How important is frame size?
 

I'm crossing the 3,000 commuting mile mark and I'm realizing that my enthusiasm has gotten way ahead of my mechanical ability. A

lot of parts need to be replaced but before I make that jump - do i have the right frame size?

I suspect that my frame might be a bit small for me. However, formulas for the right frame size vary and its gotten more difficult to determine frame size. I'm considering getting a longer stem to compensate. I'd like to stick with the same frame but I'll switch if I'm doing something awful to my body.

What harm is there in riding a bike with a frame on the small side?

I was riding a bike w/ a too-small frame. Over the course of a year or so (~3k miles) I kept moving the seatpost up, the saddle back. Never extended the stem but did flip it to lower the bar, stretch reach that way, and then finally gave up. The stock too-small frame probably also had too-short cranks (the bike was well-enough spec'd for a person of the right size, I guess). I don't know about measurable ill effects but it just wasn't comfortable. A friend who is ~5" shorter than me has it now, loves it.

There are no real formulas to calculate correct frame size. I'm currently riding a frame that is "supposed" to be too big for me. I tried out lots of frames that were supposed to be right, and they all felt too small. See Peter White's page on bike fit; I agree with what he say: it's all about your unique body geometry, and your unique preferences and comfort.

If you are comfortable riding your current frame, then it's fine. But if you're feeling cramped and adjustments (stem etc.) don't help - get a new one.

Size isn't important, it's how you ride the bike.

(Sorry, somebody was gonna say it...)

Whether or not you feel comfortable is the main consideration for choosing a frame size.

Also, I don't recommend you pay much attention to the seat-tube length (which seems to be the standard way of measuring frame size) because

Headtube length is more significant because changing the seat-to-handlebars distance is more complicated than changing the seat-to-pedals distance.

If you don't have any pain problems while riding now, changing frame size/shape might just cause them.

hard to say - if your saddle is all the way up, stem's all the way out, and you feel like your knees are just missing your chin - probably time for a new one...

I'd say as long as you are in the ball park (within a size or so) as far as frame size you can fine/tune the reach with different stems, the height with the seatpost, and Knee position with the saddle rails and possibly a different seatpost.

I have a bike that has a top tube of 52 cm based on 2 LBS's recommendations. Don't you love it when they can just look at you and say "Hmmm, you need a small frame."? Anyways it turns out that despite my height I really need a 54 cm. Anyways I was able to adjust the bike to finally fit me. It does look a bit weird that the seat is set backwards so much but my knee pain went away and I'm able to ride the bike instead of selling it or getting a new one.

Bottom line,IMO, as long as you can adjust the bike to fit you its fine. Even if it looks too small for you.

EDIT: I also read somewhere that TDF riders purposely ride smaller bikes for reasons that escape me right now.

My road bike is about 4cm too short in the frame. (58cm, I "should" ride a 62)
I raised the seat, put a longer stem with adjustable rise, and I'm going to put a wider bar on next. It fits me comfortably enough that I did 35 miles on it last weekend and felt as if I could have done double that.

Frame size is important when considering what components to buy. Do you need a short reach drop stem, or a long reach riser? A short seatpost, or some gigantic Thompson post? I think that within 2-3cm of the "correct" frame size, and you should be OK with just some minor adjustments.

Out of curiosity, how tall are you? I'm 6'1 and I'm thinking that I need around a 58-60cm, though I haven't yet tested this theory.

I'm 6'6". My dad (who owned the bike previous to me) is 6'1", so I think a 58 should work for you.

Formulas don't work really well.

Here's the site I like: http://spokesetc.com/page.cfm?pageID=35

Doesn't give formulas, but it gives a step-by-step guide to getting htings set up correctly. Within reason, you can always get the seat set up right (unless the frame is waaaay too small and you don't have enough post in the tube). The question then is what kind of a stem you'd have to get to have good posture for the frame you have. If it's too awkward, a new frame could be better.

Getting the right frame depends on the relative lengths of your arms, legs, torso, etc. You defininitely can't use those guides that have you measure your inseam and guess your size if you want an optimal fit. If you've put 3000 miles on your current ride the fit can't be *too* horrible (is it?), and I don't imagine any table or formula will get you closer.

Hmm I'm 5'11" and I ride 58 cm road bikes. My 06 Trek 520 my old 90 trek 1400 that I commute on and my good Iron Horse Victory road bike are all 58's.
They all fit, all be it differently. The two Treks give me a comfy slightly more upright posture. The IHV has a 1cm longer top tube and a 130 stem so I have a lower stretched out position, a bit more aggressive.

Frame sizing formulas will not give you an exact frame size, because one bike company's 54cm is another's 56cm, or 55cm for a third company (I'm 5'9" with a 32.5" inseam, and I usually end up riding 54-55cm frames, but with the sizing some companies use, I end up riding 52-53cm's instead). All the formulas are good for is getting you into the ballpark that you should be looking into. The best way to determine size is to get fitted in person with a professional or at your LBS.

