Monday, April 20, 2015

Avanti Inc 3: Shimano RT81 Ice-Tech Centerlock Rotors

Continuing from Part 1 of this brake upgrade, where I upgraded to Shimano Deore M615 hydraulic brakes, I will now upgrade the brake rotors too! By changing to new brake rotors at the same time as new brake pads, this eliminates the risk of contaminating the new brake pads with residue and oil from the old brake rotors.

The stock brake rotors on the Avanti Inc 3 are Shimano RT64 brake rotors. These are mid range (SLX-Deore class) disc rotors that are found on many bikes with Centrelock brake rotors. Before installing the new rotors, I will have to first remove these rotors from the hubs. This is the first time that I am removing the brake rotors ever since I bought the bike 1.5 years ago.

Original RT64 Centrelock brake rotors

To remove this Centrelock brake rotor, I will have to first remove the lockring in the middle. This is not a 6 bolt rotor which requires loosening 6 individual mounting bolts.

As shown from this illustration, removing the rotor lockring requires the use of a tool for lockring removal. This is the same tool as cassette lockrings, so no special tool here.

Nevertheless, I took the chance to get a new lockring tool. This tool can be used for both cassette and Centrelock rotor lockrings. It also comes with a central pin for alignment with the hub axle.

This tool is good because the lockring tool is already attached to a handle, which means no need to insert and align the tool within a separate wrench. This makes it much easier to apply force to the tool without the risk of the wrench slipping away from the tool.

As you can see here, the cassette lockring tool can also be used for the rotor lockring. However, the rotor lockring and the cassette lockring are not interchangeable.

Ready to remove the rotor lockring! It is really easy with this tool.

The braking surface vs the untouched surfaces on the old rotor. The braking surface can be seen to be much darker in colour and more worn out.

The replacement rotor that I decided to get is the RT81 (Deore XT grade) Ice-Tech rotors. These are Centrelock rotors (to match my Centrelock hubs), and they have an aluminium layer sandwiched between the steel braking surfaces for better heat dissipation. Honestly speaking, I have no need for better heat dissipation as I am not going fast enough or braking hard enough to actually accumulate too much heat in the rotors. What I like is the large 5 arm aluminium spider in the middle of the rotor which looks really good (much like the 5 arm design on the Ultegra 6700 crankset).

Comparing the RT64 rotor on the left with the new RT81 Ice-Tech rotor on the right. The main difference is the size of the aluminium spider in the middle of the rotor.

Steel lockring from the RT64 rotor vs the more lightweight aluminium lockring from the RT81 Ice-Tech rotor.

Weight of the RT64 rotor + lockring is 157 grams...

...while the RT81 Ice-Tech rotor + lockring is 129 grams. The weight savings is partly due to the large 5 arm aluminium spider.

Smart looking Ice-Tech rotor! New and shiny.

160mm diameter rotor with Ice Technologies

Model number is SM-RT81-S. The "S" stands for small which is 160mm. There are also 180mm (M) and 203mm (L) sized rotors.

Lightweight aluminium lockring from the RT81 Ice-Tech rotor

The nice looking 5 arm aluminium spider in the middle of the RT81 Ice-Tech rotor

If you look closely, you will be able to spot the aluminium layer that is sandwiched between the outer stainless steel layers.

I took the chance to remove and reinstall the tires (the tire tread was facing the wrong way, ever since I changed to Schwalbe Marathon Supreme tires), and weighed the wheel. The weight of the front wheel alone (without rim tape, tube, tire or brake rotor) is 1124 grams. This is a heavy front wheel!


RT81 Ice-Tech rotor installed on the front wheel!

As for the Alfine 11 internal hub rear wheel, I also weighed it (without rim tape, tube, tire and rotor), and it is a massive 2711 grams! This is so much heavier than the Ultegra 6800 rear wheel (940 grams).

While changing the brake rotor for the rear wheel, I discovered this rotor spacer underneath the lockring of the stock RT64 rotor.

This is because the Centrelock serration is further in on the Alfine hub than standard MTB hubs

Without the rotor spacer, the lockring cannot reach the rotor at all to tighten it.

This is why the rotor spacer is required, to act as an intermediary for the lockring to tighten onto the rotor spider.

With the rotor spacer, the lockring can now be tightened properly onto the rotor.

RT81 Ice-Tech rotor successfully installed onto the Alfine 11 internal hub!

Another view of the rotor on the Alfine 11 hub

Black coloured rotor spider is not really visible when placed against the black bike frame

RT81 Ice-Tech brake rotor as seen mounted on the front wheel

Both the new rotors have been successfully mounted on the Avanti Inc 3 bike! Adjusting the centering of the brake calipers is also easy, as the rotors are nice and flat without warpage. However, I did notice some issues with the clearance between the rotor and the brake caliper.

As can be seen from the two pictures below (showing front and rear brakes respectively), the two red arrows point to the clearance between the rotor and the brake caliper. Due to the large aluminium spider on the rotors, there is very little clearance between the spinning rotor and the caliper body of the brake calipers. From my estimate, there is barely 1mm of clearance between these parts.

Minimal clearance between the rotor spider and the brake caliper on the front wheel

Same situation for the rear wheel

Although the clearance is very small, I did not notice any interference between the rotor and brake caliper when I spin the wheels. After test riding the bike, I also did not notice any abnormalities caused by the small clearance. Thankfully there is no problem, but I am not so comfortable with this setup as the clearance is really small.

Since there is no problem now, I will leave it as it is. There is always the option of adding a washer underneath the brake caliper mounting just to put it a little bit further from the rotor.

With the new brake rotors and the new brakes, the whole braking system on my Avanti Inc 3 is completely new. As with a new rotor or brake pad, there is always a settling in period where the braking performance will gradually improve as everything is worn in. This process can be accelerated by some hard braking.

Once the brakes have attained their full performance, I found that the braking power has been noticeably improved compared to the previous stock setup. I also had to get used to the new, shorter brake levers which affects the braking feel and ergonomics. Overall, I am happy with this new setup as I get shiny, good looking new rotors and improved braking performance.

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