flats

Let's say I currently ride a 56 cm frame. If I find a killer deal on a 54, couldn't I buy it and then make up the frame size difference with changes in stem length and seat post height and/or setback?

This is hypothetical. I'm just curious how much the frame size matters for a good fit. Obviously a 52 and a 62 are quite different. But a couple of centimeters?

Thanks.

halfspeed

It depends upon the 56 and the 54. "Frame size" on its own doesn't necessarily mean a whole lot.

fstshrk

I ride a 56cm Roubaix. I also ride a 55cm Jamis Aurora. And I have test ridden a 54cm Roubaix. They all fit fine. Just watch for the effective top tube length and head tube height.
You don't want to end up with a goofy stem to compensate for the reduced head tube height in the 54.

giro_man

In theory, as you say, it is possible to fit 2 frame sizes. Depending on the respective geometries, you might expect one size to require greater adjustment than the other. I have 2 Cervelo bikes, a size 48 and a size 51. Placement of the handlebars requires the size 51 to have no spacers and a -10 degree stem that is 110 mm in length. Correspondingly, the size 48 Cervelo has 20 mm of spacers and a -6 degree stem that is 120 mm in length.

pgjackson

Yes. Get the killer deal. You can fit pretty easily one-up or one-down. When you look at it closely, the difference between a 52 and a 54 is about 1/2 of an inch. If you feel best on a 54, you can easily fit on a 52 or a 56. Bikes are built to be adjustable. Too many people here get all wrapped around the axel on having a specific, perfectly sized bike..like anything off by 2cm will cause horrible bodily harm or something. I started out on a 54, found a KILLER deal on a 56 and got it. Bought a shorter stem for $20 and I was riding in the exact same position I was before. Then I upgraded and found a killer deal on a 52. Put a longer stem on it and everything is great.

If you are looking for a new bike, don't pass up a great deal because it isn't what you think is the perfect size.

hamster

I used to ride a motorcycle in addition to the bicycle.

When you're buying a sportbike, do you know how many choices of the frame size you normally get? Exactly one (1), also known as "take it or leave it". On a motorcycle, you don't need to pedal but other considerations, like aerodynamics, handling, etc. are pretty much the same.

Eventually I grew resigned to the fact that I can't put my feet flat on the ground at the same time on any sportbike in production, because they all had seat heights at least a couple of inches higher than my leg length, and said heights were not adjustable in any way. At stoplights, I had to lean the bike and touch the ground on the outside with my toes. (This, by the way, is a somewhat bigger problem on a motorcycle, because even the lightest sportbike weighs ~450 lbs including gasoline and battery, and lifting a dropped bike is hard, not to mention embarrassing.)

Compared to that, worries about having to find a "perfect" bicycle frame size among 8-10 options seem laughable.

evan938

+1. i rode a 56cm CAAD8 all year, and just bought a 54cm supersix. both fit me fine, and both are stock form.

benajah

Frame geometry matters a lot more than frame size, in the sense that a 54 Madone may be too big and a 54 CAAD10 may be just right, or whatever....but the general rule of thumb is that it's easier to make a small frame bigger than a big frame smaller.
Don't go too small though.

Sixty Fiver

When you get fitted for a bike the fitter should be able to give you a narrow range of frame sizes that will fit you... most have expressed this here that they can ride frames that might vary 2-4 cm between them and this is the usual range you would get from a fitter.

I ride currently ride 53-55.5 cm frames.

grolby

Ugh. I'm going to disagree a bit with others here. Fit matters. A lot. Obviously, there is some wiggle room, but how much depends upon the bike and on your body. If you are on a bike that doesn't fit right, you absolutely will pay for it in some level of performance, either in handling or putting power to the pedals. Enough to bother you? I don't know, maybe not. I will say that there's a lot more you can do if the frame is a little small for you. That's usually fine. End up on a bike that's too big and, trust me, you're basically screwed. You can get it to work well enough, and I did this with a too-big frame for years. But you won't live up to the bike's potential or your potential on it. My advice would be: unless you really know what you're doing (and if you have to ask, you probably don't), why take a chance? If you get a screaming deal on a bike that doesn't really work for you, that's not actually much of a deal, is it?

marqueemoon

Totally depends on the setup of your current bike and how you like a bike to fit and handle.

If you're running a slammed -17 100mm stem on your current bike with a fistful of zero setback post, yes you could probably size down and make it work. If you're running a 130 stem with 40mm of spacers and your saddle slammed back on a sky high mega-setback post the next size down is going to be too small.

datlas 

I suggest you familiarize yourself with "reach" and "stack," makes it much easier to compare.

Of course, the correct answer to your query is "it depends."

Sixty Fiver

A proper fit is crucial and we're not talking about too big or too small but rather, a smaller range of variance in frame sizing between bicycles.

DaveSSS 

As others have noted, pay attention to the reach and stack, not the frame size number. If you are comparng a single model, then the smaller size would typically have about a 20mm shorter head tube and and maybe 1cm shorter reach. If you really need the larger size with 20mm or more of spacer under the stem, then the smaller size would not be a great idea, unless you're also willing to used a flipped up stem.

