
Note: Hope 38.5mm QR clamp has to be ordered separately! (I won't take orders without it)
The #Seatposthugger Model S is a luggage carrier which is designed to hold the Brompton front carrier block and clamps onto your Brompton 31.8mm seatpost. The Model S is 36 mm shorter than the Model 4 series and 21 mm longer than the old Model XS with the advantage that the rack or bag can slide all the way up to behind the saddle which was't possible with the old Model XS.
Shown on the Green G line is a bolt-on prototype version, not yet available, but it shows that when your saddle is in the typical Brompton forward position there's room for the rack to be positioned behind the saddle. This is great for a bit more aerodynamics, having the bag behind your back. It's also a good choice for smaller riders who don't have a lot of seatpost exposed for a seatposthugger. Minimum distance from the end of the seattube/frame to the underside of the seatposthugger is about 15 cm to prevent heel strike. With the old Model XS, when used with smaller riders, the top of the bag could get in the way of the back of the saddle in this 15 cm position (see photo below). That's not a problem with the Model S.
Installing the Seatposthugger :
So in case you have a standard or extended (60 mm longer plain) seatpost you just remove the saddle and slide the Seatposthugger onto the post.
Note: In case you have a pre 2017 Brompton with telescopic seatpost the secondary clamp is secured to the seatpost with a small Allen bolt and special nut inside the plastic sleeve. Undo the bolt with a properly fitting Allen key but be careful to not lose it or lose the washer. The little special nut can be pressed out with the bolt or the allen key. In case you have a seatpost bung on the underside the nut will fall inside the post and ends up on the bung. Turn around the seatpost to free the nut. If the seatpost has an open end the nut will fall on the ground, so be very careful not to lose it.