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?
Asked
Active
Viewed 502 times
1
-
1Believe 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 '21 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 '21 at 23:29
-
Basically yes? Although possible more legal than marketing. We're talking about brake components the manufacturer certifies as compatible with each other to protect life and limb. The manufacturer doesn't have much incentive to certify broad compatibility with other parts outside the Tourney line. OEMs may occassionaly do something like slap a Tourney FD on an otherwise Altus bike, but for something as important as brakes using components that have been tested together and are listed as compatible by the manufacturer matters! – Affe Jan 28 '21 at 23:52
-
1The 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 '21 at 00:45
-
But aren't there some CENTERLOCK rotors that work with resin or metal pads? That is what makes me think there must be some feature of the caliper itself that prevents use of metal pads because the only compatible rotors are resin-only. Are metal-or-resin rotors not the same thickness as resin-only? Or is the contact-surface a different width? – Tim Jan 29 '21 at 16:10
-
@Tim the Tourney level centrelock rotors are only compatible with resin pads. There’s nothing stopping you from using better rotors, but pairing $70 rotors with $30 calipers isn’t very common. – MaplePanda Jan 29 '21 at 19:17
-
@MaplePanda: I understand why some rotors are not compatible with metal pads. But my question is, what design feature make calipers compatible only with resin pads? Or makes calipers compatible only with rotors that are compatible only with resin pads? – Tim Jan 29 '21 at 19:38
-
2It 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 '21 at 20:39
-
@Tim Apart from what Affe mentioned (an excellent point by the way), there is nothing that says the CALIPER is incompatible with metallic pads. The “for resin pad only” you see on the website is in reference to the ROTOR. – MaplePanda Jan 30 '21 at 00:23
-
@Affe: So if I understand you correctly, there are no Shimano metal pads in the right size for the caliper; it's not that the calipers are by design unsuitable for metal pads, e.g. the pistons don't squeeze tightly enough or something like that? – Tim Jan 30 '21 at 13:40
-
Orthogonal aside if this is related to your other question about building up a frame, have you ever owned a bike with cheapie mechanical discs? It is not a pleasant experience – Affe Jan 30 '21 at 23:13
-
Metal pads are more expensive than the Tourney brake system. Not an answer but reason enough for me to stay with resin. – Jeff Feb 11 '21 at 15:36
-
@Affe: Always had rim brakes. – Tim Feb 11 '21 at 18:37
-
imo the only time I would ever buy mechanical disks again is if it were a back country tour and field-servicability were critical. They are a huge PITA. Either good old reliable V-brakes or mid-grade or higher hydraulics. (maybe a super fine-tuned downhill racer too where you're carefully tuning everything before every ride anyway and fluid heating is a problem, but then you wouldn't be looking at the cheapest possible mechanical caliper ;) ) – Affe Feb 11 '21 at 18:39
-
@Affe: Not putting on high-end brakes just yet because the bike might not be suitable for the person I'm building it for. She has ridden a step-through all her life but she wanted to try a MTB. I'm not expecting her to feel comfortable on the bike. – Tim Feb 11 '21 at 21:40
-
3Does this answer your question? Why would hydraulic calipers (not rotors) only be compatible with resin pads? – bernhardrusch Apr 06 '22 at 11:05
2 Answers
5
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 '21 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 '21 at 15:51
-
-
@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 '22 at 04:25
2
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.
Jonas Léchot
- 21
- 1
-
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. – bernhardrusch Apr 06 '22 at 11:04
-
2The 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 06 '22 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 07 '22 at 06:41
-
2@Burki The pistons of your calipers are made of ceramic, not plastic. That's why they break easily when mistreated. – airace3 Apr 07 '22 at 08:35
-
-
1@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 07 '22 at 10:36
-
To add to @MaplePanda / temperature tolerant plastics: Polyimides typically also handle temperatures in the 200°C long-term. But they're expensive, on the order of 300$/kg so nothing to construct cheap parts out of it. – chichak Apr 11 '22 at 20:47