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The Grind is a weekly column about all things gravel.
The more gravel bikes I ride, the more I become an evangelist of long, flexy carbon seatposts. Here’s why.
For enjoyable long-range riding, it’s vital to have happy hands and a happy butt. You could have a $5,000 bike, but your ride is no fun if your hands are going numb, your wrists hurt, or if you are chafing or going numb between your legs. Those puzzles can usually be solved with a good fit, and an agreeable saddle.
But after you have your touchpoints sorted, is there really any difference between one gravel bike and the next? Or between a gravel bike and cyclocross bike? Yes! A seatpost with a bit of flex to it can make a huge difference, especially if the frame design has a sloping top tube that allows for more exposed post and thus more movement.
While differences in frames can be difficult to detect, it’s easy to feel differences between seatposts, especially when going from extremes like a zero-setback aluminum post to a carbon post that’s engineered to flex.
You may have read lab tests on seastpost flex, like this one Lennard Zinn wrote for VeloNews or this one my old colleague James Huang did for BikeRadar. As those tests show, there clearly is a quantifiable difference between posts. But perhaps more importantly — and often different than in frame testing — there is a difference that riders can feel.
If you are coming from a road bike, a generously flexing post may feel weird, like your back tire is going flat. And, to play devil’s advocate, you could probably take it into the lab and find a minute but measurable decrease in pedaling efficiency at low-rpm, high-torque efforts. But faced with miles of washboard or otherwise rugged road, I’ll take that tradeoff.
Some seatposts I have appreciated recently are the top-end carbon options from Canyon, Salsa, Giant, and Specialized/Roval. And I’m a big fan of Trek’s IsoSpeed solution where the seat tube and seatmast bow from a pivot at the top tube junction.
You can also get suspension seatposts, like the eeSilk from Cane Creek or the ShockStop Suspension post from Redshift. For me, the full-on suspension seatposts I have tried in the past like the Thudbuster feel like top-heavy overkill. But it depends on your preferences of where and how you like to ride.
For me, having a sloping top tube frame that allows for a long carbon post is the sweet spot. Which brings us back to the gravel vs cyclocross debate. Gravel and ’cross bikes differ on geometry in a few ways: Gravel bikes are lower, longer, and slacker than ’cross bikes designed for an hour or less of full-gas racing through tight turns and over off-camber ground. And of course gravel bikes pack a lot more tire clearance and oodles of mounts for liters of water and packs and fenders and racks, whereas a ’cross bike is normally a naked frame designed for an hour in a skinsuit. But to the point here — the comfort of the ride — ’cross bikes almost always have straight top tubes for dismounting and shouldering, and thus short seatposts.
If you’ve been on the fence about replacing your ’cross bike with a gravel bike, I’d suggest taking one for a spin. Before you even climb on, press down hard on the saddle with your hand, and compare that flex — and the resulting ride — to what you’ve been on before. I think you’ll agree, comfy is good.