Bestrider Pump Pro 16: Saddle and Seatpost Upgrade

The Bestrider Pump Pro 16 kids bike came with a decent small saddle for kids, but the lack of adjustability is a problem. Only the saddle height can be adjusted via the seatpost height, while the saddle fore/aft and tilt cannot be adjusted at all. This is because the saddle attaches to the seat post via a pipe-fitting interface (refer to pictures below), instead of using the common saddle rail interface.

Another issue was that this pipe-fitting interface had looseness between the saddle and the seat post which could not be eliminated. To be honest, this kind of interface is not good at all, and only used because it is cheap.

Therefore, to optimize the saddle position for proper riding, I decided to get a new kids-specific saddle for this bike. As the stock seat post does not have a clamp for saddle rails, I also had to get a new seat post at the same time.

I found that it was nearly impossible to get a decent kids saddle that is not too big or with overly-thick cushion. There are very few options available.

Finally I found a source which had this SDG Fly Junior saddle that is highly rated for kids. There was practically no second option for a good quality kids saddle.

SDG Fly Junior kids saddle!

Some of the features of this saddle.

It was not available in red to match the bike frame, nor all-black. Therefore I had to settle for orange colour.

Standard saddle construction with normal saddle rails.

Tough side material to prevent scuffing when the bike is rested against the ground or wall.

Comparing it to a standard adult road saddle.

Although it is shorter than the adult saddle, it can actually be even shorter and will still be fine.

Narrower to suit the kids' narrower sit bones. You will be surprised how many kids saddles are too wide.

Comparing the shape of the stock saddle (on the left) with the new saddle. Original saddle is even shorter.

Stock saddle has a large plastic bottom shell which matches with the stock seat post. This is what I meant by pipe-fitting interface.

Stock saddle has a cutout at the rear of the saddle, for an adult to hold the saddle using fingers when guiding the kid on the bike.

Stock saddle is chunkier as well, with a very thick and soft cushion.

As for the seat post, a standard 27.2 mm diameter seat post is needed. Since I already had the carbon handlebars, I might as well get a carbon seat post as well. There are many available online, but I decided to get one from Toseek which is of better quality. I'm not too concerned about the strength of these carbon seat posts, because it will only need to take a kid's weight and not an adult. Also, as long as you don't get the super lightweight type, the strength is usually more than sufficient as they will just use more carbon to ensure sufficient strength. The risk comes when you buy lightweight carbon parts from unknown sources.

New carbon seat post! Definitely needs to be cut to fit the kids bike frame.

Dual bolt top and bottom clamp, pretty standard stuff. However, the resting surface for the saddle rails is rather short as it is limited to the centre portion.

Standard bolt and clamp interface, similar to Litepro seatposts.

There is actually an open slot at one of the clamping areas, which is not such an ideal design. I did not notice this when I ordered the seat post.

Wall thickness is equal around the circumference, and more than thick enough.

Weighs 221 grams, which is decent but not really lightweight for a carbon seat post. That's perfectly fine as I don't need to worry about insufficient strength.

After measuring and cutting off almost 90 mm of seat post...

...the seat post weight is now reduced to 194 grams which is great.

New SDG Fly Junior saddle is 260 grams which is so-so. I expected it to be lighter as it is smaller than the usual adult saddles.

New saddle plus new seat post weighs 454 grams.

Stock seat post and saddle only weighs 254 grams! That is really very lightweight.

A lot of the seat post weight comes from the saddle clamp area, not the aluminium or carbon tube. Also, the steel saddle rails on the saddle accounts for a lot of the saddle weight as well. The stock seat post and saddle design eliminates both of these heavy components, which allowed it to save a lot of weight. However, this sacrifices the option of saddle adjustability. 

New saddle and seat post installed on the upgraded 3 speed kids bike! Unfortunately the orange saddle does not really match the red frame.

Finally we can adjust the saddle tilt angle...

...and also the fore/aft setting to optimize the pedaling ergonomics.

Overall, this seat post and saddle upgrade actually caused a 200 grams increase in weight, which is unusual. The better saddle quality and position adjustment comes at a cost of heavier weight.

Bestrider Pump Pro 16 (Single Speed)

5.6 kg without pedals and kickstand, in stock condition.

