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Author Topic: Sways vs. spring rate (long and a little technical)  (Read 15058 times)
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dvdreith
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« Reply #15 on: March 15, 2011, 10:01:31 AM »

It is solo hard to post with this darn phone!!
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'95MSM
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« Reply #16 on: March 15, 2011, 04:21:28 PM »

In regards to the OP by 95MSM, I completely agree for the process of reducing roll by first springs, then anti-roll (sway) bars.  My MSM and NA's suspensions are tuned to this very concept (both have MSM stock size anti-roll bars).

Can I get an AMEN?


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« Reply #17 on: March 15, 2011, 04:24:52 PM »

I thought we would get a post or two from Michael Wootten on this thread since he has posted that adding big bars generates more grip.
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3.63 ring & pinion FM content: Blouch compressor mod, FM-Link, i/c & no-MAF intake.   BEGi: Stainless SGDP w/ metal core performance cat.   Custom stuff: Compressor clocked downward w/ new i/c pipe, big radius throttle elbow, 2.5" mid-pipe w/ Hushpower II, dual 2" axle-back w/ open Supertrapps, Toyota 4 pc cop ignition

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mr_hyde
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« Reply #18 on: March 15, 2011, 08:16:16 PM »

I thought we would get a post or two from Michael Wootten on this thread since he has posted that adding big bars generates more grip.
He seems like a pretty smart guy so my hunch is he was arguing some of the same points in the other thread but the theory was coming out as a disagreement.  We don't have a 'popcorn' emoticon so I'll just need to keep checking back Wink
-h
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bandg
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« Reply #19 on: March 15, 2011, 10:57:50 PM »

I'm far from an expert here but I had several late 70's trans ams in my youth and the pinnacle of handling for that generation was the 79 ws6 setup (still have that 4 speed car but it needs full restoration now) which had relatively huge sway bars and relatively soft springs.  Big heavy cars but for all that weight they really did handle incredibly well.  Might be completely different for the lighter IRS miata.
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VagaXt
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« Reply #20 on: March 15, 2011, 11:05:01 PM »

In regards to the OP by 95MSM, I completely agree for the process of reducing roll by first springs, then anti-roll (sway) bars.  My MSM and NA's suspensions are tuned to this very concept (both have MSM stock size anti-roll bars).

Can I get an AMEN?

AAAAAAMEN!  Haha.

But yeah, the roll stiffness by way of swaybars is in my head an autox tuning trick to get though offset gates and slaloms with quick steering while being stable at limit when changing directions quickly (usually biased toward understeer but best for stability), a result of getting to the limit of your car's roll quicker (when the tire grip and lateral acceleration is at its highest).  

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scotty b
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« Reply #21 on: March 15, 2011, 11:47:01 PM »

I'm far from an expert here but I had several late 70's trans ams in my youth and the pinnacle of handling for that generation was the 79 ws6 setup (still have that 4 speed car but it needs full restoration now) which had relatively huge sway bars and relatively soft springs.  Big heavy cars but for all that weight they really did handle incredibly well.  Might be completely different for the lighter IRS miata.

T/As still didn't corner anywhere near flat, though, and with that long hood with the engine set well back the weight distribution probably wasn't too terrible.  They had beefy rubber at all corners, and the springs were considered stiff for that time.  Also, they are much wider than a Miata, and a longer bar will twist more with the same force, and the bars may have been more flexible then (but that bit is speculation on my part).  Or maybe that old T/A just grips the road like Burt Reynolds' moustache gripped his face.
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« Reply #22 on: March 15, 2011, 11:56:01 PM »


But yeah, the roll stiffness by way of swaybars is in my head an autox tuning trick to get though offset gates and slaloms with quick steering while being stable at limit when changing directions quickly (usually biased toward understeer but best for stability), a result of getting to the limit of your car's roll quicker (when the tire grip and lateral acceleration is at its highest).  

