Pads for Shimano GRX BR-RX400 disk brakes

[Retrobyte]

I have moved into the 21st century by buying my very first disk brake bike last weekend - a second hand Norco Search to replace my V-brake equipped hybrid as my daily commuter. Loving the upgrade so far, the Norco is a nice ride and the difference in braking feel and efficiency is light and day. That gives me food for thought when I reach the stage of replacing my rim brake roadie at some time in the future (not planning to do so at this stage though).

Given this is my first bike with disk brakes I will be learning new disk brake maintenance and repair skills soon enough, which I'm ok with since I'm the family bike mechanic by default anyway. I understand the fundamentals of hydraulic disks having worked on cars so know what to expect in terms of changing pads, bleeding brakes, aligning pistons etc.

A couple of really basic noob questions if I may -

1. How many kms can I expect to get from a set of pads? My commute is pretty flat with no excessive braking needed most of the trip, however I'm no lightweight (plus the weight of my pannier) and the cyclepaths still have areas of running water and muddy puddles, so I assume both those factors will exacerbate pad wear?

2. The bike has Shimano GRX BR-RX400 brakes - will any generic Shimano pad fit these calipers?

3. Any recommendations on good replacement pads when the time comes?

[warthog1]

There are some pad options at the bottom of this page;

https://bike.shimano.com/en-EU/product/ ... 400-R.html

Can't advise which to use though.
I am a disc brake newb with same calipers, so also interesed to see what is recommended.

[Tim]

Shimano Tech Docs to the rescue.
The exploded parts diagram shows you the pad options.
https://si.shimano.com/api/publish/stor ... -4574B.pdf

[Retrobyte]

Shimano Tech Docs to the rescue.
The exploded parts diagram shows you the pad options.
https://si.shimano.com/api/publish/stor ... -4574B.pdf

Thanks, I did find that earlier, however that part number draws a blank at Bikebug, Pushys, 99Bikes etc, so I wonder if they go by a different part number in Australia. Would have thought that pads for a GRX caliper would be pretty standard across the Shimano range?

[Duck!]

The 05 pad compound is new, and not one I've seen before, and might not be available here yet. Other pads in the K or L series will suit (they're shared with the road disc brakes).

[Retrobyte]

I was hoping you'd take the bait and join the thread, Duck - always good input, thanks

[Mr Purple]

Shimano Tech Docs to the rescue.
The exploded parts diagram shows you the pad options.
https://si.shimano.com/api/publish/stor ... -4574B.pdf

Thanks, I did find that earlier, however that part number draws a blank at Bikebug, Pushys, 99Bikes etc, so I wonder if they go by a different part number in Australia. Would have thought that pads for a GRX caliper would be pretty standard across the Shimano range?

The LO5A? They're standard Shimano Resin disc pads with fins. The KO5S looks to be the version without fins.

Both are available if you can actually find stock:

https://www.pushys.com.au/shimano-br-r9 ... -fins.html

Which you can't.

Swissstop do make an alternative which is the Disc 34E. Though no fins.

Stock is a major issue. I'm 6700km in on my resin Shimano pads on my road bike and starting to think about replacing them now - have gone with the Swissstop mentioned above.

[Retrobyte]

I'm 6700km in on my resin Shimano pads on my road bike

Wow, sounds like I don't need to worry until next year, although I think I weigh a bit more than you, which will probably wear pads quicker for me

[Mr Purple]

I'm 6700km in on my resin Shimano pads on my road bike

Wow, sounds like I don't need to worry until next year, although I think I weigh a bit more than you, which will probably wear pads quicker for me

I am light, but probably make up for it by doing a lot of high speed descents. I'm a bit OCD about brake cleaner use though.

The hard bit is telling if they're even due for replacement now. There looks to be a good few millimetres of compound on there still. But I figure it's better to replace them before I find out they're down to metal!

[robbo mcs]

Wow, sounds like I don't need to worry until next year, although I think I weigh a bit more than you, which will probably wear pads quicker for me

Keep a close eye on them though.

