Official Suspension Bars and Braces Thread

[phate]

Originally Posted by MSP611 No one makes an aftermarket tie rod endlink for toe adjustment for the speed6?

Toe is independently adjustable with stock components in both the front and rear of the MS6. No need for anything aftermarket.

[phate]

Originally Posted by Inquisitive I mean I am still trying to wrap my head around Puhn and Staniforth’s formulae.

Not mine, but it's a good derivation. It assumes you already know some things about bending and torsion, though.


Sway bar formula derivation

^That should prompt you to download a pdf. If it doesn't work, I can just upload a copy to this post.

Originally Posted by Inquisitive Would some sort of caveat or warning suffice, such as, “Warning, the following links are the opinion of Ultra Racing’s and not necessarily those shared by this MSF”?

I just wouldn't call them a technical resource, is all.

[Inquisitive]

Originally Posted by phate That should prompt you to download a pdf.

I removed the quotes and it worked. Thanks – I have some reading to do.

Originally Posted by phate I just wouldn't call them a technical resource, is all.

OP updated

[Inquisitive]

Originally Posted by maisonvi I did the math on my bar vs the stock bar to calculate spring stiffness and made it according to what I wanted.

OK, now armed with Fred Kuhn’s effective spring rate in sway bars equation thanks to @phate; would you mind running us through the numbers: original and yours?

You bring up an interesting point about 4140. The equation assumes generic steel is generic steel (elastic and shear modulus).

Kswaybar_Puhn ≡ 5000000 x D to the fourth power / 0.4244 x A squared x B + 0.2264 x C cubed

Where D is the diameter and A, B and C are lengths as shown below

[breakfstincluded]

my pic folder of looking at brace options mostly autoexe and it's ebay clone speedline

[maisonvi]

Originally Posted by Inquisitive OK, now armed with Fred Kuhn’s effective spring rate in sway bars equation thanks to @phate; would you mind running us through the numbers: original and yours? You bring up an interesting point about 4140. The equation assumes generic steel is generic steel (elastic and shear modulus). Kswaybar_Puhn ≡ 5000000 x D to the fourth power / 0.4244 x A squared x B + 0.2264 x C cubed Where D is the diameter and A, B and C are lengths as shown below

Yeah I used 4130 but really the calculations for both end up the same. I honestly dont remember why, I did this a long time ago at this point. I can look it all up if you want, I know I did a bit of research between various different materials. I chose 4130 for its strength and really impact resistance. It handles load very well and I have made swaybars (and tube chassis) out of it back in college. The cost difference wasnt much at all so I ended up just using it and it has worked out great.

Edit, I found one of my calculations spreadsheets. Ive attached it for people to look at.

[MSP611]

Originally Posted by breakfstincluded my pic folder of looking at brace options mostly autoexe and it's ebay clone speedline

These for speed6???

[breakfstincluded]

Originally Posted by MSP611 These for speed6???

lol easy way to check... look to see if there's a drive shaft in the pic.

[EvoFire]

Looks like a speed3 to me

[MSP611]

o ya ur right guess I was just bein lazy, why does no one make any of these for speed6

[Inquisitive]

For understanding, I have tried to work through the calculations for:
Kswaybar_Puhn ≡ 5000000 x D to the fourth power / 0.4244 x A squared x B + 0.2264 x C cubed

Stock Bar
Kswaybar_Puhn ≡ 5000000 x1x1x1x1/ 0.4244x7.375x7.375x25+ 0.2264x 7.488575 x 7.488575 x 7.488575
Or in Excel
Kswaybar_Puhn= =5000000*1*1*1*1/((0.4244*7.375*7.375*25)+(0.2264*7.488575*7.488575 *7.488575))
= 7438.7 lbf / in

@maisonvi; ‘s
Kswaybar_Puhn=
=5000000*1.25*1.25*1.25*1.25/((0.4244*7.375*7.375*25)+(0.2264*7.488575*7.488575 *7.488575))
= 18161 lbf / in

Or 244.1% vs your 112.5%, but I note that you have calculated Tonison, bending and total spring rates

@phate; What am I doing wrong or is it just that Kswaybar_Puhn’s formula is so different from Tonison, bending and total spring rates?

