Brad The Bike Boy: 320mm / 6 bolt front brake disc options and rambling

Saturday, July 4, 2026

320mm / 6 bolt front brake disc options and rambling

Front brake discs for 320mm, 6 bolt applications. You know, pretty much everything Ducati, Aprilia, Guzzi from mid 90's to 2008 ish.

I had to replace some on a Monster S2R1000 which are black carrier. That makes them a bit harder to find. Metalgear don't list anything black carrier for any Ducati, even though the SC/GT1000 and M696/796 run them. So with Melissa's help I found a Metalgear option in the end under an "Aprilia" part #. Melissa is certainly very helpful should you need options and can search their offerings via the mounting and disc diameter specs.

There were OEM 4.0, 4.5 and 5.0mm thickness discs in these discs. If you're after gold centre discs, you can still buy them as genuine Brembo parts in places other than Australia it seems.

The 90's "swiss cheese" round hole carrier discs were all 4.0mm and used on most Ducati models 1989 to 2000 ish.

Superceded around 2000 by a triangular pattern carrier disc.

The "snowflake" aluminium carrier discs that came with the 996 and other higher spec models - ST4S, MS4, etc - were 5.0mm. And I'm sure there was a 4.5mm version of them for 998R maybe? 748R version had 15mm offset, compared to the 10mm offset everything else had.

On pretty much all of them, the wear limit is 0.4 / 0.5mm under original thickness, even though they're the same disc and carrier pattern. No idea what that's about. But it can define the applications. Certainly the 5.0mm discs were as eager to warp as the 4.0mm discs.

The original Brembo discs on the S2R1000 are 4mm thick, triangular steel carriers and 1685gms.

I ended up fitting NG1060, which are Spanish as was the owner and he didn't mind some gold instead of black carriers. They are 5mm thick, like the 996 Snowflake style Brembo disc, and have steel carriers. 1780gms each. The carrier looks like it's made to take smaller discs as well.

Metalgear options: Black carrier 21-069-A-BK. The A denotes aluminium carrier, BK black. 4.5mm thick. And a gold -GL version too.

Gold carriers used to come in GL and GD - light and dark gold. but it looks like GD are no longer supplied as I write this (07/2026). Light is more the washed anodised look, dark like gold paint. The main variation in these is the carrier style and thickness.

21-015-A-GL and 21-142-A-GL are the ones I've used most often. Thicker spoke carriers with less spokes or thinner, more ornate style carriers - that sort of thing. 4.0mm thick. 1320 or 1380gms. While that 300 - 400gms is not a lot and close to the centre meaning it has a smaller inertial impact than unsprung weight impact, it's still a saving.

21-015-A-GL

Under the 21-142-A- number there are now 3 options: GL, GL-D1 and GL-D2. GL are a variation of the "triangular" style above, GL-D1 are the "swiss cheese" and GL-D2 are the "triangular".

21-104-A-GL are the snowflake style, 5.0mm thick. Also comes in a -ABS "drilled for ABS ring" version.

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