XR4Ti Archived Tech Articles
Post Date: Fri, 17 Apr 1998 Subject: $5 rear shock tower brace - XR4Ti Unbraced list members, I have an experience to share. One that I know others have talked about, but I thought I'd add my two pennies on the subject... This last Monday, Jeff Jackson (firstname.lastname@example.org) drove up to Dayton from Cincy for a work related training event. He let me know about it and we got together. His XR is a late 89, with a T-5, lowered with Eibach's and RS adjustables, cossie front bumper and grille, all OEM Ford pieces, mono-red, looks nice. He also had the Slocum design rear brace for the shocks. Anyway we went tooling around in it (I drove it) so I could see how the suspension felt lowered. He put the fronts on full hard and I loved it! This is where it gets interesting... I am pretty familiar with how my 87 XR4 feels when pushed to the limits. I have autocrossed it, done illegal things in it (insert standard disclaimer here), and basically darn near discovered the cars handling *limits*. I have good tires, too. Yoko AVS's, nice and shaved. The car sticks good, and I know how the shell of the car responds during corners... I *know* my car... Jeff let me push his XR a bit in some local parking lots (he didn't flip out the way I was tossing his car around, great guy!). Well, having NOT driven his car before the shock tower brace was installed, I can say that I CAN tell the difference between the way his behaved and mine behaved, beyond the level of the springs and dampers. To describe: Jeff's XR4Ti - the rear suspension had a one-ness to it (great for you Zen- masters...), no feeling of independent movement, just connected movement. My XR4Ti - I didn't notice until I drove Jeff's XR4Ti how truely our cars have an *independent rear suspension*, it feels as though there are two separate units in the rear. The truth is, you never can experience what I am describing without putting the brace in. Quotes from the XR4Ti suspension masters: "The front brace was noticable, but adding the rear brace made a night and day difference". - From a discussion at the Carlisle 97 M-O banquet "Just by moving one end of the brace with two fingers, there was 3/16th's of an inch of play visible at the shock tower that the brace was attached to". - From a list member/autocrosser (note: quotes were paraphased, qualifying them as non-quotes...) My advice: Grab a cup of Java or ActiveX and point your browser here: http://home.pacbell.net/aslocum/ Look for the link to the Merkur Encyclopedia, and seek info on the shock tower brace... Am I getting reimbursed for my endorsement? Sure, I can make a brace too!!! (insert standard disclaimer here) ---------- Post Date: Sun, 19 Apr 1998 Subject: $5 rear shock tower brace INSTALLATION - XR4Ti Unbraced list members, This is part two of my rear shock tower brace adventure. As I mentioned a few days ago, I drove Jeff Jackson's lowered and rear shock tower brace equipped XR4Ti. I was very impressed with how it handled. On to present info: Yesterday I purchased an angle iron that measured 1/8" x 1 1/4"x 1 1/4" x 48" for $6.05 from my local Furrow. It is plain, untreated steel. Sears Hardware has galvanzied angle iron for about $0.75 more for the same size. I would have gotten that, but they were out of stock, the next useable size being 60" and costing twice as much. Not worth it. Parts, tools, and equipment: - angle iron, 1/8" x 1 1/4"x 1 1/4" x 48" - $6.05 - dremel tool (cutting, sanding, grinding bits) - 1/2 chuck drill (variable speed) - 25/64 drill bit (13/32 is the correct size, but Sears didn't have it in stock) - $4.36 - phillips screw driver - 17mm socket wrench - 17mm box end wrench - *clicker* torque wrench - dark primer and black paint - about $7.00 and plenty left on both cans - two slightly smaller and much shorter bolts used to center shocks - small pocket knife - some scotch tape - the Dead Sea Scrolls I followed Allan Slocums dimensions from the Merkur Encyclopedia to build the bar. http://home.pacbell.net/aslocum/ - Click the link to the Merkur Encyclopedia I gave the bar a nice wire brushing, sanding, and paint job to prevent surface rust (since it isn't galvanized). Since I didn't buy the correct size drill bit I had to slightly enlarge the holes to the required 0.400" (from the 0.390625" hole I made) I found a few areas where the rough edges of the design can be smoothed over. These aren't required but help improve the appearance (not that you see it once in the car) and fit and finish of the bar. These will come later on. How to install the rear shock tower brace: - Remove the rear parcel shelf from the car. I found it easier to fold the seats forward, too. - Remove the plastic trim covering the shock tower bolts (two phillips screws per side). - Remove the Nylock nuts from the bolts, being careful not to drop them behind the trim panel (it's a pain to take it out to recover a dropped nut or bolt). Get out of the trunk if you climbed in. You want the shocks to remain as much as possible in the original position. - Jeff noted that installing his brace with the Koni RS adjustables became difficult when he compressed the shocks by getting in the car. The rebound damping kept them from extending when he got out of the trunk. My stock shocks didn't have that problem. More in the next bullet point. - Remove the bolt from the shock. My stock shocks wanted to extend. No biggie. I just stuck a phillips screw driver in the hole (from the front side of the tower) to realign the shock with the hole. - With the screw driver holding the shock into position, I stuck a smaller bolt in the shock from the rear of the tower to keep it generally aligned for later. - Next I installed the bolts in the brace, holding them