Deep dive on the Flatbike Century THINstem

Roadbike Review recently published an analysis of the Flatbike Century Folding road bike. One of the great things about a technical drill-down like this from a professional bike mechanic is that it highlights the strong points while offering insights for model improvement tweaks that the feedback from our early adopter program may have missed.

The Flatbike Century, a folding road bike designed for comfortable 100-mile rides. (Photo credit: Roadbike Review)

Two methods of folding: Ritchey Breakaway vs. Changebike foldaway

In particular, Roadbike Review compared the Changebike folding frame approach to the more well-known Ritchey Breakaway system that requires disassembling the entire frame. The comparison could not have been more accurate.

Ritchey’s Breakaway frames fold down smaller, which is great for flying with a bike. The downside to Breakaway frames is that they take longer to assemble and disassemble—somewhere between 20-30 minutes, depending on the type of bike and the mechanical aptitude of its owner.

In contrast, Flatbike’s frames can transition from folded to functional in under a minute. This makes them a good option for riders who have limited space in their homes or want a bike they can transport in the trunk of their car.

Flatbike also has an edge on price. The Complete Flatbike Century tested here retails for just $81 more than the price of Ritchey’s Breakaway Road frameset. When built, A Ritchey Breakaway will cost approximately 800-$1000 more than the Flatbike Century with a comparable build.

Two opportunities for improvement

The reviewer also singled out two areas of the Flatbike Century spec for improvement:

• The 53/39 crank should be reduced to a 50/34 compact crankset for casual/sport riders.
• Combining a carbon post with a quick-release lever is asking for overcranking and a cracked post.

There are personal reasons for both of these specs–I personally tend to crank a big gear, and I use Finish Line Fiber Grip to avoid the carbon stem slip that leads to overcranking–highly recommended, by the way.

But more importantly, there are good reasons to listen to the gentle nudging of a professional bike reviewer. Both a 50/34 crank and an alloy seat post will be standard equipment on the Flatbike Century folding road bike within two weeks.

The Flatbike Century stem: Fold it or not?

The most interesting–and unexpected–feedback in the Flatbike Century review was this perspective:

I didn’t get along well with the folding stem. One of the trade-offs for its ability to rotate 90-degrees is a very high handlebar position. Given that this bike is geared toward recreational riders, some cyclists may appreciate the higher stack height and more upright riding position.

The Flatbike Century ships with a THINstem and 1″ of spacers underneath. Road racers sometimes flip the spacers up top, as this reviewer did. (Credit: Roadbike Review)

Both observations are spot-on. Yes, the THINstem adds height to the stack, specifically 1.75″, which is why some riders lower the stem on the steerer, as shown. If the top of the steerer tube then interferes with folding, that’s a simple cut on a carbon fork.

That still leaves the bars raised 3/4″ above the floor position, however, which may be an issue for some riders who prefer to ride the absolute minimum height, very low down. These are unlikely to be recreational riders. Higher bars and a less-bent back were also considered as contributing to the design goal of comfortable 100-mile rides. What’s the first thing to start hurting on a long ride?

This all raises two interesting questions:

1. Is the THINstem an absolutely necessary spec for folding a Flatbike Century for transport?
2. Is there other value for the THINstem other than folding for transport?

Close-up of default THINstem folding

With a THINstem, the bars turn inward, with the levers just over the wheel, which nestles in between the bar and brake lever.

All four sizes of Changebike road frame can do this.

From the front, it looks like this.

When folded, the frame and rear wheel assembly fit into a space just about 10 inches.

That’s the default spec, with the THINstem installed. But what if you’re a “low stack” rider who really doesn’t like to add that extra bar height? Next we’ll show the same positions with a long and short regular stem.

Close up of folding with a 120mm regular stem

With at least two sizes of Changebike road frame—460mm (Small) and 490mm (Medium)—the bars are low enough for the grips to slip through the wheel. And the standard wheel shipped with the Century allows that.

As long as you don’t have a Large or X-Large frame, the grips can slip through the wheel, for a width of about 13 inches.

It looks elegantly simple, but make sure the wheel doesn’t turn with the grip stuck in it. Note: This approach works only when the bars are mounted all the way down.

Close up of folding with a short stem

The same concept applies if the stem is shorter. For an extreme test, here is folding with a standard mountain bike stem.

Same folding as above, just with a thinner profile of about 11 inches using a shorter stem.

The left hood of a Medium (490mm) bike just barely fits under the rim.

If your bike is large or extra large, and you want to ride with a short stack, then you’ll need to turn your bars the other way.

At 17 inches wide, this isn’t elegant. And a longer stem would make it even wider. But it still beats trying to fit a five-foot-long bike into a four-foot-long cargo space.

Ultimately, we chose the THINstem because it delivers the minimum folded width with all sizes of Flatbike Century frames. Smaller riders have an option of folding their bike nearly as small with a regular frame. Larger riders don’t have that option (Full disclosure: I’m personally 6’5″, so this point was a major decision factor in the spec).

And finally…a THINstem superpower.

The more accessible your bike is, the more you’ll ride it. The more value you’ll get out of it, and the better shape you’ll be in. Imagine if you could store your bike conveniently and out of the way…in the hallway by the door.

Or don’t imagine it. Make it happen with a THINstem.

In the end, the choice of stem for a Flatbike Century is a matter of preference. If you’re optimizing for the lowest possible stack, you’ll go with a traditional stem. And if you’re optimizing for maximum flexibility, you’ll go with a THINstem.

What means the most to you?

Bob Forgrave is president of Flatbike, an
ecommerce company offering full-size folding bikes
and kits to make any bike take up half the space.

425-985-6219