Author Topic: Mounting a Brooks twin rail saddle on a modern micro-adjustable seat post  (Read 14873 times)

Andre Jute

  • Hero Member
  • *****
  • Posts: 4128
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
« Last Edit: April 13, 2014, 01:33:56 AM by Andre Jute »

Danneaux

  • Administrator
  • Hero Member
  • *****
  • Posts: 8281
  • reisen statt rasen
Oh, there's real beauty in that final assembly Andre, and in your essay, which should prove helpful to others who wish to run multi-railed saddles on proper seatposts/clamps.

I'm so glad this has resolved your dilemma and it really looks the business as well. If needed, holes can be readily re-tapped and 8mm bolts substituted for 7mm if needed. I did a similar modification for a friend with great success, though the pathways had to be enlarged slightly as well. You may be interested in this discussion of the Airwings vs Thudbuster designs, Andre: http://forums.mtbr.com/general-discussion/suspension-seatposts-thudbuster-vs-extra-bike-ii-329544.html There's good and bad features to each. If you(r knees) are at all sensitive to changes in saddle height, a parallelogram seatpost might be preferable to a telescopic if you have the vertical space for it. You don't have room for a Thudbuster LT, but it is possible removing your springs could do the job if you wish to go with a TB instead of them. Necessary to clear an Airwings as well, as you've mentioned.

Joe Breeze ( http://en.wikipedia.org/wiki/Joe_Breeze ) and others who did "Repack Runs" on Mt Tamalpais in California's Marin County are responsible for much of what we think of as mountain bikes, and their work formed the bedrock for modern 26in-wheeled Adventure-touring bikes like...Thorns. I count myself lucky to have seen Breezer #1 in person.

All the best,

Dan.

julk

  • Hero Member
  • *****
  • Posts: 976
Andre,
Great looking assembly, hope it is riding well.

For that perfect level saddle, you can get a very smart titanium 50mm long taper head M7 bolt from here
only $11 delivered…
Julian.

Andre Jute

  • Hero Member
  • *****
  • Posts: 4128
Thanks, Dan. For the moment I've given up the idea of an additional suspended seat post, The Thudbuster LT won't fit, that's for sure; the LT or the Airwings might be levered in with radical surgery to my Brooks B73. But careful inspection of the B73 springs under pressure showed that they move probably as much as a Thudbuster ST, though perhaps not in as controlled, progressive a manner, and I'm not keen at all on either disassembling the Brooks, in which I have thousands of miles invested, or starting again with a hard leather saddle of flatter profile like the Spa. In fact, it might be smarter to buy a B67 pre-softened and removing the springs if I go back to the hide/rails/Thudbuster idea. In would be worth a hundred euro to me to preserve my B73 as an instant fallback. With the uncertain weather here, a day's cycling lost really matters, and I'm fed up getting my exercise on the treadmill (I've worn out the Nordic strider, which turned out to have plain bearings running on mild steel -- cheap Chinese cr@p sold expensively by JD Williams and Co LTD, M60 6ES, photographs on request).

Thanks for the link, Julian. I'll get onto them as, while I currently have full engagement of all threads, just, but only to the bottom of locating dimples on rotating nuts invisible from the side of the saddle, I like having the business ends of such crucial bolts stand proud for a quick visual check. So I'll splash out for one of those ti bolts you recommend and move all the bolts up one place. For the moment I've been for a short sunshiny ride into a gale direct off the Urals and the setup, while not ideal, works. When I have the right fasteners, if I haven't become too attached to the much more upright seating position of the present seat fixing, I'll move the assembly further back at the same time as I tilt it more forward the tiniest fraction. That's the whole point of a micro adjustable seat post, to get it perfectly right, which is just about impossible with the Brooks clip, unless you strike it lucky, and then you usually lose the adjustment the next time you hoist the bike up on the work stand. Basically, after seven months of fruitless search for a choice of seat posts, I'm on my way, huge progress.

By the way, the resistance to the Brand X seat post in the first instance wasn't snobbery. I actually have quite a bit of Brand X stuff on my bike, the seat post clamp for instance, and the same thing duplicated as a steering tube clamp when I turned the Aheadset into a quill steerer to get height on my n'lock installation, and one of their toolkits that I advise to Rohloff owners because it has an 8mm socket suitable for switching gears on EXT box if you should break a cable, and quite a bit more. It's a brand I trust, and besides like because they don't emblazon their name on everything; I'm nobody's advertising billboard. But I was really looking for something special for a special bike (my original idea was a showpiece lugged Nitto seat post, like Julian has), and Brand X specializes in good quality functional gear at affordable prices.

Danneaux

  • Administrator
  • Hero Member
  • *****
  • Posts: 8281
  • reisen statt rasen
Quote
I currently have full engagement of all threads, just...
Andre, most threads are designed to achieve full strength when five threads are engaged, so you should be safe. However, like you, I prefer to have more engaged so I can quickly make a visual check and so I have a bit more margin in case of unexpected loosening.

All the best,

Dan.

Andre Jute

  • Hero Member
  • *****
  • Posts: 4128
When we meet, we won't need photographs, Dan. We'll be the guys wearing belt, braces and an old school tie tied around the waist just for good measure!

Danneaux

  • Administrator
  • Hero Member
  • *****
  • Posts: 8281
  • reisen statt rasen
Got that right, Andre! Solidarity!  :D

All the best,

Dan. (...who is very much looking forward to that meeting someday)