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Why longer top tubes and shorter stems are simply gravitating us back to a "normal" that we never knew of.

Jan 23, 2014 at 22:59
by r C  
There is a normal or a neutral for many things in the automotive world, whether it's on 2 wheels or 4. When the mountain bike was born, people were not only stealing over components from the existing cruisers and 70s road bikes, but their dimensions and geometries as well. Over the years, we've gradually gravitated towards "our" normal by trial and error, mistake, and by painstakingly manipulating bad geometry 1 tiny degree or millimeter at a time.

Occasionally, this slow process gets a boost when somebody does something ballsy like Mondraker's Forward geometry or the 2014 GT Fury with its super long top tube. Instead of growing the top tube by 5mm over the course of 5 years, they just went straight to what felt right - a really long top tube, thus a really large sized bike without compromise. They didn't go off of how far off it was from Trek's Session or Giant's reach, but just chose the length that they wanted without compromise.

Mondraker is doing exactly what I think is "normal and sane" but before we talk about what they did, let's talk about 2 important things: Reach and how new technology is embraced,

As an atheist, I'm still thanking God that we now have reach(and stack, to a lesser degree) in our geometry charts because this is the one single factor that determines the size of a bike whenever you're out of the seat(doing downhill, sprinting, jumping) Stack can still be manipulated with stem angles, headset spacers, bar rise heights, A-C, etc. Reach is set in stone once the alloy tubes have been welded on the jig or the carbon has cured in its mould. Stem length should be a factor of handling and not to Band-Aid a frame size that doesn't fit you.

Humans and embracing new technology and standards: 66-67 degree head angles on a 6" bike is the norm nowadays and it feels better than whatever we had before. BUT, bring that LOW BB, slack head tube, and 6" of travel back 10 years and people would mistake this bike as factory mistake that should be exiled to the attic or destroyed in that industrial press that Killed the terminator in T1. They'd say, "my pedals keep striking the ground, this is an obvious mistake." "How am I supposed to climb my switchbacks with that head angle??" "Do you REALLY need 6" of travel?" This is the norm for us because we've realized that whatever we give up in pedal-strike opportunities and other sacrifices is more than made up for In a bike whose geometry allows us to ride so much better downhill. So keep this in mind when you first climb aboard mountain bikes who have a longer top tube and shorter stem.

Nobody is telling anybody to ride a bike that does not fit. You can't just have a frame with a long reach and your regular 50-60mm stem and you can't put a 35mm or 10mm stem on your current frame. What I see going on is that we're returning back to a normal or neutral from our 130mm road stem roots. From the bike side of things, we've desired the handling of shorter stems and were stuck with our old frame sizing. It was not long ago that Santa Cruz's advertisement for the 160mm Nomad had it outfitted with a 90mm stem when it first arrived on the scene.

So we've gone from longer stems to shorter stems over time and now our frames need to accommodate this. Is that it? NO, there's more. There's a purpose for this extension off the steerer axis that we call a stem: proper trail/handling. Mondraker riders have decided on having a small length of "stem" to create some trail(not in the same sense as when we talk about forks) and this is similar to what motocross and endure motos have gravitated towards through the 70s and have settled on for the past decade or two. One important factor is the consequences for having a "length of trail" or stem that is longer than the minimal amount necessary to create stability. In other words, when you trade a long top tube for s horter one, and a short stem for a long one, your front wheel is closer to being "under your bars" rather than sticking forward and supplementing your stability.

This is the next step in evolution or simply undoing the unfortunate standards and geometry that mountain bikes were born into. Just like we've seen our BBs get lower, head angles go from 69 to 63 degrees, and stems shrink to 35-50, the longer top tube to compensate for that lost in reach and the more optimal position that it puts our front wheel in is the next logical step in finding our neutral or "normal" baseline.

If you think this is crazy, why don't you try riding a bike with a shorter top tube(1 size smaller) with a stem 35-50mm longer. You'll find that your front wheel is way under your handlebar and your stability has gone out the window. Is 10mm too short? Who knows, I haven't tried it, but I'm pretty sure I wouldn't go back to 60mm. But mx riders have a preference and their normal is a range that is certainly shorter than a 50mm stem. BTW, their head angles are often around 63 and enduro moto bars are roughly around 30. Sound familiar?

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Member since Jul 4, 2008
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