Normally, new bicycle tires really aren't that big a deal. They are simply another wear item, disposable, temporary. Much like a new chain and cassette. However, when you start talking about new tires for a fat bike, things change.
For one, the tires cost nearly a fortune at about $150/each for a good quality folding bead 120tpi model. Therefore, the idea of having lots of use specific tires hanging around which you switch between isn't really a practical option for most. More practically speaking, the benefit or conversely, the detriment of a specific tire style for specific riding purposes can be huge. Fat bikes are, after all, meant to be ridden in the snow. In order to most effectively ride in the snow or any soft conditions, tire choice is crucial.
Key concerns are float which is a component of the tire volume and pressure making for the biggest footprint possible and of course, traction as provided by the tread pattern. In the few years that I have been fat biking a lot, roughly a thousand miles a year on snow, I've used four different tire/wheel combinations on there different bikes.
I started out on a Charge Bikes Cooker Maxi 135mm front and rear hub spacing with 80mm rims and 4" Vee Rubber Mission 120tpi tires. The 135mm rear spacing meant an offset rear end which was limited to a 4" tire due to clearance. The offdet is used to push the wheel away from the center of the bike, gaining clearance for the chain as it passes the tire coming from the crankset. Being new to the fat bike, coming from riding normal MTB in the snow for a couple decades, the difference was amazing. By closely controlling the tire pressure to adjust the footprint the bike went really, really well. That was the setup that got us hooked on the fat bike discipline and we rode them a lot.
Last year we got new Borealis Yampa with 197/135mm hubs and 80mm wheels with 45NRTH Dillinger 4 120tpi tires. The rear end was symmetrical as with a traditional bike frame rather than being offset. This setup worked significantly better than the Charge setup. Of course, the bike weighed 10# less and the tires had significantly more tread. The wider rear end also meant that the bike could take up to a 5" tire. The Dillinger is a great all around tread pattern, fast and light but a little on the conservative side. The sidewalls are thin because the tire is so light, which means that if you ride them in dirt and rocks, they get threadbare. That said, I put about 1000 miles on mine, primarily on snow with some snowy gravel, and they still look near new with no issues at all.
I also put together a Salsa Mukluk last year which had 170/135mm hub spacing and a symmetrical rear. Unfortunately, it can't handle oversized fat tires. I built it with 100mm rims though and ran aggressive, Surly Nate 3.8" 120tpi tires on it. The wider rims gave a significantly larger footprint and with the more aggressive tread of the Nates, did very well in looser snow conditions. I found myself leaning toward that bike over the Borealis when the conditions were loose, despite the bike weighing significantly more.
We started this season out with the Dillinger 4 on the Borealis but also pulled out all of the stops and added HED Big Deal 82mm carbon wheels to the bikes. This dropped a fair amount of weight from bikes that were already lightweight. It really made a noticeable difference as well, in terms of rolling weight and spin up for the wheels. The conditions this season have been fickle, to say the least. We have not gotten that much snow yet to start with. The initial snowpack we had going, which had transformed into some very good rising, was greeted with a bout of warm and rain that turned everything packed down to ice.
In the past week or so we have started to get some small snow storms, which drop an inch or so at a time as well as some gusty wind, that blows and drifts the snow. Conditions tend to be good in places but loose in others. With that, I was ready to try something new, a little more aggressive and a little bigger.
Given the luck we've had with 45NRTH coupled with reviews from friends at the Village Sport Shop at Kingdom Trails in Lyndonville, VT, we decided to order some of the new, front and rear specific 45NRTH Flowbeist front and Dunderbeist rear. from Chris at the Bikeway Source They are beefy and the lugs are deeper and wider spaced than the Dillinger. The casing is a claimed 4.6", which is the largest volume tire that 45NRTH offers.
Out of the box, the tires look aggressive. Very moto like. An unscientific weight comparison by hand with the Dillinger 4 yielded exactly what you'd expect, they are heavier. The sidewalls also appear to be slightly heavier and more robust, which should help increase longevity at lower pressures. Mounted up, they are indeed wider. Not huge like the Bud and Lou on 100mm rims but bigger. On the trail, they roll well and hood up very well. I'd dubbed them the Garden Weasel, a throwback to an old reference my buddy Wick made to the WTB Velociraptor when they first appeared, in the 90's. These things grab and with a more pronounced edge know, they corner better as well. I got into some loose, super technical snowshoe trail with about 6" of semi compacted snow the other day and was blown away by how well they hooked up at lower pressure.
Though I was concerned about the weight at first, I simply didn't notice it. Now of course, if you were doing a long, hard packed snowy gravel ride these tires would be less desirable than the Dillinger 4. But for riding snow, they are very good so far. At present I've only got limited time on them but so far, so good. Will see how the race goes this weekend.
I'll check back in once I have some more hours on them but at this point I like them, a lot, which is a good thing given how expensive they are.