Gravel racing on MTB

Hi champions.

I am having my first gravel race in a few weeks. As race is organized for the first time and I don’t have time to recon it all I decided to race it on MTB (I do not have gravel bike and I would rent it if I would choose so). I have some experience with MTB but I am definitely not world class. I have much more experience on road and I am one of the best amateur road cyclist in my country. So I have the power to compete with the best, but I am lacking some skills on loose terrain as I am newer to MTB scene. I am quite a technical type of guy and always study equipment what would be the best for race.
Race should include wide wariety of gravel terain; from fast fire roads to some xc trail tipe paths.

So here come my question. Which tire would you advise for gravel racing on MtB bike? I was looking at racing ralph(front) + thunder burt(rear) in 2.25 width. I have 30mm wide internal rims so that is why I do not want to go down to 2.1. Anyone running 2.1 width on 30mm rims?

I will also mount aero bars for faster sections and I am going with 38t chainring and 10-52 cassette so I will have great gearing range. Any other tips that you can give?

Thank you.

You’re limited with 30mm id rims. Maybe Aspens would be another good choice. If you have a dropper I’d remove it. Also run your suspension stiffer and utilize the forks/shocks lockouts. Narrow handlebars if you have that option.

You’re likely not going to be staying with the front group on a MTB as you’re at a disadvantage, but maybe you can hide in the pack for as long as possible.

2.2 Continental Race King Protection would be my choice. They test really fast on the drum at and they roll fast on pavement. I have a set on a Scott Scale hardtail that I’ve set up with a rigid front fork for gravel riding. What aero bar are you using?


I was also looking at that, but those ones have basicaly 0 side knobs. So that is why I looked at racing ralph for the front one.

I will use generic aero bars. I do not know what brand they are.

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Gravel tires don’t have/need side nobs per se. Gravel for the most part is by far much more straight than MTB trails. You won’t be railing corners with a gravel setup, this is not an XC race. So you will need to ride differently and optimize for speed on open roads/gravel.

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The first clarification necessary, in my opinion, is about the terrain. You wrote “fast fire roads” which suggests you’ll be racing in the US. I did note you wrote “one of the best amateur road cyclist in my country”. “Gravel” is different things in different parts of the US let alone outside of the US. Regardless of additional specifics, working with the brief you gave…

The “xc trail” paths don’t necessarily mean technical-I-wish-for-full-suspension, but then again you will probably have at least front suspension since you’ll be on an MTB. For this, do you really need 2.25 or even 2.1 for what you’re suggesting is a course with hyperfast segments (“aero bars”). Because you presumably have at least front suspension, do you really need the cushioning that comes with the increased rolling resistance of the massive tires? I run 47mm (1.85) on 32mm (outside) width rims without a problem on my gravel bike that I often ride as an MTB on trails around Switzerland and Italy. I’d go with 47mm at the most and smaller if possible, which is probably safe but I don’t know.

I can’t imagine why you’d need a wide knobby pattern. A far tighter pattern will be better considering the glimpse you offered in the terrain and the expectation of speed. Also, considering this is a gravel event and not an MTB event, I don’t think you need the additional traction of wide knobs. My WTB Ventures in 47mm provide me great traction on highly varied wet and dry terrain save thick mud, which I rarely encounter, and decent traction in snow.

That you mounted aero bars and yet have a 38t front, even 38-10, also suggests to me something is out of whack with the gear selection. If you’re going to run aero bars because segments are so fast, I’m guessing you’re going to run out of gearing. I run a mullet setup on my gravel bike with a 42t front and 10-52 back. At high speed on pavement or downhill, I run out of gears, which is ok because at that speed I’ll rest or concentrate on not sliding out.

As for side knobs, the need or lack of need depends on terrain and course. Depending on your course, you may or may not have tight or even less than wide turns in loose dirt/rocks/surface gravel on top of hardpack dirt. No, you won’t be railing but cornering characteristics matter, again depending on the terrain. Even small knobs, possibly imperceptible to a mtb’er :smiley:, can matter a lot.

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Thanks for explanation. I am really new to gravel racing and I am very happy to get any kind of advice. So to reply to you:

That is not correct. I am racing in the EU. I just gave some kind of comparison so the people can understand variety in the terain. Gravel in the EU is much different than gravel in the US as I was able to hear from other people.

