shorten steering rack?

trctrdrvr · #1 (**permalink**) 12-31-2002, 10:24 AM

I put shorter A arms on the front of the car so that I could run Trigo's, now the rods on the rack are to long, do I just cut them to fit? I have plenty of threads. looking for expert opinion's before I screw up.

Thanks Mike

kountzecobra · #2 (**permalink**) 12-31-2002, 10:38 AM

Mike, you need to shorten the rack an equal amount. This will keep the steering geometry correct.

trctrdrvr · #3 (**permalink**) 12-31-2002, 10:49 AM

Thanks David, thats what I was thinking the new a-arms are 1" shorter so I will start by reducing each side by 1"

Thanks Mike

kountzecobra · #4 (**permalink**) 12-31-2002, 11:11 AM

Mike, I recently read an article in some magazine (Can't remember which one) and they used 1" shorter a-arms so they shortened rack by 1" each side and it worked well for them.

Bob Putnam · #5 (**permalink**) 12-31-2002, 11:37 AM

Wrong, wrong, wrong...

If the bump-steer was correct before, you should only have to shorten the tie-rods. The idea is to have the tie-rods follow the same radius arc as (a weighted average of) the upper and lower control arms. For a fairly good approximation, the inner tie-rod pivot should fall on an imaginary line between the upper and lower pivot axis.

kountzecobra · #6 (**permalink**) 12-31-2002, 11:44 AM

Bob, that's what we are talking about. Shortening the threaded ends on the rack. Or at least that's what I was trying to say.

Bob Putnam · #7 (**permalink**) 12-31-2002, 01:10 PM

Kountz,

You want to keep the same inner pivot point for the tie rod, so no modifications to the rack are needed. Only the tie rods need shortening.

kountzecobra · #8 (**permalink**) 12-31-2002, 01:39 PM

Bob, not to argue, but I assure you I am saying the same thing you are. Maybe I am not saying it as clearly as you. The inner pivots will not be changed, only the length of the tierod assemblies. Maybe I should have said "Shorten the outer threaded portion of the inner tierod ends where the outer tierod end screws on?" Most folks don't even know how to remove the inner tierod ends from a rack or have the correct tool.

trctrdrvr · #9 (**permalink**) 12-31-2002, 01:49 PM

David;Bob
I believe we are all on the same page, I thought I could fix the problem by just reducing the threaded rods by 1", but just wanted more input before I screwed up.

Thanks Mike

Jack21 · #10 (**permalink**) 12-31-2002, 02:02 PM

What Bob was trying to say was (I think), shortening the control arms for the sake of your wheel offset is not a good idea. You're taking a big gamble with the cars handling by offhandedly making this change. Modifying control arms, and tie rods is for suspension gurus, not us unwashed masses. Leave the suspension geometry alone, and modify the wheel offset to where you need it.

Go to the heidts.com web site and read their tech article (it is also in their catalog) about Mustang II front suspensions, "bump steer", and what not to modify unless you know what you're doing.

Can't say I'm any great fan of Fords engineering prowess, but primitive as it is, the MII front suspension does work.

That being said, there are some things that can, and some things that must be modified with the MII on a Cobra (or any other car it is adapted to).

Can modify. You can replace the strut rod with a strutrodless lower control arm. There are some good, and beefy conversion kits out there, and there are some that look like they will twist like spaghetti the first time you hit the brakes. Starting with a bare frame, it can be done easily as there is some welding to do. Retrofitting after the body is on is more difficult. The strut rod does make for a beefy, and well supported front suspension. The problem is not the strut rod itself, but the soft rubber OEM style strut rod bushing that allows the wheel to move up & down (which it's supposed to do), and also front and rearward (which it's not supposed to do, not on a Cobra anyway). Solution, use urethane strut rod bushings.

Must modify. The inside mounting of the upper control arm, clamps the the arm to the frame with bolts. Ford seems to think that the serrations on the underside of the arm will hold it firmly to the frame when aligned. Provided, of course, that you can get an alignment shop to do it for you. ($69 for several hours worth of work is not particularly profitable for the shop) The first bump I went over collapsed the arms to the inner edge of the slots.

Solution. Tom Beroth of www.bethania-garage.com makes a MII upper control arm bracket that lets the alignment shop set the alignment with shims (just like real cars - sentements to Ford engineering again, and re-engineering that SHOULD have been done by the kit maker). The alignment, once (and easily) set, stays put.

trctrdrvr · #11 (**permalink**) 12-31-2002, 02:30 PM

Jack
I got my new shorter A-arms from Shell Valley they traded my original one's out when I went with Trigo's.
I am running top and bottom tubular A-arms without the strut, my car has also been modified to set alighment with shims they come stock from Shell Valley that way.
I just wanted to see if I could cut 1" off of the threaded end of the rod or if I needed to go to a shorter rod , it seem's to come to the same conclusion either way.

Thanks again for your replys

Mike

Jon Miller · #12 (**permalink**) 12-31-2002, 07:29 PM

Hi Mike,
I've got the same problem that you do with the Trigo/Mustang II combo. I was going to go with the shorter arms, but now I'm leaning toward a complete front end change to Jag E-Type.(see Jag E-M conversion thread in shop talk)

I would be very interested in knowing how your car handles after the change before I start cutting and welding on my car.

Thanks!
-Jon

trctrdrvr · #13 (**permalink**) 12-31-2002, 07:48 PM

Jon
Sorry can not help you out at this time still in the building stages.
I bought the wheels from Jim Day, who also has a E-M, do you have the corvette rearend?
I decided to change my setup in mid stage due to the fact that I got such a good deal on the wheels, and that Dana at Shell Valley was willing to swap parts with me for just the cost of shipping.
I will let you know how everything works out.

Mike

trctrdrvr · #14 (**permalink**) 12-31-2002, 08:13 PM

Sorry Jon read your post on E-M front conversion,and I see that you have the jag rear, I've changed the arms on one side already and everthing looks good, but I only had to go 1" not 2". but the tires are now inside the fenderwells, I need to figure out what to do with the rear now.

Mike