Thanks for all the advice!

I don't have any pains that I can't attribute to simpler changes. I have some knee pain at the moment but thats only developed in the past month and I'm fairly certain that I need to adjust my shoes. (I've played a ton of soccer and my feet turn outward more than is healthy when cycling. but i'll figure it out in time) My ass gets a bit sore but thats probably a seat problem and completely common with all cyclists.

I might stop by my LBS and see if they can sell me on a new bike but its much more likely that i'll order a ton of parts.

I got intimidated for a bit but I'm feeling much better know. I guess its just the growing pains of going from a novice to real cyclist. The pain is an honor - in the general population, how many people make it this far?

A bunch of parts may cost more than a new bike, and if you buy a bike you get all the parts you didn't need , which can be sold or kept for when you do need them. Just something to consider.

I'm 6'3, but with long arms and shorter legs. I'd ride a 61 or 62 on a roadie...but ride a 58 in cross (Kona JTS).

Keep in mind that some bikes have higher bottom brackets, so the top tube length is the more important measure. If you're going to be slowing down and coming off the bike a lot (as in traffic lights, etc.) it's also really important to have clearance for the boys when you drop off the seat and clip out to put a foot down.

Comfort is key. I've done metrics on the JTS in about 4 hours flat, with no pain or other issues. It feels a tad cramped when i stand to push up a hill, but that won't lead me to change the frame -- only perhaps go for a slightly longer stem.

Do you get any pain when you ride?

Here has been my experience with fit. I bairly clear the bar standing over my old Fugi touring commuter . I have been playing with fit all over and maybe this bike is just to big for me. I am 6 feet tall, but have a 30 inseam, so short legs, tall torso. The bike is big, 60+, but I really like it. Upgrading to 44 handlebar, my sholders are broad, seemed to help shoulder pain, going with Look pedals, rather than SPD, has helped foot pain. Now it is the lower back and neck that are sore the day after. Currently the seat sems correct and I have the bars a bit lower than the seat, maybe an inch. During my 24mile commute I move between hoods, drops, and top of bars. My arms are bent, I feel comforatable while riding, I have had mixed success trying to find the perfect fit. I can say do one adjustment at a time, and make them fairly small. There does come a point when you wonder if the frame is just too big or small. Good luck.:)

I'm 6'7" and I've found over years of experimenting that the top tube length is most important to me for getting the correct size frame. I've actually ridden a 59cm framed bike for an extended length of time with no pain anywhere....but it had a 60cm top tube! Right now all of my bikes are in the 64-66cm seat tube length and 60-65cm top tube length and they all fit me superbly.

My .02 worth? "standover" height should leave you about 1" for safety's sake :) , and your top tube length should be long enough to keep you comfortably stretched out, but not "reaching" too far....you'll know if you are.....

here is my experience... I bought a bike a year ago based on the sizing recommendations off of ebay...
the bike is nice but I extended the stem (because I like a more upright riding style than the default) and have enjoyed the bike for a year... about 2 months ago, I purchased a used trek 1220 that was too big for me (based on a comment by my LBS...). I did have to shorten up the stem and I did also extend it as well but I have enjoyed riding that bike... I recently went back to the original bike and took it for a spin... boy did the setup seem "cramped" and I seemed to have more weight on my hands so they got numb, etc...

so, based on that, I agree with you...

I bought the recommended size from Trek and the frame ended up too small. Like others, I raised the seat, and handlebars. It's an OK ride, but when making sharp turns, I have to clip-out otherwise my foot hits the fender.

Road bike - ride the biggest size you can stand over.

MTB - Stand over the top tube and pull up the front tire 2 inches.

Give or take. :p

I have a 58cm frame. I had to get a longer seat post to get proper leg extension. I had buyer’s remorse kicking myself because the bike was too small. Then I looked at the specs on the bike for various sizes and realized that the top tube length, stem length, were the same between the 58 and 62cm frames but the angles were different and after putting it on CAD it was clear that the reach on the 62cm frame was actually shorter than the 58cm frame!

Bottom line: Frame size is a starting point not an end all in bike fit.

I wouldn't want to be more than 2cm off of my "ideal" size.

I'm 6'4" and primarily look for bikes in the 62/63 range, although I've owned 60's. There's not much bigger than that so I don't have much choice.

Every now and then I see a custom "tall" bike, but they're generally MUCH bigger.

I'm 6'2" with a 32" inseam (long torso). My bikes run to larger frame sizes. The smallest is 58cm with a longer stem. The biggest comfortable bike is 63cm with a 100mm stem. I built a 64cm frame up with a 120mm stem. It's big and the stretches me out some - but it has caused pain/numbness in my hands. If I keep the bike I'll have to substitute a stem/handlebar combination that is adjustable so I can shorten the reach and raise the bar level.