Cervelo Aspero: Continental GP5000 Tires

In the previous post, I shared the new Ascent Bikes Zenith Elite carbon wheelset, which is my new 50 mm high profile carbon wheelset for fast road riding on the Cervelo Aspero. At the same time, I decided to change to a new set of tires as well, as the Continental GP4000 tires that came with the Reynolds Assault Limited Edition wheelset has about 3 years on it already.

Although the mileage is not high, I would like to get new tires, as they tend to lose their suppleness with age. We all know it is just an excuse to get new tires...

The latest generation of Continental road tires is the GP5000, which is an improved version of the very popular GP4000. Let's see what is the difference!

Continental GP5000 tires, also in the same 28 mm width as the previous GP4000 tires.

List of features that always includes better grip, better puncture resistance, lower rolling resistance, lower weight, etc.

Estimated tire circumference and maximum tire pressure for each tire width spec.

Weighs just 238 grams each! This is the clincher version, which would be lighter than the tubeless version.

In comparison, the old GP4000 tire in the same 28 mm width weighs more at 260 grams each.

Was there any magic formula that allowed the tire weight to be reduced from 260 to 238 grams? Short of making the tread or side walls any thinner, the tire can also be made to be narrower. Which is exactly what happened, even though both are rated as 28 mm wide tires.

GP5000 in front, GP4000 behind. Left side bead is aligned, but the GP4000 is wider by about 5 mm on the right side bead.

Although both are listed as 28 mm wide tires, they are from different generations, quite a few years apart. As such, they are designed based on different rim widths.

The old GP4000 was designed some years ago, when internal widths for road rims was still a conservative 15 mm wide. If the GP4000 28 mm tire was installed on a rim with internal width of 15 mm, the actual tire width should be close to the listed 28 mm. Therefore, when installed on wide modern rims, the tires become well over-sized.

Old GP4000 28 mm tires become 32 mm when mounted on the 21 mm internal rim width Reynolds wheelset. 4 mm oversized, which is also the stock condition from the Canyon Endurace.

The GP4000 tires bulge out from the rim visibly, as the actual tire width is 32 mm.

Another view showing the 32 mm tire width bulging from the rim.

New inner tubes to match the new GP5000 tires and new Zenith Elite wheelset. Which inner tube should I use?

The Continental inner tubes on the right are a bit wider (can't see from this view), and they came free with the pair of GP5000 tires.

Schwalbe SV15 with 60 mm valve weighs 110 grams.

Continental inner tube weighs more at 133 grams.

I decided to save some weight by using the lighter Schwalbe SV15 inner tubes. Let's see what is the actual width of the new GP5000 28 mm tires, when mounted on the Reynolds rim (21 mm internal) and also the new Zenith Elite rims (17 mm internal).

GP5000 28 mm tire on 21 mm internal rim width. Actual tire width is slightly over-sized at 28.5 mm.

GP5000 28 mm tire is about flush with the external rim width

GP5000 tire does not bulge out from the rim, unlike the GP4000 tire.

Both GP5000 tires installed on the new Zenith Elite rims!

Add a flash, and the Darklight reflective stickers make the rims stand out. 

GP5000 tires on the Ascent Bikes Zenith Elite wheelset.

GP5000 28 mm tire on 17 mm internal rim width gives an actual tire width of 27.5 mm.

Using the new GP5000 tire on the old school rim width of 17 mm actually makes the tire undersized, which is uncommon nowadays.

Just for comparison, the new GP5000 tire + Zenith Elite wheel on the left, and the old GP4000 tire + Reynolds wheel on the right.

Due to the oversized GP4000 tire (in terms of width and also height), the tire diameter is also visibly larger.

The axle height comparison check also shows that the tire diameter of the GP4000 tire on Reynolds wheel is bigger.

50 mm rim profile on the left, with shorter tire height, and a 41 mm rim profile on the right, with a taller tire height.

Final comparison picture, with the GP5000 tire on the left, and GP4000 tire on the right. The width difference is 27.5 mm vs 32 mm, which is quite noticeable when positioned side by side.

