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Old 04-26-2012, 11:30 PM   #1126
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Quote:
Originally Posted by glhs377 View Post
i fully understand how it works, so much that i'm saying you can achieve.. FUKKALL(defined herein as an inconsequential amount, an amount that would be measurable, however the results of said changes would not be measurable or repeatable in any reasonable way with regard to to many other factors whose inconsistency weigh in as more important in the measuring of the results, like say the amount of sunlight a tire has had, or the amount of urine in the drivers bladder) in camber gain from moving the strut top around from the factory location. not static, not anything but camber gain.

edit: just made some datasets and gave them to Jimmy to make into pretty graphs. moving a strut top over on a 17" long (which is very short) strut, 1.5"(which you'll never see on a production chassis, i have less than that adjustment in my KW competition tophats, and that's full travel, not just one way off center.) and you get ~ 0.1 deg of extra camber gain in 2" of compression. which, as previously stated, is ridiculous. so a realistic situation where a 3000lb car has ~1.5" of compression travel in a turn, with 300 some lb/in springs and ARBs,(about the softest you can go on coilovers, oh, which you need to be able to move the strut top over) with a realistic tophat adjustment of half what i calculated out, you get 0.04 deg of extra camber.

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Last edited by FXTSPORTS08; 04-26-2012 at 11:39 PM.
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Old 04-26-2012, 11:32 PM   #1127
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while that looks way too conclusive for the data i sent, it's more effort than i'm willing to spend on this terrible conversation anymore.

Quote:
Camber_R as a function of Ride
-2.000 -0.989
-1.900 -0.949
-1.800 -0.908
-1.700 -0.866
-1.600 -0.823
-1.500 -0.778
-1.400 -0.733
-1.300 -0.687
-1.200 -0.639
-1.100 -0.591
-1.000 -0.542
-0.900 -0.492
-0.800 -0.441
-0.700 -0.389
-0.600 -0.336
-0.500 -0.282
-0.400 -0.227
-0.300 -0.172
-0.200 -0.115
-0.100 -0.058
0.000 -0.000
0.100 0.059
0.200 0.119
0.300 0.179
0.400 0.241
0.500 0.303
0.600 0.366
0.700 0.429
0.800 0.494
0.900 0.559
1.000 0.625
1.100 0.692
1.200 0.759
1.300 0.828
1.400 0.897
1.500 0.966
1.600 1.037
1.700 1.108
1.800 1.180
1.900 1.252
2.000 1.326

Camber_L as a function of Ride
-2.000 -1.199
-1.900 -1.147
-1.800 -1.095
-1.700 -1.041
-1.600 -0.986
-1.500 -0.931
-1.400 -0.874
-1.300 -0.817
-1.200 -0.759
-1.100 -0.700
-1.000 -0.641
-0.900 -0.580
-0.800 -0.519
-0.700 -0.456
-0.600 -0.394
-0.500 -0.330
-0.400 -0.265
-0.300 -0.200
-0.200 -0.134
-0.100 -0.067
0.000 -0.000
0.100 0.068
0.200 0.137
0.300 0.207
0.400 0.277
0.500 0.348
0.600 0.420
0.700 0.492
0.800 0.565
0.900 0.639
1.000 0.713
1.100 0.789
1.200 0.864
1.300 0.941
1.400 1.018
1.500 1.096
1.600 1.174
1.700 1.253
1.800 1.333
1.900 1.413
2.000 1.494
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Old 04-26-2012, 11:35 PM   #1128
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Old 04-26-2012, 11:44 PM   #1129
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Originally Posted by BoozeRS05 View Post
My train ride is 8 hours, wonder what the over will be on the number of times I look at the pictures.

After that I'll have a 6 hour ride home with her, alone at night on a Sunday, across PA.

Good job finding that. I have a guy flying in from Missouri to pick up a used CTS 4. Apparently it is the only GM certified diamond white with black interior performance package /nav available this side of the rockies. 600 mile drive home with that one.

