Specialized Aethos: S-Works Frame

Time to build a new bike! I have been reading about the Specialized Aethos, and it seems to be an awesome bike that is different from others. Some of the features that attracted me:

1) Rides very well without being overly stiff nor flexible.

2) Extremely lightweight frameset, especially for a mass produced carbon frame.

3) Non-integrated cable routing at the stem and headset area, for easy maintenance.

4) Threaded bottom bracket for easy servicing.

5) Conventional round seat post, with external seat post clamp.

After doing lots of research, I decided to buy the frameset from the local Specialized dealer. I was able to find the colour that I wanted (Satin Flake Silver/Red Gold Chameleon Tint/Brushed Chrome), or Champagne colour in short.

With this bike, I can go full weight weenie, and source for components that are of high quality and also lightweight. Starting with the frame, follow me on this bike build process!

Specialized S-Works Aethos frame! No large S-Works logo splashed across the down tube.

The colour looks like pinkish champagne, which is very unique as I have not seen it on other bikes before.

Smooth blended interface between the head tube, top tube and down tube. This ensures optimal strength with the least amount of material used.

Small Aethos logo on the front of the head tube, which I prefer over big flashy logos.

Check out the metallic paint job which looks very good in the sun.

One cable hole on the side of the head tube, for the rear brake hose.

Integrated headset design for headset bearings, for weight savings and a clean look. Easy headset assembly as well.

Both top and bottom of the head tube has integrated bearing seats. Inside of the frame looks nicely finished.

The paint job looks gorgeous under sunlight.

Small S-Works logo on the top tube, which is the way I like it. Size 52 frame size.

Unpainted carbon under the seat post clamp.

Again, smooth joints between the top tube, seat tube and seat stays. Maximum stiffness at minimum weight.

Smooth joining between the down tube, seat tube and chain stays. Bottle cage bolts on the down tube and seat tube.

Front derailleur bracket, with a hole at the side for the Di2 cable to pass through.

S-Works frames use 12R carbon with the highest modulus to ensure good strength and stiffness at a low weight.

Bottom bracket is threaded for easy servicing and no creaking. Nicely blended into the rest of the frame.

At the bottom, the chain stays are slightly squarish. 

Standard chain stay design, without being oversized.

Rear flat mount brake mounting, with the rear brake hose exiting from the left side chain stay.

M12 thread for the rear thru axle is integrated into the frame for weight reduction, instead of having the threads on a separate aluminum piece.

Rear derailleur hanger for M12 thru axles.

On the other side of the rear dropout, the frame has a countersunk for the thru axle to rest inside. 

Saves weight and gives a very clean appearance.

Size 52 frame weight including front derailleur bracket weighs only 599 grams!

4x aluminium bottle cage bolts weigh 5 grams.

Rear derailleur dropout weighs 12 grams.

Seat post clamp is 11 grams. Very minimalist design.

2x hose guides plus 1x Di2 wire grommet weighs 2 grams.

This S-Works Aethos frame is extremely lightweight, at just 599 grams! Very similar to the claimed weight of around 600 grams. For a fair comparison to other frames, I will add the weight of the seat post clamp, rear derailleur dropout and bottle cage bolts to this Aethos frame. This gives a weight of 627 grams for the Aethos.

Compared to the other road/gravel frames that I have measured, here is the summary.

Weight includes front derailleur mount, rear derailleur hanger, seat post clamp and 4x bottle cage bolts.

Frame Weight Comparison

Specialized S-Works Aethos: 627 grams

Canyon Endurace CF SLX: 807 grams

Focus Paralane: 1005 grams

Cervelo Aspero: 1177 grams

Fabike C3: 1296 grams

From this comparison, you can see that the Aethos frame weight is in a completely different league. If you want to build a lightweight bike, you have to start with a lightweight frame.

Cervelo Aspero: PRO PLT Carbon Road Handlebar

On the Cervelo Aspero gravel bike, I have been using the PRO Vibe Aero Superlight handlebar since the beginning. At that time, the plan was for the Aspero to serve as a dual purpose road and gravel bike, as seen from the two wheelsets that I had.

