Notices
Autocross/Road SCCA Solo II, SCCA Club Racing, Redline Track Events, Speed Trial, Speed Ventures, Grand-Am Cup, JGTC, Procar Australia

Unsprung weights, motion ratios, and natural frequencies?

Old 03-26-2010, 06:00 AM
  #1  
senorcole86
Registered User
Thread Starter
 
Join Date: Jan 2009
Location: Here
Posts: 10
Likes: 0
Received 0 Likes on 0 Posts
Default Unsprung weights, motion ratios, and natural frequencies?

I tried posting this in the suspension section, but nobody seems to have any answers. I've seen some pretty technical discussions going on over here, so hopefully y'all can help me out.

I apologize if this information is available elsewhere, I honestly couldn't find it.

I was wondering if anybody had estimates for any of these numbers for a g35 coupe (or 350z) in stock form.

1) unsprung weights
2) motion ratios (I've heard 0.76 F and 0.39 R, but nobody was sure)
3) natural frequencies
4) Corner weights (don't have access to a set of scales, sorry)

I'm picking out suspension components and trying to get a really good handle on the natural frequencies of the vehicle. Thanks in advance guys, have a good one.
senorcole86 is offline  
Old 03-26-2010, 07:44 AM
  #2  
betamotorsports
Registered User
iTrader: (1)
 
betamotorsports's Avatar
 
Join Date: Jul 2006
Location: La Habra, CA, USA
Posts: 1,393
Likes: 0
Received 2 Likes on 2 Posts
Default

Corner Weights

2006 350Z Base with 1/2 tank of fuel, not spare, tools, no driver.

LF 889 RF 903
LR 694 RR 730

Left Side 1583 49.2%
Right Side 1634 50.8%
Front 1792 55.7%
Rear 44.3%
Cross (RF/LR) 1598 49.7%

Unsprung Weight

Stock spring, Koni Sport, Enkei RPF1 18 x 10 w/Hankook R214 285/30-10, stock calipers, Hawk DTC70 pads.

Front 135 lbs. (estimated)
Rear 130 lbs. (estimated)

Motion ratios and bump steer curve are already posted in this forum. Just do a search.

Last edited by betamotorsports; 03-26-2010 at 07:46 AM.
betamotorsports is offline  
Old 03-26-2010, 11:26 AM
  #3  
senorcole86
Registered User
Thread Starter
 
Join Date: Jan 2009
Location: Here
Posts: 10
Likes: 0
Received 0 Likes on 0 Posts
Default

I really have searched, and I've come up with conflicting information. Here's what I've found so far for motion ratios.

1) 0.79 F 0.36 R
2) 0.53 F (with 10 degree AC) 0.36 R
3) 0.688 F 0.649 R

The third option sounds more correct considering the stock spring rates, but I've seen the other two options quoted much more frequently. Which is correct?

Thank you for the information on corner weights and unsprung weights. I'll tack on the difference in wheel weights (I'm rolling on the Infiniti OEM 19's) and call it a day.
senorcole86 is offline  
Old 03-26-2010, 12:16 PM
  #4  
betamotorsports
Registered User
iTrader: (1)
 
betamotorsports's Avatar
 
Join Date: Jul 2006
Location: La Habra, CA, USA
Posts: 1,393
Likes: 0
Received 2 Likes on 2 Posts
Default

Be careful with my unsprung weight numbers. They are estimates based on weighing the main components separately over a period of time. I've used the third motion ratio numbers for my calcs and things worked out fine.
betamotorsports is offline  
Old 03-26-2010, 12:24 PM
  #5  
Zazz93
Registered User
iTrader: (2)
 
Zazz93's Avatar
 
Join Date: Jul 2009
Location: So Cal
Posts: 1,767
Received 7 Likes on 5 Posts
Default

How would you use the motion ratios? I can't see an application unless your planning on mod'ing a pickup point.

Last edited by Zazz93; 03-26-2010 at 12:26 PM.
Zazz93 is offline  
Old 03-29-2010, 05:06 AM
  #6  
senorcole86
Registered User
Thread Starter
 
Join Date: Jan 2009
Location: Here
Posts: 10
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by betamotorsports View Post
Be careful with my unsprung weight numbers. They are estimates based on weighing the main components separately over a period of time. I've used the third motion ratio numbers for my calcs and things worked out fine.
Perfect, thanks a lot. I was hoping those were the correct ones, the other didn't make much sense when you started doing the math.

