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PostPosted: Thu Dec 20, 2012 8:40 pm 
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https://docs.google.com/open?id=0B1JPD57r2Hyrb3FsdVRsR2k0Nmc


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Posted: Thu Dec 20, 2012 8:40 pm 


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PostPosted: Sun Dec 30, 2012 4:42 pm 
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I assumed tip-to-center of saddle was 140 mm, based on my stripped SLR:

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PostPosted: Sun Dec 30, 2012 5:18 pm 
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If you wanted to build a bike which fit the cyclists the best, you'd use a 66 degree STA and offset the seat tube forward by 94 mm relative to the BB. That's a radical version of this:

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PostPosted: Tue Jan 01, 2013 8:40 pm 
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A lot of full suspension mountain bikes do that, the Specialized Epic comes to mind. Also, back in the day Basso made a full carbon bike with that feature being touted. It may have been a rebadged Aegis?
edit: here is the Aegis.
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PostPosted: Wed Jan 02, 2013 11:17 pm 
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Dan Emfield, though a triathlon pioneer by background, has very similar data and recommendations based on his research on road bike fit.

He apparently did some collecting of data and also found an 9% average setback of saddle height from pro tour riders in the Mediterranean area: http://www.slowtwitch.com/Bike_Fit/Road ... _2631.html


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PostPosted: Thu Jan 03, 2013 12:54 pm 
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To the OP,
Not trying to be disrespectful, I just don't see how this is helpful for an individual setting up his or her bike. Our physical attributes dictate bike set up, regardless of our status as a pro rider or not. Perhaps I am missing the point, but I'll stick to the plum bob when setting up a bikes saddle position. What anyone else does is not my concern.

As to weight distribution, IMO a very important attribute for a well handling machine, that is best dictated by the bike's geometry. (I love custom frames). I would not risk my knees trying to alter my weight distribution by compromising fit :beerchug:

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PostPosted: Thu Jan 03, 2013 6:43 pm 
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thisisatest wrote:
A lot of full suspension mountain bikes do that, the Specialized Epic comes to mind. Also, back in the day Basso made a full carbon bike with that feature being touted. It may have been a rebadged Aegis?
edit: here is the Aegis.


Wow -- cool! It seems the seat angle is around 66.8 degrees. ("There are no new good ideas...")

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PostPosted: Thu Jan 03, 2013 11:58 pm 
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djconnel wrote:
If you wanted to build a bike which fit the cyclists the best, you'd use a 66 degree STA and offset the seat tube forward by 94 mm relative to the BB.

Wouldn't this mean this mean a decreased STA (measured relative to the BB) for higher saddle-heights?
And isn't that opposed to the Cervelo fit that dictates equal STA irrespective of rider size?


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PostPosted: Fri Jan 04, 2013 12:53 am 
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1. Yes.
2. Yes.
You are measuring the knee relative to the pedal spindle (not that I believe in KOPS, that's another topic). As the legs and feet get smaller, the knee ends at the pedal spindle, not the bottom bracket. That's at least one way to look at it.


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PostPosted: Fri Jan 04, 2013 1:17 am 
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Although if the pedal spindle is proportional to height, which it generally is not, then it still converges on the bottom bracket. My regression converges 93.5 mm ahead of the bottom bracket, which makes sense consistent with your description if the crank length is scaling less than proportional to height, as is typical. But this would be the zero-height extrapolated crank length assuming KOPS.

Indeed looking at the Aegis frame, as I hold a piece of paper up to my screen to extrapolate the seat post, it appears it intersects the crank arm a bit more than half way along its length, quite close to the 93.5 mm I derived from the data.

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PostPosted: Fri Jan 04, 2013 4:06 am 
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Good point. Obviously I havent given this much thought. and by "pedal spindle" I assume you meant "crank length".
Others to look at with this characteristic are the Klein mantra, Ibis Szasbo (or something like that), some others I'm sure.


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PostPosted: Tue Jan 08, 2013 3:12 am 
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Think it was the other way around Aegis made the frames for Basso. Aegis really did some neat things. Unfortunately they did not keep up with the times , 1 1/8 headtubes, internal cable routing, spending some time in a wind tunnel. Apologies for the slightly off topic post.


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PostPosted: Wed Jan 09, 2013 3:50 pm 
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rustychain wrote:
To the OP,
Not trying to be disrespectful, I just don't see how this is helpful for an individual setting up his or her bike. Our physical attributes dictate bike set up, regardless of our status as a pro rider or not. Perhaps I am missing the point, but I'll stick to the plum bob when setting up a bikes saddle position. What anyone else does is not my concern.

As to weight distribution, IMO a very important attribute for a well handling machine, that is best dictated by the bike's geometry. (I love custom frames). I would not risk my knees trying to alter my weight distribution by compromising fit :beerchug:


The idea of this thread and this information is to counter the BS assertion that pros run ungodly amounts of setback to compensate for the puny frames they ride; that no Fred or weekend warrior “needs” pro setback. The people searching the internet for fit advice are more likely to be amateur riders without enough experience to know where to start. The more people that can learn to appreciate some setback instead of being basically in the pushup position on their bikes, the better. Nonetheless, I specifically stated that this could be geared toward the racing/go-fast crowd to make for a more apples-to-apples approach. Arguably, pros are the world's most efficient riders on their machines, so just about everybody could benefit from some aspect of their fit.

It may seem like a useless measurement, but with KOPS more likely to be an incidental finding than a desired endpoint (especially since cranks parallel to the ground is NOT the point of max power/force in the pedal stroke), this is a pretty useful way to check your own fit against a pretty professionally fitted crowd. Your statement works both ways. Were I to use a plumb bob and set myself up for KOPS, I'd have 65% of my weight on my hands. Since you also state I shouldn't be compromising weight distribution, perhaps you need to reevaluate the effectiveness of your advice. Apparently, Dan Empfield came to a pretty similar conclusion about avg % setback and felt the need to write an article. Maybe you should swing by slowtwitch and tell him “no offense but...”

I've been thinking about the upper-leg/lower-leg length issue as well. Considering how the % setback-to-saddle height changes markedly with height, I'm wondering if increased height (6'0”+) exaggerates these measurements, resulting in the 11%+ for guys like Boonen, Hincapie, Cancellara, etc. The other side of that are the short riders with the 3-5% setback measurements.

For the majority of people, though, this is a better starting point than KOPS. As I believe KOPS is an incidental finding, a person of average height and average inseam could stat at 9% and move themselves forward or back by a mm or two and probably be in the correct spot behind the bottom bracket ina single ride.


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PostPosted: Wed Jan 09, 2013 4:00 pm 
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I couldn't agree more.


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PostPosted: Wed Jan 09, 2013 4:19 pm 
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Fascinating stuff, I can't wait to get home and compare some measurements on my bike.

Thanks to all who contributed :beerchug:


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Posted: Wed Jan 09, 2013 4:19 pm 


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