Shimano hydraulic disc brake differences

[thelawnet]

Shimano manage to sell numerous different disc brake models at very different prices.

Please feel free to comment on differences.

From what I've seen:

MT200/M315/M365 (other codes may exist) - basic caliper
M395/M445/M446/M447/MT500 - supposedly 10% more effective caliper
M596/M615/M6000 - basically the same caliper as the above, but supplied as standard with the more rigid BH90 hose rather than BH59. The braking surface may also be narrower, as Shimano specifies that you should use discs with a narrower braking track on these. In addition, Shimano says these calipers are compatible with finned 'icetech' pads, whereas the cheaper ones are not.
M675/M6000/M7000/M785/M8000 - as above, but uses ceramic rather than resin pistons, while the hose joint is now a banjo type
M640/M820/M8020 - this is a 4-piston design and is more expensive/heavier

Levers:
essentially all cross-compatible, Deore & up are 'servowave', in terms of brake price differences, most is paying for the levers

MT201/M315 - these are 'three-finger'-size levers made of (non-stainless) steel
M365 - as above in rust-free alu.
M396 - the 'two-finger'-size lever in (non-stainless) steel
M425/MT500 - the alu version of that
M596/M615/M6000 - these have 'servowave' where the first of the braking stroke moves the pad faster than the second
M675/M7000/M785/M8000 - these use the same tooling, just minor differences. They have tool-less reach adjust (not sure what's wrong with an Allen key myself and I believe some early examples had a problem with this, as they moved around during riding), and biting point adjustment, though on the SLX models it is blocked off (hence this is a case of a feature being disabled to differentiate on price). The M8000s have slightly nicer, dimpled levers, then either the older XT or the SLX models. They should all still perform similarly to the Deore ones.

A set of the cheapest MT200/M315 brakes (with levers & pads) is around £25 off AliExpress. I guess more in the UK. The M365s are then £30, and then the M6000 around £60 off AliExpress. The M7000s are at £90, and the M8000s around £115.

Noting that Evans charges £50 to bleed a pair of brakes, it may be cheaper to buy new ones, especially as manufacturers seem to use the £30 brakes on bikes costing as much as £1500. You also get nice new hoses (some seem to provide pre-cut hoses, so it might be worth checking if they are ready to ride) and brake fluid.

Disc rotors:
Since 2009 Shimano has maintained a distinction between 'wide' and 'narrow' calipers, possibly dating from RT97 rotor and M975 introduced in 2007. As I understand it earlier caliper designs were 'wide', and newer designs are either narrow or wide. If a narrow pad and disc is used on a wide caliper, performance will be reduced, but the reverse shouldn't cause issues.



Cheaper (RT56 and below) rotors are softer and 'will become easily damaged' if metal pads are used. All the current rotors using wider tracks are resin-only. However you could use an older rotor with metal pads if you wanted to.

Higher end discs are 'icetech', which is to say a sandwich of aluminium between slices of steel. Aluminium having much better thermal conductivity, this should conduct heat away from the surface of the rotor and improve performance.

There are also 'icetech freeza' discs, which have an additional aluminium fin to conduct heat away.



Some of the discs are ridiculously expensive compared to say, car brake discs, a pair of RT70 'icetech' is around £40, and the RT99 'freeza' discs are more like £70. You can get a pair of basic RT30 discs for under £15 direct from China.

If you have six-bolt hubs then there are knock-off Chinese designs available, but they don't seem to be hugely cheaper, and for whatever reason they don't seem to make centerlock discs.

Pads:
If you have the cheapo rotors & brakes you're supposed to only use the B01s resin pads. Otherwise there's a choice of pads including with and without 'icetech', which in this case refers to aluminium fins on the pads to conduct away heat. Third-party pads may be cheaper and/or better.

[thelawnet]

There's a group test of brakes here:

https://enduro-mtb.com/en/best-mtb-disc-brake-can-buy/

It's not a very good test in that they don't isolate the different variables that are user-adjustable, specifically the choice of discs and pads.

From what I can see:

Deore (M6000) - standard stainless steel rotors (RT64), steel-backed resin pads (G02s)
Deore XT (M8000) - steel/alu/steel rotors (RT81, alu-backed resin pads (G02a)
Zee (M640) - standard stainless steel rotors (RT64), steel-backed resin pads (D01s)
Saint (M820) - steel/alu/steel finned rotors (RT99), alu-backed resin pads with fins (H01a)

The results appear to show much better initial deceleration with the 4-piston designs (Zee/Saint), however the cheap pads & rotors fitted to the Zee fade badly over a longer period of deceleration. There doesn't appear to be much performance difference between the Deore & the XT - around 10%, despite different piston material, better pads, and better discs.

