Specialized Aethos: Dura-Ace C36 Wheelset and GP5000 Tires

Building a lightweight bike requires a lightweight wheelset. For the Specialized Aethos, I decided to get a relatively lower profile carbon wheelset to help save some weight.

Previously I got the Dura-Ace C50 wheelset for the Focus Paralane, during the change to 12 speeds. That C50 wheelset with a 50 mm tall rim profile weighs 1493 grams, which is a good weight but not really lightweight.

This time, I got the Dura-Ace C36 wheelset, which is exactly the same as the C50 wheelset, except for the lower 36 mm rim profile. Due to the lower profile, the wheelset will be lighter. Check out the details below.

Dura-Ace C36 R9270 wheelset

Dura-Ace wheelsets are available in 36, 50 and 60 mm rim profiles. The C36 is the lightest but also least aerodynamic.

Rim profile is about 36 mm as claimed.

Other than the difference in rim profile (and spoke lengths), all other areas of the C36 wheelset is the same as the C50. For the details such as rim width, hub info, etc, check out the C50 blog post.

Weight of C36 front wheel is 622 grams.

Weight of C36 rear wheel is 727 grams.

Dura-Ace C36 Wheelset

Front Wheel: 622 grams

Rear Wheel: 727 grams

C36 wheelset total: 1349 grams

Dura-Ace C50 Wheelset

Front Wheel: 693 grams

Rear Wheel: 800 grams

C50 wheelset total: 1493 grams

Ascent Bikes Zenith Elite (for reference)

Front Wheel: 682 grams

Rear Wheel: 822 grams

Wheelset total: 1504 grams

Based on this comparison, the C36 wheelset saves 144 grams over the C50 wheelset, or about 10% of the wheelset weight. Quite a substantial difference, especially at the high end wheel market where the differences are small.

As for the tires, I went back to the tried and tested Continental GP5000, which is the same as what I used on the Dura-Ace C50 wheelset and also the Ascent Bikes Zenith Elite wheelset.

Brand new folding tires! These are the 28 mm wide version.

Each tire weighs 244 grams, and this varies from batch to batch.

GP5000 tires installed on the C36 wheelset. Looking good!

Another picture of the new wheelset and new tires

Although I had the chance to go for a tubeless setup this time, since I had to get a new wheelset and tires anyway, I did not do so. I am still not convinced of the benefits of road tubeless, as I think it is easier to just change an inner tube if I do get a puncture.

On the other hand, if a tubeless tire and sealant is used, it will make a mess if there is a puncture, especially since the tire pressure is higher. For off-road riding such as on the Cervelo Aspero gravel bike, tubeless is awesome, but not necessary for road riding.

Nevertheless, I tried out some new types of inner tubes this time, so as to save weight and improve the ride quality. As opposed to the usual butyl inner tubes, I tried latex and TPU types. Check out the next post for the details!

Specialized Aethos: S-Works SL Stem and PRO Vibe Superlight Handlebar

In the earlier posts about the Specialized Aethos, I have shared some information about the frame, fork and other small parts that come with the frameset.

As the Aethos is designed to use a standard stem and handlebar, with no integrated cable routing at the front, it means that I am free to choose a stem and handlebar to use. I like it this way as I am not a fan of integrated cockpits. Although it looks very neat and clean, it takes a lot of effort to assemble this kind of integrated cockpits. If you leave this job to the experienced bike mechanics at the shop, it is not an issue for you. However, if you prefer to work on your own bikes, I would definitely prefer to have a non-integrated front end that I can work on easily.

For a lightweight build, the weight of every part needs to be considered carefully, as every gram counts. I have considered using super lightweight parts from Darimo, but the price is just too high for me to accept, at $750 for a handlebar and $650 for a stem. An alternative is to use Specialized own stem, which is pretty lightweight. It also matches the S-Works frameset which is a nice touch as well.

Specialized S-Works SL Stem, ordered online from the Singapore Specialized store.

I was surprised to see how moldy it is straight out of the box!

Look at the picture above, how would you feel as a customer if the brand new part that you ordered came to you in such a condition? It seems that the part has been in storage for quite some time, for it to develop so much mold on a metal part.

Surely someone would have spotted the condition of this part before packing and sending it out, since the part can be seen from the hole in the box.

Luckily the mold can be cleaned off without too much effort. Even so, this condition is unacceptable.

After cleaning off the mold from the stem, it looks good now.

The stem is 90 mm long with a 6 degree tilt.

Uses 4x titanium bolts to save some weight.

Stem weighs 116 grams, not really lightweight. Similar to PRO or FSA stems.

On hindsight, I would have gotten another stem, since it is not really lightweight. The claimed weight is 110-115 grams in 110 mm length. In this case I expect the 90 mm stem to weigh less than 110 grams, maybe 100-105 grams. Actual weight is 116 grams.

