Power Steering MK 3.1

[tparry]

First post so please bear with me. Just getting restarted on my build of one of the last 3.1 Roadsters - picked up 12/19/2009. Had installed AGR PS rack from Summit for '87-'93 Mustang (15:1). Now that I'm really getting serious I find I have a couple of problems. Installed extenders and now inner tie rods are way too long. Looks like I need to cut both inner and outer tie rods to make it work. Pivot point on inner tie rod is between 1 and 2 inched outboard of LCA - is that OK? Also input to PS rack is round with a flat spot - not the trapazoidal shape that FF offers to adapt steering shaft. Is there an adapter I can buy? Reading a number of post it appears I should have bought a slower rack that fits later model mustangs. Any suggestions on where I go from here?

[lilnuke]

With the rack centered, the inner tie-rod pivot point should be approximately the same as the LCA pivot. You may need to remove the extenders, some do not need them.

I had to cut the inner tie-rods about an inch to fit with the extenders installed.

FFR sells the correct adapter to mate the steering shaft and the power rack.

[JKleiner]

Without adapters the steering shaft is already configured for the '87-'93 PS rack with a 3/4" 36 spline coupling. You install the adapters to mate it to a manual or SN95 rack. Complete kits were/are shipped with the 9/16" 24 adapter installed---remove it and you should be able to couple your shaft to the power rack.

Jeff

[tparry]

Thanks! That's good news on the steering shaft. Will have to do some more accurate measurements with and without extenders. As is I do need about an inch to not bottom out on the outer tie rod but then it looks like I would be at the end of the inner rod threads with no room for adjustment. As I understand then the determinate on extenders is getting the same pivot point as the LCA. Thanks again both of you.

[nosniborf]

Well, it's not exactly correct to say "With the rack centered, the inner tie-rod pivot point should be approximately the same as the LCA pivot"
Actually, the inner tie rod pivot should be along an imaginary line drawn from the UCA pivot down to the LCA pivot as in the attached diagram.
For a better explanation see:
Longacre Racing Online -- Tech Article "Bump Steer "

[tparry]

Look at my set up. Forgot to mention I have the SAI mod. With that set up the inner control arm pivot point is in that imaginary line between upper and lower CA pivot points. I also have the centering mount from breeze. Given that the inner steering rod pivot point is still about 2 inches above LCA pivot point. Don't know how I could change that substantially. I'm now thinking to go ahead and cut inner rod about an inch and wait to see if I need to cut outer tie rod after I get engine and ride hieght set. What do you think?

[nosniborf]

I've been doing a lot of research in advance of a winter project to convert my MK3 over to power steering. I will be installing a SAI mod along with a rack and offset bushings from Breeze.
There are lots of posts on this site that cover various aspects of this conversion, but in short, if you have SN95 spindles it's very likely you will have to shorten the inner tie rods. I wouldn't plan on shortening the outers. If you mock it up you should be able to do it one time only.

[JKleiner]

Originally Posted by nosniborf

Actually, the inner tie rod pivot should be along an imaginary line drawn from the UCA pivot down to the LCA pivot...

Correct. In our cars it winds up like this



When the extenders are installed you need to either shorten the threaded end of the inner tie rod by the length of the extenders (approximately 1 1/2") or use an outer tie rod that is shorter by a like amount. Most opt to cut the inners but before you do assure that you will have enough threads remaining; not all manufacturers/rebuilders thread the inners the same distance from the outside end.

Good luck,
Jeff

[tparry]

Thanks again - I think I now have a much better undertanding of issue and a plan ahead. By the way the FFR supplied Steering column coupler does fit my steering rack. On to the next problem - panels.

[CHOTIS BILL]

Having the inside pivot points in a straight line is only half the puzzle. Having the outside pivot points in line is also important. With both set of points aligned it is just a matter of setting the steering rod to the correct angle by shimming the steering rod where it bolds to the steering arm. With mine I had to turn the steering arm so the dog leg pointed toward the center line of the car to get the outer steering pivot point in line with the outer control arm ball joints. The angle of the steering arm in more sensitive than it’s length. A very small change in the steering rod angle will make a very large change in bump steer where as you need to change the steering rod length quit a bit to make much difference in the bump steer. I am running a power steering rack from Breeze with the rack extenders and offset bushings. I have the FFR two piece spindles with the steering arms mounted with the dog legs to the inside and have adjusted the steering angle so that I have less than .010” bump steer in +/- 2” of wheel travel. With the steering arms mounted with the dog leg to the outside the bump steer was about +/- 3/16 in the same 2” of wheel travel.

Bill Lomenick

[CrawleysCobra]

I cut them a little at a time. Checking after each cut. I ended up cutting my inner rods by 1 1/8"... Just right for my set up.

[rich grsc]

Originally Posted by JKleiner

Correct. In our cars it winds up like this



When the extenders are installed you need to either shorten the threaded end of the inner tie rod by the length of the extenders (approximately 1 1/2") or use an outer tie rod that is shorter by a like amount. Most opt to cut the inners but before you do assure that you will have enough threads remaining; not all manufacturers/rebuilders thread the inners the same distance from the outside end.

Good luck,
Jeff

Jeff, question for you to ponder. My current build is a Mrk III with power steering being added, SN 95 spindles, pin drive width. Without the adapters the pivot is about 3/4" inside of your line, with the adapters, it is 3/4" outside of the line. So, seeing as the adapters are 1.5", 1" being ideal, I guess not installing them would be the way to go? Which side of the line would be better? Right now the plan is to leave it as is and see if I have an issue when I get it on the road.

[CHOTIS BILL]

If you have the steering arm dog leg to the outside I would use the 1.5” extenders and check you bump steer both above and below where the lower control arm is horizontal and then shim between where steering arm and tie rod bolt together until the bump steer is equal both up and down. If the bumps steer is too much you will need to change the length of the tie rod. It is important to get the length and angle of the tie rod correct but the pivots don’t need to line up it is just quick way to see if you are in the ball park.

Bill Lomenick