- Sedan Tires & Inserts -
Words: David Jun
Tire and insert
choice is probably the most important aspect of an R/C car's
performance, especially in competition. Whether you're a
competitive racer participating in organized racing events or a
casual R/C enthusiast, the more performance you get out of your
tires the more fun you'll have. With all the options available
in the sedan market for the consumer, it has become somewhat
difficult, not to mention confusing, looking for the right
insert and tire. This segment is based on my personal
experiences and is a basic guide intended to help you choose the
best tire and insert for your sedan.
|
Let's start with
tires. If you race at a local track, there is probably a popular
tire that everyone already uses. Usually, that tire is popular
because the most competitive drivers use it and for this reason,
others have assumed it's the best choice. While this is an
effective way to make your decision, keep your mind open to test
other tires. In my experience competing in major events (before
spec tires were implemented), the tires that most of the
competitors settled on, in many cases, were not the tires
favored by the track locals. A lot of this is due to the fact
that conditions always change (even indoor tracks), including
the same day. This is because of factors such as dust or
humidity but it's mostly due to changes in temperature, even as
the day progresses.
|
There are many different manufacturers that produce sedan tires
and each tire was designed for a general operating temperature.
Most manufacturers will not label the temperature range of their
tires due to the amount of variables that can effect the overall
performance. Instead, most tires are categorized by an
alphanumeric code or by a simple description like soft, medium
or hard. Usually, the lower the alphanumeric code, the softer
the compound. Cooler temperatures typically require a softer
compound as hotter temperatures generally require a harder
compound. However, the track surface often has characteristics
that will also effect tire choice. For example, a coarse surface
will put more friction on the tire; friction creates heat and
the higher the temperature the harder the compound you'll need.
Yes, you can overheat a 1/10th scale sedan tire, which is why
different compounds are available. In other words, just because
the track temperature is low doesn't always mean you need a soft
compound. Unfortunately, these cases are not as black and whites
as we might like, but by taking these factors into consideration,
you can better choose and test various compounds. Most tires on
the market are belted with a type of cloth or glass fiber. The
belting reduces tire distortion especially at high speeds and
during cornering. This reduces feathering or blistering of the
tire surface and extends the life of the tire.
|
With a sedan tire, you need an insert, which is as important as
the tire itself. Inserts are like the air pressure in a full
size car tire because both are responsible for supporting the
tire. Over inflating your full size car's tires will cause them
to crown, decreasing the tires surface contact to the road and
reducing the tires ability to absorb bumps, both resulting in
reduced performance. The difference in a 1/10th scale sedan tire
is, the insert can independently effect the tire profile from
the amount of support. Meaning,
a soft insert can crown the tire as much as a firm insert can.
The profile of the tire is an extremely important aspect of how
the tire will perform and just like a full size tire, there is
an ideal range. That range is typically that of the empty tire.
Manufacturers profiled the tires to maximize the surface area
that would contact the track surface and generally speaking, if
you alter that profile too much by using a big or tall insert,
you will compromise the amount of grip the tire can generate.
The key is to choose an insert that fits the tire.
|
Like tires, inserts are also available in various compounds as
well as materials. Soft, medium and hard is for the most part,
the industry standard. With that in mind, you should consider
the track surface conditions before selecting a compound,
because in a way, the insert and tire is indirectly a part of
your car's suspension. Without going into suspension, the job of
an insert is to support and maintain the tires surface area to
the driving surface by resisting various loads as well as bumps.
For example, a soft insert used in a high grip condition is
likely to collapse causing the contact area of the tire to be
reduced, which will decrease grip and stability. Higher grip
levels will put more load on the tire, therefore, a harder
insert will usually work better. However, a rough surface with a
similar level of grip may require a medium insert. Track
temperature is also a major element that will effect your insert
choice.
|
A general rule applies with the operating temperature; soft is
for cooler temperatures and hard is for hotter temperatures. I'll
use the Reedy Race and the Roar Nationals as examples. Both of
these events mandated a spec tire, so the inserts were the only
variable. Towards the end of practice during both events, myself
as well as most of the competitors were using a medium insert
during the early part of the day when the temperature was cooler
and a hard insert during the rest of the day or when the
temperature was higher. There are a number of reasons for this;
the hard insert during cooler temperatures was too stiff and not
maximizing contact between the tire surface and the track
surface. It was also not allowing the tire to reach an ideal
temperature. Using the medium insert during higher temperatures
cause the tire to deform and overheat. Both race events
exhibited extreme changes is track temperatures during the
course of the day but are both good examples of how temperatures
can effect insert choice.
|
Another element of tires and inserts is air gap. Air gap is the
amount of space between the tire and insert. Most tires operate
best with little or no air gap but there are some tires that
work much better with a certain amount of air gap, like Tamiya's
F-1 rubber tires. Most tires designed to operate with an air gap
are belted tires because the belting resists distortion during
operation. The reason for having an air gap is similar to why
drag racers under inflate their tires; the tire surface area
increases, especially under acceleration. The advantage is more
forward grip or 'bite.' The disadvantage is less steering
response. Unlike a full size car tire, sedan tires still have an
insert that supports the tire. The insert can be changed to
adjust for the amount of air gap, track conditions and track
temperature.
|
Once you have an understanding of the effects conditions will
have on your tires and inserts, you can make educated decisions
that will lead you to the best choice for each condition. As you
experiment with tires and inserts, you'll find that you have to
compromise and the best set-up is usually the best balance. This
is what makes the R/C hobby so exciting and understanding the
basics will not only help you make better choices, but also
speed up your tuning process. This is very advantageous during a
big event where practice is limited, keeping you one step ahead
of the competition.
|
Source:
|