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Monday 20 January 2020

Shimano XT and SLX brake pads

The brakes on all our bikes now use the same styles of Shimano pads. The G-series, G03A, G03S, G04S or the J-series J04C, J03A etc.

I've been trying to work out the most appropriate pads to buy. My problems started when I was trying to find out what the difference was between G03A pads and G03S pads!

Shimano have a brake pad selector page, that is intended to guide you through to get the most appropriate pads:
That goes so far but often throws out multiple choices with no explanation of the differences.

Working the other way round. It is fairly easy to get generic information on resin, sintered or semi-metal but translating that in to which Shimano part number that relates to, can be confusing and is often contradictory.

As far as I can work out, in summary:
Resin (Organic) = For dry or rainy days. Quick to bed and more control.
Metal (Sintered) = For muddy, wet, gritty conditions. Last a lot longer. Take a lot more bedding in.
One other thing that I found out quickly about metal, they can be noisy. They Squeal.

In addition, some disc rotors are not compatible with some brake pad compounds. Most, if not all, discs are compatible with resin pads but not all are compatible with the metal compound pads. Many rotors have 'Resin Pads Only' engraved on them. Some of our disc rotors have that engraved on them.

Shimano simply state the following for the use of each type:
Resin: silence and controllability
Metal: durability and braking power

The symbols on the packaging provides some details to expand on that but that is not easy to search for on the internet. I have interpreted the information I have found, as best I can, and presented it here for my own use in the future. There is no reason for you, the reader, to trust my list any more than any of the hundreds of others out there on the internet.

Shimano Markings:
First letter = Shape. Both the G and J fit the dual piston XT and SLX brake callipers.
J has cooling fins
G does not have cooling fins
There are also 4 piston callipers, they use different pads.

Middle numbers = brake pad compound.
01, 02 and 03 appear to be updates of the resin formula. 03 being the most recent.
04 are always metal pads

Last letter = backing material:
A = aluminium (heat transfers to the calliper and hydraulic fluid which risks the brakes locking on)
S = steel (heat transfers to the rotor which risks brake fade)
Ti = titanium (heat transfers to the rotor which risks brake fade)
C = combination, stainless steel with aluminium fins
The heat sink fins, fitted to some pads, are obviously intended to mitigate the disadvantages of each of the above materials.

J03A, J02A 
Resin pad with anti-fade heat sink 
Metal pad with anti-fade heat-sink 
G03A, G02A 
Resin pad with aluminium back plate 
G03S, G02S 
Resin pad with steel back plate 
Metal pad with a steel back plate 
Metal pad with a titanium back plate 

I can't find enough reliable information on other makes of brake pad. I'm sure there must be good alternative pads but the only way to know is to try them, so for the time being, I'm sticking with the genuine Shimano pads.

A friend likes Noah and Theo pads. These are available from eBay. I'll give them a try one day.


I still don't know, for sure, if I should buy steel or aluminium backed but for my riding, it probably does not matter.

Metal pads are probably longer lasting for the muddy riding I do in the winter but I am less likely to be comfortable with the feel. On top of that, my disc rotors are not compatible with metal!

The following look like the best choices, which are compatible with both SLX and XT brakes:
J03A resin pads with heat sink
G03S resin pads with steel backing
Alternatively, J02A or G03A would be perfectly adequate.



My new bike has 4 pot Shimano brakes so takes different pads.
Based on the above, the standard D03S pads will suit.

I failed to stop the 4 piston Shimano callipers from squealing, so I swapped them for Shimano SLX 2 pot callipers and I am much happier.



The source, the Shimano web site:

Brake Callipers
We have XT and SLX brakes in use. These are or are similar to the current M8000 and the M7000 brake callipers:



Unknown said...

Thanks, great info.

Carlos said...

Why you say that aluminium transfers heat to the calliper and hydraulic fluid? Alumimium blocks heat very well.

John C Brown said...

That's what I read while researching this article.
Aluminium is a good conductor of heat. It is used for most heat sinks on electronic chips.