Cervelo Aspero: Bike Servicing after Dusty Gravel Ride

This dusty gravel ride was actually done last year in 2021, just that I didn't get around to writing about it until now. For those who do not know, the trail around Pandan Reservoir is made of light gravel, with small stones that are doable for most bikes.

Using a gravel bike is nice, but it is actually not necessary. Road bikes with wider tires (> 28 mm) are fine as well as I have tested with my Focus Paralane. That said, it is a good place to test out gravel bikes with some fast riding, as it is an unbroken stretch of gravel that you can ride round and round.

Approximate distance for one round is about 6 km, which is easily done on a bike but takes some effort if you are jogging.

One quirk of this gravel trail is the dusty conditions. When the trail is dry, it actually generates quite a bit of dust as you ride over it. The result is a bike that is entirely coated in a fine layer of dust, as you will see below.

Cervelo Aspero gravel bike with Giant TCR Advanced Disc 2 road bike.

Cervelo Aspero: Front Single Road and Gravel Drivetrain

From the first set up of the Cervelo Aspero, where I first used a 2x11 speed drivetrain for road and gravel riding, I have now changed to a dedicated 1x11 speed gravel drivetrain.

The Aspero is now a dedicated gravel bike, which is why I have changed some of the components to make it more suitable for gravel riding, instead of striking a balance previously between road and gravel usage.

Other than the drivetrain, I have also changed to the GRX Di2 shifters, which has ergonomics that are very well suited for gravel riding. The default wheelset is also the excellent Hunt 650B carbon wheelset, with WTB Venture 47 tires.

That said, if I want to, I can still swap it to a road wheelset, if I ever want to ride fast on the road with this Cervelo Aspero. This is because the Ascent Bikes Zenith Elite wheelset is using the Sunrace RX1 11-36T cassette, which is relatively similar in size to the SLX CS-M7000 11-42T cassette on the Hunt wheelset. Previously I have swapped between the 11-30T cassette and the 11-36T cassette, without adjusting the rear derailleur at all, so I think swapping between the 11-36T and 11-42T cassette is possible.

Default gravel wheelset on the left (Hunt 650B + Venture 47 tires + 11-42T cassette) and the road wheelset on the right (Zenith Elite + GP5000 tires + 11-36T cassette).

From the picture above, you can see that the external wheel diameters are similar. This post shows the size difference in detail. The Zenith Elite carbon wheelset is currently being used on the Focus Paralane, as my all-weather commuting road bike.

Road wheelset with 11-36T cassette installed on the Cervelo Aspero.

Distance between the largest 36T sprocket and the guide pulley is a little further, since the rear derailleur is set for a 42T large sprocket. However, shifting is still OK.

Looks good as a road bike too!

With a carbon road wheelset, this Aspero can be converted into a pretty fast bike as well. It is only limited by the small 38T chain ring, which is good for gravel riding but rather small for road riding.

Full specifications of the Cervelo Aspero in road setup. Weighs about 7.5 kg without pedals.

As for the gravel setup, it will definitely be heavier, due to the heavier wheelset and larger cassette.

Installed the XTR RT-MT900 rotors onto the Hunt wheelset.

For a comparison of MT900 vs MT800 rotors, check out this article.

Full gravel setup

I think this setup is perfect for gravel riding!

The gravel setup weighs about 8.1 kg without pedals, with the additional 600 grams of weight coming from the wheelset.

Although it is possible for this Aspero to be set up as a road bike as shown above, it is not so likely that I will use it for road riding. I would just take the Focus Paralane instead, as it has more road specific components, such as a slightly larger chain ring and road shifters.

In any case, this Aspero is so versatile that it can be setup as a full road bike or full gravel bike, or anything in between.

Cervelo Aspero: 650B and 700C Gravel Wheelset Comparison

Since I now have both a 700C and 650B wheelset for my Cervelo Aspero gravel bike, it is a good chance to do a side-by-side comparison. This will be useful for those who cannot decide between a 700C or 650B gravel wheelset.

