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Fair to Say that One Fits a Range of Bike Sizes....(6 posts)

Fair to Say that One Fits a Range of Bike Sizes....peterkg
Oct 22, 2002 6:39 AM
Considering what you can do with crank length, stem, spacers, and seatpost... can't one make up for a slightly long or short top tube?
re: Fair to Say that One Fits a Range of Bike Sizes....jtolleson
Oct 22, 2002 7:05 AM
Fair within reason. I can ride between a 52-54 depending on the manufacturer.

But I also think that what you can do with a stem (the most common device swapped for adjusting fit) is somewhat overrated. Even if you aren't a Serotta sizecycle-type purist, we all have slowly learned that there is a balance/weight issue in one's fore-aft position on a bike.

Exaggerated example: I get a small 48 cm and jack the seat up, put as many spacers as I can, and put a 14+ stem on the bike. Those who claim that bike fit is only about the "three points of contact" (butt, feet, hands) fail to recognize that I've got a lot more weight over the fork, or even in front of it, plus the slow steering that comes from the really long stem.

When a woman gets sold a bike that is too big and just puts a 6cm stem on it, handling is effected (of course) but also she's probably got more weight back as well.

So, I still think that rules of thumb (such as thinking twice about buying any bike that requires you to use a stem shorter than a 9 or longer than a 12/13) is a helpful way to decide when to say "too much."
Oct 22, 2002 7:33 AM
there's another consideration frequently overlooked: How often do you ride, and -- especially -- how far do you ride at a time? If you ride a 10-mile loop three days a week as a minimal aerobics program, the issue is a lot less critical and you have a wide range of adjustability you can play with. That range narrows as you add days and miles of riding, and the discomforts of jury-rigged fit become more apparent. If you're going to ride the Furnace Creek 508 or whatever, it becomes a relatively huge issue.

To answer the question sensibly, you have to ask where on that continuum the potential rider lies. My brother-in-law, who faithfully puts in 30 miles a week, is far less concerned with the subtleties of fit than I am, and that's as it should be. A too-short stem isn't going to affect him one way or another. A too-short stem would, on a double century, leave me in serious discomfort.

Potential 'average recreational' or 'minimal fitness' riders probably don't last long on this board, but they do show up here asking their newbie questions occasionally, and the exacting discussions of fit probably scare them off. Sometimes I want to tell them: Just get a damn bike that more or less fits you and ride it, and not an expensive one either. In time, you'll discover through experience what needs to be tweaked in the way of fit, and you'll be in much better position to buy a 'real' bike.

Or maybe you won't ever need to.
How do you define "slightly" ?filtersweep
Oct 22, 2002 7:23 AM
I think the answer is to find the BEST frame size- which will arguably still not be absolutely "perfect" and adjust from there. I don't think that with the relatively standard practice of building frames in 2cm increments, someone would "fit" a "range" of frames unless they were "exactly" sized between the two available frames.
re: Fair to Say that One Fits a Range of Bike Sizes....tarwheel
Oct 22, 2002 8:19 AM
As others stated, it depends a lot on how much you ride. When I was an occasional biker, my size 57 frame seemed to fit just fine. When I increased my mileage a lot, I began to suspect the fit wasn't right. I now ride a 56 frame with a shorter top tube and I am much more comfortable riding longer miles and more frequently.

Personally, I think 1 cm can make a lot of difference in proper fit. That's one reason why I can't seem to find a US bike that fits me right -- most of them come in 2 cm increments, and they're either 1 cm too long or short for me. It's also harder to make a slightly large or small frame fit right with the advent of threadless stems. If you buy a frame that's too large, you have to compensate with a short stem that can lead to twitchy handling and quick steering. If you buy a frame that's too small, you have to add lots of spacers and/or a riser stem to minimize the saddle to handlebar drop.
re: The key word in your question is "slightly"dzrider
Oct 22, 2002 10:05 AM
For me bike fit is about feeling centered and balanced on the bike. I can create equal triangles with points at the handlebar, seat, and bottom bracket on quite a few bikes by moving the seat and bars. Where this triangle sits between the axles changes how comfortable I am and how well the bike handles for me.

Moving the triangle slightly would probably be unnoticed until you go a long, long way or try to get through winding descents at high speeds. Lots of folks never do either. Moving the triangle a lot can really change how a bike feels and handles. A 9cm stem and a 12cm stem feel radically different to me.