Shimano brake oil addition

[gongmech]

So just before my weekend ride my Shimano rear brake had no grip whatsoever. I was desperate and had no Shimano mineral oil to bleed into the system, so I grabbed a little shock oil in a syringe and opened the valve cap at the back, pumped a little oil in there until the brake lever felt a little fuller, the opened the reservoir by the lever and added drop by drop of the shock oil and pumped the lever until it felt like i had proper brakes again.

I'm sure this oil is much thicker than the Shimano bleed oil, but it worked. 

Any coments on how this could be detrimental? My brakes worked great and even better after the ride and I rode some hairy stuff.

 

Some thoughts would be great from you bike techy guys.

Thanks

 

[Rudi Pollard]

Shimano brakes typically use mineral oil. Using something else might destroy your seals but I'm not sure what shock oil will do to it. All I know is that dot fluid will destroy a mineral oil system.

[Jewbacca]

I would suggest that any type of consistent oil WILL work, but the long term effects on the seals and pistons is another matter.

 

I would suggest flushing that brake and re-bleeding it.

 

In the future use sunflower cooking oil if you are in a pinch. It is natural and won't damage your internals.

[TNOSE_E]

Fork / shock oil is mineral oil.

 

Should be fine till you have time to flush the system.

 

Have got XT brakes running 5w mineral oil for 3 years now.

[rudi-h]

think i did the same thing last week...

 

I have two containers of oil which I recall were shimano mineral oil and RS fork oil (both are red) and I can't remember which was which...

 

would be nice if anyone can confirm whether RS fork oil is mineral or synthetic...  Doing Transbaviaans in a month and don't want leaking brake pistons before such a long ride.

 

edit:  on the op's question:  Can it be detrimental?

 

Yes it can.  Mineral and synthetic oils have different reactions to seal materials and are generally not compatible, causing hardening or leaking of seals which will cause leaks etc.  the viscosity for this type of application shouldn't be too serious, but the type of the base oil is important.

[David Marshall]

Not going to damage the seals short term.  Both "mineral" and "synthetic" oils are refined from crude oil and should not damage nitrile seals or o'rings.  Hydraulic lock out mechanisms usually call for fork oil and have the same seal compounds as oil filled brakes.  Oil viscosity and heat characteristics may well be a factor in terms of brake performance so could be detrimental over time.

 

I would just flush out with Shimano oil (or Castrol LHM mineral oil if you can't get Shimano) .

[droo]

"Shock oil" is way too broad. Give me a brand and variant and I'll be able to give you some meaningful feedback.