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Home » Q & A » Image Treadmills
Question: What causes the spike-like "growth" on tires and does it affect the tire?
Question Description:
I noticed it first on my bike tires when I increased the air pressure to almost the maximum and used it on my roller (a treadmill-like device that lets you ride your bike indoors --> http://www.bikesomewhere.com/images/big/elite_parabolic.jpg )I also noticed it on my car tires after I increased the tire pressure (recommended in hybrid groups to maximize mpg). But I didn't notice it until I drove the car on the freeway. Most of my daily commute is on surface street.Based on the above, my theory is it happens when the the tire heats up. Does the spike grow until it falls off or does it recede back to the tire? Does it have any effect on the tire?Here's a picture of how it looks like --> http://farm2.static.flickr.com/1169/1107702767_e08404d9c8.jpg?v=0I want to know the science behind it hence the category.Thanks!Although I'm not satisfied with the answers since the car was bought brand new in March and I only noticed the "spikes" this month, I'll give cdf-rom the 10 pts. Also a TU for all the answers. Thanks!
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Answer#1: The people above are MOSTLY right, the "spikes" came with the tires. They are not sprues though, they are vents. Tires are not infection molded. They are build to slightly smaller size (and a bit different in shape). The tires are then put into a press then inflated using a bladder into a mold to cure (essentially harden) the rubber. The vents are overflow of the rubber that is too much for the capacity of the mold.
Answer#2: You, my friend, are a magician's dream!Most "magic" depends almost entirely on sleight og hand and the audience's inattention to detail....The spikes CAME with the tire.Silly goose!
Answer#3: Those are called 'sprues' and the other person was right; those are the points where th eliquid rubber was inected into the tire mold during the manufacturing process. Nothing to worry about. It is just the unavoidable waste material when you are using any kind of molding compound. Ever make a plastic car or ship model? The plastic parts are all injection molded in one piece and there is a framweork around them, you must break each piece apart and there are little bits of waste plastic. A 'sprue' is the plastic in a hole through which it was injected. If the halves of the mold don't fit perfectly together, you get a little oozing out at the edge and it hardens in a bit of a flat sheet, that is called 'flashing'. So it's nothing to worry about. In fact, if a person tries to see you used tires and claims they are new, you can tell if he's lying because now you know new ones must have sprues on them! They will usually wear off (if they contact the road surface) or become brittle from exposure to the sunlight with ultraviolet rays and fall off. The whole tire doesn't become brittle because the UV rays only penetrate a little bit into it. (That's why tires are black; they mix carbon into them to protect them from the UV rays.) But the sprues are thin and the UV penetrates through them eventually. that's probably more than you wanted or needed to know. Sorry. But I hope that answers your question.14 AUG 07, 0131 hrs, GMT.
Answer#4: Those are cast into the tire, and are remnants of the casting process. They were there all along. You just didn't notice them before. Stop by the tire store and look at brand new tires. There they are!
Answer#5: The spikes in your picture are the points where the rubber was injected into the mould during manufacture.
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