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Your knowledge and efforts literally baffle me, I just recently started going to school for my Master Mechanic degree and I now need to re-read through this entire thread to see what all you've done from start to finish. You clearly have more experience and MacGyver in you than most mechanics out there today lol.
 

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Discussion Starter #443
Thanks! My advice to aspiring mechanics (and young engineers, for that matter) is to be Fearless and Persistent - it is the best way to learn. A man far wiser than I once said, "Experience is what you get when you don't get what you want." So yeah, I've got plenty of experience. :)

CR
 

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Discussion Starter #444
I can almost hear ya - "CR, race season is coming, what are ya working on?"

Still working on the rear suspension. Made these plates to box in the radius arms:



This is how they'll be welded in to provide support for the new spherical ends and stiffen the radius arm:



I've also been working on the front . . . :D

CR
 

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Discussion Starter #445 (Edited)
DIY Coilovers

How to convert your Bilsteins to coilovers for under $35ea! (not including springs)

The reasons I bought Bilsteins when my KYBs were shot:
Very high quality
The factory will rebuild and revalve them to just about any spec you want
Easily converted to coilovers

Here they are as I have been running them with Eibach springs.


Here is the spring perch with the spring removed.


Here you can see the perch sits on a snap ring that sits in a groove in the strut body.


The sleeve I'm using has a bump inside to sit on the snap ring. At one end the bump is 1" from the end. At the other end it is 2" from the end. The sleeve is 7" long.


If you slide the sleeve on, it stops pretty much where the factory spring perch was. This is useful if you want to raise the car to monster truck status, but not if you what to lower the car.


BUT . . . if you cut 1" off one end - thereby removing the bump inside the sleeve at that end:


It slides all the way down to the bump inside the other end of the sleeve. Now I can adjust the spring perch up 1.5" from the factory position and 3.5" down. :thumbup:




I think the Track Car will finally be getting MOAR LOWER! :p

CR
 

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Discussion Starter #446
One done with new spring installed:



Total cost to convert two bilsteins - just under $150 for springs, sleeves, adjusting nuts and shipping. :thumbup:

Now I gotta finish the rear suspension. <_<

CR
 

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First post over here (isn't that exciting). I was directed to this thread because I'm doing similar things with my speed6. Your build looks good! Long time in the making with really cool work (I just read the entire thread).

Mine isn't as extreme as yours, as I want to stay (hopefully) within street prepared rules. The WRX's were pulled out of the class and thrown into ASP for 2014, so I just have camaros and mustangs to play with :) I did 16 or 17 events this past season (all autocross) just trying to learn the car and figure out what it needed (that took ~1 event, haha), but I wasn't willing to make drastic changes mid season. It was my first year with the car and didn't know what to expect, and now suspension is my #1 priority.

I agree that all of the available adjustable rear perches are a huge pain, so I'm looking to modify, as well. I've been going the opposite direction, though. Rather than cutting the upper perch and making it adjustable, I think I'm going to make the LCA spring seat flat (cut and weld in a flat piece) and run some adjustable perches with spherical bearings. The hexagonal adjuster just sticks through the bottom of the LCA a bit.

In both the front and rear, I'm making adapters to run a standard 2.5" ID spring (or 65mm ID swift, since they have more options). I'm hoping they only require me to remove the bump stop mounts, rather than cut through the subframe. They should be out of the machine shop in a couple weeks.

I'm looking at this picture of your bilsteins, and it looks like the speed6's had a torrington bearing sandwiched between two plates, whereas you guys do not. Is that the case, or am I just missing it? Here's a pic of what our top hats look like, without that same rubber spring seat. Here's the bearing that is sandwiched between those two stamped pieces.

I almost have enough information to finish my spreadsheet for suspension frequency calculations. How did you come up with the .73 MR for the front suspension? I'm coming up with slightly less (probably negligible, just curious), measuring the forward LCA, and estimating the spring angle (12.24" chassis mount to ball joint, and 9.05" chassis mount to shock mount centers, estimated 70° angle from LCA). I haven't remembered to get the angle when the wheel has been off recently. The rear suspension MR is spot on to what I found, though. I was second guessing myself before seeing your figure, because it requires a LOT more spring than I had expected.

Anywho, good luck on the build, and sorry for all of the questions!
 

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Hey phate!
Glad to see you posting on m6c, always nice to have another Speed6 around!
 
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Discussion Starter #450
Thanks and welcome!

