Road Cycling - What does "fit" really mean?

I'm in the market for a new bike and of course the No. 1 piece of advice is to make sure to get a bike that "fits." This makes perfect sense to me, but other than the basic fit of frame size, I don't get what "fit" really means.

I know a good LBS can adjust stem length, crank length, saddle height and position, etc. to match my size, but is this "fit"? Or is it more of a zen mind-meld thing, like, I should get on a showroom bike zip around for a few minutes on a test ride and go "Yup, that's the one for me, no doubt about it!" To me, a test ride seems inadequate for knowing how a bike will feel once you've had it for a while.

The only bike I've looked at so far that I was sure didn't fit me was a LeMond, and that was because I felt the top tube was too uncomofortably long (of course, even then it's conceivable that the showroom bike may have had a stem on it that was too long for me). I feel like I 've made this whole fit thing much more complicated than it is.

You are onto something.

Fitting can be a long and complex process.

"Fit" means how well your bike conforms to your body proportions, flexibility and style of riding. Since everyone's body proportions, etc., are different, everyone's bike will fit differently.

In terms of proportions, there are two principal metrics for bike fit -- seattube height and toptube length. These should approximate your leg length [a ratio of your inseam length] and reach [the horizontal distance from your hands to your pelvis while sitting comfortably on the bike]. There are other metrics as well -- handlebar/shoulder width, saddle position [relative to the crank] -- but those can be tinkered with.

The goal of that part of fitting is to find a bike that you can sit and ride on comfortably and pedal with the greatest biomechanical efficiency without causing injury.

However, different bike designs have different geometric properties. The angle of the headtube and seattube may be steeper or slacker, giving you a sense of greater responsiveness/twitchiness or stability/sluggishness. As you can see, this is very subjective. Also, you'll find that different bike designs have different toptube lengths relative to seatube height. Lemonds typically have long TTs, while Treks typically have short TTs. You'll find that you usually prefer one more than the other, and you'll find that criterium racers tend to prefer steep-angled, shorter TT bikes, while long-distanxce riders will prefer moree relaxed angles with a longer TT.

My road bike is a 50 cm with a 53 cm TT.

The problem is that there is no way to say which metric is more important than the other. I have a long back, so I tend to like a longer TT than a shorter one. My cyclocross bike, counterintuitively to cyclocross, is a 52 cm bike, but it has a 53 cm TT. I really wanted that length.

The reason why a fitting can take so long -- with a tape measure, a fit kit and a whole lot of bikes -- is that, once you get past the hard metrics like TT length and ST height, which geometry combinations you actually prefer is a very personal and subjective thing. I have a buddy who turned down an almost-never-used Colnago C40 [full record, nucleon wheels] for $2500 because, although the height fit him fine, he likes a much longer, Lemond-ian top-tube, and Colnagos have relatively short top tubes.

Hope this all made sense.

Thanks, velocipedio. So should a good bike shop take those measurements before suggesting bikes, also taking into account what type of riding I'll be doing, etc?

Your right, that the way to achieve a good fit, given a frame of roughly the correct size and shape , to to play around with the size and shapes of the components, until the points of contact (saddle, pedals, bars) fall where you want them to be.
If you dont already ride a bike lots, you probably dont know where to put the points of contact, so you use some standard measures, which should feel OK for the average rider.
Once you have a good setup, its possible to replicate the points of contact on other frames, even if the frame is not an exact match.
There are other aspects of bike geometry (steering, wheelbase)which dont affect the points of contact, but may affect the general handling. These do not come under the remit of "fit"

The top tube on my new Fuji Roubaix-Pro felt way too long when I first bought it. I went through severe buyer's remorse for awhile, thinking I had bought too large a frame.

Now, having ridden the bike about 10 miles every day for the past two months, the reach feels good.

As part of my adjustment process, I tried out an 80mm stem in place of the stock 100mm and was miserable on it. I felt way too scrunched up and couldn't wait to get home and put the stock stem back on.

What's even more surprising is that the reach now feels a little SHORT sometimes, as if I could stretch out more, particularly in the drops.

Bottom line: I think my 58cm frame size is correct, given the 2cm increments it comes in. A 56 would be too small; a 60 probably too large. My seat post now sticks out a little less than 5 inches from the seat tube. Whatever.

Even though I test rode the bike, I'm glad I didn't reject it because the reach felt too long.

condor