Shimano says its Tourney mechanical disc brake is "designed for resin pads only". What is it about the design of a brake caliper that makes it suitable only for resin pads?

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    Believe it is simply that all of the rotors that are "officially" compatible with it and part of the Tourney line are resin-only rotors, so someone searching for this part to find out what brake pads to replace with would be expected to need resin pads.
    – Affe
    Jan 28, 2021 at 21:40
  • But doesn't that explanation just punt the question downfield? Why would resin-only rotors only be "officially" compatible with the caliper, if metal pads would not be incompatible with the caliper? Why do some other calipers that ship with resin pads not have that "official" restriction? Is the restriction 100% marketing and 0% engineering?
    – Tim
    Jan 28, 2021 at 23:29
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    The mention of “resin pad only” is in reference to the rotor, not the caliper. It’s a subpoint of the “uses centerlock rotors!” bullet point.
    – MaplePanda
    Jan 29, 2021 at 0:45
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    It does appear that in the current product lineup there are no metal pads sold in the 'wide' format so in fact for actual shimano parts there are no metal pads that physically fit into the caliper.
    – Affe
    Jan 29, 2021 at 20:39
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    Does this answer your question? Why would hydraulic calipers (not rotors) only be compatible with resin pads? Apr 6, 2022 at 11:05

2 Answers 2


It's not the caliper, it's the disc (it's made out of a soft material). If you put a harder brake pad, it would wear the disc too fast. Actually look at the disc. On my discs it's written: "for resin pads only".

  • But my question is, why can't metal pads be used with these calipers, assuming that a metal-pad-compatible rotor would be chosen? Where exactly does the incompatibility reside? Thickness of the rotor or thickness of the pad? Pad travel limitations?
    – Tim
    Jan 29, 2021 at 19:42
  • It's a good question. Looking at Shimano's spec listings, a resin only rotor like the SM-RT56 is made of polished stainless steel, as is the SM-RT64, which can be used with metal pads. In addition, higher end rotors are made by sandwiching aluminum between two faces of stainless steel and these are fine for use with metal pads (at least until the aluminum is exposed). While I don't claim to know why this discrepancy exists, it may have more to do with the design of he rotor in regards to the size and pattern of the holes stamped around the rotors business edge.
    – Jeff
    Feb 11, 2021 at 15:51
  • @Jeff I believe it’s the quality of the heat treatment.
    – MaplePanda
    Mar 22, 2022 at 19:11
  • @MaplePanda That's a good thought. More true than my type of hole theory. I just notice that regarding Shimano, the resin only design seem to all have several small round holes while the ones ok for metal have larger polygons for open area. Though in the past Shimano rotors that were good for metal pads had the small round holes that were far fewer in number (like the RT60 & RT61's). Still in use on my '03 SJ and on the rear of my '16 S-works SJ. Never had to true them but wouldn't wanna see em on a scale.
    – Jeff
    Mar 24, 2022 at 4:25

I have used metallic pads on low-end shimano calipers (BR-M365) and noticed something unusual: one caliper definitely started to leak oil through the piston seals. When bleeding the brake, I noticed very black oil coming out, something that should not be. The black contamination in the oil was either brake pad dust, or material from the pistons themselves. Either way, I think there is some incompatibility between metallic pads and low-end brake calipers. the exact reason remains to be found. Some say, the pistons on these are made of resin, but I cannot imagine how that would pass a safety test. after all, brake pads heat up, and brake oil is supposed to tolerate temperatures beyond 200°C. I don't see how a piston made from plastic would hold up to these temperatures.

  • I had the same experience with a BR-M400 caliper. After a long descent the caliper lost oil. After a bleed everything looked fine again, but I didn't want to use metal pads with this caliper any more. Apr 6, 2022 at 11:04
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    The black oil is very well known among Shimanos. Has to do with being poorly sealed from the elements and having a soft, easily scratched master cylinder bore. Plastics hold up to 200 degrees just fine. The phenolic resins used are more than capable. As a point of interest, Kapton (polyimide) is good to 400 degrees C briefly.
    – MaplePanda
    Apr 6, 2022 at 21:02
  • The pistons of the deore xt BR-M 8100 are definitely made of plastic. I broke one. (yes, out of extreme stupidity). But unless mis-treated, they work perfectly.
    – Burki
    Apr 7, 2022 at 6:41
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    @Burki The pistons of your calipers are made of ceramic, not plastic. That's why they break easily when mistreated.
    – airace3
    Apr 7, 2022 at 8:35
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    @Burki yes, SLX and higher end groups (including Zee and Saint) have ceramic pistons, Deore has resin pistons and groups below Deore have alluminium pistons.
    – airace3
    Apr 7, 2022 at 10:36

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