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PostPosted: May 1, 2023, 11:14 pm 
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I have mostly finished the rear end of my car. Just to remind everybody that I'm using the NC MX-5 rear end w/crossmember. Using everything from the NC rear end.
This was easy to setup, since only the height I had to figure out, but the front is a whole new animal.
Specially that I don't know anything about suspensions.
I really need your help here, with pretty much everything.
I'm reading, watching Youtube videos and I'm still not clear on where to start.
I know, that the LCA has to be parallel to the ground, and "V"(A arm) parallel to the car's centerline.
I'm using the NC front knuckles, that are a bit weird, in a way that the lower ball joints are installed from the top down.
I'm not sure what should I use, for the chassis side, I would prefer adjustable bushings, since it will be a street car, but if you can convince me that the Heim joints are much better, I may go that route. Also I need help with thread size and hole size. I'm thinking about using 5/8-18 thread and 5/8" hole, or 1/2" is enough?
Tube would be 1" and .083" wall thickness, that sounds about right? Low carbon steel 1020 DOM is OK?
Kinetic(Jack) sells those lower control arms, but I personally I don't like how they look, specially that rectangular tube. Sorry Jack about that.
Most likely I will use his upper control arms, I like that design and how they look.
I'm thinking about using a piece of square tubing, as a bracket to the chassis side. Maybe something even thicker, than 1/16th wall thickness.
Another "issue" is that, I have purchased some earlier Miata ball joints, since the NC comes only with aluminum control arms with integrated ball joints. These(bottom ones) are angled downwards, which creates a bit of a challenge, on how to join it with the rest of the control arm.
Most likely, I will have to use the 2.5"x1" tube, but that tube is pointed downwards at an angle. Now that tube, at that angle has to be joining with the two round 1" tubes.
The upper ones are the recommended ES2407R ones. Another issues has arises with these(all 4), that I have already took care. The taper angles, and diameters don't match with each other. Knuckle holes are bigger and deeper, than the taper diameter and length of the ball joints.
I have machined taper sleeves as adapters. I have also machined a bit off from the top ball joint mount bottom part, where the nut goes.
I will be using weld in bungs in the tubes. Material for these matters? Can be mild steel/low carbon steel, or has to be 4130?
I have measured the knuckle and inserted in vsusp and I came up with this specs. First time I'm doing something like this.
As you can see, I need a lot of help. It would be much appreciated, any help or pointers that you guys can offer.
https://tinyurl.com/59fsfztr


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PostPosted: May 2, 2023, 7:43 am 
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Normally to select an LBJ or UBJ, the dimensions of the taper in the spindle is measured and reamed if needed to fit an appropriate joint with a known taper. Oem spindle balljoint tapers are not published, only tie rod tapers.

I don't know if that will be acceptable. The NA LBJ is designed to support the weight of the car in tension. The NC loads the LBJ in compression.

The obvious best choice is to use the NC arms and bushes with the NC spindles, but the chassis will stick out wider than the nose. A small price to pay for all the benefits. You may be able to use the NC rack and swaybar as-is.

Another option is to use NA spindles.

Fwiw, "inverted" LBJs are better for minimizing the scrub radius.

Mild steel is fine for inserts.

Tube angle is independent of balljoint angle. The balljoint should be in the center of travel at ride height to ensure it doesn't rock too far at full bump or droop and break or bend something.

Tubing selection is just one element to designing an arm but many have used that size.

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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12


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PostPosted: May 2, 2023, 11:14 am 
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The NA spindle has 4 studs, I have 5 studs. I would like to minimize using other car's parts, to make it simpler to service in the future.
Also, the NC ball joints come with the whole aluminum control arms, they are not replaceable.
What do you think about my vsusp numbers? It can't be good the first time around.
It took me a while, to get the taper sleeve adapters machined to the proper angles. Set the compound at an angle, that I have found online 7.15 for example and after machining the angle, I have used a marker on the tapered surface, and pushed in and twisted the ball joint over it. This showed me, in which way I have to adjust my compound angle on the lathe. I did this a few times, until I have seen scratched on the whole tapered surface. Spindle angle is different than the ball joint angle. I don't have the number in front of me, but it's bigger slightly, than the ball joint angle.
The issue with the NC steering rack(which I already have), it is to long. If I recall it correctly, it is 25". I will need to shorten it. I don't know how yet, but that is tomorros problem.
Thank you for your help.
I should start my own thread, right?

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PostPosted: May 2, 2023, 11:51 am 
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I am familiar with the NC arms. The NC arms and rack can be used by widening the chassis behind the nose. It was an option before the spindles were modified.

