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Thread: dumb question

  1. #1
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    dumb question

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    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.

  2. #2
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    The bottom bracket is higher to give you better clearance over obstacles, and the tires are wider for better traction. Hope that helps!

  3. #3
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    And the tires will have tread, little knobbies more like a mountain bike tire.
    Frends know gud humors when dey is hear it. ~ Da Crockydiles of ZZE.

  4. #4
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    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.

  5. #5
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    Quote Originally Posted by velogirl View Post
    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.)

  6. #6
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    Quote Originally Posted by velogirl View Post
    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?
    Just keep pedaling.

  7. #7
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    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.

  8. #8
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    Another tire question....

    Thanks for the question, Ruth! And to Velogirl for her answers!

    All of the pros I know LOVE their tubulars, but I was thinking that in cyclocross, it would be a detriment to use tubulars because of the difficulty in fixing the flats (I know racing, you probably have multiple tires already on rims for quick change, but I am talking about just going out and about off road)- And are tubeless becoming popular in the cyclocross arena?

    Now that I have my new baby coming, I started getting more tire and rim geeky....frightening.....
    The best rides are the ones where you bite off much more than you can chew--and live through it.

  9. #9
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    If you don't race, you don't need tubulars. Stick with your clinchers and you'll be fine.

    UST tubeless technology hasn't hit the cross scene yet, although Tufo makes a tubular clincher (basically a tubular with a bead so it fits on a clincher rim). I just got some and it was hecka-hard to mount. I couldn't do it by myself and even me & a big guy had a hard time doing it together. It's so tight because it's designed to seal the rim. In my opinion, this would be super-hard to change a flat.

    Did I mention you should just stick with your clinchers?

  10. #10
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    So

    Hmm, maybe I should stick with clinchers; at least that is what I am reading between the lines there, Velo - I might do some local racing, but just for the fun of it.

    Thanks! About the last thing I would have thought I would be is a tire geek....wow, now I just need a pocket protector for my bike jersey.
    The best rides are the ones where you bite off much more than you can chew--and live through it.

  11. #11
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    Quote Originally Posted by velogirl View Post
    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.
    I ran my clinchers at 37psi this weekend. It worked well with the course. I'm not sure how I would feel dropping it below 35, but I'll have to experiment. I really wanted to run them lower than 37psi, but I was too chicken. One of my teammates sometimes drops her tire pressure to 28-30psi and doesn't have problems with flats. I really like the feel of riding on a lower tire pressure, but I fear the DNF too much.
    Just keep pedaling.

  12. #12
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    rocks, and more rocks

    Some of our courses in Flagstaff are way to rocky for running really low pressure - they are not typical smoother cyclocross courses so typically I can't run real low pressures -
    but since it looks like the only cyclocross this year will be down south in Tucson and Phoenix (whoever heard of cyclocross without snow??? ); I'll probably be able to run higher air pressures

 

 

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