ENVE initially launched the M Series in 2014. At the time, one of the main goals was to just convince the riding public that carbon was a reliable material to use for rim construction and was here to stay. It was also designed to be the first reliable hookless carbon tubeless rim.
Obviously, a lot has changed since then. Carbon is pretty much accepted as a rim material, and for the most part, tubeless reliability isn’t really an issue. So when it came time to rework the M Series, ENVE looked at is as a chance to completely reimagine what carbon mountain bike rims could be. The result is a completely new design across the board from XC to DH with rims that are more compliant, have better impact strength, and may just make pinch flats a thing of the past.
Calling it their Dynamic Impact Design, the new wheels are all about the reworked profile. Divided into two categories, rims on the XC and trail side of things go with a wide hookless bead that is all carbon, while the Enduro and more aggressive rims benefit from their new Protective Rim Strip design.
According to ENVE, one of the biggest factors to pinch flat resistance is the width of the leading edge of the rim, but shape of the leading edge is important as well. Moving from 3.3mm on the previous M Series to 4.5mm for the Wide Hookless Bead and 5mm for the Protective Rim Strip, the change has a massive effect on pinch flat resistance and impact strength. 
After testing previous M Series against the new generation and even an odd M70 HV with a Cush Core insert, the results speak for themselves. The Wide Hookless Bead of the new M525, M630, and M635 offer a 30% increase of impact strength and impressive 60% increase in pinch flat resistance. The Protective Rim Strip design on the other hand found on the M730, M735, M735 E-Spec, and M930 results in an incredible 100+% increase in pinch flat resistance and a 10-20% increase in impact resistance.
Basically, ENVE simply hasn’t been able to cause a pinch flat with the Protective Rim Strip design with their current fixtures. That doesn’t mean they aren’t trying though – they have the ability to drop a heavy enough weight that it is cracking the rim, but the tires still won’t flat. And since the rim strip seals the rim channel completely, the tires maintain their seal even if the rim is damaged. ENVE says this is really more for the gravity racers who can’t afford to flat out on their run, even if they hit something hard enough to break the rim.
Both rims are designed with a more triangular profile which uses thinner walls than previous M Series. According to ENVE, this along with a refined laminate has had a profound effect on ride quality with the new rims offering better compliance across the range without sacrificing stiffness. The shape is also better for the manufacturing process.
The Protective Rim Strip wheels use a similar shape, but include a protective plastic rim strip that must be used with the rim, and is specific to each rim. Included with the wheel is a special rim strip lever to remove the strip to service spokes, but the strip come pre-installed on complete wheels. ENVE says that the biggest barrier to this design was the making of the strip itself – having it made overseas would simply be too expensive in terms of tooling, so the strip is made in Ogden along with the rims.
Essentially split into two categories, anything with a 5 or 6 falls into the Wide Hookless Bead territory. Anything with a 7 or 9 is the Protective Rim Strip Design. In terms of the naming structure, it’s pretty simple – the first number is the series (5 – XC, 6 – Trail, 7 – Enduro/AM, and 9 – DH/FR), while the second two numbers is the actual inner width of the rim. Based on the inner width, ENVE has recommended tire sizes, and hole counts are based on use. All eight models are available in 27.5 or 29″ versions, and ENVE expects them to ship by October. And yes, there is a M735 E – for ebikes with plus tires.
It’s taken ENVE years of development and testing and over 800 rim prototypes this year alone, but if all (or even half) of their claims turn out to be true, these rims have the potential to be a big improvement not just for ENVE, but for mountain biking as a whole.