I agree that all of the available adjustable rear perches are a huge pain, so I'm looking to modify, as well. I've been going the opposite direction, though. Rather than cutting the upper perch and making it adjustable, I think I'm going to make the LCA spring seat flat (cut and weld in a flat piece) and run some adjustable perches with spherical bearings. The hexagonal adjuster just sticks through the bottom of the LCA a bit.
I considered a similar solution. I look forward to seeing what you come up with.

I'm looking at this picture of your bilsteins, and it looks like the speed6's had a torrington bearing sandwiched between two plates, whereas you guys do not. Is that the case, or am I just missing it? Here's a pic of what our top hats look like, without that same rubber spring seat. Here's the bearing that is sandwiched between those two stamped pieces.
Thanks very interesting. I'm at a complete loss for why they would use a bearing there. The strut and spring do not rotate - in fact the fork that connects the strut to the LCA prevents any rotation.

For comparison here is my strut mount assembled:





And disassembled:



How did you come up with the .73 MR for the front suspension? I'm coming up with slightly less (probably negligible, just curious), measuring the forward LCA, and estimating the spring angle (12.24" chassis mount to ball joint, and 9.05" chassis mount to shock mount centers, estimated 70° angle from LCA).
From the Formula MR=(a/b)^2 * (c/d)^2
where
a = LCA inner pivot point to the point where the spring attaches to the LCA
b = Length of the LCA from the inner pivot point to the ball joint
c = LCA ball joint to the instant center
d = Center of the tire contact patch to the instant center

The instant center is the intersection of two imaginary lines: one formed by the angle of the UCA and the other formed by the angle of the LCA. This is where you can have some variability. Also, the instant center changes with ride height.

On my car I found
a=9.25"
b=12.625"
c=163"
d=167"
The angle between the UCA and LCA was about 7deg.

The dominant term is a/b. Being off a couple of degrees and even a couple of inches in the c/d measurements makes little difference, but a 1/4" error in the a/b measurements makes a big difference.

I look forward to your build thread.

CR
 

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Thanks very interesting. I'm at a complete loss for why they would use a bearing there. The strut and spring do not rotate - in fact the fork that connects the strut to the LCA prevents any rotation.

For comparison here is my strut mount assembled:

And disassembled:
From what I've read in the past, and after talking to some of the spring manufacturers, they say the spring twists as it compresses. Without allowing one end to rotate, it supposedly binds the spring a little bit, which changes its rate. BUT, those same spring manufacturers (and the folks at rogue engineering, and probably one or two others) said that with short springs that don't have a lot of travel, it's pretty much a negligible amount. The stock MS6 springs are awfully long, maybe the mazda engineers saw it worthwhile. Since I have them available, and after seeing how well they hold up, I'm going to keep mine in. At worst, they don't help anything and I'll probably never be able to tell one way or another.

From the Formula MR=(a/b)^2 * (c/d)^2
where
a = LCA inner pivot point to the point where the spring attaches to the LCA
b = Length of the LCA from the inner pivot point to the ball joint
c = LCA ball joint to the instant center
d = Center of the tire contact patch to the instant center

The instant center is the intersection of two imaginary lines: one formed by the angle of the UCA and the other formed by the angle of the LCA. This is where you can have some variability. Also, the instant center changes with ride height.

On my car I found
a=9.25"
b=12.625"
c=163"
d=167"
The angle between the UCA and LCA was about 7deg.

The dominant term is a/b. Being off a couple of degrees and even a couple of inches in the c/d measurements makes little difference, but a 1/4" error in the a/b measurements makes a big difference.

I look forward to your build thread.

CR
My goal here is to figure out what spring rates I really need. I was using the simpler formula of MR=(a/b)*sin(θ), where θ is the angle between the LCA and spring. [Which is looking at it like a force vector, using only the force perpendicular to the LCA.] Using this, we would have a rising MR, because θ is moving towards perpendicular through bump.



I will double check my measurements, and refine it with the actual θ. I also need to compare this LCA to what's on the car right now, because it's an aftermarket replacement. [Hopefully it isn't different than OEM.] I made those measurements with the aftermarket piece off of the car. I'm pretty confident of those measurements, but I'll double check.

Using your numbers and formula, I get MR = .51. Way back here, you said you got a motion ratio of .73 for the front, which is much closer to what I'm finding. Can you clear that up for me?

