Tony_G

I have a bike that is equipped with TRP-29 160mm cable disc brakes. This exact rotor here:

https://trpcycling.com/product/trp-29-slotted-rotor/

What is the wear limit (thickness) for this rotor?

jimc101

Have you tried contacting them? https://trpcycling.com/contact/

If in doubt, just replace, rotors are not exactly the most expensive part on a bike

Tony_G

Thanks for your reply. I have not contacted them. I thought some mechanic here might know.

About cost, last week I paid $31.50 for a pair on e-bay, from the cheapest reputable vendor. I'd like to milk out the last safe miles from the OEMs before replacing them. The pair that is on the bike is down to around 1.5mm, and the black paint on the cleaning grooves is wearing off.

dsbrantjr

The last place I'd cheap out on my bike is brakes.

Spoonrobot 

Regardless of the spec if you're wearing the clearing groove, you're on the last miles. 1.5mm is the Shimano standard and reasonable for the same style rotors from other manufacturers.

How are you measuring the thickness? A normal caliper often will overstate the thickness as rotors can wear concave or only have pad engagement below the edge of the rotor. I use a dental caliper (or outside diameter caliper) to measure a few spots around the rotor and retire once the lowest spot falls below my preference.

If you do hear back from TRP please share, I don't recall ever seeing their recommendation and a cursory look at their site didn't show anything obvious.

Marcus_Ti

TRP seems to think no one will ride their rotors enough to need to replace them....none of their documentation states a wear-limit, as far as I can tell. Ask them. They aren't alone, I remember reading a Zinn column where even he couldn't find SRAM/Avid documentation on wear-limit for those rotors.

Generally wear limits vary from 1.4mm (Hope) to 1.8mm (Some Magura) depending on the OEM. Generally....the wear limit is a loss of 0.2mm (Hayes, Magura, Hope) to 0.3mm (Shimano) from as-new thickness.

dsbrantjr

I use an Iwanson gauge, they are also good for measuring rim brake track thicknesses. Like this: https://www.ebay.com/itm/Crown-Gauge...cAAOSwoetdo-kn
There are also little ball adapters which fit onto a micrometer to measure past a ridge: https://www.ebay.com/itm/STARRETT-MI...wAAOSw8V9d0D8C

Tony_G

I’m measuring with a cheap $10 caliper purchased this week from Harbor Freight. I have checked the trashy tool against some quality feeler gauges. It measures a .88 mm feeler gauge as .93 on average.

Measuring the rotor I am taking care to avoid the outer edge, which just as you say, has outside tips that have no wear.

Today I emailed TRP. If they respond, I will post the info here.

AndreyT

Does that mean you replace your rotors after every ride?

If you do, then good for you, but I think everyone will agree that this does not make a shred of sense. And is actually a performance-degrading practice.

If you don't, then where do you draw the line? Where exactly does that "cheap out" begin? And that is the question the OP is asking.

dsbrantjr

I replace brake components when I get to the point where I am asking myself questions like the original one. I'd rather toss some cheap consumables early than press my luck, especially things like tires and brakes.

Tony_G

Update:

TRP replied to my email. Here is the spec:

"The wear limit or minimum thickness for the TRP 160-29 is 1.5mm."