# How do you know if your frame is to small or big



## Dmayner (Jul 4, 2010)

I recently bought a road bike and the shop insisted that I buy a 50cm (medium), but everything I have read since suggests that I should be on a 54cm. Needless to say I am a bit confused. So what would be signs that my frame is to small. So far the only discomfort I am having is a bit of shoulder tightness but I am only riding around 10-15 miles a day. Any help here would be greatly appreciated. Oh, I am about 5' 9" and have an inseam between 31" and 32". Thanks again.


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## frpax (Feb 13, 2010)

how is the 50cm measured? Actual seat tube length? Actual top tube? Virtual? What brand is it?

54 sounds like it might be at the tall end of your range... a 53 or maybe a 52 might be better.


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## PJ352 (Dec 5, 2007)

Dmayner said:


> I recently bought a road bike and the shop insisted that I buy a 50cm (medium), but everything I have read since suggests that I should be on a 54cm. Needless to say I am a bit confused. *So what would be signs that my frame is to small*. So far the only discomfort I am having is a bit of shoulder tightness but I am only riding around 10-15 miles a day. Any help here would be greatly appreciated. Oh, I am about 5' 9" and have an inseam between 31" and 32". Thanks again.


There are no industry standards of measuring to determine frame size, so it's essentially a label affixed to your frame with a number on it. Chances are another brand/ model with that same number wouldn't measure the same. 

As far as criteria used for determining a riders sizing requirements - proportions, fitness/ flexibility, cycling experience and personal preferences (among other factors) matter more than height or inseam alone. 

To answer the bolded question, a common sign of a frame sized too small for a given rider would be a cramped cockpit with the fitter resorting to long stems (generally speaking, longer than 120mm) and adjusting the saddle far back on the rails. The more saddle time a rider puts in, the more likely fit deficiencies will crop up, so if a bike is sized incorrectly, the rider is apt to experience some level of discomfort.


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## Jay Strongbow (May 8, 2010)

As an example of what the first two posts say: I'm 5' 8" and ride, comfortably, what Storck calls a 47. Yes, that's not a typo, 47. It's effective top tube is 52 and fraction.

Basically not enough info given to say much and sizing info over the interweb isn't a good idea either but I wouldn't be concerned based on comparing what a certain maker calls a 50 and what you read you should take for a size alone. 

It's not uncommon for what's called a 50 by a certain maker to have a effective top tube of 52ish and 52 can be a good size for a 5 9 person. 

Not that anyone would be able to determine anything definitively over the net but if you could list the specific bike or better yet a picture of you on the bike in the position you ride in it woudl allow for a better guess.


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## Dmayner (Jul 4, 2010)

Wow! What great forum. Thanks for all the helpful responses. Here are the answers to the questions that were asked: It is a Fuji Newest 1.0 (2009 which is the same as 2010). The seat tube is extended 6.75" (17cm) measured to the seat rails. Here are the specs from the fuji website I hope you can make sense of them:
Description XS(42cm)	S(46cm)	M(50cm)	L(54cm)	XL(58cm)
A SEAT TUBE- CENTER TO TOP 420.0 460.0 500.0 540.0 580.0
C-2 EFFECTIVE TOP TUBE LENGTH 510.0 530.0 545.0 565.0 590.0
D CHAIN STAY 420.0 420.0 420.0 420.0 420.0
E BB DROP 71.1 71.1 71.1 71.1 71.1
F FORK OFFSET 45.0 45.0 45.0 45.0 45.0
G HEAD TUBE ANGLE 71.0 71.5 72.5 73.0 73.0
H SEAT TUBE ANGLE 76.0 74.5 73.5 73.0 73.0
I WHEEL BASE 993.1 996.6 994.0 1004.4 1029.3
J STAND OVER HEIGHT 710.9 739.4 773.7 795.3 831.4
HEAD TUBE LENGTH 105.0 126.0 156.0 161.0 197.0
REACH 379.5 375.8 376.0 390.0 404.0
STACK 512.0 535.6 565.9 572.5 607.0
TRAIL 69.5 63.2 60.0 57.0 56.9
STEM LENGTH 90.0 90.0 100.0 100.0 110.0
STEM ANGLE ADJ ADJ ADJ ADJ ADJ
HANDLEBAR WIDTH 400.0 420.0 420.0 440.0 440.0
HANDLEBAR RISE NA NA NA NA NA
CRANK LENGTH 170.0 170.0 175.0 175.0 175.0
TOE CLIP SIZE S S M L L
SEAT POST DIAMETER 27.2 27.2 27.2 27.2 27.2

