Bilstein after market. My situation said B8 because e of the sports suspension but would recommend checking by phone of email as to the correct model.

    Edit edit – @molgrips – I’ve messaged you the email address I used.

    Premier Icon molgrips
    Full Member

    having driven with the B8s and then going to standard damping, in our Passat highline. I was going to get b6s for it until some **** wrote it off.

    Sorry I’m not sure I can parse this :). You mean that the B8s were so good you wanted B6s for your Passat to make it equally good? And you wanted B6 because it wasn’t lowered?

    Many car man’s sport suspension is merely a lower ride height with no damper change.

    I test drove a Jetta (2008 ish) with sports suspension, and it was ridiculous. The ride was so hard and bouncy it was not even funny. Completely different to the normal car, utterly undesirable, and wasn’t even particularly low. Didn’t feel at all sporty, just shit.

    Premier Icon bsims
    Free Member

    The b8s were better than the oem vw sports suspension dampers. The cornering was ridiculously good compared to the oem with minimal change in ride comfort.

    The Passat had standard and I hated the wallowyness after driving with the b8s so was going to upgrade the dampers to the b6 which have the same damping rate but are longer for non sports/ lowered springs.

    If you didn’t like the sports suspension on that Jetta then get The dampers from Mercedes’ with their oem valving. You won’t like the after market ride.

    The b8s did eliminate that bounciness from the vw sports set up.

    Premier Icon Edukator
    Free Member

    If it ain’t broke don’t fix it and if it does need fixing fix it properly.

    I’ve had three cars with Bilstein suspension, Group N rallycars: Samba and Nova, and an otherwise standard Peugeot 605. What they had in common was that each corner was a complete pack. At the front a complete strut with spring and damper and at the back a matched spring and damper. Just changing the damper it’s highly unlikely that the damper will correspond to the spring rate over the full range of travel.

    In terms of performance the Samba kit was ace (supple, well controlled with wel chosen spring rates), the Nova kit less so (too soft at the back) and the Peugeot was a fabulous ride : handling compromise at a sensible ride height.

    Premier Icon molgrips
    Full Member

    If it ain’t broke don’t fix it and if it does need fixing fix it properly.

    Shocks may fail, but they deteriorate over time. Mine are 9 years old, and in my experience replacing old shocks really increases what MTBers would call small bump sensitivity.

    Just changing the damper it’s highly unlikely that the damper will correspond to the spring rate over the full range of travel.

    This was what happened with the Passat, the aftermarket ones were much firmer. And this is what I want to avoid on this car. Thing is, I don’t know how firm they were when they were new. What I want to know is how the B6s for example correspond to the OEM Merc ones. I’m hoping that since Bilstein have made Merc shocks since forever, they would at least know how their aftermarket kit compares to the stuff they made for Merc.

    Just found a Bilstein vendor that describes B4 as monotube. If so, this could be the best option for comfort, and they are half the price of the Merc original. I don’t mind paying for B6s if they are worth it but I don’t want to pay double for original parts if they are just B4s.

    Premier Icon bsims
    Free Member

    Email the manufacturer as they will know. The vendor in the uk will only know what the uk sales rep told them.

    Premier Icon Edukator
    Free Member

    If the dampers affect how firm a car feels they’re almost certainly wrong or trying to compensate for another flaw in the suspension set up.

    You have front and rear spring rates (which can be progresive) and anti-roll bar stiffness to play with to determine ride height and how soft/hard teh ride is. The dampers are just there to control the movement. If the dampers are making the ride firmer they are providing too much resistance for the spring. Or they are being used to control pitch and roll rather than using appropriate geometrie, springs and anti-roll bars in the first place.

    The big German saloons I’ve drive seem to be set up for running 250kmh on a smooth autobahn and are utterly dreadful on French départementales. Too low, too little travel (because they’re too low), too hard (because they’re too low which means they need high spring rates to stop them bottoming out). A dumb fashion based around a need for high speed stability and to look like a DTM racer.

    Hard suspension means less grip on rough roads.

    Premier Icon molgrips
    Full Member

    Ed I wasn’t designing a racing car, I just fitted what the retailer sent me, which corresponded with what the manufacturer (Sachs) told me.

