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Question about lowered FC front suspension

Old 10-26-07, 01:16 AM
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Question about lowered FC front suspension

My FC is currently "too low" as the front lower arm is parallel with the ground and so gains positive camber on compression.

Can one move the ball joint mount from the bottom of the lower arm to the top in order to gain proper angle?

I can see in bump compression this will now pull on the mounting bolts instead of pushing the ball joint mount into the lower arm like stock position, but many cars have the strut suspension set up just this way from the factory.

Or do I just need to raise the car to proper height?
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Old 10-26-07, 04:55 AM
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Ive seen pictures of this done, i belive they did it to eliminate bump steer iirc, however it did work.

I dont see how it would cause adverse effects ont he ball joint either in respect to longevity
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Old 10-26-07, 07:35 AM
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It won't change your geometry. You need to change the relationship between the spindle and ball joint.
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Old 10-26-07, 09:34 AM
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The correct way to do this is with Camber plates. Talk to the folks at Mazdatrix and they can fill you in on what you need to do. Raising the car will not help your handling other than improving your camber under load.
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Old 10-26-07, 10:49 AM
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Even with camber plates, FC's will still lose camber under load if you have flexible bushings. Just a design of the McPherson Strut suspension.
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Old 10-26-07, 11:40 AM
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You'll never get more than a small amount of camber gain on a strut squishy bushings or no, it's a function of the geometry, not the bushings. People space out the lower control arm pivot more for roll center correction than for camber gain, as the difference in camber gain will be small.

This is talking about dynamic camber change as the wheel moves, not static camber, which is what camber plates change. Camber plates will change what the dynamic camber numbers are, but it doesn't really affect how the numbers change.
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Old 10-26-07, 02:56 PM
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So, I am hearing that I should do it to help correct the roll center, but basically don't wory about camber loss or gain under compression as it is such a small number.

Any downsides to this simple mod?
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Old 10-26-07, 03:41 PM
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No downside except it isn't that simple on the FC, on the FB its easy. If you are able to do it it will make your front anti roll bar more effective so if the car is balanced right now be prepared for it to understeer.
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Old 10-26-07, 05:18 PM
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OK, so just bolting the ball joint mount to the top of the lower arm instead of the bottom will not change geometry since the pivot is in the same spot, but it will change where along that geometry the suspension travel is at rest.

Is there any downside to bolting the ball joint mount to the top of the lower arm?
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Old 10-26-07, 09:23 PM
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The shape of the arm doesn't matter. The pivot points are all that affect the radius and suspension geometry.

The only thing I can think of that might be changed would be the anti-roll bar arm angle when you move that bracket.
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Old 10-27-07, 02:21 PM
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Originally Posted by BLUE TII View Post
OK, so just bolting the ball joint mount to the top of the lower arm instead of the bottom will not change geometry since the pivot is in the same spot, but it will change where along that geometry the suspension travel is at rest.

Is there any downside to bolting the ball joint mount to the top of the lower arm?
it doesnt matter, it doesnt change the relationship of the spindle to the ball joint.

unfortunately this is really hard to change on the FC, FB is much much easier.

if you look at pics of FC's cornering, you will see a lot of positive camber on the outer front wheel.

which is why we need camber plates.

so we compromise, by running the car a little too low, and running a lot of static negative camber.

the rear is comprimised too, but in the opposite way, it goes negative, and toes in with squat.
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Old 10-27-07, 03:58 PM
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Hmm, at least this idea has got me learning about strut front ends a bit.

From WIKI

They [double wishbone] also provide increasing negative camber gain all the way to full jounce travel unlike the MacPherson strut which provides negative camber gain only at the beginning of jounce travel and then reverses into positive camber gain at high jounce amounts.
This is the phenomenon I am attempting to address as my suspension is lowered and so already into the stock jounce travel.

What had me thinking about relocating the hub carrier to lower arm ball joint mount is many people attribute the camber change to the position of the lower arm. Camber gain as it travels from downward slope from inboard side to horizontal and camber loss as it travels from horizontal to upward slope.

However, this appears to be a correlation not the cause.

someone that had played with suspension geometry programs and strut designs say it looks like the switch over to camber loss happens when the inside angle between the lower arm and the strut becomes greater than 90 degrees.

Mmm.

Then I read

Milliken and Milliken say that the camber gain is basically the inverse tangent of the reciprocal of the horizontal distance from the contact patch to the instant center.
That just rolled off my brain like my skull was freshly Rain-X'ed when I first read it.

Once I dissected the sentence to make sense of it I could see what they were saying, but you need a dynamic model that tracks the changing instant center. Actual work! Much harder than reading (mis)information off the interweb

Easiest thing would be to take the spring off my front coilovers and raise/lower the front of the car from the center with a camber gauge on a rim

Or trust others that the amount of camber gain/loss is not worth worrying about- that is even easier.
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Old 10-27-07, 04:13 PM
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Another argument I have read for not lowering a strut equipped vehicle beyond the point that the lower arm is parallel to the ground is-

Once the arm is slopped up (relative to the chassis) in a corner the side loads from cornering will also act to compress the suspension further compounding the compression present from body roll.