Thanks again for all the help. BTW I did try the 54cm but felt a little "long" when I was griping behind the shifters, but I had been ridding a mountain bike all spring which may have affected how I felt. Oh, I don't know if this will matter or not but the top of my seat and my handlebars both measure 39" from the floor. And at present my seat is clamped in the middle of the rails. Anyways thanks again for all the advice.


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## PJ352 (Dec 5, 2007)

Your bikes geo is an example of just how insignificant the frame size is. If you notice, the effective top tube of their 50cm bike is 545mm's. If you compare that to some Trek, C'dale and Specialized models (to name but three) you'll see that it's closer to their 54cm bikes. Generally speaking, since the ETT is a good indicator of a bikes reach, it's_ one of _the key measurements used by fitters to size a rider, not frame size. 

One indicator that the bike is sized correctly for you is that the saddle is positioned in the center of the rails. This, of course, assumes the fitter used reliable methods of measuring to get you there, but since we're critiquing over the web and unless you want to measure your KOPS, it's as good as it gets. 

From everything you've offered thus far, I personally think it's likely that you're on the right sized bike, but if you want to check one other thing, measure your stem length from center of top cap bolt to center of bars, running parallel with the stem.


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## indysteel (Jul 21, 2006)

PJ352,

I'm curious as to your comment that a good way to judge whether a bike is the right size is the position of the saddle on the rails. That's just incorrect IMO. The seat post angle, seatpost offset, the length of the rider's femur relative to their overall leg length, the length of the rails and individual preference, a saddle can be positioned just about anywhere along the rails (so long as it's within the particular saddle's specs). The fact that a saddle is pushed all the way forward or back may be an indication that a bike is too big or too small, but it is by no means determinative. 

A lot of smaller frames, for instance, have steeper STAs, which ofte require a rider to push their saddle back as far as it will go and/or use a seatpost with a fair amount of setback. I know, because I have just such a bike. Even with the saddle positioned all the way back, I still run a 100 mm stem, so it did no throw off my reach so much that I have to compensate for it with an overly short stem.


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## PJ352 (Dec 5, 2007)

indysteel said:


> PJ352,
> 
> I'm curious as to your comment that a good way to judge whether a bike is the right size is the position of the saddle on the rails. That's just incorrect IMO. The seat post angle, seatpost offset, the length of the rider's femur relative to their overall leg length, the length of the rails and individual preference, a saddle can be positioned just about anywhere along the rails (so long as it's within the particular saddle's specs). The fact that a saddle is pushed all the way forward or back may be an indication that a bike is too big or too small, but it is by no means determinative.
> 
> A lot of smaller frames, for instance, have steeper STAs, which ofte require a rider to push their saddle back as far as it will go and/or use a seatpost with a fair amount of setback. I know, because I have just such a bike. Even with the saddle positioned all the way back, I still run a 100 mm stem, so it did no throw off my reach so much that I have to compensate for it with an overly short stem.


You need to reread what I wrote. I didn't say _a good way to judge whether a bike is the right size is the position of the saddle on the rails_ nor did I say it was determinative. What I said was that it's_ one indicator _that the bike is sized correctly, and it is. Like KOPS (which it directly relates to) it's not an end all be all, but some fitters use the fore/ aft saddle adjustment in an attempt to correct reach deficiencies, which is incorrect. That said, I generally agree with your first paragraph.