For Kswaybar_Puhn, being in the numerator, I see that diameter makes a significantly higher contribution than trying to reduce some of the distances in the denominator.

So, @maisonvi; you used the exact same bends (allowing for diameter differences), but just used a thicker (1.25 vs 1 inch) 4130 bar?

[phate]

Originally Posted by Inquisitive For understanding, I have tried to work through the calculations for: Kswaybar_Puhn ≡ 5000000 x D to the fourth power / 0.4244 x A squared x B + 0.2264 x C cubed Stock Bar Kswaybar_Puhn ≡ 5000000 x1x1x1x1/ 0.4244x7.375x7.375x25+ 0.2264x 7.488575 x 7.488575 x 7.488575 Or in Excel Kswaybar_Puhn= =5000000*1*1*1*1/((0.4244*7.375*7.375*25)+(0.2264*7.488575*7.488575 *7.488575)) = 7438.7 lbf / in maisonvi‘s Kswaybar_Puhn= =5000000*1.25*1.25*1.25*1.25/((0.4244*7.375*7.375*25)+(0.2264*7.488575*7.488575 *7.488575)) = 18161 lbf / in Or 244.1% vs your 112.5%, but I note that you have calculated Tonison, bending and total spring rates phate What am I doing wrong or is it just that Kswaybar_Puhn’s formula is so different from Tonison, bending and total spring rates?

I get bench rates as:

1.00" OD (solid): 743lb/in

1.25" OD (solid): 1816lb/in

2.44 times as stiff. I think you're off by a factor of 10 somewhere in your calcs, but the ratio is correct.




BUT, @maisonvi; is using a hollow bar, with inner diameter of .75" according to his spreadsheet, above. I get a bench rate of:

1,580lb/in, which is 2.12 times as stiff as.

I haven't looked at his calculations closely, so I'm not sure where we are different.

[maisonvi]

Originally Posted by Inquisitive For understanding, I have tried to work through the calculations for: Kswaybar_Puhn ≡ 5000000 x D to the fourth power / 0.4244 x A squared x B + 0.2264 x C cubed Stock Bar Kswaybar_Puhn ≡ 5000000 x1x1x1x1/ 0.4244x7.375x7.375x25+ 0.2264x 7.488575 x 7.488575 x 7.488575 Or in Excel Kswaybar_Puhn= =5000000*1*1*1*1/((0.4244*7.375*7.375*25)+(0.2264*7.488575*7.488575 *7.488575)) = 7438.7 lbf / in @maisonvi; ‘s Kswaybar_Puhn= =5000000*1.25*1.25*1.25*1.25/((0.4244*7.375*7.375*25)+(0.2264*7.488575*7.488575 *7.488575)) = 18161 lbf / in Or 244.1% vs your 112.5%, but I note that you have calculated Tonison, bending and total spring rates @phate; What am I doing wrong or is it just that Kswaybar_Puhn’s formula is so different from Tonison, bending and total spring rates? For Kswaybar_Puhn, being in the numerator, I see that diameter makes a significantly higher contribution than trying to reduce some of the distances in the denominator. So, @maisonvi; you used the exact same bends (allowing for diameter differences), but just used a thicker (1.25 vs 1 inch) 4130 bar?

Originally Posted by phate I get bench rates as: 1.00" OD (solid): 743lb/in 1.25" OD (solid): 1816lb/in 2.44 times as stiff. I think you're off by a factor of 10 somewhere in your calcs, but the ratio is correct. BUT, @maisonvi; is using a hollow bar, with inner diameter of .75" according to his spreadsheet, above. I get a bench rate of: 1,580lb/in, which is 2.12 times as stiff as. I haven't looked at his calculations closely, so I'm not sure where we are different.

Im not going to lie, I havent really looked at that sheet in a long while. I would have to dig back into it to remember. Honestly at this point, I would trust Phate's data more than my own. I was just using it as a point of reference.

