Scale Nascar
PRODUCTION 4-1/2 STOCK CAR
All General Rules also apply.
A. Chassis
See Stamped Steel Chassis Regulations on page 52.
1. Must be a commercially-available, stamped and formed chassis with a 4-1/2
inch wheelbase and be approved for competition.
2. If using extenders, must use original manufacturer’s extenders on the chassis
they were designed for. May solder extender to chassis. May remove front
wings for extender/front wheel clearance only.
B. Motor
See D-Can Motor Specifications on page 48, A. Motors (Stock 16D).
C. Bodies
See Stock Car Body Specifications below.
D. Gears
Any gear ratio allowed. Pitch of gears is unrestricted as of 2008. May sol-
der pinion onto armature shaft.
E. Axles &Tires
1. See General Scale Rules on page 49 – Wheels, Tires, & Axles section.
2. Minimum front and rear axle diameter is 3/32 inch. Steel axles only. No
hollow or other lightweight axles. Drill blank axles are allowed.
3. Tires front and rear must be composed of black foam rubber only. No dyed
tires allowed. May add nail polish to front tires.
4. Front tire minimum diameter is .675 inch (17.15 mm). Minimum front tire
width 0\400 inch (10.16 mm). Minimum rear tire diameter is .790 inch (20.07
mm). Maximum rear tire width is .810 inch (20.57 mm).
5. Independent rotating fronts wheels are allowed.
6. Solid, one-piece front axles only; no stubbies. Axle must pass through both
front uprights. Front axles may be soldered to uprights, but front wheels
must rotate. Axle hole in front uprights may be enlarged to allow .675 front
tires to touch the track but 4-1/2 inch wheelbase must be maintained.
F. Clearance
See General Scale Rules – Clearance Section.
STOCK CAR BODY SPECIFICATIONS
A. Rules applying to both Group 10 (4”) & 4.5” Stock Car
1. See General Scale Rules – Bodies section.
2. No air control devices allowed. No alterations or additions to the manufacturer’s
dimensions are permitted. Body must cover entire chassis when viewed from
above.
3. May reinforce body with tape or Lexan.
4. Bodies must be fully-painted and all window areas must be left clear.
5. Body must have full Stock Car interior (Parma #809 or similar) properly-
painted, and installed in the correct position, and completely covering inte-
rior. Chassis or track must not be visible when viewed from above.
6. Front wheel wells may be cut out or left clear. No cutting into the top of the
fenders.
7. Must have three decal or painted numbers placed on body, one on each door
and one on the roof. Bodies should be painted to resemble real stock cars.
8. No wedging of bodies.
9. Tech Director reserves the right to allow or disallow any cars or bodies and
his decision is final.
B. Dimensions and rules applying to Group 10 (4”) Stock Car Only
1. 4-inch Stock Car bodies will be used. Should represent the full size car. Only
Stock Car body styles will be permitted. Bodies must have front and
rear bumpers.
2. See Stock Car dimension diagram below for measurement points (A-D):
A = Roof Height: 1-1/2 inches (38.10 mm) measured from the track to the
center of roof; roof ribs not included. Roof height will not be checked
during tech inspection as of 2008.
B = Front Bumper: Minimum 1/8 inch (3.18 mm) measured from the top
of bumper down.
C = Rear Bumper: Minimum 1/8 inch (3.18 mm) measured from top
of bumper down.
D = Rear Spoiler Height: Maximum height 1-3/8 inches (34.93 mm)
measuring from test block.
3. For manufacturer specifications, please refer to the USRA website at
www.usra.us.
4. Must retain a minimum of 5/8 inch (15.86 mm) rear valance measured from
the trunk lid down. Rear bumper may be included in the measurement, but
must also be minimum 1/8 inch (3.18 mm). May not cut out or put holes in
rear portion of bodies.
5. Rear spoiler to be blade type only with a maximum height of 1-3/8 inch
(34.93 mm) measured from tech block to the top of the spoiler. Spoilers are
to have no side dams/plates, no radius or fillets between the trunk lid
and blade/spoiler.
C. Dimensions and rules applying to 4.5” Stock Car Only
1. Bodies must be 1/24th scale 4-1/2 inch wheelbase stock car bodies that are
commercially-available and approved for USRA competition. Minimum
length 7-1/2 inches (190.5 mm). Only body styles resembling Stock Cars
will be permitted.
2. See Stock Car dimension diagram on page 55 for measurement points (A-D):
A = Roof Height: 1-7/8 inches (47.63 mm) measured from the track to the
center of roof; roof ribs not included. Roof height will not be checked
during tech inspection, as of 2008.
B = Front Bumper: Minimum 1/4 inch (6.35 mm) measured from the top
of bumper down.
C = Rear Bumper: Minimum 1/8 inch (3.18 mm) measured from top
of bumper down.
