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Old 03-27-08, 04:42 PM   #1
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, 04:49 PM   #2
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At 5'10", 33 inseam...a 56 is probably correct for a road bike...you may want to size down if you're looking at a tri/tt bike.

I'm 5'8", 30 inseam and my road bike is a 54 but my tri bike is a 51.

EDIT - Maybe this will help.

I'm pretty sure that my Roadie (2003 Specialized Allez Pro) has a 54.8 top tube and my tri bike (2006 Cervelo P2 SL) has a 53.5 top tube at 75 deg that really works out to 51 if you use the forward seat tube angle (78 deg).
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Old 03-27-08, 07:07 PM   #3
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I think you're in the right direction as well with a 56. A 54 may work as well.

For instance I am 5'8", with a 31.33 inseam and ride a 52 road bike witha 53.5 top tube. I also ride a 53.5cm tri bike thats probably 1.5cm too long for me.
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Old 03-29-08, 09:05 AM   #4
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[QUOTE=cjbruin;6416970]At 5'10", 33 inseam...a 56 is probably correct for a road bike...you may want to size down if you're looking at a tri/tt bike.
QUOTE]

If you are looking in the $500 range you are probably going to get a road bike. My advice is to not size down. If you decide that triathlon is not for you or you decide it is for you and you get a dedicated tri bike you can always turn it back into a road bike. If you size down you are going to have a very uncomfortable ride when using it as a road bike. A 56 sounds like it will do you just fine but remember a 56 with one bike manufacturer can end up being a 58 or 54 with another. Good luck and welcome to the sport!
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Old 03-29-08, 09:37 AM   #5
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This is helpful - thanks guys. One more question. If I'm going to add aero bars, would that influence the size bike I should get, as opposed to if I was just getting a road bike to ride as a road bike? Seems like in the aero position I might be more stretched out. I've seen sizes 55 and 57 too, so I'm just wondering 1. would those work period if I should be looking at a 56, and 2. if I'm adding aero bars, would smaller (55, 56) be better than larger (57)?
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Old 03-29-08, 12:37 PM   #6
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That was why I commented on possibly sizing down. In general, once you add aero bars, a normal road frame will stretch you out to much...unless you get a forward facing seat post. You could also go with "shorty" bar extensions.

There really are several options.
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