Brake Fluid Question
 

How come Brake Fluid in new cars and trucks have to be changed nowadays and when I bought new cars and trucks in the 60's 70's 80's 90's. i don't remember that being necessary. Does all the brake fluid today need to be changed out including in the race cars?

Thank You Kenney Kelley

Re: Brake Fluid Question
 

Brake fluid always had to be, should have been changed and it’s the root cause of “frozen” calipers.

That said changing race car brake fluid is even more important especially if you don’t use DOT5 silicone which is the only fluid that does not overheat and burn and the only fluid I use in my race cars which I change every season. DOT3, 4 and 4.5 pour clear and drain looking like black sludge from excessive heat.

Re: Brake Fluid Question
 

Brake fluid change has been recommended for years by manufacturers . When I started as a technician 50 plus years ago ,we used to flush the systems with denatured alcohol.
Brake fluid is hydroscopic ,it absorbs moisture from the atmosphere and becomes both a rust agent and corrosive to the system .constant heat also degrades it ,becoming black and sludgy
With the advent of antilock brake systems regular servicing of the fluid became more critical as the antilock system employs several close tolerance high speed actuator valves that are easily damaged by contaminated fluid .
As it applies to our race cars ,brake fluid should be flushed and replaced every season , preferably at the end of the season before storage .
DOT 3 or 4regular fluid is fine for a street car ,but race cars that experience extremely high temperatures should be using race specific fluids that have a much higher wet boiling point such as Wilwood Hi Temp 570 or EXP 600. Castrol ,VP ,Motul and others all make high performance fluids with higher wet boiling points.
The higher boiling point fluids do not sludge up nearly as much as street fluids.

Re: Brake Fluid Question
 

Tom, I have tried Wilwood’s Hi Temp 570 and it too overheated, burnt and was black sludge, just as bad as DOT3, 4 and 4.5. Again the only fluid that I have used that doesn’t burn, overheat, cook, turn black is DOT5

Re: Brake Fluid Question
 

probably because we dont use the chutes .
The silicone fluid has it's pluses for sure ,but silicone has 3 times more compression than regular fluid .
Not something that a foot brake racer might feel comfortable with.
The 570 and 600 works pretty well on Stock Super Stock type cars . ...The Motul fluid in my opinion is even better than the Wilwood fluid .
I used to do SCCA inspections and maintenance on several road race Corvettes .Fluid flush and change is required before EVERY event....All fluids brands show some degradation .
The Motul fluid really was superior to most of the others ,only Wilwood 600 was as good . We're talking cars that get the brakes so hot that the caliper piston boots melt or burn up and the rotors dont last more than 2 races!

Re: Brake Fluid Question
 

Because brake systems years ago consisted of $5 shoes and $3 wheel cylinders that had tolerances measured in .100. Now we have ABS controllers and a variety of materials in brake systems with much closer tolerances. We used to hone and rebuild wheel cylinders with no measurements. Even back them brake hydraulic system failures were usually related to rusting of the cast iron due to brake fluid contamination but parts and fluids were cheap and we junked cars at 100k mi.

Re: Brake Fluid Question
 

Have you tried Castrol SRF? Its wet boiling point (which is more applicable to how most people care for their brake fluid) is higher than all the other high temp offerings out there. I have used it with great success in road racing compared to Motul 660 which is a nice fluid in itself, but if you aren't flushing it very often it has issues like all the rest. I value wet boiling point much more than the dry points they all advertise, since unlike the road racing stuff, I do not plan on flushing the fluid weekly

Re: Brake Fluid Question
 

I have not, but I do flush my system before the start of every season and I swap out the calipers every other season, sending them back to Mark Williams for rebuilding.

Re: Brake Fluid Question
 

I've been using DOT 4 brake fluid as per the manufacturer & gets changed out during the off season. This year I will be using DOT 5.1

Re: Brake Fluid Question
 

Pegasus Auto Racing has a great comparison chart of racing brake fluids:

https://www.pegasusautoracing.com/gr...pID=BRAKEFLUID