LOL @ Jimmy. I am pretty sure I know where to get those.
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Old 04-26-2012, 11:56 PM   #1130
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Pivots C and D are fixed in the X & Y axis and can only rotate. Pretend the strut in the bottom example is at a 45 degree angle.

In the top example, as point A moves up, it pretty much only moves up in the Y axis.

In the bottom example, as point A moves up, it also HAS to move in the X axis as well. There's your camber gain.

That makes the following statements false:

Quote:
Originally Posted by glhs377 View Post
what are you guys, daft? the inclination of the strut doesn't matter, it's the points between the strut top and LBJ in relation to LBJ and inner arm pivots. oh no there's more bending load there..
edit: clint yeah.
Quote:
Originally Posted by glhs377 View Post
homeboy, you started this. and you stated it with the misnomer that strut inclination has something to do with camber gain. that is all.
Quote:
Originally Posted by glhs377 View Post
abhishek, you do realize that from that pic you can not determine anything about the pickup points of the LCA, which has an everything more to do with camber gain than the angle between the axial positioning of the strut vs anything else. i'll draw you pictures, in due time, or draw them yourself. basically, if the steering axis vs the LCA angle is acute, you're gaining camber in compression. strut axis, does not matter when your'e talking about camber gain. if you want to go jibba jabba bout roll center height and instant center, then by all means, use the strut axis as a reference.

Last edited by MRF582; 04-27-2012 at 12:15 AM.
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Old 04-27-2012, 12:07 AM   #1131
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Quote:
Originally Posted by MRF582
Pivots C and D are fixed in the X & Y axis and can only rotate.

In the top example, as point A moves up, it pretty much only moves up in the Y axis.

In the bottom example, as point A moves up, it also HAS to move in the X axis as well. There's your camber gain.
But doesn't your critique of the BRZ suspension lack the crucial component of your two diagrams?
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Old 04-27-2012, 12:12 AM   #1132
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i used soemthing a bit fancier.. it was easier for me, maybe cause i've been through this before, but then maybe i just don't understand it..


all i did was move the upper point on the L strut inboard 1.5" for those numbers, hence increasing the inclination. i didn't move the bottom also inboard 1.5". i know what those results are, and they're not worth talking about. as are these.

edit: something to keep in mind, as you can see(and probably ignore) the LCA on this simulation is in an ideal starting position, unlike the LCA and it's pickup points(the LBJ that's inverted in the knuckle? yeah remember that pivot's not in the arm) in a subaru.


i'm not preaching here, i'm telling you, as a friend to shut up, you're out of your element. your world isn't flat, etc.

Last edited by glhs377; 04-27-2012 at 12:24 AM.
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Old 04-27-2012, 12:19 AM   #1133
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For a camber curve to be 'crappy' doesn't it have to go positive after a certain displacement? That can't be proven by the BRZ suspension silhouette. Non optimal is a given, but it looks like more info would be needed to decide its that bad. But I don't understand most of what has been referenced, so I'm tuning out.
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Old 04-27-2012, 12:22 AM   #1134
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Shek, the two diagrams you drew will act exactly the same (except the bending forces which will own the **** out of the linkage you drew from your strut to knuckle in your first diagram).



Quote:
Originally Posted by isis View Post
For a camber curve to be 'crappy' doesn't it have to go positive after a certain displacement? That can't be proven by the BRZ suspension silhouette. Non optimal is a given, but it looks like more info would be needed to decide its that bad. But I don't understand most of what has been referenced, so I'm tuning out.
You have to factor in your roll rate and strut flex as well. It won't go positive necessarily depending on how much static camber you run, but it's a decreasing rate linkage, so you'd get to zero and positive rather quickly without enough adjustment.

There's a pic of some guy in a 240SX with -5.5 degrees static camber, and just about eeks out a flat contact patch at full (autocross) cornering load. That's also partially why you see DTM cars and australian V8 cars w/ retardo camber.

