Challenge Tires “Gravel Grinder” 38mm Tires

Editor’s Note: In the merge with Gravel Grinder News we knew there was a wealth of reviewed tires, bicycles, and components that might be a good resource on the new site here. With that in mind here is a condensed version of a review that originally appeared on Gravel Grinder News. Any updates on these reviewed products will appear at the end of the article. Thanks and Enjoy!

Challenge Tires
The Challenge Gravel Grinder 38mm tire.

Challenge Tires “Gravel Grinder” 38mm Tires; Reviewed by Guitar Ted

Another of the new gravel tires for 2014, the “Gravel Grinder”, is a tire introduced to us privately by Challenge Tires back in February at Frostbike. Challenge has sent over an early production version of the vulcanized Gravel Grinder 38, which isn’t like the hand made, “open tubulars” we’ve tested here before and which have been known to have had issues. This is a vulcanized tire and Challenge assures us it can take the abuse.

P1070392Suggested pressure rating range is 45psi to 80psi. This is not a tubeless rated bead on the casing and Challenge strongly advises against trying these in that manner. Challenge claims a weight for these at just over 400 grams a piece, but our two samples arrived here weighing 370/380 grams, which is a light weight for this sort of tire in my opinion. The casing is supple in the hand and the tire fit snugly on the HED Ardennes+ wheels I have here on my Black Mountain Cycles bike. The tires have a nice, rounded profile on these wheels, as shown to the left here. Once again, they measured out right at 38mm each at 45psi.

First Impressions: The Challenge Tires Gravel Grinder is a fast feeling, smooth rolling tire, which should be no surprise, given the minimalistic tread in the center portion of the tire.  However; it also has a very smooth, damped feel while riding most surfaces, and this was a nice surprise given that I was unsure what to expect with Challenge’s vulcanized casing technique used on this tire.  The ride showed me that a light, wider tire is easier to spin up a long, grinding climb, and having that tire be supple really helps keep the bike floating up and over the rocks instead of spitting them out and pinging around off them, which I find can really upset the rhythm of a climb. Going down I wasn’t sure that the side lugs were helping me stay stable, but these tires did stay underneath me better than some others I’ve had on this bike. On the sandier stuff, these did not show me a tendency to knife in and wash out, so that was another nice surprise here.

Mid-Term Update:  I had been running the Gravel Grinder tire on my Black Mountain Cycles “Monster Cross” rig. I did a few more gravel rides and a whole bunch of commuting. The tires were pounded through pot holes, cracks, and fissured concrete along with my normal curb hopping. This was all done in an effort to try to expose any weaknesses in the Gravel Grinder’s casing. However, I could not find any issues after three weeks of this abuse. So, onto the next phase of testing……

Challenge Tires
Challenge Tires Gravel Grinder 38’s mounted on the Raleigh Tamland Two

I switched the Gravel Grinder tires over to the Tamland Two and the idea here was to contrast the feel of the tire with the Nano 40‘s which had been on the Tamland previously. I ran the Gravel Grinder tires at the same 45psi rear/40psi front that I had been on the Black Mountain Cycles bike. Once again, the lack of vibrations and gains in smoothness were things I fully expected to find, but the thing here is that the Gravel Grinder has a better damped feel than the Nano 40- or than most any other tires I’ve tried.

The reason is that the casing is a pretty supple one, even though it uses the coarser 60TPI threads. (Editor’s Note: The hot patch on the pre-production sample was incorrectly stating a 120TPI casing) Despite the non-”Open Tubular” construction, I would give these a high rating for ride feel. Combine that with the smooth, fast rolling tread design, and you have a great tire for a faster paced ride. But what about those side lugs? Do they actually help to stabilize the tire in looser conditions, as I thought they might? Well, the answer is “yes“, but not for the obvious reason. You have to look at the Gravel Grinder a little more closely to figure out why it handles like a bigger, wider tire.