He is right though, I used a 1.25" bar with a .1875" wall thickness. The arm length is measured as the crow flies if I remember right, so the bend in the arm is not taken into consideration. That might be part of the discrepancy.

[Inquisitive]

@phate; Goodness, solid vs hollow – I missed that. You would have a better feel for the numbers, such as Michael J. Iacchei’s quoting an Elastic and Shear Modulus of steel being for solid, rather than hollow. So, I need to substitute OD to the fourth power – ID to the fourth power for D to the fourth power.

Instead of using maisonvi’s measured ID of 0.75 (and like you I got to your 1580), using rather his latest 1.25 (OD) - 0.1875 - 0.1875 (thickness x 2 for both sides of a hollow tube) = 0.875

= (1.25*1.25*1.25*1.25)-(.875*.875*.875*.875)
= 1.855224609

=500000*1.855224609/((0.4244*7.375*7.375*25)+(0.2264*7.488575*7.488575 *7.488575))
=1380 lb / in

or 1.855 times (1380 / 743.87) stiffer (not 2.44 times) for @maisonvi; ’s new sway-bar.

For the factor of ten discrepancy, I see that all the coefficients (60, 32 and 7.0685775e7) were divided by 141.37154 to get 0.4244, .2264, but 5e6 should have been 5e5 (1e7/100 yields 1e5). Mystery solved. Not sure if you want to get back to the good professor on this, but the equation should be:

Kswaybar_Puhn = 500000 x D to the fourth power / 0.4244 x A squared x B + 0.2264 x C cubed

And the ratios would have remained the same as both were out by the same factor.

What fun. What’s next?

[maisonvi]

Originally Posted by Inquisitive @phate; Goodness, solid vs hollow – I missed that. You would have a better feel for the numbers, such as Michael J. Iacchei’s quoting an Elastic and Shear Modulus of steel being for solid, rather than hollow. So, I need to substitute OD to the fourth power – ID to the fourth power for D to the fourth power. Instead of using maisonvi’s measured ID of 0.75 (and like you I got to your 1580), using rather his latest 1.25 (OD) - 0.1875 - 0.1875 (thickness x 2 for both sides of a hollow tube) = 0.875 = (1.25*1.25*1.25*1.25)-(.875*.875*.875*.875) = 1.855224609 =500000*1.855224609/((0.4244*7.375*7.375*25)+(0.2264*7.488575*7.488575 *7.488575)) =1380 lb / in or 1.855 times (1380 / 743.87) stiffer (not 2.44 times) for @maisonvi; ’s new sway-bar. For the factor of ten discrepancy, I see that all the coefficients (60, 32 and 7.0685775e7) were divided by 141.37154 to get 0.4244, .2264, but 5e6 should have been 5e5 (1e7/100 yields 1e5). Mystery solved. Not sure if you want to get back to the good professor on this, but the equation should be: Kswaybar_Puhn = 500000 x D to the fourth power / 0.4244 x A squared x B + 0.2264 x C cubed And the ratios would have remained the same as both were out by the same factor. What fun. What’s next?

So you got me wondering which I had. .75" ID or .875" ID. I still have the piece that is left at my desk, turns out my calculations sheet and not my memory was right.

[Inquisitive]

Originally Posted by maisonvi I did the math on my bar vs the stock bar to calculate spring stiffness and made it according to what I wanted.

lol – I think I’d be fairly content with 2.12 times stiffer than stock. That’s much higher than what the vendors offer. Ever thought of selling any?

Did you do cold bends, apply some heat or just weld end bars to get the requisite shape?

[maisonvi]

Originally Posted by Inquisitive lol – I think I’d be fairly content with 2.12 times stiffer than stock. That’s much higher than what the vendors offer. Ever thought of selling any? Did you do cold bends, apply some heat or just weld end bars to get the requisite shape?

Ive had a few people ask for them, but I wont make them. I will give out the CAD if people want it to make their own, but Im not a business, so I dont have insurance if something goes south and someone gets hurt or dies and I end up getting sued.

I only make parts for people that if they break, you can still get home. I will leave the big stuff to the real vendors.

