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Old 04-30-10, 07:38 PM   #1
gldrgidr
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Need info on chainrings

Hi. I just pulled a Roadmaster Mt Climber Sport from a dumster at my apartment complex.
I know. You get what you pay for. I'm sure most will tell me to throw it back.
The smaller chainring has 6 teeth worn down. I can remove the chainrings but where do I get replacements?
Are these chainrings a standard item or are they specific to Roadmasters?
The smaller one has 38 teeth and the larger one has 48 teeth.
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Old 04-30-10, 09:35 PM   #2
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That 38T ring might have the teeth ground down on purpose. The shorter teeth help the chain ride up when making an upshift. Even though this is now the small ring, it may have once been the middle ring in a triple.

:)ensen.
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Old 04-30-10, 09:50 PM   #3
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If you're set on replacing the rings, just go ahead and do the whole crank, it's just as easy, if not easier. It's a one-piece crank, I'm betting.

If I was a little bit shady, I might suggest something like going into a Wally World, getting the 800 number off a Roadmaster, and calling them for a replacement crank. Likely get one for peanuts. But I'm not shady, so, I don't know what to tell you.....
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Old 04-30-10, 09:53 PM   #4
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Originally Posted by purplepeople View Post
That 38T ring might have the teeth ground down on purpose. The shorter teeth help the chain ride up when making an upshift. Even though this is now the small ring, it may have once been the middle ring in a triple.

ensen.
I've never heard of this, but I suppose it could be true. If that's the reason, then the bike should still shift OK and peal smoothly, and I wouldn't change it. If it won't shift or the chain doesn't hook up to the ring when you pedal hard (try it sitting down before you try it standing up...), and assuming it uses a standard bolt circle diameter, any bike shop should be able to sell you a replacement. Most bikes these days use one or the other of a couple of circle sizes. If not, check thrift stores like the Salvation army for a bike you can cannibalize. Around here, at least, they're full of old, cheap bikes for $10 or so.
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Old 05-02-10, 09:13 AM   #5
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If you're set on replacing the rings, just go ahead and do the whole crank, it's just as easy, if not easier. It's a one-piece crank, I'm betting.

If I was a little bit shady, I might suggest something like going into a Wally World, getting the 800 number off a Roadmaster, and calling them for a replacement crank. Likely get one for peanuts. But I'm not shady, so, I don't know what to tell you.....
You're assuming the components are original. My (stolen) Bridgestone had a triple with 28/38/48 on it and the two larger rings had some short teeth on it for smoother upshifts. These shorter teeth were just before the intro of pins which do the same thing even better and don't appear defective on first glance.

:)ensen.
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Old 05-02-10, 07:40 PM   #6
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Quote:
Originally Posted by DX-MAN View Post
If you're set on replacing the rings, just go ahead and do the whole crank, it's just as easy, if not easier. It's a one-piece crank, I'm betting.

If I was a little bit shady, I might suggest something like going into a Wally World, getting the 800 number off a Roadmaster, and calling them for a replacement crank. Likely get one for peanuts. But I'm not shady, so, I don't know what to tell you.....
Thanks to all who replied.

I don't see how this would be shady if I'm paying for the part. The trouble is that this is an older Roadmaster. It is a 12 speed.

If I went to a bike shop, it would probably cost more for the chainrings than the $74 price for an entire new bike from Walmart.

I think this is not a case of someone grinding the teeth to improve the shifting.

Here's some photos.

The chainrings are either spot-welded or rivited together.
I was hoping that it would be possible for me to just order the chainrings online so that it would be economical enough to fix the bike rather than just buy a new bike.
Attached Images
File Type: jpg Crank13x2..jpg (73.1 KB, 9 views)
File Type: jpg crank11x..JPG (48.0 KB, 6 views)
File Type: jpg crank10x..JPG (36.9 KB, 5 views)

Last edited by gldrgidr; 05-02-10 at 07:44 PM.
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Old 05-02-10, 08:01 PM   #7
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Okay, those photos tell a lot. Mostly that the bike is probably not worth fixing. If you're on a budget, don't buy new as you will just get a poor bike. Better to find a good used bike. Start by getting a bike that does not have a one-piece crank, like the one in the photo. Look for a bike with bolts that hold the chain rings and V-type brakes. After that, it likely starts to get expensive.

:)ensen.
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Old 05-02-10, 08:14 PM   #8
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It's hard to see in your pics, ---- but if the profile of the tooth, is the same on both sides, it's fine.
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Old 05-07-10, 05:15 PM   #9
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It's hard to see in your pics, ---- but if the profile of the tooth, is the same on both sides, it's fine.
I can't believe it. But you are right! I put the bike together and it works fine. You would never know there is a problem with the chainring. No noises, no skipping, nothing wrong.

Here's a photo.
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File Type: jpg RoadM2b..jpg (103.1 KB, 12 views)
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