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New Tires

  1. Mar 28, 2005 #1
    I just put slick tires on My Bicycle, my beloved Fuji. It used to have nubby tires. Now the ride is so smooth...

    They say that there is not a significant decrease in traction on smooth tires, because the rubber-coated nylon tires actually take on the shape of the pavement pebbles as they roll.

    Recommended pressure 90 pounds per square inch!! :smile: Though they're probably at 70 or so right now.

    I want it to stop raining
  2. jcsd
  3. Mar 28, 2005 #2


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    Take it from an old street racer (and Hypatia can back me on this because she was there)... knobby tires are for traction on rough terrain. (My current vehicle is a 4-wheel drive El Camino with 33 inch Trailblazers, and I can go places that a bulldozer can't.) Slicks, particularly very soft, no-discernable-sidewall slicks, are for maximum traction on dry pavement. For wet, but warm, areas you need something with water-displacement tread design (it essentially squishes the water out the sides so you don't hydroplane). Winter is tougher, between snow or ice traction, but you need a softer compound. Regardless of the tread design, you get more traction with less inflation; but also more torture and shorter life for the tire.
  4. Mar 28, 2005 #3
    So where were you and Hypatia?

    Bicycles can't hydroplane because the tires are too skinny and round and the pressure is too high. That's cool about slicks actually having more traction on dry pavement--I didn't know that. They have less rolling resistance.

    So "no sidewall" means better traction for cars? I've wondered why some cars have tires like that.
  5. Mar 28, 2005 #4


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    Detroit, late '60s-early '70s. She's still there. I was on our side of the border, and left in '78. (If I'd known about her, I wouldn't have left.)
    Wrong... they have more. But what they suffer in rolling resistance, they way more than make up for in traction.
    You're mistaking low-profile tires, like the ones that come stock on a rice-rocket, for racing slicks. A short sidewall like you're thinking of gives better rigidity on curves, and hence less sway, and look a lot better on a car that's the size of model kits that I bought as a kid. Racing slicks are specifically designed to act as not only the car/pavement interface, but also a transmission. They're very soft and very wide (generally 15-20 inches across). The compound is gummier than standard to start with, but they also do a 'burn-out' on a section of track with bleach poured on it. That's when they just smoke the **** out of the tires a couple of times before staging. The reason for doing that is to heat, and therefore soften, the rubber. Soft rubber grabs the pavement better. The special feature of the tires is in the sidewall/tread integration. They start out very short and fat for maximum surface contact (traction) and gearing (small diameter). As the car accelerates, centrifugal force narrows the tire and expands its diameter. Hence less surface contact (rolling resistance) and gearing (large diameter). It's all far more technical than that, and beyond my knowledge, but I'm sure that someone else around here can give you better information. :smile:
  6. Mar 28, 2005 #5
    I love new tires! I even love the smell of them..I know that can sound kind of sick..but I was raised in the Motor city And still sneak in with the street racers at times.
    I ride a cannondale bike. Its kind of hybrid/crossover. Ihave road tires on it now{ribbed for my pleasure}, and keep the knobies for ruff land. I don't think I'd ride with pure slicks here..too much road oils and in the summer with our 90% humidity..its like riding on ice.
  7. Mar 28, 2005 #6


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    Hi gorgeous; I figured you wouldn't mind me dragging you into this. Kind of sick...? Are you daft, woman? Burning rubber and nitro fumes should be made into an air freshener (or at least an after-shave). And anybody who's ever felt a blown/injected nitro-burning 484 cube elephant rattle their ribcage at 50 feet will buy it by the truckload.
    So you've got the humidity down to 90% now, huh? That's 9% better than when I left.
    Hey, just out of curiosity... who's on top now? When I left, Steve Lisk's 430 cube hemi T/A Challenger with the Lenco had just displaced Joe Ruggarilo's 505" Mustang II. But Joe had a 600" aluminum Can Am to put into the 'Stang. Is either one of them still in the scene, or has something ever wilder turned up? (Jeez, it's pitiful how much I miss that crap.)
  8. Mar 28, 2005 #7
    Theirs a whole crop of new young racers, with there souped up hot wheels.{Fast and Furrious} I like cars with some meat on them still. My son and I have a 69 Chevelle with a 350, Its been a joint project for 3 yrs now. Last summer we were pulling high 6's in the 1/4.
  9. Mar 28, 2005 #8
    Well, on cars. On bikes, slicks aren't sticky, they are made to be inflated to very high pressure, and heat energy isn't wasted compressing and pushing around any tread nubs. As a result they have a big advantage in rolling resistance (you think they'd use slicks in the Tour de France if they were inefficient?). If you feel them when inflated, they feel like solid rubber. The reduced resistance is noticeable.

