This is probably the last upgrade post for this Bestrider Pump Pro 16 that I will be writing in a while. Starting from the stock bike, the drivetrain was upgraded from single speed to a 3 speed internal hub system. The tires were changed to slick type for lower rolling resistance, while the saddle and seat post were also changed to allow saddle position adjustment.
Now, I will be changing the stem, to improve the handling of this bike. I placed a GoPro on the stem cap of the bike, to record some riding videos from my kid's point of view. It is very interesting, and I found that the handlebar swerves left and right quite a bit even when riding in a straight line.
As I am unable to ride the bike myself to check the geometry, I suspect that this could be due to sensitive steering. It could be due to insufficient trail on the fork or some other geometry problem. Instead of being able to self-center when riding the bike in a straight like, the steering might be too sensitive, requiring constant input and correction to prevent it from steering towards the left or right side. I encountered this issue when I used a handlepost that was too short on the United Trifold.
The stock stem is super short, which may contribute to the sensitive steering condition. I decided to swap the stem to a longer one to see if it improves the situation. As the reach is not too far for my kid, this change of stem length should be OK.
Stock stem length is 35 mm
I have a few spare stems of various lengths, and I found one that may be suitable. This is a 60 mm FSA stem that I used on my Avanti Inc 3 bike 5 years ago.
Going to try this 60 mm FSA stem on the Bestrider Pump Pro 16 kids bike.
Side by side comparison of the stems. The stock 35 mm stem is a lot chunkier with excess material everywhere.
Stock 35 mm stem weighs 121 grams, which is considered heavy as it is a very short stem.
60 mm FSA stem weighs less at 115 grams.
Unfortunately it is not a straightforward stem swap, as the handlebar clamp area is of a different diameter. The stock 35 mm stem has a handlebar clamp of diameter 25.4 mm, which is why I got a 25.4 mm carbon handlebar during the earlier upgrade.
However, the FSA 60 mm stem has a larger and more common 31.8 mm clamp diameter, which is normally used with modern wider MTB handlebars and road drop bars.
I had a few options here. I could get a new 60 mm stem with 25.4 mm clamp diameter, but this is probably hard to find. An alternative is to find a new 31.8 mm handlebar, but I didn't want to do that as this handlebar is very new.
So, I chose the easy way out which is to use a handlebar spacer to enable the 25.4 mm handlebar to fit into the 31.8 mm stem clamp. This spacer will go around the handlebar, boosting its diameter to match the larger stem.
Handlebar spacer with an internal diameter of 25.4 mm and external diameter of 31.8 mm.
Weight of 32 grams for this spacer, which unfortunately means added weight.
Finally, I did a weight comparison before and after the stem change. Due to the stem height, there was a change of the stem spacers used as well.
Stock setup is 141 grams with the short 35 mm stem and aluminium stem spacers.
New setup is slightly heavier at 156 grams, inclusive of the handlebar spacer. The use of carbon stem spacers does help to minimize the weight increase.
New 60 mm FSA stem installed with the handlebar spacer, and also with carbon stem spacers used this time. Check out the PRO GoPro mount which is the stem cap.
Out for a ride at Marina Bay Sands!
Together with the United Trifold folding bike.
Lovely view of the skyline and also the bikes.
Beside the Merlion
With this slightly longer stem, I noticed that the handlebar wobbling is greatly reduced. This longer stem is helping to stabilize the steering geometry and making it less sensitive. Not only that, it gives a more sporty feel as the reach is slightly increased. Both myself and my kid are very happy with this bike!
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