Last edited by stealthx32; 04-27-2012 at 12:32 AM.
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Old 04-27-2012, 12:38 AM   #1135
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Let me quote Suspension Geometry and Computation by John C Dixon.
Quote:
The strut-and-arm suspension, commonly just called a strut suspension, typically uses a basically
transverse lower arm, with the upper arm and wheel carrier (wheel upright) replaced by an integrated
unit of wheel carrier, slider and spring–damper unit, acting on an upper trunnion where it connects to the
inner part of the bodywork. The upper joint is a really a combination of the slider with a ball joint, or rubber
bush, the latter allowing various angular movements. The combination acts geometrically like a trunnion,
which is a slider passing right through a swivel joint (in two dimensions) or ball joint (in three dimensions),
as seen in Figure 12.14.1. The steering action normally acts about a steering axis passing through the lower
ball joint and the trunnion point. However, a separate steering axis could be provided, as used to be done on
some double-transverse-arm suspensions.
The two-dimensional analytical methods applied to the double-transverse-arm suspension are easily
adapted to the common strut suspension. The one issue to be resolved is how to find the equivalent upper
arm. The plane of the equivalent upper arm is through the trunnion point and perpendicular to the strut
slider centreline.
Intersecting this with the transverse vertical plane gives the equivalent arm, as usual, but
with length yet to be determined. Note that the strut slider is generally not aligned with the ball joint on the
lower arm, so not coinciding with the steering axis which passes through the two joints, Figure 12.14.1.
The lower arm angle is u YL , positivewhen the outer ball joint is higher than the axis, but usually negative in
the static position.
The upper arm length can simply be taken effectively as infinite, that is, as having zero shortness.
A slightly better equivalent is to take it to be equal to the swing arm length in front view and the pitch arm
length in side view. In Figure 12.14.2, AB is the lower arm, E is the foot of the perpendicular from B onto
the slider centreline, DE is the slider centreline, and BD is the steering axis through the lower ball joint B
and trunnion centre D. Figure 12.14.2(b) shows the velocity diagram for a lower arm angular velocity W .
The fixed points are A and C. The line ab has length value (units m/s)


Then later on...

Quote:
Application of the two-dimensional analytical equations of Table 12.14.1 to design of a strut-and-arm
suspension is very revealing. Whereas the double-arm suspension is very adaptable and can be specified to
give almost any desired coefficients, the strut-and-arm suspension is very limited because of the long
equivalent upper arm. The arm shortness difference
S YD S YU S YL
is negative, so the quadratic bump camber coefficient
BC2
S YD
2H BJDis inevitably positive, whereas negativevalues are favoured fordouble-armsuspensions. Also, control of the
bump scrub rate variation is effectively lost, this, although being desirably negative, is much too large in
magnitude, so control of the roll centre movement is poor. Even the linear bump camber coefficient
BC1
1
R S

u YD0
H BJD
may be a problem, becausetheball jointheight differenceH BJD islargerthanforthedouble-arm suspension,
so to achieve a desirable swing arm length of about 1.5 m requires a very large arm angle difference u YD0 .
This indicates need of a very steeply inclined slider,
which is impractical forother reasons – forexample, the
excessive steering axis inclination angle is detrimental. This could be overcome by using a separate steering
axis, but at extra cost. The only coefficient not really compromised is the linear bump scrub variation, so at
least the initial roll centre height can be fixed correctly. However, the lower arm may be set at a steeper angle
than is otherwise desirable to give a higher initial roll centre, and to reduce the swing arm length.
Geometrically, then, the strut-and-arm is a poor suspension configuration, and is used rather because it
has a good motion ratio for the spring and damper, spreads the loads into the body well, and is economic in
production.
Some manufacturers have sought to combine some of the benefits of both systems by using a double-
arm system for the geometry, with the spring and damper acting, with pivotal connection, down onto the
top of the upright or onto the end of the top arm (see Figure 1.6.8).
In sports and racing cars, the adaptability of the double-arm suspension is highly valued, and the
geometric limitations of the strut-and-arm are a significant problem. In some cases conversions are made,
often retaining the existing lower arm, using a subframe on each side, mounted at the lower arm and at the
strut top, providing the mounting points for a new, upper, arm. This will cause problems with the steering
unless the rack is repositioned and the length is corrected. This is not necessary in the special case of a rack
which is located immediately in line with the lower arm.
12.17 Strut Numerical Solution in Three Dimensions
The strut-and-arm suspension can be analysed numerically in three dimensions by similar methods to the
double-arm suspension, with some detail changes because of the slider trunnion (compare Table 12.17.1
with Table 12.12.1).
I'm sending you the entire book. Read section 12.14 starting on page 244.

