It all depends on the surface you're racing on. On sand or loose gravel, every added mm of tire width helps. In gooey mud, some would say added width helps. (But I think aero wheels help more in gooey mud than a few extra mm of tire width. Aero wheels shed mud better than box section wheels.)

As for discs, yes, they're worth it. Much better modulation. Much better power than canti's. And when they're wet, they still work great.

I doubt it. If wider tires are faster at all it might be because you can run lower psi. Tire tread, on the other hand, makes a big difference in cyclocross.

And brakes only slow you down. If you're faster on one type of brake than another something is seriously wrong.

The only actual test I've seen of that theory (though it was sand, not mud) was by CXMagazine several years ago. It wasn't much of a test, of course, but seemed to show just the opposite -- shallow rims were faster through sand than deep rims. They guessed that deep rims meant more surface area to rub/drag through the sand. Would mud be similar?

Yes! Went to Ritchey Megabites last season (from a mix of tubies and other narrow 33+/- tubeless rubber) for most general conditions. F@#$ing amazing. Nice tight beads on Hed Belgium hoops.

That being said, I believe pressure and technique trump tread and width at least in typical Colorado conditions. Now on the last lap or two your technique may be questionable (mine sure as hell is) and that is where width/tread really save your bacon.

Wider tires are faster in situations where a narrower tire knifes into the surface. For example, on loose sand or gravel, narrower tires sometimes knife into the surface and stop where tires 6mm to 9mm wider can float over the top and keep rolling. Rolling freely is faster than bogging down.

And brakes slow you down, but better brakes allow you to slow down for less time and distance. In other words, if your brakes are better, you don't have to start braking until later -- meaning you keep going faster (no brakes applied) when you would, with poor brakes, already have to be slowing down. If you've got better brakes, you can beat the guy with mediocre brakes at each and every braking point. If you're skilled, you can gain several feet every single time.

You said 4/5, so it may/does not really apply, but, since you are looking to get faster, there are rules about tire width.
https://www.ridecx.com/...onship-max-tire-size

Even if you don't plan on getting fast enough to race nationals, isn't it better to keep yourself beholden to the rules to really gauge your abilities?

As you can see, I was discussing gooey mud. Gooey mud has very different characteristics than sand. Sand doesn't stick to your wheels and accumulate. Gooey mud does.

The reason an aero wheel sheds mud better is that, with a box section rim, the mud surrounds the tire/rim inside and out and attaches itself. There's nothing to act on it to make it want to fall off the inside surface of the rim. It builds up into a large diameter donut that adds weight and can eventually bring the wheel to a halt. (This is why gravel racers carry paint stirrers with them -- to clear the gooey mud off their wheels.) With aero rims, the mud can't surround the tire/rim as readily and, for that reason, stuck only to the sides and tread, it falls away. It doesn't get a "grip" on the inner surface of the rim as it can with box section rims.

Oddly enough, I haven't been beat in a 'cross race by a fat bike with disc brakes all season.

Seriously, though, there are way too many factors for a blanket statement like "wider is faster" to hold true. My latest race I passed the guy just ahead of me when he pitted to switch from a cross bike to a mtb, presumably with wider tires. Despite a very sandy course he never caught back up to me, making me wonder why he pitted. (Flat, maybe?)

Yes, I acknowledged that twice in my comment. Still, the argument for deep rims in sand reads very similarly to what you laid out.

I love racing cyclocross in mud. If it's peanut butter I'm pitting my bike rather than hoping the mud doesn't stick. Every half lap some times. And my tires and wheels get pretty clean that way.

I remember a particularly muddy race in Belgium where Wout van Aert chose narrower tires that all of his competition to cruise to victory. I think it was one of his world's wins.

My understanding is that cx mud tires used to come in 28mm widths as well as wider. (Were the original green Michelin Muds 28s?) In the right conditions they would cut through mud and find some grip underneath. I don't know if anyone makes narrower mud tires any more, but I suspect that reflects a marketing trend rather than any actual progress.

Many of the CX courses here in the UK are all about grip. Almost immediately the whole course becomes a muddy mess where breaking, acceleration and just staying upright is a fight for traction. In these conditions cantis vs discs don't make a ton of difference but every little bit of extra tire width/drop in tire pressure is key. Occasionally though we will get a cold spell and the ground will freeze solid. This completely changes the equation with tire width becoming much less important than braking performance. So I imagine it matters a lot where you live and the course you race.

Personally I would never go back to canti's, or even mechanical discs for that matter, but I managed many years without problems. The nicest thing about hydro discs is that you don't get hand fatigue during longer training rides. I also found canti's required constant maintenance faffing.

Well, it's the wet season here now and all I own is a set of 32mm dry condition tires. I don't own anything for wet.

For dry or easy conditions I'm cool with 32's. I'm talking about bumpy, curvy, wet.

I also ride this bike gravel a good bit for training and fun. The fastest times in that area round here are often on drop bar 29ers and hardtails on the curvier sections. Road bikes with 28's on the straight sections.

I don't think the sport gravitated towards 32 because it's best, but because it's a rule at higher levels enforced to ensure the spirit of cross races. There's a reason the rule is 32 and not 42, I'd think. I'd assume that would mean it would make the courses easier.

If that's the case, how couldn't they be often faster? I could see specific conditions or courses meaning a smaller tire wins out. But not ones with lots of bumps, tons of corners, and not perfect terrain.

