'Resin pads only'

[thelawnet]

I noticed this explanation in an old Shimano service leaflet

https://si.shimano.com/pdfs/si/SI-8CN0D-000-ENG.pdf

"• The SM-RT50 rotor should be used together with resin pads. If it is used with metal
pads, the pads will wear out very rapidly. Use the SM-RT61 for repair work"

Which is quite straight forward really.

They had two identical-looking discs:




RT50, RT60 (later RT61)

where one was 'resin pads only' and one wasn't (They also had RT75, which had a different inner construction, saving a bit of weight).

And they recommended that if you wore out the stock cheap rotor, then you replace it with the more durable one.

Now 20 years later, we have 'progress' in that they will no longer sell you the equivalent to an RT60 rotor. Nope, all such discs are now 'Pad lining shape compatibility': narrow only

https://productinfo.shimano.com/#/spec/ ... ke%20Rotor

So if you want to use metal pads with Shimano discs you'll need to replace your brakes as well. because Shimano won't sell you a rotor that works with the brakes specified on the overwhelming majority of MTB/hybrid bikes that is designed for metal pads.

[PH]

So if you want to use metal pads with Shimano discs you'll need to replace your brakes as well. because Shimano won't sell you a rotor that works with the brakes specified on the overwhelming majority of MTB/hybrid bikes that is designed for metal pads.

I've not looked outside of my own requirements, but I expect there's a choice of third party options, there has been for all those I've looked for.

[MikeDee]

I wonder what makes these rotors resin pad only. I don't think they are hardened stainless steel. Maybe Brucey knows.

[Brucey]

yes they are just not so hard as some other discs. What shimano call 'resin' pads are often called 'organic' pads by others. These frequently contain some metal particles; by the time the content is high enough that they are called 'semi metallic' you may be in trouble with high rates of disc wear again. But there is no standard for brake pads, so if you definitely don't want to wear out your discs, best to stick to shimano's resin pads.

cheers

[thelawnet]

yes they are just not so hard as some other discs. What shimano call 'resin' pads are often called 'organic' pads by others. These frequently contain some metal particles; by the time the content is high enough that they are called 'semi metallic' you may be in trouble with high rates of disc wear again. But there is no standard for brake pads, so if you definitely don't want to wear out your discs, best to stick to shimano's resin pads.

cheers

Shimano say the problem is with pad wear, not disc wear.... 'If it is used with metal pads, the pads will wear out very rapidly. '

[Brucey]

well I have only seen the results of trying this a few times; the wear rate of sintered pads may be higher than normal (e.g. in the dry), but it may not be higher than that of resin pads under all conditions. What is clear is that the disc itself soon gets badly marked up/worn when you use some pads other than those recommended.

I suspect that most other discs are made of martensitic stainless steel ( more or less the same kind as is used for stainless steel knife blades) but that the shimano discs in question are made from stainless steel which is closer to austenitic composition, but which contains both ferrite and austenite. The two materials would be expected to behave rather differently under conditions which might promote galling, which isn't a million miles away from what happens in a brake friction couple either.

In a former life I had some involvement with brake pads. I was lucky enough to spend some time with folk who had spent their lives working in the 'friction materials' business and their take on things was very interesting; they more or less confirmed that what I'd heard elsewhere i.e. that 'the composition of friction materials is a dark art'.

In the simplest terms you are after a friction coefficient that is stable under a wide range of conditions including a wide range of temperature and even when amounts of water are present. All with quiet operation and a low wear rate too. It is often the case that organic materials tend to 'go away' at temperature ( they outgas, burn, or otherwise create gas) but that a lot of metal to metal friction coefficients rise with temperature. The same pads can work differently with different disc compositions because the whole nature of the fiction couple is different. So some brake pads (sintered ones being a case in point) actually contain some metal ingredients which work as lubricants (with some disc materials and not others) at high temperatures, aiming to balance out the inherent rise in the friction coefficient with temperature.

If you use 'the wrong combination' this is very soon evident on a brake dyno, which usually simulates an intensive cycle of some kind. It doesn't however represent a typical use very well, which doesn't always involve much intensive braking; therefore the thing that is first apparent on the dyno (eg high pad wear rate) may not be the most striking thing in real world use.

cheers

[pwu]

RT62 in 160mm works with wide or narrow, saw it in one of the compatibility charts 2005 I think, I bought a pair for £12NOS when my rt54 wore down to 1.5mm. I have m395 brakes with Noah and Theo sintered pads.

As you can see m525 and other b01s pads are compatible with RT62 160mm but not 180mm or 203mm because the rotor area is smaller.

[thelawnet]

RT62 in 160mm works with wide or narrow, saw it in one of the compatibility charts 2005 I think, I bought a pair for £12NOS when my rt54 wore down to 1.5mm. I have m395 brakes with Noah and Theo sintered pads.
Screenshot_20201006-132532.png
As you can see m525 and other b01s pads are compatible with RT62 160mm but not 180mm or 203mm because the rotor area is smaller.


IMG_20200608_173343409.jpg

I have a spreadsheet:

https://docs.google.com/spreadsheets/d/ ... 1666210379

They introduced the RT97 rotor with the narrow track in 2006.



The pad type was not changed with that year's XTR brake release; at that point they had a 'narrow' pad and a 'wide' one.

The wide pad continues to this day, but the narrow pad was redesigned. The old one looks like this:



The new one has the mount in the centre (obviously meaning the calipers were also changed), so they could add cooling fins.

RT97 was no lighter than RT96:



but perhaps it saved manufacturing costs or something.

Anyway, it's easy to identify the compatible discs: anything starting with a 5-, 4-, 3-, 2-, 1-, etc., is 'resin pads only', while anything starting 6, 7, 8, 9 is not.
For the 'wide' vs 'narrow' braking track', they never made a 'narrow' 5-series, so you have to seek out RT62/RT63/RT77/RT96



I don't think there is any issue with the larger disc sizes on the B01s pad:

The M575 caliper uses B01s pads, and it's noted to be ok with 160,180,203mm wide types.