I have the older carbon Shimano 7900 C50 with alum brake surface. It could be worn off but looking to confirm there is a wear indicator hole. The online manual says: "The hollow on the opposite side to the valve hole is an indicator for the amount of rim wear." What-da??? Please in layman terms explain where it is suppose to be. I do have some micrometers so does anyone possibly know the minimum wall thickness??

Thanks a ton!!
Marty

You might have difficulty measuring the brake track thickness due to the bead hook. Something like this 1pc Wax Dental Crown Gauge Caliper Dental Surgical Instruments | eBay might work. No recommendations as to minimum thickness, did you check with the manufacturer?

Let me google that for you

first link has this image

I know how to google and have seen that many times. It's surely not my C50 rim?? I can't tell from the picture "where" it's suppose to be on the rim so can look closely in that area for a blemish or something indicating there was one at on time.

Thanks for the tip.... I work in QC and have a good tool to do it. I will see if I can find a wall thickness reference from somewhere but I have a hunch these did indeed have the ref hole at one time.

Dental calipers Reach around the bead hook and you can always Modify a cheap 'General tool' caliper.

Rarely does the brake pad take off aluminum in a smooth flat wear track.

"on the opposite side to the valve hole" i.e. if you rotate your wheel so the valve is at the top, look near the ground, or vice versa.

According to the manuals definition: "The hollow on the opposite side to the valve hole is an indicator for the amount of rim wear" you are saying it should be here as shown in pic. That was my interpretation as well. If that's the case sadly I believe I have worn these awesome rims out. If I would of done my home work sooner I would of put softer pads on. Shimano makes pads that are supposedly less aggressive on alum rims.

BIG BUMMER