Grinding sound when standing and sprinting?
02-08-15, 08:25 PM
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Grinding sound when standing and sprinting?
I have a cross bike that I just built a wheelset for. I got on the trainer earlier and noticed it did it on the factory wheelset too (that I'm now using with slick tires for road biking).
In my 3-4 smallest cogs if I stand and sprint, I get a grinding/crunching sound. What could this be?
Shifting is flawless, hangar is straight, and it does it on two different wheelsets/cassettes. The bike has maybe 400 miles on it and I maintain/clean it to an almost OCD level.
In my 3-4 smallest cogs if I stand and sprint, I get a grinding/crunching sound. What could this be?
Shifting is flawless, hangar is straight, and it does it on two different wheelsets/cassettes. The bike has maybe 400 miles on it and I maintain/clean it to an almost OCD level.
02-08-15, 09:00 PM
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First things first. Take a look at the crowns and sides of your tires, and check for any signs of rubbing. Sometimes sprinting deflect the bike enough for the tire to rub on the yoke of the trainer. If that's the issue, there should be visible marks or dust.
If what you're hearing is more by way of a whirring or buzz, it might be chordal action. We think of chains and sprockets as if they were ropes on pulleys, but that's not the reality. The chain runs on sprockets more like a rope running on a pulley that's a multi-sided figure having as many sides as the sprocket has teeth. That means the radius changes as the chain is pulling on a flat vs. a corner. So the chain is moving up and down X times per sprocket revolution, plus the sprocket speed (or chain speed) changes that many times also.
That produces vertical vibration, plus tension vibration and a noticeable grinding. This becomes more pronounced as the number of teeth are reduced, and would be very obvious if you imaging a sprocket having only 3 or 4 sides.
By analogy, imagine riding on wheels that have 32 sides, or 16 sides, or 8, 6, 4 or even 3.
If what you're hearing is more by way of a whirring or buzz, it might be chordal action. We think of chains and sprockets as if they were ropes on pulleys, but that's not the reality. The chain runs on sprockets more like a rope running on a pulley that's a multi-sided figure having as many sides as the sprocket has teeth. That means the radius changes as the chain is pulling on a flat vs. a corner. So the chain is moving up and down X times per sprocket revolution, plus the sprocket speed (or chain speed) changes that many times also.
That produces vertical vibration, plus tension vibration and a noticeable grinding. This becomes more pronounced as the number of teeth are reduced, and would be very obvious if you imaging a sprocket having only 3 or 4 sides.
By analogy, imagine riding on wheels that have 32 sides, or 16 sides, or 8, 6, 4 or even 3.
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02-08-15, 09:04 PM
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First things first. Take a look at the crowns and sides of your tires, and check for any signs of rubbing. Sometimes sprinting deflect the bike enough for the tire to rub on the yoke of the trainer. If that's the issue, there should be visible marks or dust.
if what you're hearing is more by way of a whirring or buzz, it might be chordal action. We think of chains and sprockets as if they were ropes on pulleys, but that's not the reality. The chain runs on sprockets more like a rope running on a pulley that's a multi-sided figure having as many sides as the sprocket has teeth. That means the radius changes as the chain is pulling on a flat vs. a corner. So the chain is moving up and down X times per sprocket revolution, plus the sprocket speed (or chain speed) changes that many times also.
That produces vertical vibration, plus tension vibration
if what you're hearing is more by way of a whirring or buzz, it might be chordal action. We think of chains and sprockets as if they were ropes on pulleys, but that's not the reality. The chain runs on sprockets more like a rope running on a pulley that's a multi-sided figure having as many sides as the sprocket has teeth. That means the radius changes as the chain is pulling on a flat vs. a corner. So the chain is moving up and down X times per sprocket revolution, plus the sprocket speed (or chain speed) changes that many times also.
That produces vertical vibration, plus tension vibration
sounds like its metal crunching/grinding
there's some rubbing from those rubber spike things on new tires on the inside of the front fork
02-08-15, 10:16 PM
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I wasn't thinking of rubbing within the bike, but against the yoke that supports the trainer's roller. The axle supports aren't super rigid, so when working hard the bike can rock, moving the tire along the roller. Flex hard enough and the tire moves beyond the end of the roller and rubs the supporting yoke.
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02-08-15, 10:43 PM
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I wasn't thinking of rubbing within the bike, but against the yoke that supports the trainer's roller. The axle supports aren't super rigid, so when working hard the bike can rock, moving the tire along the roller. Flex hard enough and the tire moves beyond the end of the roller and rubs the supporting yoke.
02-08-15, 10:50 PM
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Does it make this noise riding on the road, or only on the trainer?
02-08-15, 11:17 PM
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I never know how much the OP knows or has done prior to posting, so forgive the following question.
You describe "metal crunching/grinding" when using the outer 1/3rd of the cassette. Any chance we're talking about simple chain/front derailleur cage rub?
Otherwise, consider chain plate rub on the chain ring teeth, with lack of lube, or maybe a bit of grit. Simple test here, add some oil to your chain and see if the nature of the sound changes.
You describe "metal crunching/grinding" when using the outer 1/3rd of the cassette. Any chance we're talking about simple chain/front derailleur cage rub?
Otherwise, consider chain plate rub on the chain ring teeth, with lack of lube, or maybe a bit of grit. Simple test here, add some oil to your chain and see if the nature of the sound changes.
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An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
02-09-15, 08:04 AM
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02-09-15, 08:05 AM
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I never know how much the OP knows or has done prior to posting, so forgive the following question.
You describe "metal crunching/grinding" when using the outer 1/3rd of the cassette. Any chance we're talking about simple chain/front derailleur cage rub?
Otherwise, consider chain plate rub on the chain ring teeth, with lack of lube, or maybe a bit of grit. Simple test here, add some oil to your chain and see if the nature of the sound changes.
You describe "metal crunching/grinding" when using the outer 1/3rd of the cassette. Any chance we're talking about simple chain/front derailleur cage rub?
Otherwise, consider chain plate rub on the chain ring teeth, with lack of lube, or maybe a bit of grit. Simple test here, add some oil to your chain and see if the nature of the sound changes.
is it nothing to worry about it that's the case?
02-09-15, 09:03 AM
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Put your bike in the biggest gear combo you have, big up front small in back, then take a flashlight and hold it under the chain at the front derailleur and backpedal the bike. The light will help you see if it is rubbing at all. Video shouldn’t be necessary.
Skip to 1:20
Last edited by EnsitMike; 02-09-15 at 09:11 AM.
02-09-15, 10:16 PM
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I was wondering if this was it as well. It is just a matter of adjusting your limit screws.
Put your bike in the biggest gear combo you have, big up front small in back, then take a flashlight and hold it under the chain at the front derailleur and backpedal the bike. The light will help you see if it is rubbing at all. Video shouldn’t be necessary.
Skip to 1:20
Put your bike in the biggest gear combo you have, big up front small in back, then take a flashlight and hold it under the chain at the front derailleur and backpedal the bike. The light will help you see if it is rubbing at all. Video shouldn’t be necessary.
Skip to 1:20
02-09-15, 10:55 PM
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Read this thread. Sounds like you have the same problem, and the diagnosis and possible resolution would be the same.
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“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
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An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
02-10-15, 07:51 PM
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Sound like a problem I experienced recently. Turns out when I was installing my BB (octalink) the splines were not completely engaged so when I would put a large amount of pressure on the crank I would hear and feel a click/crunch. Check your BB.