As the wheels are different, the weight comparison is merely for reference. The Hunt 650B Adventure Carbon Disc wheelset is one of the best 650B wheels around, and is also very lightweight. On the other hand, the DT Swiss G 1800 wheelset is a basic aluminium gravel wheelset that is rather heavy.

650B wheel on the left, with brown sidewall WTB Venture 47 tires.

Both are using 11-42T 11 speed MTB cassettes.

650B wheel with WTB Venture 47 tires have a diameter of 681 mm.

700C wheel with WTB Byway tires have a diameter of 698 mm.

As you can see, there is a diameter difference of about 17 mm between these two wheelsets. It is expected, and this size difference will mean a different axle-to-ground height, and also BB ground clearance. The ride characteristic will also be slightly different, which is where the Trail Mixer position may be used to adjust the ride feeling.

Axle centre differs by about 8.5 mm, which is about half the diameter difference of 17 mm.

700C wheelset is noticeably larger than the 650B wheelset.

Very different tire treads. Smooth centreline on the 700C Byway, and grippy treads on the 650B Venture 47.

Tire width is different, as a smaller 650B tire can have a wider tire compared to a 700C tire, without frame interference.

Venture 47 measures true to size at 47 mm, on a 24 mm internal rim.

Byway measures 37 mm on a 24 mm internal rim, smaller than the claimed 40 mm width. I'm OK with this width as it is midway between the 27.5 mm GP5000 road tire and the 47 mm Venture 47 tire.

The 700C Byway has a tire width that is 10 mm narrower than the 650B Venture 47, which may or may not be a good thing. I'm hoping that the smooth centreline on the Byway will give me low rolling resistance on tarmac.

The height of the tire sidewall is very different. The black areas are about the same height, but the 650B tire has an additional brown sidewall height which adds a lot to the air volume inside the tire.

DT Swiss G 1800 front wheel with Byway tire and rotor weighs 1600 grams, which is quite heavy. Also partly because I am using inner tubes.

Hunt 650B carbon front wheel with Venture 47 tire and rotor weighs less, at 1448 grams. Although the tire is heavier, the carbon rim and tubeless setup saves quite a bit of weight.

DT Swiss G 1800 rear wheel with rotor and cassette weighs 2224 grams, which is also heavy.

Hunt 650B rear wheel with rotor and cassette weighs less at 2036 grams.

700C wheelset weight is thus 3824 grams, while the 650B wheelset weighs 3484 grams. If I used a high end carbon rim for the 700C wheel, plus tubeless setup, the final weight will be lighter than the 650B wheelset, as the 700C tires are usually lighter.

Main Differences:

1) 700C tire width is 10 mm narrower than the 650B tire.

2) 700C tire diameter is 17 mm larger than the 650B tire.

3) 700C wheelset is 340 grams heavier than the 650B wheelset.

4) 700C tire has a smooth centreline tread, which should make it roll smoother on tarmac.

It is nice to compare the specifications, but the final test is how well it rides on the road. For this 700C gravel wheelset, I need it to ride well on the road, while also being wide and grippy enough to handle some light gravel.

After extensive testing on the road and gravel, I found that this 700C gravel wheelset is rather disappointing. My expectation was smooth rolling on tarmac, due to the smooth centreline in the middle of the Byway tire. However, I could still feel a significant amount of drag, and it feels pretty slow to accelerate or cruise. In fact, my 650B wheelset feels even faster, even though the Venture 47 tire has a more knobbly tire on it. It could be due to the heavier DT Swiss G 1800 wheelset, instead of the Byway tire. Hard to conclude unless I put the Byway tires onto a lightweight set of 700C carbon gravel wheels to compare again.

As for light gravel riding, the Byway tire also does not perform very well. Due to the smooth centreline, it does not have sufficient grip. Compared to the 650B tires, I have to slow down a lot more on loose corners, to avoid sliding during cornering. This makes it a relatively poor gravel tire as well.

I just came across an article reviewing this exact tire, and the conclusion was the same as what I discovered. The rolling resistance was quite high, which is unexpected since there is a smooth centreline that is supposed to reduce rolling resistance.

