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#21
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Replace Mavic MA40 Rim with... ?
On Sun, 29 Sep 2019 21:19:59 -0700 (PDT), Sir Ridesalot
wrote: On Sunday, 29 September 2019 23:06:52 UTC-4, Frank Krygowski wrote: On Sunday, September 29, 2019 at 2:37:44 PM UTC-4, Ned Mantei wrote: Some (many? most?) rims have wear indicators. At least for Mavic XC717 and X719 there are/were tiny holes going partway into the rim. The idea is that the rim should be replaced when the holes are no longer visible. None of my rims have those. If I had one around, I'd mike the thickness from the bottom of the wear indicator to the inside edge of the rim. That should be the assumed minimum safe thickness. - Frank Krygowski Then again, that wear indicator, or at least the ones I've seen, are akin to a deep gouge and I wonder if they in themselves don't become a stress riser as the rim wears down towards the bottom of the groove. What's your guess on that? Cheers Depending on the direction that the force is applied any thinner section is stressed to a greater extent than an adjacent thicker section. But whether the thinner section is subject to breaking is dependent on the force applied and the strength of the thinner section. -- cheers, John B. |
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#22
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Replace Mavic MA40 Rim with... ?
On 9/29/2019 10:06 PM, Frank Krygowski wrote:
On Sunday, September 29, 2019 at 2:37:44 PM UTC-4, Ned Mantei wrote: Some (many? most?) rims have wear indicators. At least for Mavic XC717 and X719 there are/were tiny holes going partway into the rim. The idea is that the rim should be replaced when the holes are no longer visible. None of my rims have those. If I had one around, I'd mike the thickness from the bottom of the wear indicator to the inside edge of the rim. That should be the assumed minimum safe thickness. - Frank Krygowski In theory yes. Trouble is that with modern cut-side rims the resulting thickness is not uniform all around the perimeter -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 |
#23
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Replace Mavic MA40 Rim with... ?
On Monday, September 30, 2019 at 12:20:02 AM UTC-4, Sir Ridesalot wrote:
On Sunday, 29 September 2019 23:06:52 UTC-4, Frank Krygowski wrote: On Sunday, September 29, 2019 at 2:37:44 PM UTC-4, Ned Mantei wrote: Some (many? most?) rims have wear indicators. At least for Mavic XC717 and X719 there are/were tiny holes going partway into the rim. The idea is that the rim should be replaced when the holes are no longer visible. None of my rims have those. If I had one around, I'd mike the thickness from the bottom of the wear indicator to the inside edge of the rim. That should be the assumed minimum safe thickness. - Frank Krygowski Then again, that wear indicator, or at least the ones I've seen, are akin to a deep gouge and I wonder if they in themselves don't become a stress riser as the rim wears down towards the bottom of the groove. What's your guess on that? I doubt they'd cause a problem, because I think the manufacturers would be conservative with the depth. That is, they would take that into consideration when they designed the groove. By the way, stress risers make a difference only with either brittle materials, or with materials subject to fatigue (i.e. varying) loading. I suspect the main varying load on the rim wall would be a slight fluctuation in outward spreading force as the tire contact patch was loaded and unloaded. I'm not sure the magnitude of variation would cause significant fatigue. I guess one way to find out would be to examine a bunch of worn and failed rims. See if any still had the indicator groove visible at the failure. If not, all is good. - Frank Krygowski |
#24
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Replace Mavic MA40 Rim with... ?
On Monday, September 30, 2019 at 9:15:55 AM UTC-4, AMuzi wrote:
On 9/29/2019 10:06 PM, Frank Krygowski wrote: On Sunday, September 29, 2019 at 2:37:44 PM UTC-4, Ned Mantei wrote: Some (many? most?) rims have wear indicators. At least for Mavic XC717 and X719 there are/were tiny holes going partway into the rim. The idea is that the rim should be replaced when the holes are no longer visible. None of my rims have those. If I had one around, I'd mike the thickness from the bottom of the wear indicator to the inside edge of the rim. That should be the assumed minimum safe thickness. - Frank Krygowski In theory yes. Trouble is that with modern cut-side rims the resulting thickness is not uniform all around the perimeter I wonder what the minimum dimension is, at the thinnest point. - Frank Krygowski |
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