Bestrider Pump Pro 20: Wheelset

One of the stock components from the Bestrider Pump Pro 20 that I considered changing was the 20 inch 406 wheelset. However, I did not order a new wheelset yet, as I wanted to see what the stock wheelset looks like. If it is good enough, I will not need to get a new wheelset.

After disassembling the bike earlier, I also removed the stock Kenda tires from the wheelset, to find out the weight of the stock wheelset.

Stock front wheel is 527 grams

Stock rear wheelset is 802 grams

The stock wheelset weight is thus 1329 grams, inclusive of rim tape. Not very lightweight, but can't complain given that it is a stock wheelset.

In comparison, the Ascent Cirrus Elite carbon wheelset is 1217 grams, while the Kinetix Pro wheelset is just 998 grams.

Rim external width is 24 mm

Rim internal width is nearly 20 mm, which is pretty good, as it is even wider than the carbon Cirrus Elite wheelset (18 mm).

Rim height is just 21 mm, which is very shallow. This helps to lower weight which is good if you are not concerned about rim aerodynamics.

Based on what I have seen so far, the weight of the wheelset is acceptable. Rim width is surprisingly wide, which helps to ensure a good tire width.

There was an issue when I fixed the front wheel onto the front fork, as the rim seems to be offset to one side. I didn't notice this earlier when the bike was fully assembled with tires.

Rim is very obviously offset to one side when installed in the front fork.

Upon closer inspection, I spotted a gap between the hub end cap and the hub shell. This does not look normal.

Whereas on the other side of the hub, the hub end cap is sunken inside the hub shell.

Based on this, it seems that the hub shell and thus the rim is not properly centered on the hub axle. Let's see if it can be fixed...

Close up look. Sealed bearing is not seated properly into the hub shell, causing it to protrude and also affect the position of the hub end cap.

On this side, the sealed bearing is seated too deep into the hub shell, causing the end cap to be sunken inwards.

After checking with the bike seller from Taobao, they said that this might be caused by the hub axle being pushed to one side during shipment. Not sure how plausible it is, but they did suggest that I could push the hub axle, to center the wheel.

No harm trying, since I got nothing to lose anyway. What I needed to do was just to find a spacer to support one side, and slowly knock on the other end.

This side needs to be pushed in

This side has to be moved outwards, which can be done by pushing on the other side.

When done properly, this is how it looks like. The sealed bearing position on both sides should look like this, so that the hub end cap positions are equal on both sides.

After reworking the front hub, the hub end cap matches properly with the hub shell on both sides as shown.

Glad that I could fix the offset front wheel myself, with a bit of DIY work. Bike seller was helpful as well, although it would be good if I did not have to fix it myself.

For the rear wheel, it comes with a freehub that supports multi speed cassettes. Since it came with a 8 speed cassette, this means that it will definitely fit a 9 speed or 10 speed cassette. 11 speed road cassettes will require longer 11 speed freehub bodies instead.

After comparing the stock rear freehub with a 11 speed freehub body, I found that they are the same length.

In other words, the stock rear wheel can support 11 speed road cassettes. If installing 8/9/10 speed cassettes, a 1.85 mm spacer is needed.

I will be using these lightweight titanium quick release levers that only weighs 51 grams per pair.

The stock wheelset is pretty OK, although it is not very lightweight. Still, it is very acceptable given that it is part of the cost of the full bike. Also, since this is for a kids bike, it doesn't have to withstand a high load or have the most efficient hubs.

Bestrider Pump Pro 20: Frameset, Handlebar, Seatpost, Saddle

It's time to disassemble the Bestrider Pump Pro 20, before starting the modifications! As there are some  stock components that are pretty good, I will be reusing them. As for the other parts which do not meet my requirements, I will swap them out for something better.

Bike frameset with most of the components removed!

Only the aluminium frame left!

Frame weight is 1370 grams, with one headset bearing. It was stuck and I could not remove both to weigh.

Using sealed headset bearings, which is much nicer than loose ball bearings.

Aluminium front fork, with the super tall crown and large width.

Front fork is 507 grams, which is pretty heavy. It can be lighter as proven by the Fnhon front fork.

Stock super short stem weighs 85 grams.

Stock stem length is just 35 mm, which is like a MTB stem.

Lightweight carbon headset spacers weigh 8 grams.

Freshly cleaned and ready for new components to be installed!

