Another 91 vs 93 Suspension Difference: Anti-Dive - MR2 Owners Club Message Board
 
LinkBack Thread Tools
post #1 of 11 (permalink) Old January 5th, 2010, 11:18 Thread Starter
Wilhelm Raceworks, LLC
click here to visit the sponsor page
 
Alex W's Avatar
 
Join Date: Jan 2005
Location: Bozeman, MT
Age: 34
Posts: 12,547
OldTrader Rating: (120)
Another 91 vs 93 Suspension Difference: Anti-Dive

While swapping to the 93+ front strut rod brackets in preparation for a spherical bearing front strut rod I noticed a difference between the 91 and 93 brackets that nobody talks about. Its tough to measure exactly, but it appears that the 93 brackets lower the front strut rod pivot point by about 1/2", maybe a little less. The effect of this is to raise the front suspension side view instant center from about 8.3" above ground level to about 15.8" above ground level. This will give the 93 suspension nearly twice as much (about 1.9x actually) anti-dive as the 91.

Without knowing the exact location of the CG we can't calculate the exact percentages for either suspension, but if (for example) the 91 has 20% anti-dive then the 93, all else equal, will have 38% anti-dive.

On the subject of anti dive, it is worth noting that increasing caster will decrease anti-dive on a McPherson strut suspension.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Specializing in suspension and handling for the MKII MR2

Custom Koni coilovers and coilover housings, suspension geometry correction kits, camber/caster plates, big brake kits, and more

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
A retro-active build thread for my track / autocross car

Last edited by Alex W; September 21st, 2010 at 09:33.
Alex W is offline  
Sponsored Links
Advertisement
 
post #2 of 11 (permalink) Old January 14th, 2010, 15:15
Registered User
 
Join Date: Mar 2008
Location: Seattle
Posts: 787
OldTrader Rating: (7)
Neat!

For me, the whole anti-dive concept has always been really difficult to visualize. Part of the braking load is transferred to the tires through the suspension pivots and control arms rather than the springs/dampers? Just sounds weird to me.

We always talk about spring rates and damping curves but there is a huge amount of tuning/engineering that goes into the suspension geometry. Makes me wish I studied mech eng instead of elec/comp eng in school.
phatvw is offline  
post #3 of 11 (permalink) Old January 16th, 2010, 16:45 Thread Starter
Wilhelm Raceworks, LLC
click here to visit the sponsor page
 
Alex W's Avatar
 
Join Date: Jan 2005
Location: Bozeman, MT
Age: 34
Posts: 12,547
OldTrader Rating: (120)
Yeah, it took me a while to make sense of it too. Looking from the side of the car, it has to do with where the horizontal plane of the front "control arm" (the combination of the control arm and the strut rod) crosses the vertical plan through the center of gravity. Angling the strut rod down causes the horizontal plane to angle down, causing it to cross the vertical plane closer to the CG.

Basically, it works like a roll center, only for dive instead. Its rarely talked about, but you could define an "anti roll" percentage based on the height of the roll centers vs the CG in the same way that anti dive is commonly used.

I'm looking forward to actually getting to drive it, see if there is a noticeable difference. Unfortunately it will have been 5 months or so since I last drove the car when I get to try it... so it may be tough to tell.
Alex W is offline  
Sponsored Links
Advertisement
 
post #4 of 11 (permalink) Old January 27th, 2010, 18:38
Registered User
 
Join Date: Mar 2004
Location: Panama City Bch Florida
Age: 44
Posts: 6,579
OldTrader Rating: (24)
Quote:
Originally Posted by Alex W
On the subject of anti dive, it is worth noting that increasing caster will decrease anti-dive on a McPherson strut suspension.