Originally Posted by Zazz93 View Post
How would you use the motion ratios? I can't see an application unless your planning on mod'ing a pickup point.
To figure out wheel rates with the stock pickup points.
senorcole86 is offline  
Old 03-29-2010, 05:33 AM
  #7  
Zazz93
Registered User
iTrader: (2)
 
Zazz93's Avatar
 
Join Date: Jul 2009
Location: So Cal
Posts: 1,767
Received 7 Likes on 5 Posts
Default

Good to know, but I'm referring to what your end result is. Are you corner balancing the car, trying to get a idea for a new spring package, etc. Just wondering what I'm missing, and could be looking at.
Zazz93 is offline  
Old 03-29-2010, 08:20 AM
  #8  
senorcole86
Registered User
Thread Starter
 
Join Date: Jan 2009
Location: Here
Posts: 10
Likes: 0
Received 0 Likes on 0 Posts
Default

Yeah, I'm just running the numbers for different aftermarket suspension kits. Seeing how the roll stiffness and natural frequencies are affected. There's not a whole lot I could do until I get the springs on my car, but I'm a mechanical engineer and I like running the numbers . Makes me feel better and I like to make sure everything makes sense before I buy the stuff.
senorcole86 is offline  
Old 03-29-2010, 08:24 AM
  #9  
Zazz93
Registered User
iTrader: (2)
 
Zazz93's Avatar
 
Join Date: Jul 2009
Location: So Cal
Posts: 1,767
Received 7 Likes on 5 Posts
Default

That's a great way double check the company has done their research and not just spec'ed a part because it just looked like a good idea.
Zazz93 is offline  
Old 03-30-2010, 06:35 AM
  #10  
diablox1
Registered User
iTrader: (7)
 
Join Date: Jul 2007
Location: CaliFTMFGDW OMFG LMFAO LOL WUT
Posts: 976
Likes: 0
Received 0 Likes on 0 Posts
Default

+1 as an ME myself too i am forever doomed to run numbers like that. ive been surprised at some of the numbers & conclusions I've come up with from so called performance parts though.

Last edited by diablox1; 03-30-2010 at 06:37 AM.
diablox1 is offline  
Old 03-31-2010, 06:21 PM
  #11  
SGSash
Vendor - Former Vendor
iTrader: (3)
 
Join Date: Jul 2007
Location: Brampton, ON
Posts: 469
Likes: 0
Received 1 Like on 1 Post
Default

Common sense tells us there is no way the rear motion ratio can be 0.36 guys!
SGSash is offline  
Old 04-06-2010, 07:35 AM
  #12  
Zazz93
Registered User
iTrader: (2)
 
Zazz93's Avatar
 
Join Date: Jul 2009
Location: So Cal
Posts: 1,767
Received 7 Likes on 5 Posts
Default

Originally Posted by SGSash View Post
Common sense tells us there is no way the rear motion ratio can be 0.36 guys!
Good find Sash,

Found a calculation chart from third party's site. On SPL's website under the 350z's suspension area (springs to be precise). It has a Excel Calc that shows the ratio around 1.66 (Note SPL listed this as an inverse relationship than what is generally measured, spring to wheel Vs wheel to spring motion).

http://www.splparts.com/main4/parts/...Calculator.xls

Last edited by Zazz93; 01-13-2011 at 08:58 AM.
Zazz93 is offline  
Old 08-02-2016, 07:57 PM
  #13  
BeaverMeat
Registered User
 
Join Date: Aug 2016
Location: Saskatchewan
Posts: 12
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by SGSash View Post
Common sense tells us there is no way the rear motion ratio can be 0.36 guys!
Nechro bump!

From my understanding there are two points to calculate from at the rear.

Rear OEM coil ratio is 0.36. The rear shock loaction ratio is 0.59. Is that used when your calculating for a proper rear mounted coilover?

Originally Posted by Zazz93 View Post
Good find Sash,

Found a calculation chart from third party's site. On SPL's website under the 350z's suspension area (springs to be precise). It has a Excel Calc that shows the ratio around 1.66 (Note SPL listed this as an inverse relationship than what is generally measured, spring to wheel Vs wheel to spring motion).

http://www.splparts.com/main4/parts/...Calculator.xls
How is the front calculated?

Last edited by BeaverMeat; 08-02-2016 at 08:05 PM.
BeaverMeat is offline  
Old 08-02-2016, 09:59 PM
  #14  
terrasmak
Super Moderator
MY350Z.COM
iTrader: (8)
 
terrasmak's Avatar
 
Join Date: Jan 2007
Location: Sin City
Posts: 25,512
Received 1,108 Likes on 813 Posts
Default

Originally Posted by BeaverMeat View Post
Nechro bump!

From my understanding there are two points to calculate from at the rear.

Rear OEM coil ratio is 0.36. The rear shock loaction ratio is 0.59. Is that used when your calculating for a proper rear mounted coilover?



How is the front calculated?
.97 is commonly used in the rear when the spring is mounted on the shock. Front I would have to look, but I thought I'd was like .73 or .68
terrasmak is online now  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
1973camarolt
Drivetrain
5
10-11-2015 01:26 PM
FromGtoZ
Intake Exhaust
2
09-20-2015 03:41 PM
Shane86
Autocross/Road
2
09-17-2015 05:33 PM
etkms
Engine & Drivetrain
24
09-13-2015 11:10 AM


Thread Tools
Search this Thread
Quick Reply: Unsprung weights, motion ratios, and natural frequencies?


Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: