Fat Tires On Gravel: From Krampus To Gryphon (Intro)

This post will be the beginning of a series on 700c fat tires on gravel. I mean really fat tires, not 2.4's or 2.6's, but really fat tires. The so-called "29+" tires. Originally these were 29" X 3.0" wide tires and they were pretty much the brainchild of the nutbags at Surly Bikes. Originally seen on the Krampus model in 2012, this tire size revolutionized my thinking about what might work in certain situations on gravel roads and dirt roads. 

This will be a mini-series on the blog here. My intentions are to show my personal experiences and takes on 29+ sized wheels for gravel. this is not going to be a comprehensive look at 29+, nor is it going to encompass everything about 29+ and gravel riding. However; I think you might find it interesting to know why I think 29+ is a good choice for gravel and what my thought processes and experiences have been up to this point. 

My intentions are to show my revelations regarding 29+, my experiences with 29+, where that led to gravel riding on such big, heavy tires, and where I have traveled on my way to getting what I consider now to be a "proper" 29+ bike for gravel. It all started with Surly's Krampus model in 2012, and it ended up with my Singular Cycles Gryphon Mk3 in 2023, over a decade later. 

29+: Surly's Last Great Innovation: 

This all begins with Surly Bikes' surprise revelation during the Summer of 2012 that they would be introducing the Krampus which was a hard tail MTB with corpulent 29" tires. Actually, if we wanted to be really technical about things, the 29+, three inch wide Surly Knard tires ended up being a bit over 31" in diameter, so quite a bit larger than 29"ers in reality. But who's measuring that?
 

I got to ride a Krampus at the 2012 Interbike show. It was the highlight of the show for me.

I was able to test ride that bike with the new 29+ Knard tires at Interbike's Outdoor Demo at Bootleg Canyon that year. I was very impressed. I stated back then that, "I think the Krampus is the ideal platform for longer, really rough road/back road/fire road riding in a bike packing set up. The tires should exhibit lots of grip, and with the volume, lots of suspension. Plus, a bit lower angle of attack should smooth out bumps even more than a typical 29"er."

I was thinking in mountain biking terms at the time, but all of that applies to gravel as well. The attributes of the 29+ tire were all well suited to gravel travel with the exception, perhaps, of the weight. The first Knards were pretty light though, so initially, this seemed like a viable way to go for gravel at some point. 

And it did.

But first we need to go back a bit further to when fat bikes came out. It wasn't completely obvious then, but in 2011, fat bikes were found to be "okay" at gravel travel. their big footprint was a stabilizing force over what could be described as a surface of stony ball bearings. Skinnier tires plowed through this and hunted for a stable passage through the rocky bits. But a fat bike tire just cruised over the top of the rocky chaos and smoothed out the ride so well that many still choose a fat bike to this day for gravel travel. All that despite the heavy, ponderous wheels. 

An all fat bike gravel ride in 2012

 While fat, voluminous tires were found to be pretty good at some things concerning gravel, they were a pretty heavy wheel back in the early twenty-teens. You rarely saw anyone running tubeless because of the lack of tubeless options, and therefore the wheels were really heavy. It would then make sense that a middle ground, something between fat tires of 3" plus and mountain bike tires for 29"ers would be a nice thing to try. 

In steps the Krampus, and later, the Surly ECR, a purpose-built bikepacking bike for off-roading. These bikes featured Surly's Knard 3.0" X 29 inch diameter tires which were a revelation in terms of what might be possible. Early on, the wheels and tires Surly brought to bear on the MTB world were repurposed as "Summer Wheels" for fat bikes, turning those bikes into multi-purpose, all-terrain vehicles. 

Bikes like this Borealis were early fat bike conversions for 29+.

I had the chance to ride a Borealis fat bike outfitted with the 29+ wheel format and I was blown away by the bike's capabilities in varied terrain. However; I was still stuck on the thought that this format was more of a mountain biking thing. I wasn't focused on the possibilities for gravel riding at that point. 

29+ is fantastic for mountain biking, but the wheel size is limited to those who ride a medium on up, in practical terms, so the proliferation of 29+ wasn't as quick and all-encompassing as Surly and a few other brands who bought into the idea were hoping that it might be. Swapping out fat tires for 29+ in a fat bike was a thing for a hot minute too, but many were put off by having to deal with an extra wheel set and a pair of expensive tires. So, the idea never really caught fire like 29"ers, fat bikes, or gravel bikes which came later. 

The 29"er-ized Mukluk in 2012.

 I actually experimented with a 29"er wheel set in my 2011 Salsa Cycles Ti Mukluk back in 2012, but that idea fell off in importance to me because it was really "just another 29"er" at that point, and not an ideal one from a geometry standpoint at that. So, it lost interest with me fairly quickly.

However; there was one thing that happened at an Odin's Revenge which made me think that I needed to revisit that extra wheel set for the Ti Muk. That will be the next installment in this mini-series coming up in a week. Stay tuned!