Never knew this.....I never heard anything bad about increasing caster other than the fact it increase steering effort but made up for it in on-center feel.
SuperMR2 is offline  
post #5 of 11 (permalink) Old February 25th, 2010, 14:00
Registered User
 
Join Date: Aug 2005
Location: FL
Age: 42
Posts: 3,040
OldTrader Rating: (24)
Would adding 1/2" spacers to the 91 brackets between the body give the same effect?
Blue Bomber is offline  
post #6 of 11 (permalink) Old February 25th, 2010, 15:46 Thread Starter
Wilhelm Raceworks, LLC
click here to visit the sponsor page
 
Alex W's Avatar
 
Join Date: Jan 2005
Location: Bozeman, MT
Age: 34
Posts: 12,547
OldTrader Rating: (120)
Quote:
Originally Posted by Blue Bomber
Would adding 1/2" spacers to the 91 brackets between the body give the same effect?
Yep, it sure would

Although I have to say I much prefer the 93 design (when coupled with a spherical bearing type strut rod). Much more free movement.
Alex W is offline  
post #7 of 11 (permalink) Old April 14th, 2010, 14:01
Registered User
 
Join Date: Oct 2007
Age: 30
Posts: 129
OldTrader Rating: (1)
would there be in gain spacing down the 93 brackets... and if there is a gain would it be more noticeable at higher caster angles?? i have spherical bearing adjustable strut rods.

Matt

Last edited by wrxwalsh; April 14th, 2010 at 14:04.
wrxwalsh is offline  
post #8 of 11 (permalink) Old April 19th, 2010, 09:55 Thread Starter
Wilhelm Raceworks, LLC
click here to visit the sponsor page
 
Alex W's Avatar
 
Join Date: Jan 2005
Location: Bozeman, MT
Age: 34
Posts: 12,547
OldTrader Rating: (120)
Quote:
Originally Posted by wrxwalsh
would there be in gain spacing down the 93 brackets... and if there is a gain would it be more noticeable at higher caster angles?? i have spherical bearing adjustable strut rods.

Matt
As I mentioned in the anti-squat thread, there is such a thing as too much of these effects. I don't know exactly where that point lies, but like everything else in tuning (suspension or otherwise) its all a trade-off. Its possible that dropping the 93 brackets to gain more anti-dive would be beneficial, especially on a car with lots of caster (get you back toward the original 93 anti-dive level), but you need to be careful not to take it too far and be ready to go back if it makes things worse.
Alex W is offline  
post #9 of 11 (permalink) Old April 19th, 2010, 11:36
Registered User
 
Join Date: Oct 2007
Age: 30
Posts: 129
OldTrader Rating: (1)
i realize that this is for r/c cars... when i was in the 6th grade i raced these things quite successfully for a couple of years... however the physics is physics

anti squat
http://www.rc-truckncar-tuning.com/Anti-Squat.html

anti dive
http://www.rc-truckncar-tuning.com/Kick-up.html

Matt
wrxwalsh is offline  
post #10 of 11 (permalink) Old April 19th, 2010, 11:43
Registered User
 
Join Date: Oct 2007
Age: 30
Posts: 129
OldTrader Rating: (1)
im not entirely sure what it changes but on my tension rod it came with spacers to space the rod end left or right of center in the mounting bracket. i assume its to that you can run a higher caster angle without binding the suspension but im not entirely sure... any enlightenment?
wrxwalsh is offline  
post #11 of 11 (permalink) Old April 19th, 2010, 13:24 Thread Starter
Wilhelm Raceworks, LLC
click here to visit the sponsor page
 
Alex W's Avatar
 
Join Date: Jan 2005
Location: Bozeman, MT
Age: 34
Posts: 12,547
OldTrader Rating: (120)
Quote:
Originally Posted by wrxwalsh
im not entirely sure what it changes but on my tension rod it came with spacers to space the rod end left or right of center in the mounting bracket. i assume its to that you can run a higher caster angle without binding the suspension but im not entirely sure... any enlightenment?
Yeah, thats the only reason I can see.
Alex W is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the MR2 Owners Club Message Board forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: (0 members)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may 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
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome