• Pros: legit aero performance, adjustable IsoSpeed flex, available in rim and disc
  • Cons: price, integrated bar might not work for some
  • Price: starting at $5,899, tested at $11,899
  • Similar: Specialized Venge Disc, Canyon Aeroad Disc, Giant Propel Disc
  • Photographed: Elephant Rock


A cushy aero bike?! Yup, it’s true. The adjustable IsoSpeed suspension is what sets this bike apart. For this build, the Bontrager wheels are on par with the best out there, and the tires are close behind. But a bike this expensive should have a power meter. And the bar/stem, while adjustable for angle, still means you better be sure you are sure about your fit measurements before you buy.

Fast and comfortable

Fast or comfortable. This was the choice with early aero bikes, as the deep tubes shapes that worked so well for reducing aerodynamic drag did not work so well for absorbing bumps in the road. Trek changed that with the Madone SLR Disc, which has adjustable flex built into the rear of the bike. 

What Trek calls the IsoSpeed Decoupler is a pivot inside the junction of the top tube and seat tube/seat mast, which allows the latter to flex fore and aft without compromising the rigidity of the rest of the bike. On the new bike, you can adjust how much flex you get with Allen keys and a few minutes of work.

Aero everything

Whether Specialized, Trek or Giant, most of the bike companies will tell you their aero bike is the fastest, and that is no different here. Is that the case? Who knows. But after having spent time and done my own testing in wind tunnels in Germany, France, California, Arizona and North Carolina, I can confirm that, yes, aero bikes are indeed faster than round-tube bikes with shallow wheels. But you knew that already.

A few basic design features make aero bikes faster: tube shape, internal routing of shift and brake lines, and ovalized and integrated handlebars. As with anything on a bike, each of these things comes with a price and a balance of other characteristics. With the Madone SLR Disc, Trek hedged against most of the compromises.

With electronics and hydraulics tucked inside, the Madone’s front end is all kinds of smooth

Huge, oval tubes, for instance, don’t flex much, but the IsoSpeed fixes the comfort issue. Internal routing can make shifting or braking with cables poor if there are tight angles, but electric wires and hydraulic hoses aren’t affected. And the integrated bar/stem greatly limits fit options, but Trek added a +/-5 bar angle adjustment and, critically, offers fit services through its dealers so you order not only the right sized frame but the correct bar/stem length and width.     

Fit, feel and physics

Here’s the thing: It doesn’t matter how aero your bike is if you aren’t. How you fit onto your bike is always the most important thing, not just for aerodynamics, of course, but for efficiency and comfort.

Trek has long had two fit geometries: H1 for low-and-pro and H2 for a more upright and sustainable position for more riders. The Madone SLR comes in a Goldilocks middle ground, the H1.5. The middle-of-the-road head-tube height is a good thing in my book.

While the interlocking two-piece spacers are a slick solution for height adjustability without having to redo hydraulic lines, the integrated bar and stem means you can’t just swap in another stem to adjust fit. I can’t stress enough how important it is to have your fit measurements dialed before you buy an aero bike.

Two-piece spacers mean you can adjust stack height without having to mess with hydraulic lines

A few riders have asked me whether the Madone feels sluggish compared to a standard race bike for accelerations. In terms of perceived snap, the frame lateral stiffness is on par with the best, so there is no pedaling efficiency loss. However the bike is a bit heavier than a standard bike — 18lbs as shown here with pedals; the rim bike is 300g lighter — so a physics equation would show a small disadvantage. And, of course, mo’ weight is always mo’ slow when going uphill.

But… aerodynamics are indeed a thing. And less drag means more speed for the same amount of work.

This is one of cycling’s many balancing acts. What is best for you depends on where you live (Dubai or the Dolomites?) and how you like to ride.   

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Comparison to other aero bikes

The primary difference between the Madone and bikes like the Specialized Venge or the Canyon Aeroad is the IsoSpeed, which Trek claims offers a range between 17% softer and up to 21% stiffer than the previous Madone. Can my butt detect those percentages? No. But I can say that the softest setting feels like you’re riding big, squishy tires while the tautest setting feels like, well, an aero bike.

The parts package varies by model, of course, but the top-shelf version I tested has the excellent Bontrager Aeolus XXX 6 wheels (you can read my review on BikeRadar), Bontrager R4 320 clinchers and the best-in-class Shimano Dura-Ace 9170 group. Bontrager has come a long way with its wheels, which I would now put on par with Zipp, and ahead of the Reynolds that come on a Canyon or Roval that come on Specialized.

Notably, you can get this bike in disc or rim-brake. I won’t try to convince you one way or the other in the rim vs disc debate, but I will say that braking rapidly and easily is a nice thing. Coming down Flagstaff, a local 2,000ft climb by my house that I ride up and down often, I ended up with a few Strava PRs, which you could attribute to an aero bike with disc brake and/or me just eating more pastries this summer. I also ended up with some fairly dramatic squealing from braking hard into corners and then leaning the bike.

In my experience, disc brakes are better, heavier and, often, noisier than rim brakes. With the Madone SLR, you can choose.

Bottom line: a unique aero bike

So, all the benefits of an aero bike without the main drawback of a rough ride? What’s not to love? The only issue I had was with the seatmast’s lateral movement. At high-torque, low-RPM pedaling, I could feel and see the saddle moving sideways in relation to the rest of the frame. The lateral movement isn’t anywhere near as dramatic as the engineered fore/aft movement, but it’s noticeable. I don’t know if it’s a bad thing; fore/aft movement is comfortable, so what’s wrong with side-to-side play?

While you can adjust the IsoSpeed, it’s not like you do it with an electric remote; you need tools. First, you unscrew a little 2.5mm Allen on the back of the seat tube, which removes tension on an elastomer damper that butts up against the moving frame piece. Then, you removed the 4mm bolt under the top tube at the end of the IsoSpeed boom. Then, you adjust the slider forward for more flex, or rearward for less. The process takes about three minutes.

Firm or plush? You can have both, plush any setting in between

Trek first introduced adjustable IsoSpeed on the Domane endurance bike, where it featured on the seat tube. The single-leaf-spring concept is the same here, just with a 90-degree bend in the moving part. 

The beauty of the IsoSpeed is how it feels like a normal bike until you hit a bump. Since the suspension consists of a carbon tube and not a spring or a hydraulic system, there is no bob when pedaling normally. You can create rider-induced flex by hopping on the bike cyclocross style or an intense seated sprint, but in normal conditions it is bumps in the road activating the system.

With the Madone SLR, Trek has delivered an impressive aero race bike. The list of plusses on this bike is long. If I were a paying customer, though, I would like to see three things added to the stock machine: Di2 sprint shifters for more shift-position options, a D-Fly for Garmin control from the hood buttons, and a power meter.

I realize not everyone wants a power meter, but if you are nerded out enough to consider a high-end aero bike, then I would be you are nerded out enough like me to train with power. I know a lot of the folks at Trek do. This is the money-is-no-object model we’re talking about here. It should be perfect.

The Trek Madone SLR 9 Disc is a remarkable aero bike for both its comfort and the adjustability of the frame stiffness. The parts spec is all absolute top end — including the Bontrager Aeolus XXX 6 wheels. Many times house brands are sub-par; here that is absolutely not the case. If you want a fast machine with all-day comfort, you will be hard pressed to find anything in the world like the Madone SLR.

Ben Delaney

Ben Delaney

Roll Massif editor

Ben has been riding bikes and slinging stories since he was a paperboy. Professionally, he’s been a cycling journalist since 1999, when racing bikes and studying journalism at the University of New Mexico led to pulls at VeloNews, BikeRadar, Cyclingnews and elsewhere. After traveling the world to report on pro cycling in Europe and manufacturing in Asia, Ben is happy to be at home in Colorado, writing about the incomparable riding and the creative people who drive the cycling culture.

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