About 6 kg with larger Early Rider pedals (266 g) and kickstand (102 g).

Bestrider Pump Pro 16 (3 Speed)

After upgrading to 3 speed drivetrain, new SDG saddle and seat post.

- 6.6 kg without pedals and kickstand.

- 7.0 kg with Early Rider pedals (266 g) and kickstand (102 g).

At 7.0 kg for a 3 speed kids bike, I think it is a very good weight. Probably very difficult to go any lower unless you change to carbon wheels or carbon frame/fork.

Bestrider Pump Pro 16: Slick Tire Upgrade

The Bestrider Pump Pro 16 came stock with MTB tires, which is very common on kids bikes. It is not that kids are using their bikes for off-road riding. Rather, it is due to the belief that knobbly MTB tires offer better traction, which reduces the chance of skidding and is thus safer for kids.

However, slick tires can actually offer good grip on pavement as well, as the contact area with the ground may be larger than knobbly tires, where only a few blocks are actually in contact with the smooth pavement. Unless the bike is really being used for some off-road riding, I think most kids bikes are actually better off using slick tires that have much lower rolling resistance.

In this case, this kids bike will not be used for off-road riding. It will only be used on pavement and PCN, and so a slick tire will provide a smoother and faster ride with less effort.

Therefore, I searched for a suitable slick tire in the 16 inch 305 wheel size, which is much less common than the 349 wheel size. I found that there is no slick tire in 305 size available from the big brands, such as Schwalbe and Continental. There are more models available from the Chinese brands, such as Kenda, CST, and etc.

However, I was surprised to find that these cheaper 305 tires are actually quite heavy. For a start, they are only available in wire bead types, which are heavier than those with kevlar beads that are only found on high end tires. Next, many of these tires are still knobbly MTB tires that are heavy, or semi-slick types with grooves and a thick rubber tread and sidewalls.

All of these 305 tires that I found are heavier than the much larger Continental GP5000 tires which are only 238 grams each. Of course, the width and price differs greatly, but what I found was that there is probably no market demand for a lightweight 305 slick tire.

Finally, I found a relatively lightweight 305 slick tire from CST, which stands for Cheng Shin Tire. Let's check out these new tires and compare it to the stock tires.

New 40-305 tires from CST. This brand is very common on mid-range to entry level bikes.

Relatively thinner sidewalls help to reduce the tire weight.

Claimed width is 40 mm or 1.50 inches. It will vary depending on the rim width.

Recommended tire pressure is 60 to 100 PSI, which seems very high given the width. Definitely can go lower if used on a kids bike.

Actual tread pattern, with a smooth centre tread and some side grooves. This was the smoothest 305 slick tire I could find.

Comparing it to the stock knobbly MTB tire, it is completely different!

Quite a big difference in tire width. Actual width to be shown later.

Stock tire is 305 grams. This is surprisingly light, as many of the 305 tires that I came across are heavier despite being less knobbly.

New CST tire is lighter at 260 grams. Still heavier than the much larger 700C GP5000 tire though, which makes me appreciate how much work went into making the lightweight race tires.

Stock inner tube with Schrader valves is 123 grams.

I took the chance to change the inner tubes as well, to use Presta valves instead. This would allow me to pump all the bike tires in my stable without having to change pump heads.

Slimmer inner tubes to match the slimmer tires.

New CST inner tubes with Presta valves are 102 grams each.

Since I will be replacing both the tires, I took the chance to weigh the front wheel as well. 413 grams for this 305 front wheel.

Instead of having a quick release axle pass through the hub axle, the wheel is bolted to the front fork by bolts on either side of the fork. Apparently this is a safety feature on kids bikes.

Stock MTB tire has a width of about 44 mm on the Inter-3 wheel, and 46 mm on the original wheel.

If the side knobs are included, the width is 49 mm. Even wider than my 650B gravel tires!

With the new CST slick tires, the tire width is greatly reduced to 36 mm.

As expected, the actual tire width differs from the claimed tire width of 40 mm, but it is OK. I think this width of 36 mm should be a good balance between low rolling resistance and also safety. Narrower tires for kids bikes are not ideal as they can get stuck in drain cover grilles or grooves in the ground, so I think 36 mm should be OK. For adult bikes, 28 mm road bike tires are common, but it requires attention to ensure that they are not trapped by drain cover grilles.