Later on, after I got the Focus Paralane as a road bike, the Cervelo Aspero was converted to be a dedicated gravel bike with a front single drivetrain. One of the more recent change was to GRX Di2 shifters which work really well for gravel riding.

All the while, the handlebar used was the PRO Vibe Aero Superlight handlebar, which is OK for road riding but not really ideal for gravel. I have some issues with the design of the PRO Vibe handlebar, such as the teardrop bar shape in the drops, and the non-compatibility with standard Garmin computer mounts.

Therefore, after much consideration, I decided to change the handlebar to a more conventional round type, to improve the ergonomics and avoid all the downsides of the PRO Vibe Aero handlebar.

At the same time, I wanted to avoid or minimize the internal routing needed, as it takes more work to route hydraulic hoses and Di2 cables through the handlebar.

Finally I chose the PRO PLT Carbon Handlebar, which is relatively lightweight, with less internal routing and a normal round clamp section on top.

New PRO PLT Carbon Handlebar

These handlebars are 40 cm wide, with a standard oversized clamp diameter of 31.8 mm.

Not the top level PRO Vibe model, but the lower PLT model.

Compact shape, with a very standard 80 mm reach and 130 mm drop.

Pretty good drop shape, but the top area where it starts curving down seems too gentle for a smooth transition to the shifter hoods.

Unfortunately there is still some internal routing on the underside of the handlebar. But at least this is much easier to route than the PRO Vibe Aero Superlight handlebar.

This handlebar weighs 230 grams, not a weight weenie type. But probably safer and more reassuring for gravel riding.

Warning label not to add clip on aero bars onto these handlebars, as the walls are probably not strong enough to support clamps.

Terrible sticker which tore apart when removing, along with lots of glue and sticker residue that took me a lot of time to remove. A very negative experience, can't imagine the bike shop having to spend so much time to clean this up.

After that, it was time to remove the old handlebar from the bike, before installing the new handlebar and the shifters on it. At the same time, I will not be using the integrated EW-RS910 Junction A inside the bar end any more, but using the Di2 Info Display SC-MT800 instead. It will essentially be the same Di2 wiring layout as on the Focus Paralane.

Similar Di2 wiring layout as on the 1x11 speed Focus Paralane.

Since both the old handlebar and new handlebar has some internal routing, I needed to disconnect the hydraulic hose from the shifters. This is the downside of having internal routing, where it is more troublesome to change handlebar or make adjustments.

For Shimano road hydraulic shifters, there is a flanged connecting bolt that needs to be screwed into the resin Bracket. The torque on this bolt needs to be within 5-6 N.m, to avoid a leaky connection or a cracked Bracket.

Torque wrenches usually have a 3/8" or 1/4" square interface to the hexagon socket, but not with open wrenches. I have always been tightening this flanged connecting bolt by hand feeling, without knowing the actual torque. Extra care needs to be taken to ensure the bolt is not over-tightened.

I recently learnt that there is a tool called a crowfoot wrench, which you can see below. It is like an adapter which is attached to a standard square interface torque wrench.

Size 8 crowfoot wrench for 1/4" torque wrench, which needs to be attached at 90 degrees to the torque wrench for accurate torque readings.

Here is how it is used. The open crowfoot wrench allows the flanged connecting bolt to be tightened using a standard torque wrench.

GRX Di2 shifters installed onto the new PRO PLT carbon road handlebar. Note that I can attach a standard cycle computer mount from Cycliq, and also the Di2 Display onto the round handlebar.

View from the front. Cycliq Duo Mount for the Cycliq Fly12 Front Camera + Light if needed.

Side view of the transition from the shifter hoods to the handlebar. Not a smooth transition, due to the shape of the handlebar.

Exploring different gravel and off-road paths with the Cervelo Aspero!

Latest bike component specifications. Note an additional 200 grams of weight mainly due to the PRO Stealth Off-Road saddle and the Redshift suspension stem.

I think it will be quite a while before I modify anything else on the Cervelo Aspero, as I don't have anything else lined up as of now (Nov 2022). It is a very good gravel bike which I really like, and I can't really find anything else that needs an upgrade. In fact, this PRO PLT carbon handlebar change is not really necessary, just something that has been bugging me for quite some time now.

