Measuring Rim wear

[Chris99]

WARNING This is how my rims behaved, your rims may behave differently.

I had a pile of broken/worn Mavic rims in my garage. Then I was advised an Iwanson gauge can be used to measure the wear.
https://www.ebay.co.uk/i/322893460376?c ... gIemfD_BwE

Using the gauge I measured the rims and found-
Measured using a Iwanson Gauge Spring Measuring Calliper
Rim type (all Mavic) Condition Measurement (mm)
1 XC717........New (unused)................1.6
2 XC719................worn.....................1.3
3 XC719................worn....................1.0 to 1.2
4 XC719................worn.....................1.0 to 1.3
5 Mavic.................worn......................0.8 to 1.0
6 XC719................worn......................1.0
7 XC717................worn......................0.7 to 1.0
8 XC519................worn......................0.6 to 1.0
9 Mavic.................worn......................0.6 to 1.0
10 XC317...............broken...................0.7 to 0.9
11 Mavic................broken...................0.7

All the worn rims had been discarded as they looked past it.

Conclusion
Wear is never even, side to side variation and uneven wear on one side occurs.
Rims break at 0.7mm
Replace rim at 0.9 to 1.0mm
Warning- other manufacturers rims may behave differently!

I would be interested to hear others thoughts on this important matter!

 

[TheAntsPants]

Sidewall failure depends on wall thickness, alloy, tyre pressure, dings in the rim, variations in manufacturing, your star sign etc... Most people don't have the experience or hindsight to learn from past experience and there are just too many variables, so in my experience, measuring sidewall thickness has not been very helpful.

I find a visual inspection of the shape of the sidewalls is the most reliable and practical means of preventing blowout. Rims will tend to bulge out from tyre pressure and then start gradually splitting before exploding. You will feel most such deformation in the brakes too.

If you're still worried, some people advise pumping up your tyres to 150% of your normal tyre pressure, wearing eye protection and taking appropriate precautions. If it does not fail, you're probably pretty safe.

These days many rims have wear indicators that eliminate such issues. But that this topic comes up points to the fact that 26" rims are getting hard to come by :cry:

 

[Chris99]

I agree with everything you say above. But I would add, the two rims I had fail did not look badly worn.

Number 11 was old, I suspect it was the original wheel from 1993. It failed after about 20 years, maybe material aging was a factor.
Number 10 was only 2 years old when it failed, and had not been used a great deal. XC317's use a lower grade material than the XC717 I build wheels with.
I did have another XC717 rim which after about 6 months developed a bulge, so had to be replaced.
Disappointing rims should fail so quickly.

 

[FluffyChicken]

Re:

The 717 should have wear indicators in them, what are they like?

 

[Chris99]

Re:

Unfortunately, there are no wear indicators on the 717 rims.

 

[FluffyChicken]

Re:

A little dip on the inside of the rim, probably near the labels or valve I can't remember. You know they're warn out when they get a hole.

Some mavic also used a milled band all around the rim on the braking surface, I think.

 

[Chris99]

Re:

I did a google search on this. I found numerous references to 'there should be marks on the inside of mavic rims' but nothing definitive, and no pictures.
I went back to my pile of old rims and cannot see any marks at all. And certainly no holes in amy of the rims, even the most badly worn.

 

[FluffyChicken]

Re:

Here are the nicks, one on ech side, they are where the yellow arrows point to.

If they are not there then I think they are pre 2004 (I have a silver one without them and a different label, and two with them. All my black I looked at have them).

It is quite deep, so they don't allow a lot of rim wear by the looks of it, probably 1mm deep
If I ever get them out the loft again, I'll try measure it.

 

[mdvineng]

Mavic quote not more than 0.4mm wear on any one side for rims without built in indicators

 

[Chris99]

Thanks for the pics, they were a great help.

From my 11 Mavic rims just 2 had the arrows on the label and marks shown in the pictures
The 2 that did were older, silver rims. None of the black rims, including the new, unused rims I bought a year or 2 ago had any arrows or marks at all.

Fluffy Chicken- this is the opposite of what you have observed. Seems the addition of these wear marks was a bit random.