The Gravel Grinder is a true 38mm wide tire, and has a great volume on both the HED Ardennes+ and the stock Weinmann rims on the Tamland Two. The profile of the tire is a shallow “C” shape, and those side lugs? The side lugs sort of make the tire act like a wider tire than it really is. All this “width” is helping the Gravel Grinder roll up and over gravel rather than knifing into it and washing out. The feeling is more stable, more like a 1.8″ 29″er tire, than a 38mm one. Those side lugs effectively act like little “outriggers” more than they actually grab rocks and terrain, as you would initially think they would. To wit: You still get a little lateral “looseness” on the deeper, loose gravel, but it’s more predictable and feels more controllable than a tire of this size should feel.

So the tire is fast, supple, and seems tough enough with a great, controllable feel in looser gravel.


Final Verdict: I won’t waste any time here- The Gravel Grinder tire is a winner. It stands alongside the Clement MSO 40mm and 32mm tires as being, in my opinion, the best gravel road riding and racing tires you can get now. The Gravel Grinder by Challenge, with the vulcanized construction, is tougher by far than their previous samples that we have tested. The Open Tubular, handmade construction used by the previous tires is certainly awesome in ride feel and has no peer, when they hold up. That was the trouble with those samples- they just were too inconsistent in how they worked on gravel roads. Not so these vulcanized Gravel Grinder 38’s.

The tire wear has been impressive as well. The diamond shaped, file tread has held up well, despite lots of paved commute miles. Certainly, they do show wear, but nothing I would deem as out of the ordinary. In fact, I keep looking for something to come apart, show scarring, or excessive wear, and I am just not seeing it with the pair I have on test.

The ride quality is on par with the best of the rest out there and maybe a tic below that of the handmade Challenge tires, so I cannot really fault the tires there. Paved riding is fast, and if you find that you need to cover a lot of paved miles to get to gravel or dirt, these tires are definitely not a hindrance to getting out there. They buzz a tiny bit, and they sing on hard pack, but I found neither to be annoying in my opinion.

Even the chunkiest gravel was handled well by this tire.
Even the chunkiest gravel was handled well by this tire.

The width is spot on for what most folks seem to want, and the tire has the toughness and performance necessary to be fast and reliable. What’s not to like here? Well, I will take Challenge, (and other tire companies making tires for “gravel road riding”) to task here for not getting on the stick and making tubeless tires for gravel road riders. Yes……it is a tiny niche market within cycling, but in my opinion, there shouldn’t be any performance tires made in 2014 and beyond that are not tubeless ready. The wheels and rims may be scarce now, but one can always fall back to using a tube. One cannot always reliably use a clincher tire tubeless. It seems to be a simple solution to all the hand-wringing companies do when asked about tubeless  tires. Some will point to the “lack of standards” and I would counter with “UST”, but maybe there is something to that.

All that aside, for now, the Gravel Grinder joins the short list of tires specifically aimed at gravel road riding that are actually worthy tires for the purpose. That’s probably a good thing for Challenge Tires, considering the cheek in choosing this tire’s name!

Long Term Riding Gravel Update: As of this writing the Gravel Grinder tires were just replaced by a new set of review tires, but these tires will definitely be in the rotation for special events and for faster rides. The wear has been minimal and as stated, I have found no significant issues with the construction of this particular Challenge model.

Note: Gravel Grinder News received the Gravel Grinder tires at no charge for test and review. We are not being paid, nor bribed, for this review. We will strive to give our honest thoughts and opinions throughout.

Discuss and share your questions or thoughts about gravel bikes on the Riding Gravel Forum.




Author: Guitar Ted

Guitar Ted hails from Iowa. Home of over 70,000 miles of gravel and back roads. An inaugural member of the Gravel Cycling Hall of Fame and Co-creator of Trans Iowa in late 2004- Guitar Ted has been at the forefront of the growth of gravel events and riding since then. Creator of Gravel Grinder News in 2008, he produced the premier calendar of gravel and back road events. GT joined forces with Riding Gravel in late 2014.

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28 thoughts on “Challenge Tires “Gravel Grinder” 38mm Tires

  1. Been thinking about these tires, good to hear such a good report. Last year I was impressed with the Contiental Cyclocross speed 35mm tire for gravel/pavement/early dry cross racing. This year I’ve tried the Specialized 38c Trigger tubeless on HED belgium + wheels, so far so good, but I think these Challenge tires with a more supple casing and a pair of latex tubes might ride as well or better then the triggers and not be any heavier, hmm. What’s better a supple casing but tough tire like the challenge gravel grinder with a pair of latex tubes, or a stiffer heavier tubeless ready tire like the trigger 38 setup tubeless, my guess is the actual weight probably equals out or isn’t much difference between the two.

