Susupension Thread

[7thgear]

Originally Posted by old greg

This is a function of spring rates, not damper rates.

yes correct,

but the dampers are there to control that oscillation

so while you can solve the initial problem of 4 corner balance by simply installing the correct spring, in the real world most people just buy off-the-shelf units which are tuned for some median chassis/wheel weight and not your specific case.

in effect, you can use a damper's adjustability to compensate for that incorrect spring rate to some degree in addition to overall tuning.

[trackmagic]

Old Greg, Oregon State. You?

[old greg]

Originally Posted by trackmagic

Old Greg, Oregon State. You?

USF. If you're with GFR, you may remember me as the shitfaced guy in the "I Like Turbos" shirt at the California party last year.

[trackmagic]

Originally Posted by old greg

USF. If you're with GFR, you may remember me as the shitfaced guy in the "I Like Turbos" shirt at the California party last year.

I was with GFR, but I graduated in 2005. That would have been before my time. Sounds like a good story though

[Dimman]

Bump for more questions...

Regarding the wheel rate/frequency calculations, I've been using the assumption that the front MacStrut has a 1:1 ratio.

But looking back at the MotoIQ suspension sticky and article, the amount that the strut is offset and a comment Mr Kojima makes about it.

Pic:



And he says:

Another interesting point is that the front strut is mounted unusually inboard so the front suspension motion ratio is pretty high. This means that a pretty stiff front spring will be needed.

So I came up with this...



If this is correct, this would make the motion ratio/leverage appear to be closer to the rear multi-link...

Thoughts? Corrections?

[fatoni]

Originally Posted by Dimman

Bump for more questions...

Regarding the wheel rate/frequency calculations, I've been using the assumption that the front MacStrut has a 1:1 ratio.

But looking back at the MotoIQ suspension sticky and article, the amount that the strut is offset and a comment Mr Kojima makes about it.

Pic:



And he says:




So I came up with this...



If this is correct, this would make the motion ratio/leverage appear to be closer to the rear multi-link...

Thoughts? Corrections?

im not certain but i dont think that changes the motion ratio at all but that depends on if you are adding length to ac and ab or just ac

[Dimman]

Originally Posted by fatoni

im not certain but i dont think that changes the motion ratio at all but that depends on if you are adding length to ac and ab or just ac

It was what he said about the motion ratio that got me thinking, everywhere else seems to treat MacStruts as just 1:1

[fatoni]

Originally Posted by Dimman

It was what he said about the motion ratio that got me thinking, everywhere else seems to treat MacStruts as just 1:1

i dont have the deepest knowledge of suspensions but im pretty sure you still would even with an inboard strut like you posted.

[old greg]

Originally Posted by Dimman

It was what he said about the motion ratio that got me thinking, everywhere else seems to treat MacStruts as just 1:1

Distance inboard doesn't affect motion ratio in strut suspensions (well, it does affect motion ratio progression a little). Only the angle of the line of action of the spring/damper matters.

[Dimman]

Originally Posted by old greg

Distance inboard doesn't affect motion ratio in strut suspensions (well, it does affect motion ratio progression a little). Only the angle of the line of action of the spring/damper matters.

The mounting angle affects the fitted rate and changes a little as they cycle, correct? So inboard/outboard can have an effect on how the angle changes, only (which isn't huge)?

So what the hell is Kojima talking about?

[old greg]

Originally Posted by Dimman

The mounting angle affects the fitted rate and changes a little as they cycle, correct? So inboard/outboard can have an effect on how the angle changes, only (which isn't huge)?

Yep. Moving the upper mounts inboard will create a progressive motion ratio, but we're talking an order or two of magnitude below the static MR.

Originally Posted by Dimman

So what the hell is Kojima talking about?

Maybe he's just fallen prey to a misconception.

[Dimman]

Originally Posted by old greg

Yep. Moving the upper mounts inboard will create a progressive motion ratio, but we're talking an order or two of magnitude below the static MR.





Maybe he's just fallen prey to a misconception.

Thanks.


So if I came up with Front 1.5Hz and Rear 1.35Hz (RCE says 185 lbs/in f&r) would I be in the right ball park?

[Ryephile]

Originally Posted by Dimman

So what the hell is Kojima talking about?

He's confused. Mac Struts' motion ratio is almost always about 1:1. The only thing that changes it is their angle vs. vertical. This is why in practice most Mac Struts motion ratio is about 0.98:1 or there about.

Originally Posted by Dimman

So if I came up with Front 1.5Hz and Rear 1.35Hz (RCE says 185 lbs/in f&r) would I be in the right ball park?

Sounds like you're in the ball park. Do you have the exact motion ratio of the rear suspension [of the Impreza]? It seems Toyobaru may be slightly overdamping the rear end to account for the otherwise under-sprung rear suspension.

[old greg]

Originally Posted by Dimman

So if I came up with Front 1.5Hz and Rear 1.35Hz (RCE says 185 lbs/in f&r) would I be in the right ball park?

Seems reasonable.