Regarding the second paragraph, given what you've offered about your bike set up, I probably wouldn't have opted for that particular geo for myself. I take a smaller frame and have had bikes with steeper (relatively speaking) STA's and they don't work that well for me because of my preferred KOPS position.

I think in your case the geo (or that particular frame size) set the stage for you having to make an unnecessary compromise in order to correctly fit the bike to you. If you're happy and comfortable riding, that's certainly the bottom line, but there may have been better choices available to you.


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## Dmayner (Jul 4, 2010)

PJ352,

Thanks for the reply. It put my mind at ease about the frame. Concerning the seat position, it was not specifically positioned for me. It just happened to be where it was. In either case it seems to be comfortable for me. I now have two questions for you: what is KOPS and what exactly do you want me to measure? In other words what stem and bolt are you referring to? Thanks


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## PJ352 (Dec 5, 2007)

Dmayner said:


> PJ352,
> 
> Thanks for the reply. It put my mind at ease about the frame. Concerning the seat position, it was not specifically positioned for me. It just happened to be where it was. In either case it seems to be comfortable for me. I now have two questions for you: what is KOPS and what exactly do you want me to measure? In other words what stem and bolt are you referring to? Thanks


KOPS is knee over pedal spindle. It's easy to measure, and since your bike wasn't set up specifically for you, I think it would be good for you to measure. Even if the position is working for you, by measuring you'll have a reference point if it's ever needed.

Here's a diagram - to measure, first make sure your bike is on a level surface. With your pedals at the 3 and 9 position, using a weighted string (a plumb bob) drop it from the front (bottom) of your knee cap, down (where the dotted line appears in the diagram). It's easier if you have a helper to measure the distance from where the string rests to the pedal spindle (plus or minus). 
View attachment 204539


To measure the handlebar stem, measure from the center of the handlebars to the bolt in the center of the top cap.


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## PJ352 (Dec 5, 2007)

Dmayner said:


> PJ352,
> 
> Thanks for the reply. It put my mind at ease about the frame. Concerning the seat position, it was not specifically positioned for me. It just happened to be where it was. In either case it seems to be comfortable for me. I now have two questions for you: what is KOPS and what exactly do you want me to measure? In other words *what stem and bolt are you referring to? *Thanks


Here's a pic of how to measure the stem length. Ignore the curved handlebars. For reference, in this pic the stem measures about 4.75 inches, or 120mm's.
View attachment 204540


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## Dmayner (Jul 4, 2010)

PJ352,

Thanks for the very clear explanations and diagrams Here are my results:
Stem to bar = 3.5"
KOPS = 2.5" - 2.75" (I would slip forward in my seat a bit)

Thanks again for all the time and help


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## PJ352 (Dec 5, 2007)

Dmayner said:


> PJ352,
> 
> Thanks for the very clear explanations and diagrams Here are my results:
> Stem to bar = 3.5"
> ...


If you measured your stem correctly it's a 90mm. On the short side, but fine.

Is that KOPS measurement a plus or minus. In other words, did the string fall in front of the pedal (towards the front of the bike) or behind (towards the rear).

Also, pls explain the bolded statement.


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## Dmayner (Jul 4, 2010)

For the KOPS, the string fell in front of the pedal or towards the front of the bike. So far as the bolded statement, I think my seat must be tilt a little down in front so I had a tendency to slide forward in my seat. In other words I wasn't able to maintain my riding position consistently and that is why I posted 1/4" difference.


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## PJ352 (Dec 5, 2007)

Dmayner said:


> For the KOPS, the string fell in front of the pedal or towards the front of the bike. So far as the bolded statement, *I think my seat must be tilt a little down in front* so I had a tendency to slide forward in my seat. In other words I wasn't able to maintain my riding position consistently and that is why I posted 1/4" difference.



