LocostUSA.com

As title shows, I'm about to setup my steering. Control arm brackets, and control arms are all tacked in.
I need to shorten the rack, already depowered it and cut it in two. It is an NC MX-5 rack.
The spindles are for an NA and already have NC tie rods(purchased them in advance for the NC spindles, but switched to NA due to wrong scrub radius), which look different than the NA onse. Not sure if that matters.
The NC onse look like straight tie rods, while the NA looks more like a hook shape tie rod.
vsusp shows 20.472" rack width, and 3.146" rack height.
Should I just cut the rack(housing only and cut the end of the actual rack rod and re-thread it) to have this dimension at the inner tie rod ball centers, and make a mount for the rack, and all should be good to go(most likely not)?
What should be the alignment of the rack, compared to the outer tie rod mount to the spindle, looking from above. Should be inline?
Any input, where should I start would be appreciated.

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Tibor


'20 Alfa Romeo Stelvio daily
Locost/442E in progress

The hook na tierods maximize "misalignment" range when the tierods mount below the arms and the rack is at na miata height.

Because the lower control arms forward link taper rearward in the overhead view, the rack cannot be mounted at the miata height. This reduces the available "misalignment" range of the outer tierod (i.e. bump and droop travel without bind at the tierod). An nc tierod would reduce this further if bottom mounted.

Most likely, for a higher rack mounting, you will need to flip the tierods by drilling the taper from the top and use the nc tierod. Another option is to drill the taper to fit bolts and standard sphericals or tapered inserts you could make with no drilling of the spindle arm.

Confirm the rack width needed with a jig representing the inner tie rod joints and check for bump steer.
For a percentage of ackermann, the rack should be behind a centerline between the outer tierods.

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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

What about shortening the arms to increase the ratio?
Or is the Miata rack quick enough?

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Honey anyone?

It is something around 2.75 turns end to end. I have already cut it and modified it. The only thing is left, is the outer tube modification.
Control arms are done as well.

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Tibor


'20 Alfa Romeo Stelvio daily
Locost/442E in progress

To do the bump steer alignment, after the rack is installed, the wheels should be aligned right?

_________________
Tibor


'20 Alfa Romeo Stelvio daily
Locost/442E in progress

Bumpsteer check determines rack mounting height if not the rack width. The wheel being checked needs to be parallel to the chassis. You could setup a piece of cardboard, flat facing the front and about six inches wide and set vertical in the side view, between the ucap and lcap in the front view. Attach a string to a pen near the tip and the tie rod pivot center with a bolt small enough to fit through the tappered hole and washers or nuts to position the string at the right height. Set to ride height, then swing the pen across the cardboard, making an arc. Lift the suspension to full bump and swing again, making a new arc. The rack height should be where the arcs intersect. This gets you in the vertical ball park to be checked again with actual tie rods and steering components before final welding the rack mount.

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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

The rack width and height location, is not what vsusp shows?

_________________
Tibor


'20 Alfa Romeo Stelvio daily
Locost/442E in progress

There are tolerances that can stack in measuring for vsusp input, machining, and fabricating. Check it before final welding the rack mount.

_________________
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

Sorry, but I'm having a hard time picturing your description, on how to do it.
I have another question, the front and aft location of the rack, is important? Should be at the same axis as the outer tie rod ball?

_________________
Tibor


'20 Alfa Romeo Stelvio daily
Locost/442E in progress

The rack should be mounted slightly behind a line drawn through the end of the steering arms on a front steer.
This provides a needed amount of ackermann

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Honey anyone?

Thanks.
How can I check my Ackerman angle? I know that is the line from the steering arm hole center to the center of the diff. The diff is not even on the center of the axle.

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Tibor


'20 Alfa Romeo Stelvio daily
Locost/442E in progress

A 30 foot circle with a 95.5 wheel base (don't know what your wheel base is) should be about 28 deg on the outside wheel, and with a 58 inch track(?) should be about 38 degrees on the inside with ackermann.

It's a right triangle using the radius of the desired turning circle and wheelbase to find the angles, then subtract from 90 deg.

Toe would be adjusted with the rack temporarily mounted for testing fore-aft position, then the steering turned to the required outside wheel angle. The inside wheel angle is checked to see how close you are and which way you want to go but the amount is not as important as bump steer.

If using the rear axle, it is the center of the axle rotating axis, not the diff and setting steering arm angles, not rack fore-aft position.

_________________
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

Track width is 59.375", wheel base I need to measure.

_________________
Tibor


'20 Alfa Romeo Stelvio daily
Locost/442E in progress

What I did was to attach a laser level to the brake rotor, pointing to the wall. I moved the upright through it's range of motion, marking the high and low spots on the wall. I experimented with the steering rack location, until the high and low spots were exactly perpendicular to each other. This shows that there is no bump steer through the range of motion. Mount the rack there, and you'll be golden.
cheers
Doug

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book 4AGE build, Supra W58 transmission, Corolla GTS live axle

Like this?
https://www.youtube.com/watch?v=dXLgh-jkwT4&t=1803s

_________________
Tibor


'20 Alfa Romeo Stelvio daily
Locost/442E in progress