If you are entering UCI races, you need to know the standard used based on your weight and your equipment and take the time to measure out, but in most US events short of nationals it won't be a concern. Mounted on a 29"NoTu bes Crest EX with a 21mm internal width rim, at 45psi the MXPTubeless measured out at 34.8mm. On a HED Ardennes FR rim with a 17.8mm internal width, also at 45psi, the micrometer said 33.9mm. Granted, all specs can vary with manufacturing variance, use, etc., you just need to take the time to check your actual rim and tire. That variation goes for weight as well. Clement knows there is production variation, just as everyone who has ever weighed their tires is aware. A +/- 8% variance may seem like a substantial amount, but is pretty much standard across the industry. The listed weight for the 700c is 380 grams, and the actual tire tested was 392.

For this tubeless version the reinforced, yet supple sidewall that can handle lower pressures without fear of destruction, and best of all- no pinch flats from tubes. Donnelly rates the MXP Tubeless for a 35-60 psi range, and while we doubt anyone will push the upper range, we know many will fully explore lower numbers. Just so you know what the rated range is, we'll repeat, 35-60. The tread rubber itself is a Shore 70A durometer, which is firm enough to inherently offer low rolling resistance, but durable enough to wear better on hard or rough surfaces. The beefy nature of the tread knobs mean they will hold up well through regular use, relying on incuts and vectors for traction. You don't want to do a lot of road training, but if you use gravel surface roads or trails to connect training zones, the MXP will not only give you speed, but will hold up to regular use.

There are many cross venues in the US that feature hard, fast courses with just enough technical terrain to prevent a rider from choosing the fastest of tires. And even the coastal courses of New England and the Pacific Northwest can be pretty dry in the early Fall season. Once the mud runs thick and deep, the MXP might not be your tire of choice, but in just about any other situation, it can be run front and rear. As things soften up, many riders will even opt for a PDX or BOS up front, and an MXP for the rear, as a way to get the best of all worlds. That is the beauty of tubeless for many cyclists. It is easy to change out as conditions change, and ammonia-free sealants prevent the small punctures that can slowly, but surely prematurely end your race. The sidewalls can handle the low pressures you require and the large footprint of the contact patch of low pressure tubeless use afford you most of the advantage tubular riders have enjoyed, especially in slick conditions or off camber corners on the grass.

If you are building a quiver of tubeless cross tires for the season, you start with the Donnelly MXP Tubeless, and likely add a BOS or PDX for mud, and an LAS for the fast, dry courses. Three to four tires can easily get you through a full season and leave you plenty to train on next year. Ok, maybe you'll need two or three MXP's alone, as this it the tire you will turn to time and time again as you approach Saturday's event.