[KevinK2]

Originally Posted by phate I get bench rates as: 1.00" OD (solid): 743lb/in 1.25" OD (solid): 1816lb/in 2.44 times as stiff. I think you're off by a factor of 10 somewhere in your calcs, but the ratio is correct.

As this page has been revived for strut braces, time to clarify some old sway bar calc'n issues.

Reading this page now, there is confusion about what the proper sway-bar rate calculation is, because of an error in the first equation posted by Phate in post 82. That is an excellent derivation of Fred Puhn's equation by M. Iacchei that I have seen before, but never noticed the error in the numerator; it should be 500,000, and not 5,000,000.

Inquisitive had a great explanation of this error in post 94.

This is the correct formula, reprinted from Puhn's book:
http://v8sho.com/SHO/images/Image48.gif

This is an online calculator that works well:
http://www.gtsparkplugs.com/Sway-Bar-Calculator.html

Maisonvi has a link to his spread sheet in post 86. The equations are correct, but the current modulus values he used are low by a factor of 10, reducing rates by the same factor ... too soft.

The Puhn formula is an estimate of the bench rate, and the A,B, and C dimensions are the centerline values with "ball joint" type supports at the intersections shown on Puhn's image. The typical bushings can drop calculated stiffness by 30%!

When Phate mentions bench rate, that is what the Puhn equation represents, a bench test like he did. I derived the formula to be sure it made sense. It considers:

1) the twist in the bar
2) the lever arms "rigid" deflection due to this twist
3) the bending in the lever arms, as cantilevered beams

The Puhn "bench rate" equation represents the wheel on one side moving up or down, while the wheel on the other side does not move. When considering wheel rates while cornering, you must multiply the Puhn spring rate by 2 .

"How to make your car Handle" by Fred Puhn --- excellent for the basics

.

[mituc]

I purchased this trunk brace from theSpeedLine and installed it today. I had to trim that plastic piece that comes on top of that area but other than that the install was relatively simple.






...And these pieced had to be cut off from the trunk board:



I didn't drive the car yet but I guess anything that can be added in the trunk area will increase the rigidity of an otherwise very soft hatch.

[EvoFire]

Originally Posted by mituc I purchased this trunk brace from theSpeedLine and installed it today. I had to trim that plastic piece that comes on top of that area but other than that the install was relatively simple. ...And these pieced had to be cut off from the trunk board: I didn't drive the car yet but I guess anything that can be added in the trunk area will increase the rigidity of an otherwise very soft hatch.

Report back! My hatch is getting old and flexy.

[mituc]

Originally Posted by EvoFire Report back! My hatch is getting old and flexy.

Ok, I just did a 250 miles trip and despite the fact the road was mostly greasy and wet, I can definitely tell there's a difference. In these conditions the difference in handling was not big but noticeable. It's also hard to be a placebo effect because I drive the car every day, and today in all the trip madness when tat bar was the last thing I had in my mind, I woke up at some point "oh wait, the car didn't do this before, not like that and not as good!".

Probably I need a road where I can get more lateral Gs to tell more, but the fact that the rear was flexing less (as less as it did even before in similar conditions) made the care want to turn more eagerly. And all that is on a relatively soft suspension, the Eibach Pro kit and Bilstein B8 springs (Bilstein B12 kit).

So yes, there's hope, I can still keep the suspension mildly soft (stiffer than OEM though) and by reinforcing the chassis plus the alignment bits can still make a pretty good handling machine from this chassis.
To give you a point of reference, for those who drove rally cars or at least went to the rally school, my car with the suspension/chassis setup I have in my signature feels on the road like a rally car set up for hard/dry gravel which is quite fine for a street driven fast family car.
I can't wait to install the Tanabe 4 point brace (will replace the CorkSport front arms tie brace) and the SpeedLine rear lower strut tower bar.

[KevinK2]

I installed a similar brace on a 93 FD Rx7 that I ran 1000's of miles at HPDE days. The brace was mounted on the top of the front strut towers, to prevent the tower tops from moving toward or away from each other Tower Brace Animation during hard cornering. I first attached it loosely at one end, with "tell-tale" grease smeared around edges of the barcket and/or bolt head, to see if there was relative motion there, for the brace to eliminate. Just a way to quantify the effectiveness of the brace.



