SDG I-Beam Duster and Micro Carbon Seatpost

December 4, 2013

Mounting system ditches rails, adds durability

Speed Defies Gravity
I-Beam Duster & Micro Carbon seatpost
£80/$100 saddle, £90/$120 seatpost
by Marc B for 7 Months

Mounting system ditches rails, adds durability

I-Beam:  Lighter, cheaper, stronger
I-Beam: Lighter, cheaper, stronger

Given the number of changes to bicycles and bicycling since their introduction over a century ago, the parallel round metal mounting rails at on the underside of most saddles have served us remarkably well.  But given railed saddles’ manufacturing complexity, potential for creaking, and inefficient structure, the gravity-oriented saddle makers at Speed Defies Gravity (SDG) feel that it’s time to move saddle interface tech forward.  Enter the I-Beam.

In order to sidestep the issues raised by bent, popped, and broken saddle rails, five years ago SDG’s lead designer decided to try something different.  Molded directly into the saddle shell, the company’s I-Beam design is both stronger and less expensive to manufacture than than metal or carbon rails at any given weight.  The centre mounting rail provides plenty of fore-aft adjustment in a compact package, staying clear of the rider’s thighs while still allowing for a suspended shell and various amounts of engineered flex.

Subtle unidirectional carbon
Subtle unidirectional carbon

At 226g (31.6x400mm actual), the SDG Micro Carbon seatpost isn’t the sort of thing to draw a lot of trailhead fondling.  A matte unidirectional carbon, the only real distinguishing feature is its I-Beam specific head.  For angle adjustment, the zero-offset model uses a pair of curved wedges that aren’t dissimilar in concept to those used by Crank Brothers’ or Ritchey.  The single 5mm bolt serves to hold everything together but doesn’t bear the brunt of impact forces.  In use, the post has been solid and creak-free.  Only 25g lighter than a comparable Thomson Elite post, the Micro Carbon seems built more for longevity than ultimate light weight- no surprise given the brand’s gravity origins.

Without the flex of some wispier posts, a large-diameter Micro Carbon won’t add much in the way of suspension- but larger riders will no doubt find its solidity comforting in its own right.  Because no torque specification is provided for the single fastener, we were a bit conservative to start, endeding up with a slightly wiggly saddle.  Assured by SDG that tighter is better (within reason), we cranked the fastener up to th 15Nm range and neither the saddle nor head has moved in over six months.

Just to clarify, there is an "S"  hiding just 'round the corner
Just to clarify: there is an “S” hiding just ’round the corner

Where the I-Beam system really bears fruit is in the saddle.  The 220g (actual) I-Beam Duster saddle is both lighter and stronger than its Ti-railed equivalent.  An XC-oriented saddle, the Duster makes use of lightweight foam, a suspended centre section, and intentionally flexy wings to provide comfort.  The subtle “Peri-Canal” keeps blood flowing where it’s most appreciated and the brightly-coloured microfibre cover (six combinations are available) has held up very well.  The flat-ish profile is designed for riders who tend to move about in the saddle.  Despite the lack of rails, saddlebaggers are accommodated by a removable (10g) Topeak QuickClick attachment point.  Not quite all day comfortable when paired with this rider’s bony behind, the Duster is – in keeping with its XC/’cross race aspirations – plenty comfortable for 2-3 hour efforts.

While adoption has been slow, SDG’s I-Beam has proved itself solid and quiet.  Even so, both Kind Shock (KS) and Gravity Dropper are supporting the I-Beam standard on their dropper posts, a welcome development.  Not cheap per se, the I-beam Duster and Micro Carbon are more solid than their weight would imply and priced reasonably for their  durability.  Those whose size or riding style is hard on saddles or anyone whose thighs rub on traditional saddle clamps would do well to give the system a look.


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