AJW2W11E

Hello, I am relatively new to bicycling . I ride a Bianchi Pista SS and a Giant Tough Road . Both are Large frame size . I feel like they fit well .
I measure 5 foot 9 1/2 inches at the doctors with my Nikes on so they say I am 5 10”. I may be actually 5 9.
I am about to buy another Bike. What am I missing by not choosing Frame Size M. Would Medium optimize my energy?
Thank you in Advance

Koyote

There are too many variables involved to give a reliable answer over the internet. You should buy your next bike from a good shop that will do a proper fitting.

phughes

No one can answer than for you, without knowing what bike you are considering, and what your objectives are. When I bought my current touring bike, I went with the larger of two frame sizes the bike came in, because I wanted to keep my bars level, or slightly about the seat, without having to use a lot of spacers. If I wanted the bars lower, the smaller frame would have been the better option. That is just one criteria that can go into frame size choice.

So what kind of bike are you considering, or even better, what specific bike? Bike sizes vary from manufacturer to manufacturer. What will you use it for?

grizzly59

Lookup using a book and a tape measure against a wall to get your true bicycling inseam length. And look at the specs for the length of the crank arms that come with each size. Just your height in shoes isn't a great measure for picking a bike. You should try both sizes hands on if you can.

cyclic_eric

I'm also 5'10" and frequently find myself in the same quandary. There's a trade off I believe.
The smaller frames feel a bit quicker, more nimble, better for shorter rides. The larger ones feel big, stable, and comfortable for longer distances.
You really need to have several bikes ready for each scenario.

icemilkcoffee 

Whichever is in stock.

shelbyfv

What does the mfg suggest for the bike you are looking at? I think most would recommend a Medium or 54cm for 5'9". That's assuming normal proportions.

70sSanO

Ha ha. I actually did that in 1986. I’m just under 5’9”, probably closer to 5’8” these days, and they didn’t have 54cm so I bought the 56cm. Four years later, a shop was blowing out frames and they didn’t have a 54cm, so once again I got a 56cm.

​​​So far so good!

John

chaadster

If you’re between sizes, always go smaller. No question…but I guess that’s not the question.

To the question, generally speaking, 5’9” sure sounds like a Medium size frame.

Maelochs

You can stretch a small frame with a long seat post, setback, a longer stem, longer reach bars .... you can make a frame smaller with a saw and glue.

You choose.

chaadster

Haha! Yep.

Koyote

Bad advice.

Paul Barnard

There can be a substantial amount of variability between one manufacturer's medium and another's. Same with large. Assuming you cannot try before you buy, you'll have to know the dimensions of a bike that works for you, and examine that against the dimension of the bike you are interested in. If you can try first, you should. Some manufacturers make a ML, so keep that in mind as well.

veganbikes

Test ride the bike that you want in both sizes and see which one feels best for you. Talk with a knowledgeable salesperson and maybe ask for recommendations as well but really it is all about your fit on whatever bike you want. Nobody on the internet can really determine much for you other than what you have told us which is very little but even if you had said I want to buy the Bike Co. BikeMaster and provided a link it would still be tough because we don't know much about your fitment to that bike only you and your fitter would really know, maybe the sales person or some shop employee with fitting knowledge. It all really comes down to you and your feelings on the bike.

If you know what you want and have some fitting issues or just want something that really fits you might consider talking with a custom builder and a fitter and really get something dialed in to you not just to the general mass public. Nothing wrong with a stock bike necessarily but a custom fit bike could be just the ticket if you know you enjoy riding and want a real upgrade.

Camilo

Here's the trade off and, IMHO the major decision criterion: head tube length and how high or low you want your handlebars.

There's a lot of range for saddle height and even a decent amount for setback. There's a lot of range for stem length too. So seat tube and top tube length and seat tube angle can be adjusted for quite a bit. But there's not a lot of range - either up or down - for stem height, given any stem angle. Maybe 40 mm either way (35 - 40 mm is generally the maximum spacer height under any stem).