Some piston stats:

Shimano levers (all): 10mm diameter
Older Shimano 2-piston calipers, including apparently the current lowest end models (I have some that I will dismantle at some point and check): 21mm diameter = 882π mm^2 area.
Newer Shimano 2-piston calipers: 22mm diameter = 968π mm^2 area (=+10% vs 21mm)
Shimano 4-piston: 2 * 16mm, 2 * 18mm = 1160π mm^2 (+32% vs 21mm/+20% vs 22mm)
Formula Cura 2-piston: 24mm = 1152π mm^2

Perhaps unsurprisingly the Cura 2-piston seem to offer the same power as Shimano's 4-piston design (noting as an aside that they are oval shaped albeit that the diameter quoted is the circular equivalent).

So some sort of idea what you get for your money:

1. M315 (etc) 21mm pistons, steel levers, cheaper hose - around £25
2. M365 (etc) aluminium levers - around £30
3. M445 (etc) 22mm pistons = +10% performance - around £40
4. Deore M615/M6000 stiffer hose, modulated levers, narrower braking surface (not an advantage per se, this appears to have been changed to lop 5 grams or so off the disc weight, and perhaps give a more modern looking design) - around £60

5a. SLX M675/M7000 banjo fitting, tool-less reach adjust, ceramic pistons (apparently more fragile but better for heat dispersal?) - around £90
6a. XT M785/M8000, biting point adjustment, dimpled levers on the M8000 - around £120

5b. Zee M640 - 4 ceramic pistons = 20% more performance, banjo fitting, Deore-type levers - around £175
6b. Saint/Deore XT M820/M8020 = same as Zee calipers, levers similar to M785/M8000. - around £250 for Saint or £180 for XT.

The rest of the differentiations come down to user pad/disc choice.

It's not clear why the Saint brakes are more expensive than the 4-piston XT ones, other than just market differentiation.

[Brucey]

FWIW differences in friction coefficient between different pads are usually larger than 10% and often larger than 20% so the differences between brake piston areas appear not to be of great significance vs other things.

Note also that you can usually fit a different sized rotor and get larger variations in brake power that way too.

Regarding ICE rotors there have been a few reports of the aluminium centre layer softening/melting with intense heat and the rotor failing that way. This is unlikely in normal use but might be a concern when thinking about alpine touring. BTW ICE rotors have a wear limit of 1.5mm, and are not that thick to start with, so may last less long than other rotors too. Having said that I have seen a set of ICE rotors worn to 1.25mm thickness and (amazingly) the rotors wore uniformly and didn't disintegrate despite the stainless steel layer being a tiny fraction of a mm thick once they were this worn. [The bike's owner had no idea they were this worn, BTW; best to check this often.]

Regarding brake power I like the better modulation of hydro discs when riding offroad but (larking about aside) it is rare that you have enough grip to exploit the full power of the brakes. On the road, you very quickly get enough power that the limitation to how quickly you can stop becomes how well you can modulate the brake.

It seems to me that having incredibly powerful brakes on a standard solo bike might feel great but when it comes to avoiding a collision or something it is actually not terribly useful; if you stop quickly from ~20mph with good brakes, you will stop dead in about 1s. This isn't long enough for even a very good rider to bring the brake up to full power and then modulate it deliberately so as to exploit the full power of such brakes. Arguably you would be better off with brakes that get you ~90% of the way to doing a stoppie, that you could slam on without any worries about going over the handlebars.

cheers

[thelawnet]

Here's the compatibility detail for rotors:

'SM-RT56/54/30/26/10 are for resin pads only. If use with metal pad, rotor will become easily damaged.
'Durability of B-type {wide} pad become shorter when the pad is used with narrow type rotor.'
'Narrow type 2 piece rotor are not compatible to caliper for Wide type rotor because of interference.'


'Do not use these combinations for a reason of interference between brake caliper and adapter'

BR T675, T615, M4050, MT500, M446, M3050, M395, M365, M315 {and the newer models} -
SM-RT900/500/99/99-A/86/81/76/70

I am not sure if there are any 1-piece centerlock rotors, but there is a 1-piece narrow 6-bolt rotor (SM-RT66), which should therefore work and is metal-pad compatible. This is in addition to older, wide-type rotors.



