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Simian Rex
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Discussion Starter #1 (Edited)
This question comes up a lot, so I just made one big effin' post in some random thread to purge all of the data stuck in my head. Thinking about it harder, I decided to split it and stick it. Enjoy!

Let's take two springs, and two dampers. One spring takes 200 lbs of force to compress one inch, the other takes 150 lbs of force to compress one inch. We'll call them Heavy (200) and Light (150). One damper we'll simply call Firm and the other Soft. Let's say you also have an imaginary but alarmingly sophisticated unicycle, and these dampers and these springs fit and work on this unicycle. Let's assume that your unicycle, with rider, weighs three hundred pounds (somebody needs to adjust their diet, don't they?). I'm no physicist (Hell, I cain't even speel right mose times), and I don't proclaim to know how all of these weights relate to forces on a mathematical level, but we're not talking about heavy math, we're just making examples.

The spring's job, remember, is to hold the wheel to the ground, even when you strike irregularities like bumps and potholes. When you roll into a bump at a high rate of speed, your body tends to want to conserve momentum, and stay at the same orientation but still moving forward. The bump wants to drive the wheel UP into the body, thus changing it's vector. Momentum doesn't like this vector change, so we add a spring in the middle to give making a semi-firm instead of an absolutely solid link. When you roll into a pothole, the opposite occurs, but instead of simply giving (compressing), the spring forces the wheel down into the depression. On the other side of each of these irregularities, the bump becomes a dip, and the hole becomes a bump. The body has probably changed it's vector anyway, so the spring is asked to do the opposite of what it did just a split second before. These rapid changes in motion and duty are called, for simplicity, oscillation. The damper's job is to keep the spring under control when oscillation occurs. It does this by resisting acceleration of the spring, be it compression or rebound (jounce).

Let's pair Light and Soft on your unicycle first. With your weight and those spring rates, you should be able to get some pretty wild motion out of the reciprocating assembly (that's the combination of the spring and the damper, because those are the parts that, ahem, reciprocate). The ride is comfortable for an overweight rider on an overly complicated machine, but you want more! On vehicles with more than one reciprocating assembly (motorcycles usually have two, cars usually have four), the way to get better performance is to raise the spring rate, so we'll do the same on your UniMondoCycle, and assume that it will have the same affect. Yes, I said assume; what do I look like, a unicycle developer?

So we'll take the UniMondoCycle back to the Fantasy Garage, and mount Ibox Heavies. One hour, a six-pack of Shiner Bock, and twelve busted knuckles between the three of you later, your buddies have helped you with your first upgrade. Lets hope you can still operate a unicycle, 'cause we have testing to do (not on public roads, naturally, and always wear appropriate safety gear, especially when operating unicycles under the influence of alcohol)!

The good news is that you can now go faster with more responsive turn in and your confidence at attacking corners is improved. The bad news is that when you encounter irregularities, the oscillation is out of control. When a rock in your way wouldn't even phase the Light/Soft combo, the slightest pebble now makes the UniMondoCycle feel like somebody just smacked you in the nuts with a hammer. When you roll over a real irregularity like a speed bump or a corner bubble, it takes twice the oscillation to control. The old combo would only oscillate three or four times before returning to a neutral state, and the Heavy/Soft setup oscillates about six to eight times. Dampers have a non-linear relationship to spring rates, so even upping the rate by 30% presents an observed 100% increase in oscillation in our super-crude and totally mathematically unfounded example.

Another problem is decreased damper life. This is because you have hydraulic-filled, gas-charged dampers, and the materials inside are prone to thermal fatigue. The recent increase in oscillation rate has cut your damper life in half in and of itself (just having to work twice as much), but this also induces heat problems, because it's doing twice the work in the same amount of time. This excited behaviour leads to decay of the hydraulic fluid and gas, as well as minor deterioration in the piston's valves. God help you, though, if you didn't get a Heavy spring long enough for your weight and activity, because bottoming the piston against the damper body does waaay more damage than your valving problem and your decay problem combined.

The fix? A Firmline damper from Kewaibi. You should have done this in the first place, but some monkey at a speed shop assured you that Ibox are intended for use with your standard damper, so you took his word for it. Now you have to go back to the Fantasy Garage, back to the grocery store (for more Shiner Bock), and hope that your buddies are still on speaking terms after one of them contracted Tetnis from the last misadventure.

