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Steering rack dimensions
brewil - 25/9/18 at 11:17 AM

Hi Everyone,

I am rebuilding an old car with a custom tubular coil-over suspension.
I live in South Africa so the car is RHD. Going with a manual rack but PAS is also an option.

The issue I am having is that the LCA's centre to centre is 622mm apart and I am looking for a rack that fits this is it will be inline. It has to be this way and can't be changed. The system I am using is based on the Mustang II rack and pinion.

I know that the Escort is 615mm between the centre of the inner tie rod pivots so it's too short.
Does anyone have measurements on the Sierra/Sapphire or Granada racks?
I've called up the businesses selling these racks but no one has the measurements.

Any help is greatly appreciated.

Thanks,

Brett
Cape Town, South Africa

[Edited on 25/9/18 by brewil]

brewil - 25/9/18 at 02:29 PM

Anyone?

Angel Acevedo - 25/9/18 at 03:54 PM

Brewil.
3.5 mm per side difference will give you some bump steering, but I donīt think it will be noticeable unless you are very exigent driver...
Hope this helps.
Angel Acevedo

brewil - 25/9/18 at 07:14 PM

Thanks, this will be a street car using a 500hp 4.3l straight six. Also, it's around 3000lbs so any info or advice regarding the strength of the rack is welcome.

Any idea's on the Granada or Sapphire/Sierra racks dimensions anyone?

[Edited on 25/9/18 by brewil]

ettore bugatti - 25/9/18 at 07:22 PM

Why not use a Mustang II steering rack too?

brewil - 25/9/18 at 07:39 PM

It's left hand drive. I need RHD

AdamR20 - 25/9/18 at 07:55 PM

What's your upper control arm CtoC? That is also important. Should be more than 622 by a significant chunk?

Depends on your steering layout but it's unlikely 622 would be suitable, 615 might even work well.

https://goo.gl/images/KjVgeH

I think a Miata rack is about 635mm, could be one to look at.



[Edited on 25/9/18 by AdamR20]

brewil - 25/9/18 at 11:14 PM

The rack is directly in-line with the LCA which is the design of the system and the LCA's are 622mm apart.
The geometry has been worked out. The issue is that the system was designed with an available left-hand rack.
The designer was nice enough the help me build my own on the same platform but we didn't think there wouldn't be a RHD rack available.

AdamR20 - 26/9/18 at 07:44 AM

Would be keen to see the workings out of this geometry.

Mr Whippy - 26/9/18 at 11:45 AM

on this forum it seems the Sierra 4x4 or cosworth uses the same rack

linky

brewil - 26/9/18 at 02:21 PM

thanks Mr Whippy

I'd post an image of the suspension but I can only post image links it seems.

So here's a link to the builder who has been helping me:

http://gerstsuspensions.com/products/front-suspension/

http://gerstsuspensions.com/wp-content/uploads/2017/02/Carl-Gerst-QT4A9113white-1.jpg

brewil - 26/9/18 at 02:32 PM

I'm assuming a stock Sierra/Sapphire manual rack has the same dimensions just different ratios.
The mounts don't matter as I will make custom mounting points to fit.

AdamR20 - 26/9/18 at 02:35 PM

Looks like it will have a fair chunk of toe out bump steer if the rack is the same width as the LCA centres? (Assuming 100% Ackerman, hard to tell from the photos)

[Edited on 26/9/18 by AdamR20]

brewil - 26/9/18 at 02:43 PM

The centreline of the rack is directly in-inline with the centreline of the LCA pivot point so Instant Centre is normal.

Would the Heim joint at the spindle not assist??

http://photobucket.com/gallery/http://s183.photobucket.com/user/dukeboy_318/media/dart/12431191_10203804569795085_549239434_n_zpsxgmo3szi.jpg.html

brewil - 26/9/18 at 02:46 PM

More install pics - scroll down

https://www.forabodiesonly.com/mopar/threads/gts-install-write-up-and-review-lots-of-pics.335465/

He's used Ron Suttons suspension geometry software to get everything right. Apparently zero bumpsteer.
Ackermann is something else. Impossible to get exact with Mustang II spindles

brewil - 26/9/18 at 02:49 PM

Here's the spindle I am using

https://www.wilwood.com/Images/Steering/Steering_Drawings-Large/spindle_830-9807-dwg-lg.jpg

AdamR20 - 26/9/18 at 02:55 PM

quote:
Originally posted by brewil
Ackermann is something else.


Indeed it is something different, but it is related.

Good luck with your search for the rack you want to use.

