Yet Another Fit Question...
 

I'm sure fit questions have been asked 2343255 times on this forum, but I'm adding one more...

I'm looking to get a new Trek Madone, and the guys at my LBS are trying to get me onto 58cm frame. I'm 5'9" with a 32.5" inseam, and from everything I'm reading, a 56cm should be my size. I test rode both, but they each were a slightly different setup (stem size, seat post setback, headtube length).

Both bikes felt more upright than my current bike (55 cm frame with 55.5 cm top tube), which has a much shorter headtube. The 56 cm Trek felt a bit cramped, but there was room to move the saddle back, and lengthen the stem. The 58 felt ok, but there was less room to adjust shorter if I find out the position is too stretched out. The 56cm Trek is a 55.7cm top tube and the 58cm is a 57.2cm top tube.

Perhaps I should just go with the 58, as that felt a little better as it was setup at the shop, but almost everything I read (and comparing to my current bike), the 56cm more closely matches what I "should" be riding. (I also did the Competetive Cyclist Fit Calculator, which gave me an average top tube length of around 54-55cm.) I think the main difference is how much longer the headtube is on the Trek. Being more upright makes it feel less stretched out (I might have had the wrong setup on my current bike).

Advice???

LBS employees typically do try to fit you on the larger end of frame sizes. I'm not exactly sure why, but they do seem to be alarmed by a lot of seatpost sticking out. For your average rec cyclist, they're probably looking for a more relaxed fit.

have them make necessary adj to the 56 and try it again for a fair comparision - tell them what you are thinking and reading its a lot of money for you and them

If you're happy with the way your current bike fits I would try to get as close to that as possible. When I did my fit we measured me and my old bike before we came up with the solution. I didn't ride any of them because the weather was really just too crappy.

My old bike (a 56cm 1991 Specialized Sirrus) had never given me any problems and I went in fully expecting to get another 56cm bike. After looking it all over though we came up with a 58cm Performance fit with a 100mm stem as being my best option. It really all came down to inseam length. The way the Madones are set up I would have had a heck of a saddle to bar drop with a 56 or end up with a bunch of spacers that I didn't want. All in all, I'm happy with the setup though I may try out a slightly shorter stem.

I went against my gut feeling ordering the 58 over the 56 but I'm glad I did, maybe you could go to another shop for a second opinion if you're really concerned. Truth be told however, you should be able to get a good fit on either of them. But I understand, your spending the money, you want it perfect.

And, never missing a chance to post a pic of my new bike...
http://lh3.ggpht.com/_jKcGFdmcEfk/S2...00/madone3.jpg

Most shops I've been to have typically steered me toward the larger frame under the assumption the average customer wants a more relaxed fit rather than something aggressive which they would probably find uncomfortable. If you're current set up is what you like and are comfortable with then express that to them so you get the bike you want and not the one they want to sell you. Typically the smaller frame will have a shorter headtube and allow for more saddle to bar drop so see if the bike you like mirrors your current set up.

Incidentally, the saddle should be positioned relative to the bottom bracket (well, I use a pedal anyway) and not in relation to the bars.

I'm a 58 and I'm 5' 11 3/4" and wear 34" or 32" pants depending on the style. I do use a fair amount of seat post however.

Your pant inseam shouldn't be used to determine the inseam measurement required for a bike fit.

These. And some bike fit tips.

58 sounds too big, OP. I am 6'0" with a 35.4" PBH and I ride a 56.

A few of you have pointed out that shops will lead customers more toward a larger frame under the assumption we will want a more relaxed fit. I'm not sure how a larger frame is more relaxed. Can you explain that?

When I test rode a 58 cm Madone with a Pro Fit setup, I felt I was way too stretched out and somewhat more bent over (I know the Pro Fit is about 3 cm lower on the headtube). It was definitely too big. When I test rode the Performance Fit bikes (the "style" I'm looking for), they were more upright (both a 58 and 56). On the Performance Fit, a 56 felt a bit cramped, and the 58 felt ok, but in my mind I felt I was still riding too big a bike for my size.

I think I'm overanalyzing this for a 17mm difference in top tube length and 20mm in seat tube... My current bike is not exactly the most comfortable ride, so I probably won't go wrong with either, making the exact fit better with seatmast and stem choice, and saddle position...

All of the "fit systems" have me on a 54cm bike (at least one with a 54cm TT). I'm 5'7". I much prefer a bike with a 51cm TT. I feel way too stretched out on a 54. Even with a 52 I use a very short stem (75mm) and short reach bars.

Everyone is different. You have to decide which bike size is comfortable. Get educated and go from there.

I'm 6'0'' and ride a 58cm Madone. It fits me pretty well. I would think you'd be better suited on a 56cm as well. I think either would have been fine for me. If I check any of the various fit calculators online I come up at 57cm. I don't think you'll be too far off on either, as you can adjust the stem and saddle, but I think the 56 would probably be the better starting point.

What about first getting a proper bike fit, if not at the shop with the Trek, than an LBS that specializes in fitting. Opinion varies, but I see a proper fit being done initially without a specific bike (e.g. on a fit bike, like Serrottas). Once you know the ideal seat height and saddle setback, you can than look at the stem and handlebar height for reach.

While you can continue to have adjustments made between the 56 & 58 at the shop, I'm thinking at some point you'll just say yes to one of them and may regret it later.

Fit is so important...

Way too big, even in the pro fit model. You didn't mention what model or what fit (pro or performance). I've got the same inseam, but I'm shorter. I'd pick a 54cm in the pro fit, for the 120mm head tube, but the reach is a bit long. For someone of your height it should be perfect. If you can't tolerate much saddle to bar drop, then the performance fit in a 54cm should be the right size. The 30mm jump in HTL is too much for me.

Here's some education. A TT length without a STA to go with it does not mean much. You need both to define the frame reach. Steeper STAs add reach - about 8.5mm per degree in this frame size range. A shorter TT with a steeper STA can be just as long in reach as a frame with a longer TT.

I'm just 1cm shorter than you, but I've got no problem with a 53cm TT, 74.5 degree STA, 110mm stem and short reach bars, with the saddle tip set 6-7cm behind the BB. I also use an 11cm drop from the saddle to the bars.

Ok, here's more specifics...

I'm running 8cm saddle to bar drop.
Bike A: 52cm TT, 74.5 STA, 75mm stem, short reach bars.
Bike B: 51.5cm TT, 74 STA, 75mm stem, short reach bars.

Saddle tip is apprx 4cm behind BB.

Bike B is more comfortable for me than Bike A.

How's that?

I happen to like a very compact cockpit, you'd probably feel squished. We're all built differently, it's important to find what fits you and not some idealized person of your height.

^^^

I agree completely. I just hate it when people mention TT length instead of reach. It's easy to buy a frame with a shorter TT, thinking it has a shorter reach and later find out that it does not, due to a steeper STA.

In your case, bike B has about 9mm less reach.

Yup, that's why it's more comfortable.