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.

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

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

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