For example, I have a couple of road bikes with shimano ultegra discs. I'm pretty light, generally ride in semi rural or rural environments where there are not many intersectiins or traffic lights, and tend to get 10k from the fronts, more for the rear.

However, on my bike with grx, I ride more when its wet, dirty roads, gravel, sometimes with more weight from loading the bike. I only got 3.5k from the front, so a very big difference. I thing the wet, dirty stuff just grinds them down.

My grx must be slightly different to yours because it uses the LO3a pads, which are the exact same as my ultegra road bikes.

Also, as others said, there is a massive shortage of shimano pads at the moment, so might need to look at swiss stop or others

[Duck!]

My grx must be slightly different to yours because it uses the LO3a pads, which are the exact same as my ultegra road bikes.

The difference is in the pad compound, the specifics of which I don't know.

A brief breakdown of Shimano brake pad codes....
The first letter identifies the pad shape. All variants within this code are interchangeable. The second & third digits refer to the pad compound; the 0 is currently redundant, but provides for future evolutions... Generally, odd numbers refer to resin compound, even numbers to metal compound, although there are some exceptions. Higher number is an evolution of the compound. The final letter notes the backing plate material, A=aluminium, S= steel, C=composite aluminium/steel (only on metal compound pads with cooling fins) or Ti=titanium.

Over the last ten years or so, Shimano have offered the option of pads with or without cooling fins on their mid- to high-level brakes. For road/GRX, the paired series are K without cooling fins and L with them. There are other pairings on the MTB side of things, but they're not applicable to this thread.

[Mr Purple]

Would anyone be concerned about running the Swissstop Disc 34 in place of the LO3A on a road bike?

They don't have the cooling fins but from what I can see that's not really a huge drama in most situations.

[Retrobyte]

Would anyone be concerned about running the Swissstop Disc 34 in place of the LO3A on a road bike?

They don't have the cooling fins but from what I can see that's not really a huge drama in most situations.

I would assume the cooling fins are most useful on long descents where there is a lot of heavy braking, to reduce brake fade as the pads heat up

[Mr Purple]

My thought too. Given most of my descents are <2km and I'm not really touching the brakes (except at 60km/hr heading into the Stop sign on Cootha) I don't think I really need the fins.

Will report back.

[Duck!]

Changing to unfinned pads won't make any difference in most situations, but when pushed hard they can suffer fade and glazing, especially resin compounds. The fins do help in these situations.

[robbo mcs]

Would anyone be concerned about running the Swissstop Disc 34 in place of the LO3A on a road bike?

They don't have the cooling fins but from what I can see that's not really a huge drama in most situations.

I recently did exactly that on my road bike, as I couldn't get the shimanos. Changed over no problems, bedded them in on the first ride, and now done around 700km on them. I haven't noticed any difference in stopping power or noise. However, I am generally light on the brakes.

[Mr Purple]

Thanks. I figured as such - also that at 61kg I'm hardly likely to be overheating any braking system.

[dmwill]

Galfer is another option to consider. Ultegra bakes with XTR Rotors in my case.

Used Swissstop 34 previously - they're quieter than Shimano pads, but the dust is terrible. I suspect the dust makes a mess around the pistons/caliper body making the pistons slow/sticky when retracting - so I'd always get rubbing after hard braking.

Switched to Galfer - less dust, even quieter, no rubbing issues as yet (6months/2000kms in).

[Mr Purple]

Galfer is another option to consider. Ultegra bakes with XTR Rotors in my case.

Used Swissstop 34 previously - they're quieter than Shimano pads, but the dust is terrible. I suspect the dust makes a mess around the pistons/caliper body making the pistons slow/sticky when retracting - so I'd always get rubbing after hard braking.

Switched to Galfer - less dust, even quieter, no rubbing issues as yet (6months/2000kms in).

Should probably have checked this thread after a year ago; I've been experiencing much the same issue with the Swissstop the whole time. Nothing major, but I tend to get a bit of rubbing after hard braking. I thought it was a hydraulic issue but may just be the pads.

