Help picking frame size
I posted this over at Slowtwitch first and have not recieved any responses as everyone is too busy fighting about other things 
Sorry for the long post but if anyone has other thoughts or I'm missing something in my logic below please let me know....
I'm moving to a new bike frame this year and am trying to decide if I want to size up like Dan has suggested in multiple recent articles.
The aerobars are staying the same for at least this year and only the frame is changing. I'm very pleased with my position overall and have been in it for 2+ years, but I like to be able to tweak it a little as well.(i.e. lower for shorter races, or higher in the early season)
My current frame has a stack of 512 and reach of 395. For 70.3 ironman, I use a 120mm -17 stem with 30mm of top cover/spacers which make the effective handle bar stack 541 and the reach 506. I'm 5'8", this postion has 130mm of drop, and I use Vuka Bull/Clip which are not the lowest stack high but lower than many options out there that I might consider in the furture.
Therefore my goal is to have the same stack/reach but allow for a stack adjustment of at least 15mm lower and not limit my options on future aerobars too much. I can achieve this position on either a small or medium frame and am not sure which way to go.
Small Frame - S500 R415. With a 100mm -6 stem and 25mm of top cap/spacers the effective handle bar stack is 543 and reach is 506. With a -17 stem I would have 40mm of spacers. I have plently of room to go lower and 100mm seems like a good stem length to allow for future adjustments if need (or to change aerobars), but this means I have a decent amout of spacers (25 to 40mm) which Dan does not recomend.
Medium Frame - S520 R430. With a 80mm -6 stem I only need a 10mm of top cap to achieve my goal effective stack and reach (S545 R505) and I can still get down about 15mm lower by going with a -17 stem for shorter races. I could also run a -17 stem 25 mm of top cover/spacers to be in my ironman position. My concern here is that I'm going have less options for future adjustments as I can only get 15mm lower with common stems and would need an adjustable or extreme angle if I ever change aerobars (i.e. higher stack).
So I guess the question comes down to:
A) Small with 100mm -6 stem with 25mm of spacers - lots of flexibility but doesn't follow Dan's advice (25-40mm of spacers) 
Medium with 80mm -6 with 10mm spacers or 80mm -17 with 25mm spacers - less flexibility for future changes but follows Dan's advice (10-25mm of spacers)
What do the slowtwitch experts recomend...
Optimize based on my current position(B) or leave some room for future changes by having between 15-30mm of additional spacers(A)?
Will the 15-30mm of additional spacers actually make any difference in anything but how the bike looks?
Thanks!
Comments
@Matt, I am no expert. I think if you have arrived at your position that you favor, you like your aerobar to the point that there will be no need to tweak anything but change between positions you describe, I think you can probably go with B choice. 15-30mm of spacers is really no issue in any way, even the looks.
The adjustments you are talking about are very small and don't think you will need anymore than that. You are pretty much where you are, no significant rotation around BB will occur for you, so I think you are safe with B. Gives you enough to experiment too.
Uh, long thread over there, did not like the tone, much like norm these days. Surely missed your post, but keep bringing it up there. You are likely to run into a more complete answer.
@Beth, I actually "thought" the trend was the opposite now, but I haven't really read anything the other way. The only thing I have read on it is Dan Empfield recomending to size up.
@Chris, The good news is this time around it's a two year contract, so unless i decide to do something else next year I wont have to get a new frame for the 4th year in a row ;-) . Actually, one thing to add is the new frame as a seat mast I have to cut to lenght, which sucks for resale. So, now I'm thinking the small might help with resale as it will leave more post on the small frame and therefore it will likely be easier to find someone my height or shorter that wants a small, then someone 5'8" or shorter that wants a medium.... thanks for making me think through that side of it more.
@Matt - I can't find any literature, but I remember lots of commentary while watching Kona on this. Can anyone else verify?
Matt,
I'm not up on my stack and reach lingo but two thoughts:
1) Will the small frame get you over the front tire more, that is a little more twitchy in handling. Any big descending racing on you calendar?
2) If you don't find answers in the house or at ST look for some comments from Todd at TT bike fit. It was very cheap for me to get optimal frame choices when I was looking last year.
Gordon
What about a bike with a new front end like the Felt or speed concept bikes??? Not sure how that new fork and "thingy" combo work as opposed to spacers...just a thought...and maybe not much of one at that. Let us know what you find out/decide. Good Luck!
Ebe
@Beth, in the last year, Dan Empfield has written extensive articles on stack and reach, frame size selection, spacers and aerobar choices. The conclusion of the articles is choose the largest frame you fit on as that will eliminate the need for excessive number of spacers..........means more aero/less drag system set up. He does a nice job explaining it way beyond what we need to know. Matt has studied it well and applied it in his personal example, has arrived at a narrow window of positions that work for him and is now selecting the frame in accordance.
