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Drilled my holes for the Bump Steer mod, but.....


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OK. I wanted to get the holes drilled per the JTR manual to get rid of, or lesson the effects of bump steer. Well I marked all the holes for 3/4" above the original hole (center to center) and removed the "washers". I then took a nail to mark my holes so the drill bit wouldn't walk from my spot. Well obviously that didn't work because only one of the holes looks like it stayed where it should have. fmad.gif None of the holes are terribly off but they are off 1/16 in one direction or the other. One is 1/16 to low, the other looks like it moved 1/16th in and the other 1/16th out. Will this mean bad things for me, or is this little bit not enough to worry about. :confused: I know the original holes were out of round and didn't look "perfect" but I hate to think I just screwed this crossmember up, by doing this job. Please let me know one way or the other. Thanks for your help guys.

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You want to get the measurements as correct as possible. My advice (for what it is worth) is to file your way to the correct spot and then weld the 'washer' in the correct location. You can use weld material to compensate for the enlarged hole, but man is it ever hard to file...

 

Davy

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I agree with Davy and would only add that with the enlarged holes, you'll want to weld the washers in more than you would have otherwise. In other words, the washers are there mostly for a nice surface for the bushing to ride against. But in this case, you'll be depending on them more as a pivot location, so they'll need more than a simple spot weld.

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Guest Anonymous

Hard recovery.. to make new holes. I made a hole jig out of flate plate steel 1/8 inch thick to rest at the bottom of the cross member to re-locate the control arm pivot hole further up.The jig fixture could be reversed and and be used from side to side ,back and front The hole in the jig was 3/16 and I final drilled the 9/16 innch hole on a drill press. Davy has a good solution. Another solution I would suggest is to use 1/8 inch flat bar as a doubler washer and weld it inside the control arms, one on each side to cover up the bad holes and then wire weld these bad holes on the outside to remove them by later grinding the weld flush and start your new holes all over again with a jig fixture to locate the new holes.. I found the MSA polyurethane 2 piece control arm bushing took to the slightly oversized doubler i/8 inch strap that I used for the "smaller doubler washer". Good luck Watch the welding heat since the the cross member has a tendancy to warp easily . I had to use a porta power "spreader" to widen one side after the side drew in from heat warpage.

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I wouldn't be too concerned about a 1/16" here or there. The suspension holes weren't that accurately placed from the factory anyway. The true test is doing a bumpsteer measurement once it's done. How about taking the doubler washers in where the holes are now, installing it in the car, and measuring the bump steer. If it looks like a big problem, then go back and move them. Otherwise, take it back out and weld the doublers in well.

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Adjustable camber bushings can help with this when its time for the front end alignment so it can match side to side. You can also get another crossmember fairly easily and do this mod out of the car it seems. After center punching your holes, make a starter hole with an 1/8" drill bit or so, then hit it with a 1/4" before drilling your final hole. That should control the bit placement much better.

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Yeah, I figured the drilling with the 1/8" out after already doing the job. My one buddy came over and took a look at it with me and we've decided that it is so close that I would only be wasting time, and metal, if I tried to adjust it for "perfection". I think I could adjust out any of the slight variation when I get my alignment. I guess it was just one of those days that I wanted to get it done, and wasn't doing much thinking. I'll post some pics when it is together. Thanks for the replies guys.

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Originally posted by johnc:

> I wouldn't be too concerned about a 1/16" here or there.

Pete,

Sometimes I worry about you... :wink:

Of course, I can say that, since I made the mount points for the control arm pivot adjustable on my crossmember. :D

 

I can adjust the horizontal and vertical position of the pivot bolt independently, +/- 1/4" of the recommended JTR relocation specs. Haven't found time to fine tune it yet, but I have it set to nearly the "JTR" relocated points and it's fairly good in bumpsteer, by road feel.

 

I guess I was thinking about Michael Fawke's (from the IZCC mail list) observation that a single "relocation" spec for the pivot point isn't optimal from one crossmember to another. So if you are off a bit, it probably won't matter a bunch. The fact that you're 3/4" +/-1/16" above the stock pivot is going to be an improvement. You really need to measure the bumpsteer to know where the hole NEEDS to be.

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I have to agree with Pete here, that 1/16th of an inch is not a big deal--it might even average out between the two holes once you get the bolt through it. I took my crossmember off to do the modification recently, only to find that my current holes were nowhere near where they were supposed to be according to the pictures in the JTR book. Mine were closer to the modified location. I think someone had already done the modification, but they did it so well that I couldn't see any evidence that it had been tampered with. However, the holes were slightly off (slightly more than yours)and I never noticed it while driving--and I'm like the princess in the fairy tale who could tell that there was a pea under 20 mattresses. When it comes to suspension tuning, I can usually pick up subtle abnormalities, and I didn't even notice anything was different, except that I had never noticed any bumpsteer.

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