Tony kart brakes boiling

John Matthews · Posted: Wed Sep 19, 2012 5:57 am Post subject:

Great article with lots of good tech info.

Since the OP hasn't bled his brakes for a long time the statements about boiling points and silicone not mixing make perfect sense. All it takes is a little water at the bottom of the system i.e. calipers, which isn't mixed with the brake fluid due to the silicone not absorbing it to boil at 212 deg F. and cause the problem described. If changing the fluid fixes the problem you have your answer.

But, if I had a TonyKart designed to run Dot 5 I would seriously think about changing the seals and switching to Motul 600. Although I haven't used everything out there it is the best brake fluid I have used.

As for why Tony switched to Dot 5 I can't say but they wouldn't be the first manufacturer to attempt to increase profits by selling repackaged consumables....

Cheers,
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John Matthews
Heartbeat Power, LLC.

Steve Buckner · Joined: 22 Apr 2003 Posts: 839

Yea, That is what I was thinking John, on the boiling point change. I just thought it was a very good informative article. Yet, I dont own a kart shop or sell Tony karts or have ever raced a Tony Kart, so I could be wrong. What is said in the article made a light go off in my head, that could be his prob. Idea

Rich Hays · Posted: Wed Sep 19, 2012 7:49 am Post subject:

Steve Buckner · Joined: 22 Apr 2003 Posts: 839

Yep, the boiling point and water was different back then. Confused

Steve Buckner · Joined: 22 Apr 2003 Posts: 839

To continue to belabor the silicone brake fluid question … Just discovered a brochure in my pile of karting information from the Ripley Engineering folks … they make braking systems for karts. Here’s what they say about silicone brake fluid: “unsuitable for racing applications (for these three reasons): 1. At approximately 275 degrees, the additives used to compound silicone fluid begin gassing off resulting in air in the lines. 2. At elevated temperature, silicone fluid has four times the compressibility of glycol-based fluids (leading to) increased pedal travel and a spongy pedal. 3. At elevated temperatures, silicone brake fluid will expand significantly. ”

Your mileage may vary.

Rob Kozakowski · Posted: Wed Sep 19, 2012 10:34 am Post subject:

One thing to understand about Dot 5 is that it is not necessarily spongey.

Dot 5 CAN be spongey if it is exposed to high temperatures. While we may think that karting produces high brake temperatures, our brake temps are nowhere near what you'd get in most motorsports applications because karts weigh so little and our speeds are generally lower than you'd find in most racing applications.

Yes, in some ways, the performance of a shifter kart is the closest thing to an Indycar or F1 you can find. And although those are relatively light-weight vehicles, they still weigh a lot more than karts, they stop from much higher speeds, and their brakes are exposed to more heat being packaged inside the wheels, whereas ours are sitting out in the air thus making them much easier to keep cool because we don't worry about aero in our packaging.

We're definitely not racing stock cars or full-sized production-based cars with all their weight.

The second thing about Dot 5 is that while it doesn't absorb water, moisture can and will still get into your brake system. With Dot 4, the water mixes in with the brake fluid, lowering the boiling point of the mixture of brake fluid and water. With Dot 5, the water will "pocket" on its own, basically making for 2 different boiling points in your braking system. So, while Dot 5 has higher boiling points, if water is in there in any significant amount, the water can still be a problem boiling on its own.

Brake fluid should be changed periodically/regularly ESPECIALLY for racing, regardless of the type of fluid used in your system. Dot 4 has a lower boiling point to start with and it decreases with more water. Dot 5 has a higher boiling point, but the "pocketing" of excess water can become problematic.

If your fluid is boiling it is likely either due to unusually high water content (old fluid or poor seal somewhere in the system allowing unusually high amount of moisture to enter the system) or improperly adjusted/shimmed rotors/pads that are rubbing and creating abnormal heat.

All that said, there's absolutely no reason not to use Dot 5 in kart racing applications.

Rob Kozakowski · Posted: Wed Sep 19, 2012 10:34 am Post subject:

delete - double post

Rob Kozakowski · Posted: Wed Sep 19, 2012 10:37 am Post subject:

http://kartdrome.com/index.php/technical-documents/brake-fluid-overview

An article about brake fluid and karts.

Bruce Jackson · Posted: Wed Sep 19, 2012 5:39 pm Post subject:

This has been an informative thread regarding Kart brakes, which is possibly one of the least understood components found on a kart chassis. In our case, as I just found out, the guy that was doing the tuning that weekend had added DOT 3-4 fluid to the system, which resulted in brake failure within just a few laps into the main. Thanks for all the input everyone has provided, I'm sure those who followed the thread will benefit from it.

Bruce
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Bruce Jackson

Steve Buckner · Joined: 22 Apr 2003 Posts: 839

Thanks for letting us know what the prob was. As you said, it helps a lot for other drivers that may make the same mistake.