Fit calculator and frame size question

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Fit calculator and frame size question

Postby jemima » Sun Sep 02, 2012 3:23 pm

Looking at getting my first road bike.
I punched in some figures on a fit calculator:-
Image

Now I've been to a couple of stores, and both the sales guys were a bit surprised (eyeing my height) when I mentioned an ETT of around 53-54cm.
Their thoughts just looking at me were 55/56 top tube.
So I thought, maybe I made a wrong measurement somewhere and did it again the following day. Only a mm here or there difference 2nd time.

Going on a couple of short rides on 55cm top tube frames, it felt way too stretched out.

Am I missing something here, to start off by?
Would appreciate any feedback.
jemima
 
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Joined: Thu Mar 31, 2011 11:18 am
Location: Sunny Perth

by BNA » Sun Sep 02, 2012 4:17 pm

BNA
 

Re: Fit calculator and frame size question

Postby RonK » Sun Sep 02, 2012 4:17 pm

A 56cm top tube (with a 100mm stem) is perfect for me at 182cm.
So I'd agree a size smaller would probably be the best choice for your stature.
It's more likely that the store didn't have a bike in your size.
Cycle touring blog and tour journals: whispering wheels...
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Re: Fit calculator and frame size question

Postby Nobody » Sun Sep 02, 2012 8:22 pm

jemima wrote:Looking at getting my first road bike.
I punched in some figures on a fit calculator:-
Image

Going on a couple of short rides on 55cm top tube frames, it felt way too stretched out.

Am I missing something here, to start off by?
Would appreciate any feedback.


My measurements:
Inseam: 81
Trunk: 62.5
Forearm: 33
Arm: 60.5
Thigh: 59.5
Lower Leg: 53
Sternal Notch: 138
Total Body Height: 172

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: 52.2 - 52.6
Stem Length: 9.5 - 10.1
BB-Saddle Position: 68.5 - 70.5 (69.5)
Saddle-Handlebar: 51.1 - 51.7
Saddle Setback: 6.0 - 6.4 (6.2)

Note the trunk and forearm measurements compared to yours. They specify a 52.4cm effective top tube length (ETT) for me. I have a 52.8cm. A 55.5 ETT is too big for me because I have one of them too. Even with the 52.8 I have a shorter stem than they specify. This probably has to do with the seat tube angle (STA) which increases the ETT by ~1cm for every degree. I suspect that Competitive Cyclist use either use 73 degree or 73.5 degree where I have 74.5 degree. So for me it is like having a 53.8 or 54.3cm ETT. STA is something to keep in mind when looking at bikes for sizing.
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Location: Sydney

Re: Fit calculator and frame size question

Postby jemima » Tue Sep 04, 2012 7:30 pm

Thanks for the feedback.
I will keep in mind that point about the ETT and the seat tube angle. Very helpful.
jemima
 
Posts: 52
Joined: Thu Mar 31, 2011 11:18 am
Location: Sunny Perth


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