  2. Previously my go-to tire for mixed surface rides was the Clement LAS, which has a tread very similar to what is pictured above, however they wore extremely fast on the rear with any decent amount of pavement riding, and for only being 33mm there were extremely fat on A23 rims.

    The Gravel Grinder sounds like everything I loved about the LAS, but in a bigger package with better wear characteristics. Can’t wait to throw a pair of these on the bike for the events I have coming up this spring.

  3. Ted – would you recommend the Challenge Gravel Grinder 38’s for DK200? How about vs. the Clement MSO’s? Any experience with either tubeless?

    1. Steve: The Gravel Grinder 38’s have a really supple, thinner casing, so…….yeah. For DK 200 riding? Maybe, if you don’t mind taking chances. I cannot speak to their tubeless capabilities, although some readers have reported successful conversions using the Gravel Grinder. I do know Challenge explicitly warns against using them that way. The MSO’s, in the 120TPI variant, seem to fare better being switched to tubeless use than their 60TPI model. I haven’t done it myself, but again- you’ll get varying reports on how that tire fares. I would choose it over the GG for the DK200 though, simply from the standpoint of durability. I have heard that the MSO will deal with the Kanza rock better than many other lighter weight class tires do. Many folks actually will use touring tires with puncture protection, like Schwalbe Marathon series tires and the like, and they have fewer flats, but you do pay a weight penalty.

    2. I roding some of the DK200 roads for 3 days not too long ago, some 170 miles, and I did not have a single flat on the Gravel Grinders. I had them mounted on Belgium + rims, running them at 40psi (I weigh 130lbs).

  4. Thanks GT. Have you taken a look at or had the opportunity to try out the Specialized Trigger Pro 2Bliss 38’s. These look like a nice gravel bike tire designed to be tubeless, offer some flat protection and what looks like a pretty fast rolling design…

  5. Comparing the 700×38 Gravel Grinder, the 700×40 120tpi MSO, and the 700×40 120tpi Maxxis Rambler, which tire would be wider on something like a Velocity A23 rim?

    If it helps anyone, my measurements for a Mavic MA-2 rim, are
    700x35c Continental Cyclocross Speed – 32-1/2 mm
    700x38c Challenge Gravel Grinder Race 120tpi – 36mm

    1. Alex, your questions could be answered by searching in the forums, most likely, but in my experience, A-23’s yeild “normal” widths on tires, so it shouldn’t take much thinking to answer your question. A-23’s aren’t all the wide a rim internally. Gravel Grinders will be about what they are claimed as will the other two tires.

      You really need to “open up” the inner rim dimensions to 22-23mm before you start seeing much difference.

      1. Hey Ted,

        Comparing the Challenge GG & Maxxis Rambler. Thoughts on which one would win out (not taking into account the Maxxis issue with mounting tubeless)?


        1. Phil L- Can we agree that tubeless compatibility, engineered in to the tire from the start, is a huge advantage? Then it would be no contest. The Maxxis wins hands down. However; if you do not believe in tubeless tire advantages, then it gets more dicey.

          I like the Challenge Gravel Grinder tire’s lateral stability over that of the Rambler, so that would likely sway me in its direction if both were tubed only type tires. In real world comparison, I still believe tubeless tires roll more smoothly with less rolling resistance, so the Gravel Grinder loses by technical knockout.

          1. I just picked a set of 120tpi for a the Chino Grinder. I liked the road feel on the tires for the first 2 rides, both in the 40-50 mile range. Then the random issues started. Picked up a nail on the 1st ride. OK, normal karma. Then on the second ride, picked up a thorn. (1 tube and more issues getting home) So, they feel great, and maybe I am just on bad luck, but, maybe the thinness of the casing is something to think about. I am concerned on doing a big rough ride on them, over some pretty rough roads.

          2. Myself and a friend purchased a set of the Comps for a gravel grinding weekend. Multiple flats for both of us almost exclusively do to punctures from small thorns and other road stuff that my Schwalbes would have not flatted on. When the tires were not flat, they were pretty good…but the multiple flats that we both had tells me they are not very puncture resistant at all. Disappointing, because otherwise I liked them.

