Brooks' so-called "clip" for mounting their saddles to an old-fashioned plain seat post (called "kerze" by the Germans, aptly for candle...) is cheap pressed metal, rubbish that sooner or later will give trouble. This is bad enough with single rail saddles, but at least those generally fit modern micro-adjustable seat post heads. For single rail Brooks saddles Brompton makes its own good-looking clamp for plain seat posts, called the Pentaclip, but they have nothing for twin rail saddles, which is a huge pity as the majority of really comfortable Brooks saddles, for commuting and utility bikes, and for tourers who sit more upright than the ex-roadie drop handlebar brigade, are twin-rail saddles or even triple rail saddles. Brooks knows it is problem, but for decades have done nothing about it except to make one particularly well-selling saddle, the B66 twin rail series, available in a single rail equivalent to fit micro adjustable seat posts, relabeling it the B67 -- it is deservedly popular.
My own fave, well-broken in saddle is the triple coil-spring B73, which has twin rails per side. This article describes how, when the wretched Brooks clip would no longer hold the setting after five years, I replaced it by a proper seat post with a decent range of adjustment, in a design which, once set, holds the adjustment.
The method is the same for any bike, though on my Utopia Kranich there was the additional problem that these days almost no one makes a 26.4mm diameter seat post, so in the end I was left with a single in-stock choice, the inexpensive Brand X from CRC, €15.49 delivered. What I really wanted was a Nitto lugged seat post, like Julian's, but that has too much layback. I would also have taken an Airwings suspended seat post but the philosophy behind the design of my bike is not for long exposed seat posts, and I couldn't find the 110mm headroom required by the best Airwings post; in future I may remove the springs under my B73 to find the headroom to fit an Airwings, just to see if the combo of Brooks bare hide and Airwings springing works together. Or I would have taken a Thomson, which is well reputed, but I couldn't find one in 26.4mm dia in stock from my usual bike components pushers, and this has been dragging on for seven months with the summer coming (have faith, my brothers, it
is coming).
For the moment, we're working with the Brand X seat post, which is nicer than the price might lead one to believe, all black except the fasteners and washers, quite different from the photo on the CRC site. The sequence described will most likely also work for your fave seatpost and any multi-rail Brooks saddle.
Next, after a seat post of suitable diameter and layback, you need a pair of spacers to insert between the rails so that a micro-adjustable head designed for a single rail doesn't crush the rails together and upset the attitude and perhaps the resilience of the rails/frame. The machined aluminum design by Joe Breezer is generally available in America, and all these spacers are called "sandwiches" because the Breezer design looks vaguely like a sandwich, and fits between two similar parts. It can be tiresome and expensive in postage to get one of the Breezer items. It isn't clear to me whether the Breezer item will work with twin-screw heads, or only with the older single-screw ones; if not, you might have to drill or file the Breezer adaptor to make it usable.
You will also require a longer bolt or pair of bolts for the adjustment head, depending on its design, and these must be capable of withstanding high tension. The Breezer sandwich comes with one longer replacement bolt suitable for a single-bolt twin rail installation.
I was therefore most pleased when Julian (who posts here as Julk) made me a gift of a fibre-filled nylon sandwich and a 45mm long high tensile bolt. Thanks, Julian! The bolts in the Brand X seat post are common M6 items but if you buy a fancy Japanese post, they use M7, which can be tricky and expensive to get.
The Brand X design adjustment head has two dissimilar length adjustment bolts, so I discarded the shorter one and used the longer one that came with the seat post, and Julian's long bolt. Between them they had just enough length to allow a very conservative setting. To get the nose down further for a truly level saddle, I'll need at least one 50mm bolt, and one with a minimum length of 43mm, for which 45mm is the nearest off-the-shelf size. I'll order those when I've taken a test ride. I checked with the green-framed mirror that there is enough engaged thread on each bolt, as I don't fancy being assaulted by a seat post.
The thin cross-struts on the sandwich bent when I forced it into the narrow Brooks rail set, but they are not structural (their purpose is to hold the actual sandwich filling level in position while the components of the micro-adjuster are assembled -- otherwise you'd need five hands...) and the bending is serendipitous because it clears the path of the two bolts.
The finished assembly looks so much better than the pressed sheet metal of the wretched Brooks "clip"! (No, my B73 isn't that hollow! It'a trick of lighting and angle.)
EDITED 0133 13 April 2014 to clarify adjustment bolt diameters