Agreed!  I'm running relatively high spring rates (560/336) with a RB tubular 1.25" front bar and stock rear.  The ride height is similar to Sonny's (11.5") and the camber is -2.5 F & R.  The car is incredibly stable, amazingly flat, and easily flickable (goes where you point it).  I'd say the handling is closer to neutral with oversteer on demand via throttle input.  On an aside, it doesn't work well with a street tire that has moderate grip (Falken RT-615) on the (narrow and tall) Racing Harts (they can't cope) but with a 15X9 and an R comp (Nitto NT-01 or Hoosier A6) the car is phenomenal! 
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VagaXt
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« Reply #23 on: March 16, 2011, 06:07:10 AM »


But yeah, the roll stiffness by way of swaybars is in my head an autox tuning trick to get though offset gates and slaloms with quick steering while being stable at limit when changing directions quickly (usually biased toward understeer but best for stability), a result of getting to the limit of your car's roll quicker (when the tire grip and lateral acceleration is at its highest).  

Agreed!  I'm running relatively high spring rates (560/336) with a RB tubular 1.25" front bar and stock rear.  The ride height is similar to Sonny's (11.5") and the camber is -2.5 F & R.  The car is incredibly stable, amazingly flat, and easily flickable (goes where you point it).  I'd say the handling is closer to neutral with oversteer on demand via throttle input.  On an aside, it doesn't work well with a street tire that has moderate grip (Falken RT-615) on the (narrow and tall) Racing Harts (they can't cope) but with a 15X9 and an R comp (Nitto NT-01 or Hoosier A6) the car is phenomenal! 

I realized I didn't complete my thought, so I'll finish it. Through the bigger bar on the front axle will quicken the time you get max grip and lateral acceleration, the max grip level on that axle will be less than achieving the equivalent roll stiffness with using heavier springs and smaller bar, like 95MSM explained in the OP.  Though I have more roll than say a well set up auto-x car, for race tracks this is preferred as the turns aren't as tight and as in quick succession as an autox course, thus rewarding overall mechanical grip over agility.     
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'95MSM
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« Reply #24 on: March 16, 2011, 06:27:30 AM »

I disagree about bars being particularly well suited to autox.  I would make a sizable wager that the same roll stiffness achieved with more spring and less bar will be a tick quicker due to the net grip calculations detailed in my first post of this thread.  And mechanical roll stiffness is roll stiffness whether most of the stiffness is achieved with springs or bars (I'm missing that MB coupe with its hydraulic suspension that I had for most of the fall).  The bar just pushes on the other spring (through two links and guided by two mounts that typically have at least a little deflection).

I think bars are common in autox because they have no ride penalty and most autox cars are definitely dual purpose that have to deal with potholes and speed bumps.  More than a few also have to pass the spouse test.  I don't think I'm being sexist in my opinion that most women won't tolerate spring rates that most guys would find perfect.  Could have something to do with jiggly body parts. Roll Eyes Roll Eyes

As to the TAs (did I just type TA after mentioning jiggly body parts?), mass produced cars will always lean towards the cushiest ride possible that meets the handling target.  Plus a honkin' big rear sway bar on the rear of a TA wasn't going to convert it any more towards the solid axle than it already was.  
« Last Edit: March 16, 2011, 06:30:32 AM by '95MSM » Logged

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'95MSM
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« Reply #25 on: March 16, 2011, 06:40:56 AM »

On an aside, it doesn't work well with a street tire that has moderate grip (Falken RT-615) on the (narrow and tall) Racing Harts (they can't cope) but with a 15X9 and an R comp (Nitto NT-01 or Hoosier A6) the car is phenomenal! 

Bolting on a set of tires with a different level of grip will often hose the setup.  Most of the time the problem surfaces when putting a softer compound on.  The car will generate roll angles that it just wouldn't get to with harder tires.  Your situation could very easily be the reverse: you've dialed in your setup to present the tire to the track at the correct attitude when cornering at X g.  When you bolt on tires that can only generate .8X, the tire to pavement angle probably isn't optimum.
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'05 running gear + '95 body
3.63 ring & pinion FM content: Blouch compressor mod, FM-Link, i/c & no-MAF intake.   BEGi: Stainless SGDP w/ metal core performance cat.   Custom stuff: Compressor clocked downward w/ new i/c pipe, big radius throttle elbow, 2.5" mid-pipe w/ Hushpower II, dual 2" axle-back w/ open Supertrapps, Toyota 4 pc cop ignition

