# Squealing Di2 rear brake



## golfnbike13 (Jun 27, 2019)

Brake caliper is BR-R8070 on a new 2020 Specialized Roubaix. 

No matter how frequently cleaned this rear brake continues to squeal. After cleaning with clean rag and rubbing alcohol it’s quite for the first 5-10 miles but squeal always come back. The bottom bolt of the caliper also looks very rusted (bike is only 2 months old and kept in prestige condition). Pointed all this out the the dealer and they assumed a leak in the caliper is rusting the bolt and contaminating the rotor or pads so they replaced the caliper, pads, and rotor under warranty. 
However after a couple weeks the same issue is back, both the squeal and rusted bolt. I’m at a loss, and so is dealer. Anyone have similar issue with this brake set?

Here is a photo of the rusted bolt that is just a few weeks old. 










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## Finx (Oct 19, 2017)

Just FYI, Di2 has nothing to do with brakes. Di2 is just the shifting components.

Shimano brakes use mineral oil. Mineral oil leaking onto the pads would surely cause squeaking, but I it would not cause that rusted bolt. That has to be water in some form (which should certainly not be leaking out of your brakes).


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## tlg (May 11, 2011)

#1 it's not a Di2 brake. It's an Ultegra brake. There is no "Di2" brake. The same brake is used on electronic and mechanical systems.

#2 There is no way possible that a leaking caliper would rust a bolt. Hydraulic fluid is oil. Oil prevents rust, it doesn't cause it.

#4 I'm really really really really baffled how one bolt is rusting and the other isn't. Especially in that short of time. And even more baffled how it can rust that severe in two months.

I'd replace them with stainless bolts and be done with it.

#5 My guess as to why the squeal keeps coming back.... somebody keeps touching the rotors and/or the pads with greasy/oily fingers. Brake pads are porous and will absorb grease/oil. Once contaminated no amount of cleaning will fix them. You only clean the surface. Then when they heat up again, the oil migrates back out and causes squeal.


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## jetdog9 (Jul 12, 2007)

What about #3? 😁

The one rusty bolt is really weird for sure.


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## tlg (May 11, 2011)

jetdog9 said:


> What about #3? 😁.


lol... You don't want to know about #3


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## Marc (Jan 23, 2005)

jetdog9 said:


> What about #3? 
> 
> The one rusty bolt is really weird for sure.


...And 3 is the number thou shalt count, and the number of thine counting shall be 3. 4 thou shalt not count, neither count thou two, except in proceeding to 3....


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## golfnbike13 (Jun 27, 2019)

Bike hasn’t been in rain. Only been washed a few times with small amount of water, but dried well and none in frame. 

Shimano told dealer to run a test by placing paper towels between pads and strap down brake handle for a few hours. Any leaks in caliper would show on towel. So that’s happening right now. 

You can say Shimano mineral oil should not rust a bolt but it’s happened twice now over a span of less then 2 months. Nobody can figure out what else would cause that. 

I’m in TN so no salty air, but it’s hot and humid here. 


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## tlg (May 11, 2011)

golfnbike13 said:


> You can say Shimano mineral oil should not rust a bolt but it’s happened twice now over a span of less then 2 months.


I'm not saying mineral oil 'should' not rust a bolt. Mineral oil WILL NOT rust a bolt. It's impossible. Mineral oil has been used as a rust preventer on tools and instruments for decades. Whatever is rusting your bolt, it's not the mineral oil.


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## golfnbike13 (Jun 27, 2019)

Direct from Shimano “we’ve never seen that but any type of chemical reaction could be possible. We will send you new bolts.”


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