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Discussion Starter #1
I've been thinking about how to get more negative camber in the rear of the car and it occurred to me that I might be able to "notch" the outer hole of the rear UCAs to make an oblong/oval hole that allows me to move the top part of the knuckle inward. Has anyone done that or thought any problems it might cause?
 

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Can something like this be fabricated for the rear? These are options available for my DD, Honda Accord. I know that the IRS of my Honda is completely different than it is on our MN12s, but I'm only presenting this to see if this concept can be fabricated to work on the MN12.

Rear UCA

37732


Rear LCA

37733
 

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Enough to lay in the rim?

Sorry, I couldn't resist. :sneaky:

 

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Can something like this be fabricated for the rear? These are options available for my DD, Honda Accord. I know that the IRS of my Honda is completely different than it is on our MN12s, but I'm only presenting this to see if this concept can be fabricated to work on the MN12.

Rear UCA

View attachment 37732

Rear LCA

View attachment 37733
there’s a reason the stock arm is a U shape, a straight rod won’t clear the chassis, same with similar ideas that have been kicked around with the front strut rods.

I think Welding the holes shut and drilling it further inboard is the best route(I think they’re too flimsy and the sleeve too small to oblong and expect them not to shift). No need to make it complicated.
 

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Discussion Starter #6
How many degrees of negative camber are you trying to achieve?
All of them. ;)

Right now I'm getting about -1 degrees out of the stock setup. I would love to get -3 or so.

there’s a reason the stock arm is a U shape, a straight rod won’t clear the chassis, same with similar ideas that have been kicked around with the front strut rods.

I think Welding the holes shut and drilling it further inboard is the best route(I think they’re too flimsy and the sleeve too small to oblong and expect them not to shift). No need to make it complicated.
As long as I don't have to worry about interference then what I could do is oblong the holes and then weld a washer on the outside of the arm to keep it from shifting. I think I have a spare set I can practice on. I guess the math I would have to figure out is how much to oblong the holes and how much negative camber it would give.
 

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Why not something adjustable, like the one in CD's lower pic, but suitably curved with a press to the desired U shape?

Give me the measurements of the rear pivots, in the plane running vertically thru the axle, and I'll do the math.

Or, if someone has a good picture of a loose irs assembly from the rear, perpendicular to the axle; I can work from that.

I love maths, lol.
 

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Discussion Starter #8
Why not something adjustable, like the one in CD's lower pic, but suitably curved with a press to the desired U shape?
If there were such a thing I would be interested. I've thought about making something but this method is actually easier.

Give me the measurements of the rear pivots, in the plane running vertically thru the axle, and I'll do the math.

Or, if someone has a good picture of a loose irs assembly from the rear, perpendicular to the axle; I can work from that.

I love maths, lol.
If the plane is 90 degrees and the pivot point is 10 inches from that point, how many degree change is it to step back .3825 inches from the plane?

See lousy picture for the idea:
37736
 

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If you're only getting -1, you must not be lowered much, or you've got something unusual going on. That said, -3 isn't going to perform particularly well.

If you're going this route, I'd agree that welding up the hole or at least welding a washer in place would be necessary to keep the camber from changing on its own. Move it in, then use the stock UCA bushing to get your adjustment.
 

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Discussion Starter #10
If you're only getting -1, you must not be lowered much, or you've got something unusual going on. That said, -3 isn't going to perform particularly well.

If you're going this route, I'd agree that welding up the hole or at least welding a washer in place would be necessary to keep the camber from changing on its own. Move it in, then use the stock UCA bushing to get your adjustment.
Well, the car only weighs about 3000lbs. I'm running a set of Sprint lowering springs front and rear and there are no perches for the MK8 LCAs I'm running other than the poly spring isolators. I've also cut half a coil off the rear. When we did the alignment last summer the most we were able to squeeze out was -1 degrees. This is not a street car so tire wear and the like isn't something that is a concern.
 

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EDIT: You said 10", lol.

Ok, I need the length of one more line.
Either one.


The "opposite" side is 0.3825 inches; to do the math, I need the lengths of either other line.

10 inches is the length of the adjacent line, so

.3825/10=0.03825 ; INV TAN(0.03825) = 2.190 °

So, if you want the distance for say, 5 degrees, you do TAN(5°), which equals 0.087488 ; 0.087488*10"=0.87488" displacement.

See what I mean?
Trigonemetry made easy.png
 

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Pythagoras would be proud 😁.

If a spare UCA was had, could you just cut the outer attachment point off, very slightly shorten the arm itself at the angle desired and weld the attachment point back on?

So, 2πr would be the total circumference. 90°is 1/4 of that. If using the 10" as radius. 10*2*3.14=62.8/360= 0.1744" per degree.
Three degrees would be just over 1/2" @ 0.523". Two is 0.3488". So instead of using 10" if we had the exact measurements from midpoint of the hub to the midpoint of the UCA attachment, you could figure out how much to shorten the UCA.
 

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Discussion Starter #14
Thanks for all of the replies. Here is what I learned:
  • Yes, this could be done without a significant loss of safety
  • Moving the center line of the hole over by about 3/8" would give me an additional ~2 degrees or so.
  • Once the hole is elongated a washer should be welded over the new position to ensure that it stays where it's set.
Cool. Another project is in the works potentially.
 
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