in position with the scotch tape. - I laid the bar in it's approximate position so I could trim the carpet panel to allow the brace to be in place. - I used the pocket knife (a utility knife would have been better) to make two vertical cuts in the carpeted trim piece. I didn't cut any lower than the impression made by the plastic panel in the carpet. Am I clear on this? - I didn't cut a notch out, rather I separated the carpet from it's backing, folded the carpet in towards the trunk space and the backing toward the tower. This way I can return it close to stock if need be. - Next I put the bolts into the shock tower holes and the shock. I did one end at a time. The smaller bolt held the shock generally in place and I jounced the car with my body weight until (I was in the car) the alignment was perfect just long enough for the bolt to slide it. Unfortunately, the bolt jumped in so quickly that the smaller bolt jumped out the back and down behind the panel. DOH!!! - Repeat this step for both ends. - Install the Nylock nuts on the ends of the bolts and turn it. - Torque the bolt to 30-37 lb-ft. You have to trim the shock tower plastic cover panel to get it to fit over the brace. I am not *down with that* as I don't have decent replacements now, so I left them off for the present time. For my improvements on the design: - I'd round off the ends on the surface that bolts to the tower. It seems like it would conform to the shape a bit better. My dremel isn't up to the task and I have no bench grinder. - Install a washer between the bolt head and the brace. The OEM bolt may not be long enough to reach the Nylock part of the nut with a washer in there. But replacement bolts are cheap and they are a standard cad plating. My supplier just isn't in on Saturdays. - The reason for adding the washer? The surface that the bolt head meets up with is different with the brace than with the tower itself. This might have an effect on the torque when you apply it. You may be wasting torque on the friction between the bolt head and the brace. The results: Not only does the car feel more solid and UNITIZED in the rear, but some of the creaks are gone! This isn't all that odd considering the body is now stiffer preventing flex therefore less movement of the plastic components. Just coming down off a curb you can tell the body doesn't move as much in the back. A list member said that he could tell the difference in handling on a SNOW COVERED road. That's incredible. I was concerned about reduced storage capacity in my trunk. I don't haul much, but I normally have a 10" bass tube in the trunk. It clears just fine. As for it being an eyesore, it isn't even visable when I open the trunk. I have to bend down just a bit to see it (I'm 5'11"). It is close to the seat backs and the parcel shelf so space isn't reduced by much. I'll be posting pictures of the installation on my Picture Page sometime Sunday: http://members.aol.com/mc2racing/pictures/ Until then, just email me and ask any questions you have. I really like how easy it was to install and the results are great for the capital outlay. How many other components could you build and install so beautifully for $17.00 complete? If you haven't done it and plan on autocrossing at Carlisle (or in Akron, Josh...) you haven't gone as fast as you can! ---------- Post Date: Tue, 26 May 1998 Subject: Re: rear shock brace difficulties A list member, concerning the installation of their shock tower brace, wrote: >When I went to instal it it didn't fit, the holes for >the bolts were too close together. I had to wreck >the finished product by enlarging the holes so >that they were 1/4" wider at the ends >:-( Maybe my theory is wrong, but I understand that the whole idea of the brace is to prevent movement of the shock towers toward each other. What these slots now allow is movement in the slots. Tightening the bolts more would help to a point, but keep in mind that bolts are designed to hold in tension (along the axis of the bolt) not in shear (perpendicular to the bolt, like the brace). So, technically, you'll have to get a new section of angle iron and cut the holes again. Here is the method I used to ensure the holes lined up. First, I drilled one hole. I slid it onto the threaded section of the bolt while it was in the car. Then, I scribed an arc (using the threaded end of the opposite bolt as the scribe) onto the section of angle iron, indicating the exact line that the hole should be drilled on. It fit like it had been machined not just drilled out by hand. ---------- Post Date: Mon, 2 Aug 1999 Subject: Re: Rear strut brace effective? List Members, Bill Williams has brought up this question before. It seems as though there is almost no way to test this other than using racer-testing methods of torsional rigidity. That would be pretty involved, requiring one side of the shell to be bolted to something solid and applying a known weight to a lever-arm bolted to the other side. Few are equipped to do this sort of testing. Allan Slocum wrote: > This is consistant with the reduction of > noises when I added the brace. I also think I feel the rear is stiffer. Speaking for another list member as well as myself, it has been said that the difference was noticed while driving on snow covered roads. As for my experience, I noticed that the rear end was stiffer when I backed down the driveway and the first rear wheel went off the curb. Here is a testing method suggestion. With creative use of a yardstick and some wooden dowels (or other cheap stock), I am sure some sort of measuring device can be installed between the shock towers to measure total relative movement in a braced and unbraced car.Back to the Tech Articles main page
Published by Chris Anglin.