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#11
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Replace Mavic MA40 Rim with... ?
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#12
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Replace Mavic MA40 Rim with... ?
On Saturday, September 28, 2019 at 8:51:31 AM UTC-4, wrote:
Thank you for the further input, jbeattie, John, David, AMuzi and Tosspot. I squeezed the sides of the braking surface, and the rim seems solid. Is there a rule of thumb for minimum safe rim thickness at the braking surfaces? - Frank Krygowski |
#13
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Replace Mavic MA40 Rim with... ?
On 9/28/2019 9:06 AM, Frank Krygowski wrote:
On Saturday, September 28, 2019 at 8:51:31 AM UTC-4, wrote: Thank you for the further input, jbeattie, John, David, AMuzi and Tosspot. I squeezed the sides of the braking surface, and the rim seems solid. Is there a rule of thumb for minimum safe rim thickness at the braking surfaces? - Frank Krygowski Yes. Go this far: http://www.yellowjersey.org/photosfr...st/wornrim.jpg and then reverse the wear a little. -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 |
#14
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Replace Mavic MA40 Rim with... ?
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#15
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Replace Mavic MA40 Rim with... ?
On Saturday, September 28, 2019 at 9:06:57 AM UTC-5, Frank Krygowski wrote:
Is there a rule of thumb for minimum safe rim thickness at the braking surfaces? I've worn a couple rims to the point where they have begun to show cracks along the braking surfaces. The brake on the affected wheel would "pulse" slightly because of the wide spot. The brake surface was between 0.5 and 1.0mm thick. Most of the new rims I've measured have 1.4 to 1.6mm of brake surface thickness. So I'd say when the thickness reaches around 1.0mm it would be time to start looking for a brake pulsation and planning a rim replacement at a convenient future time. |
#16
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Replace Mavic MA40 Rim with... ?
On Saturday, September 28, 2019 at 9:43:30 PM UTC-4, Steve Weeks wrote:
On Saturday, September 28, 2019 at 9:06:57 AM UTC-5, Frank Krygowski wrote: Is there a rule of thumb for minimum safe rim thickness at the braking surfaces? I've worn a couple rims to the point where they have begun to show cracks along the braking surfaces. The brake on the affected wheel would "pulse" slightly because of the wide spot. The brake surface was between 0.5 and 1.0mm thick. Most of the new rims I've measured have 1.4 to 1.6mm of brake surface thickness. So I'd say when the thickness reaches around 1.0mm it would be time to start looking for a brake pulsation and planning a rim replacement at a convenient future time. 1 mm sounds pretty practical to me. I've never ground a rim down to failure, but I think I'm pretty easy on brakes. Unlike Jay, I only rarely rode to or from work in the rain. I was comfortable coasting at 30 mph on the way to work, since my routes were mostly low traffic roads. And when biking (as when driving) I tend to watch far ahead for potential conflicts or events. - Frank Krygowski |
#17
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Replace Mavic MA40 Rim with... ?
On 28-09-19 16:06, Frank Krygowski wrote:
On Saturday, September 28, 2019 at 8:51:31 AM UTC-4, wrote: Thank you for the further input, jbeattie, John, David, AMuzi and Tosspot. I squeezed the sides of the braking surface, and the rim seems solid. Is there a rule of thumb for minimum safe rim thickness at the braking surfaces? - Frank Krygowski 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. However, more often I have replaced the rim because the brake is grabbing at one spot, which could be because the rim is getting wider there and might fail. After once replacing a rim for this reason I took the old rim to my LBS to ask whether they would have done something similar. They broke the rim into pieces by putting it between the jaws of a vise and pushing back. One part of the rim wall at a break was only about 0.7 or 0.8 mm thick, dangerously thin. However, just now it occurred to me that this could have been because the rim wall "stretched" as it was being broken apart, so I'm not sure that this was a proper measurement. Clearly I should break a brand new rim as a control, but I'll pass on this. My older bikes have 26" wheels, and it's becoming difficult to impossible to find rims with the effective rim diameter that will fit the old hubs and spokes. For two bikes, 13 and 16 years old, it would have been time for rim #5 on the back wheel. Replacing both the spokes and rims was more than I wanted to deal with, and the hubs were anyhow old, so I gave up and bought complete new wheels. Ned |
#18
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Replace Mavic MA40 Rim with... ?
On Saturday, 28 September 2019 12:00:41 UTC-4, AMuzi wrote:
On 9/28/2019 9:06 AM, Frank Krygowski wrote: On Saturday, September 28, 2019 at 8:51:31 AM UTC-4, wrote: Thank you for the further input, jbeattie, John, David, AMuzi and Tosspot. I squeezed the sides of the braking surface, and the rim seems solid. Is there a rule of thumb for minimum safe rim thickness at the braking surfaces? - Frank Krygowski Yes. Go this far: http://www.yellowjersey.org/photosfr...st/wornrim.jpg and then reverse the wear a little. -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 That looks like the used Matrix rim I had that recently failed! Cheers |
#19
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Replace Mavic MA40 Rim with... ?
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 |
#20
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Replace Mavic MA40 Rim with... ?
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 |
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