D = Spoiler height: Maximum 1-5/8 inches (41.28 mm) height measured
from tech block to top of spoiler.
3. For manufacturer specifications, please refer to the USRA website at
www.usra.us.
4. Cars must have front and rear bumpers. Front bumper must be at least
1/4 inch (6.35 mm) tall, measuring from top of bumper down. Rear
bumper must be at least 1/8 inch (3.18 mm) tall, measuring from top
of bumper down.
5. Car must retain a minimum of 1-3/16 inches (30.16 mm) rear body valance.
This will be measured from trunk lid down. Rear bumper may be included in
the measurement, but must also be a minimum 1/8 inch (3.18 mm). May not
cut out or punch holes in rear of the body.
6. Rear spoilers are to be blade-type only with a maximum height of 1-5/8
inches (41.28 mm) measuring from tech block to top of spoiler. Rear spoil-
ers are to have no side dams/plates, no radius, or fillets between the trunk lid
and blade spoiler.
7. No air control devices allowed. No additions or alterations to the manufacturer’s
dimensions are allowed except for the following:
a) Rear spoiler maximum height is 3/8 inch (9.53 mm) measuring the actual
blade/chord length. May add Lexan to meet this measurement.
b) Rear spoiler maximum width is 3-1/4 inches (82.55 mm). Lexan may be
added to meet this measurement.
c) No “Gurney Lip” or additional bends in the spoiler allowed.
8. No cutting into top of body or fenders allowed. No part of the chassis or tires
may be visible when viewed from above. Maximum of 1/8 inch (3.175 mm)
of tire may be visible as viewed from above.
9. Front wheel wells must be cut out.
D-CAN MOTOR SPECIFICATIONS
A. Motors (Stock 16D)
Must be commercially-available, meet all USRA manufacturing specs, and
be approved for use in this class by the USRA. A minimum number of 500
pieces is required for approval, and must be available through distributors
and or raceways by Oct. 1 prior to the National Event.
1. Stock 16D style set-ups only. Must be commercially-available. Setup must
retail for the USRA 16D Setup maximum price or less (see USRA Price
Limit Table on page 44). Setups sold with aluminium spring cups must retail
for the USRA 16D Setup With Aluminiuum Spring Cups maximum price or
less (see USRA Price Limit Table on page 44) may compete.
2. No modifications allowed except as follows:
a) Racer may add can screws.
b) May add spacers to limit end play.
c) May dye armature.
d) May re-true commutator.
e) May zap magnets.
f) Magnets may be shimmed..
g) May glue magnets in place. Any adhesive may be used.
h) May change brushes and may use any three-coil springs.
i) No polishing or honing of magnets is allowed.
j) Balancing is allowed.
k) Armature may reconditioned; coating may be removed.
l) There is no minimum air gap in 16D motors, begiing in 2008.
m) May interchange parts between manufacturer’s set-ups.
n) Oilite may be soldered in place.
o) May use any USRA-approved C- or D-can endbell hardware as
replacement hardware. Aluminum or brass spring cups may be used as
replacements.
p) May solder and/or glue endbell hardware together and to endbell.
3. Cans (16D)
a) Must be made from metal, and have no cutouts or metal removed from
sides of can. The only allowable cutouts are the axle notches. Only one
hole is allowed on the top and bottom of can. No strap-type cans allowed.
Cans must have a full top and bottom. No cheater tabs on cans allowed.
b)Must meet the following minimum inside dimensions:
Height: .600 inches (15.24 mm)
Width: .875 inches (22.23 mm)
Length: .950 inches (24.13 mm)
c) Definition of can shall not include surface treatment. If a manufacturer
introduces a plated can they need not go through the submission process
again. Plated can must sell for the same price as the unplated version.
d)Cans submitted for product approval after January 1, 2005, must be no
lighter than the lightest approved can commercially available on January
1, 2005. This is a manufacturer specification, not a racer specification.
The minimum weight is 2.1 grams.
4. Magnets (16D)
Must be stock one piece single (no quads) ceramic magnets as found in the
production motor, and meet the following minimum dimensions:
Height: .570 inches (14.48 mm)
Length: .650 inches (16.51 mm)
Thickness: .145 inches (3.68 mm)
5. Armatures
See Armature Tecnical Specifications on page 47 for armature specs.
6. Set-ups (16D)
16D set-ups are to be submitted and sold as ready to run. Set-ups should be
ready to install a armature, brushes, spacers, springs with no further assem-
bly work needed. Set-ups would have the magnets installed by using magnet
clips or can fingers folded over and/or super glue used to retain magnets.
Can oilite pressed or soldered in place. End bell fully assembled and drilled
for can screws. Parts/kits are not acceptable as set-ups.
Exceptions to rules above...
Can bearing permitted on motors....
Any production 4 1/2" body permitted as long as all measurements pass guidelines.