In all, this Byway 700C tire is neither fast rolling on road, and also not grippy enough for proper gravel riding. I'm sure there are some good 700C gravel tires out there, but this is not the one. Unfortunately this 700C tire does not provide the characteristics that I want, so it is back to the 650B gravel wheelset on my Cervelo Aspero gravel bike.

Cervelo Aspero: Road vs Gravel Setup

As you already know by now, my Cervelo Aspero is a dual use bike, which means that it can be both a road bike and a gravel bike. This only requires a wheelset swap, as already demonstrated successfully on the Canyon Endurace.

Although the Cervelo Aspero is designed as a fast gravel bike, there is no reason why it cannot be a good road bike as well. All it needs is a fast set of high profile carbon road wheels and smooth rolling road tires. The frame geometry is very similar to that of an endurance road bike, which means it is not too upright for fast rides. Even though the frameset is quite a bit heavier than the Canyon Endurace, it is acceptable as it is not meant to be a pure climbing bike.

The road wheelset is the same old Reynolds Assault Limited Edition Disc wheelset that came stock with the Canyon Endurace, with Continental GP4000 28 mm wide tires. The actual tire width is about 32 mm due to the wide 21 mm internal rim width. This is a good wheelset that I like very much.

On the other hand, the gravel wheelset that I will use on the Aspero is the new Hunt 650B Adventure Carbon Disc wheelset, with 43 mm wide Panaracer GravelKing SK tires. Although the previous DT Swiss G 1800 gravel wheelset was good, it is for 700C tires, which is not what I want on the Aspero. Instead, I want to take maximum advantage of the big tire clearance on the Aspero, which is why I will use 650B wheels and wide tires.

As shown below, the road wheelset and gravel wheelset are different, which means that I do not need to compromise a single wheelset and tire to fit both road and gravel riding. The road wheelset can be optimized for fast road riding, while the gravel wheelset will be optimized for comfort and traction during off-road riding.

650B wheels are visibly smaller than the 700C wheels. The taller 650B tire is not enough to make up for the difference in rim diameter.

Cassette and Rotor Comparison

Road wheels use a Dura-Ace 11-30T cassette and a Dura-Ace RT900 160 mm diameter disc rotor.

Gravel wheels use a HG800 11-34T cassette and a Deore XT RT800 disc rotor, also 160 mm diameter.

Front Wheel Comparison

Road front wheel, with high profile rim and road tires.

Gravel front wheel, with a smaller 650B low profile rim, but high volume gravel tires.

It is necessary to use the same size of disc brake rotors and number of speeds on the cassette, if you plan to swap wheels like this. Remember, the idea is to make it as fuss-free as possible to convert between a road and gravel bike setup, with just a wheelset change. No adjustment should be needed.

On both wheelsets, the rotor is located at almost the same position, and I was able to setup the brake calipers to accommodate that. Therefore, there is no brake rotor rubbing when swapping between these two wheelsets.


Front Fork Tire Clearance Comparison

Lots of tire clearance at the fork around the 700C road bike tire. This frame can accept up to 700Cx42 mm wide tires.

Lots of clearance radially, when using the smaller diameter 650Bx43 mm tire.

Rear Wheel Setup Comparison

Road rear wheel

Road rear wheel with 11-30T cassette, using the GRX rear derailleur.

Gravel rear wheel with 11-34T cassette, also using the same GRX rear derailleur. There is no need to adjust the rear derailleur setting after swapping wheels.

Rear Chain Stay and Seat Stay Clearance Comparison

Still plenty of tire clearance at the seat stay area, around the wide gravel tires. There will be even more clearance when the road tires are used.

Still lots of clearance around the rear road tire, along the seat tube and the chain stays.

For the gravel tire, there is more clearance with the seat tube due to the smaller tire diameter, but lesser clearance with the chain stays as the gravel tire is wider.

In the picture above, notice that the 4iiii power meter on the left side crank arm manages to clear the frame. There is actually a healthy amount of clearance with the left side chain stay. In fact, there is more clearance than on the Canyon Endurace frame (shown below).

