623/486

you know you could almost switch bikes with BMS just above.

i would always trust drivers achieved on the bike over my math. just, when padx and pady creep closer to each other, such as fewer than 100mm apart from each other for a rider aboard a size L or 56cm or 58cm bike, that's a sign of a very aggressive position, even if you're long torsoed. while this position may in fact be correct for you, i wouldn't expect my math to generate such a position.

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Dan Empfield
aka Slowman

I am on a Large Spec. transition. I have a -45 adjustable stem (long story).
I have never been more comfortable on this bike than these last 2 months since lower the front end with this stem. Power is also up.
My local dealer carries Specialized and Trek. But not sure I can fit either bike.

Here is my current position:
https://www.facebook.com/...p;type=3&theater

i wouldn't counsel any change. that said, on paper, saddle height of 740mm, typical pro or top AG triathlete, the expected armrest elevation drop is about 12.5cm to 13cm, something like that. my guess is you're 16cm, 17cm, maybe more. i don't know.

the reason we don't want those big drops is because you lose mechanical advantage at TDC. however, you can ameliorate that by moving the saddle forward (opening that hip angle back up) and also by going to shorter cranks (making the top of TDC not quite so close to your torso).

because we are afraid of power diminishing with a really low pads position, if your power actually increased then we don't have to worry about that. that's why the math i'm using for this exercise is not for outliers. it's intended to drive you toward the norm because this math is the result of a wager, that if you're buying a bike you haven't seen, and you have no idea what size you should buy and how it should be configured, we'll wager toward the fat of the bell curve of good riders who ride good positions. you're not on the high point of the bell curve. not everyone should be there. you obviously are a case where you need to deviate from the fat of the bell curve.

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Dan Empfield
aka Slowman

Very cool information.

I believe my old position was closer to the fat part of the bell curve. I have been working on getting lower for a few years now.
I use 165cm cranks. Just by luck my road bike and Tri bike have the exact seat height as measured from the flat part of the pedals to the seat. I ride the exact same seat and pedals/shoes with both bikes.


I have added pictures of last years position and this years position

This new position

i MUCH prefer your knew position. just, it is my guess that the MAIN reason your new position grants you more power is what looks to me like a significant move forward. the only thing i would question is whether you're better where you now are or whether raising your bars 1cm or 2cm might generate even more power. i think that's what you have to tune, otherwise i like where you are. for example, here's me from a few years ago:



i think the main difference between you and me is i might be that 1cm or 2cm higher in front than you.

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Dan Empfield
aka Slowman

x = 528
y = 622
height 6'2" inseam 34" so long torso I guess

When I star doing some Aero testing I can evaluate a slightly higher position. I have an adjustable stem on the bike, so it is an easy change.

Right now the power I can generate is within 10 watts of my road bike position (to the best of my ability to compare the two power meters). But I need some time to figure that out. After a race on Sunday I will be spending a few rides with my powertap wheel on the tri bike and two computers so I can nail down the difference between the two.

The new position reflects changes you advised my on last year. So I am glad you prefer it.

well, in that case, your new position looks perfect! change nothing! ;-)

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Dan Empfield
aka Slowman

Height: 6' 1.5"
Saddle height: 800 mm
Pad x: 505 mm
Pad y: 615 mm

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http://www.verynooty.com

657/501

just know that my math adds by design 20mm to the PadY of a top pro / top AGer, because i think the typical buyer will be slightly higher than the typical top pro. so if you were a competitive pro my math would prescribe 637/501mm and that always comes with a +/- 20mm for PadY. in other words, my math assumes, for all comers, math for a competitive pro, just adjusted to the least-aggressive point in the +/- range.

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Dan Empfield
aka Slowman

Height 6'3
Saddle 81.5 cm
Long Torso

Pad X - 533
Pad Y - 645

These were my original measurements for height of 5'9"
Pad x 472
Pad y 609
Saddle height 747
Saddle set back -6
Saddle to pads drop 127




But over a few races I realized I was straining my neck too much to look ahead. So ended up pedestaling the pads by 30mm to effectively get this

Pad x 472
Pad y 639
Saddle height 747
Saddle set back -6
Saddle to pads drop 97

And here is my position from IMC

my math for you yields 617/471, which i'm comfortable with. on padx you and my math agree. on pady my math thinks you need to lower your bars 20mm, but keep them still 10mm higher than your original position. i think you too would like your bars lower, but your spinal stenosis or whatever it is you have that keeps you from looking up when in aero precludes you from having your bars that low.

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Dan Empfield
aka Slowman

I tried the 10mm pedestal for quite a bit after the initial fit ( that first fit was with the alpha X completely slammed) and then just went on the side of comfort and added another 20. Something about craning my neck to look ahead would just hurt. I would love to go lower on the front end.

my math says 670/511. but trust your set up, not my math. for example, my math wants you to be 10mm higher than the mean armrest elevation of a quality pro. that means my 670mm really is 650mm if you're a quality pro. still, i'd love to see a pic. we're off by 20mm on X. but i can believe your 533mm. still, i'd like to see it.

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Dan Empfield
aka Slowman

Ok, would be great to hear your thoughts to this. Hope I converted it right.

1. Saddle height 740, pad stack 615, pad reach 490
2. 5.10" height , 33.85 inseam
3. 170 crank

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-shoki

Another data point for you. My wife is 5'11", saddle height 804mm - lots of legs.

Hi Slowman,

I didn't want to start a new topic since everyone seems to start one right now to get help with their fit based on your calculator, so I thought I should ask it here.

The Diamondback calculator gives me Pad X = 468mm and Pad Y = 602mm for a length of 1698mm and saddle height of 681mm.
However, my recent fit (Pinarello Dogma 65.1 Think 2 converted with Profile clip on aero bars etc) got me a Pad X of 395mm and Y of 580mm (measured to the center of the pad)..

So my bars should be higher but further to the front? My lower back tends to start bothering me a bit on 26+ mile rides so a longer stem seems like it wouldn't really help?

there's a little glitch in the calculator online. the math actually gives you 620/482. but the online calculator is the calculator of last resort, to be clear.

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Dan Empfield
aka Slowman

calculator has a glitch. actual math gives you 585/466

now, as to the pinarello, i don't believe 395mm for pad x center. remeasure. or post a pic to explain how this came about.

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Dan Empfield
aka Slowman

Ok so Pad Y is pretty close (I measured to the middle of the pad because it compresses a bit, so not to the top).

It's a size 51.5 with a 90mm stem, center of the saddle to center BB is 198mm if that's useful.
Measured from center BB to center pad, not the best pic but still can't be far off of 395mm..:

Yeah, played a little with the calculator yesterday.....for ballpark pretty darn close though.

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-shoki

i had no doubt the tape read 398 or 395 or whatever you quoted. what i suspect is either:

1. you're sitting waaaay back;
2. the bike isn't level;
3. you're measuring from spot other than where pad x is measured from.

so maybe we start with point 3: where is the other end of that tape?

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Dan Empfield
aka Slowman

It's measured like this: Bike held straight via a level, plumb which goes through the center of the BB and distance measured from the cord.
Might not be super accurate but it won't be 6cm off..




So can I assume I'm sitting too far back? I don't have a trainer so no moving images, but I could show a pic of my position if you want.
BTW thanks a lot for your time and feedback! Much appreciated.