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Place a board under the chassis Pay careful attention to seat alignment
kart the seat is cupped to hold the driver from behind, from the sides and
from the front. A good seat should hold the driver firmly and support the
hips. Most seats will have a spine relief in the form of a groove down the
back to keep pressure off the driver’s spine, making it more comfortable.
Seats can be purchased fully padded, partially padded or not padded at all.
Your seat choice is based on increased comfort versus weight savings.
The front mounting tabs are welded to the first cross member, just
behind the fuel tank and usually in line with the steering column supports.
They are generally positioned about five to six inches apart, or the width of
the fuel tank. This keeps the front of the seat in position and provides a solid
attachment point.
The side mounting supports hold the seat in place from both the left
and the right sides. These supports are attached to the side rails and to the
rear cross rail. Some chassis manufacturers use a right side support that
can be clamped on, allowing you to position it where it fits best. Again, the
manufacturer defines much of this.
Most seat struts are made from tube steel with the ends flattened to
allow for flush mounting. Some are made from round stock while others use
flat tubing. Seat struts are extremely important to the overall performance
of the seat and the kart. It is through the struts that the weight transfer from
the driver is connected to the rear wheels. Loosen or remove the struts and
the weight transfer effect will diminish.
Seat Installation
We will now go into the process of seat installation and anticipate some
factors that you may encounter while installing or repositioning your seat.
Before you begin you will need to get your tools together. You will need a
drill, preferably cordless, a 15/64” (6mm) drill bit for the M6 bolts and a
5/16” (8mm) drill for the M8 bolts. Also, you will need M13 and M10
wrenches, along with T4 and T5 hex head sockets or T-handles.
Make sure you have the proper hardware before you get started. All the
nuts need to be Nylock style so they do not vibrate loose. The bolts should
be the countersunk, flat head variety. These bolts use a special washer that
makes for a smooth surface on the seat and distributes the pressure over a
wider area to prevent cracking around the boltholes.
Use a lead weight to support the
seat at its natural angle
The first consideration when installing the seat properly is to ensure
that you do not pre-load the chassis with tension. If the bolts are out of
alignment, or the seat has to be pulled or twisted into place, it will put
pressure and tension on the chassis before the kart even gets rolling. This
will greatly affect the flex and the tuning consistency of the kart.
Start by putting your kart up on the stand. Next, place a wide piece
of wood under the frame from side to side just forward of the side seat
supports. Spring clamps work great; be careful not to scratch the chassis
finish. Make sure that there are no tye wraps, engine mounts or struts in the
way. Have a couple of pieces of eighth inch stock on hand. These shims may
be placed under the rails, lowering the board, if you are a tall driver, not used
at all if you are medium height and placed on top of the board, raising the
seat, if you are short. However, this does depend on the grip level you will
encounter as in high grip conditions a short driver can set the seat as low as
possible and gain an advantage over the taller competition.
Set the seat in place and center it between the side seat posts. If there
are excessive gaps on each side bring the side supports closer together. You
will need a long pipe that can go over the seat support or fit in between the
support and the side rail to bend it back. Remember, you do not need to
move the pipe very much to move the support and you want to bend the
tube slowly and not all in one spot.
For karts with one fixed and one clamped side support, place the seat
centered on the steering column support with the proper angle. Check the
space between the seat and the fixed left side support. If the gap is big move
it in (or out if the seat cannot be placed properly). Once you have this fixed
support set, put the clamped support in place and snug the bolts. You may
need to cut the post to fit. Ideally the seat mounts will attach to the seat at
the same place on opposite sides. Be careful placing the clamped-on support.
As you tighten it, the angle may change. Make sure it is flush when you set
it in place.
The seat spacers can be made from aluminum or hard plastic. Never
use soft rubber spacers as they do not allow the seat to flex correctly during
cornering and can split apart when being tightened. Edge cracks in the seat
are common when seats are mounted with spacers made of an extremely
flexible material like rubber. It is important to use the same type of spacers
for both sides. This will keep the seat mounting symmetrical and help the
kart to perform the same in both left and right turns.
In the next installment from Memo Gidley’s Secrets of Speed for Four-
Cycle Kart Racing we will finish off the kart seat installation and look at a
base line set-up.
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go to www.mgspeedsecrets.com
Go Racing Magazine Page 45