.

[EvoFire]

@mituc;

It looks like you got this one 02+ Mazda3 2X Rear Cross Floor Bar - THESPEEDLINE

Any reason why you didn't get this one instead? 02+ Mazda3/ 06+ MPS3 Rear Cross Floor Bar - THESPEEDLINE

[mituc]

Originally Posted by EvoFire Any reason why you didn't get this one instead?

The install looked too invasive for me for a car that is meant for street use (for hooning on the street and occasional track, but mainly for street). But now after tasting the benefits of having the other bar in place I'm seriously considering getting the other one as well since it's not affecting the cargo space by too much, the top bar sits just an inch or so above the trunk floor.

However, I need to have the occasion to drive the car hard on better surface and see how much the current bar affected the oversteer willingness of the car, as of right now all I could test was the turn in and neutrality on loose surface (and both improved just a bit to make the change noticeable).

However, my car has about 114k miles/183k kms so chassis flex became noticeable for the rear. The front is still planted and the rear flex didn't seem to bother me too much as it's light and floaty when you want to make it so, but I'd rather deal with the setup of the suspension in the back than having to think about the chassis flex as well.

[mituc]

Originally Posted by KevinK2 I installed a similar brace on a 93 FD Rx7 that I ran 1000's of miles at HPDE days. The brace was mounted on the top of the front strut towers, to prevent the tower tops from moving toward or away from each other Tower Brace Animation during hard cornering. I first attached it loosely at one end, with "tell-tale" grease smeared around edges of the barcket and/or bolt head, to see if there was relative motion there, for the brace to eliminate. Just a way to quantify the effectiveness of the brace.

Ok, so I followed your advice and did this: took off all 4 bolts, added some graphite grease (black-ish) on the bolt crown face to the bar, screwed the bolts in but just a bit, so touch the bar lightly but still hold it in place.
Then I went to my favourite car wash where there's a big ramp I have to climb on, and that on a 45 degrees angle. As usual, the hatch start squeaking. I eyeballed the deviation of the bolts and they were like 1.5mm on one side and under 1mm on the other side. When I checked the bar after that it seemed to be in the same position relatively to the bolts/holes that I've initially put it in.
Cleaned up the bolts, screwed them back in, went on that ramp again under the same angle, no more hatch squeaking. iWin!

I have no pictures this time because my damn phone was under 10% charged and it was too dark.

This is the ramp. It may not seem much, but if I come in too hard I will hit it with the bumper. Once the front right wheel is on it, the rear right will lift. it's just a ramp on an angle, but with no real playground for more lateral Gs this will do.

https://www.youtube.com/watch?v=3fr2T6Au4ds

[KevinK2]

Great way to test it, as your equaling or slightly exceeding the roll that the rear normally will see on corners at speed. It is doing it's job. Do you have a rear bar upgrade.


.

[mituc]

Originally Posted by KevinK2 Do you have a rear bar upgrade..

Not yet, not on the car. it's sitting on my balcony waiting to be installed (I hope it will clear my Cobb catback):


Otherwise the sway bar is stock and it will remain so. Same for the front.

[greatdane68]

Originally Posted by mituc Not yet, not on the car. it's sitting on my balcony waiting to be installed (I hope it will clear my Cobb catback): Otherwise the sway bar is stock and it will remain so. Same for the front.

I got lost somewhere. What kind and where can I find that rear lower tie brace that you have on your car?

[greatdane68]

Nevermind. I saw the watermark in your pic. I just ordered one. Thanks.

[mituc]

Originally Posted by greatdane68 Nevermind. I saw the watermark in your pic. I just ordered one. Thanks.

Just beware the one I installed appears in the previous pictures and on their web site it's called "02+ Mazda3 2X Rear Cross Floor Bar" (part# M0168R-BK) and this is the one I evaluated.
The other one you've seen in the picture with watermark is "02+ Mazda3 Rear Middle Lower Strut Bar" (M0187R-02BK) and it's currently sitting somewhere in my house waiting for princess Elsa to meet the love of her life and melt away the ice on her tiny tits and our roads all together.