Outer tire diameter with the slick tires is 390 mm, smaller than the 400 mm with the knobbly tires.

With this change of tire, the effective tire diameter will become smaller, which translates to a lower gear ratio. Also, the slick tire will result in lower rolling resistance compared to the knobbly MTB tire.

Therefore, to maintain a similar gear ratio and to take advantage of the easier pedaling due to slick tires, I decided to change the rear sprocket size as well to ensure that the gearing does not become too light.

Previously I used an 18T sprocket, now a smaller 16T sprocket will be used to compensate for the tire change.

The smaller 16T sprocket saves a tiny bit of weight over the 18T sprocket.

Tire change is completed! Due to the change of sprocket size, I had to tension the chain by moving the rear wheel slightly further back, which requires the rear brake pads to be adjusted as well.

Slick tires on the front wheel as well.

Apart from the flashing due to the molding of the tire, the centreline is smooth with low rolling resistance.

Bike looks quite different with the slick tires. Now instead of looking rugged, it looks faster and more like a race bike.

With this tire change, the bike rides smoother, as I observed during our rides. Not only is it able to roll down slopes more easily without pedaling, the entire cycling experience is more enjoyable without having to work against unnecessary rolling resistance. At the same time, managed to save about 140 grams overall, which is a nice bonus.

Bestrider Pump Pro 16: 305 vs 349 Wheel Size Comparison

After completing the upgrade of the Bestrider Pump Pro 16 from the stock single speed drivetrain to the a 3 speed Nexus internal hub setup, I wanted to understand more about the wheel size.

The 16 inch wheel size used on the Pump Pro 16 has a rim diameter of 305 mm, which is less common than the 349 mm version. Most other bikes with 16 inch wheels use the 349 version, such as the Brompton, the Fnhon Gust, and the United Trifold that I have.

The only other bike that I know of that uses a 16 inch 305 wheel size is the Dahon Curve D3, which was one of the folding bikes that impressed me a lot many years ago, but I could not afford it at that time.

Now, I have the United Trifold with the 16 inch 349 wheels, and this new kids bike with 16 inch 305 wheels, so I can do a side by side comparison.

Wheel in wheel picture

Not exactly a fair comparison, as the tire widths are different, which means a different tire height as well.

The 349 wheelset is larger in diameter, as the rim itself is already larger. 

Difference in axle height, due to the difference in wheel diameter, inclusive of the tire diameter. Note that a change in wheel size on the same frame would result in a different bottom bracket height.

Outer diameter of this 349 wheelset is about 425 mm.

Outer diameter of this 305 wheelset is about 400 mm, which means that the 349 wheelset in this case is about 6% larger in diameter.

If the tires used on both the 349 and 305 wheelsets are the same type with the same width, the diameter difference would be larger. Theoretically speaking, the difference in rim diameter is 44 mm (349 - 305 = 44 mm), which means a radius difference of 22 mm.

In any case, 305 wheels have a limited tire choice, as this wheel size is less common.

On the Pump Pro 16, the front V brakes only have a small clearance with the stock tires, although there is still a big clearance with the fork.

About 15 mm of clearance between the tire and the rubber cover.

On the rear, there is very little clearance, at just a few millimeters.

I found that the brake arms of the Tektro brakes are about 96 mm long.

In this case, if I wish to use larger 349 wheels on this Pump Pro 16 bike frame, it is probably possible. Based on the front fork clearance, there is plenty of space up front.

Still lots of space at the rear chain stay area as well.

It seems that the frame itself is not the limiting factor for larger wheels. Rather, it is limited by the clearance between the V brakes and the tires. 

This can be solved easily by using V brakes with longer arms, such as the Shimano LX V brakes that were used on the Crius AEV20 folding bike. Those had an arm length of 107 mm which is longer, but it might still not be enough. If a larger rim diameter is used, the tire needs to be reduced in height as well, by using a slimmer slick tire that is not as tall.

Alternatively, a Litepro V brake with a long slot for brake pad adjustment might be needed, if the rim position is changed a lot. This was used on the Fnhon Gust.

No real reason to change from the existing 305 wheels to larger 349 wheels, as it works perfectly fine now. Just wanted to document these ideas for future reference.