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Discussion Starter · #1 ·
Hey guys -

I am looking at picking up a new bike...and I'd like a little input on frame sizing. I've done my measurements several times (included below) and with what i've come up with, I'm curious what the general guidance is on frame sizing.

One bike I'm looking at is the Jamis Xenith. The two TT lengths are 53 and 54.5. What other measurements should I take note of to find the best fit? Is it generally better to go with a longer stem and smaller frame or larger frame with smaller stem? Any input would be appreciated!

Measurements
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Inseam: 81
Trunk: 60
Forearm: 34
Arm: 64
Thigh: 58
Lower Leg: 55
Sternal Notch: 142
Total Body Height: 171


The Competitive Fit (cm)
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Seat tube range c-c: 52.4 - 52.9
Seat tube range c-t: 54.1 - 54.6
Top tube length: 53.8 - 54.2
Stem Length: 10.7 - 11.3
BB-Saddle Position: 75.1 - 77.1
Saddle-Handlebar: 51.0 - 51.6
Saddle Setback: 3.3 - 3.7
Seatpost Type: NON-SETBACK


The Eddy Fit (cm)
-------------------------------------------
Seat tube range c-c: 53.6 - 54.1
Seat tube range c-t: 55.3 - 55.8
Top tube length: 53.8 - 54.2
Stem Length: 9.6 - 10.2
BB-Saddle Position: 74.3 - 76.3
Saddle-Handlebar: 51.8 - 52.4
Saddle Setback: 4.5 - 4.9
Seatpost Type: NON-SETBACK


The French Fit (cm)
-------------------------------------------
Seat tube range c-c: 55.3 - 55.8
Seat tube range c-t: 57.0 - 57.5
Top tube length: 55.0 - 55.4
Stem Length: 9.8 - 10.4
BB-Saddle Position: 72.6 - 74.6
Saddle-Handlebar: 53.5 - 54.1
Saddle Setback: 4.0 - 4.4
Seatpost Type: SETBACK
 

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info...

What makes these suggestions form the Competitive Cyclist website so worthless is (1) they don't list the critical dimensions of head tube length or seat tube angle and most frame sizing number these days have little to do with either of the old c-c or c-t standards.

The saddle setbacks are suggesting a very forward saddle position, but once again the large variation in saddle designs makes saddle nose suggestions quite worthless.

What you really need to look at is the head tube length, with the headset, to get the true vertical size of the frame and the combination of TT length and set tube angle to compare the reach.

In the case of the Jamis Zenith, either size could be made to fit the same. They both have the same STA, so the true difference in reach is 15mm. A 15mm difference in stem length is often difficult to come by, so it may be a toss-up whether the smaller frame uses a 10 or 20mm longer stem.

The 73 degree STA makes the reach of these frames relatively short and might require a non-setback post to produce the setback you need.

The other issue is the head tube length. I've got 2cm more inseam and would still select the smaller frame, but I have no problem tolerating a 9-10cm drop from the saddle to the bars. If you can't tolerate more than 5cm of drop, the smaller frame might require a large 30mm stack of spacers under the stem, or a flipped up stem.

You've got enough torso length for the larger frame, but with an average inseam, the vertical size of the larger frame is largest you should consider.

Now you need to figure out what your fit needs are, in order to select the frame that would have the better setup.

http://www.jamisbikes.com/usa/bikes/08_bikes/08_geo/xenith_geo.html
 

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Discussion Starter · #3 ·
Thanks for the info. I'm not sold on the Jamis, it was just one of many possibilities. My flexibility is pretty crappy now-a-days and my riding has been very limited for the last year thanks to work. With a heavy year of travel behind me though, I'm gearing up to start riding regularly again...and am building up a new bike in celebration. (eh, needed an excuse to build a new bike)

I suppose my question for you, if there is a right answer, would be what is the ideal frame geometry/size for me? I'd rather shop around for the correct frame knowing the size criteria and be able to find the best fit.
 
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