B6.2 Rear Arm Modification

- B6.2 Rear Arm Modification -

by Ray Munday

You may notice on many of our setup sheets using the layback transmission outdoors that we are using rear arms dremelled to get 4mm shorter wheelbase at the rear. This moves a little more weight over the rear wheels but more importantly sweeps the driveshaft forward further which creates more traction under power. During the lockdown period I've taken the opportunity to prepare a few sets of both the 73mm and 75mm rear arms for myself and Lachlan Munday RC Racer.

To do this you will need:

Dremel with sanding drum
Vernier calipers (accurate to at least 0.1mm)
Hobby knife /scalpel
safety goggles
4 of 3.5mm ID X 2mm shims

The kit arms measure 35.6mm wide at the inner pivot, so we Dremel them back to 31.6mm. I do this using the Dremel, holding as shown in the image below (always use eye protection). You need to take enough material off to clear the chassis as the arm rotates, so I take the cut all the way to the base of the 'v' in the front face of the arm. We use the innermost shock hole, so make sure you are cutting the correct face :). As you get closer to the correct width cut slowlyyiu want to get the width as close to 31.6mm as possible.
The right hand side arm needs a title extra clearance to clear the spur gear of the layback transmission at full compression. I've shown a picture of the extra material you need to remove.

When you have finished, use a scalpel to make a small chamfer around the edge of the cut and most importantly clean the material out of the pivot pin hole (I use a reamer then the knife).

When you have finished, test fit in the car with the shocks disconnected and make sure the arms move smoothly without fouling on the chassis. I use the alloy 3.5mm X 2mm hub spacer washers (Team Associated #31389) to space the arms forward, but you can also use the parts that are included with spare arms.

We are still testing the options available with the 6.2 parts but early testing has shown this mod with the +3mm chassis to work really well in lower grip and bumpy tracks.

Good luck at the track!