Shocking madness? {Looking for shock absorber data} - Page 2 - PeachParts Mercedes-Benz Forum

Mölyapina · #16 02-01-2014, 11:24 AM

Quote:

Originally Posted by Stretch

I wouldn't go that far, a direct push onto the bathroom scales would be fine. They are "calibrated" (I use the term loosely!) for that orientation.

Have a look at chapter 32-120 for how the FSM says to check 'em I think that'll give you some idea of what's involved.

If you get to the stage of taking some shock absorbers to bits (before me) make sure you don't injure yourself - they are pressurized and could potentially put a hole in you.

If you can measure the volume of oil in a shock that would be great information to have - but as measuring cups are often a bit out of whack an additional measurement of weight could prove to be useful.

What I could do is get the weight of the absorber and then subtract that from the force required to actuate some piston movement.

But since I've never been one to make things easy... could you pile an ever-increasing amount of weight onto the shock and then measure the weight that it takes to get the shock moving? That would seem more "stable" a way to do it.

Thanks for the FSM ref -- I'll check that.

I don't think my rears are leaking, so I could take one of those to bits both to see how much oil is in there and what seals would need to be acquired. I'll try not to kill myself, either.

Stretch · #17 02-01-2014, 11:38 AM

Please don't destroy anything that might be useful - I have a set of W201 shocks that will be going under the knife soon(ish).

Mölyapina · #18 02-01-2014, 11:43 AM

Don't worry -- my rears are bad, just not leaking.

Mölyapina · #19 04-08-2016, 07:42 PM

Here is an interesting thread on the subject from a Honda forum where the guy is actually revalving his shocks, but it looks very applicable to just refreshing them as well.

DIY Bilstein revalve project - Honda-Tech

His first paragraph references what might be a possible source of information:

Quote:

Originally Posted by beanbag on honda-tech.com

Intro:
Since I was starting to get fed up with the "black magic" in paying others to revalve shocks (*cough* Koni *cough*) I decided to go with a set of Bilsteins and practice revalving them myself. The good thing about Bilsteins is that they encourage (sort of) users to do this by selling all the parts, and the guys at the North Carolina division are pretty helpful as well. Another nice thing is that pretty much all their shocks use the same internals, so you can go with the lowly commodity circle track or dirt racing shocks.

Stretch · #20 04-09-2016, 05:24 AM

I had to chuck my W201 shocks 'cos of the little "d" - when I get some new ones I'll have a go at seeing if I can get the things in pieces with out spreading shrapnel...

babymog · #21 04-09-2016, 11:17 AM

Find someone in racing, or who rebuilds shocks.

There is a thing called a shock dyno, which is able to measure the jounce and rebound energy absorption, which is what a shock absorber does. The pressure necessary to compress or extend will change drastically with speed of compression (or extension) and it can't be duplicated easily by hand (our validation lab had equipment for this, I used it often).

The best that you can do is extend and compress them to see if there is significant damping, if not then they're shot. If the gas pressure is missing to keep them extended (designed to prevent boiling / cavitation of the oil), then they're shot. Whether they can be rebuilt I do not know, depends on the design of the shock as some are swedged together and not able to be disassembled without destroying them.

Mölyapina · #22 04-09-2016, 12:10 PM

To what extent are OEM parts made by different manufacturers built to the same spec? I have used good shocks from Boge and Sachs for my 240D, but not from Bilstein. If I got specs from Bilstein, could I use the specs to rebuild my Sachs and Boge shocks, or at least to estimate the correct specs?

Mölyapina · #23 04-09-2016, 12:13 PM

Quote:

Originally Posted by babymog

Find someone in racing, or who rebuilds shocks.

There is a thing called a shock dyno, which is able to measure the jounce and rebound energy absorption, which is what a shock absorber does. The pressure necessary to compress or extend will change drastically with speed of compression (or extension) and it can't be duplicated easily by hand (our validation lab had equipment for this, I used it often).

The best that you can do is extend and compress them to see if there is significant damping, if not then they're shot. If the gas pressure is missing to keep them extended (designed to prevent boiling / cavitation of the oil), then they're shot. Whether they can be rebuilt I do not know, depends on the design of the shock as some are swedged together and not able to be disassembled without destroying them.

In the link I provided, the guy actually builds a shock dyno... unfortunately, it costs him like $200, which makes it less worth it to do the job on these cars. I wasn't sure if a shock dyno was necessary for just putting in the stock amounts of nitrogen, oil, and new seals, though.

From what Zulfiqar posted, I'm guessing that these shocks would be rebuildable...

babymog · #24 04-09-2016, 03:04 PM

Agreed, if you have the seals and oil, can charge the proper amount, the only thing remaining is the nitrogen pressure (which could be the most difficult).

I have a pair of new adjustable Konis for a 201, never installed because one has no nitrogen pressure, I never looked into whether they can be charged and re-sealed (NOS, have had them for probably 20years). They would be covered by the lifetime warranty if I could find the receipt (can't), but as I haven't had a 201 in many years, ... not a priority.

Junkman · #25 04-09-2016, 05:48 PM

I have a pair of Bilstein Comforts that were working. The PO would only do 1/2 of the system at a time and I replaced all 4 with HDs. My intent is to put them on Craigslist but can go measure force until then.

97 SL320 · #26 04-09-2016, 07:53 PM

Quote:

Whether they can be rebuilt I do not know, depends on the design of the shock as some are swedged together and not able to be disassembled without destroying them.

Many shocks have the top roll welded. I've used a hacksaw to cut the tube just below the weld in order to get the cap off. I've then dumped oil and refilled with motorcycle fork oil since it comes in various viscosities.

Before cutting apart I used a scale to measure force compression force so gas pressure could be replicated.

A nut was welded to the shock body then tapped for 1/16 pipe, tire valves can be gotten with pipe on one end making filling easy.

The top can be easily MIG welded back on completing the process.

Another super secret trick. Monroe Sensatrac shocks have a line in the cylinder that bypasses fluid at ride height, this line does not exist at the limits of travel and isn't centered in the travel. I was able to flip the cylinder on a lowered car and instantly get a stiffer shock.

Internal parts for a stock shock are going to be impossible to get no mater the brand. Take apart racing shocks are made to be repaired and parts are floating around.