You can check your saddle using a level or straight edge. They have to be placed carefully atop the saddle, taking into consideration the contours of your saddle, but done with care you'll get a reliable result, especially if you recheck a few times. Usually placing either in the center running lengthwise works best. No matter the method used, make sure the bike is level. If you use a straight edge place it as stated, running parallel with the top tube, then measure two or three points from ground to straight edge (example: Front of saddle, the mid point between saddle and stem, then near stem). 

Re: KOPS. If measured correctly, you're 6-7cm's ahead of the pedal spindle. If you're comfortable with that position and feel that it works well for you, leave it. FWIW if you're rails are clamped at the center of the saddle rails you may not be able to adjust to KOPS (no plus or minus).


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## Dmayner (Jul 4, 2010)

PJ352,

First thanks for all your time and thoughts. You have been very helpful. Second, based on all the info I have provide do you think I have the right size frame? What would you say is the ideal KOPS and stem to bar length? What are the pros and cons in the KOPS? Should I be considering any adjustments?


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## PJ352 (Dec 5, 2007)

Dmayner said:


> PJ352,
> 
> First thanks for all your time and thoughts. You have been very helpful. Second, based on all the info I have provide do you think I have the right size frame? What would you say is the ideal KOPS and stem to bar length? What are the pros and cons in the KOPS? Should I be considering any adjustments?


Without knowing how you're proportioned or seeing you on your bike, it's difficult to say if you've been correctly sized. Given the fairly slack STA it seems odd that you're 6-7 cm's ahead of pedal spindle _along_ with running a 90mm stem. That would normally be a sign that without making those adjustments reach would be excessive for you, indicating the frame may be too large, but you mentioned that you've been fitted and are relatively comfortable on your bike. 

As far as the ideal KOPS and stem length, there are some generally held beliefs, but no hard and fast rules. And really, what a good fit comes down to is little more than a rider feeling like his/ her position feels right, the bike is handling predictably and they're performing as they would expect - and in relative comfort.

I'm not sure what you mean by pros and cons of KOPS, but generally speaking moving forward of KOPS will predominantly use quad muscles which theoretically helps sprinters, while adjusting rearward uses hamstrings. Going too far back can make a rider over reach through part of the pedal stroke and (in turn) stretch the IT band - a common injury in cyclists.

Another aspect of KOPS (or fore/ aft saddle position) is that adjusting it forward or back shifts a riders weight forward or back _slightly_. So (as an example) if you were complaining of hand pain/ numbness, I'd suggest moving the saddle rearward a few mm's. IME many riders are set up with fore/ aft set too far forward, causing incorrect f/r weight distribution. 

Your call on making any adjustments. If anything, I would suggest checking that your saddle is level, because if it's tilted front down you'll find yourself pushing back to maintain a proper position and this can lead to fit issues. If you decide to reset KOPS, I would suggest rechecking your current position to ensure you know the correct starting point.


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## gardenrunner (Jul 25, 2009)

Off subject-

PJ I have similar FSA carbon handlebars to those in your photo. Does it bother you that the flat of the bar isn't taped? I was debating on taping the flat, but I really only put my hands up there if I'm taking a break(eat, drink, trying not to barf). Plus, I'd cover the cool logo on them. Not that I'd care, but my frame is also blank so it looks kinda stealth. Have you ever had them taped and didn't like it? Thoughts?


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## PJ352 (Dec 5, 2007)

gardenrunner said:


> Off subject-
> 
> PJ I have similar FSA carbon handlebars to those in your photo. Does it bother you that the flat of the bar isn't taped? I was debating on taping the flat, but I really only put my hands up there if I'm taking a break(eat, drink, trying not to barf). Plus, I'd cover the cool logo on them. Not that I'd care, but my frame is also blank so it looks kinda stealth. Have you ever had them taped and didn't like it? Thoughts?


To set the record straight, that pic isn't of my bike. I just used it as a point of reference. Coincidentally, my bars also have (sorta) flat tops, so to answer your question, even though I ride about 90% in the drops I tape the bars because doing so quells some road buzz/ harshness. On longer rides (IMO) a degree of comfort trumps aesthetics, but if you seldom position your hands at the tops, YMMV.


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