I can give you one really good argument in favor of T47, but first…
I first heard about the T47 bottom bracket from a coworker I didn’t get along with at the bike shop where I worked while Wes and I were getting BBInfinite off the ground. My first thought was “Oh, crap, I’m in the pressfit business. This isn’t good”. Then I found out more about T47 and figured we’d just start making the best damn T47’s the world had ever seen. Then I found out even more and realized that T47 is going to limp along in small frame builders’ bikes for a few years, maybe a decade, until it lies to rest with the Octalinks, ISIS-drives, and the cotter pinned crank sets of yore.
Don’t get me wrong, I’m no hater. I wish the T47 bottom bracket and the folks who toiled to bring it to the market well. If it does catch on we will make them, but I just don’t think that will happen for some fundamental reasons.
For those in need a primer, here's the T47 skinny from the guys who birthed it.
Which manufacturers are going to use T47?
This is the biggest strike against the T47 bottom bracket (aside from its bulky, tool-notch festooned ugliness), and that is, it’s a design that doesn’t translate well to the ultra-wide form factor BB shell formats favored by most industry-leading manufacturers, systems such as BBRight, BB386 Evo, BB86/BB92, and so on. Frame designers like the wide bb shells because of the stiffness they provide. Add to this the need to make frame bb shells wider to accommodate wider tires while maintaining wheel base for handling feel and it's easy to see what a pickle T47 was in at birth just two year ago.
I mean, why would Cervelo, who's touted the superiority of wider bb's for going on a decade, abandon their own BBRight standard in favor of one developed by Chris King that's simply a threaded Cannondale PF30 bottom bracket design? The only major player I can imagine who might consider T47 would be Specialized simply because they seem completely adrift on the bottom bracket issue of late. The reason Specialized would only look at T47 for about a minute is the second reason the “new” standard is doomed: Weight.
Holy 145 grams Batman, that's one helluva hunk just to fit a Shimano crank! Add another 80-100 grams if it's a carbon frame, folks.
Seriously Heavy Metal
We here a BBInfinite have put our products on a diet of late, trimming as much weight as we can with our fancy new CNC machine to optimize each bb we make. It's just what you've gotta do in this industry where less costs more, at least when it comes to mass. The T47 bottom bracket doesn't afford an opportunity to lighten its structure because a substantial hunk of excess material is required to form threads. In truth T47’s are not outrageously heavy on their own, but the mandatory support structure bonded into the frame is another story.
And a sad story it is. Any manufacturer specing T47 in their frame sets is committing to a minimum 100-gram weight gain just to make a home for a T47 bb. This means a sub 1,000 gram, T47 frame set just got a lot more expensive at a time when sub 900-gram frame sets are cheaper than ever. Any BB86 bike will be at least 100 grams lighter, loads stiffer, and cheaper than a T47 bike. In summation: You’d just have to really, really want T47 to pony up for one. I can hear someone screaming, “You’re missing the point, man, T47 won’t creak like pressfit”. Um, pressfit doesn’t creak, it’s crappy pressfit bb’s that do. Get a BBInfinite and the argument is moot. It’s funny how merely stating facts can sound like hating.
I didn’t mention that pressift arrived to address the widespread delamination problems one runs into whenever dissimilar materials are bonded together, e.g. aluminum to carbon. The former expands and contracts readily, the latter does not. Now for point three: The T47 bottom bracket is a retrograde maneuver.
Deja Vu All Over Again
Whenever technology changes there are always those who can't see it’s obvious merits past the inevitable initial implementation problems. Take fuel injection in automobiles for instance, or electronic ignition, or cell phones, or anything that’s arrived in our lifetime. All technology moves from naysaying to can’t live without it in short order. Press fit bb’s are this way. Press fit is the best possible system that the bike industry chose to implement in the worst possible way. Anyone remember threaded headsets? Does anyone seriously want that hackneyed crap on their brand-new, wind-tunnel-tested, carbon monocoque wunderbike with programmable electronic shifters shod with a $3,000 carbon wheelset? Nope. Why? Because technology supersedes. Press fit has now been perfected, so why rummage through the Bygone-Era-Tech scrapyard to address a problem that no longer exists?
Oh, and that good reason I see for using the T47 bottom bracket: In Ti and steel bikes because the threads are cut directly into the frame. But is it necessary? Can’t you do the same job with an English or Italian threaded bb? But what about a 30mm spindle, one might ask? Answer: Just get a 30mm spindle crank set and one of our 64 grams-a-set, BSA30 bottom brackets and you’ll be lighter than anything else on the market. By far. So where does that leave the T47 bottom bracket?
I feel sorry for the T47. Being born an anachronism is a bummer.
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We are not trying to cut all the way through the alloy at any time. We only want to thin it out as much as possible so we can crack it easily. Let’s think of it as aggressive scoring...