Originally Posted by
billythekid
Hi Hiro, why do you recommend lowering the roll center with this mod?
Also, what is the easiest way to drill the 2 additional holes accurately?
Generally, whenever you widen out from the hinge pins the car won't roll as much. When running blocks much wider than stock like 2.0 or 2.5 deg, it tends to make the car push a little more mid-exit. By lowering the roll center (going to 1.0mm under the blocks) it helps remedy that.
At Reedy I ran a 3.0 deg FF block, and a 1.0 deg rear block. Overall, the car had killer turn in, but I just wanted to get a little more mid-exit steering, so I dropped to 1.0mm shims under the FF and FR block. Overall that seemed to work really well.
There is no super easy way to make sure they are located correctly unless you have really $$$ equipment. Although, it can be done at home with the right tools. A lot of it comes down to how well you can measure, and be accurate. Here's how I did mine:
1. What I did was draw a line right down the centerline of the chassis. This will be used as a reference line.
2. Then I drew a line from the center of the FF suspension block holes, down the length of the chassis, parallel to the center line. Do this from the other hole as well. Thats probably one of the most important things to get right.
3. Next step is pretty easy. Now you just need to draw a line from center to center across the existing FR suspension block holes. The intersection of the lines (except that center line) is where the holes need to be drilled.
4. To drill the holes, I used a drill press. I clamped the chassis down to the table of the drill press, with a piece of wood under the chassis. This helps back the chassis and prevent the fibers from blowing out and looking nasty as the drill bit punches through. Drill your hole with a 3mm drill bit.
5. Now without unclamping the chassis from the drill surface, remove the 3mm drill bit and load up the countersink bit. By not removing the chassis, or moving the drill location, it will ensure the countersink is centered on the hole you just drilled. Make sure it's a 90 deg countersink bit. THIS IS EXTREMELY IMPORTANT!!!!!! Most Hardware stores have 82 deg countersinks, and this is for SAE hardware. Metric hardware uses a 90 deg countersink angle. Just use the countersink bit and go a little bit at a time, testing the fit of a countersunk screw. You have to make sure not to go too deep.
6. Repeat step 4 and 5 for the other hole
Hope that helps some...
-Korey