I just notice that dry or wet I'm in the smaller % of people for tire choice being smaller.

You really gotta separate gravel from cross to get the discussion you want here. jstonebarger's posts are perfect for cross related stuff. They are clearly speaking from cyclocross experience. I really agree with them saying there's too many factors for a blanket statement. That's why people show up to cross races with 4 sets of wheels. As you start getting towards higher categories, there's a certain level of homogeneity of riders, thus a corresponding similarity between the 'best' equipment for them.

If somebody has an 'aha' moment with much more aggressive tires, I'm guessing it's because they have more horsepower than handling. There's nothing wrong with that. Shore up your weaknesses. It's also possible they are finally able to achieve a lower tire pressure due to a larger tire. If people are passing you (a collective 'you')in corners and technical sections and you're getting them back in the straights, climbs and other power sections, then it might be time to try tires with more grip whether that's wider, more knobby, or lower pressure.

Gravel is primarily just finding the mix of comfort and rolling resistance that you're comfortably with. The small amount of grip needed is coming from lower tire pressure, not tread.

I feel that the best cross racers are using their brakes the least and/or doing the least slowing down so they are kind of a moot point.

Edit (there were a few posts while I wrote the above section): A discussion of CX tires without mention of pressure is not very beneficial. 32 mm dry tires in wet conditions is a recipe for disaster.

The tire width 'rule' is a pointless discussion in the USA. USAC does not have a tire width rule for cyclocross. It's a UCI rule that USAC borrows once a year for half of its categories. Even at a UCI race like Trek CXC, Jingle Cross, etc. the rule does not apply to you unless you're racing in the elite/pro categories. The other categories are run under USAC rules.

If you are looking for a single do-it-all tire, the Schwalbe X One all around is a solid option. It's going to measure around 35 mm on the average rim, it's low rolling resistance, it's a tight bead for better tubeless performance, the corner knobs are going to get you through most cyclocross racing except the really wet/loose stuff and the center tread is spaced tight enough that it won't be a bad roller on gravel.

Gotcha.

It's certainly a horsepower/skill discrepancy to a point. I'd say the ratio of horsepower to skill is probably 30/70.

I finish mid to front 1/3 of pack, but way back from the pointy end that gets the call ups and has the best skill/horsepower ratio.

I do what I absolutely can on the skill department, but I don't want to be slower simply because I'm too stubborn to try a tire or pressure or a tread though either. I even made my own set of PVC pipe barriers I can use at home or at the park.

Comfort wise, I feel like a couple courses here wet or dry beat the absolute crap out of me on the 32 tire. I'm not tubeless nor tubular. I don't want to spend money on wheels if I go disc at some point. I could at least move over tubeless ready tires if I use them now with a tube.

So, part of it is I can't get as low a pressure as the TL/tubular crowd. I'm 155lb and ran the 32's at about 25lbs my last race. At that pressure I pinch flatted on my next gravel ride when I hit a washout I didn't see in time to bunny hop.

Edit:
I have the Velocity USA wheels, an A23 I think. Not sure if TL ready or not.

Are you running latex tubes? If not, that would be an improvement in both rolling resistance and pinch-flat protection.

FWIW most guys I race with won't run tubeless under 25 psi for fear of burping. With latex tubes (at 175lbs) I race 'cross at 18-24 psi on either clinchers or tubulars. For gravel racing it'd be quite a bit higher, maybe 30-35?

Funny you mention that. I got fed up recently with a couple pinch flats in practice and on gravel and bought some latex tubes. And I'm pretty careful to hop or use skill to avoid a bad bump.

I was about to put them in.

I do need muddier tires though, narrow or not. The only tire I have now is specifically for dry, hardpack, easy stuff. Nothing good for wet.

Donnelly MXP, Challenge Baby Limus, or Schwalbe X-One All-Around should serve you pretty well.

Considering how my race ended at my last race of the year (flat and carrying the bike for a lap) I am debating running the Schwalbe's tubeless next year.

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I run 700 x 40mm Clement X'plor on my 2015 Crockett (disc) so 40 should fit on that bike. I really like this tire for all surface/gravel riding around here. Its great moving from paved, to gravel and the occasional single track. I haven't rode them in wet cross conditions so can't comment there but wouldn't think they'd be the greatest tire in mud conditions.

I really can't comment on if you should use your current rims tubeless. I have never had my hands on those rims (which appear to be tubeless compatible). The trick for cyclocross is a painfully tight fit when mounting tires. As I have mentioned on other posts, a WTB or Schwalbe tire on a Stans rim is really difficult to install, but burp proof. I prefer the Schwalbe tires over WTB because the WTB tires have a really square tread. Your corner knobs are always on the ground and you end up with casing where you want your corner knobs on off-camber stuff with square-ish tires.....or most tubeless clinchers on wider rims.

If you try some tubeless tires and it's not a total PITA to mount them on your rims, take them back off, clean the rims and rim tape, and put a few more layers of tubeless tape on. Repeat until you can barely get the tire on even when using some sort of lubricant like dish soap, furniture polish, or other tricks used for mounting tubeless tires. There's absolutely no reason you can be in the very low 20 psi range on the right combo of tubeless tire and rim. Getting the right combo isn't easy. Additional tubeless tape (or rubber rim strips like what Stans sells) helps you cheat that a little.