Dampers (shocks) lasting nearly “forever”?

[chris719]

I looked at both links. Link #2 is, I think irrelevant to the discussed matter and link #1 (tirereview) is just a bulletin post that repeats “every 50k miles” thesis, but does not explain how a unit that doesn’t leak and does not produce an extra bounce going over a bump can still be a spent one . So, can you explain it in your own words? Because I understand people that say: “no leaking and no extra bounce, therefore my dampers are fine”, but I don’t understand (hence my asking) people’s logic that say: “dampers that don’t leak and don’t produce extra bounce can still be spent”. If I understood correctly, you are in the 2nd camp, so I’m asking if you could explain the mechanics involved that substantiate your claim. If you don’t want to answer - it’s all good, but please don’t get offended like the other guy

The general rationale is described in the first link and the second link explains in detail the components of the dampers. It should be an easy conceptual exercise to get a rough idea how wear to bushings, seals, valves, guides, oil, etc. could produce a decrease in damping force or some kind of unwanted motion.

BTW - I said this already - they absolutely DO produce extra "bounce". You just might not always notice it. Put a high res high sample rate accelerometer in the car and log data, then replace the shocks and do it again. You are going to have less motion.

 

[brianl703]

I replaced the shocks in my 1998 Nissan Frontier when it had about 90K on it and when it was about 23 years old. (It was my dad's and he did not drive it very much).

The shocks felt like they were worn out. Most noticeable going over speed bumps. Additionally, the dust cover over the rod on both front shocks had rusted through in several places.

I replaced the shocks with KYB shocks. I noticed that the new KYB shocks were MUCH harder to compress than the old OE shocks; so much so that it was a little difficult to get them installed.

 

[AlphaOmega]

You cut/paste opinions supporting your position that shocks last virtually forever but offer no data.

That was a question, not a claim. See question marks at the end?

If I google, most results are “blogging” style pages by various repair facilities. But also saw enough people on German car forums posting “200k mi” on original dampers, and these kind of people are not averse to replacing parts, so I figured there must be something to it and hence my asking a collective hive mind here. The conclusion I draw is that 200k mi for dampers is not a since fiction, and as long as there is no extra bounce or weird motions, mileage alone is NOT an indicator of damper’s life! But I still keep an open mind. I’ve been mulling if I should replace struts and rear dampers on my car, now that I’m nearing 100k mi, but will postpone in light of people’s experiences posted in this thread, since my car handles straight, tight, and without extra bounce when hitting certain road irregularities at freeway speeds.

 

[chris719]

That was a question, not a claim. See question marks at the end?

If I google, most results are “blogging” style pages by various repair facilities. But also saw enough people on German car forums posting “200k mi” on original dampers, and these kind of people are not averse to replacing parts, so I figured there must be something to it and hence my asking a collective hive mind here. The conclusion I draw is that 200k mi for dampers is not a since fiction, and as long as there is no extra bounce or weird motions, mileage alone is NOT an indicator of damper’s life! But I still keep an open mind. I’ve been mulling if I should replace struts and rear dampers on my car, now that I’m nearing 100k mi, but will postpone in light of people’s experiences posted in this thread, since my car handles straight, tight, and without extra bounce when hitting certain road irregularities at freeway speeds.

In the end it is subjective. If the car handles fine for you, then don't touch them. They are wear items and will eventually need replacement, so I like to do it a bit early and gain some of that new car feeling back.

I bet if you email Sachs, Bilstein, etc. who OEM dampers for the Germans and ask if their OE parts are good for 200k miles they will probably tell you hell no.

 

[Winterpeg]

I’ve seen this multiple times now, across various forums: dampers lasting for well over a 100k miles and even 200k+, or so people claim.

In my own case, at nearly a 100k I detect no issue with them, with my adult-still-teenager driving style. I know there is no issue because there is no extra bounce when hitting certain familiar expansion joints at freeway speeds.

Here are just a few examples of people’s posts on various German car forums (but not limited to German cars) with people claiming 140k mi or even 220k mi on original dampers

View attachment 149664View attachment 149665View attachment 149666View attachment 149667View attachment 149668View attachment 149669View attachment 149670
And so on.

How often do people replace still functional dampers and then “think” they feel an improvement, whereas if a proper scientific measurement was done, there’d be no significant difference?

The recommend “every 50k mi” is a corporate BS, no?

My 87 Camry went to the scrapyard in 2009 with the original struts all around.It died of rust,300k

 

[AlphaOmega]

Put a high res high sample rate accelerometer in the car and log data, then replace the shocks and do it again. You are going to have less motion.

Makes sense. But the only mechanic through which degradation can take place that was explained and made sense to me, was damper’s fluid viscosity. Just thinking out loud: if a valve was letting through more oil because of becoming worn from use, wouldn’t the car bottom out more often on harsher impacts, thus making it obvious the damper is spent?

