Bilstein B8 Failure- What to do?

[adam1985]

So have had a bit of a knocking sound coming from front left corner.
Got chance to take a look at the weekend, couldn't find anything loose.
Was about to put the wheel back on and though i would have look under the cover of the shock, which didn't look good, video below.
[youtube]r_gpn_uoX80[/youtube]

Now I'm assuming that the shock has failed and that gunk is a mixture of dirt and oil from the shock.
Has anyone else had this with a Bilstein shock? I had the B12 kit fitted since May 2015 and only done 25K since then, this doesn't seem long enough for it to have failed.

The question is whats the best thing to do now?
Replace the single shock, drivers side looks fine.
Replace both front shocks in case the other one is on its way out too?
The best price i can find for individual shocks is around £200 each, i only paid £650 for the full B12 kit :headbang:

 

[eddiemunster]

The question is whats the best thing to do now?
Replace the single shock, drivers side looks fine.
Replace both front shocks in case the other one is on its way out too?

Always by axle, never singularly, and never when the shocks have been on more than 6 months.

I used to test tyres, we could mash a set of shocks in 10k miles doing nothing more than generic road-testing. The only difference to us testing, compared to your average driver, is that we deliberately wouldn't slow down for speed bumps/cushions, we'd drive the car as per your average "lazy" driver. So, 25k doesn't sound overly low mileage for a car like this, but more likely at 5 years old the inner seals will have perished and that'll have caused the failure.

I had B4s on my Z4, I took them off (despite being in good condition) and replaced them with Sachs twin-tubes (which I also have on my 123d and 320d) and in my opinion they're a more robust and progressive shock.

 

[adam1985]

Always by axle, never singularly, and never when the shocks have been on more than 6 months.

I used to test tyres, we could mash a set of shocks in 10k miles doing nothing more than generic road-testing. The only difference to us testing, compared to your average driver, is that we deliberately wouldn't slow down for speed bumps/cushions, we'd drive the car as per your average "lazy" driver. So, 25k doesn't sound overly low mileage for a car like this, but more likely at 5 years old the inner seals will have perished and that'll have caused the failure.

I had B4s on my Z4, I took them off (despite being in good condition) and replaced them with Sachs twin-tubes (which I also have on my 123d and 320d) and in my opinion they're a more robust and progressive shock.

Yea I was pretty much thinking both shocks, you got a link to the Sachs, are these jsut the OEM style?
I suppose that's my other option is to fit something other than the bilsteins that are a reasonable price.

 

[eddiemunster]

Yea I was pretty much thinking both shocks, you got a link to the Sachs, are these jsut the OEM style?
I suppose that's my other option is to fit something other than the bilsteins that are a reasonable price.

https://www.ebay.co.uk/itm/Sachs-2x-Shock-Absorbers-Dampers-Front-Pair-Gas-Pressure-312-467-312-466/332683650987?epid=7020342174&hash=item4d757da7ab:g:EmsAAOSwdfZbH68j

They're OEM replacement, but to me, they feel as though there's more compression than standard and said rate is geared towards initial compression rather than even linear; that, in my opinion, suits normal road driving as it'll be more robust/compliant over uneven surfaces.

The big difference that I noticed over the B4s was mid-corner, the Sachs aren't as affected by uneven surfaces/changes in tarmac/negative camber, and if you "kiss" the occasional speedbump without noticing it, they don't bottom out and groan like the B4s. I suspect overall shock life will be slightly shorter on the Sachs, as they say you don't get something for nothing, but much like tyres, I'd rather fit the best option for driveability than longevity. Other people make choose the opposite, that's fair enough.

 

[ph001]

I am assuming the Sachs shockers are gas damped rather than oil? What are the ramifications of that in terms of performance / lifetime?

Ah... just found this on the web...

"Oil shock absorbers – these are very common. A relatively simple, cheap to produce shock absorber filled with oil.

Gas shock absorbers – The biggest misconception about gas shock absorbers is they are filled exclusively with gas. Not true. Every shock absorber has hydraulic oil. Nitrogen gas is used to pressurize the oil which prevents the oil from foaming, a term called cavitation. This provides a reliable stable shock absorber, big safety improvement over the oil damper which suffers from a noticeable drop in damping force under load. So with this in mind changing your standard oil shock absorbers for Bilstein B4 gas will improve your vehicle stability, road holding and safety. A worthwhile investment."



and this....

"Many shock absorbers contain pressurized nitrogen gas in them as well as the hydraulic oil. If a shock has to react very rapidly to an up and down motion the hydraulic oil can start to foam. This foam causes the shock to lose some of its control. The purpose of the gas in the shock is to keep the oil under pressure so it is less likely to foam. This is the same reason a can of soda that has been shaken is still a liquid until you pop the top. The foam doesn’t start until the pressure is released."

 

[eddiemunster]

I am assuming the Sachs shockers are gas damped rather than oil? What are the ramifications of that in terms of performance / lifetime?

Plenty of top-end shocks are exclusively oil, for people like Bilstein/KYB/Sachs etc. the use of gas/oil is to create a better quality of shock at a price-point that can attract more customers. I had ProFlex on my Integrale, £1k a corner and that was 15 years ago, but the net result was that the shocks were amazing on the track, on the road, even on gravel (to a lesser extent); the more you spent often the more bases you could cover. Building those now would probably more like £300-£400 a corner, and that's why you'll often see 1970s cars out-handle far more modern cars, suspension has moved on so far in the last decade (never mind the last 40-50 years) that you can transform a car simply by updating the suspension but without having to spend ludicrous amounts of money.

Springs are equally as important too; the same ride height with 2 sets of springs does not mean the same performance. Rate, initial sag, compression rate, decompression rate, material quality etc., etc. all play their part in how the overall spring performs, and those reasons are why I rarely stray from companies like Eibach; they make so many OEM springs, for seriously top-end cars, that their design and manufacturing process' allow you to have complete confidence in what you're buying. Knowing the "constant" is so important in testing everything, having a measurable datum is the be-all and end-all.