245.2 whp on default FM-Link maps (with OEM midpipe)
'95MSM
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« Reply #26 on: March 16, 2011, 06:46:30 AM »

Sonny was getting into the differences between track setup and autox.  I agree 100% that the quick transitions in autox reward roll stiffness that would be too knife edged on the race track.  I just think it is still best done with as much spring as possible.  The realities of Monday through Friday driving, however, reduces the amount of spring that is acceptable for most people.
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'05 running gear + '95 body
3.63 ring & pinion FM content: Blouch compressor mod, FM-Link, i/c & no-MAF intake.   BEGi: Stainless SGDP w/ metal core performance cat.   Custom stuff: Compressor clocked downward w/ new i/c pipe, big radius throttle elbow, 2.5" mid-pipe w/ Hushpower II, dual 2" axle-back w/ open Supertrapps, Toyota 4 pc cop ignition

245.2 whp on default FM-Link maps (with OEM midpipe)
mr_hyde
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« Reply #27 on: March 16, 2011, 07:34:04 AM »

Plus we haven't discussed the differences in alignment optimized for a 100mph sweeper on a track vs. a 35mph slalom at an autocross vs. something more neutral to get maximum life out of street tires M-F. buck2
-h
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2005 Black Mica #290 8/27/04 w/Factory Hard Top
BEGi Intake, FM Downpipe.  Nice and calm with an edge...

1990 Red - MSM Drivetrain, Adaptronic EMS, Xida 700/400, 15x9 6uls, Full Cage, SGDP w/80mm Corksport exhaust, ~260whp @ 15psi on Forged Rods.  bow2
Build Thread: http://www.mazda-speed.com/forum2/index.php/topic,24668.0.html

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2003 E350 7.3 Powerstroke Ambulance for towing '90MSM to play dates.

1991 BRG - Daughter's daily driver.
VagaXt
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« Reply #28 on: March 16, 2011, 08:42:12 AM »


Bolting on a set of tires with a different level of grip will often hose the setup.  Most of the time the problem surfaces when putting a softer compound on.  The car will generate roll angles that it just wouldn't get to with harder tires.  Your situation could very easily be the reverse: you've dialed in your setup to present the tire to the track at the correct attitude when cornering at X g.  When you bolt on tires that can only generate .8X, the tire to pavement angle probably isn't optimum.

This is a problem I couldn't solve for a couple of years ago.  Different wheel/tire combo will definitely yield different results, but the optimization is down to simply picking alignment settings that are best your needs.  Before the NA wore the 15x9 6UL with 225/45/15 NT01s for the first time, the alignment wasn't optimized for that, but rather for optimal tread wear and life between street and track for the old less grippy, tall flexible sidewall of the 195/60/14 Azenis RT615 of the time.  The result was that the NT01 only used the outside 2/3 width of the tire!  It was noticed because visually it was obvious as the rubber was chunking in a line on the last 1/4 width of the inside of each front tire all around the circumference!

Later I optimized the alignment for the NT01 for a later track day on the same set of tires to see if it fixed the funky wear problems, and it did, as well as provide better overall mechanical grip and faster lap times.
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I've started my journey toward wheel-to-wheel racing. Follow my driving adventures on my BLOG.

Also, see it action on YouTube.

I'm getting lonely being the only MSM in competition. Join me in Miata Challenge!!

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gtred
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« Reply #29 on: March 16, 2011, 05:06:52 PM »

my simplistic understanding of this is:

while stiffer sway bars will certainly diminish the combined grip of the wheel/axel set that it is attached to**, the sway bar does positively impact the drivers "feel" or "confidence" by keeping the platform stable.   for me, the driver confidence imparted by this "seat of the pants" feel is the most important contribution from a stiff set of sway bars.
 

** in a turn, the sway bar acts as a lever to unload the inside tire and will move the grip of this tire away from it's optimum, while the sway bar will over-load the outside tire, also moving it away from it's optimum grip level; lowering the combined traction available at that wheel/axle set.
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