Shimano Hydraulic Disc Brake Pads: Resin vs Metal, With and Without Cooling Fins

Here is a detailed blog post comparing the different brake pads made by Shimano, for their hydraulic disc brakes. With many model numbers used for the different brake pads, it is confusing for almost everyone.

However, after studying and comparing many different brake pads, I think I have got it figured out. Each brake pad has a specific model number, such as L03A, or K05Ti, etc.

Breaking down this model number into the different parts, using L03A Resin as an example.

L: Shape of brake pad, to match different brake calipers.

03: Version of brake pad. Different revisions are cross-compatible if the other parameters are the same.

A: Aluminium backing material.

Resin: Resin material used for the pad, to reduce noise.

First letter denotes the shape of brake pad. L is the finned brake pad used for road brake calipers.

Other letters that I have seen are K (similar shape and compatibility as L, but without fins) and H (4 piston brake pads). There is also the J and G type for other brake pads, just to name a few.

This is followed by a number, usually 02, 03, 04, 05 and so on. It is just the revision number of this brake pad design. For example, L02A was recently replaced by L03A, which has a more durable resin pad material. Different revisions are compatible as the pad shape is unchanged.

After the number, the letter refers to the backing material. The backing is the plate that the brake pad is attached to. This can be made with aluminium, steel or titanium.

A: Aluminium

S: Steel

Ti: Titanium

C: Combined

Final part of the model number refers to the pad material, whether it is made of resin or metal.

With different backing materials, different pad materials, and different shapes, it gives rise to many different combinations and thus many different options. In fact, I think there are too many variations which makes it very confusing.

Here are 5 different brake pads that I have, to match different brake calipers.

Metal brake pads shown here.

K04Ti Metal: K shape, version 04, titanium backing, metal pads.

L04C Metal: L shape with fins, version 04, combined backing (aluminium + steel), metal pads.

Resin brake pads shown here.

K05Ti-RX: K shape, version 05, titanium backing, resin pads.

L03A Resin: L shape with fins, version 03, aluminium backing, resin pads.

H03A Resin: H shape (4 piston), version 03, aluminium backing, resin pads.

With all these examples, the model number code is now clear. Now I have learnt how to identify each type of brake pad.

Let's take a closer look at the difference between resin and metal brake pads. For the pros and cons of each type, you can Google for the answers.

Metal brake pad on the left, resin on the right. The metal pads have much more metal content inside as seen from the reflectiveness. This also adds to the weight.

The metal pad on the right has a separate steel backing, which is riveted to the aluminium backing with cooling fins. I am not sure why it is made this way, instead of the bonded construction like the resin pad.

A pair of resin brake pads with aluminium cooling fins weigh 17 grams. This is the most common brake pad used on Shimano road hydraulic brake calipers.

A pair of metal brake pads with aluminium cooling fins weigh more, at 26 grams. Useful for more braking power if you want to go off-road on gravel bikes.

Resin brake pads without cooling fins, with titanium backing. 12 grams for the pair. Lightest brake pad out of all the variations.

Resin brake pads without cooling fins, with steel backing. Weighs 5 grams more than the titanium backing version.

Metal brake pads without cooling fins, with titanium backing. 15 grams for the pair.

H03A Resin, used for some 4 piston MTB brakes, such as the Deore XT brakes used on the Bike Friday Haul-A-Day cargo bike.

Summary of actual weight for different brake pad configurations

2 Piston Resin Pad

With aluminium backing and fins: 17 grams

With steel backing, no fins: 17 grams

With titanium backing, no fins: 12 grams

2 Piston Metallic Pad

With aluminium+steel backing and fins: 26 grams

With steel backing, no fins: 22 grams (estimated)

With titanium backing, no fins: 15 grams

4 Piston Resin Pad

With aluminium backing and fins: 25 grams

In summary, if you want to reduce weight, use resin brake pads as they are lighter than metallic brake pads. Using the titanium backing with no cooling fins will also save some weight over the aluminium backing with fins. That said, the weight difference is only 5 grams (17 vs 12 grams) per brake, giving a total savings of only 10 grams per bike.

With such a small difference, it is more important to choose the correct brake pad, depending on your needs or preference, rather than weight.