This is my suspension thread - MS6 Suspension Data - Mazdaspeed Forums Mostly just gathering information right now, but I have a couple things in the works (like the perch adapters). In the Mazdaspeed world, the MS6 is an unknown and enigmatic beast. Most people think it's just a bigger, heavier version of the speed3 that is only good for 60' times...with mcphailson strut and all. Because of that, though, no one (besides you and me) has gathered this information in an attempt to improve it.
 

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Discussion Starter #452
Ok this may get a little confusing:

Using your numbers and formula, I get MR = .51. Way back here, you said you got a motion ratio of .73 for the front, which is much closer to what I'm finding. Can you clear that up for me?
Sorry, my bad- I omitted the SQRT function in the formula I gave above. It should be:

MR=SQRT[(a/b)^2 * (c/d)^2]

The function basically normalizes the two terms. Now if you plug & chug, you get 0.72 not 0.51.

Strictly speaking: MR=SQRT[(a/b)^2 * (c/d)^2]
or more simply: MR=a/b (as in your example)
The answers should be very similar.

Contrary to the name, MR is not WR/SR. You do not multiply MR by SR to get WR. If you look way, way back at this post I said WR=0.5SR.

What I left out is:

WR=(MR)^2*SR*ACR
where
WR = Wheel rate
SR = Spring rate
ACR = Angle correction factor or sin(θ)

Remember, the angle changes slightly with ride height. I found mine to be 75deg.

Alot of folks (me included - and apparently you) call (MR)^2*ACR the Motion Ratio because it is the value that the SR is multiplied by to get WR, but it is not technically accurate - it is just a constant C.

In this case C=(0.72)^2*sin(75)=0.5.

That’s where I got WR=0.5SR in the earlier post.


So lets do a real world example of of selecting the spring rate for the front of the car:

Let’s say we’re going to lower the car to the point where we have 3” of suspension travel before hitting the bumpstops. When last on the scales we had LF=844lbs, RF= 848lbs. For simplicity, let’s say 850lbs each. I haven’t weighed the wheels, tires, knuckles, control arms, strut, spring and CV shaft, but I guessing there’s about 150lbs of unsprung weight at each corner - leaving 700lbs of sprung. Let’s assume we are going to be driving on a fairly smooth track (AutoX tends to be much bumpier) so we design for a maximum 1.5g bump. Based on these assumptions, we would be absorbing a 700*1.5=1050lb force over 3”, therefore requiring a minimum wheelrate of 1050/3=350lb/in.

Of course WR and SR are not the same, but they a related by a constant that is a function of the control arm linkage ratios, the instant center of the front suspension and angle of the spring.

From above we found WR=0.5SR or SR=WR/0.5

Therefore we, need a 700lb/in spring to handle a 1.5g bump in 3 inches.

The new springs I just installed on my bilsteins are 700lb/in.

Hope this clarifies and I apologize for the confusion. The key is getting the LCA dimensions correct. It is best to remove it from the car.

CR
 

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Discussion Starter #454
Suspension Engineering Continues

So we have our new 700lb/in, 2.5"dia race springs on our newly adjustable perches. As @phate has pointed out in another post, the 6 suffers from a lack of stroke. The front struts have a max of just under 5.5" with no weight on them; add the weight of the car and you have, say 4"; add a bumpstop on the strut piston and you may have around 3" of usable stroke. Remember that because WR=0.5*SR, this means 3" of spring travel equals 6" of wheel travel so all is good.

The problem comes when you start to lower the car. If we lower the car to the point where we only have 3" of wheel travel, this will mean about 1.5" of travel available at the strut. We need to increase the available travel for two reasons:
1- So we aren't riding on the bumpstops.
2- So we don't damage the strut by bottoming it out.

So here is the stock strut mount:




We disassemble it and throw away the top (the plate on the right) and rubber mount in the middle.




Then we cut the bumpstop cup off the bottom plate which is actually the upper spring perch. This will allow the entire strut body to pass thru the spring perch.



Here is the underside of the strut tower where the strut mount would normally be.



Here is our modified mount installed in the car. It will no longer function as a strut mount - only a spring perch.



Here is the strut installed with the spring and bump stop removed and the suspension in full compression (no more available travel). Keep in mind, you would never set your ride height this low, but under the worst bump condition this is the limit of suspension travel.



