I am building up a new bike for my wife and got a good deal on a Tarmac SL3 in size 54. But now I am having some doubts about weather the size is right. My wife is 172 cm high and has her saddle 72,5 cm up (midle of bb to sadle). According to Specialized size 54 is for heights of 168 to 175, which puts her spot on a size 54. But looking at how most people set up their Tarmac they usually go one size smaller.

What would you recommend?

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Bring the mountains to Denmark!!

Too big IMO. I'm 178cm and I ride a 52! But that's because I prefer a longer stem and the shorter head tube. If your wife appreciates the longer head tube and doesn't mind a slightly twitchier ride, all is good

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It isn't going to be easy, but it's going to be worth it.

I am 1.80 and ride a 54 with seatback and 110mm stem, fits perfectly.
Too big for her, maybe 50 would be rhe right size


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Too big. 52cm max.

I have the same BB to Top of saddle height. I would ride a 52.

She would be more comfortable on womens geo as well.

i rode a sl3 s works size 54, with a saddle height of 730mm, so no i dont think its wrong at all...

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http://weightweenies.starbike.com/forum/viewtopic.php?f=10&t=100739

im 178cm, i ride a 54cm with a 120mm stem, but my saddle height is 723mm, legs are a bit short. hell, i prefer some brands' 56cm. i usually go for a 5cm bar drop, nothing too drastic...
i think a lot of folks try to fit on bikes that are too small, driven by "pro" setups and their "fashion forward" lack-of-logic. but that's another topic...
so id go for the 54.

I'm 180cm and ride a 56 with 120mm stem, 770mm of saddle to BB, and about 120mm of saddle to bar drop. Saddle to bar drop may seem extreme but I've long arms, so my posture isn't uncomfortably flat.

Women generally have longer legs (ratio) than men so it may not be as simple as height.

A bike fitting would help but if could always try different stem lengths (if you've a few laying about), bars with a different reach, different seatposts, and different stack heights.

not that it makes any difference but im 170cm, ride 170mm cranks, have 703mm top of saddle to bb, ride a 20mm offset saddle, 115mm stem -10 deg stem, on a 52cm tarmac sl3 s-works

often mentioned, but mostly disproved now. however, they do have shorter arms for a given height, which would require the shorter reach and less drop that is often seen...

Not disproved at all. Its entirely true, while their legs may be the same length, their torso is indeed shorter. Like he said... Its a ratio based size.

disproved, again.
from Active.com, i believe, a quote from a well regarded book. also, specialized and cervelo fit studies back it up.

(bold by me)

I mentioned 'generally' as there are concrete cross-cultural differences and socio-economic factors involved in sexually dimorphic leg-to-body ratios (LBR).

I'm not familiar with the book you mentioned nor the US military anthropometric data source. I'd suggest that the US military data is not representative of the male/female population. For instance, women represent about 13.4 percent of the active Army, 23.7 percent of the Army Reserve and 14.0 percent of the Army National Guard (2009). We know that women are aprrox 50% of world population.

I'm unsure if the data is from 1977 or more recently 1996 (based on a 1988 dataset). If we use the 1988 dataset of males (n=5103) and females (n=3446) women of heights 72-78" are not accepted whereas males are. This invalidates the dataset.

Another example...the US military are trying to fit people into their military hardware cockpits, uniforms, body armour etc. and would select according to these specific criteria. Their sample is not representative. MC ANSUR recognises this when they state "There are no statistically valid anthropometric data representative of the current USMC population for design and sizing of ICE. " (http://nsrdec.natick.army.mil/MC-ANSUR/index.htm).

And just to muddy things further there isn't a standardised measurement in use. For instance, in a 1995 document, (p. 26 http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA316646&Location=U2&doc=GetTRDoc.pdf) height could Acrimonial Height (floor to shoulder) or Cervicale Height (floor to cervicale). Leg length is variously measured as Crotch Height, Buttock Height, and Functional Leg Length. I've no idea of which measurements the authour of your book mentioned and the statistical method he used to analyse the data as no LBR is provided in doc I linked.

Height is also measured differently in different disciplines (ie. some include foot length and others exclude the neck/head).

Interestingly, there are numerous studies that show females with a higher LBR (in western cultures) are seen as more attractive, that might explain my bias! But the semi-nomadic Himba people of Namibia see women with low LBR, and men with higher LBR, as attractive.

So er, to the OP, measure your wife, the other data is inconclusive

*edited urls

I'm 186cm and I hesitated between 56 and 58cm SL3, and finally took 58cm with 90mm stem - feel very comfortable with it.