And how much do they degrade and over how many miles? If it’s 10% degradation over a 100k mi then it’s a non issue, no? Kind of like replacing a phone because its battery’s capacity is down to 90%? This is separate from regular (loosely: housewife) people not noticing their dampers are gone because it happened gradually and they got use to it. A majority of car enthusiasts should be able to tell when suspension is not just “slightly used” but is performing incorrectly, no?

In my own case, there is one particular expansion joint in the middle of a tight freeway bend that mandates dropping speed from 70 mph to 45 mph. I still enter it 70 and when my wheels drop from one freeway plate onto the next one in a rather stern manner, the car still does not bottom out and makes only one upswing before settling. Same when it was new. I would not claim that my dampers are the same spec as when new, (ditto for my engine), but I’m guessing the difference is rather insignificant - but I don’t know, of course

 

[UG_Passat]

That was a question, not a claim. See question marks at the end?

If I google, most results are “blogging” style pages by various repair facilities. But also saw enough people on German car forums posting “200k mi” on original dampers, and these kind of people are not averse to replacing parts, so I figured there must be something to it and hence my asking a collective hive mind here. The conclusion I draw is that 200k mi for dampers is not a since fiction, and as long as there is no extra bounce or weird motions, mileage alone is NOT an indicator of damper’s life! But I still keep an open mind. I’ve been mulling if I should replace struts and rear dampers on my car, now that I’m nearing 100k mi, but will postpone in light of people’s experiences posted in this thread, since my car handles straight, tight, and without extra bounce when hitting certain road irregularities at freeway speeds.

View attachment 149834

But, when I got Eibach Pro.Kit springs on my Passat, I put Bilstein Sports (B8), which aside from the difference between a twin tube (Sachs OE) vs Monotube (Bilstein Sport-B8), there is a significant difference between the Sachs and Bilstein in terms of valving for both rebound and compression strokes.

Rumor has it, and confirmed by Bilstein reps, many mercedes-benz customers will buy Bilstein B6 monotube and then send it back to Bilstein to revalve it to mimic the properties of the Bilstein B4 (twin tube), since they deemed the B6 ride was too harsh and they prefer the comfort of the B4


On my highlander, I feel the Hitachi dampers are a tad underdamped, while great for ride (it does get a little bouncy), I'd prefer a better balance between ride and handling... so I'm hoping Bilstein comes out with a B4 replacement, as I have not been disappointed with the feel of the Bilstein B4 on previous cars. I can't raid the lexus parts bin for the new RX F-sport suspension as the front struts are magnetically adjustable.

 

[Jimmy_Russells]

What is the mechanism behind it, if the shock isn’t leaking and does not produce an extra bounce over a bump - that’s what I’m asking. Do you know?

Then it is not badly worn? I don’t know what is difficult to understand. Shocks progressively wear. But they tend to get to a point when they get older where the performance starts to fall off a cliff. I don’t really want to get to that point in the first place.

I get this stuff at work all the time (diesel injection pump rebuilds). People bring something in saying it runs fine and just leaks or whatever. So we rebuild it and of course it’s all worn out, they think we’re trying to rip them off or something, but when they get it back they’re blown away at how much better it runs. Yeah, no kidding. Because it was worn the crap out. The degradation is so slow and over a long period of time and people don’t realize it.

 

[AlphaOmega]

Then it is not badly worn? I don’t know what is difficult to understand. Shocks progressively wear. But they tend to get to a point when they get older where the performance starts to fall off a cliff. I don’t really want to get to that point in the first place.

I get this stuff at work all the time (diesel injection pump rebuilds). People bring something in saying it runs fine and just leaks or whatever. So we rebuild it and of course it’s all worn out, they think we’re trying to rip them off or something, but when they get it back they’re blown away at how much better it runs. Yeah, no kidding. Because it was worn the crap out. The degradation is so slow and over a long period of time and people don’t realize it.

This is a rebuilder’s type of answer. I’m hoping more for an engineer type of answer to satisfy my curiosity

A damper is a piston pushing/displacing oil inside a tube. If the seals are intact (no oil leaking) and there is no extra rebound when hitting a bump, and the damper has 200k miles on it - what makes it different from the same new one (if there is a difference), aside from, possibly, changed oil viscosity, do you know?

 

[brages]

If the seal around the piston or the bore it is traveling in is worn enough, some of the oil could get around the piston without going through the valving and that would reduce the damping somewhat. Or wear to the shaft seal could allow contaminants into the oil.

IME, the old shocks/struts that I replaced did not have the same level of gas charge as the new ones - they did not spring as forcefully into the full extended position. So that may allow greater aeration (?) and would give a little less spring support.

 

[UG_Passat]

This is a rebuilder’s type of answer. I’m hoping more for an engineer type of answer to satisfy my curiosity

A damper is a piston pushing/displacing oil inside a tube. If the seals are intact (no oil leaking) and there is no extra rebound when hitting a bump, and the damper has 200k miles on it - what makes it different from the same new one (if there is a difference), aside from, possibly, changed oil viscosity, do you know?

Everything wears, including seals.

