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Seat Position - It's not about driver comfort

Seat Position - It's not about driver comfort
Category: Comet Technical Karting Blog
Posted: 05-10-2014 11:28
Synopsis:

Seat position and its effects on the karts handling


We’ve discussed a number of factors that affect your kart’s handling on track in previous blog posts but it’s all pretty much a moot point if the seat isn’t mounted in the right spot. The seat, as we discussed in this article, is a huge part of what makes the kart work (or not work).

So where does the seat need to be? Well it all depends on the class you run. In a TaG kart you need rear grip and a seat that is further back will increase rear weight percentage and move the mass (the driver) more over the rear of the axle. In a class like Yamaha Can you typically want less rear percentage to help free up the rear of the kart since you have less horsepower. Too far back and the mass of the driver doesn’t allow the kart to pick up the inside rear tire through the corner properly. The more grip a track has or the stickier the tire the more likely the seat needs to be further forward.

Another variable is seat angle. On a flat bottom seat you basically mount the flat bottom, “flat”. That will give you the proper angle. On a more rounded bottom seat it takes a little more measuring and some experience. I’ve measured quite a few seats in the past and the seat angle where your upper back would be typically falls around 55-57 degrees. The higher the angle the more upright the driver and the more side bite the kart will have. If you are a bigger driver or on a high grip track the lower you want the seat angle but make sure you check your rules. Many organizations have a minimum rear seat height as measured from the ground.

Yet another variable is the height of the seat from the bottom of the frame rails. The bigger you are, the stickier the tire and/or the track the more likely you will want the seat mounted below the main rails. In my experience you don’t want to go more than 8mm below the rails or you’ll be buying a lot of new seats or fiberglass repair kits! 5mm below seems to be a safe number if you want the seat below but not “too” low. Now the inverse is raising the seat up from the bottom of the rails. A good way to accomplish this is to stack aluminum 219 sprockets under the seat to raise the seat up for a smaller driver when you mount it. For a small junior driver 2 to 3 sprockets can usually get the job done but I’ve seen seats mounted ABOVE the main rails for very small drivers!

Sometimes you will see a seat mounted crooked if you are looking down on the seat from above. The left side of the seat (drivers left) will be further forward than the right side of the seat. Cocking the seat to the left will move the mass of the driver slightly towards the brake and may improve braking. If there is an effect it is small but you will see a number of people mount their seat like that. The difference left to right is typically in the 5mm range, 10mm max.

It’s not really possible to give seat measurements in this article because most karts have a specific spot where they work the best for a given class and different seat models and sizes will change these numbers. I would start with the recommended seat position either given by the manufacturer or from a reputable shop or team that runs that particular kart in the class you are running. That will give you a good baseline and you can make adjustments from there.

In general (and remember the opposite direction will do the opposite to the handling) –

Further back the seat the more rear grip.

If you need to free up the kart move the seat further forward, 10mm at a time is usually a good number.

Higher the seat above the rails the more grip the kart will have.

The higher the angle of the seat the more grip the kart will have.

The smaller the driver the more likely the seat will need to be more upright and higher in the kart.

If you are at the track and you have changed axles, the front end, moved this and that and still can't find speed the problem might be the seat position. It's a huge part of the kart's setup and understanding more about how the seat affects the karts handling will help you as you progress in karts.

Mark Dismore Jr. 


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