Sunday, November 10, 2019

Canyon Endurace: GRX Rear Derailleur and Cassette

The most important change needed to convert a standard road bike to a gravel bike would be a new set of gravel tires. There is a huge difference when you ride a gravel trail on a set of slick tires, versus a set of gravel specific knobbly tires. I used the Panaracer GravelKing SK tires on a separate DT Swiss G 1800 wheelset, and it has worked well for me.

In order to have a separate gravel wheelset that can be swapped quickly with the standard road wheelset, it is necessary to have an additional cassette and disc brake rotors on the gravel wheelset as well. This way, the wheelset can be swapped in without adjusting or changing any other component.

In this case, a new cassette is needed on the gravel wheelset. If I were building a gravel bike from scratch, with a new frame, most likely I will go for a front single drivetrain, with a wide ratio cassette at the back. For example, a 40T chain ring with a 11-42T cassette at the back.

However, since I am modifying the Canyon Endurace to be a part-time gravel bike, I need to maintain the front double drivetrain that is needed for road riding. Just to recap, the Canyon Endurace is equipped with a full Dura-Ace R9170 groupset, with the 50/34T crankset and a 11-30T 11 speed cassette.

A front double crankset is actually pretty good for a gravel setup as well, as the small 34T inner chain ring can provide a low gear ratio for off-road riding. Usually, a gravel setup will have a lowest gear ratio of 1:1, to enable grinding up steeper slopes. In this case, since the small chain ring is already 34T, a 11-34T cassette will achieve a lowest gear ratio of 1:1, or roughly 28 gear inches with 700C wheels.

A larger 11 speed cassette would be 11-36T or even 11-40T, but it is probably not necessary with the low 34T chain ring available. Besides, the gear sprocket difference between the gravel wheelset (11-34T) and road wheelset (11-30T) should be minimized for better shifting performance, as will be explained later on.

Ultegra grade CS-HG800-11 cassette, 11-34T 11 speed.

The compatibility graphic on the packaging is a bit confusing, because this 11 speed HG800 cassette can actually be used on 8/9/10 speed freehub bodies, just by omitting the 1.85 mm spacer that comes with the cassette. A 11 speed MTB freehub is the same as a 8/9/10 speed freehub.

Ultegra grade finishing on the sprockets, but it is not classified under Ultegra R8000. Probably because the cassette structure is a bit different, as it can be used on 8/9/10 speed freehub bodies as well, not exclusively on 11 speed road freehub bodies.

Weighs 337 grams, including the 1.85 mm spacer. 130 grams heavier than the 11-30T Dura-Ace cassette.

Gear sprockets are 11-13-15-17-19-21-23-25-27-30-34. 

I don't like the large 11T to 13T jump at the top end of the cassette, as explained before here. That is the case if all the gears are used, such as on a 1x11 speed drivetrain where the full gear range is utilized.

However, I realized that on this 2x11 speed Di2 drivetrain, the cross-chaining is electronically limited. Basically, if you are in the small 34T chainring, the rear derailleur does not allow you to shift to the top two gears on the cassette (11T and 13T in this case). The reason is to prevent chain touching on the large chain ring due to the cross chain angle, and also to ensure that the chain capacity of the rear derailleur is not exceeded.

In other words, when I am using the small 34T chainring, I am limited to 9 gears at the back (15T - 34T). The top 2 gears on the cassette are only accessible when in the large chain ring, where it is hardly used as the gear ratio is usually too high for me. In conclusion, the large jump between 11T and 13T does not come into play at all, as it is not selectable (when in small chainring) or the gear ratio is too high (when in large chainring).

The 11 speed 11-34T cassette disassembled.

Rear view of the cassette with the large aluminium spider. Note that the largest sprocket is cantilevered out over the spider, beyond the freehub body. This is what enables it to be mounted on older 8/9/10 speed freehubs.

The largest 3 sprockets (27T, 30T, 34T) are mounted on an aluminium spider, and is specific to this cassette.

Next 3 sprockets (21T, 23T, 25T) are also mounted on an aluminium spider. This is different from other Ultegra cassettes which use carbon fibre for the second spider.

