I posted this in my model specific forum with limited help.
So ... I am posting it in suspension specific hoping for more help!

Okay, so my buddy was arguing with me on the subject and we have 2 opposing views, he happens to be a mechanic. He plans on buying lowering spings -2" and running them with BRAND NEW OEM shocks.

He claims that the OEM shocks will handle the lowering springs, and will not blow out. As long as they are brand new. He claims that the stock shocks and stock springs develop a pre-set "surface of travel" inside the shock. He says once you switch to lowering springs and keep the old OEM shocks, that regular travel area changes which causes the shock to start leaking and losing pressure.

He claims that when you take a NEW shock and stick it on a lowering spring, after a certain period of time the shocks get used to the springs that are on them (and create that "surface of travel" inside the shock). And everything will be fine. He claims that installing new OEM shocks and new performance shocks will give the same results, depending on driving conditions. He says the seals are what blow.

My friend claims that if you install lowering springs on performance shocks, and the car is being driven on bumpy roads alot, the performance shocks will actually blow FASTER than OEM shocks. I ROFL on this one.

Okay, so heres my perdicament and following are MY views on the subject:

When you have a stock, original, OEM suspension assembly. The spring takes the most grunt of the impact, which compresses and rebounds. The shock is in place to control the impact of the spring, to basically slow it down.

When you lower the car on lowering springs, the ride gets rougher and the spring rate needs to be higher. When the spring rate is higher, it can handle more unsprung weight which makes it go more crazy when it hits a bump (opposed to an OEM spring).

Since the spring is compressing and rebounding faster than stock, a performance shock needs to be used to control the spring. A performance shock will be able to more effectively handle the spring based on the higher damping forces of the shock. The higher damping force will ensure that the shock has less of a chance of bottoming out and less of a chance of blowing altogether.

Now correct me if I am wrong, but the damping force is the ability of the piston to actively displace a mass of gas/fluid from one part of the shock to another. Isn't this achieved through a hole in the piston, the bigger the hole the more effectively the gas can be displaced?

The shocks blow becuase the pressure on one side of the piston builds up (because the damping force is no great enough, the gas has nowhere to go) and the piston seal blows?

Since my friend claims that the performance shock will blow faster than OEM under bumpy/harsh conditions, doesn't that defeat the whole purpose of a performance shock, to NOT blow?! More specifically, he claims that putting regular new struts on lowering springs will not effect the life of the struts. And that the performance shock will blow because it is not designed to handle the bumps, which is kind of contradictory to the whole prupose of the performance shock (to outhandle OEM and NOT blow).

He claims that a shock is a sealed unit, and the pressure inside never changes.

Now, who sounds more correct? He ended up basically calling me an idiot because I was in doubt of his theory. He is about to be ASE certified as he claims and that this knowledge comes from his experience and learning from his superiors.

When you guys respond, also let me know how much experience you've had and if you are a mechanic or not. He specifically said that your responses would probably not be valid (if different than his theory) because you are backyard mechanics.

Also, if you could provide me with any clear-cut links about the reason for shocks blowing, that would be MARVELOUS. I can't seem to find any.

Thanks for your input and I can't wait to study the subject some more!

 

You're reading way to far into it man.
The only thing that makes your friend a moron is that he will be dealing with higher spring rates, which need to be damped accordingly. Otherwise, on a bumpy road, it will feel 10 times worse. Under damped shocks are dangerous.
Aside from that, he makes some good points. Lowering a car will create a different wear area within the shock. That will wear out seals faster.
He is also right that aftermarket shocks will probably blow faster on a very bumper road. It all depends on the manufacturer, durability of the specific shock, vavling, etc. But the fast motion, extreme travel situations will make a tightly valved shock work hard. Work it hard enough, often enough, the tighter valving will give out. Again, quality of parts is a major factor.

I should also mention that ASE certification not as great as it sounds. Read up on it. As long as you have two years experience in the field (including working the counter at Checker), you can take any of the tests. Read up a little, and you can pass any of them, since they give you pre tests on the site, and it's really general questions. Two of my friends are ASE certified, and they said it was just something to look good on a resume. I never bothered with it, since I don't wrench for a living, rather race as a hobby for the last 10 years.

 

Interesting post, I think youre both probably right. What he said makes sense, but at some point the damping of the stock shocks will just be outmatched depending on the spring rate. Hmmm, makes me think a bit.