Here is an opinion piece on the Transition 2010 Tri Bike. The excerpt below just deals with the seat post. You may want to read more on the
SlowTwitch.com website.
Thank you Specialized for allowing a rider to put his saddle where he wants it. [Digression] Here's a secret for all you bike designers out there: When you allow a rider input on his own position—when a fit session includes actually asking the rider whether he's comfortable and powerful—the rider, when given a legitimate, well-executed, choice in positions, will choose 79.5° of seat angle. This is the average. This is where the fat of the bell curve sits. [/Digression] So...
Here's a bike company that made a timed race bike to help in its quest for that elusive yellow jersey, nevertheless it thought enough about this bike's target market to allow customers the sit where they want. This, because the Transition Comp—and all the Transitions—come with one of three available seatposts.
The seatposts are named Team (way set back, without very much difference between it's two fore and aft positions); the Regular post; and the Straight post. These posts are each two-position posts, and, on the straight post, the center of the binder mechanism sits either 100mm behind the BB or 150mm behind the BB depending on whether the binder mechanism is in its fore or aft position.
The offsets are rational and thought-out. The swept back post (Regular post) has offsets of 160mm and 210mm. The Team post has offsets of 200mm and 225mm respectively.
Your safest bet is to get your Transition with a Straight post (you may well choose the rear position of the Straight post). But if you're a taller rider—riding the XL or XXL—you might need the Regular post, with the moderate backsweep. This, because the seatpost sticks straight up, at 90°, so, the taller the bike size, the nominally steeper the bike is already.
Not to beat on this subject too hard, but [Digression back on], how difficult is it to do what Specialized has done? Why can't bike companies who seek to sell to triathletes just take a digital level, pass it through both the bottom bracket and the center of the saddle's rails as the saddle is pushed all the way forward, and see if the first number is 8. It can be 80°, 80.5°, 82°, but, the first number needs to be 8.
It needs to be 8 as the saddle sits at a representative height from the pedals in each size, that is, it needs to adjust forward to 80° or steeper in the smallest size (when the top of the saddle sits 67cm from the bottom bracket axle), and in the largest size, when the saddle sits 85cm from the BB axle (and for every saddle height in between). Note to product manager (or engineer, or bike designer): if the first number on your digital level is a 7, go back to the drawing board. Literally. You can figure this out in SolidWorks, or, using a little junior class trig. This will save the trouble of wondering whether your design gets riders steep enough.
