Indy Project Sled - Lightweight Brake Hub and Rotor

Nov. 01, 2005 By Rob Schley
Cost: Around $100 (US)
Risks: Minor
Benefits: Improved braking
Tools Required: Basic tools, snap-ring pliers
Parts Required: Brake hub and rotor
Mechanical Skill Required: Average "shade-tree" mechanical skills

Elsewhere on the Off-Road Snowmobile site, you'll find an outstanding article written by Rob Schley that explains the physics behind rotating mass. Rob understands it and explains it better than I ever could, but in a nutshell, the farther away from the center of rotation mass is, the more power it takes to move. For instance, a titanimum shaft will save as much weight (maybe more) than a lightweight brake hub and rotor, but since the shaft is smaller in diameter, the power required to spin it is less and even though the overall weight savings is comparable, the effect on accelleration is not as pronounced.

However, if all you are looking for is improved accelleration, you probably will not want to go to the work and expense of installing a lightweight brake hub and rotor. It's a lot of work. But there are other benefits like better braking and cooler operation due to the improved material of the new rotor. The overall weight saving was just about one pound. I can't say that it translated into noticably quicker accelleration, although I can look at Rob's chart and state unequivocably that it now takes less power to spin the brake hub and rotor on my sled, so more horsepower is getting to the snow. I can also say that I can tell a noticable difference in brake lever effort, as stated above and that I have very little worry that my brake will overheat even when riding hard.

IMO, this is a mod for someone who is really serious about only using the very latest and greatest components in their sled, it will not provide a dramatic improvement in any aspect of your sled's performance.

Installing just a new brake hub and rotor by itself is a huge job. If like me, you have the chaincase off for some other reason, now is the time to put the hub and rotor on. Unless you like completely dismantling the drivetrain of your sled, I'd recommend waiting for some other occasion to put on a new brake rotor.

Removing the chaincase is detailed in the section on rolling the chaincase, so I won't repeat it here. Once the chaincase is off, putting on a new hub and rotor is fairly easy. All you need to do is remove the snap-ring that holds the hub on the jackshaft and slide the old hub/rotor off. Take a moment to clean up the shaft and key before you put the new hub on. I used a little disk brake lubricant on the key and the jackshaft before I put the new hub on. Then put the snap-ring back on (use a new one) and you're done.

Except. Unfortunately this turned out to be not quite a "bolt-on" for my sled. Apparently the hub is intended for newer Indys and the fit on the jackshaft was not quite right. I had to remove about 1/4" from the inside edge of the hub to get the rotor located correctly on the shaft. It's a minor issue, the kind of thing you learn to expect when working with aftermarket parts, but you need to be aware of this before trying to reinstall the chaincase.

Also, getting the rotor mated to the hub is not as simple as putting the together and putting in a few bolts. The rotor is a very tight fit on the hub. I heated the rotor, slowly, in the oven to about 250 degrees and then put it on the hub. It still didn't exactly slip on, but did required a little persuation. I used aircraft-quality button-head bolts to attach it. Northern Lites sells a hub/rotor combination bolted together with titanium bolts, you might be able to buy the just the bolts from them, or you could buy their hub/rotor and skip the mating step altogether.

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