The Dahon MuSP is a really nice drop bar folding bike that I assembled back in 2018. It's a rarely used bike, but it is always available as an option if you need to transport a folded drop bar bike to another location.
As shown below, when folded, it can be placed on the backseat of a car, or in the boot if the boot is large enough. On this Dahon MuSP, I chose an inward folding handlepost for a more compact folded size. Most of the time, it works, but it can also be rather awkward during folding.
The problem with the inward folding handlepost with a drop bar is the difficulty of actually folding the handlepost and drop bar, without the saddle or other parts of the bike getting in the way.
Another issue is that the shifters protrude from the folded bike quite significantly. For storage it is fine, but it barely fits in the backseat of the car, as the shifters are already touching the windows.
Folded Dahon MuSP on the backseat of a car. Shifters are right up against the window.
After much consideration, I decided to try a more conventional outward folding handlepost for this drop bar folding bike. Although the folded size would be wider, at least it would be shorter and perhaps easier to place into the car.
New outward folding T-shaped handlepost on the right, just a tiny little bit taller. Shorter ones are practically impossible to find.
The only difference is the direction of the joint, which determines whether it folds inwards or outwards.
Uses a simpler sliding safety lock instead of a rotating catch. Non-branded.
New outward folding handlepost is a little heavier at 503 grams.
New height is about 297 mm from the base.
For reference, the previous inward folding handlepost is a bit lighter at 494 grams.
It is a bit lighter because it is slightly shorter at 295 mm.
New outward folding handlepost installed on the Dahon MuSP!
The locking lever indicates the direction which the handlepost will fold down.
The handlepost swap is a straightforward and easy modification, as I have done it so many times on so many folding bikes.
Next, I also wanted to service some of the parts on the Dahon MuSP. One of the other problem that I faced was the wear and tear on the rear brake outer casing during folding.
Due to the internal cable routing, the rear brake outer casing will slide in and out of the frame during folding. As the hole on the frame has sharp edges, repeated folding will damage the outer casing, even when I fold and unfold the bike carefully. I have tried adding some plastic guides but they are not effective.
Damage to the rear brake outer casing at the frame hole area. Cuts and scratches on the outer plastic layer.
Prior to assembling this Dahon MuSP, I did not know that internal cable routing would be a problem for a folding bike. Although internal cable routing looks clean and nice, it is not so suitable for folding bikes. The United Trifold does a better job of internal routing, but it still has some limitations.
My solution is to change the cable routing to an external type, even though the frame is not designed for external routing. There are no external cable guides, so I have to create some.
Upon removal of the rear brake outer casing, I found that some places have cracked completely, exposing the coiled structure inside.
Stick-on cable guides to save the day! Basically stick the backing onto the frame and use the C-clip to hold the outer casing or hose in place.
Initial placement of the stick-on cable guides, under the frame for better appearance. Same location as traditional external cable guides.
Near the seat tube, the cable guide will route the rear brake outer casing smoothly towards the Ultegra rear brake caliper.
Previously, the Di2 Junction B was placed inside the frame. With external cable routing, Junction B has to be placed on the outside, similar to how it is done on the Fnhon DB12.
The cables used to run internally through the frame joint, but they have since been moved to the outside.
This was the internal metal cable guide that protected the outer casing and Di2 wire across the frame joint during folding. It comes with the Dahon MuSP, but it is no longer necessary.
Here is how it looks, with an outward folding handlepost and external cable routing. Although the folded size is wide, it is also shorter than the previous setup.
When folded down, the end of the drop bar will stop against the front tire. If the handlepost is shorter, the drop bar will be able to clear the tire for an even more compact fold.
The modification has been completed, but a few days later, I noticed that the stick-on cable guide has been detached from the frame. The cable guides are pasted onto the frame with double sided tape, unfortunately it is not strong enough.
When folded for storage, this bend puts a lot of stress on the stick-on cable guides. In this position, the outer casing will detach the cable guide located underneath the frame after a few days.
First I tried using better 3M double sided mounting tape, but it was still not strong enough. The tape remains on the frame and on the cable guide, but the sticky part shears off due to the load from the bent outer casing. I considered using super glue or epoxy, but worried that the paint may come off instead.
Finally, after many different trials, I shifted the stick-on cable guides to the side of the frame, to better withstand the forces exerted by the outer casing. Also, a cable tie has been added to the stick-on cable guide to strengthen the connection and prevent the mounting tape from shearing off.
Front cable guide shifted from underneath the frame to the side to withstand the forces from the bent outer casing.
Middle cable guide undergoes the highest force, and needs to be reinforced with a cable tie to prevent it from coming off the frame. Rear cable guide is fine.
Final stick-on cable guide setup, which is still going strong after a few months.
External cable routing can be seen around the main frame. Not as aesthetically pleasing as internal cable routing, but more practical.
Looking good! The bike has a 1x11 speed Ultegra Di2 setup.
Latest bike specifications, with a 46T front chain ring and 11-32T cassette, for a 32 - 92 gear inches gearing.
Weight of this folding bike is about 9.7 kg inclusive of pedals and kickstand. Not really lightweight, as the frameset, wheelset and saddle are rather heavy.
On the other hand, if you start with a lightweight mini velo frameset such as the Java Freccia, the end result would be 3 kg lighter!