Check the ST library of articles. Good read if you like the subject.
I think you may have answered your question when you talk about the amount of time you're likely to have this frame, i.e., 2 years. As I recall, your main focus for that period of time is to do well at WI and thus Kona, not go out and win the USAT sprint championship. Given that, the main focus of your bike can be determined from your goals and time frame. You do not to worry about radically changing aero bars for a radical change in racing style in this period of time that I can tell.
Let's be honest - you're shooting for the semi-pro level of training/performance, and at that level, a few hundred dollars of resale value two years down the line can't be your first priority; it has to be an "if all else is equal" decision. Figure out which bike best suits you for the next two years and go with it.
To me, that sounds like option B if you buy Empfield's latest opinions on the matter, but you're the guy to think it through.
1) shorter tube lengths will always make a stiffer bike.
2) having more room to go lower will let you truly experiment with different front ends. I'm bottomed out on my Felt 54 due to the bayonnet fork, and wish I could get it just a little lower.
3) while I appreciate what Dan E. is up to in recommending the most bike (vs. spacers) to fill up the stack and reach you need, I'm not sure that it's a perfect universal recommendation. Different factors will influence the rider/bike complex of aerodynamics around the stem/head tube area, such as the elbow width, the orientation of the stem, the presence or absence of a LYC/Joule on the stem, the presence or absence of an aero bottle between the aero bars, etc, such that I'm not sure you can make the blanket statement that 'more bike filling up your required stack and reach is better aerodynamically'
4) my guess is that the steering will feel a little more 'normal' with a 100mm stem than with an 80mm stem. Worth trying out someplace where that's an option (though you probably don't really have that, being in a snowy area right now)...
All that said, you probably can't go wrong with either, so best of luck!
BTW, that's a sweet bike you're sizing up! I don't know too many people riding the brand, but those who do are fanatically happy with it.
@Matt, on Mike's no. 3. That really is a valuable consideration. We tend to forget how much we dirty up these frames after we load all our stuff. Great that Mike points that out.
On Mike's no.4, I have been riding with a 70mm stem on E112 size small, I have a 15.5cm drop, 5'9", I use the same drop for everything from 40k TT to 100mi+ rides. Steering with Argon18 is unaffected as it is a extremely stable ride.
Stem length is not that critical with most tri bikes. Go with a choice where you can change in a direction you need to.
Most of you figured it out anyway, but the new bike I will be riding for the next two years is a Ridley Dean. Our entire Zoot team is switching (as Cary mentioned). The team was on Orbea Ordus for three years and I just happened to join them for the last year. The contract with Ridley is at least 2 years and then is up for renewal.
There are tons of benefits I have been able to enjoy from playing the sponsorship game, but there is no such thing as a free lunch either....
@Aleksandar - funny - my E112 small is on my trainer right now. Depending on which aerobars I put on it I either use a 80mm or 100mm stem and I have 13.5cm drop either way. Still have almost 40mm of spacer/top cap there as well :-( . When I bought it my saddle height was 20mm lower and hence my bars where 20mm lower as well... but when the seat went up the bars did as well. Do you happen to know your ST FIST fit coordinates? I would be currious to see how we compare.
@Matt, here is the detailed description, don't know if I am going to hit all the coordinates but I will describe it :
2008 Argon18 E112 Size Small, Dura Ace with Team FSA crank 172.5, Vision cockpit with ski tip extensions 270mm, Vision Sizemore stem 70mm
no spacers, aerobar with lowest possible stack
saddle all the way forward
Measurements:
saddle height 75.5cm
saddle nose to:
BB 2cm ahead of BB
aerobar pads 42.70cm
stem 46cm
aerobar tip (shifter housing center) 76.2 cm
aerobar drop 15.5cm
According to Dan's formula for effective seat tube angle I sit between 79 and 80 degrees.
Let me know how your numbers are.
We are so close we could probably trade bikes and would barely notice....
Here are mine for my e112...
Saddle is 23mm in front of BB
Saddle height is 747mm
Saddle to back of pads 430mm
Saddle to shifter (bolt) 780mm
Saddle to pads (drop) 135mm
At the moment I have HED blackdog bars on and a 80mm stem with almost 40mm of spacers (including top cap). When I put my zipp bars from my race bike on I use a 100mm stem and closer to 25mm of spacers.
That is too funny. If you ever are traveling through Kansas City and need a ride for training, you got your clone bike here. It is not quite used to your wattage level, but it is getting there. By the time you come, it will be ready.