tubeless pinch flat protection on CX tires

chas wrote:
But the real solution is, unfortunately, to get a bike that takes bigger tires.  If you are bottoming out, you need more volume or pressure.  Sooner or later its gonna cost ya.

mack_turtle wrote:To clarify my question: do people on CX bikes with tubeless tires suffer pinch/ slice flats like this? If so, how do they get away with super low pressure?

• run the biggest tires that fit.
• run a  narrower rim(in the rear). Pinch flat protection comes from tire height, not width, so a  big tire on a narrow rim will do better than a smaller tire on wider rim when they measure out to the same actual width.
• run more pressure, especially in the rear. You say you don’t want to run 60psi, but there is still a big gap between 35-40 psi and 60. Are you sure you were at 40 when this happened? Maybe you started at 35, and lost some air, and you were actual at 30psi when you hit the rock. How about trying 42, then 45? Keep going up in small increments until you don't bottom out anymore 
• Use a tire with a stiffer sidewall. This will help quite a bit, both to prevent bottoming out at low pressure, but mostly to protect the casing from cutting when the rim does hit.

Well, the CX events I’ve competed in have the course swept and cleaned the day before.  Much of the course is on grass (or mud).  People pre-ride the course.  And yes, stuff still happens – so the more serious people bring a spare set of wheels so they can do a hot swap during the race.

What I have done in your shoes:

- Stick a wider tire on the front.  If you don’t care about mud clearance, you can go pretty big up front on a CX bike. 

- Run 60+psi in the back and use a thudbuster

As GHC mentioned – volume does not go up linearly with width.  There is a bigger volume difference between 32 and 35 than you might imagine.  Yeah, you want more, but at this point, it sounds like you could use all you can get.

Are you bottoming out front or rear?

Your rear tire probably takes 50% more weight than your front tire (with a 40/60 weight distribution).  Consider bumping up the rear if that is where you are bottoming out.

I don't like going too tight on the rear.  I find I torque the tire into the frame and it wears down the frame.  Obviously if you break a spoke or warp a wheel you'll be walking with tight clearance. 

bnystrom wrote:I see what you're saying and while it seems to make sense, I'm not convinced that it's actually true.

When you look at mounted tires and rims, they combine to create a specific circumference. Most of that is the tire, but part of it is the rim, at the point where the tire beads meet it. If your two rim/tire combos have the same width, they'll also have the same circumference. If the circumference is the same, the height is the same, since the tire casing is always going to assume a round shape (width=height).

bnystrom wrote:As for the casing, it will assume a round shape,