Frame-sizing discussion
 

I've rode bikes all my life but only recently in the past year have I obsessed about them. Once one gets past all the superfluous stuff, it becomes abundantly clear that size and fit ought to be the paramount concerns when buying a new frame. I've learned the hard way over the past year as I have struggled to get a proper fit on my 62cm Mark V without breaking the bank (on stems, forks, seatposts, etc).

Now the purpose of this thread is to discuss frame-sizing. The pro's and con's of sizing up, sizing down, of square sizing, of longer top-tubes, longer-seatposts, of heat-tube and seat-tube angles, etc.

What I want to get out of this thread is a better understanding of critical points for intervention when fitting a frame and the process that has let many of you to finding the perfect fit. I know alot of it is trial-and-error, but there are very concrete strategies for dialing down a bike so that riding is a pleasure rather than frustration.

To start, my first question is about square frame sizing versus not. What are the benefits of a square-sized frame, if any, and why isn't it popular to build frames in this manner?

If no one is interested mods can delete this thread.

I'm interested.

While I don't have too much to add to this thread, I could show you this article by Dave Moulton.

As of recent, I found out my torso is actually quite short and I discovered that many bikes "recommended" for my height are way too large for me. I am about 5'9" with an inseam length of 87.5cm, or 34.5", which makes my torso small in comparison.

In my opinion, If you're in between size, it is the best to size down as you can fix the issue with a longer post, stem, more spacers and such.

Does my current frame fit me? No, but I make it work with a really short stem and it works for me.

I bought a bike that was too big, then I bought a bike that was too small. Finally I bought one that was juuuust right.

I assume it's your Mash? That saddle-to-bar drop is exactly the think that bugs me about my IRO's geometry. It has a 59cm toptube and a 56cm headtube. And since I got my IRO prebuilt, the fork was already cut too short and thus I have a horrible saddle-to-bar drop. I dunno why it seems that many frames are sized in this way rather than having a square type geometry (i.e., 59cm top-tube AND 59cm seat-tube). True, all can be adjusted for with longer steertubes, shorter stems, higher stem angles, etcs. But to me, that's inelegant.

In my theory as to why many steel fixed gear frames are made this way is because they want to avoid toe overlap.

Most all of the bikes I see do have that square geo, or they have longer top-tubes (Leader, Dodici). If you want to have zero drop you don't want a track bike. Get a Rivendell or a cruiser or a hybrid, or just a bunch of spacers. btw, you're getting top-tube and head-tube confused. Top tube length also isn't the only thing that determines your drop. For example, my Mash has a 590mm ST and a 550MM TT. Add in a short head tube and you have more drop and the forward sloping geo. If the head tube was longer you could have zero drop and the top-tube would be even shorter.

I think your premise is a little off. One is not better than another, it's what's suited to the rider's ride posture, style and intended use. It's all a compromise, the question is which compromises suit you? If you don't rotate your pelvis, you will likely prefer a shorter top tube and not much drop. If you are an aero pro rider, you probably riding an elongated top tube and deep drop And on and on. Once you get past basic comfort and handling, "proper" fit is about how you intend to ride and your expectations.

One of my favorite bikes has a 56cm tt and 60cm st. Old skool geometry and a blast to ride, but very 'wrong' for many reasons depending on the criteria. What's yours?

I might have misstated what I was trying to say. I wasn't trying to confuse the two, but you are right, head-tube is what matters for saddle-to-bar drop.

wat.

I meant seat-tube