This second spider is also specific to this cassette only.

It has an aluminium lock ring, but then uses resin spacers instead of aluminium spacers of other Ultegra cassettes.

An additional 1.85 mm spacer is provided, which should be used ONLY if you are mounting this spacer on 11 speed freehub bodies.

If done correctly, the top 11T sprocket should protrude from the freehub body thread by a couple of millimetres.

If you miss out the 1.85 mm spacer when mounting on an 11 speed freehub body, the whole cassette will sit too far inwards, and the lockring cannot secure the casette properly. This picture shows the wrong setup.

In my opinion, branding the cassette as a non-series HG800 is correct, as it is a bit short of the Ultegra grade quality expected. Besides using resin spacers instead of aluminium spacers, the second spider does not utilize carbon fibre material, which is another difference.

With the cassette settled, let's move on to the rear derailleur. The Canyon Endurace is currently using the Dura-Ace R9150 Di2 rear derailleur, which is rated for up to 30T large sprocket and a maximum chain capacity of 33T. If I use the 11-34T gravel cassette, the total chain capacity required would be (50-34) + (34-11) = 39T.

If we discount the top 2 sprockets (11T and 13T) as it is limited by the Di2 system, the chain capacity required would be (50-34) + (34-15) = 35T.

In this case, the R9150 rear derailleur cannot achieve both the required max sprocket size and also the chain capacity. Therefore, a new rear derailleur is needed to match with the larger 11-34T sprocket.

Remember, my objective is to enable the road bike to be transformed into a gravel bike, just by a change of wheelset. The rear derailleur and chain must be compatible to both the road and gravel setup, without any adjustment required during the swap. My plan is to set up the rear derailleur and chain length to match the larger 11-34T gravel cassette, and this same rear derailleur and chain setup also needs to work for the 11-30T road cassette.

The Ultegra RD-R8050-GS (mid cage) Di2 rear derailleur is compatible with a 34T large sprocket, but if I'm going to make a gravel setup, I might as well use components from the new GRX gravel groupset. There are a few new GRX rear derailleurs, to suit different gravel setups (1x or 2x, mechanical or Di2 shifting). What I need in this case is the GRX Di2 rear derailleur for a 2x11 speed drivetrain.

Nice packaging graphic to signify the GRX gravel component.

4 types of GRX rear derailleurs available. I would be using the RD-RX815 which is the Di2 rear derailleur for a 2x11 speed drivetrain.

GRX RD-RX815 Di2 rear derailleur. Shadow construction, similar to RD-R8050, but with an aggressive outer link design. The design language is in-between road and MTB, which works well for gravel.

The aluminium cage is quite long, to achieve a max chain capacity of 38T. This is helped by the large 13T tension pulley at the bottom. Otherwise, the structure is similar to the RD-R8050 used on the Dahon MuSP.

Most importantly, this GRX rear derailleur is equipped with a clutch! This increases chain tension to minimize chain slapping and eliminate dropped chains. Already in use on MTB rear derailleurs for many years. This will be super useful for gravel riding.

Weighs 287 grams, which is 90 grams heavier than the Dura-Ace rear derailleur. This is expected as the GRX rear derailleur has an additional clutch, a longer cage, and does not use carbon fibre outer and inner plates.

Comparing the GRX rear derailleur with the Dura-Ace rear derailleur which is still on the Canyon Endurace.

Comparing them side by side. Similar Shadow construction, but the GRX rear derailleur seems to be the more capable one, with a larger chain capacity and a clutch function.

In order for this road/gravel setup to work, this new GRX rear derailleur needs to match both the 11-34T cassette on the gravel wheelset, and also the 11-30T cassette on the road wheelset. I will basically have to set up the rear derailleur B tension screw using the 34T sprocket, and hope that it will still shift well on the 30T sprocket on the road wheelset.

The chain length obviously has to be long enough to suit the 34T cassette, so a few links need to be added onto the existing chain. The extra chain length (+6 links) will not be an issue as the longer cage can take care of that.

