Saturday, April 7, 2018

Bontrager Gnarwhal 27.5x4.5 studded fatbike tire four month review

I've now had the Bontrager Gnarwhal studded fatbike tires in use for almost four months and have used them in all sorts of conditions: powder, firm trails, ice and crust. Though we had a nice winter only a few days ago, the snow is now melting rapidly and after this weekend I think I'll put on the summer tires. Thus a good time to write a little review.

The tire is in the new 27.5 fat format and I have them mounted tubeless on 80 mm wide Bontrager Jackalope 27.5" rims. This combo is probably as easy as a tubeless setup can get: The tires can be easily inflated with only an ordinary floor pump and they hold air even without tubeless liquid. The tubeless liquid is of course still necessary to prevent flats if the situation arises.

I really can't say that the 27.5 fat format is noticeably better on smooth winter trails. Some prominent names claim the the difference is massive, but I'm skeptical. I do think the root infested and rocky summer trails will show a bigger difference, though, and I will return to that topic after the summer.

The tires were studded up with the Schwalbe studs, since they were easily available and cheap. The Bontrager studs would have been about the same price, but were harder to get. The Bontrager studs are also a little shorter, but one or two tenths of a millimeter should not matter. The picture below shows them after three and a half months of use. As can be seen, the edges of the studs have lost a little of their sharpness.

Another option for studs would have been the 45NRTH concave studs. When new they give a little better bite, but seem to wear faster. Riding only on snow or ice does not really affect the studs, but harder surfaces, like asphalt, wear out the studs quickly. The 45NRTH studs are also quite expensive at around 50 cent per stud, while the Schwalbe studs are 10 cent a piece. With over 200 studs per tire this does have some relevance. The 45NRTH studs on a 45NRTH Dillinger 5 is shown below.

The Gnarwhal is 109 mm wide on the 80 mm Jackalope rims, mounted tubeless and with an average snow pressure (~ 5 PSI). That is about 2 mm wider than the Dillinger 5 on a 80 mm rims that I have measured. On really difficult snow I've used around 3 PSI and a few times on a harder surface closer to 10 PSI. Anything above that and you are not doing the fatbike thing right.

The floatation is hard to compare between tires, since you would need to perform systematic testing in identical conditions, and preferrably in a quantifiable way, to really say anything, so I'm going with the feel here. Clearly there is a lot less floatation than with the Vee 2XL on 100 mm rims (127 mm wide), a little less than Surly Bud on 100 mm rims (~114 mm if I remember correctly) and pretty much on par with the 45NRTH Dillinger 5 on 100 mm rims. The 27.5 does give a little longer footprint, though, which probably counts for a mm or two of width. The pattern of the tire is rather coarse, which gives better grip in powder, but there are marginal conditions when a coarse pattern like that can punch through a weak surface and start digging down. Snow is a medium with lots of variation.

I can only compare this tire with the Dillinger 5, since it is the only other studded fatbike tire I have experience with. There are other alternatives as well, and I would imagine that the 45NRTH Wrathchild is rather similar to the Gnarwhal. Compared to Dillinger 5, the Gnarwhal is a lot more aggressive tire, giving a better grip on all surfaces, including ice. The Dillinger 5 rolls noticeably better, though, and that's a feature which would have been very nice on the Ă…land ice trip.

To sum it up, I think the Gnarwhal 4.5" tire with studs is the obvious choice if you have 27.5 fat bike wheels. There are a few 4" tires, but I don't see the point for my use. The Terrene Cake Eater 27.5x4.0 probably rolls a lot faster, but where I live we have no groomed trails, everything is created through use and during a winter there are lots of situation when floatation is needed.

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