Rear brakes out - Road Star Warrior Forum : Yamaha Star Warrior Forums

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Old 07-10-2019, 07:50 PM   #1 (permalink)
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Default Rear brakes out

Hello all,

Thanks for the help.
So I was riding in the mountains today. About halfway down (was on the rears kinda hard) my rear brake pedal stopped working. I can push it all the way down and it eventually does a little bit of something but not much. Feels mushy and definitely not building pressure. Don’t see any leaks, reservoir looks good. Where to look next? Master cylinder? Take it to shop?
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Old 07-10-2019, 08:19 PM   #2 (permalink)
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Update: went back out and it’s building up pressure just fine.
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Old 07-10-2019, 08:19 PM   #3 (permalink)
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You may have just boiled the fluid and now it's Airbound. Check the fluid level, I'm guessing it's low. Add some more and bleed the brakes and see if that helps.

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Old 07-10-2019, 09:00 PM   #4 (permalink)
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+1
I would just drain out the old brake fluid
And start with fresh fluid rebeed the rear brakes...


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Old 07-10-2019, 09:59 PM   #5 (permalink)
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Sounds like the thing to do. Thanks guys!
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Old 07-11-2019, 01:53 PM   #6 (permalink)
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Quote:
Originally Posted by abbrigg View Post
Hello all,

Thanks for the help.
So I was riding in the mountains today. About halfway down (was on the rears kinda hard) my rear brake pedal stopped working. I can push it all the way down and it eventually does a little bit of something but not much. Feels mushy and definitely not building pressure. Donít see any leaks, reservoir looks good. Where to look next? Master cylinder? Take it to shop?
Quote:
Originally Posted by abbrigg View Post
Update: went back out and itís building up pressure just fine.
Based on the above, the brake fluid compound broke down and reached boiling point temperature.
Perhaps because of age and or contamination or possibly the removal of the rear aluminum finned rotor cover that acts as a heat sink.

I would suggest replacing the Brake Fluid with a premium quality DOT 4 or DOT 5.1 compound that has a higher boiling point.
Both these compounds are glycol-based brake fluids and are compatible with each other.
  • DOT 5 which is silicone-based should never be mixed with glycol-based DOT fluids.
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Old 07-11-2019, 02:46 PM   #7 (permalink)
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If braking hard and often like always down the mountain, using such higher boiling point fluids might be good idea.
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