  6. Hi Ted, I am looking for a tire that would work as an all-rounder, that performs decently also on some easy single-track and is robust enough to take the abuse, even though I don’t disdain a smooth ride on pavement and hard pack and is somewhere between 38c and 40c. (maybe I’m wanting too much? :))

    I am not planning to go tubeless just now so I was looking at the clinchers. I was now left with the Maxxis Rambler 40c, the WTB Nano Race 40c (can’t really find the Comp anywhere in my country) and the Challenge GG 38c. But I can’t really decide between the three, and I don’t know if there is any other solution that could work for me. I am not particularly concerned about the weight. It’s for a CX bike with fairly wide clearances that I’ve set up a little bit more on the “gravel side”, so 40c it’s the biggest I can mount: I have tried the Surly Knard 41 and was left with way too little clearance, so I also have to consider the width issue.

    It would be great if you could give me some suggestion! Thanks!

    1. Louis, I might suggest those Nano 40’s, and I would strongly suggest them if your rims are on the narrower side, (say less than 21mm inner width), which would keep the overall width in check. That said, your comments about the Knard 41’s being a bit too plump concern me, so I might actually go with a Clement MSO 36, even though it is rated tubeless, it can be run with a tube.

      Hope that helps.

      1. Thanks for the reply! Yes the wheels are 19mm. I think I would try the Nano Race and return them for something smaller if I see they are too big. However, 38c will definitely fit, 40c are a bit of a hazard but I’ll give it a try. Heard about the Clements too but I’m not sure they distribute in Europe, I looked for them but without any success.

        The only thing I was concerned about was going for the Nano Race instead of the Nano Comp (which seem to be sold out everywhere I looked) and the loss in durability that comes with the increased TPI rate (though it’s 60 TPI, which, for what I understand, it’s still pretty low)

      2. I see now that I also have the TCS option for the Nano and run it with a tube… same TPI as the Race but maybe more durable, or exactly the same? Hmmmm…

  7. just another data point:
    Challenge Gravel Grinder 38 on a 17mm internal width rim measure out to about 37.5mm casing width and 38 for the side knobs.

  8. Been running Maxxis Rambler EXO/TR and Silkshield TR 700*40.
    Requires a some care to mount on my No tubes rims.
    First inserts an inner tube and seat the tires. Than open the “bond” at one side and take out inner tube.
    Insert tubeless valve, inflate and tire will seat.
    Did not work with compressor on my wheels. But this method works. However, the rear tire drop pressure far to quick sadly.

    Clement X’plor MSO tubeless (36mm) was not that funny. Actually disappointed in this tire. Not only the most heavy tire of the bunch, also the most boring.
    I prefer Schwalbe G-One 35mm tubeless over these.

    Hutchinson Black Mamba CX (34mm) tubeless is the fastest of the bunch and has tremendous grip.
    Part from that, very easy to find sweet spot pressure for speed and comfort.
    A clear winner if you can live with a less fat tire…
    A pity they do not have this in a 40mm version.

    SInce Challenge latex inner tubes are so great, i feel using them instead of tubeless is actually more than ok.
    I simply must use inner tube at my rear (Maxxis Rambler Silkshield) since it drop too much pressure tubeless mounted.

    Looking forward to see how WBT Riddler 45C stand up to the competition.
    Not very light, but it would be nice to try it out.

    1. @weed grinder- I don’t know enough about your bike, riding style, or expectations to say. For me and my purposes? No, I wouldn’t choose this tire for my 29″ers.

  9. Hello Ted,

    Based on this review I’ve been riding these with latex tubes for the last two seasons. And I found it to be a great combo. Only one flat (pinch @ 45km/h hitting a rock with only 35psi in the front, so can’t really blame the tyres nor tubes).

    Am considering the 35mm (tubed, but set up tubeless) or 38mm (tubeless compatible) Panaracer Gravel King SK. How would you rate the Panaracers compared to the Challenge?



    1. Oh, forgot. I ride the race version, so 120tpi. What is the thread count on the panaracers? Their website isn’t very helpful there.

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