StanSeven

This is a good response. Some of the posts got off track - the OP is talking about getting a size smaller than he has now. As far as performance suffering, it won't if the bike is setup right. Pro's generally ride a very small frame with a 130-140 stem and lots of seat post showing. Many also use a -17 degree stem for bikes with tall head tubes.

Between stem lengths and angles, seat posts with various setbacks, and seat post heights, there is lots of room to adjust.

vwchad

I currently have a 56cm Felt Z85 and a 58cm Scott CR-1 Team. I have found that I am generally comfortable on a 54-56cm frame, depending on the geometry of the particular frame. I got a great deal on the 58cm Scott and with a shorter stem and a few adjustments the reach and seat height is the same as my Felt. On the flats or down hill I'm fine on the Scott, but I've found that in a climb the bike starts to feel really big under me, even though, like I said, I've got it set up with a nearly identical reach and seat height as my Felt. Fit is important on a bike, but as others have already said bikes are adjustable within a certain range. I also agree that a slightly small frame is easier to fit than a slightly large frame. This has been my experience with the Scott. Ride what is comfortable. Don't just get something that is not the correct size simply because it is a good deal. I'm looking to get rid of my Scott for a bike that fits me now. Hope this helps.

pgjackson

Well, what is the "correct" size. I don't think there is one correct size...I believe there is a range of sizes that everyone fits. Generally one-up or one-down. If the OP feels most comfortable on a 54, he will be fine on a 52 or a 56. Anything bigger or smaller will most likely be very uncomfortable. If he finds a great deal and the size is in the ballpark, get it.

caloso

Concur.

carpediemracing 

There's fit and there's handling.

I can make myself fit various sized frames by using odd stems and such, but my actual correct size range is maybe +/- 1 cm in reach, +/- 1 cm in bar height. There's about a 0.5 cm saddle fore/aft range and perhaps 0.5 cm height (pedal to saddle) range.

My bar is about 0.5 cm higher than I prefer. When I went to 2.5 cm higher it was way too high.

My current bars are about as far out as I can use - I raced successfully for a season with a 1 cm shorter reach. I tried a 3 cm shorter reach bar and used a 1 cm longer stem. The 2 cm reduction in reach (i.e. 1 cm shorter than what I once used) was enough to kill the bars for me (since I nixed the idea of having another frame built just for those bars). I'm considering a track stem (I bought one already) that will result in 2 cm decreased reach and raising the bars 1 cm (instead of 2 cm as with the non-track stem). That may bring the bars into acceptable range - although the reach will be 2 cm shorter if the bars are 1 cm lower then it may be acceptable.

On handling - if you go too short a stem you end up with a lot of weight on the rear wheel and not much on the front. This will compromise handling. Having ridden bikes with stems as short as 90 mm and as long as 150 mm, when I spec'ed out a custom frame I aimed for a 120 mm stem. I can go 110 or 130 and not compromise handling too much. 140 is a bit long, 100 is a bit short, and both negatively affect how the bike handles.

cyclezen

+1
different sizes in the same model will ride and 'feel' different. There are many facets to how a bike ends up feeling under you.
Things like 'Front center' determine a lot of the balance - ie tarmac front-center varies by 8 mm (quite a bit) between 54 & 56.
HT & ST angles also affect that, even though you can/do move the seat around and change stem lengths.

That said there's no way to tell whether 'downsizing' will seem a good move - that's something you need to figure.

labels don;t mean much - a trek 58, from a a few seasons back, dimensionally feels to me like my Spec 56...

marqueemoon

I'm with carpediemracing. I've found when measuring things like reach, saddle height, and saddle to bar drop on my bikes I'm within about .5cm from one bike to the next.

120ish stem and a 58ish top tube is the sweet spot for me in the handling department. That's from 1 to 2 cm longer a stem than most complete 58cm bikes come with.

I personally wouldn't go any shorter than 57.5 or longer than 58.5 for an effective top tube. I don't like a big frame with short stem and I can't go smaller without resorting to silliness.

I think you need to know how you want a bike to fit and handle before you can really play with this stuff. When in doubt pass. Other deals will come along.

mynameistaken

If you go a size down check to see if the wheel base goes down as well. If you have big feet you might be clipping the front wheel on slow speed turns.

pgjackson

Is the OP planning on being a competitive racer? If not then the handling aspects of various frame sizes is not important. Seriously, 3/4 of an inch doesn't make that much difference.

Campag4life

I don't think you could be more wrong either about motorcycles or road bikes. I have ridden both for decades.
Every motorcycle I have ever owned I have modified for a better riding position...most extensively because I am fussy about fit. One size doesn't fit all and one doesn't have to live with any aspect of riding position...from suspension height to seat thickness to peg to saddle height...to front end height...to bar position both in pull back and height...or clipons. Motorcycles are infinitely adjustable. Most top sport bike riders have their rearsets, seats and clip on/bars custom made for a perfect fit triangle.

Similarly, the right road bike size matters. Not only size but proportion of a frame.
In the case of road bikes, the proportion of the bike affects comfort and aerodynamics and how much power you can lay down.

CenturionIM

personally I think going down is a lot better than going up. You get a lighter bike.