Welcome to the North American Subaru Impreza Owners Club Friday December 26, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
Click here to visit TireRack
Brakes & Suspension Forum sponsored by The Tire Rack

Losing traction? Need new tires?
Click here to visit the NASIOC Upgrade Garage...
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Brakes, Steering & Suspension

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 05-16-2007, 03:05 AM   #1
stretchsje
Scooby Newbie
 
Member#: 107389
Join Date: Feb 2006
Chapter/Region: TXIC
Vehicle:
2014 Honda Odyssey

Default How to choose your own spring rates (and get the spring frequencies correct)

I made a spring frequency calculator in Excel. Unlike anything else I've seen out there, this automatically selects a rear spring rate so that the spring frequency in the rear is appropriately higher based on the vehicle speed you want to optimize for. From there, one would dial in over or understeer using sway bars as needed.

You pick the front spring rate according to the ride comfort you would like- use the calculated spring frequency as a guideline here. Generally speaking, you'll want the front spring frequency to be around 1.0-1.2 for a family sedan, 1.5-1.7 for a sports car, and 2.0-2.2 for a race car.

Download the spreadsheet: http://putstuff.putfile.com/79647/6261372

For more reading on spring frequency selection, I recommend this: http://www.optimumg.com/techtips/Spr...Tech_Tip_1.pdf
Another good link: http://www.wincom.net/trog/autocross_secrets5.html
Yet another: http://www.smithees-racetech.com.au/...cefactors.html

I'm not suggesting this calculation is smarter than human trial and error since it certainly cannot account for other limitations or circumstances on the car. It just follows the guidelines taught at the above links, so read them to understand this calculation. The default values in the spreadsheet are for an STI; we see the rear spring rate is optimized for a "flat" ride at 70mph.

Anyway, let me know what you think! The subject of spring frequencies is certainly one that is wide open for discussion.
* Registered users of the site do not see these ads.

Last edited by stretchsje; 05-16-2007 at 03:21 AM.
stretchsje is offline   Reply With Quote
Old 05-16-2007, 11:10 AM   #2
mattxander12
Scooby Specialist
 
Member#: 111067
Join Date: Mar 2006
Chapter/Region: MWSOC
Location: Chicago, IL
Vehicle:
2002 Old and
busted.

Default

So what about choosing which speed you want to maximize for ?
for autoX speeds: ?
for DD-occasional Auto-X speeds: ?

Which do you choose ?
mattxander12 is offline   Reply With Quote
Old 05-16-2007, 02:55 PM   #3
stretchsje
Scooby Newbie
 
Member#: 107389
Join Date: Feb 2006
Chapter/Region: TXIC
Vehicle:
2014 Honda Odyssey

Default

I'd really like to defer your questions to someone else- I made the spreadsheet to learn about spring frequencies, not to share what I've already learned. So really, I'm not an expert. However, since nobody else is chiming in, I'll take a stab.

Optimizing for really low speeds is nearly impossible because by the time a bump reaches your rear tires, the front tires will have already settled. This is expecially true when running high spring frequencies- since at 2hz the front of the car will have fully oscillated in only half a second, the rear doesn't have much opportunity to catch up. This would mean running much, much higher spring frequencies in the rear (as the spreadsheet shows). Maybe that would work very well, but I doubt it.

So, depending on your chosen spring rates, I don't think it'd make sense to optimize for under 60mph. You want to optimize for the average speed you find yourself driving at, so if you optimize for 70mph, both 60mph and 85mph will still feel pretty good. Maybe road race cars would optimize for a slightly higher speed, but 60-80mph is a pretty typical speed for hitting rumble strips, right?

That's about what Subaru optimized for in the STI (and even the JDM Pink springs): 70-80mph. I've read the generalized rule-of-thumb for street and race cars alike is to make the rear 0.1 to 0.3 Hz higher than the front, and again, both the USDM and JDM STI spring rates follow this guideline.
stretchsje is offline   Reply With Quote
Reply

Thread Tools
Display Modes

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
Any DIY on how to make your own speaker spacers?? Alan l. Car Audio, Video & Security 7 05-12-2006 01:17 PM
How to make your own jet bike CSULBwagon Off-Topic 7 10-28-2005 06:21 PM
How to build your own $1199 contemporary bed ockS Off-Topic 25 09-14-2005 07:35 PM
how to make your own axle-back iloveturbos Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo) 4 01-17-2003 04:17 AM
How to do your own Blue or Red Lights Free! Reiflex Interior & Exterior Modification 28 12-12-2000 10:58 PM


All times are GMT -4. The time now is 02:56 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.