Nice one elviento

IMHO a frame that is built with straight tubes (carbon or steel or ti) must have a traditional geometry.
Aesthetically speaking it is all about pure elegance, 'confidence' and class.

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Andy I have not seen the data, though they moved to a more traditional brake for their Shiv and outright said it is less aerodynamic than their old brake on the Transition, though the amount is very small and that the purpose of the new shiv was a faster, more user friendly bike, a la a new front brake without a cable hanger.

You have to remember that, though the cable plate is not ideal, you are ridding your self of the frontal area of the housing by moving everything in front of the headtube. Whereas a traditional brake, you have a fair bit of the brake sticking out past the fork crown AND the housing running down to the brake. It's a numbers game and you can believe whatever you want.

Specialized's claims have been independently verified through aerodynamic field testing by posters on another forum.

I have been in contact with the person and seen his data. The modified center pull brake that he did his testing on tested to be about the same as the Simkins aero brake But the T726R brake is a bit better than the one that he tested.

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Not about me believing, we don't operate like that. If you could pm me the data I can give it to our aerodynamicist Nick for verification. It would be great to see how the reduced frontal area of the brake cable justifies screwing up the airflow over the headtube and subsequently over the rest of the bike at that elevation........ If that is the case we will have some pretty hard data that cables (or cables with housings) are very, very draggy indeed!

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I like the English frame with lots of slope the best.

A few things to consider:

The sloped frame has stiffer support for the rear brake. Could be noticeable with tiny stays.
The sloped frame is stiffer/lighter torsionally.
The sloped fame has more flex in the seatpost area... could be good for comfort, but bad if it is laterally too much.

Yes these are all good points. One challenge is that generally "laterally stiff yet vertically compliant" designs are generally not very aero. Slope or not in my mind is 90% aesthetics and style, and 10% functionality (the points you said). So a moderate slope is what I will go with...

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Lost a lot of sleep over this... Was leaning towards BB386 but after more thought (and as suggested by a knowledgeable ww member), decided in favor of PF30 (46mm x 68mm).

Compatibility is good -- it allows for the majority of cranks w/ adaptors; stiffness should be a bit better than BSA depending on cranks used.

Why not BB386?

Other than adaptors availability, I do not believe it's a better design.

If you look at history, when it was clear BSA needed improvement from an engineering perspective, people came up with outboard BB cups -- a half asset approach, which pushed cranks further out. Cranks became thinner laterally coz bearing cups do not leave much space for crank arms.

For example, current campy crank arms are much flatter than the square tapered version, and you have to over build the cranks to achieve the desired stiffness. That's why a whole frame is 700-1100g, and a friggin crankset has to be 600-800g.

Too much emphasis is placed on the frame, hence it gets lighter and lighter with wall thickness of around 1.5mm. But carbon cranks have much thicker walls. BBright and BB386 widens the BB shell to the max, while it's the poor old crank arms that take the most load much more directly coming from the pedals. In other words, the frame "cheated" for more (and unnecessary) width, as a result of the outboard bearing movement. Poor cranks are stuck with no room to be optimized. This is true for BB386, BB86, and BBright.

Not to mention ankle clearance and Q factor.

This is unfortunate, because the industry is less integrated, and Cervelo/BH/Wilier don't know how to make a super lightweight stiff crank with thin walls.

Exactly why Cannondale is so superior in this area.

Look's system is actually not bad but its proprietary-ness is self limiting.

If THM could develop a large but short spindle version of the Clavicula, it'd kick everybody's ass.

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Here is the contemplated seatpost. A bit early to talk about weight now but aiming for 120g w titanium hardware.

Comments welcome.

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I like the version on the left with the bolt going through the clamping mech to keep it hidden. I can see why others might like the right side so that you do not have to remove your saddle but I have the left style system on my English and do not have an issue with it.

With that being said, would you be able to rotate the seatpost 180 degrees to have it more forward. Only reason I ask is because if this is going to have aero properties then you could flip the post, slam the stem and put on some aerobars for a local TT or Triathlon from time to time.

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ISP heads could be much simpler and lighter

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The current plan is indeed to allow a flip which is not meant for tt geo but rather to mimick a zero offset post. This is because my entire seattube will be approx 10mm "off center". With 10mm setback on the topper, that's a total of 20mm setback. Flipping it will not achieve a tri/tt position but rather a 0 setback position. But an option between 20mm and 0mm setback with practically no weight penalty in my mind isn't too bad.

The top portion of the mast will be symmetrical to accommodate this "flip" feature, although the rest of the mast will remain "egg" shaped.

My next project will be more of an aero bike... but that's probably 6 mos away.

Epic -- would you care to elaborate a bit? If you are referring to the Tune/MCFK toppers, those are nice and indeed light, but I am not going with it due to the lack of setback and the general flimsy-ness (at least visually) of the "scale" design, plus my aesthetic preference for the topper to be "inside" the mast.

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I wasn't referring to any design that's already in the market

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I'm sure everyone would be interested to hear your thoughts on the subject.... but... and not to be rude at all, but a one line post simply saying you could do better with out any other advice isn't particularly helpful. Again, not at all trying to be confrontational, just trying to find out exactly what you might have in mind.

@elviento
I'm enjoying the thread, and excited to see what comes of it all.

I guess I don't think the topper needs to be that complicated either.


I'm picking on you again

edit: Thought I should say that your idea for a flippable setback/no setback topper is definitely a good one though.

No problem. I am here to be picked on, mate. LOL.

I guess adjustability is the devil here (otherwise, look at Berk's integrated seat+mast). I do agree with you that it should be simple. I seem to have something looming on my mind but I just cant see it now.

Here is something I came up with that offers around 15-20mm of adjustment including tilt. But it's still not good enough for me.

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