This page was created in response to the requests from
a few hobbyists for some sort of maintenance schedule. We've tried our
best to make these tips apply to everyone, but where different R/C hobbyists
require different maintenance schedules for the same item, we listed the
general hobbyist's needs first, then address the racer's needs. These
tips are great for those new to the hobby, and are great reminders for
experienced racers, too! This page covers every topic about electric and
Nitro cars, from batteries and motors to cleaning bearings and rebuilding
diffs. It's a great resource for racers at any level!
The Maintenance Tips are split into three different main
sections - General,
and Serious Racing. Each main section has
subsections that get specific according to the area of the car discussed.
The subsections provide a brief definition of the item being referred
to, then describe how to perform proper maintenance. The second paragraph
of each subsection is for the racers who may be reading.
Beginners please note: On this page and
throughout the site, the term "run" when talking about electric
cars refers to running the car for a full battery pack, until the pack
is discharged. When the term "tank" or "run" is used
in reference to Nitro cars, it refers to running the car for one full
tank of fuel.
Check out our R/C Glossary,
perfect for a starting point to figure out all those R/C terms you're
General Maintenance - applies to all cars
General Cleanliness - A clean car is
a happy car! Not only that, but you will be able to spot problems easier
on a clean car than on a dirty car, and also while cleaning it, you can
give the car and body a quick look to see if anything is wrong. Use a
large natural-hair bristle brush (from a hardware or paint store) to remove
dust from the chassis and inside of the body. Use some denatured alcohol
or motor spray to clean off tire and asphalt marks from the outside of
Differentials - These let the outside
wheels in a turn spin faster than the inside wheels, so the car can maintain
the proper path when turning.
For cars using gear differentials, you should check the
areas around the diff shafts for grease leaks every 20 to 25 runs. If
you see a leak, you need to take apart the diff and put more grease in
it, and reassemble it carefully.
If you run a car with ball differentials, you should check
the diffs for grittiness every 5 runs or so. To do this, put the car on
a stand so the wheels can rotate freely. Hold the spur gear and slowly
turn a wheel. Try to feel if the action is smooth or 'gritty'. If it feels
gritty or the wheel is difficult to turn, you need to rebuild that diff.
Now check the other diff using the same technique. You can use diff rings
and thrust washers twice - just flip them over to a smooth side. If you
don't have a smooth side on the rings or washers, you need to buy new
ones. We don't recommend using diff balls and thrust balls through more
than one rebuild - you should replace these each time you rebuild a ball
differential. Carbide diff balls will last longer under the same circumstances
as regular diff balls.
Shocks - Shock absorbers soak up bumps
in the track and let the tires maintain constant contact with the racing
surface; they also let the tires dip into depressions in the track. If
you are a 'backyard basher' or casual hobbyist who doesn't race, you should
give your shocks a look over before each time you run the car. If you
see any leaks, you need to rebuild your shocks. When rebuilding shocks,
you should always use brand new o-rings. Never re-use old o-rings!
Racers should check their shocks before and after each
run. Any leaks mean it's time for a rebuild. Shocks on a racing R/C car
should be rebuilt or given a good look every ten or fifteen runs. Be sure
you write down what shock oil you are using in the car! Either write it
on the shock cap in a fine-point permanent marker or use one of the HPI
Setup Sheets. When rebuilding shocks, you
should always use brand new o-rings. Never re-use old o-rings!
Drive Pulleys - These either turn the
belts (on the gear shaft) or the belts turn them (at the diffs). Whether
you race indoors or outdoors, you should check the teeth of each pulley
before the day's racing begins for any rocks, tire debris, tape, etc.,
that get stuck in there. Use a hobby knife or a dental pick ('teeth' cleaner,
Drive Belts - Provide a way for power
to be transferred from the gear shafts to the diff pulleys. The belts
should be replaced if you notice any significant wear on them (if you
can see threads hanging off the belt, that's significant!). Also, if the
belt gets so loose that no amount of tensioning helps, you should replace
the belt. Belts are a wear-and-tear item; they must be replaced periodically,
just like the belts on a real car!
Belts should not be "guitar string tight", they
should be loose enough that you can wobble the belt up and down, but tight
enough that the belt does not slip off a pulley under braking or acceleration.
For the most part, the rear belts won't have to be adjusted, but the longer
belts (front belt, in other words) will need to be adjusted periodically
for most cars.
