Just before 2020 arrived, we were able to get the answers to a number of mountain bike related questions with the help of ENVE Composites. Now, ENVE is back. But this time the focus is squarely on gravel and road. With gravel races and events gaining popularity at an impressive rate, it seems like more and more riders are curious about what actually makes a gravel bike, and how premium components from brands like ENVE can make for a better ride. Also, make sure to read to the bottom to find out how you can still win an entry into this year’s Dirty Kanza race plus ENVE wheels and a gravel handlebar!
Gravel Rim Width
Like mountain bikes, it seems like gravel rims are getting wider and wider. Is there a rim width that is most ideal for gravel?
Luke ENVE: This really depends on what tire size you’re running. One thing to consider is that as you add width, you add weight, so for ENVE we are always trying to strike just the right balance to make the best rim possible. In other words, as light, durable, and best riding as possible. Our G Series G23 (23mm internal width) is a 700c wheel and intended for primary use with a 38-42mm tire. Our G27 (27mm internal width) is a 650b wheel and primarily intended for use with a 1.9-2.1” tire. We could’ve gone wider on both these rims, but felt these widths maximized the rim’s design objectives allowing each model to be very lightweight and comfortable while providing ample tire support.
Gravel Bike Aerodynamics
It seems to be an industry wide agreement that gravel specific wheels (rims) should be quite shallow. As the American gravel scene seems to be the main motor in gravel R&D, with popular events like DK and others, why have the industry and ENVE in particular, decided that the aero benefit of a taller rim + a well-fitting tire, is less important on gravel, even when the ride is 200km + long? Would love to hear your thoughts on this, both for your own company and others. Shout out from Norway! -JD
ENVE: Sure, and a great question. ENVE has been looking at this for many years at this point and we asked ourselves the question of “aerodynamics in gravel” back in 2014 in the development leading up to the launch of the SES AR Series of wheels. What we learned is that basically once the tire exceeds 32mm and gains any side knobs/tread, you lose the majority of aerodynamic benefits. To make an aero rim for a larger tire is possible but it starts to get crazy wide and therefore exceedingly heavy, and again, this is assuming there is little to no tread on your tire. In short, the value proposition just isn’t there. On top of that, there is the fact that gravel riding is often on rough roads, if you’ve ridden or talked to anyone who’s raced DK, you know that the race is rough and also pretty slow. On a long, rough course like DK, a shallow rim with a refined laminate like the ENVE G23 provides unprecedented compliance and therefore comfort which is so valuable. Also, most gravel rides and races include a lot of climbing. DK is over 11K feet. Again, lightweight trumps aerodynamics at the speeds most are climbing gravel roads at.
Gravel Tire Aerodynamics
With all the research behind aerodynamics with road wheels and road tires leading to the 1.05 rule of thumb between the tire and rim width, how does this apply to gravel tires? Will we one day be running 45mm wide rims at Kanza? What research has been done on gravel bike aerodynamics? With 10 hours spent at 20mph a very slight difference in aero drag can make a huge difference in finishing time. – Michael
ENVE: We won’t pretend to have all the answers here, but what we do know and have learned is: Knobs and tread make it nearly impossible for air to transition smoothly from tire to rim, and therefore, aero efficiencies are essentially nullified by tread. The longer you spend on a bike, the more important light weight and comfort are. This is what we’ve developed the G Series to achieve. We made the rims as comfortable and compliant as possible to reduce rider fatigue. We made them as light as possible for the obvious reasons and that most gravel races include substantial elevation gains. Most riders are not averaging speeds of 20mph racing/riding gravel. Few average over 15mph, and most are in the 10-13 mph range. If you are a top fuel 20mph kind of guy, and the course is relatively smooth, we’d recommend something like our 3.4AR w/ a 30-33mm tire. This will provide some aero advantages, but only if you’re willing to say goodbye to tread or keep it to an absolute minimum. Colin Strickland won DK running our 3.4AR… Oh, and to actually answer the question. We don’t foresee 45mm wide rims at DK anytime soon.
Wide Rims and Tire Performance
You have been making rims wider and wider and tires became fatter and fatter. Despite better tire integration, the first one has been proven to ultimately be less aerodynamic (larger frontal area) than less extreme rims and the second one showed that except being able to use lower minimum pressures and a bit better grip, they were not bringing more absolute performance (to keep same comfort, wider tires need lower pressures and RR ultimately remain the same)… why are you pushing those 30+mm rim widths from an engineering point of view? – Jordi
ENVE: Hopefully we understand your question well enough, but it sounds like what you’re asking is “Why if 30mm isn’t more aero, and if large volume tires aren’t higher performance, then why do it? For ENVE, we engineer our SES lineup of wheels for holistic performance. Yes, an SES AR wheelset w/ a 28-30mm tire is going to have more frontal drag than a standard SES wheelset with a 24-26mm tire. What we achieve with the AR series is first, greater aero stability. A 4.5AR w/ a 28mm tire is extremely stable in crosswinds and at yaw. Also, there is rolling resistance. The rougher and more imperfect the surface, the more a high volume tire plays into your favor. On a rough road, the gains achieved in rolling resistance, will outweigh the losses caused in aerodynamic drag from an increased frontal area. It is also worth noting that these gains are further pronounced at slower speeds. Given that most roads people ride aren’t perfectly smooth, these same people are simply realizing that 28mm tires are more fun/enjoyable to ride than 25mm tires. We say, if you’re going to ride a large volume tire anyway, you might as well have the option to have a high performance aero system. This concept was originally born from testing with our World Tour team at Paris-Roubaix. PR is a perfect example where you have to run a 28-30mm tire to survive the cobbles, but the majority of the race is on smooth pavement. Well, making a rim aerodynamically optimized for use with those tires was a substantial efficiency gain over running the same tire on a more traditional width aero rim. The width of the rim is simply determined by the width of the tire we are optimizing around, and the goal being to make the system as aero as possible. If you’re a light-weight racer looking for maximum efficiency, you should still only be looking at our SES (Non-AR) wheelsets, and running 25mm tires. If you’re not racing in traditional road events, and looking for aero performance, more confident handling, comfort, and fun – then SES AR with a 28-32mm tire is going to be the ticket.
You developed a wide range of rims but it seems like little work has been done on spokes. We see carbon spokes on Cadex (Giant) and from Farsports, after Mavic did several attempts. Isn’t it a major possible improvement to bring back stiffness on rear wheels? –…