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Old 05-14-12, 09:02 PM   #1
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Sizing Philosphy Question

OK, so after being away from mountain biking for a few years, I go to one of the two LBS's in town to learn about the whole 29er thing. The young sales lady makes a good guess of my height and pulls out a Giant in a size L to take a look at. When I throw a leg over the thing, the top tube only provides an inch or so of clearance. Other than the comically short stem, the thing feels like a road bike. When I ask why my old 26er had gobs of clearance and this doesn't, she can only offer "because that's the way they're supposed to fit." So, what happened here? Why were we told that we needed a couple of inches of clearance for so many years and now we don't? And what's with the short stems? The young sales lady's reply, "because you're supposed to be more upright." What's behind these shifts in frame sizing paradigms?

Should've mentioned: I'm 6' tall and looking at getting a hardtail XC bike.

Last edited by metabike; 05-15-12 at 04:27 AM. Reason: additional info
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Old 05-14-12, 09:12 PM   #2
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Well, for one, she sucks for not explaining her reasoning to you. My guess is that it's because she doesn't know why herself, and is just going by the size someone else told her each height of person should ride. That or maybe she's just poor at her job. Also, I wouldn't ride a MTB that I barely had clearance on. I know some do, and I know a lot don't. I know that I personally am going to encounter hills and the like that will require me room to dismount in situations that are sometimes less that ideal flat ground. In those situations, you often need those extra couple inches to get your feet stable without compromising the safety and comfort of your crotch. I think I've got 2" of room on my bike. As for the stem, that just depends on the bike. If you look at a downhill bike, many of them have basically no stem. If you look at some XC bikes, many of them have 90mm stems. Any bike made to fit any number of riders might be anywhere in between. It just depends on the bike and how it's designed. The most important part is that you're comfortable physically on the bike, and mentally comfortable with the bike. Who knows, maybe it'll be one of those crazy 26" wheeled bikes with a longer stem.

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Old 05-14-12, 09:21 PM   #3
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how tall are you? if you are between 5'9 and 6 you probably need a large. stand over height was a nice rule of thumb when top tubes were straight and stems were long and everyone was in some kind of ridiculous roadie racer tuck (hooray for alliteration!), but mountain bikes today have a more upright geometry because it's more comfy and provides better handling. no, you shouldn't be racking your nuts when you are standing with a bike between your legs, but it depends on the bike, and two or more inches clearance means the bike is probably waaay too small for you. bike fit is more than stand over height.

short stems and wide bars give you better handling. unless you have arms that hand down to your knees, most stems that come stock on bikes are too freakin long. we all run 50s, maybe 70's.

it also depends on what bike. each bike company has a different geometry so some feel higher or larger than others. i wish i could explain better, but i'm drunk right now, so there is that.

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Old 05-15-12, 05:38 AM   #4
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I wouldn't be too hard on the sales person. She is young. Some of the answers to your questions require some historical perspective, and really, who can say why your old bike had gobs of clearance and the current one does not? She doesn't know a thing about your old bike.

Was your old bike from the rigid era? The addition of suspension forks raises the front end and makes it tougher to get multiple inches of standover. 29er wheels make the standover problem difficult for short and medium-sized people like me. (Hence all the bent and sloping top tubes these days) Maybe your older bike was a smaller frame size than the 29er you were looking at.

The trend in stems is to go short. I dislike riding greater than an 80mm stem. Short stem. Wide bars. That's how I roll. Go back in time 15 years though, and you'll see 120mm stems and narrow bars.

Years ago standover was probably emphasized as the key to fit more so than it is today. So there is another trend that has changed.

You're six feet, so a size large is a good beginning point. Without seeing you, large is the size I would suggest you try first. Ideally, test ride one size on either side. That way you can better hone in on the size that works.

Also try other brands. Giant sizes in even inches like 18 and 20 an 22. Specialized, for example, sizes in odd inches like 17.5, 19, and 21. If you feel a 20" Giant is a tad too much, you might like a 19" Specialized.
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Old 05-15-12, 01:31 PM   #5
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Stems are getting shorter and shorter, 15-20 years ago, it was 130-150mm, 10 years ago 110mm, 5 years 90mm, now its from 0-90mm, depending on what type of bike, a similar thing is with handlbar width, originally bars were 540/560mm, now 680-700 is the narrowest you will see, with them going up to 914mm (1 yard)
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