3T Exploro – A Deeper Dive Into Low Speed Aero

Since 3T launched the Exploro earlier this year, there is one question I continue to hear, “why do I need an aero gravel bike?”

It’s a valid question. I had a chance to catch up with Dave Koesel, general manager of 3T’s US operations, at Interbike’s Outdoor Demo, and posed the question to him.

“Any time you are moving in air, aerodynamics is a benefit. So if you are competing in a race in the atmosphere, then you are going to have an aerodynamic benefit that’s going to your advantage.”

Cycling continues to become more and more specialized, from the events we ride to the equipment we use. This fracturing creates niche markets, but in my opinion, it can lead to more versatile equipment. If you subscribe to Team Sky’s take on marginal gains, then the Exploro could be a “n-1 bike” that has so much to offer to a very large part of the market.

Pro cyclocross is a great area to look at in a study of aerodynamics at slow speeds. Though frame companies have yet to really emphasize aerodynamics like they have on the road, you’ll see many pros racing in aero helmets, skin suits, and deep profile wheels like Zipp 404’s. Yes, there are other practical benefits from these pieces of equipment, like inclement weather protection from aero helmets that have little to no vents, but in my opinion, it is a matter of time until we start to see aerodynamics taken into a greater consideration as it is on the road. With the Exploro, 3T has become a pioneer in this area.

Many might think gravel racing is something new, but the early years of road racing was all on gravel. 3T’s approach to what they are calling “Gravel 2.0” is all about freedom and exploration, hence the Exploro name. The brand also puts an emphasis on performance with everything they do, so the goal became creating a bike that is fun, functional, and FAST! Testing at the San Diego Low Speed Wind Tunnel proved that aero matters, even at slower speeds.

The Squaro shape used on the Exploro blends the stiffness, strength, and light weight of a square tube with the aerodynamics of an airfoil shape. “When we created the structure of the frame,” commented Koesel, “we asked where can we add aerodynamics to give you some kind of an aero benefit. You look at events like the Dirty Kanza, and the winner does it in 8 hours or so. If we can give an aero benefit to that guy, maybe we can get the rider to the line faster or fresher, because they have been conserving.” The end result is a rounded nose that flares out to the sides before coming back to a squared off KAMM tail shape that we have seen on many aero bikes on the road.  Cutting the tail off of the airfoil keeps the benefits of the airfoil shape, with reducing the surface area for cross winds to grab. The wider tube profile on the down tube picks up the air coming off of the wide front tires and also hides the water bottle from the wind.

Testing the theory is difficult though. Knobby tires behave unpredictably compared to smooth road tires and 3T wanted to have solid data to back up their claims made for this new category of bikes. To do that, they tested a traditional round tube frame in the same tube widths, geometry, rear stay design, and components as the Exploro. Before adding a rider, 3T tested the bikes on their own. To mimic speeds typically seen in the road and gravel world, they completed the wind tunnel testing at 20 mph, not the traditional 30 mph. Sure, they could have tested at the higher speeds and possibly shown larger gains, but they preferred to keep it realistic.

The first pass, 3T ran the Exploro and the round tube frame with 700c Discus 35 wheels and Schwalbe One 28mm tires. What they found was about 65 grams of drag difference (approximately 330g vs 395g respectively) at 0 degree yaw. When swapping out the Schwalbe’s for WTB’s Nano 40mm wide gravel tire, the Exploro bumped up to about 375 grams of drag, and the round tube frame jumped to about 420 grams of drag. The interesting bit from these wind tunnel results is that the Exploro is faster than the traditional round tubed frame, even with the wider 40mm gravel tires.

 

Even when you add 750ml water bottles, the Exploro is still faster at all but about 3 degrees of angle.

 

When it comes to wheels and tires, there has been a rebirth of the 650b size on the road and adventure arena. By decreasing the rim size, you can run a wider tire (clearance permitting) and still keep the same outer circumference as a 700c wheel and tire. For example, a typical 650b x 2.1” wheel and tire combination is similar to a 700c x 33mm cyclocross tire. The widths will be different, bit the outer diameter should be pretty close, depending on tread patterns. The larger volume tire will provide a smoother ride, providing you are running an appropriately lower air pressure.

As part of the Exploro platform, 3T added the 650b wheel size to its Discus wheel range. Previously released in 32mm and 58mm depths in a 700c rim, the 650b comes in 21 and 28mm depths. These 650b wheels are optimized to run wider tires compared to their 700c counterparts. The new Discus C25 Pro wheel set is an alloy rim with a 21mm depth and inner width of 24mm. The C30W Team wheels feature a carbon rim with a 28mm depth and 28mm wide inner width. Despite the larger dimensions, the C30W Team has a claimed weight of 1,600 grams, 40 grams lighter than the C25 Pros. To increase their versatility, the end caps can be swapped with relative ease to work with 135mm quick release, and 142mm thru-axels in 12mm/12mm and 12mm/15mm front and rear options respectively.

Earlier, I mentioned that you can stuff 650b wheels with 2.1” tires on the frame. You might be wondering how the Exploro fares with fat rubber that 3T is calling Gravel Plus. Hed Ardennes wheels in 700c and 650b were used for this round of testing to try and keep things as similar as possible between the rim sizes. As a base line, the Exploro was equipped with 700c Ardennes and the WTB Nano 40mm tires. Next, they ran the Exploro with the 650b Ardennes and Schwalbe Racing Ralphs in 2.1”. Finally, they ran the round tube frame with the same 650b Ardennes wheels and Racing Ralph 2.1” tires.

As you’d expect, the more narrow 700c x 40mm tires were more aerodynamic, but the Exploro with 650b x 2.1’s has some significant savings over the round tubed frame.

That’s not the end of the story. Bikes get dirty, especially when you take them off of paved roads. I regularly ride a trail system here in Southeastern Pennsylvania that includes a section of fine gravel. On good days, a.k.a. dry, my bike will get a bit dusty. On not so good days, I’ll end up with a splattering of mud kicked up on the downtube. Think of just about any cross race, and it takes it a bit further. 3T wanted to explore how mud affects the aerodynamics of the frame, so they 3D modeled a design for mud, and created it using a 3D printer. This allowed them to consistently test from one frame to the next. What they found might surprise you.

In both cases, the Exploro and the round tube test frame with mud came up with better drag numbers than without when it came to riding into the wind. For the round tube, very modest savings were found between 0 and 7.5 degress. The Exploro’s advantage went out to about 10 degrees, and saw increased savings over the round tube out to about 7.5 degrees on the drive side, and 10 degrees on the non-drive side. While the gains are modest, about 10 grams, they continue to add up.

The final bit of wind tunnel data 3T shared during the launch shows how the Exploro with C35 Pro wheels with the WTB Nano 700x40mm tires, two 750ml water bottles, and mud, matched up to the clean round tube test frame with C35 Pro wheels and Schwalbe One 700x28mm tires. For the 0 degree headwind, you’ll save between 25 and 30 grams of drag and continue to see savings across the spectrum. I have to say, this surprised me, and shows that the Exploro is a slippery bike in all conditions.

All of this data wouldn’t matter if when a cyclist is added to the equation, the bike does not provide an aggressive, yet comfortable and stable position. Add in their performance gravel geometry, narrow Q-factor, low trail, and short rear stays, and you have the recipe for a fast and agile bike that will get you to the finish line fast.

We should have our test rig into the BWN service course next month, so check back for the full review later this month.