Areas to take note is the indexing of the rear derailleur on the cassette, as each cassette's position might differ slightly. If they are close enough, shifting performance should be good enough across the two different cassettes and wheelsets.

With the 11-34T HG800 cassette and GRX rear derailleur installed on the Canyon Endurace. 

Using the GRX rear derailleur means that the Dura-Ace groupset is incomplete, as the Dura-Ace rear derailleur is no longer used. For me, this is OK as I am no longer obsessed with the weight of the Canyon Endurace any more, unlike previously when it was new.  Besides, using the gravel wheelset and tires already add much more weight than the little difference a change of rear derailleur makes.

Testing the gravel setup!

Wednesday, November 6, 2019

Canyon Endurace: Panaracer GravelKing SK Tires

After reviewing the DT Swiss G 1800 gravel wheelset, now we need to select the correct gravel tires to fit the Canyon Endurace. As mentioned earlier, the Canyon Endurace is not designed as a gravel bike, but since it has a pretty generous tire clearance, I think it is possible to convert it into a light gravel bike with a change of wheelset.

The challenge now lies in selecting the widest gravel tire that can fit into the frame. As you may already know, the actual tire width will differ from the claimed tire width, depending on the width of the rim. A very good example is the Continental GP4000 tires mounted on the Reynolds Assault wheelset. The claimed tire width of 28 mm has an actual tire width of about 32 mm when mounted on the wheels with internal rim width of 21 mm.

Continental GP4000 28 mm tire + 21 mm rim => 32 mm actual width (+4 mm)

Plenty of tire clearance at the front fork around the 32 mm wide (actual width) GP4000 tire.

Since there is no bridge between the seat stays for a caliper brake, there is plenty of tire clearance here as well.

To further complicate things, different tire manufacturers may have different standards for indicating tire width. A 28 mm wide tire from manufacturer A and B may be different.

With all that in mind, I tried to estimate the final tire width as best as I could, with limited information. The smallest frame clearance on the Canyon Endurace is between the chain stays, which has a maximum width of about 40 mm as measured.This means that the widest tire that I can safely fit is probably about 36 mm, with a 2 mm margin between the tire and the frame.

With 32 mm wide tires, there is about 4 mm of clearance between the tire and the chain stay on both sides.

The DT Swiss G 1800 rim has an internal width of 24 mm, which is considered wide even by gravel wheelset standards. If I were to get a 35 mm wide gravel tire, it is very likely that it will turn out even wider, making it too wide to fit on the Canyon Endurace.

Therefore, I needed a narrower tire width (as claimed by the manufacturer), which will turn out wider once installed on the wide gravel rims.

Based on some information from this discussion thread, I guessed that if I were to use a 32 mm wide tire (manufacturer claim) on the 24 mm rim, I would get something like 36 mm actual tire width.

32 mm gravel tire + 24 mm rim => ??mm actual width
Based on around 4 mm of extra width, I think the final tire width will be about 36 mm.

There are also many gravel tires to choose from, but based on many reviews, the Panaracer GravelKing SK tires seem to be really good and suits my purpose. There are tires with less knobs, but the grip does not seem to be sufficient. On the other hand, there are tires with really large knobs, but those are for muddy conditions, and I don't intend to ride in muddy conditions. My intention is to ride on unpaved trails in dry conditions or on actual gravel, therefore a tire with small knobs should be suitable. The GravelKing SK (Small Knobs) fulfills my requirements and it also comes in the width that I need.

Panaracer GravelKing SK Tires

Closer look at the features of the tire.

I chose the brown wall version, to have that gravel look. A black wall version would look almost the same as a normal road bike tire.

Claimed width is 32 mm, let's see what the actual width is once mounted. Max tire pressure with inner tube is 94 PSI. If it is used as a tubeless tire, the max tire pressure is 58 PSI.

Closely spaced knobs in the middle for lower rolling resistance, wider and angled knobs at the edges for better grip during cornering.

Each tire weighs 317 grams, which is quite lightweight for a gravel tire, as GP4000 tires (28 mm) weigh about 266 grams each. This is mainly due to the folding bead which saves a lot of weight over a metal wire bead.