As mentioned in the earlier post, the stock riser handlebar is too wide and too high. Therefore, I will be changing to a straight handlebar that is also narrower.

On the previous Bestrider Pump Pro 16, I got a new carbon handlebar in the preferred width, so that I don't need to cut it myself. However, for this new handlebar, I could not find a stock handlebar that comes in the preferred width, so I need to cut it to the correct length myself.

New carbon handlebar with a width of 580 mm

After cutting to the preferred width of 520 mm, the weight of the carbon handlebar is 131 grams. 

I used a very general formula to calculate the ideal handlebar width. Based on this guide, the handlebar width should be about 0.44 of the rider's height. This gives a handlebar width of 520 mm. The weight is pretty OK but there are lighter ones available. The one I used on the Birdy is just 107 grams for 580 mm width. Not sure why this one is significantly heavier, probably because I got a cheaper one.

As mentioned in the first post, the stock seat post and saddle is pretty bad, which is why I have to change them. The saddle and seat post which I got for the Bestrider Pump Pro 16 was good, which is why I decided to get another set for this bike.

Stock carbon seat post of 350 mm length before cutting. Diameter is 27.2 mm.

As the seat post length is too long to insert into the bike frame, I had to cut 60 mm to ensure it can fit at the lowest saddle position. Weight is 203 grams after cutting.

One more SDG Fly Junior saddle for the new bike!

Blue colour was chosen to match the new bike frame

Weight of 260 grams, which is pretty heavy considering the smaller kids size.

The weight of the original saddle + suspension seat post is 185 + 408 = 593 grams. Changing to the new SDG saddle and carbon seat post is 259 + 203 = 462 grams, a savings of about 130 grams.

There are other new components for the Bestrider Pump Pro 20 kids bike, they will be introduced in the next few posts.

Bestrider Pump Pro 20: Stock Geometry and Dimensions

With the Bestrider Pump Pro 20 kids bike in hand, I am now able to study the stock components and also the original bike geometry and dimensions.

I did the same geometry study for the Bestrider Pump Pro 16, although it was not as detailed as this one.

Wheelbase is about 841 mm, which is longer than 700 mm on the 16 inch version.

Rear chain stay length is 330 mm, longer than 273 mm on the 16 inch version.

Standover height is about 520 mm, compared to 450 mm on the 16 inch version. Make sure your kid's inseam is longer than this number.

Handlebar width is 610 mm, which is even wider than the 560 mm of the 16 inch version.

Handlebar height from the ground is 810 mm, which is too high for a kids bike.

Although the rest of the bike is designed for kids, somehow the handlebar width and height is not. It is way too wide and high for kids. It is one of the few design problems with the Bestrider Pump Pro series, but it is not a big issue since this can be changed rather easily.

Stock tire diameter is 500 mm, which is pretty standard for 20 inch 406 tires.

Tire width is 44 mm, which is good for comfort and off-road riding. However, will be changing to narrower, slicker tires for pavement and PCN riding.

Huge amount of tire clearance at the front fork. Not sure why the distance between the tire and the fork crown is so big. Same design as the 16 inch version.

Still lots of tire clearance at the rear as well, even with these rather big tires.

Crank arm length is 127 mm, which should be a good fit for this 20 inch kids bike. On the 16 inch version, the crank arm length was 102 mm.

Verified with actual measurement.

Narrow wide chain ring has 32T, which seems kind of small, even for kids bikes.

Rear frame OLD is 135 mm, which is a typical width for disc brake rear wheels, although this is not a disc brake rear wheel.

Front fork OLD is 100 mm, which is also a standard width.

Weight of Bestrider Pump Pro 20, excluding kickstand is 7.6 kg. This is a very good weight!

If we add the weight of the lightweight kickstand, the total weight would still be slightly less than the claimed weight of 7.8 kg.

This has to be one of the lightest multi-speed 20 inch kids bikes that I have seen. Most other kids bikes weigh a lot more, even with a simple single speed setup! Bike weight is very important for kids bikes, as they will need to handle a bike that is a large percentage of their own body weight.

Stock setup has lots of spacers on both sides of the bottom bracket adapters.

Bottom bracket frame width is a standard 68 mm, English threaded. Will be easy to swap in another standard bottom bracket.

Most of the frame geometry and component dimensions seem to be well sized for 20 inch kids bikes. With the exception of the handlebar that is too wide and too high, all other areas seem to be well designed.