I’d checked this bike out when it was first revealed, but until recently had never looked at the geometry chart:
http://www.boardmanelite.com/AiRTT1_spec.pdf
According to my calculations, the size M frame has a reach of 41.8 cm and a stack (ignoring headset top cap) of only 45.8 cm. That is 1.3 cm longer, but 2.4 cm lower, than a 51 cm Cervelo P3 (i.e., the smallest size that takes 700C wheels). Yowza!
Pretty sweet. The front center/rear center are a little more like that of a road bike as opposed to a TT bike, I think. Or maybe it’s just early…
Would be a sweet aero-or-die road race rig.
I’m still waiting to see some drag numbers on this bike before I assume it to be fast!
It’s defiantly designed to get you low. Boardman was interviewed about aerodynamics in a triathlon supplement to Cycling Plus here in the UK. He made mention that they built what riders need, not what they want. However later in the article he stated they have new, less aggressive, frame in development at this time. There’s an aero road frame like Cervelo and Felt coming too.
can i ask how you got those numbers? i get quite different numbers from you…
edit: in particular i am wondering how a headtube length of 8cm at 73* can have a 2.4cm less stack than headtube of 9cm at 72.5*.
can i ask how you got those numbers? i get quite different numbers from you…
edit: in particular i am wondering how a headtube length of 8cm at 73* can have a 2.4cm less stack than headtube of 9cm at 72.5*.
I calculated the stack as:
sin of seat tube angle (deg) * seat tube length (cm)
i.e.,:
0.961 * 47.7 cm = 45.8 cm
Of course, the seat tube length is measured c-to-c, so in addition to the top cap dimension you’d also have to include the radius of the top tube…but neither of those corrections would change the fact that the Boardman AiRTT1 (especially in size M) has a greater reach:stack ratio than even a Cervelo P3.
I also have been looking at this frame. I think it retails for about 2500 British pounds ~ $3,600 USD. Bike radar also has a review for another frame with similar geometery (i.e. short head tube) and it retails for only 699 quid or ~ $1,020 USD. Their favorable review is here: http://www.bikeradar.com/road/gear/category/frames/time-trial-triathlon/product/f1-zero-tt-28277
Their website is here: http://www.dalkiia.com/
I am very, very tempted by buy this frame. I’m currently looking for a 57cm frame with a short head tube and this one certainly fits the bill.
Dave in VA
i have no doubt that the stack would be lower, just not 2.4cm lower. In fact i think the difference is less than 1cm in stack.
Whether or not you believe this <1cm stack difference is worth the 500GBP cost premium of the Boardman frame over the P3C is another issue altogether.
You’re right that the stack:reach ratio is better though.
i have no doubt that the stack would be lower, just not 2.4cm lower. In fact i think the difference is less than 1cm in stack.
Just out of curiousity, why? (I noticed on the Cervelo website that they appear to define stack as the vertical distance from the b.b. center to the centerline of the top tube, which corresponds to how I calculated stack for the Boardman frame.)
Whether or not you believe this <1cm stack difference is worth the 500GBP cost premium of the Boardman frame over the P3C is another issue altogether.
Did I ever say that the Boardman frame was worth even as much as a Cervelo P3? IMHO, the P2 is a better comparison (in which case the premium you’d pay for the Boardman is even greater).
Anyway, the only reason I mentioned the Cervelo sizing is because 1) they’re well-known to be “long and low” (and yet the Boardman out-limbo’s them), and 2) up until a few months ago that is what I was riding.
You’re right that the stack:reach ratio is better though.
I never said it was better - just different.
i think the stack difference is less than 1cm because the headtube length difference is 1cm, and the boardman headtube is steeper and so in theory should have a bit more vertical height than the slacker Cervelo. All things being “equal” (e.g. assuming for the sake of argument that the same fork is used), i just don’t see how 2.4cm stack difference can be achieved here. Is there a flaw with my assumptions?