Small clearance between the left side chain stay and the power meter, on the Canyon Endurace.

Initially I thought that the left side chain stay is pushed outwards due to the BBright construction. However, later I realized that it is actually the same as the standard press fit BB construction. At the same time, the left side chain stay also needs to be moved outwards to give wider tire clearance. In summary, the Cervelo Aspero can accommodate wide tires, and still have enough clearance for a left crank arm power meter!

Non drive side view of the road setup

Non drive side view of the gravel setup.

Drive side view of the road setup

Drive side view of the gravel setup

As you can see from the pictures, only the wheelset is changed between the road setup and the gravel setup. Visually it looks quite different, especially the tires. However, the drivetrain is almost completely the same, except for the cassette.

Due to the different tire diameter, the clearance between the bottom bracket and the ground is also different. The gravel setup has lesser ground clearance due to the smaller tire diameter.

There is a diameter difference of 16 mm between these two tires. Therefore, the radial difference is 8 mm. This 8 mm will be the difference in axle height from the ground, and also the bottom bracket distance from the ground. Tire deflection under rider's load is not accounted for in this case.

BB to ground distance for Continental GP4000 road tires (700C x 28): 268 mm
BB to ground distance for Panaracer GravelKing SK gravel tires (650B x 43): 260 mm

The ground clearance of 260 mm may seem to be too low, but it does not give me any problems. I don't encounter pedal strikes when leaning over on gravel or on smooth tarmac. This is likely helped by my usage of 165 mm crank arms, which are 5 mm shorter than the more common 170 mm crank arm length.

Cervelo Aspero: 700C vs 650B Wheel Size Comparison - Part 1

Before I tried gravel riding, there was no need to consider wheel size or tire width. Basically, a road bike setup means using a 700C x 25 or 28 mm tire. The tire diameter or width is just what it is, there is no concern if the tire ends up a bit wider or narrower than claimed, or even a bit bigger or smaller in diameter.

However, when I first used a gravel setup on the Canyon Endurace, I found that depending on the tire width, the tire diameter will also be affected significantly, especially if the tire width differs a lot. This can be a problem, as a bike is designed around a nominal wheel size, with only a small variance allowed. If the wheel size differs too much, it affects the geometry of the bike.

Crank clearance with the ground will be reduced if the tire diameter is smaller. Also, the trail of the bike will be reduced with a smaller wheel size, which can cause instability.

If the tire diameter is larger, the usual problem is frame or fork clearance, but the bigger issue is a slower handling bike due to larger trail from the larger tire size. This may be good or bad depending on your desired purpose.

In this case, it is difficult for the bike frame designer to optimize for a single wheel size, if it needs to accommodate a wide range of tire diameters, from small 700C x 23 to large 700C x 43 mm, for example.

Which is why the Cervelo Aspero has a Trail Mixer on the fork which allows the trail value of the bike to be adjusted, depending on the wheel size and also your preference for a more agile or more stable bike.

I will not go through the explanation again on why I chose 650B wheels and tires, you can read about it in my previous posts.

DT Swiss G 1800 Spline DB 25 Wheelset
Panaracer GravelKing SK 700C x 32 Tires

Hunt 650B Adventure Carbon Disc Wheelset
Panaracer GravelKing SK 650B x 43 Tires

Before I compare the new 650B wheelset, I will compare the wheels used previously on the Canyon Endurace. That would be the Reynolds Assault carbon wheelset for the road setup, and the DT Swiss G 1800 wheelset for the gravel setup. Both are 700C wheels.

The Reynolds Assault wheelset is equipped with Continental GP4000 700C x 28 tires, but the actual tire width is almost 32 mm. This is due to the relatively wide internal rim width of 21 mm.

The DT Swiss G 1800 wheelset is equipped with Panaracer GravelKing SK 700C x 32 tires, with an actual tire width of 35 mm. This rim has an internal width of 24 mm.

Rim diameter looks almost similar, with the gravel wheelset being just a little big larger.

Close up look at the different tire tread patterns.

