I have never used a silicone base fluid other than Dot 5 in the race cars. It was never a street fluid and I never really needed the extra temp fluid for street driving. You really have got to kill the brakes with heat before you see boiling. Guys who take cars to track time may see it but you generally will never even see it autocrossing.

Topping off is recomended but for the most the fluid does not drop much with wear anymore. In the past with a single mater cylinder or some of the small sylinders. it was more a factor.

Also it is important when you have a leaking wheel cylinder. While it may have a slow leak in a drum brake cylinder you do not have to rebuild it till you do brakes, topping off will buy you time till the shoes need replaced if it is a slow leak. Disc brakes it is not as much an issue.

Not sure what you want in data but here is what one of the leading brake MFGs has to say.

http://www.wilwood.com/TechTip/TechBrakeFluidTip.aspx

Here is a good story on the topic from Corvette Fever Magazine.

http://www.azcompvettes.org/uploads/...Fluid_Tech.pdf

Note there are still odd systems out there like Jaguar that use Mineral oil system that is not the regular fluid. They were used years ago and have special needs. I am sure there are others but most that I have seen were British cars.

 

Really, the level doesn't drop much? Then how can the calipers "self adjust"? When my pads are close to worn out (almost to the bottom of the groove), my reservoir is almost to the "low" mark. After I compress the piston to replace the pads, the fluid level goes back to "full".

Ever wonder why there is a full and low mark?

The only time anyone should "top off" the brake fluid is to avoid imminent death from a leak that should be repaired before you can say "WTF", otherwise you just don't know how much pad you got left, unless you actually look at the pads every 1000 miles or so. If you "top off", so that the reservoir is always "full", there will be a major fluid spill if you get around to new pads before the crash caused by metal to metal disc brakes. I do not change the fluid every time I change pads, maybe that's my problem with "topping off". Back in the day, we always bled & changed the brake fluid after the friction was replaced, so that argument may be moot.

95% of people don't even know that that "scraping" noise is the brakes are going bad, just look around at stop lights for all the torn up rotors on soccer mom's SUV. Sure, she takes it to ZippoLube to have the oil changed and the fluids "topped off". But, just because the brake fluid is full, that does not mean you have friction!

That's the sort of data I meant.

I know that you have never professionally advised anyone to drive around with a leaking brake hydraulic system! I would never admit to that!

 

"I have never used a silicone base fluid other than Dot 5 in the race cars. It was never a street fluid and I never really needed the extra temp fluid for street driving"

Maybe not for autos, but Harleys had been using Dot 5 for at least a couple decades.

But stopped in about 2006 as the bikes got ABS brake systems..

 

Yeah but even HDs have a frequent fluid flush schedule..I did mine earlier this year and it wasnt pretty...

 

I hrear ya Woody, I do my Dot 5 bikes every 5 yrs.. No problems..

Even my old Servi-Car I converted to Dot 5..

 

Only ever converted one street car but didnt have it long enough to veriy the long term results..all my race cars used it and never a problem.

 

Depends on what you consider drop much. If it is not below the the low mark to me is not much and no need to top off. Just like oil if it is not a quart low I don't panic and top it off. As long as they system has some fluid in master cylinder and the system has no air it should function fine and not have to be at the top.

With most new disc brake systems today few leak fluid like the wheel cylinders did. In the old cars it was not uncommon for a 4 wheel drum system to need to be topped off several times before the shoes needed replaced. That to me is dropping much.

So there is no need to get so indignante. what some consider much to you may not be much to others.

I seldom add anything anymore since all my cars are now 4 wheel disc.

 

Ahem... on page 5-34 of the 2008 HHR Owner Manual. "It is not a good idea to top off the brake fluid." It then goes on to say what I said earlier.

No indignance was experienced by me, nor did I intend anything other than discussing a popular misconception. You should not top off the brake fluid, because the full and low marks on the reservoir are an indicator of disc pad wear.

My "request for data" was an attempt to soften any statements that could be construed as argumentative. I guess that I can be just too oblique at times. I was trying to discuss, not argue and trying to make that clear with funny words.

It was different in the "binder" days since shoe wear did not show up as prominently, and the reservoir was cast iron. (ever notice that only cars with disc brakes have a visible level mark on a see thru reservoir?). I was there for the "good old days" of 4 wheel drums, I understand that people cling to what "Dad used to say", but things have changed since 1972, when only Caddys had front disc brakes. A new day has dawned, ALL cars have, at least front disc brakes. We must change with the times!:r udy:


I apologize if anyone thought that any personal or mean things got conveyed, I was just trying to "discuss".

 

"I was there for the "good old days" of 4 wheel drums, I understand that people cling to what "Dad used to say", but things have changed since 1972, when only Caddys had front disc brakes".

Me too, my 1953 Chevy had all drum brakes & master cylinder under the floor board trap door.

But my 1972 Chevy Vega had disc brakes up front..

Just sayin..

 

The reason for all disc cars today having see through Master Cylinders is because they don't make front drum brake cars anymore out side the third world. We had disc and 4 wheel disc for years with cast master Cylinders. In the 70's GM and other started to change to Aluminum and plastic to remove weight more than any thing else. Since it was plastic they could put the window in.

There is no harm in topping off but the key is not to let it go dry. It is a reservoir and as long as there is fluid in it to talk up the piston travel the pedal will remain the same. Most reservoirs are designed to not fall below the low mark even if the pads are totally worn out.

So if you want to top off that is fine but if you don't and have no leaks you will not lose your brakes either.