flatlander937's Mazda2 build - SCCA STF / NASA NXF

flatlander937

Member
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'11 Mazda2 Sport
Since things are starting to move along pretty quickly I figured I'd start a build thread.

I previously had a 2009 Mazda3i which I had started auto-xing with and was just starting to build for STF... but then decided I wanted something more Mini-like... without the unreliability of one. I drove a Mazda2 at work and it was just stupid fun to drive so that was it.

Got the 2011 Mazda2 almost exactly one year ago(in March of 2014).

I autocrossed it a couple times while bone stock on some crappy Yokohama tires on one end, and some even crappier Kumhos on the other, 320 and 420 treadwear. It would still lift a wheel on hard turns though...

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I added a DDM Works rear sway bar at some point, it helps a TON with body roll and more importantly balance at turn-in.


The engine flopping around always bothered me and I have the basic fab skills to make my own rear motor mount.. so I did:
http://www.mazdas247.com/forum/showthread.php?123843131-Built-a-rear-motor-mount

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I still wanted more rotation... so installing a set of camber bolts up front and aligning it at home was the next cheap step to get me by since winter was coming and I had some bigger plans ahead. Here's a thread that documented the camber bolts/alignment being done: http://www.mazdas247.com/forum/show...ber-bolt-install-tip-string-alignment-at-home


One last small gripe with the car that I had was that I can't heel-toe downshift it properly. I have to brake with the left side of the right foot, and tilt my foot sideways to blip the gas pedal... which in stock form is too far away. So I made a throttle extension so I can rev match more consistently. Details here:
http://www.mazdas247.com/forum/show...-these-cars!&p=6348057&viewfull=1#post6348057

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......
 
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The only mod after the above was basically winter tires on my stock steelies(Continental ExtremeWinterContact... highly recommend them).


But what that brings me to is wanting to go all out on the suspension and keep it somewhat reasonable budget-wise and end up with something that performs great...

So I chose to start acquiring stuff to build some front coilover strut housings that accept Koni 8610-1436RACE inserts. I opted to not get the double adjustable 8611s because 1) cost and 2) more stuff to mess with means more stuff to mess up. 3) the compression adjustment is on the base of the strut housing, so right above the outer CV joint. Pain in the ass to adjust. 8610s should be better than just about any China coilover available and actually handle the 500-600lb spring rates needed.
http://www.koniracing.com/8611.cfm

So I bought these back in like October or something and have been sitting on them ever since... got them for a good price at $164/ea. They are $230-240/ea as of right now on Google shopping.(notcool)

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To make them work, they need a housing. Some people cut of stock housings to modify and put inside. Our struts are simple enough I said screw it and just bought a bare "builders housing" from TM Family Racing with the one end capped/tapered to center the strut, and the other with a modified MR2 gland nut to hold the cartridge in place. Here it is test fitting a strut, no ears or anything on it yet... that is to come soon enough...

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I haven't made any progress on that front yet since I need to be able to bolt the top into the car... so I'm building my own spherical bearing top hats which is what I started on tonight...

I started with some 1/4in steel... Frankly I feel I should have used 3/16in now but whatever it's what I've got and 0.2lbs isn't going to help me out at this point. I can always make more. I used a large 4.5in hole saw... which when the kerf is taken into consideration leaves you with a 4-1/4" circle when cut out.

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Next step was to take a smaller hole saw through the same pilot hole to cut out the inside... this is to make room for my spherical bearing holder which I purchased from Pegasus Auto Racing.

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And once somewhat cleaned up this is what I'm left with. The bearing holder will be welded to the center, after I scribe and mark the 3 bolt holes so it can bolt into the strut tower first... then determine how high/low the bearing holder needs welded in relation to the mounting plate. You want it as high as possible for more usable strut travel.

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I'm just building a solid non-adjustable camber plate because our strut tower holes are just too damn small to be useful. I will be able to modify the ears of the knuckle mounting tabs quite a bit to get as much camber as I'll ever need. The bonus to adjusting camber at the knuckle instead of at the top mount is that it leaves your steering axis inclination unchanged... which is generally good. It won't screw with scrub radius which is important since 7.5in wheel width isn't crazy. Wider wheels/tires might benefit from the SAI being moved outward some to keep it intersecting near the middle of the contact patch. The result is lighter steering feel and less momentum scrubbed off when turning.
 
I was fortunate enough to get a preview of the progress so far in FB...Nice job fabbing these up. My only concern is still welding the tabs on the housings themselves, but seeing your other projects, can't wait to see how these turn out.
 