Bushings - Used on most rotating parts
on sport or budget kits, bushings are better than direct contact between
the parts, but not as good as ball bearings. Bushings don't need any maintenance
to speak of, just keep them clean and grease them when they are first
Ball Bearings - Used on most rotating
parts on pro-level kits, bearings provide a way to eliminate almost all
of the resistance that bushings have and serve to make the car quicker
overall. For HPI kits with the standard shielded bearings (metal shields
on the side), just brush them off every now and then. You may want to
put a very light dab of oil and let it soak into the bearing,
but for the most part just brushing the dirt off the bearing is fine.
HPI's more recent kits now include rubber sealed bearings, which require
even less maintenance. All HPI kits that include bearings already are
being upgraded to rubber sealed bearings.
Gear Mesh - The relationship between
the primary drive gear (pinion or clutchbell) and the secondary drive
gear (spur gear). A tight gear mesh (the spur cannot 'wiggle' when installed)
has too much friction and will cause the motor or engine to work too hard
and could melt the spur gear from the friction. A loose gear mesh (the
spur can move significantly) will probably cause the pinion gear to strip
the spur gear, ruining the spur gear.
To set a proper gear mesh on electric cars, use a small
piece of normal notebook or copier paper and put it in between the pinion
and spur, and tighten the motor onto the motor mount. Remove the paper,
and that is how much gear mesh you should have. For Nitro cars, you can
get away with a little bit looser gear mesh than on electric cars because
the gear teeth are much larger. Use the same technique described above,
but fold the paper once before you put it in between the gears.
One-Way Diffs - Many racers do not lubricate
the one-way differentials as often as they should. Every few runs, you
should take the one-way diff out and remove the gear shafts to inspect
the bearing. If there is no hint of grease on the bearings you should
use a very small amount of the blue-capped grease that comes with the
one-way diff (the amount of grease that would end up on a toothpick or
pin if you dipped it in the grease) and re-lubricate the one-way bearings
inside the main diff body. This will help prevent a major cause of one-way
diff failures. Crashing and no lubricant are the main reasons why the
one-way bearings in the one-way diff break.
Motor - The powerplant of an electric
car, the electric motor requires proper maintenance to run smoothly and
efficiently. Motors have many maintenance-intensive parts; we will deal
with each one separately.
otor terms: First, however, we will go
over the basic parts of the motor. The can is the metal
main body of the motor. The motor magnets are glued to
the inside of the can. One bearing (for modified motors)
or bushing (for some budget modified or stock motors)
is at the end of the motor can, where the motor shaft
The endbell is the plastic part of the
motor that seals the motor and has another bearing or bushing where the
other end of the motor shaft sits. The brush hoods hold
the brushes on the endbell, and the motor springs
hold the brushes against the commutator. The brushes are the
only parts of the motor that touch the commutator, and are very important
in modified racing. Every brush has a shunt wire, which
is how the brush is connected to the brush hood. Solder them on for maximum
efficiency, or use screws and eyelets for convenience.
Most brushes are available with or without eyelets. Some endbells have
heatsinks built into them, and others have inspection
holes so you can check the commutator without taking off the
brushes. Some endbells have both features. The endbell also has the motor
tabs, where the motor wires or connectors are soldered.
The armature sits inside the can. The
armature includes the motor shaft and all the stuff that spins inside
the motor. The commutator is the copper part of the armature,
and is only part that most racers have to worry about. It must be in good
condition for good performance and high efficiency. The armature also
features copper wire wrapped around laminated stacks
of metal that are cut into distinctive shapes called poles.
All stock motors have the same number of winds (wraps
of wire around each pole), while modified motors have less winds with
thicker gauge wire for more power and RPM (Revolutions Per Minute).
Now that the motor terms are out of the way, let's move
on to motor maintenance!
Cleaning - You should purchase a can
of motor spray (HPI's Nitro Car Cleaner is a good bet) and a set of
commutator cleaning sticks. Remove the springs from the endbell, then
take out the brushes. Don't lose the springs! Holding the motor with
the endbell facing down, spray the commutator from three or four sides
(rotate it if you have to). Let the motor spray dry, then insert the
square end of the blue or red comm stick and hold it lightly against
the commutator. Rotate the motor shaft several times to let the comm
cleaning stick do its job. Then do the same thing with the green (polishing)
comm stick. Racers should clean the motor after every run, casual hobbyists
should do it at least every two or three runs.
We'll cover cleaning the brushes when we get to the
section on motor brushes.
Commutator Truing - If you don't race,
you should have someone true the commutator of your motor (whether it's
a stock or modified motor) every ten to fifteen runs. Ask your hobby
shop if they true motors there, or find a racer who is willing to help
you. At most, you might be charged $5. This helps the shop or racer
cover the cost of the diamond bits on the motor lathe, which often costs
$85 or more, on top of the more than $100 it cost for the lathe!
