Fastest tire width for cyclocross racing when UCI regulations do not matter?

At the moment, I am building a new bike. The frame is a Vitus Energie Evo. This frame is in a way similar to the Specialized Crux, as it is actually a cyclocross frame with tire clearance up to 47mm. The purpose of the bike is: fun and speed.

It shall be ridden with high speed on the local trails and hunting down some strava KOMs in the woods. Nothing techncial, but 85% off-road. No big gravel chunks, just European woods with minor roots and fallen leaves. Sometimes bumby, but a lot of double- and single-track trail with sections of sand or mud wirth very short, punchy climbs. All in all I would say it is similar to a cyclocross course, just without running parts and hurdles. As it has some tight curves out of which rapid acceleration is required, a cyclocross bike is probably the fastest bike for such a track.

What do you think is the fastest tire width, if UCI regulations do not matter?
The bigger the better? In my opinion, wider than classical 33mm is definitely faster, but at some point the bike feels sluggish. Of course weight and aerodynamics (if that matters) also are negatively influenced at some point.

At the moment I am torn between a 40mm tire (with tire inserts) and a 45mm (without inserts). The widths are actual measured widths. Quite low profile in the middle, some higher shoulder knobs on the side. From my feeling, I would not use anything larger than 45mm, because it feels indirect and sluggish. Nevertheless, I do not want to exclude that a 50mm tire could theoretically be faster?

There are many tests concerning rolling resistance, but if you talk about off-road behaviour there is a lot more to it than just some numbers generated from a rolling drum. Did anyone experiment with this or has some anecdotal experiences?

To make it more tangible. We talk about such surfaces:

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I think a cross tyre is faster, but you get less fragile tyres if you go to gravel/mtb tyres. Which means, you can just smash into roots and rocks, instead of having to be careful, which might be faster overall.

However when its muddy, I find wider tyres to be quite a bit slower than typical cross tyres.

There is likely not a single tyre that will be faster in all conditions, even without sticking to 33mm.

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With “cross tyre” you mean 33mm width max? I highly doubt that 33mm is faster than 38mm (and bigger) because of the lower pressures you can run with bigger tires. But still, I do not know for certain, just my personal feel.

I would think a 38 or 40 mm tire with the correct tread for your terrain is probably the way to go.

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38 or 40’s and you’ll be good to go. Except for the mud picture, Specialized Pathfinder Pros would be an excellent choice for that terrain. Also consider the Goodyear Connector Ultimate….extremely versatile gravel tire and my current fave (but will probably run Pathfinder Pros for SBT GRVL this year)

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The Goodyear profile really looks interesting, thanks!

I tried the pathfinders before. Liked them on tarmac but not on trails. The abrupt transition to the outer knobs felt instable and annoyed me. I prefer tires with a smoother transition.

Definitely give the Goodyears a shot then…i love them. Been riding them for almost 2 years now and they are stellar. When I did The Rift last year, the route had just about every type of gravel in the world and they performed across the board.

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The short answer: everything being equal (which it never is!), I’d go for the largest tyre I could fit and still have enough clearance for however much mud I was expecting.

The longer answer: it depends (like it always does!). There probably aren’t many situations when a 33mm tyre will be your fastest tyre, but there might be a few. Very hard and road-like conditions on a pretty smooth course is one (I’m thinking about some early season events in warm weather around a park or similar), and sometimes when you get the ‘muddy on top but firm underneath’ situation a slightly narrower tyre can bite through a bit more (though tread and pressure play a big role).

When I raced last year, the X-One Bites were pretty good (33mm), ditto the G-One Bite (40mm, which was very much the limit for clearance with my cross bike). The Goodyears mentioned seem quite popular and are on my list to try.

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This is an easy answer…… the widest one.
A high end 2.1 XC tire would win on every course that’s not a road course or groomed path.
Last years WC was held on a beach. This years, the race lace was 26.5kph. The suspension gains alone would net a ton of watts over a 33 or 38c.

CX is a dumb /outdated speciality in a gravel bike world. Theres no reason to own a cx specific bike. Tom and Wout are riding bikes that not even Tom and Wout would buy. We have AL and CF frames now with BBs that allow for more than 33mm of time. Even Aero DB frames can take a 35mm tire now. They need to move to 38c.

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This is an easy answer…… the widest one.

Ok, but where is the limit? As written above, I could probably fit a 47c tire. Do you think that´s faster than a 40c tire?

It all depends on the course…horses for courses.

I think 35mm depending on the course would be fastest. Then again I own a dumb outdated CX bike so my opinion doesn’t matter. @jfranci3

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Having chased friends on CX bikes on my XC bike, I would say that smaller tires are faster as long as you aren’t grip limited…

Which is to say, it depends on the course.

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I was answering the UCI question. I’m seeing 45mm for that frame - and I’d stay with that limit for mud clearance. If it’s tight, the mud will sand your paint off the seat stays or the sidewall of the fat tire will hit the seat stay. You’ll also mess up your shoes when the front tire hits them.

For everyday use, you need to consider the specific tire too. If you’re hitting mud, you need lugs. If you’re on the road, you want narrower. If you going to be hitting sharp rocks/thorns you need durability.

If you’re just rolling around on the trails pictured, a Rene Hense 44mm or 48mm knobby tire with the standard casing would probably be best- extra light if you’re willing to risk a flat. You’re going to be under 30kph, it always looks moist for some reason, and there’s little bumps everywhere. If you’re just hitting an odd mud puddle once in a blue moon, you’re got more options (Specialized Pathfinder, Challenge gateway) . If you’re doing a lot of asphalt riding, then hitting those trails, the 38-42c options out there would be best (conti Terra Speed, Panaracer SK).

The offerings in the 40-54mm tire range aren’t as efficient as the offerings in the 38c range (haven’t tried the Rene tires yet though). If the Renes are too expensive, there are a bunch of OK tires here Maxxis Rambles , Michelin, Schwalbe Gone Bite, Conti mud-tier XC 2.0 MTB tires, I’d check around to your local bike shops to see if they have a discontinued Schwalbe g-one Bite or Ultrabite “Onestar” Evo on the shelf - those are really good too (the new ones they made more durable/slow for ebikes)

CX is a dumb /outdated speciality in a gravel bike world.

Hol up. You best be talking about the tire choice and not the discipline itself. Cause if not, I’ve got some hands you can catch.

I foresee the sport going to 35s in the near future, but part of the challenge of cx lies in small tires. It makes you a better curly bar bike handler and presents its own challenge.

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My CX bike is dumb and only beats gravel bikes on gravel :man_shrugging:

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That isn’t correct…while conditions will certainly impact which tire choice is correct, there was a recent study that showed the Specialized pathfinder Pro in 38mm was the fastest gravel tire (and that included testing it against its 42mm sibling).

For the conditions pictured (again, outside of the mud) a 38mm tire would be faster than a wider tire.

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Do you go golfing with just sticks (no club head)?

Yes, CX is stupid. It made sense when you were trying to race off road and all you had were steel road and touring bikes, but the product offerings have moved on. CX needs to move to short-course gravel. As soon as you have CX-specific equipment, the whole point of the 33c tire rule is pointless. It can still take place on a contrived “bar-backyard” / park style course.

I rode some rough TX gravel recently on specialized 38s and couldn’t see how a wider tire would have made me any faster or given a difference in grip.