Really cool, I look forward to seeing more progress with the suspension.
 
Thanks guys!

I have a bunch of goodies on the way:

-Eibach 550lb 2.5x6in springs(just got one pair for now... will test fit both front and rear to see what I decide on for the opposite end... either 500 or 600 most likely) coming from Summit

-Torrington bearings and races to prevent spring bind and keep annoying "pinging" noises from occuring when turning left and right(already arrived, came from one of the closer-by Summit warehouses)

-Some used coilover sleeves and lower perches courtesy of Jeff(jasyatz)

-Upper spring perches designed for Koni struts coming from Turner Motorsports(http://www.turnermotorsport.com/p-3725-upper-spring-hatperches-pair-25-inch.aspx). I could have probably saved $20 and bought some Cusco brand perches that I found on google shopping, but dimensions are not 100% clear and I'd rather know I'm getting what I need than screw around getting the right part twice.



Hoping to make it back out to my friend's garage to work on finishing the strut hats too. Once the upper perches arrive I should be able to determine if any more misalignment spacers are needed for adequate clearance(or not) so I can get that ordered too.

Once ALL that crap is done, I'll be able to pull my stock strut assembly off and mock the Koni housing in place so I can shape the knuckle ears correctly to design in the camber I need. I think I'll target 2.5 to 3.0 or so. I'm not looking to go full retard as it is still daily driven.




Oh yeah, also ordered some 205 ZII Star Specs mounted on 7.5in TRM C1 wheels through work today, should be here next week!(nana)
 
Awesome, awesome stuff. I bow to your workmanship and fab skills.


Thanks!




For anyone who doesn't know already, updates happen a bit quicker on the Mazda 2 Owner's Facebook group page since it's a heck of a lot quicker to upload pics straight from my phone as opposed to transferring to imgur first then posting here when I get a chance from a laptop. Link here: https://www.facebook.com/groups/431895740279303/



Anyways... not even 24hrs after ordering my wheels/tires at work, they showed up for me to pick up! Tirerack is awesome!

They fit perfect in the back of my wife's Equinox..

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Compared next to my 185/55R15 Continental winter tires:

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I have not mounted them yet as today should be the last day below freezing(hopefully until the end of the year!) and don't want to damage them by driving on them below 32F so they're laying in my garage until tomorrow when we get above 50. Very antsy to get them on (nana)

...
 
...Also, all my goodies arrived last Wednesday!


550lb Eibach springs from Summit:

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Upper spring perches from Turner Motorsport:

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Some used coilover sleeves from Jeff/Jasyatz:

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And the 2.5in ID torrington bearings from Summit as well to prevent spring bind:

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Also I'm a dork who likes keeping track of everything... so here's a spreadsheet of what has been spent on materials/etc and where things were purchased. Prices do not include tax or shipping... for large orders it's harder to keep track of that stuff.

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As you can see this is not a budget solution. If I were to buy my own coilovers they would probably be Fortune Auto with BC being a close second for competitive autocrossing... or a Corksport spring/shock combo for a more daily driver than SRSBZNS. I came really close to buying CS stuff but I knew I'd be wanting more right away and decided to use that money to take the plunge into the Koni struts and housings.

And as stated earlier... I like building stuff. :) There will probably be another $400-500 all said and done into the rear shocks and more springs.
 
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Please stop posting your costs sheet; makes me think of mine...I don't like thinking about those things...Although this car is the most cost effective project of the 17 autox cars I've built.
 
Aluminum shifter bushings? I must have got the other version hahaha. Great work though

Pretty sure they're anodized aluminum? Maybe ask Zach of DDM Works about it, I did install them over a year ago...

Please stop posting your costs sheet; makes me think of mine...I don't like thinking about those things...Although this car is the most cost effective project of the 17 autox cars I've built.

I'll use the same excuse my wife does to justify purchases..

"It was on sale" (headshake
 
So it was a fun day today!

Loosely test fitted my coilover goodies together... waiting on a 1.1875" round bar to arrive so I can press it into my spherical bearing holders during welding(to prevent warpage).

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Also here is the bare insert... just realized this hasn't been posted yet. This is what you get from Koni(along with a small bag with a centering ring, and adjuster knob, a 14mm to 5/8" adapter, and the top nuts).

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I got around to running some suspension numbers on the rear to figure out what springs I'll need and more importantly to measure how long of a shock I need to have in order to keep the springs from falling out. The answer is roughly 21" long... I will be making my own upper shock mount to take normal 1/2" heim equipped circle track style shocks. 7" travel variety most likely.