Other than the stem, I also needed a new handlebar for the Aethos. Some previous handlebars that I used are the Brand X carbon handlebar on the Focus Paralane, the PRO Vibe Aero Superlight on the Cervelo Aspero, and the most recent PRO PLT carbon handlebar.

However, each of them have their own issues, which is why I decided to get another model. This time, it is the PRO Vibe superlight handlebar, but not with aero cross-sections. It has standard round tubes which I prefer.

PRO Vibe superlight carbon handlebar, which is the lightest that PRO makes.

Claimed weight is 185 grams, let's see the actual weight.

As the narrowest width is 40 cm, I assume that the claimed weight of 185 grams refers to this width.

Logos on the centre clamp area of the handlebar. Centre section is a standard round shape which makes it compatible to many standard accessories, unlike the Aero Superlight version.

It has 4 exit holes near the centre clamp, 2 for each side. I will only need 1 on each side for the hydraulic brake hoses.

Two cable holes near the bend. Designed for 1x brake hose, and 1x Di2 wire or shifter outer casing.

Standard compact drop shape. However, I think the transition from the top to the curve is not sharp enough, which will prevent a smooth transition from the handlebar to the shifter hoods.

Wall thickness is only about 1 mm, in order to achieve the low weight.

Handlebar weight is 198 grams, about 7% more than the claimed weight of 185 grams.

In total, this stem and handlebar combo weighs 314 grams. Quite a respectable weight, but could be below 300 grams if both the stem and handlebar did not exceed the claimed weight. One alternative I could have used was the Roval Alpinist cockpit, which is a combined stem and handlebar that weighs 255 grams (claimed). However, this also means that I can't change the stem length later on.

Specialized Aethos: Front Brake Caliper Adapter and Disc Rotors

The Specialized Aethos uses mostly standard components and specifications. For example, it uses a standard threaded bottom bracket and round seat post on the frame. There is no internal routing around the head tube and steerer tube of the fork as well.

However, there is one non-standard design on the fork, which is the disc brake mounting area. Although it uses a flat mount brake design, the distance between the holes are not the flat mount standard.

According to Specialized, the holes are closer than the usual flat mount standard, so that they can make the end section of the fork leg hollow, in order to save some weight. Not sure if it is worth it to make this non-standard design, when most other areas are standard.

Flat mount holes on the front fork, where the hole to hole distance is closer than usual.

Special flat mount adapter (top) supplied with the Aethos frameset, and it means only a 160 mm front rotor can be used.

Adapter and hole distance (between slots at both ends) is shorter than the standard design (below).

Aethos front brake adapter is lighter as well since it is shorter, at just 9 grams.

Standard Shimano front flat mount adapter is 12 grams.

Aethos front brake adapter mounted on the Dura-Ace R9270 brake caliper. 

140 mm rotor cannot be used, only 160 mm is possible.

As for the brake rotor, I have a collection to choose from. 

From left to right: RT800, RT900, MT800, MT900.

As already tried on the Focus Paralane, I will be using a 160 mm rotor on the front and a 140 mm rotor at the rear. It has sufficient brake power while also saving some weight. The same 160/140 mm rotor setup is used on the Fnhon DB12.

140 mm rotor vs 160 mm rotor, both are XTR MT900 rotors. Note the difference between a new rotor (left) and a used rotor (right).

140 mm rotor without lock ring is only 88 grams.

160 mm rotor is heavier at 106 grams.

As mentioned in the Focus Paralane post, using a 140 mm rotor instead of 160 mm at the rear saves about 35 grams. On the Specialized Aethos where I am building a lightweight bike, every gram counts.

Specialized Aethos: Thru Axles, Roval Seatpost and Di2 Battery

On the Specialized Aethos, there are many high end components used, with the main objective being to make the bike as lightweight as possible.

Starting with the super lightweight sub-600 gram frame and sub-300 gram fork, even the fork expander plug is designed to shave off every gram possible. To continue with this lightweight theme, the other parts on the bike are also designed or chosen to be lightweight.

In the previous posts on the frame and fork, I shared that the thru axles are designed to rest inside a countersunk, giving a seamless look on the outside of the frame. To do so, the thru axles need to have a chamfered head to match, as shown below.

Aethos 142x12 mm rear thru axle, only 29 grams.

Aethos 100x12 mm front thru axle, only 22 grams.

This gives a total thru axle weight of only 51 grams, which is super lightweight. This is lighter than the Robert Axle Project thru axles on the Focus Paralane (71 grams), and the Cervelo Aspero (129 grams, including levers).

Not only are these thru axles lightweight, there is also a brass bushing on the chamfered contact area with the frame and fork, to reduce friction during tightening.

The Aethos frameset also includes the seat post. Not because it requires a proprietary seat post due to a special tube shape, but because the seat post is a key part of the frameset if you are looking to minimize the weight. Of course, this additional component is reflected in the frameset price.

This seat post is from Roval, the sister brand of Specialized. Roval is regarded as a high end component brand, making wheels, cockpit components and seat posts.

