dumb question

I was just looking at the pictures from the race report...Congrats byt he way...Anyway...hmm, how do I put this, Are the tires/wheels on a cross bike bigger that on a "regular" bike?

Pardon my ignorance.....

Ruth

Oh and by the way, it looks awesome and I want to do it.

The bottom bracket is higher to give you better clearance over obstacles, and the tires are wider for better traction. Hope that helps!

And the tires will have tread, little knobbies more like a mountain bike tire.

We run different tires based on different course conditions. You want a different width and tread pattern for mud than you do for sand or for a course with lots of pavement. We also vary tire pressure based on the course.

For example, on mud, you want as few knobs as you can ride because that will help shed the mud. On sand, you want something a little wider.

I always make these decisions based on the worst terrain element of a course. For example, if a course is primarily fast and hard-packed, but has one section that's really loose, I'll plan for the loose section. If there's one really bad curb that might cause a flat, I'll run a little more psi even though the rest of the course might dictate less psi.

Most racers run a width between 30 & 34. You could run wider (assuming clearance on your bike), but there are very few times you'd want narrower.

Most racers also have a bunch of different tires (or even different wheelsets) for different course conditions. I think cyclocross racers are even bigger geeks than mtn bikers when it comes to tires and tire pressure.

I've been racing on tubulars for the past three years. This allows me to run a very low psi without pinch flatting (something you'd do with a clincher). I also have regular clinchers and tubular clinchers. By running a super-low psi, you have a larger contact patch on the tire. The biggest mistake most new racers is running to high a psi.

Quote:

Originally Posted by velogirl

The biggest mistake most new racers is running to high a psi.

Here's a question that's been lurking in my mind for a long time . . . among (non-racing) roadies, there is a school of thought that says you should keep your tires inflated to no more than 95-100 psi, regardless of what's printed on the sidewall. (Many roadie tires can accept up to 125 psi, some even higher.) These less-than-max pressures make for a smoother, more comfortable, more controllable ride, but aren't soft enough to make pinch flats more likely.

So, is there an equivalent rule for my size 32, 75-max-psi tires? Is there any benefit (or detriment) to inflating them to only, say, 60 or something?

(I don't race, BTW, but I often use my 'cross bike for long rides on packed gravel/dirt trails.)

Quote:

Originally Posted by velogirl

I've been racing on tubulars for the past three years. This allows me to run a very low psi without pinch flatting (something you'd do with a clincher). I also have regular clinchers and tubular clinchers. By running a super-low psi, you have a larger contact patch on the tire. The biggest mistake most new racers is running to high a psi.

Velogirl,

This is my first season of CX, so I've got many things to figure out...including tire pressure. What is the lowest psi that you would personally use without getting pinch flats?

I've run in the low 30s on my clinchers (rated to 40psi min, I think) and into the 20s on my tubulars. And I'm a big girl.

And I won't say it, but I've never (you know what) -- knock on wood!

One way I learned what pressure to run was start high. I used to always start aroudn 45psi for my pre-rides. As I would ride the course, I'd see if I was bouncing around (too high). If so, I'd let some air out until I liked the feel. Then I'd check the pressure with a guage (I've got a digital one). After doing that for a while, I've learned what I like.

Although, I still raced with too much air my first race this season. I put the wrong type of valve stem extenders on my new tubulars and I couldn't check the pressure. It's was the first race with lots of distractions and I didn't take enough air out. Was sliding around all over the place.