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.

Focus Paralane: Robert Axle Project Thru Axles

Practically all framesets that use thru axles have the axles included with the frameset. This is because even though thru axles are 12 mm in diameter for the front and rear (road disc brakes), the overall length is different. Even though the OLD (Over Locknut Distance) is 100 mm for the front and 142 mm for the rear, the frame thickness and thread length is different.

Therefore, if you buy aftermarket thru axles, you need to check carefully to make sure that it will match your bike frame. There is no issue with matching the hubs, as the hubs have a standard OLD of 100/142 mm and inner diameter of 12 mm.

The Focus Paralane is no exception, it comes with its own thru axles included. However, the thru axles are not the usual 12 mm threaded kind. Instead it uses its own proprietary RAT thru axles, which can be tightened with just a quarter turn.

Despite best intentions, there are some issues with the RAT thru axles, which can be seen at the link above. Therefore, I looked for an alternative to the stock RAT thru axles. While researching, I saw these thru axles by The Robert Axle Project.

It is an unusual name for a brand, but they do make quality products as seen from multiple online reviews. Basically, they make third party thru axles for practically all thru axle models from different bike frames. These thru axles are lighter and may look better.

For my case, what I am looking for on the Focus Paralane is not really about saving weight, but about ditching the RAT thru axle which I am not happy with.

In this case, there is only one choice of replacement thru axle, which is the bolt on type that needs to be secured with a size 6 Allen Key. It is also pretty lightweight, as it does not have an integrated lever. The downside is the high price, but I really needed to get rid of the RAT thru axle.

Robert Axle Project thru axles, specifically made for the Focus Paralane.

Secured using a Size 6 Allen Key, no lever type option.

The nuts on the other end also need to be replaced. There are two types of nuts supplied as shown above.

On the Focus Paralane frameset, the thru axle threads are not threaded into the frame itself. Most of the time, the threads are on a replaceable insert that is fixed to the frame, so that it can be replaced if the threads are damaged.

Therefore, in order to replace the RAT thru axles, the nut also needs to be changed to a 12 mm threaded type. The nut design on the Focus Paralane was changed in the past few years, which is why there are two types of nuts shown above. 

The one on the left is a newer design, which allows the lever angle on the RAT thru axle to be adjusted. The one on the right, which is what I have, has a fixed lever angle, which is not ideal. Use the nut that matches your frame design.

Original RAT thru axle "nut", with the quarter turn design. This part needs to be replaced with the one from Robert Axle.

New Robert Axle nut is 7 grams

Front thru axle is 33 grams, less than the stock 56 grams.

Rear thru axle is 38 grams, less than the stock 61 grams.

Replacing the nut is easy, just loosen the bolt and remove the nut + rear dropout.

Original RAT "nut" is just 3 grams.

New Robert Axle nut installed! Secured to the frame using the same bolt, but now it has threads for a conventional thru axle.

Replacing the thru axle system is easy, as the nut on the frame can be easily replaced. Same for the fork as well. The new Robert Axle nut sticks out a bit more from the frame, but this is compensated by the much slimmer profile on the head of the thru axle, since there is no lever sticking out.

Original RAT Thru Axle Weight = 3 + 3 + 56 + 61 = 123 grams

Robert Axle Thru Axle Weight = 7 + 7 + 33 + 38 = 85 grams

There is a small weight saving of 38 grams which is pretty insignificant, but comes at a high cost. Nevertheless, the thru axle system is now better as there is no handle, which looks clean but also harder to use, as an Allen Key is needed to remove the thru axle.

It is an additional cost to owning this bike, which is one of the many quirks of this frameset. Of course, this thru axle change is not compulsory, but I personally could not accept the downsides of the RAT thru axle. Given a choice again, I might have considered another frame, since there are actually many downsides on this Focus Paralane frameset.

Focus Paralane: Curana Fenders and RAT Thru Axles

The Focus Paralane is designed to be an endurance bike, with its tall stack for a less aggressive riding posture. It is one of the few road frames designed to have integrated mudguard mounts. In fact, this frame is so integrated that special mudguards are included, specially designed and made by Curana to match this frame!

Here is how the matching mudguards are supposed to look on the bike.

This picture shows the newer version of the rear mudguard, with two pairs of mudguard stays to support the mudguard.

For a sleek look, the mudguard is almost flat across the sides, without a deep curvature.

Textured wording and design makes the mudguard look really premium.

As seen above, those are marketing pictures that I found online. Unfortunately, I was not able to replicate these pictures, as explained below.

Mudguard with a combination of matte and gloss texture, looks really good.

At the rear seat stay area, the mudguard is pinched inwards, for clearance with the seat stays.

Measures about 39 mm across at the widest point. This should be wide enough for 28 mm wide tires.

It narrows to 35 mm at the pinched area.

This is the condition which I found the rear mudguard. It was bent and deformed, even before using it.

It is not possible to fix it properly, as the aluminium mudguard has already been deformed to this extent. 

