follow ft86club on our blog, twitter or facebook.
FT86CLUB
Ft86Club
Speed By Design
Register Garage Members List Calendar Search Today's Posts Mark Forums Read

Go Back   Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community - FT86CLUB > Technical Topics > Suspension | Chassis | Brakes -- Sponsored by 949 Racing

Suspension | Chassis | Brakes -- Sponsored by 949 Racing Relating to suspension, chassis, and brakes. Sponsored by 949 Racing.


User Tag List

Reply
 
Thread Tools Search this Thread
Old 07-09-2014, 11:22 PM   #1
kayoh
Senior Member
 
kayoh's Avatar
 
Join Date: Aug 2012
Drives: 2014 SWP Limited BRZ
Location: Seattle, WA
Posts: 290
Thanks: 118
Thanked 113 Times in 69 Posts
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Need help picking Springs? This tool will help.

Hey guys, I'm not much of a poster but I figured that I'd share some information that has been helpful for me.

When picking the springs for my car I wanted to eliminate the wheel gap and at the same time maintain the stock feel for the handling of the car.

Below is a link to a spreadsheet I made with various springs and their advertised spring ratios. I've also calculated the "actual" ratios specific for the twins and how springs will affect the under-steer/over-steer of your car when accounting for the motion-ratio.

If there are any mistakes or things that I've missed I'll be more than happy to make the corrections.

The top portion is for the BRZ and the bottom for the FRS
Link:
https://docs.google.com/spreadsheet/...VE&usp=sharing
__________________
kayoh is offline   Reply With Quote
The Following 8 Users Say Thank You to kayoh For This Useful Post:
8R6 (07-10-2014), Black Tire (01-06-2015), BrandonB (07-10-2014), Createddeleted (07-09-2014), fstlane (07-09-2014), Racecomp Engineering (07-10-2014), SikCee (07-11-2014), SportInjected (07-09-2014)
Old 07-09-2014, 11:46 PM   #2
Createddeleted
Senior Member
 
Join Date: Mar 2014
Drives: 2014 BRZ - 2004 GLI
Location: Texas
Posts: 328
Thanks: 255
Thanked 228 Times in 122 Posts
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Thanks for your work
Createddeleted is offline   Reply With Quote
Old 07-10-2014, 02:12 AM   #3
8R6
Senior Member
 
8R6's Avatar
 
Join Date: Jan 2014
Drives: FRS
Location: SoCal
Posts: 2,086
Thanks: 2,738
Thanked 1,338 Times in 746 Posts
Mentioned: 30 Post(s)
Tagged: 2 Thread(s)
dang a lot of work to almost be like this thread http://www.ft86club.com/forums/showthread.php?t=8739

[edit] just noticed the "actual" column. thats pretty helpful to know!

btw, how were these actuals calculated? kinda weird how all the rear spring rates for all the brands are around the same range but their advertised numbers are all over the place
__________________
8R6 is offline   Reply With Quote
Old 07-10-2014, 03:29 AM   #4
kayoh
Senior Member
 
kayoh's Avatar
 
Join Date: Aug 2012
Drives: 2014 SWP Limited BRZ
Location: Seattle, WA
Posts: 290
Thanks: 118
Thanked 113 Times in 69 Posts
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quote:
Originally Posted by BRGT86 View Post
dang a lot of work to almost be like this thread http://www.ft86club.com/forums/showthread.php?t=8739

[edit] just noticed the "actual" column. thats pretty helpful to know!

btw, how were these actuals calculated? kinda weird how all the rear spring rates for all the brands are around the same range but their advertised numbers are all over the place
So to calculate the actuals I took the information from here:
http://www.ft86club.com/forums/showthread.php?t=9936

In the "Failing to Account for the Motion Ratio" section the front of the BRZ/FRS the motion ratio is close to 1 and for the rear it's closer to .75.

You can think of our suspension in the shape of an upside-down trapezoid instead of a rectangle. The rear struts sit closer to the middle of the car than the front struts, hence the .75 number.

Towards the end of that section he mentions, "To get the "wheel" rate of the spring, or the spring rate at the wheel, you multiply the spring rate by the square of the motion ratio."

The Square of the motion ratio is .75 * .75 = 0.5625

Taking this into account, the spring rate of the front is essentially the advertised spring rate. However, for the rears, you want to multiply the the square of the motion ratio (0.5625) to the advertised spring rate of the rears.

So for a spring rated at (F 3.16k/R 3.88k) the Front remains the same 3.16k, but for the rears it's 3.88k * 0.5625 which gives you an "actual" spring rate of 2.1825k.

On a side note, I decided to go with the RS-R Super Downs because they have a spring rate bias that's approx. 6% stiffer than stock and with better wheels I'll be even closer to that stock feeling.