If you are a serious racer, you should have your comm
trued at least every four to five runs. The more often, the better.
Having more 'shallow' cuts more often is better than just a few 'deep'
cuts. After each cut, you should replace the brushes as well, since
the commutator has a new profile. Backyard bashers won't have to worry
too much about replacing the brushes, but it should be done when the
the brushes are noticably worn down.
Truing the commutator and replacing the brushes basically
'refreshes' the motor and makes it run pretty much like new, so it's
a highly recommended procedure!
Motor Brushes - The brushes on your
motor should be cleaned when you clean the commutator. Use the motor
spray to clean the ends of the brushes, and then use the round end of
the blue or red comm sticks to clean the face of the brushes. Rotate
the sticks, don't move them up an down on the face of the brush! Then
use the green comm stick to follow up the cleaning.
About brushes and comm truing: Casual R/C hobbyists
won't need to replace the brushes on their motors very often, only when
the brush gets worn down to about 2/3 its original length. Using serrated-face
(quick break-in) brushes is fine for the 'backyard basher'. Racers,
on the other hand, should get a new set of brushes every time they have
the commutator trued on their motor. This allows the new brushes to
re-seat themselves on the new, smaller comm diameter. The race-style
brushes that don't feature a serrated face are best for serious racers,
since the serration breaks in quicker, but causes a little extra wear
on the commutator that racers may not like.
A note about high silver content motor brushes:
If you use a motor that has high silver content, you should know that
those brushes should be replaced every two or three runs because they
wear very quickly. They are meant for serious racing only! If you are
a casual hobbyist and bought a motor that has these brushes in it, you
should replace them with an economical pair of brushes when the originals
If you run your motor in very hot conditions (no cooling
air, high gearing, etc.) there is a chance your brushes could be damaged.
If the brushes, commutator, endbell or brush springs look discolored
after a run, you need to take it easy on the motor, or it won't be able
to run much longer! Remove the inner body or use a smaller pinion or
larger spur gear when running the car with that motor. Beginners need
to be especially careful with modified motors, because the gearing for
them must be lower than for stock motors.
Brush Springs - Most R/C hobbyists
shouldn't need to ever replace the springs on the motor. If you run
the motor very hot (see above) there is a chance you can damage the
springs so that they don't maintain the same tension on the brushes.
A sure sign you are running the motor too hot is that the brushes come
unsoldered! If this happens you will probably have to replace the brushes
and springs, as well as true the comm, to get the motor up to normal
Bushings and Bearings - Use an oil
specifically made for bushings or bearings, and completely fill up the
end cavity where the motor shaft sticks out on the outside of the can
and endbell. Fill one end of the motor, spin the shaft a little, then
fill the other end. Oiling the bushings of a stock motor is very important,
since not oiling them can cause extra friction you just don't want!
Batteries - Many racers follow a myth
that there is a science to charging and discharging batteries. Here is
the simple truth:
Charging - Use a peak-detecting linear
charger to charge the batteries at 4 amps. That's it!
Battery chargers that use a timer, or feeling the warmth
of the batteries is nowhere as exact as peak charging, but for casual
R/C drivers, it gets the job done. The HPI Team Drivers at the ISTC
World Cup charged their batteries at 4 to 5 amps.
Discharging - For 95% of racers, all
that is needed to discharge the battery after running is to run the
car until it is very slow, then take the battery out and let it and
the motor cool down.
If you don't have time to run the batteries down (for
instance, at organized races where you can't run your car when it's
not your race), you can use a single 12 volt automotive light bulb (#1157
standard type bulb) to discharge the battery pack. Some racers feel
that using 20 amps to discharge the batteries after a race allows them
to gear the car better, but with today's RC2000 and RC1700 batteries
runtime is much less of a factor, especially in stock class racing.
Modified racing is a slightly different story - you still have to know
how to gear the car to avoid dumping.
You can run most battery packs more than once a day,
as long as you let it cool down first! Batteries such as 1400's
or 1500's shouldn't be run more than once a day very often.
The reality is that it is easy to listen to experienced
racers go over the 'proper' way to charge or discharge a battery, but
you should know that there is no need to over-analyze the simple process
of charging and discharging a battery pack. Properly cared for, a battery
pack (even a cheap one) will last you for many years.
Nitro Car Maintenance
General Cleanliness - Use a spray like
HPI's Nitro Car Cleaner or undiluted Simple Green to clean the car of
grease and road grime, and keep a natural bristle brush handy to clean
dust off the body and chassis between races.