As I had already planned to use my own SKS mudguards, the bent Curana mudguards was not a deal breaker for me. However, if I had planned to use the stock mudguards, I would be extremely annoyed as I can't use it, due to it being bent out of shape. Even if it is repaired, it will probably not have a smooth curve to match the tire.

At the other end of the rear mudguard, there is a cutout for clearance with the front derailleur.

The set of mudguards as I received it. Bad condition, luckily I didn't need to use it.

Mudguard stays with straight ends, to match this frame.

There are only two mudguard stays, as there is only 1 set for the front and 1 set for the rear. Normally, there are 2 sets for the rear, as shown by the pictures at the beginning of this post. Sadly, that is the improved version with 2 stays for the rear mudguard, not the older version that I have, with just 1 stay at the rear.

Based on research prior to getting this bike, I had already planned to use my own SKS mudguards instead of using the stock mudguards. Reasons are:

1) Rear mudguard only has 1 mudguard stay, which means that the top part of the mudguard is not supported well. Over bumpy roads, the top part of the mudguard will bounce and touch the tire. This is what I read from online reviews.

2) Rear mudguard has a cutout at the front derailleur area. It is necessary for clearance, but also means that this area will have water splashing through due to less coverage. Not ideal as it will spray water all over the chain ring area.

3) Front mudguard does not have enough coverage at the bottom, as there is no rubber flap. This will allow water to splash up onto the chain ring and also the rider's feet.

Nevertheless, there are some parts which I need from the mudguard set. These would be the brackets that hold the mudguard to the frame.

This is the plastic piece that holds the top part of the rear mudguard to the mount. The flashing on this resin part is very bad. I will not require this.

Unique bracket to hold the rear mudguard in between the seat stays.

There is no built in mudguard mount in between the seat stays, so that it has a clean look if mudguards are not used. However, if needed, this additional bracket will fit in between the seat stays.

These are the parts that are included with the stock mudguard set. Good to have a part list to check.

Just for fun, I weighed the stock mudguards that I will not be using. These are lightweight at just 377 grams.

I will be using a new set of SKS mudguards, so these stock Curana mudguards will not be needed. I will only require the chain stay bracket, and nothing else. Detailed info on the SKS mudguards will be shared in a later post.

Another component that came stock with the Focus Paralane are the unique RAT thru axles. In theory, they make wheel changes really fast, as only a quarter turn is needed to loosen or tighten the thru axle.

Both front and rear thru axles are 12 mm in diameter.

RAT stands for Rapid Axle Technology.

Instead of a M12 thread at the end, a T-shaped hook is there instead.

Basically, you slot the T-shaped end of the thru axle into the nut, and twist it 90 degrees to lock it in place. Then, the lever is closed to apply locking pressure.

However, due to frame and hub width tolerances, it is necessary to fine tune the axle length, so that when the lever is closed, sufficient closing pressure is created.

The adjustment nut under the lever can be adjusted by hand, which fine tunes the axle length. If the lever does not close tight enough, the nut should be adjusted to shorten the axle slightly.

Nominal front thru axle length

Nominal rear thru axle length

Note that thru axle lengths, not just RAT thru axles, are very dependent on the thickness of the frame or fork dropout. Taking the fork as an example; Even though the hub width is 100 mm, the fork leg width and nut thickness will affect the length of the thru axle required. This is why most frames come with thru axles included.

Front thru axle weighs 56 grams

Rear thru axle weighs 61 grams

The weight of both thru axles is this 117 grams, which is a bit lighter than the pair on the Cervelo Aspero, that weighs 129 grams.

The weight of the thru axles don't bother me. However, what bothered me was the design of the RAT thru axles. I identified three issues that I could not live with.

1) During insertion of the thru axle, it was difficult to determine which angle to push the thru axle in, so that the T-shaped end slots neatly into the nut on the other side.

2) Due to the thickness of the adjustment nut and the lever, the RAT thru axle sticks out a lot from the side.

3) The lever resting angle cannot be adjusted, which causes the lever to stick out at awkward angles.

Although the thru axle length can be adjusted, the lever angle cannot. It is determined by the slot angle on the nut. Since the slot angle on the nut is fixed, the lever angle is also fixed, unfortunately at weird angles. I saw that newer RAT thru axles allow the nut angle to be adjusted, which in turn enables the lever angle to be adjusted.

There are aftermarket thru axle designs which can be used to replace the stock RAT thru axle, but that is a story for another day. Once again, similarly to the mudguards, I will not be using the stock thru axle design. 

It may be curious to you, why did I get this Focus Paralane frame, if there are so many aspects that I didn't like (mudguards, thru axles, tall head tube, press fit BB, etc). The thing is, I didn't have other choices, if I wanted a lightweight carbon road bike frame with integrated mudguard mounts. There were a few other options, but the tire clearance became really small when mudguards are installed.

For example, the Specialized Diverge is a high end frame, but the S-Works version actually weighs about the same (995 grams) as this Focus Paralane (1005 grams). The lower grade versions weigh more and yet cost more as well.