The Noob’s Guide to Cycling: How You can tell if a Road Bike is too Big or Small with just a Simple Glance

I was perusing photos of miscellaneous Trek 5200’s and about 30 photos in I started doing the “right size”, “wrong size” game with the photos. At that point, I thought back on bringing my Cannondale to the bike shop for the first time and the owner just looking at it and knowing it was too small. I couldn’t believe it. “How did he know just by looking at the bike?”

I’ll start with what’s right with my bikes, then I’ll drop in some photos of the 5200’s I was looking at so you can see what I’m seeing.

First, my 5200 is perfectly sized for my height (a 58 cm standard frame – I’m 6’0″ tall [182 cm] 80mm stem) [ED – I’m updating the photo of my Trek… for 2020 I’ve done a lot to the bike:

Trek 5200 from my original post in… say, 2017, maybe `16.

As the Trek is in 2020 – I changed the stem to -17°, upgraded the saddle, put a 10 speed Shimano 105 groupset on it, upgraded the brakes and wheels (not shown, I upgraded the handlebar as well).

Ok, so here’s what you’re looking for: Look at the amount of visible seat post sticking out of the frame. That is the low-end of perfect right there. The high-end, say you were a bit taller, would be maybe a centimeter more than that unless you’re purposely buying a bike one size too small so you can peg the saddle height, throw a 120mm stem on that chica and slam it.

My Venge is exactly what I described above: One size smaller than standard but still perfectly sized for what I wanted (56 cm compact frame), 100mm stem, slammed, and the saddle height is exactly the same as the Trek (36-3/8″).  The compact frame, while tied to several over-the-top bike industry conspiracy theories having to do with throwing the customer under the bus to save a buck, is the quintessential aggressive road cyclist’s frame:

Now let’s look at too small, my Cannondale (54 cm frame standard Criterium):

Put simply, that bike is made for someone about 5’6″, or six inches shorter than I am.  Look at the seat post, I’m just shy of the safety limit mark. Look at the stem (that had to be ordered special to give me enough reach). That’s a stark example of “too small” but imagine if the standard (shorter) stem was on the bike. Imagine if the set-up was off…  What gets tricky here, is that this set-up can also be technically correct.  In fact, if I were a pro, you’d expect something like that.  I’m not, though.  In fact, I’m so not a pro that riding in that position was extremely uncomfortable – that’s too much drop.

Now let’s look at too big and a bad set-up – this is a little easier to spot:

Let’s start with a bike that has the hoods (handlebar) a couple of inches above the saddle – whoever picked that bike had absolutely no idea what they were doing (keep in mind before you fake indignation that I bought a Cannondale that was too small because I had absolutely no idea what I was doing – it happens). Folks, there’s a lot wrong with that bike set-up. Another interesting thing to look at is the handlebar. Actually, the whole bike is entirely wrong but the bar is likely rotated upwards to correct for too much reach to the hoods but in doing that, they put the drops further out of reach.  The right way to correct for this  is to simply buy a shorter stem for $30 (or so).

Here’s another example of too big:

On this one, the saddle is obviously too low but rather than contort the handlebar as was done on the previous bike, on this example they simply shortened the stem (which is the right way to do it).  For this bike, they have the drops rotated a little too far forward which causes the end of the drops to point up slightly.  They should be level to the ground, but that might be a touch too nitpicky.

Let’s look at one last telltale way to pick out a bike that doesn’t fit the rider… Look at the position of the saddle on this 5200:

If the saddle is sitting that far back on the rails (which means the saddle is too far forward), something is very wrong. I won’t comment on the pedals – although they help explain the double-stacker stem adapter. Ahem.

My friends, the purpose of this post is to help you understand, not only what can go wrong in a bike set-up but to highlight what it looks like when that happens.  While bike fitting isn’t an exact science, it’s most definitely a close science.  Normally I’d say, “close only counts in horseshoes and hand grenades, but it counts in bike set-up as well.  Many of the “bad” examples in this post aren’t even in hand grenade range.  Call them “good enough for government work” because I assume they can be ridden, by someone, but let’s not get too cocky either.

Now, if you need help figuring out what size bike you should be buying, try this post – it’s got a link to a calculator.  It’ll get you close enough – a little better than “hand grenade” and a lot better than “government work”.

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