If you disagree with this, I suggest you take it up with Mr. Dixon.

Also, to address some other points, you don't start losing camber until the angle between the strut center line and the LCA becomes obtuse. Just because the LCA is parallel to the ground, doesn't mean **** by itself.

Basically, to figure out wheel inclination (camber) you need to find the FVSAL. To find the FVSAL, you need to find the FVIC. To find the FVIC you need to know how the strut axis center line relates to the LCA.

Last edited by MRF582; 04-27-2012 at 01:22 AM.
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Old 04-27-2012, 03:00 AM   #1136
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Originally Posted by MRF582 View Post
Bettner, OBDII drive cycle...Like I said, it's not the number of drive cycles but the kind of driving.
http://www.i-club.com/forums/engine-...-sticky-32429/
fixed it in ATR
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Old 04-27-2012, 03:09 AM   #1137
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Originally Posted by MRF582 View Post

Clinton apparently only thinks in terms of off-road baja where you want camber to NOT change during suspension movement. This is exactly opposite of what you want for tarmac driving.
1.5 degree negative camber at ride height with a gain to I believe 3 degrees at full compression. So a 200% gain is not changing? Spew all you want, reading it in a book only goes so far in life.

keep quoting graphs and pictures all you want.
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Old 04-27-2012, 07:54 AM   #1138
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Quote:
Originally Posted by bettner12 View Post
1.5 degree negative camber at ride height with a gain to I believe 3 degrees at full compression. So a 200% gain is not changing? Spew all you want, reading it in a book only goes so far in life.

keep quoting graphs and pictures all you want.
So you gained 1.5 degrees of camber through how many degrees of roll/suspension movement? IIRC, baja cars have a LOT of suspension travel. So a cumulative gain of 1.5 degrees from static is actually quite a piss poor camber curve for tarmac. That's even worse than an Impreza!

But then again, that's why no one in their right mind would run that suspension setup for tarmac driving where you want the wheel to gain camber as the body roll takes it away.

Not to mention, your use of 'percent' in this application is deceiving. You gained 1.5 degrees from static ride height to max compression. What if you started out at 0 degrees of camber. Does that mean your suspension was teh Super Awesome because you got an infinity percentage of camber gain?

And THIS is exactly why you don't talk about camber gain as a percentage of itself but rather as a unitless value of degree gain divided by degree of body roll, or degree per suspension travel unit length.

Last edited by MRF582; 04-27-2012 at 08:06 AM.
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Old 04-27-2012, 07:55 AM   #1139
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fixed it in ATR
Also could've fixed it for free with OpenSource
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Old 04-27-2012, 09:19 AM   #1140
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Geez.....I'm feeling really under educated right now.
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Old 04-27-2012, 09:41 AM   #1141
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I think it's sinking in now. But if you need such an aggressive strut angle to get even a decent camber curve, wouldn't moving the strut tops with camber plates be pretty pointless anyway? I mean not pointless, but wouldn't it be such a small improvement in motion that all you really gain is static camber?
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Old 04-27-2012, 10:00 AM   #1142
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I think it's sinking in now. But if you need such an aggressive strut angle to get even a decent camber curve, wouldn't moving the strut tops with camber plates be pretty pointless anyway? I mean not pointless, but wouldn't it be such a small improvement in motion that all you really gain is static camber?
From looking at the data this is my conclusion as well. It seems that the strut inclination would have to be very large in order to see any real benefit. Probably not reasonable in a street car that is to be sold to the masses.

