Developing a Proper Suspension Model - Page 22 - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

wparsons · 07-16-2015, 02:01 PM

Maximum toe out will be with the LCA level, any movement in either direction will cause toe in. You'd have to see where the LCA was at the height you had it aligned at.

The toe link is shorter than the LCA, and is in front of the rear axle.

Shankenstein · 07-16-2015, 02:01 PM

Quote:

Originally Posted by 7thgear

asked this in a separate thread but got a hypothetical answer.

Does toe change in the rear with ride height changes?

And if it does even a little bit, which way does it change when the car goes up or down?

It's a different car and different suspension geometry... but the Miata rear toe does not change with suspension travel.

Link to MX-5 Forum

Our geometry will have a toe curve, but if you design suspension appropriately, the curve can flatten across a significant range (as with the Miata). I suspect that our suspension was designed similarly.

Edit:
Found the toe curve on an S2000. It's got a spread of 5/16" throughout the 5-1/2" of travel.

7thgear · 07-19-2015, 07:08 AM

soOoooo

experiment time

car currently has toe out in the rear, OEM everything

I put a plank on two jackstands at around center height of the wheel and measured the distance between the tire and plank (back and front of tire) with no spare in the car and an empty tank

then I loaded my trunk with 100 lb of weight and asked my dad (~220lb) to stand in it as well.

under compression the car goes into negative camber, so the distances from the plank increase... and the front of the tire increased by 1.2~3mm more than the back, meaning the front of the tire tucked in more than the back, which means toe-in under compression given my initial settings.

I hope

7thgear · 07-30-2015, 12:21 PM

do we know the length of our scrub radius in the front? (distance between OEM wheel centerline and the strut inclination where they meet at the ground?

fika84 · 07-30-2015, 01:56 PM

Not that I know of.. These guys have the data, but they charge for it... http://www.morsemeasurements.com/

SkiRideDrive · 07-30-2015, 02:15 PM

Subscribed! I will read through later. I did suspension design in FSAE for 4 years. Psyched for this one and hope I can contribute.

RBbugBITme · 09-23-2015, 06:13 PM

Not sure if I'm missing something but the OP has the rear motion ratio around .85 and links another thread that has it around .75.
From a sketch I built off the factory 3D model I have the MR changing from .768 at 2" of bump to .758 at 2" of droop so its .763 at at OEM ride height.

Shankenstein · 09-23-2015, 09:38 PM

Quote:

Originally Posted by RBbugBITme

Not sure if I'm missing something but the OP has the rear motion ratio around .85 and links another thread that has it around .75.
From a sketch I built off the factory 3D model I have the MR changing from .768 at 2" of bump to .758 at 2" of droop so its .763 at at OEM ride height.

Whenever a forum member pipes up with new data, I generally assume that they're correct (because they took the effort to correct me). Laziness and bad science.

Seems like the old data was better in this case.

If you see any other areas we can improve, don't hesitate to speak up.

cdrazic93 · 01-18-2016, 04:09 PM

Uh this hasent been updated in quite some time, but quick question. struts; are they simple or complex harmonic motion?

RBbugBITme · 01-18-2016, 04:33 PM

College level analysis = simple
Real world analysis = complex

cdrazic93 · 01-18-2016, 04:37 PM

Quote:

Originally Posted by RBbugBITme

College level analysis = simple
Real world analysis = complex

I had a feeling itd be complex, currently my SHM and motion equations are of only the first and second order normal diff eq lol

infinity21 · 04-22-2016, 10:30 AM

Hey guys, I have slight rubbing between my rear tires and fender on the outside. I'm wondering if installing whiteline rear upper control arm bushing will be enough to get the tire tucked in. I'm currently running 17x9 +35 with 255-40-17 RS3 on coilovers and SPC rear LCA. Anyone know how much maxing out the UCA bushing will tuck in the top of the tire?

Shankenstein · 06-24-2016, 11:58 AM

Ran across an interesting blog post from a Miata dude who talks about developing a semi-active suspension system.

LINK to Article

Basic idea is to use valves to open bleed paths (compression and rebound, with check valves to keep each path independent). "Skyhook" theory is simple enough, since you support/stiffen the vehicle to resist roll and pitch.

I'm betting that we could develop a simple feed-forward system that uses gyroscope data with some filtering/dead zones to keep things robustly stable. A potentiometer could let you dial in the aggressiveness of valve opening.

Here's another thread about similar topics: LINK to Miata.net

Tein's EFDC Active Pro does modify damping... but this type of system is pretty slow and uses motors on the adjustment knob.
Ohlins has a similar system:
LINK to SportRider

cool7 · 10-17-2016, 01:10 PM

I searched for "rear lateral link" in this thread and didn't find any results.

Do we know how this link affects rear toe and caster under suspension travel?

The link in question is the left green arrow

07-19-2015, 07:08 AM	#297
7thgear i'm sorry, what? Join Date: Jan 2012 Drives: Canada Location: I rock a beat harder than you can beat it with rocks Posts: 4,399 Thanks: 357 Thanked 2,506 Times in 1,268 Posts Mentioned: 40 Post(s) Tagged: 3 Thread(s)	soOoooo experiment time car currently has toe out in the rear, OEM everything I put a plank on two jackstands at around center height of the wheel and measured the distance between the tire and plank (back and front of tire) with no spare in the car and an empty tank then I loaded my trunk with 100 lb of weight and asked my dad (~220lb) to stand in it as well. under compression the car goes into negative camber, so the distances from the plank increase... and the front of the tire increased by 1.2~3mm more than the back, meaning the front of the tire tucked in more than the back, which means toe-in under compression given my initial settings. I hope __________________ don't you think if I was wrong, I'd know it?

