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Fixing bump steer on simple Mustang GT rack instal |
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304-dude
AMC Addicted Joined: Sep/29/2008 Location: Central Illinoi Status: Offline Points: 9082 |
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Posted: Aug/21/2019 at 8:36am |
Here is a product by Speedway for correcting tie rod end pivot points. They seem to be of near proper length to correct bump steer on 68 on up AMC cars with home brew Mustang GT rack installs.
Here the info from my recent addition to my thread... Most likely you will need to obtain a tie rod spacer adapter kit for Mustang rack installs. It may be a bit longer than needed, so cutting some of the straight bar between coupling ends will be needed, before welding the two couplers together. Once the adapter spacer has been shortened, it will allow proper bump steer on a simple rack install using original tie rods for the rack unit... Unless you prefer to mega mod, and do the truck tie rod mod that I have done. Here is a link... https://www.speedwaymotors.com/Inner-Tie-Rod-Extention-Kit-Speedway-Mustang-II-Manual-Rack,8066.html The image shows two couplers connected, and gives the impression only one is supplied. |
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71 Javelin SST body
390 69 crank, 70 block & heads NASCAR SB2 rods & pistons 78 Jeep TH400 w/ 2.76 Low 50/50 Ford-AMC Suspension 79 F150 rear & 8.8 axles Ford Racing 3.25 gears & 9" /w Detroit locker |
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farna
Supporter of TheAMCForum Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19686 |
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The kits has two extenders, one for each end of the rack. The rack is usually centered, so you would use two. It doesn't have to be though! In a custom install you can offset the rack to the driver's side for easier connection to the column and use a coupler/extension on just the passenger side end. I wouldn't go too far out, but a couple inches wouldn't hurt. The two extensions are shown connected, but that's just for shipping.
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Frank Swygert
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304-dude
AMC Addicted Joined: Sep/29/2008 Location: Central Illinoi Status: Offline Points: 9082 |
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Good explanation... though, you do want to center the rack as well as possible. Too far to one side, will effect bump steer, since the rotational centers of tie rod joints, at the rack ends are too unevenly matched. The shorter side will be effected most, and cause severe bump steer, if not checked. I think dirt setups can be less effected, by the offset, due to loaded suspension rotating deeper on the longer side, going into the turn. |
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71 Javelin SST body
390 69 crank, 70 block & heads NASCAR SB2 rods & pistons 78 Jeep TH400 w/ 2.76 Low 50/50 Ford-AMC Suspension 79 F150 rear & 8.8 axles Ford Racing 3.25 gears & 9" /w Detroit locker |
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Lucas660
AMC Addicted Joined: Apr/16/2012 Location: Vic, Australia Status: Offline Points: 1344 |
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The major cause of bump steer is the rack end (inner tie rod) not lining up with the lower control arm pivot. The closer the better here as the rack end will operate in the same plane as the lower control arm.
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billd
Moderator Group Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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Yup because the swing of the arm pulls the wheel in or out if the inner tie rod pivots in a different place. On stock suspension it's a reason the inner tie rod hits the drag link really close to the lower arm pivot point. |
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farna
Supporter of TheAMCForum Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19686 |
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"short and long ends" of the rack should make no difference. The rack moves to the left and right the same distance from center. If the rack is installed with the left and right ends near the lower control arm pivot point (both horizontally and vertically) whether it's offset or centered doesn't matter. I wouldn't use more than a 2" extension on one end simply because of the added leverage on that end. Probably wouldn't make a difference, but there is some additional leverage when the tire on that side hits a pot hole or curb. The further out you go the higher the chance of bending something or snapping the stud on the extension. The outer tie rod end must also be PARALLEL to the lower control arm. THAT is a big cause of bump steer! If the outer tie rod doesn't move in the same plane as the lower control arm the tires will steer with bumps -- hence "bump steer". If the drag link or rack ends aren't on a level with the inner control arm pivots the outer end height must be changed. That's why you see bump steer "eliminators". They are usually heim joints that replace the outer tie rod end along with a bolt and spacer kit to change the height (angle) of the outer tie rod to more closely match the lower arm angle. Note that you can have a little bump steer and never know it -- it's only when it gets to be severe that it's a problem.
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Frank Swygert
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304-dude
AMC Addicted Joined: Sep/29/2008 Location: Central Illinoi Status: Offline Points: 9082 |
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Farna, not to argue bump steer being noticable, but in respect to different radius between tie rod and LCA, no matter if parallel or not... bump steer will happen, depending on level of mismatched offset of tie rod lengths. Both parallelism and pivot placement in relation to LCA. Not everyone can have true parallelism nor matching distances at rack end pivots with LCA. Mixing two off positions with an offset tie rod length, will compound the bump steer being more noticable on the short end of the rack offset.
Not to say your wrong in thinking, just there have been lots and lots of methods on setting up steering, that has been mixed through the years that have worked well, even being counter dictory to practical methods. For some interesting details in various methods with steering setups, this pdf may enlighten some if pondering what works for difficult installations, best practice or not. http://www.woodwardsteering.com/PDF/tech%20section%20guide.pdf |
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71 Javelin SST body
390 69 crank, 70 block & heads NASCAR SB2 rods & pistons 78 Jeep TH400 w/ 2.76 Low 50/50 Ford-AMC Suspension 79 F150 rear & 8.8 axles Ford Racing 3.25 gears & 9" /w Detroit locker |
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Mopar_guy
Supporter of TheAMCForum Joined: Jun/07/2009 Location: Ohio Status: Offline Points: 4837 |
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Farna is correct. Look at these pictures and you'll see the rack is offset to the left by 2" and there's one of those spacers on the right side. There's extended outer tie rod ends for the height difference. No bump steer at all. You might want to consider reading this book that Brent wrote. https://www.amazon.com/Hot-Rod-Chassis-How-Understand/dp/1929133707/ |
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"Hemilina" My 1973, 5.7 Hemi swapped Javelin |
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304-dude
AMC Addicted Joined: Sep/29/2008 Location: Central Illinoi Status: Offline Points: 9082 |
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Your setup clearly shows what I intended for my thread... the use of the rack to tie rod spacers. Some like you may need just one on the offset rack. My setup is centered, for personal preference, and requires equal sized spacers on both ends. Thus a possible need to shave or section down the spacer or spacers when compenating for length addition. I was more concerned about adding, how some installs may not have proper location set, for the rack end pivots on the tie rods, when offset has been part of the install. Thus the spacer kit being the topic, as to equalize or properly space the tie rods when needed. Seems that I may have made discussion split on two independent points on offset rack installs, when replying back to farna's comments. Edited by 304-dude - Aug/23/2019 at 9:50am |
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71 Javelin SST body
390 69 crank, 70 block & heads NASCAR SB2 rods & pistons 78 Jeep TH400 w/ 2.76 Low 50/50 Ford-AMC Suspension 79 F150 rear & 8.8 axles Ford Racing 3.25 gears & 9" /w Detroit locker |
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Lucas660
AMC Addicted Joined: Apr/16/2012 Location: Vic, Australia Status: Offline Points: 1344 |
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Are you cutting and welding the rack ends? It is highly illegal to do that in Australia and for good reason, in fact no part of the steering system can be welded. I am in the process of building a bolt in kit for right hand drive and am going through options for the rack ends and tie rod ends. Luckily the roadsafe catalog has lengths and thread details. |
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