Tech Zone > Aircooled RD Tech Help 250cc and Above

RD400C brake calliper (twin piston) torque settings

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mutley:
Hi guys, I'm overhauling the rear brake calliper (I assume identical to the front) on my RD400C.

I was surprised how tight the two large main bolts that secure the two halves of the calliper were, I had to use a breaker bar on the socket to get them free.

So I now have a newly re-painted overhauled calliper with lovely new seals, and bores and pistons you could eat off.  :) So I am ready to re-assemble.

Does anyone know the correct torque settings for those large bolts (ideally the smaller hex-bolts as well).

Many thanks in advance.

mervin:
have you downloaded the workshop manual from here   https://www.aircooledrdclub.com/manuals.html

mutley:
Thanks mervin, didn't know that was on here. 44 years of fettling it and all done without the w/shop manual until now  :o

Replacing the bolts 'every 2 years was interesting. I'll be re-using the originals  Something to think that I should be on the 23rd set of bolts though. . .  ;D

5port:

--- Quote from: mutley on May 09, 2021, 10:04:39 AM ---Thanks mervin, didn't know that was on here. 44 years of fettling it and all done without the w/shop manual until now  :o

Replacing the bolts 'every 2 years was interesting. I'll be re-using the originals  Something to think that I should be on the 23rd set of bolts though. . .  ;D

--- End quote ---

Yes, interesting.  Usually, bolts that are marginal on stretch are single use but, I don't see them often lifed, just renew if disturbed.  However, to have a "life" you would presume that they are operating within their fatigue range.  ???  Hmmm.  They are big bolts.  I wonder if someone cocked-up the stress loading calculation at Yamaha 50 years ago?

5port 

betty foRD:
I suspect it’s likely that since that calliper design was licensed from Lockheed, the accompanying critical service guidance was adopted for good measure or for contractual reasons. Either way, you can imagine that in an aerospace environment, periodic replacement of stressed components like that would be typical.
No one should loose sleep by ignoring on an RD, especially as now the ‘extended field data’ confirms its well within application requirements.

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