This was the best upgrade you made. You're faster than ever before, and the ride control has returned to nearly- or better-than-stock. The sight of a pebble still sends you into cold shivers, but if you wanted a cushy ride, you should have bought at least a trike, right? Bubbles and bumps are no sweat, though, as oscillation is back to near stock or even lower counts, so you can go faster with the same level of interruption as stock. Since oscillation is normal again, and assuming at least the craftsmanship of your original damper, the high-po Firm damper will now last just as long as your stock Soft damper, despite the increased spring rate.

YAY! UniMondoCycle Factory Team Xtreme is now on it's way to victory lane!!! :D

Conversely, if you already had Heavy/Firm from the factory, but the only spring "upgrade" available to you is actually a Light spring, you can still reap benefits in damper longevity, because bumps now take one or two oscillations to control instead of three or four. Wanna know a secret? Even though Spec-V dampers are waaay firmer than SE dampers, they're still not firm enough for Spec-V springs, so they are effectively also Heavy/Soft setups, which can be improved upon. There is such a thing as too much damping, but back in the real world of Spec-Vs and Progress springs, the stock configuration is underdamped to START with. Since your only two variables are the spring and the damper, your only option is to lighten the spring, which has anecdotally improved the ride (though not necessarily performance) of several Spec-V owners.
 

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OMG Dren..... that is one of the most awesome post i have ever read.... not only was it informative .... funny ... but it had the infamous Unimondocycle......and had people drinking Shiner bock my favorite beer in the world ....... You should frame that post ..heh
 

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Now I have two boys!
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Random House called Dren...

Dren, you kook. The funny thing is that some people will read that post and go, "What the hell is oscillation? ... and non-linear???"

I commend you for your informative, humorous post. I understood every bit of it, then again we've been 'round and 'round the mulberry bush on this topic so many times, I'd deserve to be shot if I hadn't.

I tried to simply explain it before, but like you already know, it's a real ***** to explain something thoroughly around here. Maybe the combo of your technical manual, coupled with my more-basic-than-chewing-food description will get across the point, finally.

Hehe, I love being someone who actually get's it now!!!
 

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I don't like to put a damper on things but it seems to be necessary because the explanation is causing continuous oscillations in my mind. What specific parts are necessary and who makes them?
 

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Oh my God! flash backs to physics 151, stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it!
he he he :D

Good post Dren!
 

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Looks like your ABS was on.

daavikes said:
stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it! stop it!
 

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Simian Rex
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Discussion Starter #9
Automaton said:
What specific parts are necessary and who makes them?
Would you mind restating the question, please?
 

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Simian Rex
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3,213 Posts
Discussion Starter #11
Oh. You should read more. I recommend Progress springs and stock Nissan Spec-V dampers, but they're not the only options. Just spend some time using the search function; I recommend "spring rate," "lowering spring" and words along those lines to search for. Just read posts for a few days; you'll figure it out.
 

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#SERs beat = to many.
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whoa

that was crazy man, i understand things i never knew before, i don't feel as dumb. But either way i don't care about mods becuase i'm a warranty puss...
 

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Yeah... WE NEED FIRMER SHORTER DAMPERS..for our firm springs...

lets call them NISMO... LOL
 

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you think nismo could buy a clue and produce something needed instead of oil caps and front bumper add-ons and rear spoilers
 

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oh, egads, you dont say. if they are going to bring nismo over, then they need to bring it full force. One big wave, with parts to make all nissans stand out and outperform all others, but lets face it, thats all we are going to get for now
 

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HEY!!!

In the post that I started about dampers being the problem with wheel hop, you stated that the dampers are the last thing you would replace. But here you state the the springs are too firm for the dampers. What's up with that?
 

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Simian Rex
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Discussion Starter #19
Context, my dear friend, context. This is in the context of improved handling. That thread is in the context of reducing or eliminating wheel hop. Totally different reasons to do the same job, thus demanding different sequences. Note that I also adocate using lower spring rates to make Spec-Vs more drivable...it's all about context.
 

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Dren, say you lower a spec with progress springs, how long would you give it for the dampers to give? and do you think you can explain the benefits of coilovers please?!
 
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