07-30-2015, 12:21 PM	#298
7thgear i'm sorry, what? Join Date: Jan 2012 Drives: Canada Location: I rock a beat harder than you can beat it with rocks Posts: 4,399 Thanks: 357 Thanked 2,506 Times in 1,268 Posts Mentioned: 40 Post(s) Tagged: 3 Thread(s)	do we know the length of our scrub radius in the front? (distance between OEM wheel centerline and the strut inclination where they meet at the ground? __________________ don't you think if I was wrong, I'd know it?

09-23-2015, 06:13 PM	#301
RBbugBITme Senior Member Join Date: Jun 2014 Drives: S60R/Corvette Location: Reading, PA Posts: 104 Thanks: 4 Thanked 236 Times in 59 Posts Mentioned: 7 Post(s) Tagged: 0 Thread(s)	Not sure if I'm missing something but the OP has the rear motion ratio around .85 and links another thread that has it around .75. From a sketch I built off the factory 3D model I have the MR changing from .768 at 2" of bump to .758 at 2" of droop so its .763 at at OEM ride height. __________________ Ryan M. Strange Engineering Director of Suspension Development

01-18-2016, 04:09 PM	#303
cdrazic93 Junior Join Date: Aug 2013 Drives: a car Location: Probably at school Posts: 4,341 Thanks: 3,184 Thanked 2,512 Times in 1,502 Posts Mentioned: 20 Post(s) Tagged: 0 Thread(s)	Uh this hasent been updated in quite some time, but quick question. struts; are they simple or complex harmonic motion? __________________ "Ah! What music! They could have never imagined, those pioneers who invented the automobile, that it would posses us like this, our imaginations, our dreams. Men love women, but even more than that, men love CARS!"-Lord Hesketh

01-18-2016, 04:33 PM	#304
RBbugBITme Senior Member Join Date: Jun 2014 Drives: S60R/Corvette Location: Reading, PA Posts: 104 Thanks: 4 Thanked 236 Times in 59 Posts Mentioned: 7 Post(s) Tagged: 0 Thread(s)	College level analysis = simple Real world analysis = complex __________________ Ryan M. Strange Engineering Director of Suspension Development

07-30-2015, 02:15 PM	#300
SkiRideDrive Senior Member Join Date: Jun 2015 Drives: 2015 FRS Location: San Diego Posts: 161 Thanks: 80 Thanked 104 Times in 51 Posts Mentioned: 3 Post(s) Tagged: 0 Thread(s)	Subscribed! I will read through later. I did suspension design in FSAE for 4 years. Psyched for this one and hope I can contribute.

04-22-2016, 10:30 AM	#306
infinity21 Senior Member Join Date: Aug 2014 Drives: 2014 BRZ Sport-tech Location: Toronto, Canada Posts: 125 Thanks: 45 Thanked 66 Times in 50 Posts Mentioned: 5 Post(s) Tagged: 2 Thread(s)	Hey guys, I have slight rubbing between my rear tires and fender on the outside. I'm wondering if installing whiteline rear upper control arm bushing will be enough to get the tire tucked in. I'm currently running 17x9 +35 with 255-40-17 RS3 on coilovers and SPC rear LCA. Anyone know how much maxing out the UCA bushing will tuck in the top of the tire?

06-24-2016, 11:58 AM	#307
Shankenstein Frosty Carrot Join Date: Jan 2013 Drives: The Atomic Carrot Location: Baltimore, MD Posts: 513 Thanks: 272 Thanked 428 Times in 199 Posts Mentioned: 19 Post(s) Tagged: 0 Thread(s)	Ran across an interesting blog post from a Miata dude who talks about developing a semi-active suspension system. LINK to Article Basic idea is to use valves to open bleed paths (compression and rebound, with check valves to keep each path independent). "Skyhook" theory is simple enough, since you support/stiffen the vehicle to resist roll and pitch. I'm betting that we could develop a simple feed-forward system that uses gyroscope data with some filtering/dead zones to keep things robustly stable. A potentiometer could let you dial in the aggressiveness of valve opening. Here's another thread about similar topics: LINK to Miata.net Tein's EFDC Active Pro does modify damping... but this type of system is pretty slow and uses motors on the adjustment knob. Ohlins has a similar system: LINK to SportRider __________________ If you think you're nerd enough, join in the discussions about Suspension and Aerodynamic modelling! Wall of Fame - JDL Auto Design, Raceseng, Vishnu Tuning, Penske Shocks, Nameless, Perrin, RaceComp Engineering, Essex/AP Racing, Verus, RacerX Wall of Shame - aFe Takeda, Wilwood, FA20Club

10-17-2016, 01:10 PM	#308
cool7 Member Join Date: Jul 2015 Drives: BRZ WRB Location: 604 Posts: 14 Thanks: 0 Thanked 0 Times in 0 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	I searched for "rear lateral link" in this thread and didn't find any results. Do we know how this link affects rear toe and caster under suspension travel? The link in question is the left green arrow

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