Author Topic: RD400C brake calliper (twin piston) torque settings  (Read 333 times)

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Offline mutley

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RD400C brake calliper (twin piston) torque settings
« on: May 08, 2021, 04:53:08 PM »
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.

Online mervin

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Re: RD400C brake calliper (twin piston) torque settings
« Reply #1 on: May 08, 2021, 07:31:09 PM »
have you downloaded the workshop manual from here   https://www.aircooledrdclub.com/manuals.html
If you get to thinkin' you're a person of some influence, try orderin' somebody else's dog around

Offline mutley

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Re: RD400C brake calliper (twin piston) torque settings
« Reply #2 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

Offline 5port

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Re: RD400C brake calliper (twin piston) torque settings
« Reply #3 on: May 09, 2021, 11:13:52 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

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 
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Online betty foRD

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Re: RD400C brake calliper (twin piston) torque settings
« Reply #4 on: May 09, 2021, 12:54:51 PM »
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.
Rev 'em till they rattle

Offline 5port

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Re: RD400C brake calliper (twin piston) torque settings
« Reply #5 on: May 09, 2021, 01:50:35 PM »
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.

Yes, agree that they seem to last the test of time and abuse!  :)

5port
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Offline mutley

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Re: RD400C brake calliper (twin piston) torque settings
« Reply #6 on: May 11, 2021, 03:00:41 PM »
Always puzzled me why Yamaha moved to a single-piston sliding caliper design after the C as it seemed far from an improvement. I remember doing stoppies on my RD in the seventies with that twin-piston calliper when it was pretty much the only bike that would do them. Always struck me as a great design. Must have been a cost-saving move to avoid paying royalties to Lockheed?

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Re: RD400C brake calliper (twin piston) torque settings
« Reply #7 on: May 11, 2021, 04:46:53 PM »
Always puzzled me why Yamaha moved to a single-piston sliding caliper design after the C as it seemed far from an improvement. I remember doing stoppies on my RD in the seventies with that twin-piston calliper when it was pretty much the only bike that would do them. Always struck me as a great design. Must have been a cost-saving move to avoid paying royalties to Lockheed?
Yes exactly, they couldn’t come to agreement about renewal arrangement.
So wasn’t until 1986 or something when the patent expired and they could use freely.
Rev 'em till they rattle