For now, inner tubes will be used. Schwalbe SV17 tubes can be used for 28 mm up to 47 mm wide tires, making it very versatile. This inner tube can be used for both the GP4000 and the GravelKing tires.

The SV17 inner tube with 40 mm valve weighs 154 grams.

Here is how it looks with the tires mounted on the wheels! I like the brown side walls which makes it look different.

Actual tire width is measured to be 35 mm, up from the claimed tire width of 32 mm.

Comparing the GP4000 tires with the new GravelKing tires. Looks totally different!

How the two different wheelsets will look with the different tires.

With an actual tire width of 35 mm, it will fit into the Canyon Endurace frame, with a clearance of around 2.5 mm on either side at the chain stay area. At other areas on the frame (seat stay, front fork), the clearance will be bigger which is no problem.

Panaracer GravelKing 32 mm tire + 24 mm rim => 35 mm actual width (+3 mm)

With the wheelset and tires settled, the next components to prepare would be the cassette and rear derailleur, to complete the gravel setup.

Sunday, October 27, 2019

Canyon Endurace: DT Swiss G 1800 Spline DB 25 Gravel Wheelset

The hottest and fastest growing bike segment right now is the gravel riding scene, with almost all bike brands producing their own gravel bike frames for gravel riding.

What exactly is gravel riding? To sum in up in one word: Fun!

Gravel riding! Picture from Scott Sports.

Gravel riding does not mean just riding on gravel, it is broadly defined as going off-road on a road bike. A gravel bike looks 90% like a standard road bike, with drop bars on a road bike frame. However, one key difference here is the type of tire that is used.

For gravel bikes that are designed to go for some light off-road, the tires have some rubber knobs for better traction when going off road, similar to mountain bike tires but with less aggressive treads. The tire width and thus volume is also much larger, from 32 mm wide to even 50 mm wide (2 inches!). Correspondingly, the tire pressure is also much lower, and many people run tubeless setups to improve puncture recovery and increase traction.

Other than the tires, the gearing is also lower, to allow easy pedaling even over steep slopes or rough terrain. A front single (1x) setup is also popular, as wide range cassettes can be used for a wide gear range, even if there are larger steps between gears. This is acceptable as close gear ratios are not so important for gravel riding.

Of course, the frame must be able to support wide tires, the wider the better. In order to get a large and wide tire without increasing the wheel diameter too much, some are using 650b wheels, which are smaller than 700c wheels. These 650b wheels, when matched with large 45 - 50 mm wide tires, have an external diameter similar to 700c wheels with narrower tires.

With wide gravel tires on 650b wheels! Looks really comfortable.

Disc brakes are a given, as that is the only way to allow wide tires and rims on the frame. Caliper brakes are not used as they cannot accommodate wide tires. Besides, hydraulic disc brakes work so much better, especially when going off-road.

And that defines gravel riding! If I were to sum it up in one sentence, it is to ride light off-road trails on a road bike, with some gravel specific components to improve the riding experience and capability of the bike. It is less serious than road riding, where it is usually about going fast and long. It is also less intimidating than serious off-road riding, where it can get very technical and challenging, especially for the unskilled rider.

Most road bikes cannot be converted to gravel bikes, as the frame clearance is too small to fit in wider tires. However, I found that the Canyon Endurace that I have is different!

Being an endurance road bike, it is blessed with larger-than-normal tire clearance. Officially from Canyon, the maximum tire clearance on the Endurace CF SLX frame is 30 mm, but in actual fact, it is much wider. The Canyon Endurace came stock with the Reynolds Assault Limited Edition wheelset, with 28 mm Continental GP4000 tires. As those rims are relatively wide (21 mm), the actual width of the GP4000 tires become about 32 mm in reality. This stock condition  already exceeds the maximum of 30 mm width as claimed by Canyon.

Even so, there is still a good 4-5 mm of clearance on either side of the tire, at the narrowest area (chain stay clearance). At other areas (seat stay, front fork, etc) the clearance is even wider. This is with the 32 mm wide GP4000 tires.