I picked up a few sets of Shimano when they were actually available so I'll replace those.

How long is everyone getting out of discs? I'm beginning to suspect mine are 'not quite flat' but will give them a measure. They are 15,000km old.

[Zippy7]

In my experience, mileage from disc brake pads depends on the terrain you ride, as well as the weather.

I basically used/killed a new set when I spent 2 weeks in France on a cycling holiday, staying at La Chambre, Le Bourg D'Oisans, and Briancon. Up and down hills ate the pads really quickly and I needed a new set when I got back.

Weekend riding and wet weather would also increase the rate of wear (I'm in Sydney).

On the other hand, I got a lot more mileage from just plain commuting.
As for fins/no fins - I had fins for France, but then swapped to no fins as it was a lot cheaper for me and I didn't notice any difference.

YMMV.

[Arbuckle23]

The fins look better in the caliper. Yes I am an idiot

[Mr Purple]

Not sure if this is the right spot, but I don't really want to start a new thread for it!

How do you tell if your discs need replacement? I've got a set of Ultegra discs with 18,500km on their third set of pads. They've recently started making some decent screeching noises intermittently under dry braking and there's plenty of meat left on the pads. Their thickness is pretty much as new but the braking surfaces have some visible scoring in them. Seem to work fine, just intermittently noisy.

New disc time? And if I replace the discs am I likely to have to do any thing to adjust the pads?

[CmdrBiggles]

Not sure if this is the right spot, but I don't really want to start a new thread for it!

How do you tell if your discs need replacement? I've got a set of Ultegra discs with 18,500km on their third set of pads. They've recently started making some decent screeching noises intermittently under dry braking and there's plenty of meat left on the pads. Their thickness is pretty much as new but the braking surfaces have some visible scoring in them. Seem to work fine, just intermittently noisy.

New disc time? And if I replace the discs am I likely to have to do any thing to adjust the pads?

If visible and serviceable pad surface is present, then squealing can be contamination of the brake surface and/or rotors.
Flush with water first, then degrease, flush thoroughly again and dry down rotors.
18,500 on a set of brake pads?? Are you sure?? I have Formula X brakes on my MTB and even with hard use (commuting, bushbashing etc.) will get around 6,000km; I replaced them recently because of scoring; the rotors are in mint condition though.

If scoring is present on the pads, replace them. Very easy to remove and replace pads, the only caveat being alignment of the brake mechanism against the rotor during reassembly. A stopper must also be inserted immediately the brake pads are removed, with the replacement pads readied for quick insertion. The rotors should be within the minimum serviceable wear-down thickness, usually printed somewhere on the actual rotor. Replace the rotor(s) if the wear-down is greater than the minimum specified (use a vernier caliper to check the thickness).

[Mr Purple]

e and serviceable pad surface is present, then squealing can be contamination of the brake surface and/or rotors.
Flush with water first, then degrease, flush thoroughly again and dry down rotors.
18,500 on a set of brake pads?? Are you sure?? I have Formula X brakes on my MTB and even with hard use (commuting, bushbashing etc.) will get around 6,000km; I replaced them recently because of scoring; the rotors are in mint condition though.

No, the 18,500km is on the rotors! The pads have 4200km and look brand new.

The scoring is also on the rotors though they're still well above the minimum thickness. I'm completely OCD about maintenance and the bike was cleaned and brake cleaner applied before today's ride so I don't think it's contamination.

What I suspect has happened is that the rotors have been somehow slowly scored throughout time, wet conditions and mud, and just aren't as flat as they should be.

[CmdrBiggles]

Replace the rotors.
And the pads.

Move on.
While I don't have OCD, I am fastidious with maintenance and know from long experience when to make the call, irrespective of whether it will cost a fortune or not, "just do it!" . End of the day, all the maintenance in the world isn't going to make them look new again when they are scored and potentially well below minimum thickness — you have had more than a very good amount of time and kays on the rotors!