Tuesday, January 10, 2017

Shimano Dura-Ace 7900 vs Shimano Dura-Ace 9000: Crankset

I recently got the Dura-Ace 7900 crankset from the Rodalink online store at a great deal. This gives me a chance to make a detailed comparison between the Dura-Ace 7900 crankset and the Dura-Ace 9000 crankset.

First of all, the 7900 crankset is designed for 2x10 speed drivetrains, while the 9000 crankset is for 2x11 speed. Strictly speaking, these cranksets are not cross compatible as the front shifting performance will not be ideal. However, many people have used these cranksets interchangeably across 10 and 11 speed drivetrains with no major issues.

What I have for comparison is a Dura-Ace 7900 crankset, with 53/39T and 165mm crank arm length. As for the Dura-Ace 9000 crankset, it is 50/34T, with 170mm crank arm length. As such, the total weight comparison is not the most accurate as the specifications are slightly different.

Dura-Ace 7900 crankset, with 5 arm design and 130mm PCD.

Dura-Ace 9000 crankset, with an asymmetrical 4 arm design, and a 110mm PCD

Super polished 7900 outer chain ring, together with dark grey matte anodising.

Polished silver and black anodising on 9000 chain ring. Black inner chain ring with a silver band.

7900 crankset, with surprisingly few shifting pins and ramps. Another look at the silver inner chain ring teeth.

9000 crankset, with more shifting pins. All black inner chain ring.

Inner view of the 7900 crankset with 39T chain ring

Inner view of the 9000 crankset, with 34T chain ring

7900 crank arm with rounded edges, hollow forged in one piece.

9000 crank arm is wider and has a more rectangular cross section. Bonded from two separate pieces.

Left side crank arm comparison. The 9000 crank arm is significantly larger in terms of width.

Another look, comparing the rounded edges of the 7900 crank arm with the sharper edges of the 9000 crank arm.

7900 left side crank arm has the logo facing the right side up when the crank arm is facing to the back, while the 9000 crank arm is the other way round.

7900 crank arm with a hollow and open 5 arm profile

9000 crank arm with a hollow but closed 4 arm profile

Weight of 165mm left side 7900 crank arm

Weight of 170mm left side 9000 crank arm. If I'm not wrong, this weight will be the same as the 165mm length, as the arm is the same, just that the pedal hole is drilled at a slightly different place.

Right side crank arm of 7900, 319 grams  

53/39T chain rings of 7900, 145 grams 


Right side crank arm of 9000, 306 grams. Lighter than 7900.

50/34T chain rings of 9000. Lighter mainly due to smaller size.

Comparing the arm construction of 7900 (left) vs 9000 (right)

Side by side view of 7900 vs 9000 right side crank arms

Right side of the 7900 crankset with 53/39T chain rings and 165mm crank arm length weighs 465 grams.

Right side of the 9000 crankset with 50/34T chain rings and 170mm crank arm length is lighter at 440 grams. The lower weight is from the smaller chain rings and also lighter crank arm.

Total 7900 crankset weight is 643 grams

9000 crankset weight is even lower at 615 grams

Side by side comparison of the different chain rings. Note that there are many cosmetic and construction differences.

Final picture for crankset comparison. Both the 5 arm and the 4 arm designs are iconic and special in their own ways.

Other than the difference colour schemes, there are also major differences in how the crank arms are made, and how different parts of the crankset are constructed. Both are lightweight and look extremely high end, with exceptional surface finishing and high quality manufacturing.

Wednesday, December 28, 2016

Merida Scultura 5000: Dura-Ace 7900, 165mm Crankset

A lot of times, the reason for me getting new bike components is due to a combination of a few factors as listed below:

1) Want to try out component with new feature
2) Discount on website
3) Replacement for worn out component
4) Upgrade on existing component
5) Improve fitting on existing bike

In this case, I decided to get a new crankset because of reason 2 and reason 5. I came across this article regarding the bio-mechanics of cycling, and it discussed the crank arm length in detail. Seems that most bikes in the market are actually equipped with crank arm lengths that are too long for most people.

Link below:
http://bikedynamics.co.uk/FitGuidecranks.htm

In summary, for a person with height of 168cm (me), I should be using a crank arm length of 165mm. However, I have been using crank arm length of 170mm for as long as I can remember, due to the fact that it is the default length for most bikes in my size, and is also the most common length available.

Although I don't have a problem using 170mm crank arm length, I feel that when I am in the drops on the Merida road bike, it feels like my hip angle is too small when my knee is at the top of the pedaling stroke.

At the same time, I also came across a great online offer from Rodalink, where they are selling the Dura-Ace 7900 crankset for only $200+, when it usually costs $600+. The catch is that it is 53/39T, and also has 165mm crank arm length. Most of the time, people will not buy a crankset with 165mm crank arm length. However, in this case, it is perfect as it gives me a chance to test out a shorter crank arm length, and I am also getting a great deal on a Dura-Ace crankset.

Although this Dura-Ace 7900 crankset is 2 generations old, having already been replaced by the newer 9000 and R9100 series, it is still iconic, with the two-tone surface treatment and integrated chain ring appearance.

With that, I ordered the Dura-Ace 7900 crankset with a 165mm crank arm length, and will install it on the Merida Scultura 5000 to try out.

