KARTING BRAKES
By Vahok Hill
From the very beginning, karters seemed to focus more of their attention on the go portion rather than on the stopping portion of kart racing. Brakes have seemed to take a back seat to the power plants and chassis in the search for speed. This all started to change as tires became better and offered the karter more grip. Then in the middle to late 1970’s and early 1980’s when European karts manufacturers invaded the domestic racing scene, brakes began to get more attention.
From a historical perspective, karts have evolved from utilizing braking systems that were a simple scrub brake (a metal plate that was pushed into the tire to slow it down or the deluxe versions, used a metal plate with an old tire bolted to the plate so there was a rubber to rubber contact area to generate even more braking friction), to the four wheel hydraulic brake systems we have now. If you have been in karting for any period of time, the brake systems have seen a level of development and improvement over the past 5 years that has out paced the development over the past 35 years. From a braking perspective we are in braking Nirvana.
As the need for better, more performance oriented brakes was more and more apparent, there was a progression from the scrub brakes to the next step which was the Bendix Drum brake. This was a smaller version of the drum brakes that were on the cars back in the day. They were still very large, about the size of the brakes on a VW Beetle, the old beetle. They were simple, heavy, chrome and they worked a ton better than the scrub brake. The brake consisted of a rotating drum attached to the axle and the shoes and backing plate were attached to the frame through some simple bolt on brackets. The two shoes in the brake were forced into the drum via a mechanical linkage. That’s right the brakes were mechanical just like the scrub brakes or brakes on a Model A. The next quantum leap in brakes, were disc brakes. The first disc brakes were a mechanical disc brake. These were manufactured by the Airheart who later became Hurst-Airheart and is now just Airheart again.
These brakes started out life as a part of a large industrial turning machine, we are more accustomed to calling them lathes, but these brakes were originally used to stop lathes. But for a number of years the Hurst Airheart brake was the standard in the industry. They made two different sized calipers a 150 and a 175 (larger of the two sizes). By today’s standards these brakes are not even in the same league. But at the time when Mac’s were the engine of choice they were the standard and they were cutting edge.
The next revolution was the brakes offered by Enginetics, they offered a very simple well made and very robust caliper. The racer could adjust the gap between brake pads and the disc by adding or removing shims that would either move the caliper halves closer together or further apart. This was a quantum leap in adjustability for the karter. Now we could adjust the spacing between the disc and the pads to “tune” the brake for the feel that the driver wanted. This brake was the standard for every American made kart with the exception of Invader who made their own caliper out of bar stock and used modified automotive pads. But the Enginetics master cylinder seemed to be on every kart at the track through the end of the eighties.
This was followed by Martin Custom Products, another American company, started by an ex-employee of Enginetics. Paul Martin decided he could build a better product than his former employer, which he did, and he was off and running. They now seem to dominate the American karting market, especially in the dirt and oval market. With a very well made system that gives the karter a very large series of options, pads, disc types and they have also a front brake system.
The Modern Era
With the advent of the very large penetration of European karts, mainly Italian made karts, the number of brake choices for the karter is even larger. Every brand of kart seems to have their own take on brakes and the parts are not interchangeable from one brand to another so for the kart shop owner this is a positive from a sales perspective, but a negative from an inventory perspective. For the karter, this means that he or she may need to keep more parts in their own selection to support if they have more than one brand of kart they use in their racing arsenal.
The science of brake design and developing brake technology is more about the materials used in the manufacturing of the brake rather than any new or fundamental changes in the mechanics of the brakes. The basic design parameters are pretty much set for the karter. There is the possibility of using a brake pack similar to what is used in large airplanes. Think of a design very similar to a Horstman engine clutch, but instead of being designed to transfer power to accelerate the kart the same type of clutch pack is used to slow the kart. The problem is that the materials required for that type of clutch would be much more expensive than the simple cast iron and composite friction materials and aluminum castings used today. And this type of brake system has some other shortcomings. They require a good bit of maintenance. Where one of the greatest assets that the brakes on karts have is the “almost” maintenance free designs. It is truly amazing the amount of abuse and lack of care brakes on the modern kart have been known to take. Some karters have never been known to never work on their brakes until there a real pressing need, such as they no longer work. It is not uncommon that a kart that is raced 25 to 30 times a year receives very little maintenance to the brake system. This is a true testament to the level of material selection and design work and resulting robustness in the modern karting brake. It may not point to a very good maintenance program, but sometimes the truth is the truth. The fact of the matter is that the kart chassis may be well past its duty cycle long before the brakes wear out or require any replacement of the mechanicals.
There are multiple well known automotive brake manufacturers that have made runs into the karting market. Some of these companies are very well known automotive racing brake manufacturers. Companies such as Brembo, Wilwood, Alcon and Kelgate have all made forays into the karting market. These are companies that are more recognizable or known for high end automotive racing brakes rather than for applications suitable for the kart racing community.
The one common thread between the automotive and motorcycle braking world that is completely transferable to karting is that tires are the weak link in the braking chain. If you are running a hard tire, the brakes will not be able to perform to their maximum performance levels. It is much easier to develop a much greater mechanical load in the brake system than the tires are able to contribute grip. It is very easy to overpower the tires with the brakes. Push the pedal too hard and you will lock up the brakes. There are ways we can control the power to the brakes, the simplest is to not push as hard and use the onboard computer under your helmet and modulate the brakes based on the feedback you get from the pedal and the sensation the kart gives you via the seat when the tires lock up. When the tires lock up the ability to slow the kart in a controlled method go right out the window. By balancing the sizes of the bores in the master cylinder and the slave cylinders in the calipers we can tune the brakes to give us more control. This is usually accomplished by the kart maker, but the option still exists for the karter to look around and play with different master cylinders and calipers to custom tune the brake system to the driver.
The disc is another component you can tune to tailor the brake system to suit your individual needs. Karters have made discs out of everything from Detroit wonder metal, Cast Iron, Steel plate, Aluminum and even exotic metals like Titanium and Beryllium. But the material of choice seems to always gravitate back to Cast Iron. Nothing seems to be able to beat this material for it ability to under go many heat cycles without distorting. It is relatively inexpensive and it has great wear capabilities. Carbon-Carbon was even tried for a short time. It offered great performance and it was incredibly light often the disc would weigh less than the nuts and bolts used to hold the disc to the hub. But it was very expensive; really expensive, a single disc could cost $200.00 to $500.00 dollars depending on the application. The Carbon-Carbon disc also required special Carbon-Carbon brake pads so the cost was really astronomic, but they did work very well in heavy high powered Sprint Karts like shifters, that would really place a real strain on the brakes especially in street races.
But no matter how much things change, they still seem to be the same. Cast Iron is the material of choice and that holds true in 90% of the racing series around the world, not just karts. You will only find the esoteric Carbon-Carbon brakes in the highest formulas racing today like Formula 1.
For the most part, the brakes that were delivered with your kart as new will perform beyond your expectations, last longer, and provide trouble free service over the life of your chassis with a very little care and or maintenance. Today the karter is getting a better more completely designed product than they have in the previous years. It does not matter if you are using a domestic or an imported brake you can expect many seasons of dependable trouble free high performance braking. Keep the fluid clean, the pads in good condition, the hardware secure and in good condition, keep and route the brake lines away from the track surface or any other moving surfaces and the brakes will probably out last the chassis. If you follow those some simple maintenance steps you will most likely never have any real issues with your brakes. Remember take it in deep, trust your brakes and we will see you on the podium.