lost, entirely lost with suspension desperate

[TimZ]

Okay, now I'm confused. It looks like you are showing the spacer on top of the strut cartridge, so that it's bottom sits on the bottom of the strut tube.

 

Why would you want to do that? It doesn't make sense. This approach negates that amount of suspension travel for no reason. The spacer should always go under the cartridge. Am I missing something here?

 

Also, on John's point about the strut not travelling as far as the wheel, this is a known characteristic of suspension geometry. The strut travel is some percentage of the wheel travel, which is determined by where the strut (or shock) attaches to the a-arm. For instance, if the strut attachment point is in the middle of the a-arm laterally, then the strut travel will be 50% of the wheel travel. Same theory goes for sway bar effectiveness, btw.

 

The thing with the Z strut, though (at least on my '78), is that the strut tube is directly behind the spindle, so there should be very little difference between the strut travel and the wheel travel. At worst, I would guess that the strut travel is 90% of wheel travel in this case.

[Guest Anonymous]

okay my brain hurts....... this WAY to difficult to discuss these things without visual aide, especially when you start talking about geometery and giving percentages, stupid car....

[jeromio]

True, the suspension travel measured at the wheel will be different than that measured at the strut (in a complex trigonometric ratio).

 

BUT, it doesn't matter. The wheel is what counts. No one is talking here in terms of lowering the suspension. I agree that if you lower the spring perch by 2 inches, you're not necessarily going to lower the car by 2 inches (although it's really close).

 

We're talking about lowering the CAR. So, when you do that you are ONLY talking about the relationship of the wheel to the car. And so 2 inches of lowering the car is 2 inches of reduced effective (bump) suspension travel at the wheel. We don't need to consider what the actual strut travel is because it isn't relavent.

 

And yes, you don't usually put the spacer on the top of the cart, as I stated in my post ("My little scenario, un-obviously (oops) is assuming the unusual, top spacer."). My spacers, for instance, are underneath the cart.

 

Even as I type this I see that this is all become just too silly. Originally I was only trying to illustrate the complexity of the whole strut shortening, cartridge substituting thing so that Havok and others would have a better appreciation of the non-linearity of the relationship: ie, 2 inches shorter struts does not gain you back 2 inches of travel from a 2 inch lowered car. Then I made an oddball reference in order to further make the point.

 

And now, here we are. My picture looks pretty though, don't it?

 

Camber plates, if you can afford them, will be much easier and straight-forward.

[Guest Anonymous]

jeromio (hahaha i spelled it right) yeah im just gunna sleep on it, call ground control see what they say then make my decision... thanks every one for your input, whew... long day.

[TimZ]

quote:

---

Originally posted by TimZ:

The thing with the Z strut, though (at least on my '78), is that the strut tube is directly behind the spindle, so there should be very little difference between the strut travel and the wheel travel. At worst, I would guess that the strut travel is 90% of wheel travel in this case.

---

 

Actually, now that I'm thinking a little more about it, the Z strut (on my '78) is actually part of the spindle assembly, and moves exactly the same amount as the wheel - it physically cannot move independently of the spindle.

 

...And now that I've thought about it few minutes longer, I'm thinking that there is some difference between strut travel and purely vertical wheel travel, but this is due to the fact that the strut is not purely vertical. Instead, the strut is angled inward slightly.

 

Interestingly, this would mean that the vertical wheel travel differs from the strut travel by the cosine of the angle that the strut has from vertical (the strut is on the hypotenuse of that triangle). So, if this is correct, in this particular case, the strut travel would acually be GREATER than the vertical wheel travel.

 

Now, some of this effect will be negated by the fact that the bottom of the strut doesn't move purely up and down, but rather in the arc prescribed by the a-arm. However, I think that the strut angle will still be the dominant factor here, simply because it's longer than the a-arm.

 

...Has anybody's head exploded yet?

[johnc]

Let's keep it simple (us racers and engineers tend to get focused on the minutia because its fun)...

 

All the ITS and BSP racers I know shorten their front struts about 1.5" and run the MR2 or the GTI strut insert up front (with a spacer underneath) and the 240Z front strut insert in the rear. I forgot off the top of my head how much the rear struts are shortened - I think its 1".

 

FYI... Don't even bother shortening the struts unless you're running a racing coil-over spring set up. If you're just cutting the stock springs or installing progressive Eibach/ST springs in the stock diameter, limit the lowering to 2" max, and install good urethane bump stops.

 

That's the best and simplest advice I can give.