Since the crank arm is 5mm shorter, it also means that I can raise the saddle 5mm higher, and still get the same leg extension at the bottom of the pedaling stroke.

Current setup on the Merida road bike. Dura-Ace 9000 crankset with 170mm crank arm length.

With the Dura-Ace 7900 crankset, one difference is that 7900 is for 10 speed, while Dura-Ace 9000 is for 11 speed. There is a small difference in distance between the chain rings, but it should not affect the shifting performance greatly.

Let's take a look at the new (old?) Dura-Ace 7900 crankset!

Unboxing the Dura-Ace 7900 crankset! Always a wonderful experience

Iconic 5 arm crankset with integrated chain ring appearance

Polished aluminium! Still so shiny even after a few years of storage.

Weighs only 643 grams for the whole crankset. The weight is in between Dura-Ace 9000 and Ultegra 6800.

During installation, I found that I had to move the front derailleur upwards, as the previous setting was for the 50/34T crankset, while this Dura-Ace 7900 crankset has 53/39T. Also, the chain had to be lengthened due to the larger 53T chainring. Not a straightforward crankset swap due to the different chain ring sizes.

Installed on the bike, with the Ultegra 6870 Di2 FD moved upwards

Swapping a Dura-Ace crankset for another

Installation completed!

After testing it out for a couple of months, I found that there is some difference in the pedaling stroke. When using the drops, the knees will not come up as high, and the hip angle is not so tight, making it more comfortable when using the drops. When using the hoods, there is no noticeable difference as the hip angle does not get so tight.

Although there is a difference, this difference is quite small, and I am comfortable with using either 165mm or 170mm crankarm length. Perhaps for long distance riding or high cadence riding there will be a difference over longer periods of time.

In conclusion, using a shorter 165mm crank arm length will make a difference only if you are using the drops frequently, and if you are concerned with getting maximum pedaling efficiency and perfect bike fitting. Otherwise, it is OK to stick with 170mm crank arm lengths for most purposes.

Sunday, November 6, 2016

Avanti Inc 3: Ice Tech Disc Brake Pads

On my all-weather commuting bike, the Avanti Inc 3, the disc brakes have been giving out some noise recently. Upon braking, just when the bike is about to come to a stop, there will be a loud squealing noise coming from both the front and rear brakes. This means that it is time to service the brakes!

Usually, when there is a squealing noise from the brakes, it means that the brake pads or brake rotors have been contaminated with oil. Most of the time, this contamination comes from the dirt and oil on the roads, which is unavoidable. Other sources would be from dirty hands touching the brake rotor, and in rare cases, a leaking hydraulic brake.

Front Ice Tech rotor SM-RT81 which was installed 1.5 years ago.

The black marks on the braking surface are tell tale signs of oil on the rotors or brake pads.

Same rotor used on the rear Alfine 11 internal hub

The rear rotor also has black marks on the rotor braking surface

The standard procedure for cleaning the brake pads and rotors are:

Brake Pads:
1) Remove brake pads from brake caliper.
2) Wipe clean brake pads with isopropyl alcohol.
3) Sand off top layer of brake pads, to remove glazed or contaminated layer.
4) Clean with isopropyl alcohol again.

Brake Rotor:
1) Remove brake rotor from hub.
2) Wipe clean brake rotor with isopropyl alcohol.
3) Sand off surface of brake rotor. This removes the scratched surface of the rotor and "resets" the microscopic surface of the rotor.
4) Clean with isopropyl alcohol again.

This usually works to eliminate the squealing noise of the brakes as both the brake pad and brake rotor surfaces have been restored. At the same time, this also means that there is a need to break in the brake surfaces again, in order to get proper braking force.

However, I decided to change the brake pads to new Ice-Tech disc brake pads, as I wanted to see how the finned brake pads will look. I had gotten these brake pads long ago, but did not change them earlier as the original brake pads from the brake calipers were still working fine.

Now that the original brake pads are getting old, and are contaminated with oil, it is the perfect chance to change to these Ice-Tech brake pads.

Shimano Ice-Tech Disc Brake Pads, with finned surfaces to help keep the brake temperature low.

Compatible with the models as listed above. Each set is for 1 brake caliper, so you need 2 sets for a bike.

These are resin pads, and come with the parts as shown.

Weigh 22 grams for the pair of brake pads

The aluminium fins of the brake pad backing are exposed to air, acting like a heat sink to quickly transfer heat away from the brake pads.

Brand new look before installation.

Original look of the brake caliper with standard brake pads...

...new look with the Ice-Tech brake pads! Looks more aggressive with the finned brake pads.

From further away, these finned brake pads are not that obvious though.

Same for the rear, the picture before the change...

...after the change! Not much difference la...

Nice look when in close up

When viewed from far, the finned brake pads are not really visible

In this case, there is no need for finned brake pads on this Avanti Inc 3 commuting bike as the bike is not going downhill, and there is no chance of the brake temperatures reaching a level that requires finned brake pads. For me, it is more of changing the look of the brake calipers.

The conclusion is that the brake calipers and brake pads are not really visible and it does not really change the look of the bike. The only advantage that I have from this change is getting to use new brake pads, which stop well and are not squealing.