Need some measurements

JayBar · #1 (**permalink**) 08-06-2007, 04:57 PM

I am thinking of adapting a Mustang power steering rack to my Backdraft. Not sure of the exact model. Was thinking about a 89-92 power rack. I had one laying around my garage for 4 years being left over from building my FFR. A few months ago it fell over and almost broke my toe so I threw it into the trash. Now I am wishing I hadn't been so hasty. I need to know some measurements. If anyone has one out of the car could you take a few measurements and post them for me I would appreciate it. I would like to know the "tip to tip" length i.e. from the threaded ends. Then the center to center dimension of the mounting points.
Thanks,

JayB

mickmate · #2 (**permalink**) 08-06-2007, 06:21 PM

Check the Flaming River website they give some useful dimensions.

JayBar · #3 (**permalink**) 08-07-2007, 05:04 AM

Thanks for the suggustion, but I could find no specs on there site.

CSCHWER · #4 (**permalink**) 08-07-2007, 06:21 AM

Call Backdraft and talk to Frank. They are just down the road from u.

strictlypersonl · #5 (**permalink**) 08-07-2007, 06:39 AM

In order for bump steer to be maintained, you must duplicate the distance between the inner tie-rod pivot points, not the tip-to-tip.

JayBar · #6 (**permalink**) 08-11-2007, 10:08 AM

Yea,I know about bump steer, I went through it with my Mustang Cobra when I lowered it.
I don't think I have to dublicate the inner pivot points. I just have to have the tie-rods parallel to the lower control arms.
I know Frank is down the road, but he has no reason to know the measurements of a Ford rack, as he uses a Toyota rack.
At this point I only want the "gross" numbers,i.e.mounting hole spacing and over all length from tip of rod to rod. 'though I can cut the rods if need be.

Rick Parker · #7 (**permalink**) 08-11-2007, 01:18 PM

Jay Bar:
When you lowered your Mustang you didn't change the rack, you moved it (hopefully) or put long spacers at the tie rod ends (bad). The distance between the inner pivots must be maintained and kept in an imaginary line between the upper and lower suspension pivots or it WILL affect the bumpsteer as previously stated, strictlypersonl is on the money, heed his warning . Shortening the tie rods does not correct the problem.

JayBar · #8 (**permalink**) 08-23-2007, 08:06 PM

After giving thought to the comments of Rick Parker and Stricklypersonal, I think their theories have merit. So I need the measurement of a Ford Rack, most likely 1989-1992 Mustang, (seems the most common year). I will need the measurement of the rack from beginning of boot to beginning of boot.
That should get me close to the actual pivot points.

Rick Parker · #9 (**permalink**) 08-23-2007, 08:45 PM

You need the dimension from the center of one tie rod pivot to the other. Then shorten the inner rack as needed. Then take the same length removed out of the tube that forms the rack housing. You will need access to a metal lathe or a machinist to do this correctly but it is not hard if you have the required dimensions. I did this on my car. Do not weld on the inner rack this will create an unsafe condition in a vital part of the car. The rack in this picture has been shortened about 4 inches. It is a rack from an Early MGB. You can visualize where the pivot end of the rack is inside the boot as it is in a line between the upper and lower pivots of the suspension arms. Consult someone that deals with Mustangs such as Griggs Racing in Sonoma (at Sears Point) as thay can help you plot your course. No room for error here.

JayBar · #10 (**permalink**) 08-23-2007, 08:53 PM

Or hopefully if I can get the Ford Mustang dimensions,which may be the same as my current Backdraft rack, then no machineing necessary.

JayBar · #11 (**permalink**) 08-25-2007, 06:37 PM

I happened to be in Books a Million yesterday. While my wife looked for something I went to the car section and found a book on Chassis design and building.
I took it to and easy chair and started reading. I looked up the section on steering and "bump steer". It confirms what you guys have been saying.

There was an illustration showing the line between the top control arm pivot and lower control arm pivot, and said the pivot of the tie rod must be in line with these two points.
That is great and would be easy for me to calculate except my car does not have an upper control arm. It is a strut. The book had no info on cars using struts instead of upper control arms. Any suggestions as to how I can come up with a "line" to show where to put the tie rod pivot?

nevermind65 · #12 (**permalink**) 08-25-2007, 06:43 PM

This is also a good site to get some info.

http://www.heidts.com/heisinfo.htm

I have a rack out of a 94. I think I have one from a 88 also. I'll measure them tomorrow if I get a chance.

mickmate · #13 (**permalink**) 08-25-2007, 06:48 PM

Now your into the good stuff on it. You'll see why approximate measurements won't do. Something as small as misalignment from a worn ball joint makes the steering much heavier because of the critical nature of alignment. I believe a strut line can be drawn down through the centre of the strut, I'll look in one of my books from Steve Smith.

RICK LAKE · #14 (**permalink**) 08-26-2007, 06:04 AM

JayBar You might want to look at Sweet or Appleton Racks. They come in different ratios for turning and are Power assist. I have one in my ERA cobra. Only the second ERA built with a Sweet rack. Works great in the car. Make sure you have the correct ackerman angles on the front end for turning. Strictlypersonal is the one who setup my car for the swap from Suburu. Look in the dirt track mags or google Appleton. Add and steering cooler to the system. 8 years and no problems with mine.