BMI Racing DB12RR - Manual (Page 8)

Step 20
1. Install the molded shock mount-antenna mount
with 2 4-40 x 3/8” flat head screws
2. Assemble the IRS Nickel-Teflon Pro Shock as per
the included instructions with 35wt silicon shock oil.
3. Place the one long black alloy ball stud in the
antenna mount and a standard ball stud in the rear
pod top plate as shown. Secure the top pod plate
ball stud with an alloy lock nut.
4. Install the included gold shock spring onto the
shock and snap the shock in place.
Trim the ball cup on the shock that attaches to the
antenna mount to .472” (12mm) in length. Thread this
short ball cup on so the over all shock length is 2.6”
(66mm). This length will give you the standard setting
of 1.5mm of rear pod droop. If you thread on the ball
cup until it stops, you will have zero pod droop.
Diff Assembly:
1. Put a small dab of diff grease on the axle flange
so the diff will stick to it. Place a diff ring on the
flange so its flat keys onto the flat on the diff
flange.
2. Place a flanged 3/8 x ¼” bearing in the center
of the spur gear. Slide the spur gear and
bearing unit on to the axle until it stops against
the diff ring.
3. With a small flat screw driver remove the diff
balls from the diff grease and snap them into
the outer row of holes in the spur gear.
4. Place a flanged 3/8 x ¼” bearing into the inside
face of the right side diff hub. Put a small dab of
diff grease on the hub flange so the diff will
stick to it. Place a diff ring on the flange so its
flat keys onto the flat on the hub flange. Slide
this unit on to axle.
5. Slide a flanged 3/8 x ¼” bearing over the axle
into the outside face of the right side diff hub.
Slide the stepped thrust cone onto the axles so
the smaller diameter part is against the right
hub bearing.
Locate the rear axle parts bag. There are a couple of steps
that can make your diff last longer that should be done at
this time.
Use the right alloy diff hub as a holder and sand both sides
of each diff ring on 600 grit sand paper using electric
motor cleaner spray as a lubricant. Sand until you see an
even scoring pattern across the face of each diff ring.
Clean them with motor spray and set them aside.
The diff balls may have a protective oil coating on them.
Place them on a clean paper towel and carefully clean
them with motor spray. When dry drop them into your cup
of diff grease and stir them to coat them with diff grease.
Step 21
Step 21 Continued
6. Thread the black nylon lock nut onto the
threaded stud on the axles until it makes
contact with the thrust cone.
7. Tighten the black lock nut gradually with an
11/32” nut driver until you notice you cannot slip
the spur gear when holding the axle and right
hub in a fixed position.
Six 4-40 x ¼” cap head screws are supplied to mount
your rear wheels.
Notes:
Keep you fingers clean with motor spray. Diff
assembly is like surgery. You do not want dirt
or oil where it does not belong.
The grease on the diff balls when you pluck them out
of the cup of diff grease is all you need.
Smearing diff grease on the rings will make
your diff get dirty faster and make a mess.
The ultimate goal in building a diff is one which is
extremely free and glass smooth but requires a
lot of force to slip the spur gear.