Here is about where I want the ride height/fender gap to end up, maybe just slightly taller than this though:

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And here it is with the ZII* mounted to the car... needs lowered badly.

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Also been running as many suspension calcs as I can to try and get everything in the ballpark the first time around(and especially so I can order some rear shocks that don't suck and don't cost $250+ per corner)... here are some things that may be of use:

Front motion ratio, I'm estimating in the 0.98 area... typically of a strut equipped car.

Rear motion ratio of the SPRING is about .97, it's about 14.5in from the beam pivot to the center of the lower spring seat, and about 15.0in from beam pivot to the "axle" centerline.

Rear motion ratio of the SHOCK is about 1.23, it's roughly 18.5in from the beam pivot to the shock mounting hole.

What this means is when looking for a shock, you need to treat a 550lb spring at the perch the same as a 434lb spring on the shock center line(like the Fiesta B-spec kit for instance). You can multiple your spring rate by .789 to figure out the equivalent rate at the shock with the 1.23 motion ratio.


The rear spring seat looks about perfect to fit a 2.25" spring, the upper seat may just need a very slight trim(there's a rubber flap that would normally index against the end of the stock coil) to be used with a 2.25" spring. I may just order an 8" 450-500lb spring for the rear as a temporary measure. If I can source a spring seat height adjuster then 6in springs are perfect.


I also attempted to crudely calculate the tire spring rates(at 34psi)... By measuring the tire overall height both loaded and unloaded while roughly estimating the weight on the tire(using data from Andy Hollis and Edmunds). By knowing how much it compresses under X amount of weight and how far it compressed is how you figure this out.

The left front compressed by .5625" under (an estimated) 720lbs, the left rear compressed by .375" under (an estimated) 402lbs.

This is all a pretty big guess of course, but I wanted a somewhat realistic number to enter into the dynamics calculator here: http://farnorthracing.com/autocross_secrets16.html


I got 1280lbs/in for the front and 1072lbs/in for the rear. This is because tire spring rates increase as they are loaded.

Some time this week I am going to attempt to use a bathroom scale to figure out the unsprung weights while unbolting the struts/sway bars and measuring how much weight is on the scales.
 
The shifter bushings are anodized aluminum.

Also if you want cheap height adjustment just get a set off ebay. You can get a set of 4 adjusters with springs for $40-$50. That's what I did. Even if you don't use the springs it is still worth it for the adjusters. The springs with mine were 7" 525lbs. I didn't use them.

You can also get a set from Bilstein for their race shocks for about $40 a piece if I remember correctly. Just make sure you get the one for the 46mm shocks not the 36mm.

Also what is the height of the shock body when they are in the housings for the front? Just wondering to compare to mine.

Zach
 
The shifter bushings are anodized aluminum.

Also if you want cheap height adjustment just get a set off ebay. You can get a set of 4 adjusters with springs for $40-$50. That's what I did. Even if you don't use the springs it is still worth it for the adjusters. The springs with mine were 7" 525lbs. I didn't use them.

You can also get a set from Bilstein for their race shocks for about $40 a piece if I remember correctly. Just make sure you get the one for the 46mm shocks not the 36mm.

Also what is the height of the shock body when they are in the housings for the front? Just wondering to compare to mine.

Zach

That's basically what I have from Jeff(eBay GC knockoffs). I'm going to build a more stable base for rear spring adjustment so its basically impossible to lose a spring.


I'll measure the housings tonight. They're short compared to stock, I almost wonder if I should have used an 8610-1437 housing. It will mostly be up travel for ride reasons, having the spring loose under droop does nothing for traction, so 2" of down travel should be plenty(and spring still loose).

Finer height correctionss can be made by adding a tender coil(another 1/2" to 3/4" height when solid) if the springs alone net me silly low/unusable.

I can always build another housing for the 8611 double adjustable next year :)
 
Don't bother with an 8" spring, it's too long...7" is about right if you don't run adjusters, 6" if you want to run the adjusters with a 21" shock.
 
Zach here's a pic of Koni housing vs stock for a rough idea, I'll probably be welding an extension to the bottom if needed.


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And not a big deal but got some maintenance stuff to do later this week/weekend.

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I have some 400 and 450lb springs coming, and am in talks with Maxcy Speed and Performance for custom valved Bilsteins in the rear.
 
Do the 450 in the rear first. I am really happy with the spring balance on mine and I have 400 in the rear with 450 front.
 

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