Mmmkay, but then it seems to me if the arm still slopped down like stock in a corner a side load would bind the suspension from compressing and that would suck if there were any bumps in the corner- so that argument sucks.


I guess this is the answer to ourlowering problems :P Yawpower to the rescue. I bet it helps with weight reduction too if you race with your wallet in your pants.

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Old 10-27-07, 04:34 PM
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Details on the suspension you posted? I checked yawpowers site and saw mention of it but no technical information or even a price
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Old 10-27-07, 04:42 PM
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Real racing = Real money

It would be nice if they would knock a bunch of those out though and tell you what height to run it at, but then the original owner wouldn't have the advantage he paid lots of $$ for to have Yaw Power develop that project for.

It would be a little wrong for Yaw Power to knock off a bunch of these and sell them on Ebay looking at it from this perspective wouldn't it.

My guess is that is why they don't have more info and a price for the suspension- it was someones competitive advantage they paid $$ to have Yaw Power develop.
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Old 10-27-07, 04:51 PM
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Ahh, i was not aware that was a one off. i thought it was something they developed, not something they developed for someone.
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Old 10-27-07, 05:42 PM
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Well one problem would be that a suspension like that is illegal for the classes that most of the road race FC's run in, so there's a very small market. IIRC that was made for an autocorss car, and there's not many people seriously autocrossing FC's, and fewer still in the high up classes that allow that sort of thing. Those are Dynamic struts, which are probably on the order of $1000/ea just for the cartriges, then add the rest of the custom fab work and you're looking at maybe $3000 for the front alone. So not many people are able to run it, and of those who can not all will have the $$ and motivation to do something like that.
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Old 10-27-07, 06:31 PM
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Its legal in EP and I think the $3000+ guesstimate is close.
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Old 10-27-07, 09:17 PM
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The FC is under the restricted suspension rules in Prod though, so doesn't that mean that something like this is disallowed then? It would appear to me that it may be allowed in the unrestricted rules, but I don't see anywhere in the restricted rules where it says that you can run fabbed uprights. You could still change the pivot point, but you'd need to do it with the stock uprights.
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Old 10-27-07, 10:32 PM
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Restricted rules just end up meaning you can't move suspension mounting points on the chassis.

Any strut is allowed, so that is how those fit the rules. The rest of the parts fit under the free control arm and bushing parts. The hardest part of the of making the new parts work is that the actual pivot points on the chassis side can't be moved, even with offset bushings. The fact that you can put the outer points anywhere make offset bushings a non-issue.

Before anybody says offset bushings don't change the pivot point, here is how they work. The original center/bolt is used in a hole that is offset in the bushing. That bushing is held tight to the chassis and doesn't move. The OUTSIDE of the bushing, that is offset, is the new pivot surface. The center of that pivot surface is the new pivot point.
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Old 10-28-07, 12:49 AM
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Hmm, I guess it goes to show that I need more practice reading the rules to see exactly what's allowed and what's not. I would have assumed that since the damper and the upright were seperate that it wouldn't be considered to be part of the strut.

For EP too you'll be limited by the wheels, as you can't move the point down that much in a 15" wheel.
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Old 11-11-07, 03:00 PM
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Originally Posted by Black91n/a View Post
Well one problem would be that a suspension like that is illegal for the classes that most of the road race FC's run in, so there's a very small market. IIRC that was made for an autocorss car, and there's not many people seriously autocrossing FC's, and fewer still in the high up classes that allow that sort of thing. Those are Dynamic struts, which are probably on the order of $1000/ea just for the cartriges, then add the rest of the custom fab work and you're looking at maybe $3000 for the front alone. So not many people are able to run it, and of those who can not all will have the $$ and motivation to do something like that.
i didnt look to make sure at sevenstock, but i kinda had the feeling that that suspension is under dave lemon's ep vert...
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Old 11-12-07, 01:38 AM
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Instead of moving the pivot point at the lower arm (and thereby changing track width-whole new set of problems), has anyone relocated the strut tower sheetmetal inwards, say, an inch? That's looking to be the correction i'll make using my tig welder. My car isn't limited to the rules of e-prod. I'm primarily time attack.

Last edited by BFGRX7; 11-12-07 at 01:40 AM. Reason: clairification
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Old 11-12-07, 02:16 AM
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Well that'll change the camber unless you change the angle between the strut and the upright. Relocating the lower pivot doesn't have to change the track width and if it does it'll be a fairly monor change. Basically what changing the lower pivot does is restore some of the pre-lowered geometry.
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Old 11-12-07, 12:49 PM
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Exactly! Bringing the strut tower base inwards and possibly down towards the engine will, in fact, change the relationship (read sharpening the angle) between the strut and the lower arm without having to move the lower arm outwards. You’ve now reintroduce the proper lower arm to strut angle (less than 90degrees). Your camber would still work independent of the this relocating of the strut base-you could even engineer greater camber into the strut depending on how much further inwards you locate the strut base. Obviously there’s a limit to how far you can go but considering the 2nd gen already has a tendency towards oversteer, changing the track outwards, even if only by a small amount, could exacerbate the 2nd gens’ issue-something I can do without.
I wasn’t quite sure if people were considering raising the attachment point of the lower arm or going with the “cam” idea. Raising the attachment point seems to be the better option over the cam idea.
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