# Help with Sizing a Newbie



## xzebra (May 30, 2009)

I am looking at a Giant OCR 3 (2006) and was wondering if that is a decent bike to start with?

Also could someone help me understand what size I would need?

Based off a online calculator (https://www.competitivecyclist.com/za/CCY?PAGE=FIT_CALCULATOR_INTRO) my measurements were as listed below:

Seat tube range c-c	55.1 - 55.6
Seat tube range c-t	56.8 - 57.3
Top tube length 52.2 - 52.6 
Stem Length 10.2 - 10.8
BB-Saddle Position	78.1 - 80.1
Saddle-Handlebar	49.5 - 50.1
Saddle Setback 4.8 - 5.2

But how does this translate to these sizes from Giant:


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## PJ352 (Dec 5, 2007)

Something doesn't add up with CC's recommendations. They are basically sizing you to a (roughly) 56cm frame, but it's spec'd with a (presumably effective?) TT in the mid 52cm's which is normally found on a 51/ 52cm frame. For a frame that size you'd normally be looking at an effective TT in the mid 55-56cm range. 

I suggest you go back and redo the measurements. Also, to serve as a double check, go through the sizing process at:
http://www.wrenchscience.com/default.aspx


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## Fredrico (Jun 15, 2002)

*Are you a woman?*

The seat tube recommended is 55 cm. That's for leg length, on a horizontal top tube frame. 52 cm. recommended top tube is too short for a 55 cm. frame. So you'd have to go with a shorter seat tube. In the chart, the "w S" frame would probably fit well. The top tube matches, 52.2 cm. You'd just raise the seatpost to the recommended 78-78 cm. height from bottom bracket center. The trick is to make sure the handlebars end up not over 2 inches below the saddle height. If they are, there will be too much upper body weight transferred to the front wheel, and you'll be uncomfortable.


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## wim (Feb 28, 2005)

The calculator gave you a seat tube range for a conventional frame, which the chart in the linked article translates into Giant's compact road frame sizes. The article at the link is quite old, so its possible that the numbers have changed slightly and that some sizes are no longer available while others aren't shown. Still, the article gives you a general idea of the Giant sizing system and should be of some help.

http://archive.giant-bicycles.com/us/050.000.000/050.600.100.asp


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## PJ352 (Dec 5, 2007)

wim said:


> *The calculator gave you a seat tube range for a conventional frame*, which the chart in the linked article translates into Giant's compact road frame sizes. The article at the link is quite old, so its possible that the numbers have changed slightly and that some sizes are no longer available while others aren't shown. Still, the article gives you a general idea of the Giant sizing system and should be of some help.
> 
> http://archive.giant-bicycles.com/us/050.000.000/050.600.100.asp


Yes, but the numbers still don't add up, even when compared to Giant's geo chart.

Using the chart you linked to, Giant compares a traditional STL of 55cm's to their medium, with a STL of 50. But the TTL of their meduim is 55.5, not the mid 52's that CC recommends. So, unless I'm missing something, the numbers still don't add up. 

One comment to the OP. When checking geo of the compact geo/ sloping TT bikes, it is recommended to focus on TT rather than ST, because (generally speaking) if you get the TT length right, the frame size will be correct. I say generally speaking, because if your numbers are in fact correct, you might be a candidate for custom geo.

EDIT: In the event you are female, then at a stretch, the women's M may work. The TT of 54cm's is 1.5cm's longer than CC's recommendations, but they also recommend a stem of 10-11cm's. Going to a 8-9cm stem could possibly bring reach into a comfortable range. I wouldn't buy before trying, though.


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## wim (Feb 28, 2005)

PJ352 said:


> Yes, but the numbers still don't add up, even when compared to Giant's geo chart..


I agree, but it's not surprising. You're dealing with at least three variables here: the OP's self-measurements, Competitive Cyclist's idea of what constitutes a good fit, and Giant's assumption of which traditional frame sizes match their sizing designators. With all that vagueness, my recommendation would be the quote from your post: "try before buying." Beginners using on-line fit calculators is a questionable premise anyhow—the amount and degree of detail is useless and overwhelming.


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