    A dumb fashion

    Well I won’t argue with that. I really don’t care for hard suspension. I was given a lift in someone’s B-Class once a short distance around an airport, and it was ridiculous. What’s the point in a car like that with AMG sport kit?

    However, my CLS isn’t like that. It’s definitely firmer than you’d expect but it’s still pretty comfortable on most roads especially now that I’ve changed the wheel size. The things that makes me think the shocks need a refresh are: there’s a little bit of diving under braking, and the front does dip a fair bit when you go over a speed bump; and the small bumps are a bit more noticeable than on a newer car. New shocks on the Passat made small bumps and edges much smoother, so I’m guessing it’s to do with the condition of the seals or the gas pressure inside or something.

    Premier Icon bsims
    Free Member

    If the dampers affect how firm a car feels they’re almost certainly wrong or trying to compensate for another flaw in the suspension set up.

    Didn’t French cars of old have soft springs and fast dampers, then very fast dampers on sports models to control the movement.

    molgrips – replace like with like then you will know what you are getting.

    Premier Icon Edukator
    Free Member

    The front dipping under braking or over a speed bump is the spring doing its job. It’s what follows that tells you if the damper is working properly. The car should bounce back up, rise slightly over its normal ride height then settle down without further movment.

    The new shocks on your Passat sound like they have very little or no low-speed compression damping. Good.

    The gas pressure has a very small incidence on the overall spring rate but is mainly there to prevent cavitation which won’t be an issue over a single small bump.

    You’ve still to convince me you are going to get any improvement without changing both the springs and dampers, Molgrips. It’s not as if you’ve got a wallowy pogo stick with knacked dampers.

    Premier Icon molgrips
    Full Member

    Not really trying to convince you of anything Ed, I just had a question about B6 vs B4 vs original Merc.

    It’s not as if you’ve got a pogo stick with knacked dampers.

    No, but like I said dampers do deteriorate over time subtly – this seems to be common knowledge and it’s also backed up by my experience. Every time I drive a hire car or some other new car they feel nice and supple, and I think that is the new shock feeling.

    I am not looking for a performance upgrade, I want the new shock feeling. Now, IF I can also improve the ride further at the same time then I would like to do that.

    replace like with like then you will know what you are getting.

    It’s an option but, for all four:

    Mercedes: £950
    B4: £600
    B6: £900

    So I don’t want to pay Mercedes £950 if I am only getting what Bilstein will sell me for £600. Similarly I don’t mind paying £900 if it’s actually better than the £600 option.

    Premier Icon Edukator
    Free Member

    but like I said dampers do deteriorate over time subtly

    And/or the bushings. The loss of the taut but supple feeling is more likely to be the shock and suspension bushings going soft which means the supension being undamped over the travel corresponding to the slop. Just changing bushes can return as new performance if it’s possible. The dampers themselves perform well for as long as they have gas and oil in them and aren’t actually broken.

    Premier Icon molgrips
    Full Member

    The loss of the taut but supple feeling is more likely to be the shock and suspension bushings going soft which means the supension being undamped over the travel corresponding to the slop.

    It wasn’t on the Passat. It was my first thought, so when I had an MOT advisory I changed all the bushings, it made almost no difference to the ride, but changing the shocks made a huge difference.

    The dampers themselves perform well for as long as they have gas and oil in them and aren’t actually broken.

    I don’t think so.

    Premier Icon Edukator
    Free Member

    I don’t think so.

    Which is a Molgrips way of calling bollocks so I’ll bid you a good evening and fun with your Merc.

    Premier Icon molgrips
    Full Member

    Thanks for dropping in.

    Premier Icon MarkyG82
    Full Member

    I’m with you molgrips. Seals wear, fluid deteriorates, internal bushes wear, gas pressure reduces. All adds up to a reduction in performance.
    If you are specifically after the OEM feel then I would stay away from B6. They are stiffer. If you don’t mind a bit more firmness (better word than “stiffness”) they will do you well.

    Premier Icon molgrips
    Full Member

    I heard back from Bilstein. I gave them my existing part numbers and they said they don’t list a B4 as equivalent for them. So they recommended some B8s which are listed in the catalogue as being for my car but elsewhere for the proper AMG CLS 63.

