Saturday, June 22, 2019

Ascent Bikes Road Crankset

For my new bike building project, I will be running a 1x11 speed drivetrain. As such, I will require a front single crankset, using a chain ring with narrow-wide teeth for chain retention.

I have already built a few bikes with front single drivetrains, and I usually use a Shimano road crankset. The road crankset comes as a front double setup, so I will remove both the outer and inner chain ring, and install a third party narrow-wide chain ring.

Examples can be seen here, on the Dahon MuEX, the Dahon MuSP, and the Crius AEV20. There are more examples, but these are the main ones.

As you can already tell, I like the Wolf Tooth Drop Stop chain ring, as it comes in a large variety of chain ring sizes, and most importantly, it has 4 arm variants that can be fitted to newer Shimano road cranksets (Dura-Ace 9000 series and newer). I have never ever had a chain drop from the Wolf Tooth chain ring, that is how good it is.

In summary, I would usually get a Shimano road double crankset, and remove both the chain rings. Then, choose an appropriately sized Wolf Tooth chain ring, to match the crankset (4 arm or 5 arm). Finally, get some chain ring bolts for a front single setup, where the colour can be customized to add some bling to the bike.

However, this strategy is expensive, as Shimano road cranksets are quite pricey, since we are paying for the Hollowtech forging crank arms, plus the Hollowglide chain rings. The differences between the different grades of Shimano cranksets can be seen here.

After that, the chain rings are not used, and just kept in the storeroom, in case I want to restore the front double crankset one day (almost never). To add on, the Wolf Tooth Drop Stop chain ring is expensive too!

In order to reduce the cost and also prevent wastage (unused chain rings), I started to look around for good quality, dedicated front single cranksets, with narrow wide chain rings. Of course, it has to be available at a reasonable price, and also a reasonable weight.

After doing a comparison between a few different brands, I found this in-house crankset by Ascent Bikes, which is a dedicated front single crankset. It is Shimano road bottom bracket compatible (24 mm diameter spindle, 68 mm BB spacing), and uses a narrow-wide chain ring. The appearance is pretty decent, with a matte black, sandblasted finish that matches most bikes. The weight is around the same as an equivalent Ultegra+Wolf Tooth setup (more details below), but the price is about 1/3 of it!

Let's take a detailed look at this front single crankset by Ascent Bikes.

Overall look at the crankset. Direct mount chainring with 6 arm design. Hollow spindle visible from the drive side, similar to mountain bike crankset appearance.

Weighs 629 grams, with a 44T chain ring. Just a few grams heavier than an Ultegra crankset + Wolf Tooth chain ring setup.

I was quite surprised at the weight of this crankset, as it is lighter than it looks. Normally, for this kind of non-hollow crank arms, it will weigh much more, at 700 grams or more. Ultegra-level of weight, at 1/3 the price? I'm not going to complain about that!

Closer look at the right side crank arm. Design is simple but functional, which is fine with me.

Right side crankarm + 44T chain ring + 4 mounting bolts weigh 412 grams. The direct mount chain ring design can also be seen here.

How it looks with the chain ring removed. Crank arm shape is simple with no strong character lines.

Hollow aluminium spindle is press-fitted to the drive side crank arm. 

Rear side of the crank arm is heavily sculpted to remove material and reduce weight. Looks a bit weak, but I will probably not be strong enough to flex it significantly.

Splines on the crank arm to match the chain ring, for the direct mount design. The spline design is different and so cannot be interchangeable with direct mount chain rings from other brands.

Splines on the non-drive side of the aluminium spindle, where the non-drive crank arm will be fixed to.

With the chain ring and chain ring bolts removed, the drive side crankarm + spindle weigh 288 grams.

4 x chain ring bolts weigh just 8 grams.

44T direct mount chain ring. This size is chosen to provide the gear range that I need. There is some offset between the centre mounting area and the teeth, in order to achieve the correct chain line.

Spline design on the chain ring.

Narrow wide teeth design on the chain ring.

Made of aluminium alloy 7075, with T6 heat treatment. From what I know, this grade of aluminium can be machined easily, which makes it popular in chain rings, seat posts and stems.

Another look at the narrow wide teeth on the chain ring.

44T chain ring weighs 117 grams. 

Left side (non-drive side) crank arm.

Also heavily sculpted at the back for weight reduction. Forged for extra strength, as compared to being made by casting process. 

Left side crank arm weighs 212 grams, which is about 20 grams more than an equivalent Ultegra left side crank arm.

Aluminium crank arm fixing bolt is unique, and weighs 6 grams. Tightens to the spindle using an Allen key.

Just a random shot of the crank arms, with the chain ring removed. If the chain rings and crank arms are stored separately, it can save a lot of storage space as they can all be flat-packed.

In a later blog post, I will be installing this Ascent Bike crankset onto the bike, and evaluate the performance and riding feel. What I will check is how stiff the crankset feels, as compared to the other cranksets that I have.

For now, I am happy with how the crankset looks and weighs. With an Ultegra-level weight at 1/3 the price, it looks to be a really good alternative for a dedicated front single crankset.

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