for example a 55cm and a 57cm


is the frame longer? taller?


is there a big difference inbetween the two sizes

Depends on the mgf. A 55cm in one bike brand can be different from a different brand 55cm. All the geometries have a roll in different frame sizes. The size listed is the seat tube measurement. This will vary from maker to maker as some measure center of bottom bracket to center to top tube, and others measure center of bottom bracket to top to seat tube. This will usually be specified in the makers geometries charts - some times not and you will need to contact the maker to find out. However, top tube length is really the most important measurement when choosing a frame size. And, a 55cm frame in one maker can have a 55cm top tube and another maker can have a 56cm top tube. The geometry charts really need to be paid attention to.

Generally speaking, the 57 is longer and taller.

Yes, it's a big difference. Like the difference between size 10 and size 11 shoes.

...and just like its a bad idea to buy shoes without trying them on or at least knowing your size, the same goes for bikes.

Ah, I see what he was asking now. Man, I read into that waaaay too much.

Hahaha! Your answer is great...but just probably more than he needed right now

I can generally ride 52-56" frames. Even rode a 58cm Giant roadie with an 80cm stem and just a couple inches of seatpost showing one day, not a bad ride at all, but bars were kinda high for my taste- fully fredly 1" or so above saddle. Would probably suck if both feet came off pedals while straddling top tube tho

On my 52cm I have 130mm stem, respectable saddle to bar drop and short wheelbase. Makes cornering fun

https://www.cyclesmercier.com/geometry_tt.html

Depends on manufacturer & year of geometry.
I ride anywhere for a 44 to a 53. Stand over and TT length seems to factor in more for me than anything else, plus it also depends on what I am doing with it. Road bikes can have tighter SO clearance than mountain can.

im a 56cm but got a 55cm. do you think that would make a big difference?

Respectfully...you guys are idiots.


I can put my feet in size 14 shoes and walk around in them. That doesn't mean they fit.

Bikes come in 2cm increments for a reason. Some bikes (like high-end BMCs) come in 1cm increments. If manufacturers could get away with a one-size-fits-most approach, they would do that...but they don't.

Not sure.

What does make a difference is whether you use proper capitalization and punctuation. We are (at least I am) judging you by how you represent yourself with your posts.

we'll im 5'10-5'11 and can't make up my mind between a 55cm or 57cm

FITMENT QUESTION?





>>>FITMENT CALCULATOR<<<


That will help you make up your mind.

Seriously, take the time and do the fit calculator. You will then know if a 55cm or 57cm is right for you.

Like everyone said, it totally depends on the frame.

You can check on the fitment calculator, but I don't put too much worth into it. And not sure why people recommend it. It is setup for road bikes, assuming you will be using drops, and your default position is the hoods. Also, the ranges are pretty wide.

Go to a shop a ride a few bikes. You need to get an idea of what kind of top tube you like to ride. 55cm and 57cm means nothing. What kind of bike is it? Is it a 55cm with a 56.8 top tube? Or is it a 55cm with a 55cm top tube? These would be 2 completely different bikes.

Hmmmm.....37 years of bike riding and I still don't understand fit & SO & frame geometry. Thanks for schooling me on things. Looks like I need new bikes, mine don't fit me correctly. Damn. My bad.

Meh, you ride your bikes, I'll ride mine. I just know I can ride any 54cm square, horiz. TT road frame and most 52s and most 56s and be perfectly happy, assuming good stem, bar, brake hood choice.

joking sarcasm aside(like I wouldn't take any excuse to buy new bikes! come on

Exhibit A:
The last pic is at standing height to show you there are indeed, 2 bikes in the pics.


Pink bike:
1987 Lotus Elite 600 Triathlon bike 44cm. 24" front tire, 700c back.
Black bike:
2003 Quintana Roo Kilo(not TT....lol!) 53cm. 650c F&R.
both have standovers of 28" both TT are 19.5" long. Both fit me the same, but my seat on the Lotus is a tad lower since I want to keep it stock and I am at minimum insertion.

Decade & manufacturer DO matter. a 14 shoe isn't always a 14 shoe.

This means that the manufacturers listed the sizes inconsistently, not that you are able to comfortably ride two different sizes that are 9cm apart

Saying, "I ride anywhere for a 44 to a 53." implies that you can ride a 44cm - 53cm frame from the same product line. That's what threw me off. That's like me saying I can ride a 52, 54, 56, 58, & 60cm Bianchi Pista. That's absurd.

Inconsistent sizing is a problem in the cycling world. For a relavent example, the "60cm" Trek T1 SSFG bike fits like a standard 58cm and that +2cm size listing extends down the size run ("58cm" fits like a 56cm etc...). This is very confusing for consumers.

BMC is TERRIBLE about it. It's a long story, but their size labels have not much to do with the actual TT length.

I get you.
I did say in my first sentence of that original post AND in my pic post, that manufacturer & year of geometry matter.
I wasn't talking about the exact same bike by the exact same producer either. And I honestly don't think these bikes are 9cm apart. To me, they are damn near identical size & fit wise.
What I mean is that you cannot just say "oh, I ride a 53cm" and just sight unseen(and geometry numbers unchecked) buy your bikes stock and have them all fit the same.

I think we agree on this one, it isn't your body that can handle huge size differences in frames, it is how they are measured and ride that make they the right fit.