Edit: from Cervelo’s diagram, stack appears to be from centre of BB to horizontal line going through the centre of the top dimension of the headtube, not the centreline of the top tube.
Assuming a 368mm fork I get the stack of the small to be 2mm higher than 51 cervelo and reach 8mm shorter. Calculated from front backwards rather than relying on seat tube measurements
i think the stack difference is less than 1cm because the headtube length difference is 1cm, and the boardman headtube is steeper and so in theory should have a bit more vertical height than the slacker Cervelo. All things being “equal” (e.g. assuming for the sake of argument that the same fork is used), i just don’t see how 2.4cm stack difference can be achieved here. Is there a flaw with my assumptions?
Not that I can see. However, you are assuming that the forks are equal in length (which isn’t always the case).
Edit: from Cervelo’s diagram, stack appears to be from centre of BB to horizontal line going through the centre of the top dimension of the headtube, not the centreline of the top tube.
I agree - I was looking at the solid line, not the dashed line just above it.
Assuming a 368mm fork
But is that a safe assumption?
I suppose another way to look at it is this: despite a 0.5 deg shallower head tube angle and 0.3 mm more fork offset (aren’t all Cervelos spec’d at 4.6 cm?), the front center of the 51 P3 is 0.1 mm less than that of the M* AiRTT1. That means that the effective top tube length (i.e., reach) is greater on the AirTT1. Yet, based on the difference between the stated standover heights and b.b. drops the two bikes are equally “tall”.
*You compared the Cervelo to the size S AirTT1, not the size M.
EDIT: I’ve modified the subject title to clarify that it is the middle size that really stands out.
But is that a safe assumption? Generally yes. It doesn’t appear to have a lot of crown stack (like a scott CR1 for instance) and 368mm is pretty common. It’s unlikely to be more than 4mm either side of that figure
I suppose another way to look at it is this: despite a 0.5 deg shallower head tube angle and 0.3 mm more fork offset (aren’t all Cervelos spec’d at 4.6 cm?), the front center of the 51 P3 is 0.1 mm less than that of the M* AiRTT1. That means that the effective top tube length (i.e., reach) is greater on the AirTT1. Yet, based on the difference between the stated standover heights and b.b. drops the two bikes are equally “tall”.
Ah, if we’re looking at the M I see what you’re saying. It’s very long. If it weren’t so expensive it would be a good choice for one of my friends (who I suspect of being very aerodynamically gifted if we find the right bike, w/kg also very good) who takes a very long and low position.
Cervelo use 43mm rake on all sizes except a couple of the RS ones.
i’m getting stack = 499mm and reach = 406mm. i’m going to to back and check, but i think that’s pretty close. yes, that 80mm head tube is very short, which should drop the stack. but the BB drop of 67mm is 7mm more than cervelo which, normalized for cervelo, adds 7mm to the stack. so on paper, just using BB drop and HT as a gauge, the boardman would be right at 480mm or so. why am i off by 19mm? i don’t know. you’re 22mm in the other direction.
i think this bike is really pretty darned close to a p3 in 51cm. they have identical front/centers, by my calc identical reach, and pretty close on the stack. i think you can ride it, andy 
i think you can ride it, andy
Not interested, really (especially at that price!). I was just struck by the fact that, at least in size M, the bike appeared to be very long and low. If it turns out to be only long and low, well, so be it…
if we’re looking at the M I see what you’re saying. It’s very long. If it weren’t so expensive it would be a good choice for one of my friends (who I suspect of being very aerodynamically gifted if we find the right bike, w/kg also very good) who takes a very long and low position.
Does he race under UCI rules? I ask because my own personal desire (not really a need, since stems come in different lengths) for a TT bike with an uber-long top tube evaporated with institution of the 80 cm limit. Prior to that, I was out at ~85 cm or so.
well actually the Cervelos use forks with a 43mm rake so rake-wise they are the same as the Boardman fork.
Either way, if i were to use that frame, i would likely swap the fork out for a 3T funda or in my case a Blackwell Time Bandit anyway.