I suggest cutting the scrub radius by half and reducing the roll center movement (yellow) and height (blue).

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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12


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PostPosted: May 2, 2023, 5:59 pm 
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How would I do those?
I can't change the spindle angle, and I already have 8" wheels.
Track width of a car, is at the center of two wheels, right?

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PostPosted: May 2, 2023, 6:49 pm 
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For scrub, you could raise the UBJ a 1/2 inch by using a rebuildable, screw-in chrysler upper type joint for racing. They have different pin lengths and tapers available. A 1/2 inch would reduce the scrub to about 1/2 inch. You could also use a slightly larger od tire such as a 225-50-17 to reduce it down to almost nothing.

You can steady and lower the roll center by trading some camber gain, back and forth on the uca length and angle.

The track width is tire center to tire center.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12


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PostPosted: May 2, 2023, 7:00 pm 
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This one?
https://www.speedwaymotors.com/Speedway ... grEALw_wcB

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PostPosted: May 2, 2023, 7:11 pm 
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Yes, that type. It comes in different lengths and the depth of the fit into the spindle when you ream the hole is also a factor. A spherical upper is much easier to adjust with spacers.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12


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PostPosted: May 2, 2023, 10:33 pm 
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"reducing the roll center movement (yellow) and height (blue)"
The problem I'm having, is I don't know how it suppose to look like, and what I have to adjust to achieve these.
Track width is 59.375".
What angle should have the UCA? McSorley said that 13 degree?!
I have raised the top ball joint 1".
Lowered the chassis at the front, by .25".
How this looks?
https://tinyurl.com/bdft743t

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PostPosted: May 3, 2023, 4:47 am 
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:BH: Start over with your original dimensions and UBJ. Tweak based on those spindle dims:

7 SV tweak 05032023

Raising the UBJ makes the scrub worse and I entered the change in the wrong block. The "hub to upper balljoint X" dimension is horizontal, moving the UBJ toward the center of the car which would correct the scrub but would require cutting and welding on the spindles. The only practical way to correct or reduce scrub with your spindle dimensions is with bigger tires or more offset/back spacing.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12


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PostPosted: May 3, 2023, 11:07 am 
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You are correct, I have missed that too.
I don't understand the tire upsizing. If I change to wider tire, not much is changing.
Bigger offset, like ET60?
It seems like I may have to go with different spindles, since I already have ET40 wheels and 215 tires.
I just have to keep the 5x114.3 bolt pattern, I believe the Mustang IIs have that, right?

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PostPosted: May 3, 2023, 11:50 am 
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Research tire sizing math. A 225-50 has a larger diameter than a 215-50. You can enter a different size in vsusp and see the difference it makes in scrub.

A mustang II / pinto IFS could be used and comes in different bolt circles depending on the rotors but also has some scrub. However, the Mustang II is very common and straight forward. There are some vsusp links here where the builder used Mustang II so you could compare using your wheels. One thing to consider is the center hole and how much a mustang II rotor hub sticks out through the wheel.

There are many different spindles that have that bolt circle. Too late to use a NA irs and wheels or rear 4 lug adapters? Front 5 lug adapters would add scrub.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12


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PostPosted: May 3, 2023, 12:16 pm 
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We are shooting for 0 scrub radius, or a bit of negative scrub?
I fail to see much of a difference.
Please treat me as a first timer, I don't know anything about this stuff.
It is not too late to switch spindles, I only have one of each component, purchased only for testing.
If I add 2.4 offset to the wheel, then I have 0 scrub, that is what we want?

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PostPosted: May 3, 2023, 4:04 pm 
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Also, the measurement for the spindle wheel mounting surface, should be done with a disc on it, or without it?

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PostPosted: May 3, 2023, 4:34 pm 
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The measure is from the wheel mounting surface so yes, with the rotor.

What are these wheels from? Aftermarket? Why these wheels? Why a 215-50 on an eight inch wide rim? Do you already have these? The oem miata wheels and tire sizes are a much better choice with less scrub and unsprung weight.

The scrub radius is a lever acting on the steering that amplifies whatever surface the tire is rolling over. This feedback is felt through the steering wheel. This is in addition to the feedback lever based on tire width. Nobody wants an unstable car that needs both hands firmly on the wheel at all times to prevent a sudden turn from hitting a pot hole or running over a something. Up to a 1/2 inch scrub is generally considered tolerable but there are other variables.

I think the inverted NA LBJ is an issue long-term. The complete NC IFS subframe has all the suspension attachments so all you'd need to do is graft it in but it would not be as pretty plus you'd need to make rockers with inboard coilovers. Probably the most headache-free way to go.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12


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