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New to the Shop Fitting kits International Dealers

Choosing your new kart seat

There are many factors to consider when choosing a new kart seat.
If you have had a seat in the past. Do you know the size and shape?
Does it still fit?
If not where are the gaps or pressure points?
Will the rigidity suit your new kart/engine combination?
If you are in a team will they be happy if you choose a different shape?

Choose a shape

Shape does not make as much difference as the teams would have you believe, but they will be nervous of miss positioning the seat and may want you to use the shape they are used to fitting. This is fine until the seat is not the right fit for you. An ill-fitting seat can cause a driver to damage their body or hang on the wheel, neither are good for ultimate performance.

Different shapes put in the chassis with the drivers back in exactly the same place, made with the same materials will pretty much handle the same. That said a significant angle change of the back will alter the handling especially for bigger driver and this should be looked at separately.

T11

The most common shape used now is the much copied 58 degree T11. This by far the most popular shape, it has a huge range of twenty sizes. Drivers from a 12-year-old up to a 130 kg man, are all catered for. This shape also has many special sizes that solve age old problems. WT (Wide Top) sizes have been made for drivers with a slim hips and an athletic torso, (or maybe a thick rib protector). Also, available are a series of WH (Wide Hip) sizes for drivers that end up with severe bruising in this area.

If you are not below 12 years old, not above 1.8 m or over 35, this T11 is the seat you will most likely use.

T5

The 63 degree T5 is ideal for the 8 to 12 year old drivers. The more upright seat helps the young arms keep good control and see over the wheel.

T8

The 63 degree T8 is very comfortable having leg support and a deeper side with a rounder back. Therefore, for the older drivers this shape is popular.

T9.5

The reclined 38 degree T9.5 for the very tall drivers. This can be used to good affect to lower drivers whose height makes the kart unstable on fast corners.

Choose a size

This is important as a good fit is essential for the protection of the driver and the handling of the kart. If a driver is loose in a seat he will pull to steer, pulling himself out of the kart, making it bounce at the slightest provocation.

To assess whether or not the size of a seat that you have in your possession is correct, sit the driver should in the seat and feel the gap over the leg bone, the hip bone and down the length of the ribs, from top to bottom. This must be done with any rib protection in place, but the race suit is not so important unless it has integral padding. The rib protector when worn tight, should not move inwards as the driver sits back in the seat. Once sat back in the seat, it should be difficult to squeeze your fingers between the seat, your ribs, hip and leg bones. It’s important that all the points are evenly pressured and no one element is either loose or pinching. If one area feels loose, some firm foam stuck between driver and seat is acceptable. If it is pinching you need a different size.

To assess the size without having a seat in your vicinity, we find that denim Jeans waist size, weight and height are good indicators. Coupled with information about the chest circumference and rib protector type. An over thick rib protector can make two sizes difference and leave you with very loose hips, so this is to be avoided (i.e. buy a P1) or accounted for with a WT wide top T11 seat.

Please see sizing guide here.

Choose a rigidity

Let’s start by making the first couple of sentences simple. Currently most karts either use the VG rigidity or the "t” rigidity. These are the two grades softer than standard and most current chassis/engine combinations of full size karts will use these. Most 60 cc Minikart two strokes use the softest VTi and four stroke chassis are less affected due to their torque so standard rigidity is OK.

That should be enough for most people to decide but here is a more in depth explanation.

The impact that rigidity has on the chassis are sometimes not logical. It is common for people to make the statements "I need more grip” or "I need less grip” when they are asking me which seat to buy. I tell them that seats do not give or loose grip, but by changing the seat rigidity you can displace the weight differently on each tyre and can alter the way the weight is transferred to each tyre during the corner.
Due to the different coefficient of friction available from the track surface you may get caught out if you try and equate grip with seat stiffness. For example, you can get the grip from the tyres in two ways, a large amount of tyre rubber contact, or from downward pressure onto the two outside tyres. A stiff seat will transfer the weight to the outside front tyre more, a soft one less. A soft seat will allow the rear wheel to lift more and a stiff one will keep the rear inner tyre down. A soft seat which is not transferring weight adequately to the outside front tyre can effectively cause understeer, but likewise a stiff seat keeping both rear tyres in contact with the track can push the front on and also cause understeer. The same problem caused by two completely different directions in setup.

As a tendency but not a rule, we tend to find that low powered karts (Or karts with weak bottom end torque like Rotax Max) prefer a soft seat like a VG for Max, or the even softer VTi for Minikarts. This lets the inside wheel lift more and results in the chassis coming out of the corner better with less drag from the inside wheel on the engine. Also, we find that if you have a kart with more torque such as an X30, OK or KZ the seat used more commonly is a T11t. This is because with more power and lateral forces, the inner wheel drag becomes less important and the extra weight transfer mid corner gives an advantage, as it helps put downward pressure on the front outside wheel. Strangely the stickiness of a tyre seems to have little bearing on using a soft or stiff seat.

We also have a hybrid seat specification that is stiff across the edge and soft at the front called a VGR and this keeps the back of the kart flatter but has a soft front to allow diagonal flex. Another hybrid option is the T9.5 VRS which is rigid down the two sides but has a soft flexible centre. This reclined model seems to work well with tall drivers in cool conditions.

You can get a general feel for the type of seat that generally works best in your chassis and at the tracks that you usually run on. Once set for your current setup the seat will rarely need to be changed. However, be careful about thinking that it will be correct on every track and all types of kart. It is best to keep an open mind about this subject and rely on the stopwatch.

Choose a position

Now you have a good fitting seat it is important to fit it correctly, half the weight of the kart moved 5 mm out of position will alter the balance. Over the years the average seat position has been going back in the chassis. And the average is now three cm further back than it was in the late nineties. Please see our fitting guide PDF to help with this.

Seat fitting guide