Hi we're Pam and Gilbert of 2 Bikes 4 Adventure.
In a previous video, we discussed Brompton gearing options. In this video, we'll discuss the various
Brompton seat post and handlebar options and how to combine them for riding comfort and performance.
Selecting the size of a traditional road bike used to be as simple as measuring the standover clearance.
A two to five centimeter clearance (one or two inches) between the rider's crotch and the
top tube meant a proper bike fit. A variation on this method is to measure the rider's inseam,
then using a formula or lookup table provided by the bike manufacturer, select the corresponding
frame size, but bike fitting involves more than a single measurement to decide on a small medium or
large frame. A typical diamond shaped bike frame has three attributes that define its geometry,
the three sides of a triangle: bottom bracket to saddle, top tube, bottom bracket to stem.
In contrast, the Brompton frame is only available in one size and has a distinctly different shape
so we have to use a virtual triangle to determine these measurements and learned
which seat post and handlebar configuration is closest to ideal for an individual rider.
The criteria will be: seat post length, handlebar selection and saddle to bar drop. Brompton offers
three choices of seat posts. The regular seat post can be adjusted for riders with inseam between
66 and 83 centimeters (26 and 33 inches), it is also the lightest of the three options.
The extended seat post accommodates riders with inseam up to 89 centimeters (35 inches). Note that the
extra length also increases the saddle height when the bike is folded which could be an issue when
packing your Brompton for air travel. Finally the telescopic seat post is the most versatile option.
The dual tube arrangement offers some advantages over the piece tubes in addition to accommodating
the tallest riders up to 99 centimeters (or 39 inches) inseam. The detachable top tube
assembly enables you to remove the saddle without using tools, this feature is useful if you need to
quickly store your bike in a confined space such as an aircraft overhead bin or an x-ray scanner
or pull a Jedi mind trick on a security agent "This is not the bike you were looking for" .
The outer telescopic post has a diameter of 31.8 millimeters, just like the other Brompton seat
posts but because the inner post is narrower, it may accommodate third-party accessories that might
not otherwise fit for example attachments for rear flashers or bike packing gear.
That versatility has a price, it's more expensive
and heavier. When we travel we take the regular seat post and the 300 gram weight saving.
Seat post adjustment on the Brompton is pretty much the same as any other bicycle,
because of its folding capability however it has to be done a lot more often.
You may make a mark on your seatpost or purchase the optional Brompton saddle height insert
to ensure the right fit quickly every time you unfold your bike.
If the fully extended seat post is a little too short, you can rotate your Pentaclip upside down
and reattach the saddle to the higher rail position, this will provide an additional 2.5
centimeters (1 inch). The seat will of course be higher by that same 2.5 centimeters when the bike is folded.
The choice of handlebar will determine the overall rider position whether upright or stretch forward
which significantly affects the rider's comfort and performance. We will want to know the stack
and reach measured from the bottom bracket to the middle of the handlebar. A short stack and
longer reach provide a relatively aggressive stance suitable for speed and performance.
A long distance road bike model may have a variety of stack reach combinations based on frame size.
A higher stack and shorter reach will be more appropriate for casual upright riding
such as on a city rental bike. Brompton doesn't provide a telescopic handlebar adjustment unlike
the Birdy for example, so we're limited to three handlebar options to adjust the reach and stack.
The S sport type is a straight handlebar offering the most aggressive lowest riding position, it is
the preferred choice for short and fast trips but it may not work properly with every model
of front bag. The M modal type, the most popular, offers a mid-upright position. For average-sized
riders, it offers a relatively neutral position usually favored by tourers for longer distances.
The H high model offers the most upright riding position
particularly tall riders or riders used to dutch style bikes may prefer this option.
While a slight reach adjustment is possible for the M and H-types, it's limited by
cable length and may compromise the folding capabilities if moved more than one centimeter.
As a general rule, a rider would want the handlebar to be higher than the saddle for a more upright
and comfortable position and lower than the saddle for more aggressive and performance
oriented use. Here we have some examples of the sitting position of the S bar configuration
representing the expected height of the handlebar above or below the saddle seat
in relation to the rider's inseam. For example, a short rider with a 72 centimeter inseam riding
an S-type Brompton should expect the handlebar to be approximately four centimeters above the saddle,
a slightly upright position that should be satisfactory for touring.
A slightly taller rider with an 80 centimeter inseam on the same S-type bicycle, after adjusting
the seat to the proper height, would find the handlebar four centimeters below the saddle,
which we'll call minus four, a more aggressive position that could become uncomfortable over
long distances, especially for the wrists. This configuration would likely be more
appropriate for a one or two gear lightweight Brompton where speed is the primary goal.
Changing to an M type would raise the handlebar approximately five centimeters above the saddle,
which we'll call plus five, a comfortable mid upright position
and H type would raise it by a further six centimeters four plus eleven.
If your local bike shop doesn't have Brompton demonstrators or if you intend to order online you
may use this graphic as a quick reference guide. Measure your inseam, let's say 84 centimeters
and the saddle to handlebar distance of any other bike that you find comfortable,
in this example, five centimeters below, minus five, locate on the graph the intersection of
these coordinates and see which Brompton handlebar type provides the most similar writing position.
In this example the S type is the closest. On the other hand, if you're comfortable on
a bike with a higher handlebar, a plus 10, the intersection is closest to the H-type.
Aftermarket companies offer additional handlebar alternatives, but retrofitting
an existing handlebar configuration may require replacing the cables and stem,
meaning more time, trouble and cost, so aim to figure out the best choice at purchase time
based on the rider's height, preferred riding position and intended use. Seat post selection
is less critical as it is easy to replace or upgrade to a titanium post at a later date. We hope
this information helps you find the optimal bike configuration for your touring comfort.