  10. Mar 28, 2005 #9


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    Holy sheep ****! I used to just love you for your body! We might have to finish this on PM; my keyboard's getting wet. :tongue2:
  11. Mar 28, 2005 #10
    Hypatia, if you like your bike you should get a regular street bike.

    Truth be told, only the front wheel on my bike is a slick right now. The back one doesn't have nubs but it does have a pattern--it has a raised longitudinal ridge for a centerline. They're both smooth though and that's what counts in terms of feel, and mostly for resistance. (They're 27 x 1 1/4 inches, not real ultra-skinny racing tires; roads around here aren't good enough for those anyways)
  12. Mar 28, 2005 #11


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    Oooppps! My mistake. I thought that you were referring to a real bike, not one that you have to pedal. I haven't a clue about those things. :redface:
  13. Mar 28, 2005 #12
    Well, I did say bicycle in the original post. Besides, bicycles _are_ the real bikes (grandfathered in). Motorcycles are... good god... they suck. Dangerous, loud, SLOW in the city! No exercise, expensive... they sound like flatulence going down the street on two wheels.
  14. Mar 28, 2005 #13


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    Yeah... I saw that when I checked back. By the time we got through the first round of tire talk, I'd forgotten.
    And to you this is a bad thing...? 'No exercise'... Cripes, man! The only excercise that I burden myself with is breathing, and if I could hire somebody to do that for me without dropping dead I would. I live by the principle of 'what's a gallon of gas to save a few steps?' And as for the flatulence on wheels, just ask Hypatia about the afterburners on my car... :biggrin:
  15. Mar 28, 2005 #14
    You're probably right about that for rolling straight ahead, but I've seen enough guys (including myself) riding slick 110psi 700x20's go down in turns on wet pavement to suspect that they can hydroplane sideways. :surprised

    Maybe not so much of a problem with your "fat" 1¼ inchers, but I'd still be careful when it rains.
  16. Mar 28, 2005 #15
    Hmm, I'd have thought it would have been more of a problem with wider tires (more room to trap water). Maybe the book I read it from was misinformed.

    The really skinny tires would have longer contact patches even though they have higher pressure, so that might contribute.
  17. Mar 28, 2005 #16


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    How do you get that? For any given pressure, the wider the tire, the more surface area in contact with the road.
  18. Mar 28, 2005 #17
    You're right (about the wider tires; not about the "longer contact patches"), as long as the tire is moving forwards. But on a fast turn, as soon as it starts slipping sideways ...

    Well, just look at it from the side. If it starts moving that way, it makes no difference how fat or skinny the tire is -- they're all pretty much the same in that direction, except for differences due to tire pressure.
    Last edited: Mar 28, 2005
  19. Mar 28, 2005 #18
    Well, what I was thinking about the contact patch is that my tire is about 50% wider than yours and your tire is at about 50% more pressure, and the width counts more than the pressure. Say that the contact patch width is the width of the tire (which it isn't, but say it is), and the contact patch is a rectangle (which it isn't, but say it is). For a 100 lb load, your contact patch is .91 square inches, and since your tire is 4/5 in. wide (assuming the 20 means 20 mm... does it?), 4/5 x = .91 and x (the length) = 1.14 (inches). For mine (at 70 PSI), the contact patch is 1.43 square inches, and the width is 1.25 in., so the length is... um... 1.14 inches.

    So it seems there is not much of a difference. But that's the way I was thinking.

    Maybe it's not hydroplaning at all. Hydroplaning has to trap water under the tire. I just can't imagine that happening on a 110 PSI tire. It may be just ordinary loss of traction on slippery roads. I don't think that's always due to hydroplaning.
  20. Mar 28, 2005 #19
    Well I don't know if its technically hydroplaning or not.

    The way I understand it, hydroplaning happens when you get a sort of "wedge" of water trapped in front of the tire, and then the tire rides up on top of the water. It's not likely to happen to a skinny tire moving straight ahead, but if starts to slip sideways at all, it can "squeegee" the water in that direction & then slip up onto that water. In that direction the width of the tire makes no difference because the length of the contact patches are roughly the same.

    Hydroplaning or not, it doesn't feel nice.
  21. Mar 28, 2005 #20


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    :uhh: I'm thinking it might be more effective as a woman's perfume. A little dab on the neck and watch the guys line up! :biggrin: I don't think it'll work as well as an aftershave, unless of course you're trying to get rid of a few women. :tongue2:
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