I think this was a pretty detailed comparison between the old GP4000 and new GP5000 tires, on the old Reynolds rim and new Zenith Elite rims.

What I learnt was that the old GP4000 tires will be oversized when mounted on anything wider than old school narrow rims of maybe 15-16 mm internal width.

On the other hand, the new GP5000 tires are designed to be matched with wider rims to get the true size. When mounted on old school 17 mm internal width rims, they are actually slightly undersized.

In summary, it is difficult to know exactly what tire width you are going to get, as the different tire designs and rim widths makes it quite unpredictable, until you actually mount it yourself.

Early Rider Seeker 14: Measurements and Weights

After introducing the new kids bike in the previous posts, here is a more detailed analysis of the Early Rider Seeker 14. As it is a kids-specific bike, there are some dimensions that are specially sized to fit smaller kids. Let's find out what they are!

Some kids bikes are using smaller diameter handlebars of 19 mm diameter, instead of the industry standard of 22.2 mm. With a smaller handlebar diameter, the rubber grip can be made smaller to suit smaller hands.

For this bike, a standard handlebar diameter of 22.2 mm was used. There is a tolerance of around +/- 0.2 mm for this dimension.

Within the tolerance of the standard flat handlebar diameter of 22.2 mm.

The grip size is slightly smaller than usual, at less than 30 mm diameter. Usually for adult bikes, the grip diameter is 30-34 mm.

In this case, I would say that the grip design is not really kids specific, as the only noticeable difference is a slightly smaller grip diameter.

On the other hand, the brake levers are special, as they have an extra short reach for small kids hands. 

Special kids brake levers with a different shape for short reach. Does it work?

The pivot is located closer to the handlebar, while there is a grub screw to adjust the lever reach.

Testing with actual kids hand size shows that it works pretty well! My kid is able to reach and activate the brake lever properly.

This brake lever is by Tektro, and the model number is JL350. Hard to find it sold separately though.

The saddle does not have saddle rails for fore/aft or tilt adjustment, the angle is basically fixed.

The saddle size is suitable for kids, but the only adjustment is the seatpost height. Quick release lever is useful.

This Early Rider Seeker 14 kids bike also comes with flat pedals, but I did not install them as I was going to convert it to a balance bike first. I found that these pedals are of really good quality, as the bearings are very smooth, better than what I have seen on other pedals!

Smooth spinning bearings on the pedal axle, which also looks very premium.

Overall pedal width is about 72 mm, and it even has molded pins for grip!

Pedal size (front to back) is about 70 mm, also smaller for kids feet.

As the pedals are relatively small, they are also lightweight at just 200 grams a pair!

By converting it to a balance bike for now, I am able to measure the weight of the drivetrain components, since they have been removed from the bike.

The crank length is just 90 mm, which is good for kids bikes.

As shown in the previous post, the crankset spindle is not connected to either the drive or non-drive side, it is a standalone part. This aluminium spindle weighs 123 grams.

Left crank arm weighs just 85 grams.

Right crankarm with chain ring and chain guard weighs 294 grams.

Wave washer and two crank arm fixing bolts weigh 38 grams.

Full crankset weight is 542 grams.

The bottom bracket weighs 86 grams, and looks very much like a standard Hollowtech II BB.

The BB adapter width is measured to be 10 mm, which makes it a road type BB as previously discovered.

Bottom bracket shell width is 68 mm, which is the road spec. Standard specifications here.

The belt itself is lightweight, at just 58 grams.

No more drivetrain! You can do this with any bike to make it a balance bike.

Weight as a balance bike is just 4.9 kg.

Adding back the weight of the removed components:

Crankset: 542 grams

Bottom Bracket: 86 grams

Belt: 58 grams

4.9 kg + 542 g + 86 g + 58 g = About 5.6 kg, which is the claimed weight of the original full bike without pedals.

For now, it will be used as a balance bike first, to get used to the handling, geometry and brakes. Once my kid is ready, I will reinstall the drivetrain parts, to make it a proper pedal bike.