[Edited on 26/9/18 by AdamR20]

brewil - 26/9/18 at 03:12 PM

I'm going on his Ackermann readings and they seem to be correct.

Any ideas about the bumpstop when you look at the knuckle/spindle?

The LCA pivot points are 622mm apart
The rack will lie directly in-line with the LCA pivot points

Angel Acevedo - 26/9/18 at 03:15 PM

quote:
Originally posted by brewil
Thanks, this will be a street car using a 500hp 4.3l straight six. Also, it's around 3000lbs so any info or advice regarding the strength of the rack is welcome.

Any idea's on the Granada or Sapphire/Sierra racks dimensions anyone?

[Edited on 25/9/18 by brewil]


For a street car some bump steer may be OK. 3000 lb is not too much above a Miata weight (2300 - 2400lb approx)
Iīd be concerned if the streets were very rough and I woould be driving very high speeds.

Regarding dimensions, I donīt have any, but a quick look in Google may give you some data.


quote:
Originally posted by brewil
Here's the spindle I am using

https://www.wilwood.com/Images/Steering/Steering_Drawings-Large/spindle_830-9807-dwg-lg.jpg


If you are dead set on Absolute zero bump steering, there are several ways to achieve that.
And, if I get it right, your spindles have bolt-on steering arms, that opens uo the possibility of fabricating a custom steering arm to elliminate Bump Steer

Angel Acevedo - 26/9/18 at 03:25 PM

quote:
Originally posted by brewil

The rack will lie directly in-line with the LCA pivot points


The rack does not need to be in line... And judging from your Spindle image, If you have the Rack ends exactly in line with the LCA Pivots, the outer end (TRE) will lay above the Lower Ball Joint giving some Bump Steer. This may or may not be noticeable on a street car. Depends on how sensible you are to it.
The pivots mut keep a relationship throughout the whole range of travel of the suspension.
See link for detailed procedure.
http://www.longacreracing.com/technical-articles.aspx?item=8162

brewil - 26/9/18 at 03:42 PM

The outer tie rod (with a heim joint at the end) is directly in line with the Lower Control Arm and balljoint - it has a spacer between the heim joint and the spindle steering arm to keep it at the same angle as the LCA.

The only issue I see is that the steering arm is not vertically inline with the balljoint

Ok so these images might give a better understanding.

https://www.facebook.com/photo.php?fbid=1574144412884928&set=g.923587124369412&type=1&ifg=1

https://www.facebook.com/photo.php?fbid=1706872512665368&set=pcb.1542248085836643&type=3&theater

https://www.facebook.com/photo.php?fbid=10205914601064548&set=g.923587124369412&type=1&ifg=1



BTW I really appreciate the feedback and help

Angel Acevedo - 26/9/18 at 04:04 PM

quote:
Originally posted by brewil
The outer tie rod (with a heim joint at the end) is directly in line with the Lower Control Arm and balljoint - it has a spacer between the heim joint and the spindle steering arm to keep it at the same angle as the LCA.

This is to bring Track Rod to parallel with the Lower Control Arm, this spagcer needs to be adjusted in size in order to achieve "perfection as per the diagram pictured at the bottom of the link in my previous post.


The only issue I see is that the steering arm is not vertically inline with the balljoint



If you refer to the misalignment you "see" when viewing from the front of the car, this is closely related with Ackermann and although it may have an impact in bump steer, it will be negligible once bump steer has been corrected on static Ride Height.






BTW I really appreciate the feedback and help

Hope this helps.

brewil - 27/9/18 at 12:20 PM

Looks like the Sierra rack is over 700mm balljoint to balljoint

This search is becoming ridiculous. It's been 3 months now

Angel Acevedo - 27/9/18 at 01:48 PM

Have you tried to get a Rack from a LHD Rear Steer equipped car?
These might be installed upside down as RHD.

brewil - 27/9/18 at 01:50 PM

Seems like there are none.

My best bet might be t cut the rack of the Sierra down

Angel Acevedo - 27/9/18 at 02:43 PM

quote:
Originally posted by brewil
Seems like there are none.



My best bet might be t cut the rack of the Sierra down



As rear steer I refer to those cars that have the Steering Rack behind the front axle line.

I will be cutting my mustang Rack 4 inches total, but thatīs two FULL inches per side.
As stated in my first post , 3.5 mm difference per side will produce negligible Bump Steer.
Iīd install that and drive the car.
If not acceptable, then Cut it.

Another solution may be Shortening your rack (one end only) and manufacturing an extension for said end to regain what you need to get the desired len
gth.

[Edited on 9/27/2018 by Angel Acevedo]