Engine - The powerplant of the Nitro
car and most of its weight. The inside of the engine should be checked
for excessive wear by an experienced Nitro racer every 2 gallons of fuel
or so (or 100 hours of running time on the engine). You may have to put
in a new piston and sleeve, but after that the engine will run like new!
You also should use After Run at the end of each day's running. Do NOT
use WD-40 on the inside of your engine! After Run will absorb the water
in the engine, not just displace it. Just follow the directions on the
After Run bottle.
Ball Bearings - Make sure they are clean
on the outside. Wipe them free of any grease from the exhaust and 'road
grime'. Check the bearings after each day of running.
Nitro Two Speeds - The #B080 one-way
bearing in the spur gear needs to be checked and lubricated every ten
to twenty runs. Use the blue cap grease that comes with the front one-way
diffs or some good quality lithium grease. Just a light coat is required
to properly lubricate the bearing, so don't use too much!
Brake Disc - The only way you can stop
your car, unless something bad happens to your brakes (in which case,
a wall is the only thing that will stop the car!). Before each day of
running, you need to check the condition of the brake disc itself, the
brake linkages, screws and spacing of the screws holding the brake pads.
Screws - Since they hold the car together,
you should check all the screws every couple of days of running the Nitro
car. They should be tight and not stripped out. Replace the plastic bulkheads
if the screws are loose and won't tighten. Use Loctite on all metal-to-metal
screw connections (the motor mounts, etc.).
This section is for those racers who are very serious
about their racing! So don't be surprised if you see a suggestion here
and wonder, "Do people actually do this?", because they do!
These suggestions are not for beginners or casual racers! These tips
assume you have a good knowledge of your car and are comfortable with
taking it apart and reassembling it. Some of these tips will cost some
money, and we are NOT trying to bankrupt racers, just give them a reference
to check before they go to a big race or event.
Plastic Bulkheads - Over time, these
will loosen and get weaker. If you constantly tighten and loosen the screws
going into these plastic parts, you will accelerate the wear. To help
prevent chassis tweak during races (wrecking), these parts should be as
new as possible. Replace them before major events and use new screws if
Hingepins, Shock Shafts and Kingpins
- When tearing apart the car, check these parts. If you roll them across
a piece of flat glass or countertop and notice a wobble, replace the offending
part! Otherwise it will be binding up the suspension movement. Before
a big race or when tearing apart your whole car, it's a good idea to use
put the hingepins in a rotary tool and polishing them with some polishing
compound on a rag.
Ball Cups and Shock Ends - If you have
any play (side-to-side, or lateral play; this doesn't refer to the 'looseness'
of the ball cup) in these parts you need to replace the plastic part so
you get a more responsive suspension setup. Some racers build up layers
of CA glue inside the ball cups to get a tighter fit on the ball ends.
Ball Ends - If you have a scratch on
a ball end, you'll need to replace it. That scratch will catch on the
plastic ball end or shock end and cause it to bind.
Ball Bearings - Some racers getting ready
for a big race will clean out the thick grease completely from the bearings
(soaking overnight in grease solvent or Simple Green usually does the
trick - follow it up with blasting the bearings with motor spray or brake
parts cleaner). With all the manufacturing grease out of the bearing,
apply a very light amount of miniature bearing oil to the bearing, and
that's it. Some racers go so far as to remove the side shields from their
bearings to remove the extra friction caused by them.
Shocks - You should rebuild the shocks
more often than the casual racer. A very important point that is overlooked
by most racers is to make sure the shock's overall length is the same
from left to right. Some racers have different length shocks front and
rear, so make sure that at least the left and right shocks at each end
are the same.. This helps make sure the car is not tweaked to the left
or right. Trim the shock ends properly so there is nothing sticking off
the ends (a file or emery board works great on the rounded ends), and
use a set of calipers to measure the total shock length. The length can
be adjusted by turning the plastic shaft end, the 'eye' piece that snaps
on the ball end.
Racer's tip: You can replace the ball ends that
hold the ends of the shocks with HPI #A133 (Ball 3 x 5.8 x 6mm) or the
similar Associated part (6471, 7217 or 7660) and use screws to hold the
shocks in. From the #6817 Shock Parts Set, just use the eye pieces that
are slightly larger than the ones called for in the instructions (you've
always wondered what those were for, didn't you?) and substitute them
for the stock eye pieces. Just be aware that by using these, you will
extend the overall length of the shocks, and you will have to adjust the
ride height accordingly.