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Old 05-02-07, 04:07 PM   #1
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Are mountain bike teeth different from road bikes?

I bought a used mountain bike and I was looking at the chainring teeth and there is no uniformity. Some are shorter than the others and this is the case all around. There's no uniformity. I'm wondering....is this a design feature? Maybe since mountain bikes are ridden in the mud this may help them shift better when dirty? Or are all teeth supposed to be equally alike. Kinda weird to see the chain teeth sized differently all around.
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Old 05-02-07, 04:15 PM   #2
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Unless it's some kind of special design I've never seen, it's just uneven wear/damage. I've shaved teeth off on logs, rocks, etc. I didn't quite clear. Even on the inner rings, though, I usually have uneven wear on two sides. My theory is that it corresponds to the downward stroke--gritty mountain bike chain + extra stress from pumping hard on the downstroke = faster wear on that part of the ring. If your chain skips, you'll need to replace the chainrings.
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Old 05-02-07, 04:20 PM   #3
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chainring looks like this




see how there are some teeth that are a lot shorter than others?
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Old 05-02-07, 04:46 PM   #4
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thats a worn out chainring
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Old 05-02-07, 04:53 PM   #5
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Find the shortest tooth. Now look exactly opposite the short tooth on the chainring. Do you see another tooth that looks the same? If so, what you are looking at is teeth that have been designed to make shifting easier.

As a general rule, when chainrings wear they get real pointy looking and I'm not seeing that in your photos.
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Old 05-02-07, 05:51 PM   #6
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+1 with the grouch. FSA and some other chainring designers use different tooth profiles and even the angles machined onto the faces of the teeth to ease the chain onto and off of the rings. You will not find these features on the inner ring but you may on the middle and outer. You can also look at the inner surface of the rings to find the pins that pick up the chain. The arc that the chain will make as it climbs these pins leads right into the short teeth.

These features are not commonly seen on older or less expensive (pre CNC Machine days) chainrings.
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Old 05-02-07, 05:59 PM   #7
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mountain bikes are more like canines, and road bikes are more like herbivores. Except for Lance's bikes, of course.

Honestly, your pictures show typical differentially-shaped teeth, which the last two posts have pointed out is pretty normal in modern bike components (even cheap stuff) on all sorts of bikes, to facilitate front shifting.
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Old 05-02-07, 06:09 PM   #8
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The differences in the shapes of road bike teeth are even more pronounced.

Al
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Old 05-02-07, 06:21 PM   #9
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Quote:
Originally Posted by timcupery
mountain bikes are more like canines, and road bikes are more like herbivores.

That's a good one............and maybe touring bikes are omnivores-
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Old 05-02-07, 06:30 PM   #10
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and don't forget: bikes with lots of unnecessary cosmetic carbon have GRILLZ!

(all God's children got grillz)
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Old 05-02-07, 07:19 PM   #11
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As far as I know the answer to the original question is no.
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