In the previous post, I have compared the folded size of the United Trifold with the Brompton, and found that the United Trifold does not fold as compactly or neatly. For this post, I will compare another aspect, which is how the bike looks when it is in parking mode. By parking mode I mean that the rear triangle is folded down, so that the bike can stand on its own without a kickstand.
In the parking mode, the United Trifold's front wheel is way up in the air, as compared to the Brompton which has the front wheel resting on the ground. This is one sure way of telling the bikes apart even from far far away.
United Trifold has the top tube resting on the rear tire, while the Brompton still has a big gap.
As a result, the front wheel of the United Trifold is unable to touch the ground.
Big difference in front wheel position when in parking mode.
With the front wheel on the ground, the Brompton is more stable in the parking mode. Note the huge gap between the top tube and the rear tire.
With the front wheel off the ground, the United Trifold can be pushed around even in parking mode.
Why is there such a big difference in the folding geometry, even though the folding concept is the same? This has to do with the different frame dimensions and designs. Let's take a closer look and find the root cause that accounts for this difference.
Upon side by side comparison, I found that the main reason is the position of the rear axle. When the rear triangle is folded down in parking mode or folded mode, the rear axle of the United Trifold is much further off the ground than on the Brompton. This causes the rear wheel to be positioned higher up, which in turn pushes the top tube higher up as well.
With the top tube being pushed upwards, the highest point of the folded bike becomes the handlepost joint. This tilt also causes the saddle to stick out at the rear.
On the Brompton, distance from rear axle to ground is 23.5 cm.
On the United Trifold, this distance is much greater, at 28 cm which is a 4.5 cm difference.
The measuring tape shows the position of the Brompton rear axle, as compared to the United Trifold rear axle.
Rear tire of Brompton is only about 3 cm off the ground, while the United Trifold would be 4.5 cm higher, at 7.5 cm off the ground.
The rear wheel of the United Trifold is positioned much higher compared to the Brompton, which leads to the difference in parking mode and folded size.
On the Brompton, the rear pivot is located almost on the same horizontal axis as the bottom bracket centre.
On the United Trifold, the rear pivot is located quite a lot lower than the bottom bracket centre.
Due to the different rear pivot and rear wheel position, the result is a higher rear wheel and higher top tube position.
On the Brompton, the top tube stretches all the way to the front, to lower the head tube as much as possible, while the United Trifold top tube stops quite far back. See the position difference of the frame joint!
The Brompton is thus able to lower the head tube and handlepost joint, making it shorter when folded.
Note the big difference in rear wheel position when folded, with the United Trifold rear wheel positioned much higher up.
Back to the parking position. Looks quite similar from this angle, although the front wheel position is totally different.
United Trifold top tube is already resting on the tire, while there is still a big gap on the Brompton.
In summary, the United Trifold's folding design is not optimized, preventing the folded package from being smaller. If they are able to lower the rear wheel position, it will allow the top tube to rest at a lower position, making the whole folded bike smaller in size.
Great series of posts! Thanks.
ReplyDeleteThe problem with the United's folded height is the rack. Remove it and it sits a lot lower like the Brompton
ReplyDeleteOnce the rack is removed, it will fall on its side when folded, and cannot be rolled around.
DeleteYes, so I added a wheel extender (Muzqi) so it folds level like a Brompton and it's stable enough to roll around without falling over. I also changed to an 80mm wheel to give a smoother roll and giving the suspension block more ground clearance.
Delete