I’m looking to invest some money into a new carbon wheelset that will be an upgrade from my Easton EA70 AX aluminum wheels (24mm internal, 20mm deep, ~1800g). I need help deciding between 35 to 50mm wheels. I will be running 35c tires.
First question: How does one quantify any aerodynamic benefit? I know that some brands like Hunt and FLO have done extensive testing, but for brands that haven’t am I just throwing money away in hopes there will be an aero advantage?
My second question is: I know this likely “depends”, but, is there going any measurable difference between 35 and 40mm or is 5mm kind of a toss-up?
I’m looking at the following (all of which are 35-40mm deep, and around 1600g)
My first thought is that a 35mm depth isn’t that aero and that 35mm tires (wider than most every rim) is going to further negate aero benefits. It’s going to be a light bulb shape rather than an airfoil shape.
Peak Torque on youtube did a wider tire aero test. He was testing GP5000 32mm tires versus his regular 28s on 29mm wide rims and 32.5mm wide rims. The wider rims tolerated the wider tire much better.
If you want a significant aero upgrade go deeper with tires matched to the width of the rim (105% rule and all that).
Just looking at the cross sections & knowing your tire choice I’d pick the G25.
However, it looks to me like the Reynolds AR41 has a LIFETIME WARRANTY. My experience with FLO carbon gravel wheels is that they break under normal use. So I would have for sure made out paying an extra $700 & getting a lifetime warranty. Just saying.
But also, in my opinion, if you slap a 35mm wide tire on that AR41 it’s going to be materially aerodynamically inferior to the G25. Especially in a little bit of a cross wind. Let’s say 3 to 5 watts.
Aero increases with speed - if you just ride gravel I would be surprised if there is much difference between them - it’s not like the TT bike CdA arms race…will look cool though…and the bit about Wiggle’s financial situation is relevant…would still buy energy drinks from them but not wheels, bikes, smart trainers…they could go bust at a days notice
I’d eliminate any wheel whose inner rim width is less than 25 mm. Note that some road wheels would be suitable such as Zipp’s 303S.
There are two sides: any specific aero claims are hard-to-impossible to transfer directly to the real world. On the one hand, you have mostly windtunnel data that is often at speeds, which are not relevant to amateur athletes. On the other hand, aero benefits are real, and wheels are quite high up on the list.
However, body position and clothing are by far the most significant factor.
I’d go deeper. 40–50 mm is the goldi locks depth for good reason. I don’t think I’d ride anything shallower on a dropbar bike, excluding dropbar mountain bikes. With modern wheels of this depth, wind steer is not a concern in practice.
A wheel that is missing from your list is 3T’s Discus 45|40 Limited, which was to my knowledge the first gravel-specific aero wheel. It is aerodynamically optimized for 35–40 mm tires, but can obviously take wider tires. (Optimized refers to the 105 % rule where ideally the wheel’s outer width is at least 105 % of the tire width.)
Josh Portner has expressed his approval of the 3t discus 45 a few times. 45mm deep and 40mm wide external so they’d still seem to satisfy the good ol’ rule of 105 with a 35mm tire if that is indeed the WAM. Not cheap but not the most expensive either.
Appreciate the advice. I should have mentioned that 35c’s are what I’d like to run, but I have a wheelset that I could use for rowdy gravel and run a smaller 30-32c tire on the aforementioned carbon wheels. Not married to a high volume tire on them.