Roval carbon seat post that comes with the Aethos frameset. Only 300 mm long to reduce unnecessary weight.

Seat post is from the Alpinist series, which is used for the lightest components.

Check out how thin the walls of the seat post are, at less than 1 mm thick!

Seat post only weighs 135 grams! And that is with a pretty robust saddle rail clamp design.

Other lightweight seat posts that I have used previously were the Hylix 25.4x400 mm seat post for the Focus Paralane (151 grams) and the Cervelo SP19 27.2x350 mm seat post for the Cervelo Aspero (188 grams). This Roval seat post is shorter and also lighter.

As this Specialized Aethos will be set up as a Di2 bike, I still need to have a Di2 battery installed somewhere on the bike. The easiest way is to install it inside the seat post, as I have done on most of my other Di2 bikes. The Focus Paralane,  Cervelo Aspero and also the Fabike C3 has the Di2 battery tucked inside the seat post.

Ritchey Di2 Battery Mount, along with a black plastic shim (included with battery) to adjust the fitting of the battery inside the seat post.

Found a problem with this Ritchey Di2 battery mount, where the rubber material is interfering with the plug of the new BT-DN300 Di2 battery.

I realized that this interference is due to the new DN300 battery having a bigger plug than the previous DN110 battery. The new battery allows 3x Di2 wires to be connected to it, doubling up as a Junction B, which is why it has a bigger plug. My Ritchey Di2 battery mount is an older type which did not cater for this bigger plug size.

Anyway, it is not a big problem, as I can just cut away some material from the Ritchey Di2 battery mount to eliminate the interference.

After removing the extra material from the Ritchey Di2 battery mount, it fits the battery with no issue.

Later on, during assembly, we shall see if this Di2 battery and battery mount is able to fit inside the seat post snugly without dropping out.

Specialized Aethos: Headset, Spacers and Expander Plug

Joining the Aethos frame to the Aethos fork is the headset and other small parts around the headset. As mentioned earlier in the posts, the Specialized S-Works Aethos uses an integrated headset design, with the bearing races already molded directly into the head tube of the frame, and steerer tube of the fork. This eliminates any extra headset bearing races that needs to be pressed into the frame, such as on the Fnhon Gust or Fnhon Tornado frames.

Headset bearing races already molded into the head tube, at the top and bottom.

The frameset includes the headset bearings, and here are some pictures of it. Good reference for the future when a new replacement bearing needs to be sourced.

Headset top bearing, with 1 1/8" inner diameter and a 45 degree chamfer.

Headset bottom bearing, with a 49.5 mm outer diameter, 40.5 mm inner diameter, and 6.5 mm height.

Together with the compression ring, the headset bearings weighs 39 grams.

Here are all the carbon stem spacers that are included with the Aethos frameset. 3x 10 mm, 1x 5 mm and another 5 mm spacer on the right.

The spacers are scalloped, with more material removed from the inside, such that only 3 points are touching the steerer tube. All in the name of reducing weight!

Each 10 mm scalloped spacer weighs just 3 grams, but this is similar to other lightweight carbon spacers (about 4 grams), so not much savings here.

For reference, here are the other types of stem spacers. From left to right: Thin carbon spacer, standard carbon spacer, aluminium spacer. All are 10 mm tall.

Thin carbon spacer weighs 3 grams, same as the special scalloped ones on the Aethos.

Standard carbon spacer with thicker walls is 4 grams for 10 mm height.

Aluminium spacers are double the weight at 8 grams for 10 mm height.

Carbon headset cover is also lightweight at just 5 grams.

Next, let's take a look at the expander plug, or otherwise called compression plug. This part goes into the inside of the steerer tube, and expands to secure itself inside. It acts as an anchor point for the top cap to compress downwards on the stem, applying pre-load on the headset bearings.

The Aethos frameset comes with its own expander plug. At the same time, I also ordered the S-Works SL Stem, as the stem is not included with the frameset. The stem actually comes with its own expander plug as well, but of a different design. Check out the comparison below.

Expander plug that is included with the S-Works SL stem. Different from the one included with the Aethos frameset.

Side by side comparison. Expander plug from the stem on the left, while the right side expander plug is from the Aethos frameset. I think the bolt material is different as well.

The shaft of the expander plug on the right side has material removed, in order to shave off even more weight from the Aethos frameset. Both have thin and slotted flanges for reduced weight.

Expander plug from the stem, weighs 27 grams. About the same as the one found on the Cervelo Aspero.

The Aethos version is even lighter, at just 17 grams!

For maximum weight savings, use the Aethos expander plug (17 grams), together with the top cap and screw from the S-Works SL stem (4 grams).

For comparison, the Cervelo Aspero expander plug is 28 grams, while the top cap and screw is 15 grams, giving a total of 43 grams. This makes the Aethos version less than half the weight. Every little bit counts when you are building a weight weenie bike!