moton spring question

Boosted EVO 9 · Oct 26, 2009, 04:10 PM

i have a set of moton's on my car with JIC springs. 700lb in front and 800lb in back. I'm wanting something a little more streetable. Any suggestions on what I should go with for different springs? In the last 15,000 miles I have only did 2 track days...

**SmikeEvo** · Oct 26, 2009, 06:53 PM

That will be terrible for handling. You do not want a lower rate in the rear. You want a higher rate.

Second, you should contact Moton. You may or may not be able to just change the springs without adjusting the valving.

5k front and 7k rear would be better, if you are set on going that route. Or taking out the Motons.

rawkus · Oct 27, 2009, 08:42 AM

I'm currently running 7k Front 9k Rear and I feel the ride is very streetable on my Cusco Zero 2Rs. Have you adjusted the damping settings? Perhaps you would like to trade coilovers

Dan

LV///R · Oct 27, 2009, 01:48 PM

....nevermind

talentsearch301 · Oct 27, 2009, 05:28 PM

I though the higher spring rate would be on the front ?..?

lfaboulos34 · Oct 27, 2009, 07:18 PM

handlings not going to be good for sure

**SmikeEvo** · Oct 27, 2009, 07:22 PM

Not with the motion ratio on the Evo.

Choosing coilover spring rates for your EVO

Boosted EVO 9 · Oct 29, 2009, 03:27 PM

i've driven this car this way for 2 years and it works just fine. i was only curious if i went a little softer, so the bumps were not as hard hitting, what would be the best choice.

**SmikeEvo** · Oct 29, 2009, 03:40 PM

Works fine and handle well are two different things

Boosted EVO 9 · Oct 30, 2009, 06:48 AM

it handles freaking amazing. was fastest car out of 25 cars at first 2 track days on street tires.

**SmikeEvo** · Oct 30, 2009, 06:59 AM

I think you need to understand what motion ratio means:

Quote:

Originally Posted by GTWORX.com

First, if you don't really care about performance, than it doesn't matter. Get coilovers and get the drop you want. You can close this thread now.

But if you do care about performance, you're doing yourself and your car a disservice by getting the incorrect spring rates.

Second, I'm not going to spell out exactly what are the "best" spring rates. There are so many factors at play. Having a suspension tuner design a suspension for your specific needs and preferences is the best way to go.

This is intended to be a very rough guide people choosing spring rates for coilovers. It is not comprehensive, every car and driver is a little different, I am not a suspension master, and all that stuff.

Crappy spring rates are a problem with several brands of off the shelf coilovers. It does not necessarily mean the coilovers are bad, but the springs should be swapped out if performance is the goal.

Basics

Too stiff. You don't need 14kg spring rates on street tires. You don't have enough grip to generate enough body roll to need super stiff spring rates. You'll likely be overheating your tires. I would recommend R Compounds and stickier when you go past 10kg springs.

This is not a hard rule though and there are exceptions including auto-x, where physics do not really make as much sense.

Incorrect Spring Rates

What do I mean by incorrect?

Usually when you see spring rates for a set of coilovers it's something like 8kg/6kg. Makes sense, since the EVO is a little front heavy right? Well yes, but there's another factor at play.

The EVO has a multi-link rear suspension. The rear EVO spring is mounted inwards on the arm just a little bit. Unlike the front strut which is pretty much mounted at the hub, a 5k spring rate in the rear does not mean a 5k rate at the wheel. Essentially the suspension arm is a moment arm....placing the spring inwards towards the pivot point means it needs to be stiffer. Sometimes you'll see people mention the "motion ratio." For the front EVO with the strut based suspennsion, it's close to 1 (almost). For the rear, it's somewhere between .6 to .9.

To get the "wheel" rate, you multiply the spring rate by the square of the motion ratio.

So that 8kg/6kg is really more like 8kg/3.7kg ish.

Can you make it work? Kinda. A lot of front camber and a rear swaybar help. But a lot of front camber reduces your contact patch in a straight line and a rear swaybar reduces suspension independence. And then there's the suspension frequency to look at too. So basically yes....you want a slightly stiffer rear spring than the front for the EVO 8 and 9. At the very least, even front and rear spring rates. Top auto-x setups are generally like 12k/16k, but i wouldn't do that for the street or track since that can be a handful.

- Andrew

**SmikeEvo** · Oct 30, 2009, 07:05 AM

Quote:

Originally Posted by Boosted EVO 9

it handles freaking amazing. was fastest car out of 25 cars at first 2 track days on street tires.

I see you corrected your first post - that is a correct spring match up.

You will not want to go to a 7k front / 5k rear, which you first posted. A 5k front and 7k rear would be a more optimal setup in terms of motion ratio.

GTWORX.com · Oct 30, 2009, 10:51 AM

We can get you Swift coilover springs if you're interested.

- Andrew

rawkus · Oct 30, 2009, 01:43 PM

I'm still down for trading the Cusco's for the Moton's... seems fair as I rarely drive on the street, might as well put the Moton's to good use

Dan

Boosted EVO 9 · Oct 30, 2009, 01:54 PM

Quote:

Originally Posted by rawkus

I'm still down for trading the Cusco's for the Moton's... seems fair as I rarely drive on the street, might as well put the Moton's to good use

Dan

what are you smoking?