[MSP611]

Originally Posted by mituc Just beware the one I installed appears in the previous pictures and on their web site it's called "02+ Mazda3 2X Rear Cross Floor Bar" (part# M0168R-BK) and this is the one I evaluated. The other one you've seen in the picture with watermark is "02+ Mazda3 Rear Middle Lower Strut Bar" (M0187R-02BK) and it's currently sitting somewhere in my house waiting for princess Elsa to meet the love of her life and melt away the ice on her tiny tits and our roads all together.

Hahahha...

Sent from my Nexus 7 using Tapatalk

[greatdane68]

Originally Posted by mituc Just beware the one I installed appears in the previous pictures and on their web site it's called "02+ Mazda3 2X Rear Cross Floor Bar" (part# M0168R-BK) and this is the one I evaluated. The other one you've seen in the picture with watermark is "02+ Mazda3 Rear Middle Lower Strut Bar" (M0187R-02BK) and it's currently sitting somewhere in my house waiting for princess Elsa to meet the love of her life and melt away the ice on her tiny tits and our roads all together.

Will do.

[Roman-dude]

I have a Corksport RSB and the Moog links that I installed a year ago are blown out. Do you guys know of any that last longer? Thanks!

[mituc]

Originally Posted by Roman-dude I have a Corksport RSB and the Moog links that I installed a year ago are blown out. Do you guys know of any that last longer? Thanks!

Assuming that it's the Moog endlink which blew as the RSB is just a piece of metal and should last longer as is, I suggest you get some OEM rear end links.

[sharksinspace]

Originally Posted by mituc Not yet, not on the car. it's sitting on my balcony waiting to be installed (I hope it will clear my Cobb catback):

Since this thread was already rez'd; did you ever get this rear/middle lower bar installed and, if so, what sort of difference did it seem to make? I was eyeing it up on Speedline the other week since it's so cheap, but I'm not sure how much that section of the car really needs reinforcing.

[mituc]

Originally Posted by sharksinspace Since this thread was already rez'd; did you ever get this rear/middle lower bar installed and, if so, what sort of difference did it seem to make? I was eyeing it up on Speedline the other week since it's so cheap, but I'm not sure how much that section of the car really needs reinforcing.

Yes I installed it in the meanwhile.
It didn't make as much of a difference as the bar in the trunk but I could feel a slight improvement with it on right away.
In tight corners taken at the grip limit you can feel them the most.

[sharksinspace]

Cool cool. I was looking at buying that same tunk brace along with it (like you, I prefer the less intrusive install and ability to hide it below the trunk floor to retain storage space, in comparison to the dual level "cross brace" they sell). I suppose I'll keep these on my list to eventually grab once the big mods are done; they seem easy enough to install and are certainly cost effective if they result in any noticeable improvement in handling. Wouldn't expect anything world-changing, of course, but every bit of improvement is nice.

[Don]

Reminds me. I got to post a picture of my broken rear swaybar to see if anyone can identify it.. It came on that car when I bought it and now both mounting brackets are broken

[mituc]

Originally Posted by sharksinspace Cool cool. I was looking at buying that same tunk brace along with it (like you, I prefer the less intrusive install and ability to hide it below the trunk floor to retain storage space, in comparison to the dual level "cross brace" they sell). I suppose I'll keep these on my list to eventually grab once the big mods are done; they seem easy enough to install and are certainly cost effective if they result in any noticeable improvement in handling. Wouldn't expect anything world-changing, of course, but every bit of improvement is nice.

Here are some pics from the install:






And this is what I had to cut off from that trunk plastic trim right behind the rear seats:



To install the lower rear brace from your picture you need to get an angled key extender because you're going to have very limited space to torque that bolt on the passenger side (or the right side for RHD cars) because of the tight fuel tank clearance.

...There on the left side on the image is going to be the main source of swearing and cursing during the install:


...Or here on the right side: