What's the deal with seats?

It's easy to look at a kart seat as just something to sit in while you can drive your kart around the track but the seat has become one of the most important tuning instruments on the kart. Soft seats, stiff seats, flat bottom, fiberglass seats, carbon seats, plastic seats, padded, unpadded, lots of choices but what matters and why? Hopefully this article can help demystify the seat.

As someone who has had hurt ribs I can attest to the fact that having a well fitting and comfortable seat is important but if your goals are performance based and not recreationally based then form is more important than comfort when picking out a seat. Buying a decent rib vest will fix most people's rib issues, especially a rib vest with hard side paneling like the Ribtect 3 or the K1 Carbon vest. If you ever have rib issues a nice rib vest would be my recommendation more so than a different seat in most instances. If the driver is exceptionally tall, probably around 6' 4" or more, then a taller seat can help with rib issues. Ribtect offers seats that are taller than a standard seat and I know of more than one tall driver that probably wouldn't be racing if it wasn't for the taller seats.

So rib issues aside, what seat do you want? If you run a particular brand of chassis (Arrow, Tony Kart, Birel, etc.) and the manufacturer recommends a specific seat (or has an OEM seat) then you should most likely run that exact seat. Most manufacturers or teams have a suggested starting spot to mount the seat and if you use a different seat then you have to guess where that seat should be and if you guess incorrectly you could fight handling issues for weeks without realizing it's an improperly positioned seat. If the seat is in the wrong spot you can change the setup all around and still not fix the issue as you try to compensate.

For a long time seat shape didn't really change but over the last 5 or 6 years flat bottom seats have become extremely popular. The flat bottom seat allows the driver to sit lower in the kart which lowers the center of gravity. On a high grip track, high grip tires or with a tall driver this can be a great benefit but I have also seen junior drivers run extremely well with flat bottom seats. When I sit in a flat bottom seat I feel like I'm more down in the kart instead of on top of the kart as with some other seat styles. There's some personal preference involved for sure and I also think the taller you are, especially from the waist up, the more likely a flat bottom seat is a better choice. Smaller drivers can be too low in a kart and adversely affect the handling.

Does seat flex matter? Absolutely. The seat is a huge spacer in the center of the kart attached in at least 4 spots and greatly affects the weight transfer and chassis flex of the entire kart. Think of the seat as a oddly shaped torsion bar. The stiffer the seat the more the kart will sit flat, the softer the seat the more the kart can flex. There is a happy medium between the two as with most things. If a seat is to stiff it will cause the kart to sit flat which can lead to either a tight kart or a kart that flat slides. Think your seat might be too stiff? If you are running extra seat braces from the top of the seat to the bearing hangers you can loosen the two bolts on the side of the seat that bolt to the main seat struts and see if your kart's handling changes. (Note: If you are not running auxiliary seat braces, loosening the side bolts will be extremely hard on your seat and the seat might crack or break.) If it improves your issue then your seat is probably too stiff. I was helping a guy with a kart that was extremely loose. We changed multiple settings with little results so we ended up loosening up the bolts on the side of his big heavy seat and the kart started working again and the flat slide went away immediately.

So what about soft seats? Soft seats are great for high grip tires and tracks as it allows the kart to transfer weight more effectively. But just like having too stiff of a seat there is a happy medium with soft seats as well. If the seat is too soft or just ragged out from years of use the seat can be ineffective at transferring weight (the wet noodle effect). The drivers mass isn't effectively transferred to the chassis and the axle which makes the kart less responsive. The other issue with too soft of a seat can be a kart that over transfers, think of it as having to soft of a spring. Also a seat that is too soft can hurt rear grip. If you think your seat might be too soft you can add bolt on seat struts to stiffen the rear of the kart and see if this helps either control the transfer of the kart better or increases grip depending on your specific setup issue.

What kind of seat material is the best? The material is actually second in importance to the stiffness of the seat. Plastic seats tend to be very soft and are best suited for recreation. They can be very durable and less prone to cracking and tearing like a fiberglass seat. Fiberglass seats are the norm and work in almost every instance and are the de facto choice for most applications. Carbon fiber seats are usually more expensive than fiberglass but can be made thinner and lighter in most cases. Most seat materials can be made softer or stiffer depending on the amount of layers and binding materials used and many manufacturers offer the same model of seat in more than one stiffness. For competition I would stick with fiberglass or carbon fiber.

Shell seat or a padded seat? As comfortable as a full pad seat can be, unless you are driving a kart for recreation and fun and not overall performance I would not put one in my kart. A full pad seat sits the driver up in the seat higher and makes weight transfer less effective as it absorbs some of the load of the drivers mass through the corner. If you must have a padded seat then keep it to a 1/4 pad seat (padding only on the sides of the seat) for competition. It won't lift the driver out of the seat like a full pad seat which I think is the biggest issue with a full pad seat. If you run a shell seat with a decent rib vest for a weekend I think pretty much any driver will be comfortable.

One thing to mention is seat sizing. Make sure you have a seat that fits you snug. You don't want a seat that is uncomfortably tight but you also don't want a seat so big you have to hang on to the steering wheel through the corners! If you wear a rib vest make sure you try your seat with the vest on. If you find a seat that fits you well in the hips but is too wide under your arms you can add a little bit of foam padding in that area. Being comfortable in the kart is a big part of going fast and that comfort starts with a properly fitted seat.

Mark Dismore Jr.