Here are Shimano's pad details:



Types (since 2000):

1. Type M01/M02/C01

= M555/C901 brakes (2000-2002)

2. Type M03/M04 =

M755 (2000-2002)

3. Wide ('B-type'):

M05/M08/B01s/E01s (2000-present on most mechanical disc brakes, sub-Deore hydros & some trekking-type hydros)

4. Old-type narrow (side mounting - 'A-type') (2003-2012 - standard pad design at Deore level and above)

A01s/M06ti/M06/M07ti

5. 4-piston ('D-type' - since 2009's M810 and all subsequent 4-pot calipers):

D01s/D02s = unfinned
H01a/H02a = finned
N03a/N04a = finned (new fin design for XTR M9120)

6. New-type narrow ('F-Type' - mounting position moved to centre to make them finnable - since 2011 XTR 985 to M9000 (not M9100 onwards), 2012 XT M785, SLX M666, 2013 Deore M615, Tiagra-level (and above) mechanical road discs):

F01/03 A/C = Finned (old fin design)
G01/G03 A/S/Ti = Unfinned
J02/04 A/C = Finned (new fin design)

7. K-type (K-type = unfinned, L-type = finned)

K02/K04/L02/L04 A/C/S/Ti (2015- on higher-end road calipers, and XTR BR-9100)

Backing plates:
A = aluminium
S = steel
Ti = titanium
C = composite

The servowave levers are as follows:

Servowave 1 - XTR M988 (not on M985/M987), Saint M810,M820, XT M775/785(not T785), SLX M665/M666/M675/T665 (removed from T675), Zee M640, Deore M596/M615 (not T615), M506

Servowave 2 (refined)- XTR M9020 (not M9000), M9120 (not M9100), XT M8000 (not T8000), SLX M7000, Deore M6000, MT500

[peetee]

Do be aware that buying Shimano brakes from a foreign supplier usually (but not always) results in a pair set up for right lever/rear brake operation. The opposite of the usual UK set up. Also Shimano supply different hose length options for both front and rear. Never assume the front hose will be long enough. Also, also it's not a given for Shimano brakes to be supplied with spare hose end fittings to be used after trimming to length, which given the two aforementioned factors may or may not be applicable, but probably will be.
Also, also, also, I have never used AliExpress. I did venture there once but thought their prices were to good to be true. I left empty handed assuming that they were (Amazon style) brokers and the goods were possibly non-genuine. I have fallen foul of this before. The items were superb replicas of Shimano brakes but one rubber hose hood was missing and the lever action was a bit poor.

[thelawnet]

I have ordered a few parts from AliExpress.

There is certainly fake stuff on there. I just bought some fake KMC chain links, but Ali refunded me with no need to return them. I can't find much evidence of fake Shimano parts though (there is 'Shinano', which is a different thing and fair game really). Amazon & Ebay are infested with counterfeit goods and there is no real Trading Standards any more, so you can sell fakes all day long in the UK.

The brakes seem to be slightly cheaper here in Indonesia, which suggests to me that they aren't in general sourced from a Chinese fake factory.

Most vendors on AliEXpress seem to offer a choice of right/front or right/rear. The hose lengths are also specified, and there are choices as to the pads.

[thelawnet]

Shimano have come out with some new disc parts.

There is BR-MT420, which is interesting in that it has 4 pistons. This is following on from last year's BR-MT520, which was apparently identical to XTR, XT, Saint in having four ceramic pistons.

MT420 has resin pistons, so it's a new model, as opposed to a rebadging of a previously pricey one. It does take the same pads so presumably the same braking force as XT apart from the slightly diminished cooling using resin pistons.

It's curious that they have 4 piston calipers at nominally Alivio spec level (though most bikes with even Deore drivetrain comes with the lowest spec of disc brakes so.rhat might be moot). The nomenclature is a little odd, as br-MT420 is 4 piston, comes with the better hose, should take the fancy finned pads, but br-mT500 has the old pad shape, old hose and 2 pistons.

The new levers are BL-MT401 and BL-MT401-3A/BL-MT402-3A.

The 3A model has the long levers and the other has the short one. However both long and short lever can be used with either BR-MT400 (2 piston) or BR-MT420 (4-piston), so the lever length is not apparently particularly tuned to the brake caliper.

Short levers seem to be preferred for actual mountain biking.

I guess as MTB hydraulic disc brakes get cheaper, and supposedly 'premium' designs are sold off with low spec names, that will eventually follow through to road bikes.