[edit]Racecomp Engineering if I'm missing anything please let me know.
__________________

Last edited by kayoh; 07-10-2014 at 01:04 PM.
kayoh is offline   Reply With Quote
The Following User Says Thank You to kayoh For This Useful Post:
8R6 (07-10-2014)
Old 07-10-2014, 11:06 AM   #5
Racecomp Engineering
 
Join Date: Nov 2011
Drives: 2016 BRZ, 2012 Paris Di2 & 2018 STI
Location: Severn, MD
Posts: 5,161
Thanks: 3,146
Thanked 6,906 Times in 2,795 Posts
Mentioned: 291 Post(s)
Tagged: 9 Thread(s)
Send a message via AIM to Racecomp Engineering
Two things I'll mention:

1. Good work!

2. There's more to understeer/oversteer balance than just the main spring rates. This car is very bumpstop active, so lowering an inch up front with soft rates means you're getting a LOT of spring rate from the bumpstop itself. So the rates on the springs are almost secondary once you're in a corner and the body is rolling...the spring rate of the stock bumpstops gets progressively very firm. So lowering 1 inch with the same spring rates as stock will definitely change the handling (and ride) of the car. Even lowering with the same % increase in rate front and rear can change balance. Maybe simply

Suspension geometry is also a factor and you did note this fact in the spreadsheet.. Lowering an inch up front has a different effect on geometry than lowering an inch in the rear. Maybe mention the bumpstop thing too and/or change the wording (the 2 examples especially...putting a number on how much % more/less understeer there is than stock is very tricky). You could say the change the spring rate bias X% or something.

I would also note which springs include replacement bumpstops (our RCE springs and Eibach).

- Andy
Racecomp Engineering is offline   Reply With Quote
The Following User Says Thank You to Racecomp Engineering For This Useful Post:
kayoh (07-10-2014)
Old 07-10-2014, 11:29 AM   #6
STV3
Seņor Member
 
STV3's Avatar
 
Join Date: May 2013
Drives: 2013 Scion FR-S
Location: Rockland County NY
Posts: 1,607
Thanks: 1,103
Thanked 1,322 Times in 645 Posts
Mentioned: 17 Post(s)
Tagged: 4 Thread(s)
Anyone have any data on the TRD lowering springs yet? I want a lowering spring that will keep the ride quality and handling as close to stock as possible. I love the way the stock suspension feels but I would like to get minimize the wheel gap.
STV3 is offline   Reply With Quote
Old 07-10-2014, 01:03 PM   #7
kayoh
Senior Member
 
kayoh's Avatar
 
Join Date: Aug 2012
Drives: 2014 SWP Limited BRZ
Location: Seattle, WA
Posts: 290
Thanks: 118
Thanked 113 Times in 69 Posts
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quote:
Originally Posted by Racecomp Engineering View Post
Two things I'll mention:

1. Good work!

2. There's more to understeer/oversteer balance than just the main spring rates. This car is very bumpstop active, so lowering an inch up front with soft rates means you're getting a LOT of spring rate from the bumpstop itself. So the rates on the springs are almost secondary once you're in a corner and the body is rolling...the spring rate of the stock bumpstops gets progressively very firm. So lowering 1 inch with the same spring rates as stock will definitely change the handling (and ride) of the car. Even lowering with the same % increase in rate front and rear can change balance. Maybe simply

Suspension geometry is also a factor and you did note this fact in the spreadsheet.. Lowering an inch up front has a different effect on geometry than lowering an inch in the rear. Maybe mention the bumpstop thing too and/or change the wording (the 2 examples especially...putting a number on how much % more/less understeer there is than stock is very tricky). You could say the change the spring rate bias X% or something.

I would also note which springs include replacement bumpstops (our RCE springs and Eibach).

- Andy

Thanks for your input! I'll definitely update the spreadsheet later tonight, and add more information regarding bumpstops and correct word usage.
__________________
kayoh is offline   Reply With Quote
The Following User Says Thank You to kayoh For This Useful Post:
Racecomp Engineering (07-10-2014)
 
Reply

Tags
lower, motion ratio, springs, stock, wheel gap

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Picking my BRZ up out of state Kyle106 BRZ First-Gen (2012+) -- General Topics 20 03-26-2013 04:50 PM
Picking up BRZ tomorrow... sub_stance CANADA 17 03-25-2013 01:48 AM
Anyone picking up a Nexus 4 or 10? Available Now ironchef Off-Topic Lounge [WARNING: NO POLITICS] 0 11-13-2012 02:19 PM
Picking her up at 5! remorse87 Scion FR-S / Toyota 86 GT86 General Forum 14 10-07-2012 11:51 AM
Need Help Picking New Phone Calais Off-Topic Lounge [WARNING: NO POLITICS] 10 02-22-2011 05:29 PM


All times are GMT -4. The time now is 03:58 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2023, vBulletin Solutions Inc.
User Alert System provided by Advanced User Tagging v3.3.0 (Lite) - vBulletin Mods & Addons Copyright © 2023 DragonByte Technologies Ltd.

Garage vBulletin Plugins by Drive Thru Online, Inc.