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.
A 50mm tire on a 305 rim results in the same wheel diameter as a 28mm tire on a 349 rim. But the ride will be much cushier on the 305 wheel because it will be running lower pressure. There is no shortage of tire choice in 305. It is certainly no worse. overall than 349. 305 is more common than you imagine.
ReplyDeleteAnother thing. You keep repeating that the Gust is made for 349. That's a partial perspective as the original Gust came with vbrake mounts and originally before the hype bandwagon most people built it with 305.
ReplyDeleteDo you know if you can run 349 tubes on 305 wheels? For 349 there are some very light Tubolito tubes available.
ReplyDeleteNope the size difference is too big to fit.
ReplyDelete