Fitting a 996S brake master-cylinder to a 999S

For anybody that is wondering, the radial master-cylinder from a 996S will fit onto a 999S. I also suspect it will also fit any 748 / 916 / 996 / 998 for that matter.

In my case the replacement was necessary as the original master-cylinder had failed. Forged and billet master-cylinders are also available but the 996S master-cylinder includes a brake-light switch. Personally I have never found the brakes to be wanting on my 999S (yes I do the occasional track day) so the extra expense and hassle of the brake-light switch didn't add up in my opinion.

Since the 999 and 996S (plus 998S and 998R for that matter) use the same brake calipers I knew the piston ratios would be compatible.

The only real work was removing the 999 fluid reservoir (it interferes with the throttle cable) which involves fitting a bleed nipple to the master-cylinder (M10 thread) and creating a new fluid reservoir bracket.

The brake lines also require consideration because they mount vertically on the original master-cylinder and horizontally on the radial master-cylinder. Here it is best to also replace the brake lines with ones that have an integral 90 degree bend at the top.

Electrically it is 100% compatible.

For anyone that is interested (or prepared to host them) I have more comprehensive instructions available for the conversion.