My mate bled his rear avid juicy with Mineral oil(they should be dot 5.1). The bike has been stood for a while and now the brake is very spongy. He is not sure whether the seals have gone or he didn’t bleed it right. ny advice on whether mineral fluid wrecks non mineral seals? Thanks

New seals there I’m afraid… 🙁

Every single seal thoughout the brake will be completely shot. It will need a full strip, clean and rebuild with replacement seals and the correct fluid.

Brake fluid is cheap- I’d open it up, examine the seals, and if it doesn’t look fubbered I’d clean it thoroughly and try it with the correct fluid. What’s the worst that can happen?

(answer: brakes fail, mate rides off cliff)

No, the seals will be knackered and swollen.

Scienceofficer+1, unless you can do the work yourself you may as well write the brake off, never saw a dot seal that survived even a brief contact with mineral fluid.EDIT-leave them too long and they’ll turn to a chewing gum consistency which is virtually impossible to remove.

coatesy – Member

never saw a dot seal that survived even a brief contact with mineral fluid

See, I have- an Elixir that’d been filled with Shimano DOT, and wasn’t emptied out for about 2 months. That brake’s still going strong after a thorough clean and rebuild. It might be the exception o’course.

Put the correct fluid in, put them in the classified with photos of someone elses brakes and describe them as in perfect condition. Then we have all have a laugh when the row breaks out 😉

Thanks for the advice I’ll break the bad news to him….Cheers

Thanks monkey

Northwind – are you sure about that? As far as I know, Shimano has always been Mineral and NEVER Dot…

DOT is a range of standards. Mineral Oil can still conform to certain DOT standards (I think DOT 5 is Mineral).

DOT5 is silicone based.

DickBarton – Member

Northwind – are you sure about that? As far as I know, Shimano has always been Mineral and NEVER Dot…

Right enough, slip of the fingers there- should have said mineral.

seals all changed brakes back working all for a £10 thanks for all your help. I will not be doing that again lol.