# Dummie question on frame size.



## jsidney (Aug 24, 2011)

I am 5 8'1/2, the pants that I wear have a 30 inch inseam, I am going to guess that translates to 31 or 32 inch legs? 

On a road bike from what I read the frame size for me would be between 54-56 cm?

Is there more to it than this?

Crank size? what do I need to do with this or can that be easily changed on a bike to fit me?

The bike I am using now is too big for me.

I am gearing up to post all of my super dumb questions soon.


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## cxwrench (Nov 9, 2004)

more like 52-53-54cm. depends on your proportions, and which brand you're looking at. i'm 5' 7.5" and i've had a 49cm BMC, a 52cm Scott, a 51cm Cervelo...
most likely you'll be on 170mm cranks. get fitted by someone that knows what they're doing...


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## jsidney (Aug 24, 2011)

cxwrench said:


> more like 52-53-54cm. depends on your proportions, and which brand you're looking at. i'm 5' 7.5" and i've had a 49cm BMC, a 52cm Scott, a 51cm Cervelo...
> most likely you'll be on 170mm cranks. get fitted by someone that knows what they're doing...


I am going to have trouble finding a place to help me with fitting. It is possible I will be traveling 100 miles or more if I end up getting a new bike and I would be making this trip on a cheap bike or on foot+trying to use the thumb, I will get fitting if that is the route I take. If I go used buying in the classified section I will have to go off of the best information I can find without the benefit of pro fitting.


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## jsidney (Aug 24, 2011)

cxwrench said:


> more like 52-53-54cm. depends on your proportions, and which brand you're looking at. i'm 5' 7.5" and i've had a 49cm BMC, a 52cm Scott, a 51cm Cervelo...
> most likely you'll be on 170mm cranks. get fitted by someone that knows what they're doing...


Seems you are probably right. I did some reading and it seems most of the people that have a 30 inch inseam on their jeans are using a 54cm.


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## ddimick (Aug 9, 2011)

Sizing varies a lot between different manufactures and models, and is only one measurement out of many for how a bike might fit you. Arm length, torso length etc. all come into play. I'm 5'10" with a 32" inseam and a 56 felt too big for me. I found a 55 that feels just right but would have probably wound up with a 54 if I hadn't.


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## bentnotbroken (Jan 19, 2006)

I know I may get flamed for this, but I have never been 'fit' for a bike and find at 5'9" with a 30" inseam I can ride anyhwere from a 54 to 58 frame. You have a lot of adjustment in stems and seat posts to dial in the fit, esp with a compact frame.


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## psycleridr (Jul 21, 2005)

jsidney said:


> I am 5 8'1/2, the pants that I wear have a 30 inch inseam, I am going to guess that translates to 31 or 32 inch legs?
> 
> On a road bike from what I read the frame size for me would be between 54-56 cm?
> 
> ...


I have similar dimensions to you and have 2 bikes (Merlin & Litespeed) and one is a 53 and the other a 54. So I would think you would be close to the same. However as someone mentioned not all manufacturers measure the same so you need to find some common measurements to be able to accurately compare different models. Takes a little work but not really difficult


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## Defisch (Oct 13, 2009)

I'm 5'8" 30" inseam riding a 52cm 5.2 Madone, had a 54cm Windsor and a 52cm Cannondale. I fit the 52cm's better.


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## Erion929 (Jun 10, 2010)

Agree with CX.....a 52-53-54 cm, depending on the manufacturer.

**


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## RoadSwag (Aug 19, 2011)

bentnotbroken said:


> I know I may get flamed for this, but I have never been 'fit' for a bike and find at 5'9" with a 30" inseam I can ride anyhwere from a 54 to 58 frame. You have a lot of adjustment in stems and seat posts to dial in the fit, esp with a compact frame.


This is very true


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## PJ352 (Dec 5, 2007)

bentnotbroken said:


> I know I may get flamed for this, but I have never been 'fit' for a bike and find at 5'9" with a 30" inseam I can ride anyhwere from a 54 to 58 frame. You have a lot of adjustment in stems and seat posts to dial in the fit, esp with a compact frame.


As has been mentioned previously, manufacturers follow no standards of measuring to determine frame size, making the number affixed to the frame somewhat arbirary (and meaningless). That given, your comment that a cyclist may find that s/he fits on frames within ~4cm frame size is accurate. 

The second part of your comment re: adjustments is where potential problems occur with f/r weight distribution, because (as examples) going large on a frame might necessitate ~70mm stem, possibly placing the rider too far rearward. 

Conversely, going small and fitting ~130mm stem may increase frontal weight, causing fit issues. And both scenarios can cause handling issues, the first resulting in sketchy steering, because of too little frontal weight. 

Also, choosing incorrectly on frame size (or more accurately, geometry) and adjusting saddle fore/ aft to compensate for reach is incorrect and (similar to above) is likely to place the rider too far forward or too far back, in relation to the pedals.

Best scenario is where a bikes overall geo is chosen to suite the riders proportions, anatomy/ flexibility, fitness level, riding style and preferences. Once correctly 'sized', all that's left is to tweak fit with minor adjustments to saddle, then stem/ spacer set up.

BTW, generally speaking, compact frames (sloping TT's) offer somewhat less standover for a given frame size, so riders proportioned shorter legs, longer torso can sometimes move up one size to accomodate their reach requirements and still maintain standover. It's not a magic bullet for sizing/ fitting.


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