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PostPosted: February 21, 2020, 12:54 am 
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The rack came with the unfinished frame I picked up. I cannot for the life of me tell if it's shortened based on pictures of a regular miata rack.

Mine's a manual so the powered ones look a bit bulkier.

Based on the flap disc marks on the housing I would say yes.. but from certain pictures I compare to, it does not look shortened.

It has tie rod extensions though but doesn't guarantee the rack is shortened.

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PostPosted: February 21, 2020, 1:46 am 
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Joined: December 24, 2007, 5:11 am
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Location: Seattle area
David,

I shortened my Miata rack but it was a powered rack. I can measure it if that would help.
However that does not look like a Miata rack. What year is from?

Attachment:
IMG_0235.jpg
IMG_0235.jpg [ 799.88 KiB | Viewed 1922 times ]


Compared to mine it doesn't look shortened. I'll measure mine tomorrow and get back to you.

Cheers,

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PostPosted: February 21, 2020, 2:00 am 
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benny_toe wrote:
David,

I shortened my Miata rack but it was a powered rack. I can measure it if that would help.
However that does not look like a Miata rack. What year is from?

Attachment:
IMG_0235.jpg


Compared to mine it doesn't look shortened. I'll measure mine tomorrow and get back to you.

Cheers,


Hi Larry,

Hmm you may be right actually. Now looking more carefully it doesn't look like a miata rack. The little shaft that comes (where it connects to the ujoint) seems shorter than a miata rack. And a miata rack has a smooth housing after the bushing where this one has a housing with ridges on it.

Interesting... I wonder where this rack came from

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PostPosted: February 21, 2020, 6:11 am 
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David,

Does not have to be a Miata. Just needs to be front steer, if you're using Miata spindles, and the tie rods can mate up. Could be a better choice anyway.

The only deal breaker would be if you are using Miata uprights and it's a rear steer.

Cheers,

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PostPosted: February 21, 2020, 6:15 am 
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benny_toe wrote:
David,

Does not have to be a Miata. Just needs to be front steer, if you're using Miata spindles, and the tie rods can mate up. Could be a better choice anyway.

The only deal breaker would be if you are using Miata uprights and it's a rear steer.

Cheers,


I'm having trouble identifying the make and model this came out of it. My method had been aimlessly googling random cars.


Is there a way to know if it's front or rear steer?

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PostPosted: February 21, 2020, 6:31 am 
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Turn the input shaft. If the rack moves the same direction it's a front steer. The pinion below the rack would also indicate front steer.

Taking a closer look at your photo the rack's teeth are facing up. That's not a good sign. Did you get Miata uprights in your box of pieces?

Hope this helps.

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PostPosted: February 21, 2020, 6:48 am 
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benny_toe wrote:
Turn the input shaft. If the rack moves the same direction it's a front steer. The pinion below the rack would also indicate front steer.

Taking a closer look at your photo the rack's teeth are facing up. That's not a good sign. Did you get Miata uprights in your box of pieces?

Hope this helps.

Thanks I'll give that a test tomorrow. The roller has Miata uprights on all 4 corners but there suspension isn't complete yet

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PostPosted: February 21, 2020, 12:35 pm 
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Location: Cornholio OR "Where the magic happens"
Flip it over and make it a right hand drive? 8)

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PostPosted: February 21, 2020, 5:23 pm 
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So after doing some more google-fu.. I have a S-chassis Nissan steering rack.

S13 Silvia 240sx... s14 s15.

From the looks of it, it looks depowered but not shortened. I was wondering why the housing was flap disc-ed clean but the rack was normal. They cut the power steering fittings on the housing, welded it and cleaned it up.

This rack is a rear steer rack. Didnt know front and rear steer until yesterday lol

So I go RHD or get a different rack.

The prev owner was setting it up for RHD so now it's all making sense. I didn't put 2 and 2 together.

This is the rack measurement below:
Image


Miata outer tie rods and 240sx tie rods interchange. But the inner tie rod does not. So if I decide to go RHD, I will have to switch to miata outer tie rods anyway.

I have chris gibb's book but can someone explain to me like I'm 5, how to properly measure the steering rack to see whether or not it needs to be cut? I'm going off of the 18" number I've seen on other miata build threads.

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PostPosted: February 21, 2020, 5:43 pm 
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I was going to ask why you didn't just ask the seller what the rack came from.

There are variables, but if the rack width falls between the distance between the left and right ucaps and the shorter distance between the left and right lcaps, your going to be fairly close, give or take a couple inches to the ideal width. The closer the outer tierod ball is to the lbj, the lower the rack will need to be but not the same distance to the lcap as the tie rod to the lbj.

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PostPosted: February 21, 2020, 6:59 pm 
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Location: Livermore, Calif.
I believe the below sketch is from Tanner's book, "How to Build a Cheap Sports Car" and is trying to show the design to prevent or minimize bump steer. By knowing where to locate the end of the steering rack with respect to the ends of the upper and lower control arms (inboard), you should be able to calculate the approximately length of the rack itself. 18" - 19" sounds about right.

Cheers,
Roy


Attachments:
Bump Steer.jpg
Bump Steer.jpg [ 21.51 KiB | Viewed 1844 times ]

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PostPosted: February 21, 2020, 7:11 pm 
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I asked the seller but havent gotten a response I think he's busy.


Ok perfect that's a good diagram. I'm looking for his book to buy. I guess it addresses this better

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PostPosted: February 21, 2020, 8:33 pm 
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Ok, given that this is rear steer, what would happen if I swapped the driver and passenger uprights and made it a rear steer lhd?

The uprights are just one rose joint on top and one on bottom.

Here's a miata upright. The top ball joint hole and bottom are basically vertical.

Image

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PostPosted: February 21, 2020, 11:05 pm 
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Location: Cornholio OR "Where the magic happens"
Swapping the spindles (uprights) side to side is a common thing, I have done that in the past, even with struts.

The only down side would be if the upright has trail built into it.

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PostPosted: February 21, 2020, 11:07 pm 
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Bent Wrench wrote:
Swapping the spindles (uprights) side to side is a common thing, I have done that in the past, even with struts.

The only down side would be if the upright has trail built into it.


Can you clarify what you mean by trail?


Does swapping the upright and going to a rear steer setup cause there Ackerman angle to essentially change to anti Ackerman?

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