I'm thinking about dialing up some more height, I'm scraping everywhere. Any tricks to this?

 

You will have to have it adjusted and re-aligned. I have mine at approx -10 and it's barely tolerable for me, fun for now but likely not gonna be a long term deal.

 

I'm more than pleased with the ride compliance. I'm set way too low for road clearance. When I drive down my own street the front lip scrapes on an otherwise barely noticeable road wallow. My neighbours are giving me that look.

 

Mine is set at -15mm, that's even too low at times.

 

I am not clear on your question; let me take a guess. The very first thing you need to do is to measure the current height of your car per the method I posted.

Next, we know that stock is 132/153. If you want down 12mm front and rear for example, then your target is 120/141. If your car is currently at 110/141 for example, and scraping, then you just need to adjust that front spring perch (anyone corrects me as needed) up 10. Hope this helps.

 

Thanks for your explanation but why would the gas volume not decrease in a lowered car (steady state/static) but does so in a dynamic situation? This doesn't make sense to me since in either case it is a form of compression. The other question I had is I thought the whole idea of monotube shocks is that they DON'T have a reservoir tube but instead uses the floating piston/gas chamber instead.

Something has to explain why the OP experiences a harsher ride when lowered. Assuming the damper installation was done correctly, then it sure seems that the harsher ride is a direct consequence of lowering.

 

Thanks Cannga.
I'm going to measure on the weekend. I was told the springs settle as you drive but I would guess they will be settled down after a month or so.
Bob

 

Excellent question. The answer will have to be long, if you are interested. But.. please note I am an amateur and could not guarantee 100% accuracy!

1. First, the monotube shock may or may not have an EXTERNAL reservoir, but internally, they do have another chamber for the fluid to move to.

2. Second, your question takes us back to fundamental physics, or chemistry, or whatever it is that I learned many years ago. That is, fluid is not nearly as compressible as gas (try to squeeze a syringe of liquid with closed ends). So in action and for all coilovers, the gas chamber is compressed, but the fluid chamber doesn't get compressed as much as the fluid inside it moves to another chamber.

3. So in above diagram: a is the seal, b is the first fluid chamber, c is the digressive (look this up for fun) piston that contains the bump and rebound valves through which the fluid flows bidirectionally, d is the second fluid chamber, e is the floating piston, and f is the "gas chamber" .

4. So when you lower the height, valve c moves to the right, some fluid will move from d to b, valve e and chamber f stay the same, the coilover then achieves quilibrium/steady state at this new position. The gas volume therefore does not decrease and this is a fundamental operating principle of nitrogen charged monotube shock.

(However, when the coilover is compressed in a dynamic situation, e and f now do get compressed and move to the right, in addition to the fluid movement. How much of course depends on the pressure and the specific coilover design. In other words, BOTH fluid movement and gas compression contribute to the overall dampening force of the damper.

 

Hi Can, Many thanks for that excellent tutorial. One "last" question. When you lower the car, the piston will move to the right. That will decrease the overall volume of compressed oil + gas chamber (negligible contribution). So why wouldn't that decrease in volume increase the "harshness" of the ride since the "dampening" has less stroke volume to dissipate the energy? I hope this makes sense. TIA.

 

You are very welcome and no problem Dave; fire away with as many questions as you like. I see why you are asking: You are missing one key to the puzzle. You are thinking chamber d gets compressed and therefore pressure rises. In fact pressure doesn't rise because as chamber d gets squeezed the fluid escapes!

Look at that piston c: it has **holes** (actually deflective discs and/or needle valves) in it that allows fluid to go from chamber d to chamber b (compression), and vice versa (rebound).
The dampening force is purely a function of how big those holes are. Bigger hole = less resistance, because the fluid escapes from b to d faster. Smaller hole, more resistance, because fluid cannot escape from b to d as fast as the piston c move to the right.

BTW, voila, you have just now learned the secret of PASM: the variation of the hole size in piston c is how we have the 2 modes of PASM. Big hole: Soft/normal. Small hole: Hard/sport.

All this talk will point back to another issue: Why lowering spring works but technically is just a bad bad idea. Why all the people in the know use springs at first but immediately switch to coilover once it becomes available.

 

Thanks again Can. Maybe you should write a book called "Suspensions for Dummys"

The PASM/valve design is indeed very clever. While I understand how it works, I'm still trying to rationalize why the static position of a lowered car would not result is a harsher (albeit even slightly harsher) ride. When you hit a "bump" the piston in a lowered car has less volume of "cushion material" underneath it to absorb the shock. So if I understand you correctly, you're saying static pistion position doesn't matter because the oil will be displaced into the reservoir chamber. It's been a long while since I took physics and I know we didn't covered shock absorbers (it certainly would have been more interesting) but this is what I am picturing. When you hit a bump, the force is transmitted to the shock and, in particular, to the "cushion material" underneath the piston. The impact of the force will be applied to the entire volume underneath the pistion which includes the bottom of the piston, tube wall, and floor. So to me, a larger volume of "cushion material" would be able to better absorb the force since the force is disspated over a greater area/volume even if there is fluid transfer. I agree that the size of the holes is the overriding determinant here but it sure seems like the "cushion volume" would play a role as well. Anyhow, thanks again for the great feedback.

 

Hi Dave. I think I know exactly where/why you are having problem.

1. Ok, first, forget about the fluid being compressible when the coilover moves. Liquid state is not compressible until extremely high pressure -- the coilover doesn't work on this principle.

2. The coilover works PURELY on that fluid moving through "holes" on the piston. So:

 

Got it! Thanks Can. That certainly takes care of that topic.