I talked to some people that know some parts of the course and said that some parts of the course are forest paths that include roots and rocks. And those parts of the route are not in the comfort zone of the gravel bike. But as I can understand the more skils you have on the bike easier it would be. But the course is definately not easy. It is 270 km long and has 5500m of elevation gain.

I think I will run out of gears on fast parts. But aero bars are more for efficiency than pure speed. On that long of a course every W saved will come handy at the end. Also some climbs should be ultra steep. That is why I opted for smaller chainring. Maybe I will consider 40t+ chainring.

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Agree, gravel in Europe is different than in the US, as I’ve heard many times (and I researched after hearing Coach Jonathon’s comment that gravel is riding on poor quality roads). My questions were based on living in Europe and riding “gravel” in Europe.

It’s helpful to see more info. Based on the distance, it’ll either be a really long day+ or it’s a stage event, and I’m thinking the latter because you didn’t mention hauling stuff needed for such a long go. 270km on trails is a big day (plus), not to mention the 5500m (18000+') of climbing. This sounds like a 2- or even 3-day event, but it could be a whopper of a one-day go (pre-sunrise to post-sunset, obviously).

I’d consider the need for tires for the forest paths “not in the comfort zone” of a gravel bike with the speed and comfort of the rest of the course. If you think that you’ll spend adequate time in aero to make the bars worthwhile, consider the watts lost from the bigger / knobbier tires on those “easy” sections, which you suggest will be considerable (enough to get aero). (Also not mentioned is the potential negatives of suspension potentially eating your watts.)

On the climbing, depending on the terrain of the steep climbs, a 40-52 is probably adequate considering your road fitness, but bear in mind your road climbs are rarely 15%-25%, and your hints suggest you’ll have 15-20% climbs with kickers going steeper, common for mountain trails here. Such climbs are likely if you’re doing a Jeroboam or Gravel Epic or Tortour type course. By the way, my current tire of choice mentioned above works good on 18-25% gravel (I have an about 1km climb I do repeats on near home), so again, you may not want big knobs. But, the 38t may work well to spin your way up the steep climbs and to stay away from the 40rpm churns.

Anyway, it’s all food for thought as you find the answers that work best for you. Good luck and have fun!

I would check with the organiser if aero bars are allowed, they’ve been banned in some group events I’ve done.

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Ah yes, the XC MTB race masquerading as a gravel race.

For this my wife and I have used full suspension scott sparks with the twin loc system, plus 50mm Maxxis Ramblers. ZERO trouble keeping up with folks on gravel bikes.

I’d keep the 38. I can comfortably settle in at 24mph in aero position on my scott spark which has 34t & 10-50 cassette. I can spin up to 30mph. If I’m approaching 30 mph, I just tuck harder though otherwise it’s just a massive waste of energy in a race like you’re doing.

You’re safe running a much narrower tire on that i30 rim. I’d go as low as 42mm. The limit you’re going to hit will be the tire shape and the rim’s maximum pressure tubeless. There aren’t many great tires in the 42-50c range but I’d consider some Schwalbe G-One RS in 45; Rene Hense in 48, Tufo, and Conti Terra Speeds 45. The Pirelli H tires don’t look bad either, but it’d need to be dry and clean.
I’ve got the Terra Speeds in 38c and the Race King Protection 2.2… I don’t think the current Race Kings roll as well as the Terra Speeds, but they corner much better over loose stuff even on pretty dense crushed limestone powder. I think you’d see the same with the Schwalbe Thunder Burts vs RS, but the RS look better for cornering than the Terra Speeds. If you want knobs, I’d go MTB tire or Rene Hense

The main disadvantage of a mtb vs. gravel bike is the aero penalty of flat bars (in my opinion). You can’t be in aero bars while riding in a group and you will be burning more watts sitting in compared to folks on drop bar bikes.