In general, given a specific model of frame, aside from seat tube and top tube length differnces, the larger frame will have a longer head tube vs. the smaller frame. So if you're challenged to get the bars high enough for your fit and comfort, you should opt for the larger frame. If you dont have that issue and/or really need your bars as low as possible, go with the smaller one.

If you're in the middle, ride both and just feel which feels better. The smaller one might be a a little lighter and quicker feeling, the larger one, maybe more stable.

My experience is that I need my handlebars higher and opt for larger frame with a shorter stem and less saddle extension, if presented with two that might work OK. Others, especially younger and stronger, more flexible riders, would have the opposite opinion.

CAT7RDR

Veganbikes is spot on.

Pay more now and reap the benefits for a lifetime.

PeteHski

I disagree. It depends on your riding goals and the specific bike in question. At 6' tall I'm often in between a large and medium frame and usually go with large. Why? Because I'm primarily an endurance rider and prefer the inevitably longer wheelbase and higher stack of a larger frame size. If I was racing crits I may well choose to size down for a more aggressive position with slammed, super-long stem. But that's not how I want to ride all day.

But I totally agree at 5'9" I can't think of many Large frames that would work well. I would have thought the OP was a medium without much question.

Calsun

Go with the size frame that fits you best regardles of the label on the bike. Some have medium and medium-large and large and others have different amounts of reach depending on the intended use of the bike and so there are categories of bikes being sold by Trek and Specialized and other companies. It is more complicated than in the past when everything was based on the length of the seat tube.

You posture and riding position is what is important and if you cannot extend your arms properly or feel scrunched up or need to stretch to reach the controls on the handlebar then this should govern your selection and not some chart.

livedarklions

M and L are entirely too vague to answer the question as is 5'9". If it felt right being on the bike, it's probably right sized. I'm shorter than you are and rode several thousand very comfortable miles on a L frame FX 3.

livedarklions

I think if you look at the geometry of the Tough Road he's talking about, it's more than possible a large frame could work for him.

bruce19

People can ride frames in a range of sizes. I have a 32.5" inseam and am 5'9" tall. I ride 54-56. Optimal for me is a 55 with a 55 TT measured virtually. This is often referred to as a "square 55."

AndreyT

Nothing will "optimize your energy". You are "relatively new to bicycling", as you stated it yourself. The concept of "optimizing your energy" does not apply to you in any way, shape or form. And it won't apply for a very, very, very long time. Possibly never, especially considering that on such an early stage you are already focusing on such woefully irrelevant things.

Even if you'll seriously get yourself involved into cycling, you'll eventually find out that there's no other way of really "optimizing your energy" than riding a lot of different bikes and finding the ones that work for you. And in many cases this synergy will not follow formal logic.

As for now, don't attempt to "optimize your energy". Get a bike that fits in a sense that it doesn't do more harm than good.

rumrunn6

good luck
fastest 17 mile commute was on an old mtb w/ big fat slicks, that was too small for me
have a hybrid that is too large for me but feels quite comfortable
current mtb is correct size, feels good
current road bike is correct size, feels good

Kapusta

It is impossible to say whether you should be on a M are L. On some models you may fit a M better, on others a L.

Going to a M may mean a better fit, or it may be too small.

DaveSSS 

To the OP. I'd go by your leg length, not just your height. A lot of riders of your height have shorter legs than I do, being 3-4 inches shorter. The medium size is meaningless. In some brands, I ride a 50 or 52 and others it's S or XS. Seat tube lengths are also meaningless these days, except for a minimum to make use of a common 350mm post. You should go by stack and reach. Nearly all brands list these values. Also of importance is saddle to bar drop. I use a large 10cm saddle to bar drop, so there's a limit of about 530mm on the stack, with a 72-73cm saddle height. I look for a 365 to 380mm reach. There's a lot of adjustment available with stem length and handlebar reach. If your saddle to bar drop is less, add more stack. Taller saddle height - add some more stack.