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The Noob’s Guide to Bike Sizing: Does Size REALLY Matter?


March 2014

I’ve made a lot of mistakes when it comes to buying bikes and components, all of them early in cycling because I didn’t trust the owner of my local bike shop to shoot me a straight deal.  Put simply, this prejudice, based on the assumption that the guys at the shop would try to oversell me, led to a lot of costly errors.  The problem here is that there are shortcuts around certain “principles” involved in cycling – if you’re willing to make certain sacrifices.

My Cannondale, while I do enjoy it now, is a very good example.  I bought that bike through Craigslist because I made the assumption that I couldn’t afford to get a bike through the local shop.  According to the bike frame size calculator, at 6’0″ my ideal frame size is 58 cm but I can fit on anything from a 56 to a 59.  The Cannondale was advertised as a 56, so I should have been just fine…  Unfortunately, the size sticker had been removed and either the previous owner was mistaken or Cannondale measured their bikes differently back then, but the bike is a 54.  It also has 170 mm crank arms, and a stem that was about 60 mm too short (at least for a guy my height).  On the non-size related side, the old girl had down tube shifters and I bought a saddle with enough padding on it to choke a horse (it came without one).  The saddle, a Serfas e-Gel was another dumb noob mistake.  A great saddle for putting around for five or ten miles, yes, but riding 15 miles a day and 30-40 on the weekends, not so much.

With a little work and a lot of effort I got that little thing up to a 20 mph average, sure enough.  This was not easy but, humorously enough, because I didn’t know any better I didn’t think it was such a big deal.  Of course now that I have two properly sized road bikes with excellent saddles, it’s easy to compare riding the Cannondale to torture – or if you’re squeamish that way you could call it self-flagellation.

I’ve been back on the Cannondale (my “nasty roads” bike) for two days in a row now after riding my 5200 or Venge for two years and I’m here to tell you, I can feel the difference, just in the crank arm length.  I’ve got a 172.5 mm crank arms on both…  A difference of just 2.5 millimeters and I feel like I’m short-stroking every time around on the C’dale.  On the road it feels like I’m pedaling a kids bike.

A lot of the other issues have since been fixed:  I did some math and figured out I needed a 110 mm stem and bought that, I bought a decent Specialized Riva saddle (padded to accommodate the aluminum frame’s rigidity, but not over-done) a couple of months ago and have the setup very close to my Venge – in other words, with a little cash I could manipulate the bike so I could fit on it.  With mistake purchases and some money into fitting my old wheels from the Venge, I’ve got probably $700 into the Cannondale.  Unfortunately, if I’d have just gone to the shop in the first place, I’d have been able to get the 5200 (used) for only $50 more and had a properly sized bike – and with modern shifters and a 9-spd. drivetrain instead of a 7-sp.

So, this is the tough part of being a noob enthusiast.  Size does matter and in my case, I was too ignorant and in too much of a hurry to learn how to avoid the mistakes from the web.  I needed human help – and the funny thing, over the last three seasons:  I’ve learned just enough to be dangerous.  Fortunately, I have a much better relationship with my local shop owner so he’s saved me a lot of expensive headaches.

So, to my enthusiastic noob friends, if you take away anything from this post, please take this:  The more you plan on riding a bike, the more size matters.  If you’re just going to putt about for five or ten miles mistakes aren’t as costly.  If, on the other hand, you find yourself falling in love with cycling and the miles start racking up, millimeters matter and getting it right the first time, saves a lot of headaches, butt-aches and cash over the long run.

This ties back to my initial mistake:  Assuming that the owner of the shop was just trying to make an extra buck off of me while steering my in the right direction.  Many of his fixes to my problems were more expensive which exacerbated my incorrect assumption.  The reality was that he just wanted things done right the first time which is, often, more costly in the short-term.  Unfortunately, had I just stuck with him to begin with I’d have saved $2 for every dollar I eventually spent.



  1. brettday says:

    Notes taken, and will be applied when purchasing my nextbike. Thanks for the guide

  2. sxeveganbiking says:

    I had a play about with this calculator today… …and made a couple of adjustments as far as I could with the frame I bought. I’m 6′ and the frame is 56cm BB to top of ST, not 56cm BB to centre TT, but the standover height is ok. The only trouble with the calculator is that is says my TT is too short and there’s not much I can do about that. Although, being a relative newbie to road, the TT/reach still feels long to me as I’m still adjusting to the lower position of road.

    • bgddyjim says:

      If the reach feels too far, and I’ve dealt with this myself on my 5200 (by about 4 cm), generally you just need a shorter stem – assuming you’re in a good position over the pedals. My Cannondale measures exactly like your bike – 56 cm to the top of the ST. We are the same height and I’m in an ideal position on mine so I have to believe it’s possible to get you there on yours. I’ve been through enough fittings to know what my pro looks for so I managed my C’dale on my own and am quite happy with what I’ve done.

      On the other hand, my Venge is a true 56 cm with a sloping top tube and is VASTLY more comfortable to ride – it is, right down to the crank arm length, perfectly fitted to me.

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