Close up


Notice that the top of the strut tube is basically where the bumpstop cup used to be. To increase the available stroke and improve our safety margin we fabricate a new strut mount plate and install it above the factory mount. Here we have raised the strut mount 2.25" above the stock location.



It is a little too high and just barely hits the hood. I will remove the lower nuts to drop it down 1/4". I think you get the idea. Additional note: remember my hood has no insulation pad or reinforcing structure:



so I'm guessing a stock hood would not allow the strut tower to be 2" higher. YMMV.

CR
 

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Are you concerned at all about the torque that will be put on the new plate and/or shock rod and seals? You have removed the bushing in the stock mount that allows a bit of flex as the angle of the shock changes through its travel.

I double checked my LCA measurements today as well, and came up with very similar results to my originals. Makes me wonder if the MS6, or later years in general, were changed slightly.
 

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Discussion Starter #456
Are you concerned at all about the torque that will be put on the new plate and/or shock rod and seals? You have removed the bushing in the stock mount that allows a bit of flex as the angle of the shock changes through its travel.
.
Yeah I was thinking the same thing. I ordered some poly bushing to go above and below the plate.
CR
 

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Discussion Starter #457

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Discussion Starter #458
Here's another thing that occurred to me while under the car (I do some of my best thinking under there). :lol: When the car is lowered the upper balljoint is raised causing the UCA to be angled upward from the pivot point. It would be nice to raise the pivot point also to correct the geometry. Recall that we have installed eccentric bushings in the UCA. Here we have the eccentric set toward the balljoint to give us more negative camber.



Our adjustable balljoints give us ample negative camber, so we really don't need more. But if we rotate the eccentric toward the bottom, it will raise the back of the UCA a little and help offset the raising of the balljoint.



Every bit helps. What do you think?

CR
 

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I think, as long as it doesn't decrease the amount of dynamic camber we gain through bump, go for it. We don't have a great camber curve (it's good, but just doesn't seem to be enough), so I would avoid anything that decreases it. I would like to model this suspension at some point, but don't have the capability right now.

Those shock tower bushings should work great. I've been trying to come up with a way to increase shock travel, and this might do just fine. On the MS6, the front camber curve from full droop looks like this. Full droop, of course, is limited by the shock extension. Raising it a little bit shouldn't hurt a thing.

I might be a little concerned about removing the frame stop from the UCA. There have been many cases on other cars where the control arm will dent, or even punch through, the shock tower. I was toying around with the idea of putting a normal type of bump stop out there, but haven't done any measuring of the UCA or the math to see what would happen where.

I'm a little confused again about your motion ratio and shock/wheel travel ratios and shock travel calculations. The shock motion ratio is a direct relationship between the ball joint and strut mount, along with the angle of the shock. I come up with .73, meaning the shock/spring move .73" for every 1" of wheel travel (it's dynamic, but probably close enough for anything we're doing). I'm not sure why you're using the .5 figure, I guess.
 

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Discussion Starter #460
I might be a little concerned about removing the frame stop from the UCA. There have been many cases on other cars where the control arm will dent, or even punch through, the shock tower. I was toying around with the idea of putting a normal type of bump stop out there, but haven't done any measuring of the UCA or the math to see what would happen where.
We're thinking the same thing. I've measured it up and ordered a bumpstop that will line up with the upper ball joint as it reaches the top of its travel. I don't want to rely on my modified strut mount as a bumpstop because if it fails I'll have a hole in my hood. Also the force at the ball joint will be less (by the factor of the MR) than the force on the strut mount. I'll post pic as I get it fab-ed up.

I'm a little confused again about your motion ratio and shock/wheel travel ratios and shock travel calculations. The shock motion ratio is a direct relationship between the ball joint and strut mount, along with the angle of the shock. I come up with .73, meaning the shock/spring move .73" for every 1" of wheel travel (it's dynamic, but probably close enough for anything we're doing). I'm not sure why you're using the .5 figure, I guess.
I recall from engineering school, whenever they gave us a new formula they would send us to lab to collect experimental data and prove the formula accurately predicted the behavior we expected. So here we go:

Starting with the LCA horizontal (approximating normal ride height) We have the center of a wheel stud at exactly 5".



And at the same time the top of strut sleeve is 8" from the strut mount.



We then raise the wheel exactly 4".



And we find the strut has risen 2-9/16"



Based on this empirical data it appears WR=0.64SR. Hmmm - very interesting. Looks like I'm getting a bad lab grade on this one. :p Thoughts?
 
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