If there is a large strut inclination wouldn't that ruin some of your motion ratios? Wouldn't that have negative effects on spring rates as the suspension goes through its travel? Maybe this is all covered by Jason's main point though that the travel is small so therefore the effect will be very small.
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Old 04-27-2012, 10:25 AM   #1143
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Quote:
Originally Posted by isis View Post
I think it's sinking in now. But if you need such an aggressive strut angle to get even a decent camber curve, wouldn't moving the strut tops with camber plates be pretty pointless anyway? I mean not pointless, but wouldn't it be such a small improvement in motion that all you really gain is static camber?
Quote:
Originally Posted by FXTSPORTS08 View Post
From looking at the data this is my conclusion as well. It seems that the strut inclination would have to be very large in order to see any real benefit. Probably not reasonable in a street car that is to be sold to the masses.

If there is a large strut inclination wouldn't that ruin some of your motion ratios? Wouldn't that have negative effects on spring rates as the suspension goes through its travel? Maybe this is all covered by Jason's main point though that the travel is small so therefore the effect will be very small.
Agreed. But even replacing your stock battery with a lightweight one has no measurable improvement in performance. But if you're trying to optimize something, you do it because every little bit helps, right? Isn't that why Jason spent hours shaving a few ounces of weight out of his lightweight battery tiedown? One could argue that doing all that does FUKKALL (as defined by Jason). But you won't find me arguing that it doesn't help.

The problem I had was with the following statements by Jason. They are fundamentally wrong.

Quote:
Originally Posted by glhs377 View Post
what are you guys, daft? the inclination of the strut doesn't matter, it's the points between the strut top and LBJ in relation to LBJ and inner arm pivots. oh no there's more bending load there..
edit: clint yeah.
Quote:
Originally Posted by glhs377 View Post
homeboy, you started this. and you stated it with the misnomer that strut inclination has something to do with camber gain. that is all.
Quote:
Originally Posted by glhs377 View Post
abhishek, you do realize that from that pic you can not determine anything about the pickup points of the LCA, which has an everything more to do with camber gain than the angle between the axial positioning of the strut vs anything else. i'll draw you pictures, in due time, or draw them yourself. basically, if the steering axis vs the LCA angle is acute, you're gaining camber in compression. strut axis, does not matter when your'e talking about camber gain. if you want to go jibba jabba bout roll center height and instant center, then by all means, use the strut axis as a reference.
He could've said, 'correct, but you won't be able to feel the difference'. Instead, he said 'you are wrong' and went on to spew downright incorrect information.

THAT is what I have been arguing this whole time. It looks like everyone sees that now, I hope.

Or should we use Jason's logic in every discussion and ignore discussing the question at hand and simply address the point which is likely to make a bigger difference. If someone asks, if stiffer than stock springs help, should we tell them they are wrong and that they should know that stiffer springs do FUKKALL to improve track time and that better tires do significantly more? Then take it one step further and tell them to focus on nothing but aero dynamics since trying to squeeze mechanical grip out of a car is futile, unless you like to chase cones in a parking lot.

Why bother with anything else then? Especially stuff like shaving a few ounces of weight out of a battery tiedown.

Last edited by MRF582; 04-27-2012 at 10:44 AM.
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Old 04-27-2012, 10:26 AM   #1144
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Quote:
Originally Posted by FXTSPORTS08 View Post
From looking at the data this is my conclusion as well. It seems that the strut inclination would have to be very large in order to see any real benefit. Probably not reasonable in a street car that is to be sold to the masses.

