Spring selection

[fabr]

There you go.It just SEEMS like it should be the other way.

[Admin]

[fabr]

Greatr article.Glad you could find it.I'm saving a copy now.

[BDKW1]

There are a couple assumptions in that article that depending on the car could lead someone vary far from the mark.

[fabr]

Fill us in.

[BDKW1]

1, Not everyone wants 40% sag ride height.
 
2, Calculating the spring rate based on the corner weigth without subtracting the unsprung weight will be really off on a light car. Cars should also be ballasted for normal occupant load.
 
3, Angle of shock from vertical? Should be angle of shock in relationship to the arm pivots.
 
4, 150/300 spring rate? Potential pogo stick unless it's got bypasses and the secondary stop collars are set correctly.
 
Coming from GD, it's pretty close.......   Most Glamis cars are set up like crap and have horrible geometry so I guess it's better than nothing. It doesn't take much to make a car look good going through the dunes.

[Admin]

were is the shock angle measure, full droop, full bump?

[fabr]

[Admin]

I would suspect it is at full bump or at ride height, My 1st guess is ride height...

[Admin]

this calculator seems to factor in angle of a arms to ground, and the shock to the ground...

http://www.swayaway.com/calculators/swayawayCalc.php#step5

[fabr]

Nowhere have I seen it addressed. I assume ride height myself but it would be nice if the mofo's that make this stuff would put out some info that was really useful instead of being full of "guessing" gaps.

[Admin]

Lets throw this into the mix, with a 5 link, 3 link etc the scrub moves in and out and front/rear, now the shock would have 2 angles likely forward and sideways, how do we correct that with the calculator?

[Admin]

Seems to me it will not matter were it is measured, if you use both equations, shock angle to ground, and a arm pivots to ground... The a arm is the lever, so to use the lower shock mount angle to inner arm pivot angle would not be accurate correct?

[Engineer]

When it comes down to it, spring selection is probably like horse shoe's and hand grenades.  Close counts.  A universal calculator isn't going to take into account every scenario, or slight difference.  When you look at the jumps in spring selection, 150 lb, 200 lb, 250 lb, they are jumping 25% with every change, so you won't get an exact spring even if you had an exact number.

Also on the shock angle.  The relationship of wheel travel to shock travel somewhat takes the angle into account.  different progression rates can be in play, but generally if the wheel travels 20" and the shock travels 10", you have your ratio.  If your shock is laid down so far that it goes to a radical angle at top or bottom, there is no correct spring the will fix the problem.  I noticed that the F-O-A calculator didn't ask the shock travel, so they are not going this route.  But others may.

I would generally agree if measuring the shock angle, do it at ride height, and measure the angle between the frame mount and spindle relative to the shock.

[fabr]

We can all generally agree and be dead wrong.It would seem that we should know what was meant with the formulas.Too bad the "experts" seem to miss that we need a bit more info.  Also when using dual springs as we have had seen you DO get a far more defined rate availabiity. You are not then limited to 50 # increments.  I do agree tho that hand grenades and horseshoes apply here. I don't think the grenades are anything more than m-80's.LOL!!! I will guarantee you this much engineer ,IF they are leaning 10-20-30 degrees  or more from vertical it WILL make a huge difference in the spring requirement.