The knee-jerk reaction when looking into buying your first road bike might be to hit the Google app where you’ll end up at the Bike Frame Size Calculator. You’ll put in your height (6′), then stick a book in between your legs, tight against your crotch and measure from the floor to the spine and type in that measurement (34″). You’ll then be redirected to a new page that will give you your “ideal” frame size (59 cm or 23″ in my case). You’ll also be given your ideal crank arm length (mine shows 175 but that’s not correct, it’s 172.5 – we’ll get to that in a bit). In addition, you’ll also be given several other sizes to consider (57-61 cm in my case). Easy as pie, right? Not quite.
You’ll also have to deal with a lot of internet/pro chatter about buying a smaller bike. For instance, Mark Cavendish is 5’8″ tall which should mean a 54 cm frame for him but he rides either a 52 cm or 49 cm Venge depending on his mood. You’ll no doubt read about many other pros who ride bikes several sizes smaller than their height would suggest is plausible (according to the calculator). Look at Jen’s Voigt as well (click on “Specifications”). He’s 6’3″ tall and rides a 60 cm Madone 7 Series. According to the calculator he should be on a 62 cm frame. Now for my Venge… It’s a 56 cm frame but we were looking at a 54 initially because I made it known that I wanted as much speed as possible… It was my choice to go with the 56 – I split the difference between the right sized 58 and the smaller 54.
The first thing you should know about the bike size calculator is that it’s a guide.
The trick with picking the right frame size is choosing between comfort (larger frame) and speed (smaller) or if you’re lucky, you’ll get both as I did. The smaller frame size gets your butt up in the air and your hands down low so the cyclist can cut into the wind with his or her head and shoulders, not their chest. In other words, the smaller frames are all about aerodynamics. Now, many in the industry claim that riding like that is less comfortable but I haven’t found that to be the case. Conversely, having ridden both upright and as shown above, I am infinitely more comfortable riding low.
We’re not quite out of the woods yet though. A smaller frame should mean better handling as well, that is cornering and climbing. The larger bike should descend better because it’ll be what is described as a little less “twitchy“.
All of that taken into account, when picking a road bike a choice must be made: Stick with the proper size and ride a little more upright and comfortably or go low with a smaller frame and for aerodynamics and responsiveness. Or go for both. Just know this up front, if you do go small, there’s a very likely chance that you’ll need a longer stem to make the cockpit reach work. The frame style will matter as well. It’s quite easy to tell the two main types apart (there are several, but let’s keep this as simple as possible), you’ve got the traditional which is signified by a top tube that is parallel to the ground and a compact frame which has a sloped top tube:
It is my understanding that choosing the traditional frame limits the size selection quite a bit because the geometry is different (this is according to the owner of my local shop who has decades of experience in frame building, including a 24 hour world record bike). The compact frames are favored by manufacturers because they don’t need so many frame sizes but they also work to the cyclist’s advantage. For instance, I actually have a 54 cm traditional frame bike (see my bike page, scroll to the bottom) that happens way too small to ride comfortably at my height, yet we were seriously considering a 54 cm Venge which would have been seriously aerodynamic but would have limited me in my later years when I’m a little less flexible… In the end, I went with a 56 because I was thinking of my later years. I’m flexible enough now that I can have a fairly aggressive position on my bike (almost as much as Cav but not Jens). It also helps that when my shop built my bike they left quite a bit of room for spacers. Right now it looks a little off-putting having two large spacers stacked on top of my stem, but fifteen years from now when I’m not so concerned with speed I’ll be able to raise the stem up to account for a little bit of decreased flexibility.
So, I’m 777 words into this post, quite a few for what should be something fairly simple… You’re “this” tall and you have “this” amount of reach, you get “this” size frame. Right? Well yes, but there’s a bit more to it depending on how far you want to go. When I got into cycling, I did like most noobs do: I found a bike I wanted and I bought it before thinking it through. Then I had to buy another bike that fit me. The Venge, my third road bike was the first one that I really paid attention to what I’d need, not only right now but in the future as well.
The setup on my traditional 58 cm Trek and 56 cm Venge are almost identical but the simple truth is, the Venge is a lot more comfortable because it’s just a bit smaller and it fits how I want to ride perfectly. In my case, where I spend between five and six thousand miles a year worth of time on the saddle, it made a lot of sense to pay close attention to what I want. After all, that works out to about 330 hours give or take, we’re not talking about a couple of rides up to the market once a week. Where this gets difficult is knowing what you want before you lay down the cash. Having had a bike that was too small, one that was the correct size by the book and one that is slightly smaller, I’ll be erring to the smaller side from now on because smaller suits my riding style and small is a little more versatile.
UPDATE: My word, all that and I forgot about crank arm length… The calculator said I should be rolling with a 175 mm crank arm length but my in-shop fitting clearly showed 172.5. I tried a number of scenarios on the calculator to make a 172.5 show up but nothing worked, it popped out either 170 or 175… Again, the calculator is a guide, not the law. Use it at your own risk.