 

[BMWTurboDzl]

That was a question, not a claim. See question marks at the end?

If I google, most results are “blogging” style pages by various repair facilities. But also saw enough people on German car forums posting “200k mi” on original dampers, and these kind of people are not averse to replacing parts, so I figured there must be something to it and hence my asking a collective hive mind here. The conclusion I draw is that 200k mi for dampers is not a since fiction, and as long as there is no extra bounce or weird motions, mileage alone is NOT an indicator of damper’s life! But I still keep an open mind. I’ve been mulling if I should replace struts and rear dampers on my car, now that I’m nearing 100k mi, but will postpone in light of people’s experiences posted in this thread, since my car handles straight, tight, and without extra bounce when hitting certain road irregularities at freeway speeds.

View attachment 149834

"Significant" is subjective so it's not relevant to the discussion. Wear is always present but with shocks it's so slow that it becomes the new normal so owners are unaware of it. Since the amount of degradation is experienced on a subjective basis there there's no replacement interval. No automaker has a replacement interval so the strawman of this entire discussion is that they have one.

The only way to measure a used shock is to pull it and compare the rate of rebound to a new shock. Worn shocks have little to no rebound.

 

[repairman54]

I'm waiting for shock oil analysis next....

 

[brages]

....
The only way to measure a used shock is to pull it and compare the rate of rebound to a new shock. Worn shocks have little to no rebound.

When you say "the rate of rebound", what are you describing?

 

[BMWTurboDzl]

When you say "the rate of rebound", what are you describing?

The degree and speed at which the piston rod returns to its normal position once it has been compressed. Worn shocks will exhibit little or no rebound.

 

[Jimmy_Russells]

This is a rebuilder’s type of answer. I’m hoping more for an engineer type of answer to satisfy my curiosity

A damper is a piston pushing/displacing oil inside a tube. If the seals are intact (no oil leaking) and there is no extra rebound when hitting a bump, and the damper has 200k miles on it - what makes it different from the same new one (if there is a difference), aside from, possibly, changed oil viscosity, do you know?

Every time the shaft moves, there is wear. Aside from the seals themselves, the bore the piston rides in, and the piston itself also wears. Eventually you start getting fluid leakage past the piston (not externally), it is exactly the same thing as blow-by in an engine. I mean it's the same reason hood/hatch struts wear out.

 

[chris719]

I replaced the shocks in my 1998 Nissan Frontier when it had about 90K on it and when it was about 23 years old. (It was my dad's and he did not drive it very much).

The shocks felt like they were worn out. Most noticeable going over speed bumps. Additionally, the dust cover over the rod on both front shocks had rusted through in several places.

I replaced the shocks with KYB shocks. I noticed that the new KYB shocks were MUCH harder to compress than the old OE shocks; so much so that it was a little difficult to get them installed.

It’s hard to directly compare OE to aftermarket too, the behavior can be very different even when both are new.

 

[dogememe]

On my 2010 Escape at 120K or so one of my front struts blew out suddenly although handling seemed fine. The funny part is it failed right after starting the car while parked. I put it in drive and released the parking brake and there was a big bang and after that the car was super wobbly. Anyway, after a new set of MasterPro strut assemblies on the front and KYB shocks on the rear it felt a little firmer the first few weeks but after that really the same as before. Either I got used to it or there was really no noticeable difference in daily driving between 120K "dampers" or new ones.

 

[AlphaOmega]

the bore the piston rides in, and the piston itself also wears. Eventually you start getting fluid leakage past the piston (not externally), it is exactly the same thing as blow-by in an engine

that's it! that hit the G spot in my brain. I see now how damping is gradually reduced.

Once there is "blow by" inside the damper, is it a runaway condition - as in the damper quickly moving from, say 80% OEM spec to 20%, within a few thousand miles (or even quicker) or is it a slow, progressive decrease (in most usage cases)?

Would you, personally, go by your own feel for how suspension is performing or by mileage?

 

[Jimmy_Russells]

that's it! that hit the G spot in my brain. I see now how damping is gradually reduced.

Once there is "blow by" inside the damper, is it a runaway condition - as in the damper quickly moving from, say 80% OEM spec to 20%, within a few thousand miles (or even quicker) or is it a slow, progressive decrease (in most usage cases)?

Would you, personally, go by your own feel for how suspension is performing or by mileage?

I'm not a technician for shocks. What I can tell you is that in my industry, typically when things start to go bad and/or wear, they get worse at an exponential rate.

Your last question is a personal one, everyone is going to be different. I will be the first to tell you that feel to me is extremely important. When something is off, or not right, it bothers me. I like the engineering behind things, and I like them to be be used and perform the way they were designed. So, I will replace my shocks when I either get a fault (mag-ride), when they start to feel off, or I discover an external leak or similar. I'm also someone who is just going to do all four at once, I'm not going to do one and then another in six months, another in three months, etc. Being MR they are expensive to replace and I may go an aftermarket route like Bilstein or KW but at the same time I don't really want to give up the adjustability. So it's a trade off either way.