When it comes to overhauling the Sumitomo 4-spot calipers it is not recommended that the two halves of the caliper are separated. However, there a some reasons why you might. I have done so on a few occasions. The overhaul kits I have used, including genuine, do NOT include the cross-over or bridge sealing O-rings. These are 12.6mm OD and 2.0mm thick and have a square cross-section rather than round like a conventional O-ring. Two are needed for each caliper. Conventional nitrile O-rings are DEFINITELY NOT suitable. O-rings could work, but they need to be made of a material that is unaffected by brake fluid and rated to withstand temperatures something like -20 to +200 degrees C. This means that a special material like Aflas or Viton is needed. Such materials are hard to find but available in round section O-rings. I cannot find in square section O-rings. As far as I have discovered, these O-ring seals are not available from Nissan. I discovered a UK based supplier of kits that include ALL the seals, dust covers and cross-over bridge seals. However, I have not been able to find somebody who sells the cross-over bridge seals separately. Does anybody know of a supplier of the correct O-ring cross-over bridge seal, please?

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I have bought a couple caliper rebuild kits from Weldon brake and clutch over the years. They have always had the cross over seal in the kit.
Maybe give them a call.
http://www.weldonbrakes.com.au

Thank you for the response. I will check with them. I was sort of hoping that there was somebody who would supply the cross-over seals separately. Kind regards!

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