Anyone know what our motion ratio's are F & R? - SRT Forums

**1LAPSRT** · 09-16-2009, 07:08 AM

Anyone ever measure this before?

Thanks!

NemoFoss · 09-16-2009, 07:36 AM

Extremely close to 1:1

NemoFoss · 09-16-2009, 07:38 AM

The lower ball joint is directly inline with the upper pivot.

**1LAPSRT** · 09-16-2009, 08:04 AM

Thanks Nemo!

How about the rear?

NemoFoss · 09-16-2009, 05:43 PM

Same ting

uturner · 09-18-2009, 04:04 PM

Anyone know what is the wheel rate for the F & R?
And unsprung weight?

Thanks

GLH · 09-18-2009, 08:43 PM

are you trying different spring rates or just doing some comparing

JohnyNFS · 09-20-2009, 05:50 PM

Uh Uh I have a question that i keep forgetting!!!

if i know each corner's wheight, can you tell me what would be the perfect spring rate for my car? I usually go by what ksport and some other guys tell me, than i test it, but i was wondering if anyone would know an equation or something?

uturner · 09-21-2009, 01:33 AM

Quote: Originally Posted by GLH

are you trying different spring rates or just doing some comparing

New spring rates, that generally leads to comparing which spring is best.

I believe the wheel rate equation is: Spring rate x Motion ratio = Wheel rate

correct me if I'm wrong. (I think somewhere should fit unsprung mass)

and the corner weight equation is: front right + rear left = xxxx
front left + rear right = xxxx

the answers should be as close as possible.
correct me if I'm wrong on that too.

NemoFoss · 09-22-2009, 08:49 PM

Spring rate is un affected by motion ratio as it is 1:1
Unsprung mass is half the control arm weight, the wheel, tire, hub/brake assembly, the strut and half the spring.

NemoFoss · 09-22-2009, 08:52 PM

Quote: Originally Posted by JohnyNFS

Uh Uh I have a question that i keep forgetting!!!

if i know each corner's wheight, can you tell me what would be the perfect spring rate for my car? I usually go by what ksport and some other guys tell me, than i test it, but i was wondering if anyone would know an equation or something?

Perfect spring rate? That depends on the course a really smooth course equals higher spring rates, Rough course softer.

Typical is about 950 front and 1050 rear with a 58/42 f/r weight bias.
21mm front bar and 20 mm rear bar

jlaymanmoto · 09-22-2009, 11:47 PM

K, so I did some research to learn what the hell you guys are talking about and I got this from wikipedia.

The motion ratio of a mechanism is the ratio of the displacement of the point of interest to that of another point.

The most common example is in a vehicle's suspension, where it is used to describe the displacement and forces in the springs and shock absorbers. The force in the spring is (roughly) the vertical force at the contact patch divided by the motion ratio, and the wheel rate is the spring rate divided by the motion ratio squared.

This is described as the Installation Ratio in the reference. Motion Ratio is the more common term in the industry, but sometimes is used to mean the inverse of the above definition.

Maybe someone could explain this in

layman's

terms. I would greatly appreciate it. I am going to try to start getting on a road coarse once next season starts and I would like to learn everything that I can get my hands on. Any help would be appreciated.

**1LAPSRT** · 09-23-2009, 06:17 AM

It's basically a way to determine your actual spring rates as they apply to your vehicle.

A 500 lb spring on a car with a 1 : 0.75 motion ratio is actually is doing the work of a 375 lb spring (500*0.75=375).

Since our ratio is 1:1 a 500 lb spring is a 500lb spring.

Ta-Da...... I think!

jlaymanmoto · 09-23-2009, 10:56 AM

Oh, OK, thanks doug.

That is way easier than freakin wikipedia's albert einstien mumbo jumbo.

K, also are those spring rates that nemo said, are those combined for front and rear, ie 950 front meaning 475 lbs/in Front left and 475 lbs/in front right making a combined front 950 lbs/in?

**1LAPSRT** · 09-23-2009, 10:41 PM

Quote: Originally Posted by jlaymanmoto

Oh, OK, thanks doug.

That is way easier than freakin wikipedia's albert einstien mumbo jumbo.

K, also are those spring rates that nemo said, are those combined for front and rear, ie 950 front meaning 475 lbs/in Front left and 475 lbs/in front right making a combined front 950 lbs/in?

Nope...not combined...individually!

I run 650's front and 850's rear. May change them though...more research to do!