Still a good amount of tire clearance with 32 mm wide GP4000 tires.

With this realization, I had a plan to convert the Canyon Endurace to a gravel bike. Not a serious gravel bike with extra wide tires (>40 mm), as that is not possible, but sort of a light gravel bike with maybe 35 mm wide tires. At the same time, I want to use it as a road bike as well.

Instead of building a completely new gravel bike from scratch, I decided to modify the Canyon Endurace, so that I can swap in a gravel wheelset (complete with tires, cassette, disc brake rotors) and convert it from a road bike to a gravel bike. In other words, I will have a separate gravel wheelset that I can swap in to make it a gravel bike, without touching or adjusting any other parts of the bike.

Is it possible? Let's find out!

My plan is to have a totally independent wheelset, that can be swapped in to the Canyon Endurace, without using any tools. This will allow the bike conversion to be done easily in just a couple of minutes. Details to be shared in later posts.

First, we need a new gravel wheelset! Since a 650b wheelset needs to be paired to a wide tire, it is not possible in my case due to limited frame clearance. Therefore, a 700c wheelset will be used, just with wider tires (as wide as the frame will allow!).

To get more tire volume, a wide rim is recommended, instead of putting a wide tire on a narrow rim and creating a mushroom shape that can be unstable during cornering. Therefore, I looked for a gravel wheelset with wide rims.

As you already know, DT Swiss is one of the leading wheel manufacturing companies, and they recently launched the gravel wheelset lineup. My timing is perfect! There are 3 tiers of gravel wheels from DT Swiss:

GRC 1400: Best hubs, carbon rims, lowest weight.
GR 1600: Good hubs, aluminium rims, mid range offering.
G 1800: Decent hubs, aluminium rims, more budget friendly option. Also the heaviest.

With this 3 tier selection, there is a wheelset to suit different usage and budget. For me, carbon rims are not preferred due to risk of stone damage when riding off-road, and it can become an expensive mistake. The GR 1600 is nice, but still too pricey in this case as I don't need the lightest setup for racing. Therefore I settled for the G 1800 wheelset which is more wallet friendly. At this point, I am still not sure if I will like the gravel setup or not.

DT Swiss G 1800 gravel wheelset, 700c size. 24 spokes each for the front and rear wheels.

Nice decals, similar to other DT Swiss wheels that I have used previously.

Tubeless ready rim tape already installed.

The bead type is hooked, which creates a more secure fit between the tire and the rim. There is a central channel with a smaller diameter to allow the tire to be removed more easily.

Claimed internal rim width is 24 mm! Wider than the 21 mm on the Reynolds Assault wheelset.

Internal rim width is measured to be about 24 mm.

External rim width is measured to be about 28 mm.

Rim height is about 25 mm. No need for a tall rim for aerodynamic advantage as I will mostly be riding slowly on the trail.

Centerlock interface for use with Centerlock disc brake rotors. Much easier to remove and install as compared to 6 bolt rotors. 12 mm E-Thru axle type to match the frame.

11 speed freehub body. Pawl engagement is every 15 degrees (24 clicks per round) which is not so ideal. 12 mm E-Thru axle type to match the frame.

Front wheel weighs 864 grams, which is about 100 grams more than the 763 grams of the Reynolds Assault front wheel.

Rear wheel weighs 1005 grams, which is about 130 grams more than the 874 grams of the Reynolds Assault rear wheel.

This G 1800 wheelset comes with all the attachments and adapters that you need, to make it compatible to virtually every road bike frame.

Adapter contents:
1) 6 bolt to centerlock adapters
2) Front wheel adapter for 15 mm E-Thru axle type
3) Front wheel adapter for 5 mm Quick Release axle type
4) Rear wheel adapter for 5 mm Quick Release axle type
5) SRAM XD Driver for rear wheel + end cap
6) Tubeless valves

Next time, if I want to use a SRAM XD cassette, or use the wheelset on other bike frames, it is possible with the use of these adapters.

Next, we need to get the correct gravel tires, but that is a story for the next blog post...