Tire diameter is very similar.

In this case, if the tire diameter is almost the same, swapping between the wheelsets will not cause significant differences in ride geometry. This was the case on the Canyon Endurace.

Moving on to the new Hunt 650B wheelset, the rim diameter is smaller, but the tire will add back some of the diameter by having a taller sidewall. A 700C rim has an outer diameter of 622 mm, while a 650B rim has an outer diameter of 584 mm. This is a difference of 38 mm, which means 19 mm on either side. If a 650B tire is to have the same outer diameter as a 700C tire, the side wall needs to be 19 mm taller, which is a huge difference.

650B x 43 mm tire on the left, 700C x 32C tire (actual 35 mm) on the right. The diameter difference is quite obvious.

The 650B wheelset on the right has a smaller diameter, as seen from the difference in axle height. This will also be the difference in bottom bracket or crank arm clearance.

Another view showing the difference in tire diameter.

Using a long thru axle to align the centre of the hubs, the difference in radius can be measured more accurately.

650B tire has a gap with the ground. Multiply this gap by 2 and you get the diameter difference.

Using a 10 mm Allen key as a gauge, there is still a tiny bit of clearance. I would say that the gap is about 11 mm.

Other than the diameter difference, there is a big tire width difference as well. The wider 650B tire on the right has 5 rows of small knobs instead of 3.

43 mm width on the left, versus 35 mm (actual) width on the right. This 8 mm width difference is quite obvious.

There is some difference in sidewall height, as the 650B tire on the left will have a taller side wall as it is wider. The height of the brown sidewall area is about the same, but the black sidewall area is much taller on the 650B tire.

Finally, let's also compare the 700C road wheelset with the new 650B gravel wheelset. These are the two wheelsets that I will use on the Cervelo Aspero. I will explain more about the road and gravel setup in a later post.

Hunt 650B wheelset on the left, for gravel riding. Reynolds Assault 700C wheelset on the right for road riding.

Significant difference in tire diameter between these two wheelsets.

Another view of the different tire diameter. Despite the wider tire width, the 650B tire does not add enough tire height to come close to the 700C tire diameter.

Difference in axle height, which is about 8 mm.

Big difference in tire width and tread pattern. 32 mm tire width vs 43 mm tire width.

Comparison of the tire sidewall height. The 650B tire is taller with much more volume, but not enough to make up for the smaller rim diameter.

In summary, here are the tire diameters as measured, and also the difference in BB to ground distance (which is calculated as half the difference in tire diameter).

Continental GP4000 700C x 28 (actual 32): 695 mm diameter
Panaracer GravelKing SK 700C x 32 (actual 35): 699 mm diameter
Panaracer GravelKing SK 650B x 43: 677 mm diameter

On Cervelo Aspero (Size 51)
BB to ground distance for Continental GP4000 (700C x 28): 268 mm
BB to ground distance for GravelKing SK (700C x 32): 270 mm
BB to ground distance for GravelKing SK (650B x 43): 259 mm

The differences between the 700C road and 700C gravel tires are small, while there is a big difference between the 700C road and 650B gravel tire. What does this mean?

Swapping from the 700C road wheelset to the 650B gravel wheelset will lower the bike by about 9 mm. That is 9 mm less crank arm clearance. Not sure if pedal strike will be an issue, as it has even lesser ground clearance compared to my other bikes.

On the plus side, a lower centre of gravity will help in cornering and descending at speed. A smaller tire diameter also means a lower trail value, which increases agility. Is increased agility good or bad for a gravel bike? This is up for debate, as increased agility can allow you to tackle twisty trails more easily, but also make a speedy descent less stable.

Regardless, the proof of the ride quality will require actual riding. Whether good or not, I will have to use the tires to see if it is suitable for my usage.

From left to right: GP4000 28 mm, GravelKing 43 mm, GravelKing 32 mm

The 650B wheelset is the junior here, having a smaller diameter than the other two.

This concludes the first part of this comparison, which is between these three tires. Later on, in Part 2, there will be an additional tire added to this comparison, stay tuned!