I'm sure it won't stop people believing they need a high-end groupset to ride on though.

[zenitb]

Super informative post as usual from you thelawnet. The pad compatiblity is particularly useful and I never realised there were wide and narrow rotors !!!

One other practical difference I would like to point out is the bleed screws. On the caliper the Deore and up brakes have a plastic/rubber cap you can remove so you can attach a hose/syringe. It also has spanner flats enabling you to open an internal valve allowing you to push/pull the fluid through and capture all the air that was in the caliper area in the syringe - just like bleeding car brakes in fact. I found this very effective when bleeding my Deore M505 brakes (which my LBS had utterly failed to bleed properly when they extended the hose).

I have just got a commuter bike with the cheaper M396 brakes and I notice it does not have the rubber/plastic cap or spanner flats .. just a simple recessed hex screw .. see my third picture attached. So how do you bleed them ? I have not needed to bleed the M396 brakes yet but I am wondering how this is going to work. I have a wrecked Deore M505 brake so I am wondering whether to just transfer the bleed nipple accross... or maybe buy a bleed nipple on eBay ?

Something to think about before cheaping out on sub-Deore brakes... unless anyone on the forum knows how they are bled ?

[Brucey]

there is a shimano document that explains in detail which rotors (with different track widths) go with which calipers.

The photo above of M396 caliper shows a bleed tube attached to the bleed nipple. The allen screw is simply a blanking plug for a cross-drilling, not where the tube is connected.

The intended bleed process for shimano brakes is that you attach a syringe of brake fluid to the caliper bleed nipple, and a funnel to the MC. Fluid is forced from the syringe and due to clever orientation of the transfer ports inside the caliper, air is swept out along the line to the MC and out into the funnel. This usually works OK provided the action is fairly vigorous and the caliper is correctly oriented. This procedure eliminates the possibility of sucking air in at the bleed nipple threads.

cheers

[zenitb]

there is a shimano document that explains in detail which rotors (with different track widths) go with which calipers.

The photo above of M396 caliper shows a bleed tube attached to the bleed nipple. The allen screw is simply a blanking plug for a cross-drilling, not where the tube is connected.

The intended bleed process for shimano brakes is that you attach a syringe of brake fluid to the caliper bleed nipple, and a funnel to the MC. Fluid is forced from the syringe and due to clever orientation of the transfer ports inside the caliper, air is swept out along the line to the MC and out into the funnel. This usually works OK provided the action is fairly vigorous and the caliper is correctly oriented. This procedure eliminates the possibility of sucking air in at the bleed nipple threads.

cheers

Ok yes I see the bleed tube is attached on that photo. Googling it looks like the recessed allen key is actually the bleed screw ??? .. I found this pic.

Going back to thelawnets post it does seem to be a difference between the cheaper and more expensive brake calipers - the cheaper ones have this system for some reason.

[thelawnet]

Super informative post as usual from you thelawnet. The pad compatiblity is particularly useful and I never realised there were wide and narrow rotors !!!

One other practical difference I would like to point out is the bleed screws. On the caliper the Deore and up brakes have a plastic/rubber cap you can remove so you can attach a hose/syringe. It also has spanner flats enabling you to open an internal valve allowing you to push/pull the fluid through and capture all the air that was in the caliper area in the syringe - just like bleeding car brakes in fact. I found this very effective when bleeding my Deore M505 brakes (which my LBS had utterly failed to bleed properly when they extended the hose).

I have just got a commuter bike with the cheaper M396 brakes and I notice it does not have the rubber/plastic cap or spanner flats .. just a simple recessed hex screw .. see my third picture attached. So how do you bleed them ?

There are two different designs:

BR-M395 (BL-M396 is the lever) uses a separate 3mm allen key to loosen the bleed screw.



BL-M505 is again the lever name, and comes with either BR-M445, BR-M446 or BR-M447.

You'd think they'd be all the same, but in fact BR-M445 & BR-M446 are as per the image above, with the 7mm socket, while BR-M447 is like BR-M395 with the 3mm Allen key.

So there is basically either a 7mm socket you tighten and loosen for the bleed hose, or a 3mm a bleed screw you tighten and loosen with separate bleed boss.

Otherwise in terms of hose to caliper, some use a banjo fitting with 4mm hex key, some use banjo fitting with a 3mm hex key, others are straight with a 8mm spanner,

Some fit pads with a snap ring, which has a 3mm hex head, and others just use the split pin