    So it’s a choice between B8s, which will likely be an upgrade, or OEM which are probably overpriced being OEM parts. Cost will be about the same.

    There are a lot of people saying that B8s are firm but remarkably plush. Hopefully that’s good enough for a family holiday wagon.

    Premier Icon Daffy
    Full Member

    Have you called a few Mercedes Garages for prices? I can usually get a 10-20% discount on OEN parts from a few main dealers groups for my BMW.

    Premier Icon molgrips
    Full Member

    Turns out that the reason I couldn’t make sense of the part numbers currently on the car is that they are actually the wrong shocks. Someone’s had them replaced and gone for the cheap option. They’re both non-sport shocks and the fronts are non-dampmatic which apparently makes it much worse all round.

    So whatever I choose should be a significant upgrade.

    Premier Icon Daffy
    Full Member

    Didn’t you complain the ride was harsh as it stood? So putting sports dampeners on it will help, how?

    Premier Icon b230ftw
    Free Member

    Go to Mercedes forums. Must be a decent one somewhere. Pointless asking on here really.

    The B4s I fitted to my last car were a decent upgrade on the standard softer units but I also lowered it 2” as well so it’s hard to tell. From the forums I found that the B8s were way too much and only ok for fast road applications where comfort wasn’t a consideration.
    But every car is different with different characteristics so comparing one marque with another is pretty pointless even with the same dampers.

    Personally the last thing I would do is get B8s for your car. If your current dampers aren’t leaking then they should be working fine, don’t bother replacing them. Replacing the ARB bushes and any other ropey looking bushes is a lot cheaper and will have a better effect. Also maybe smaller wheels if they are compatible with your brakes – bigger tyres = more comfort. I didn’t bother upgrading the standard wheel size on my new car like so many do and it has a magic carpet ride.

    Premier Icon nickdavies
    Free Member

    Have a word with Steve at CRS performance in cannock, hes mainly VAG world but there isnt much about suspension he doesnt know. Really helpful chap even if hes not going to sell you anything, does the bilstein/koni etc debate on a daily basis.

    Had a merc in there when i had my van fettled so would guess likely he could advise.

    Premier Icon MarkyG82
    Full Member

    So putting sports dampeners on it will help, how?

    So that the dampers will match the spring rate. If the dampers are too fast the suspension will feel harsh due to not controlling the stiff springs.

    Premier Icon molgrips
    Full Member

    Didn’t you complain the ride was harsh as it stood? So putting sports dampeners on it will help, how?

    What I’ve read suggests that B6/8s are both more supple and firmer at the same time. This is what I experienced on my other car by changing shocks. In MTB terms it’s what you would call better small bump compliance – a bit like increasing both the negative and positive air pressures.

    When driving on a smooth road it’s not clear how much of the the movement felt over undulations is compression or actually rebound from being under-damped. What MarkyG82 said, in other words.

    If your current dampers aren’t leaking then they should be working fine

    Not in my experience, see above. Shocks degrade in comfort throughout their life.

    Go to Mercedes forums. Must be a decent one somewhere.

    Yeah I have, you don’t get as good of a response generally though.


    @nickdavies
    ta.

    Premier Icon molgrips
    Full Member

    Not sure if anyone’s still following this but I figured out what’s going on via the VIN decoder and the original brochure that I found online.

    You could specify AMG Sport but then have comfort suspension as a no-cost option. The brochure has this option code as 485. My VIN decoder says I have option 485 fitted. The electronics part catalogue (mbepc.net) lists lots of codes and options for each part number, but the actual code entry says things like -488-489+486 which in that example would mean WITHOUT sports chassis tuning, WITHOUT airmatic but WITH sports suspension.

    In my case, the comfort damper is listed as -488-489+485 which means comfort suspension, and it all makes sense. So I’ve ordered 4x B4s for only £450 from autodoc which is half what MB quoted and fairly reasonable for top quality kit in my book. Saved £60 by using the app!

    Also, I called MB earlier and they told me I did have sport suspension, I reckon they got that wrong.

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