Subaru Forester rear brakes

[JTK]

Originally Posted by painfx
Originally Posted by Donald
With respect to putting some of the Permatex purple on the metal to metal contact areas including the piston surfacr, the Permatex purple is not for rubber and if you put some on the piston surface that hits the pad you are likely to get some on piston boot.


I see that Eric O. From South Main Auto does that. I have also been thinking if it is a good idea to lube the piston to prevent rust?


I've even seen some Eric O videos where he slathers the purple stuff on the caliper pins as well, which I suppose would swell pin bushings and boots. People write in questioning him on this and he says he's never had a return or saw a problem from this. Then again, on some other brake jobs videos I've watched from him, he plucked the pins out and shoved them right back in w/out cleaning/re-lubing them with anything.

This is why I hate the thought of paying ~$400 for a shop to do a pair of pads and rotors. You never know how thorough of a job they're going to do.

 

[Donald]

Originally Posted by JTK
Originally Posted by painfx
Originally Posted by Donald
With respect to putting some of the Permatex purple on the metal to metal contact areas including the piston surfacr, the Permatex purple is not for rubber and if you put some on the piston surface that hits the pad you are likely to get some on piston boot.


I see that Eric O. From South Main Auto does that. I have also been thinking if it is a good idea to lube the piston to prevent rust?


I've even seen some Eric O videos where he slathers the purple stuff on the caliper pins as well, which I suppose would swell pin bushings and boots. People write in questioning him on this and he says he's never had a return or saw a problem from this. Then again, on some other brake jobs videos I've watched from him, he plucked the pins out and shoved them right back in w/out cleaning/re-lubing them with anything.

This is why I hate the thought of paying ~$400 for a shop to do a pair of pads and rotors. You never know how thorough of a job they're going to do.


I am not sure the pin lube would ever wear out. If there is lube and not dirty(as in sand or dirt) it will probably be fine. If the boots are intact(no cracks or rot) and not pulled off at the ends then I guess it would be fine.

However

I wipe off the pins, inspect pins and boots and lube with Sil-glyde.

 

[Luftmasse]

Question... By lubing the caliper piston to prevent rust, but what happens if the lube gets thru the seal and enters the hydraulic system?

So if you don't lube the caliper piston it will rust. But if you lube it, grease will enter the hydraulic system.

To lube or not lube...?

 

[HangFire]

Originally Posted by painfx
Question... By lubing the caliper piston to prevent rust, but what happens if the lube gets thru the seal and enters the hydraulic system?

So if you don't lube the caliper piston it will rust. But if you lube it, grease will enter the hydraulic system.

To lube or not lube...?


The seal we are talking about is not what keeps the hydraulic fluid in. This seal is external, an accordion-like affair held in place by a circular spring, that is just there to get dust and water off the junction of the outside of the piston where it goes in the caliper bore. Any grease on the outside of the piston should not get past the piston/caliper bore interface. If it does, the caliper has already failed.

Grease on the face of the piston is only there to keep the pad mobile and sliding freely against it.

Not all pistons rust. Some are good quality Stainless Steel and well protected by the seal. Some are Phenolic Resin Composite, and thus cannot rust.

 

[Luftmasse]

Originally Posted by HangFire
Originally Posted by painfx
Question... By lubing the caliper piston to prevent rust, but what happens if the lube gets thru the seal and enters the hydraulic system?

So if you don't lube the caliper piston it will rust. But if you lube it, grease will enter the hydraulic system.

To lube or not lube...?


The seal we are talking about is not what keeps the hydraulic fluid in. This seal is external, an accordion-like affair held in place by a circular spring, that is just there to get dust and water off the junction of the outside of the piston where it goes in the caliper bore. Any grease on the outside of the piston should not get past the piston/caliper bore interface. If it does, the caliper has already failed.

Grease on the face of the piston is only there to keep the pad mobile and sliding freely against it.

Not all pistons rust. Some are good quality Stainless Steel and well protected by the seal. Some are Phenolic Resin Composite, and thus cannot rust.


How do you know that by applying grease, it cannot get passed through the seal and get into the system?

You haven't seen caliper piston get rusted?

 

[Donald]

I put some grease on the other side of the caliper and then used my finger to just put a tiny bit on the piston. Kind of like lubing the gasket of oil filter.

 

[Donald]

My local indy mechanic says they use never-seize on the caliper under the clip and then a tiny dab of lubricant on the pad ear.

So up in the air as to lube on pad ear. Helps lube but attract dirt.

He also said they like the Akebono pads I bring in when they have done brakes for me as always perfectly machined.