I raced gravel on my full suspension spark RC for a couple years before buying a gravel bike. I could race at the pointy end of my age group and even managed a couple podiums. You get a lot of “I can’t believe you are doing this race on a MTB”, but it’s really not that much of a handicap on many courses. I’d typically run 44mm gravel tires and the bike had full lockouts, so it’s basically rigid flat bar gravel bike with suspension when I wanted it. I always ran a 38 chainring (biggest the bike would allow) with 10/50 eagle. There are some courses where that gearing isn’t ideal, but I don’t think I ever got dropped from a group from being spun out. There are some tactics that come into play also, you really need to stay sheltered in the group. Once you hit the wind, the disadvantages of the MTB are magnified. You will crush any technical sections, so that’s always fun.

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It is a one day race. Start at 6am and I think it will take me around 10-11 hours to get around. So I really need 1 set of tires to do it all. That is why my decision would be to go with a bit more profile on the front for grip and sleaker tire in the rear for speed.

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I am also going with the spark. It is what I have at the momment and when suspension is locked it is really stiff :smiley:

I will wait with baited breath to hear how this goes. I think you’re set up very well.

I swear up and down that suspension is underutilized in gravel racing. All this talk of vibration damping… pshhhh… give me 40-80mm plush travel that I can lock out whenever I want.

Give me 50mm-2.2" tires with perfectly smooth center and some side knobs for when I want to lean the bike over and corner like a MTB’er. Don’t let those knobs touch the ground any other time.

Anecdotally, my wife and I did a “casual” team gravel ride in Patagonia, AZ. It was truly gravel roads. Some washboarded, some glassine. She was accidentally putting the hurt on a relatively equivalent rider on her team. Her teammate was on a $8k gravel bike and Michelle was on a $8k Scott Spark. It was a non-technical route. Not even any single-track or double-track. All truly hard dirt, and gravel roads among wheat fields.



One more thing to conisder - If you’re looking at tire data, keep in mind that you need to subtract about 4w from from their MTB test @35psi; 3w from a gravel tire at medium pressure; and none from a road-tubeless to get an apples-to-apples number from BRR because of the tube they use. Knobs cost about 2w extra, but its hard to tell.

Very much depends on the trail quality. If there are going to be chunky descents, I’d go with a MTB tire. Conti Race King Pros are fast and have good flat protection. I’ve ridden them for Leadville, White Rim and a chunky gravel course in Idaho. Very good for conditions like that.

If the trail is smoother, I’d go with a gravel tire, but on the wider end of the spectrum like 45-50mm. Panaracer Gravel Kings come in 50mm. Can get the SK plus for added flat protection.

Youtube is your friend: search for the name of the race and usually someone with a Go Pro has done it.

And if I were you’d I’d talk to people who have done the race. E. g. there is an XC marathon race here in Japan (100–120 km), and at first glance the course is tame. But you encounter a lot of large, fresh rock in some areas with sharp edges. So veterans of this race recommend running tires with thick casing and to take the necessary precautions on the downhill — you can make up a lot of time when you let it rip, but even if you are an excellent bike handler, you are running the risk of crashing or slicing open one of your tires.

Tire choice really depends on the terrain, and I don’t know what the terrain will look like (your description is too vague). And base your decision on a virtual course recon and talking to other athletes.

If I hear gravel race, running a Racing Ralph in the front sounds like overkill. But I like Racing Ralphs, they still roll very quickly, and if you are either not certain about the terrain or your bike handling skills, they are a good choice.

Alternatively, you could run Thunderburts front and rear or even run proper gravel tires that wide enough. E. g. Schwalbe makes the G-One Allround in 29" x 2.25". I’d also strongly consider running tire inserts.

That sounds too narrow to me, and the gain isn’t that big, I think.

If aero bars are not permitted, and you really want that forward lean for aero gains, double or triple bar tape two 100mm sections in the real estate on your flat bars remaining between shifters and stem to rest your forearms on.

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You can get most of the aero benefit by just putting your hands there (up against the stem in the center of the bar) and getting low. It’s a bit safer than IAB position with just arms resting there. I can’t remember if it was specialized or someone else, but I remember someone doing windtunnel testing of different positions on a MTB (regular, mini aero bars, hands on top of fork crown, etc.) and just having your hands centered, elbows in, with a low position was surprisingly aero. The bike (particularly bars/cockpit) are still aerodynamic disasters, but you can get the body position pretty decent.