If there is a large strut inclination wouldn't that ruin some of your motion ratios? Wouldn't that have negative effects on spring rates as the suspension goes through its travel? Maybe this is all covered by Jason's main point though that the travel is small so therefore the effect will be very small.
Alter, yes, but ruin? Are you saying a double wishbone suspension has a worse motion ratio than a McStrut? Or is it merely different?
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Old 04-27-2012, 10:48 AM   #1145
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Alter, yes, but ruin? Are you saying a double wishbone suspension has a worse motion ratio than a McStrut? Or is it merely different?
Well the motion ratio that deals with the strut angle really doesn't have a lot to do with what type of suspension but more the inclination of the strut even on double wishbone cars. If the strut inclination is too high you end up with a *not sure if this is the right way to say it* reverse progressive spring response (assuming linear springs), this can all be compensated for but so can the camber curve.
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Old 04-27-2012, 11:01 AM   #1146
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Originally Posted by FXTSPORTS08 View Post
Well the motion ratio that deals with the strut angle really doesn't have a lot to do with what type of suspension but more the inclination of the strut even on double wishbone cars. If the strut inclination is too high you end up with a *not sure if this is the right way to say it* reverse progressive spring response (assuming linear springs), this can all be compensated for but so can the camber curve.
You are really grasping at straws here trying to find some way to disagree with me, right?

So are you saying a SLA (short long arm) suspension has a 'worse' motion ratio than most MacPherson Strut setups?

For a strut, this 'worse' motion ratio as you define it is inversely proportional to how much 'better' the camber curve is. Would you rather have the ability to use linear springs at the cost of camber gain in a McStrut car? You would be a fool to make that trade-off.

The fact of the matter is, when you design a production car with a McStrut you try to angle that damn thing in as far as the other departments in your company will allow. Engine department wants to use a wider than your mom's ass motor. Great, there goes the ability to run a proper suspension. And then the product manager and aesthetics guru says the car has to be narrow AND have a short hood line. GREAT, now you have to stuff a McStrut in there inboard of the wheel instead of having the spring perch above the tire. So you have to extend the spindle inwards a bit and trash your strut inclination. Well, **** THAT. I quit.

They really should've called this the Fubaru BRZ.
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Old 04-27-2012, 11:15 AM   #1147
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You are really grasping at straws here trying to find some way to disagree with me, right?

So are you saying a SLA (short long arm) suspension has a 'worse' motion ratio than most MacPherson Strut setups?

For a strut, this 'worse' motion ratio as you define it is inversely proportional to how much 'better' the camber curve is. Would you rather have the ability to use linear springs at the cost of camber gain in a McStrut car? You would be a fool to make that trade-off.
I guess it just seems like you are only looking at optimizing the suspension in one particular way. Since neither of us have data to show how much the camber curve will change and how much that will alter the motion ratios its really hard to talk about what is or isn't optimized for a specific car. Just like you pointed out that you can bandaid suspension to fix motion ratios you can do the same for camber. Which makes more sense? That depends on far more variable than any of us have discussed so far.
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Old 04-27-2012, 11:20 AM   #1148
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Shek, make a 2 bar linkage with your arm, elbow is the LBJ, shoulder is the LCA pivot, fingers are your top hat. Shorten your forearm by closing your hand. Does it really matter where your fingers are pointing?
Depends, if you want to walk like an Egyptian or not.
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Old 04-27-2012, 11:25 AM   #1149
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I guess it just seems like you are only looking at optimizing the suspension in one particular way. Since neither of us have data to show how much the camber curve will change and how much that will alter the motion ratios its really hard to talk about what is or isn't optimized for a specific car. Just like you pointed out that you can bandaid suspension to fix motion ratios you can do the same for camber. Which makes more sense? That depends on far more variable than any of us have discussed so far.
Having to run more static camber reduces straight line stability over uneven rough surfaces and degrades braking performance especially when the car is tuned for dry weather and it starts raining...

Why are you still so caught up over motion ratios? Are you aware that most good double wishbone suspensions have way 'worse' (as you define it) motion ratio than a McStrut? Are you surprised they've traded a 'worse' motion ratio for better camber curves? Generally speaking, even with a linear spring rate and 'worse' motion-ratio the spring force still goes up as the suspension compresses. f=-kx. Yeah? And if you really have trouble sleeping at night because your motion-ratios are 'worse' you can just run progressive rate springs (like most production cars) which have no negative effect on performance. That's why it's not a band-aid, it's just proper design. Having to run a **** load of static negative camber is a band-aid because your inherent suspension geometry eats dicks.

Last edited by MRF582; 04-27-2012 at 11:48 AM.
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Old 04-27-2012, 12:42 PM   #1150
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