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still confused on frame size

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still confused on frame size

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Old 03-27-08, 04:41 PM
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bmogie
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still confused on frame size

I'm looking into buying my first bike to do triathlons. I can only spend about $500, so I'm looking at used bikes and probably can't buy one at a LBS. I've read hundreds of posts about determining the proper frame size. I know it's best to go to a LBS to get sized. I simply may have to buy online though, so I'd like a best guess at a frame size. So far I've had someone measure me and gone to competitive cyclist - I'll put my results below. I understand that top tube length is the most important to look at, but that you need to take more than that into account in determining the best fit (and that really you should ride a bike to see how it feels).

The recommended top tube length is 53.2-53.6. Does that mean I should be looking at 54 frames? I'm 5'10.5" with a 33" inseam - seems like maybe I should be looking at a 56. Any help would be greatly appreciated.

Measurements
-------------------------------------------
Inseam: 84
Trunk: 63
Forearm: 33
Arm: 65.5
Thigh: 60.5
Lower Leg: 54.5
Sternal Notch: 145
Total Body Height: 179


The Competitive Fit (cm)
-------------------------------------------
Seat tube range c-c: 54.4 - 54.9
Seat tube range c-t: 56.1 - 56.6
Top tube length: 53.2 - 53.6
Stem Length: 10.9 - 11.5
BB-Saddle Position: 71.9 - 73.9
Saddle-Handlebar: 52.0 - 52.6
Saddle Setback: 5.5 - 5.9
Seatpost Type: NON-SETBACK
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Old 03-27-08, 04:44 PM
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Do you have long legs? 53 cm is a little on the low side.

And unfortunately, bikes are sized by seat tube length, the least important factor. So yes, you should look at 54's, but for 53 cm TT, you're probably looking for a 52 cm bike or a 54 and a short stem.
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Old 03-27-08, 05:01 PM
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There is no standard as to what 54 actually means. Different manufacturers measure the seat tube from different places (go figure). And with that, the top tube lengths vary quite a bit for a bike of the same "size", even if they measure the seat tube the same.

Most manufacturers have a specification page that will show all of the frame dimensions. I would start there when I found a bike I was interested in.

One thing if you are looking for a tri bike, the geometry is a little different. I don't know how that should change the measurements you got.
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Old 03-27-08, 05:58 PM
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So I'm not a total idiot for being confused then. I wish there was a standard for what a "size 54" actually is. I've tried looking for manufacture specs, but they're hard to find on some bikes. Adding aero bars for tri racing will probably confuse things even more.
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Old 03-27-08, 06:12 PM
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gurana
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I'm on my blackberry, so it's difficult for me to throw links up, but you most definitely shouldn't feel bad about being confused. The thing is, I don't think a standard of measuring would help too much. If all manufacturers measured seat tube c-c, a bike's size really is dependant on pretty much all facets of its geometry: ht, st angle, tt angle, bb drop (I'm still not too sure what that even means)...

What you need, or at least what I was able to conclude for myself in going through the RS2 group buy, are measuring factors that essentially convert the figures you are given into something that approximates 'universal'. In the RS2 gb thread, someone posted info on fitting for a bike based on 'reach and stack'. You should check it out and make your own decision, but it is what I used. Unfortunately, I won't be able to tell you for how that ended up working out for me... The frame won't be here for another few weeks, and who knows when I'll be able to actually build it up....

Good luck
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Old 03-27-08, 09:03 PM
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I'm 5'10" with a 31" inseam and ride a Trek 54. I would think a 56 would fit you perfectly.
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