because the show car crowd needs a brake fluid that is good for 500+ degrees.

DOT5 works better because it doesn't boil when braking in our race cars like DOT3, 4 or 5.1 does.

I see there is more than Brake fluids starting to boil on this thread?

Looked in my trailer and seems I have a big ole bottle of prestone dot 3 I have been using for the trailer brakes and race cars...pedal and stopping abilities are good on all.

Most of the tracks we run on are/were 1/4 mile tracks in the past and stopping room is plentiful.

Copied from Mark Williams website...….

Brake Lines and Fluid

Aircraft AN-3 brake lines and fittings are recommended. Only stainless steel braided teflon hose, stainless or seamless steel tubing (3/16” x .028”) should be used for brake lines. MW has available swaged Teflon Stainless flexible braided line that can be fabricated on a same day basis. The are available online (P/N 0300-X-X). Lines should be secured to chassis rails to resist vibration and routed in such a way to avoid possible contact with wheels, tires and other moving parts. Joining hard line and braided line or “T”s should be done using a bulkhead fitting and a small tab welded to the chassis. Long runs should be done with hard tubing to avoid expansion of flexible line. The amount of flexible braided hose in the system should be kept to a minimum. See page 64 or the online store for AN -3 fittings and brake line. Use of DOT 4 or 5.1 fluid with a high boiling point and lubrication for seals and pistons is recommended. Do not use (DOT 5) silicone fluids .

Boiling point chart link

https://th.bing.com/th/id/OIP....o=5&dpr=1.25&pid=1.7

I boiled the fluid once at the end of a race I was fortunate enough to win.....

Dot 3 std fluid....

After semi's pedal went to floor.....

By the time we ran the final, pedal was ok....

Been using Motul Dot 4 and it has higher boiling point....No issues...

DOT4 and 5.1 will boil too. Even if it doesn't boil, it's cooking. Flush your brake system at the end of a season and I know what comes out looks and smells nothing like what went in out of the bottle except DOT5

As has been said, use whatever floats your boat.

FWIW, I always went with what MW recommended in my MW brakes. Never had a problem.

FWIW, I always go with what my professional race car chassis builders recommend and If you had made the switch to DOT5, you would have felt a difference in the pedal and seen a difference when you flushed the system which most bracket racers never do.

FWIW2, I've read on line that DOT5 is also used in military vehicles.

Ed - maybe they suggested you use Dot 5 because "your car sits for long periods of time"



Are DOT 3 and DOT 4 brake fluid compatible?
Yes, DOT 3 brake fluid is compatible with DOT 4 brake fluid. However, DOT 4 offers a higher boiling point.

DOT 5.1 is used in high-performance and heavy-duty applications due to its high boiling point. It’s compatible with DOT 3 and DOT 4 fluid.

DOT 5 brake fluid is silicone, meaning it doesn’t absorb water. It’s not compatible with the other brake fluids and is used mostly in classic cars that remain in storage for long periods and need a brake fluid that doesn’t absorb water.

I did a lot of research with our 2018 cars and tried to improve of the brakes. I settled on the Motul 5.1 after recommendation from my son who is into road racing and sports cars.

We race at Huntsville which is pretty short, double lots of runs and don't see pedal fade now.

PROPERTIES
100% synthetic fluid, polyglycol bases.
Color Yellow
Dry boiling point 269 °C / 516 °F
Wet boiling point 187 °C / 369 °F

Here is the complete spec sheet - https://d23zpyj32c5wn3.cloudfr...GB_29.pdf?1492016150

Scott, dry is meaningless, wet is the barometer.

That said, you'll never know until you try DOT5 then you see and feel the difference. What you see after a seasonal flushing alone is enough to convince most.

Correct

quote:

Originally posted by DragRaceResults:

DOT 5 brake fluid is silicone, meaning it doesn’t absorb water. It’s not compatible with the other brake fluids and is used mostly in classic cars that remain in storage for long periods and need a brake fluid that doesn’t absorb water.

Scott, this was written in the mid 70s, I know, I read it then.

As I said, you flush your brake system just once after a full season of racing and the smelly black liquid that comes out should be enough to convince anyone that the DOT3, 4, 5.1 brake fluid they are using isn't up to the task.

The performance parameters of each fluid is what it is and each individual can make his own decision. Getting back to the OP's original question, you're dealing with chemistry, and bottom line, the rubber components you currently have and it's compatibility with 5.0 fluid.

the rubber components aka o rings in ALL drag race brake systems are compatible with DOT5

Gang, If your ride is developing excessive heat when braking at the end of a dragstrip and you run under 230 mph you probably have insufficient(low) line pressure and or caliper flex or caliper mounting issues...The low line pressure at the caliper is the result of wrong pedal ratio or wrong master cyl bore size,usually both (providing you have no air in the system)..The caliper flex issue is a design problem of the caliper with weak bridging or a weak mounting bracket..so if your car stops great with long pad and rotor life on a quality
Dot 3/4 your not overheating or overtaxing the fluid and it wont be blackened ..If you need a 260 degree boiling point fluid you might want to check the mechanics of the system..The Ford Truck Rotunda H.D. Fluid is an excellent O.E.M Fluid..

We all have a lot of free time on our hands now, so I present this challenge to everyone here... flush your brake system today, tomorrow, this weekend, it's something you should be doing every season anyway and I'll bet that what comes out doesn't look like or smell like what's in the bottle.

I have only used DOT4 in my car, fluid stays clear, never any fade even at GALOT running 190+ with no chutes. The MW rotors are the originals that were put on this car in 09. No signs of cracks, warping or discoloration.

It does have a aggressive pedal ratio, don't have to get on the brakes very hard to slow down quickly.

quote:

Originally posted by 1320racer:
because the show car crowd needs a brake fluid that is good for 500+ degrees.

DOT5 works better because it doesn't boil when braking in our race cars like DOT3, 4 or 5.1 does.

Every UNDERCOVER made was a show car lol...

that I agree with

Kurt showed every chassis shop how to build a dragster and they all attempted to copy him.

Heck I’ve been using wilwood hi temp fluid for a while now, with good results. I have run every dot at some point I think, I do remember the silicone fluid not having a good pedal feel
https://www.summitracing.com/p...qEAQYASABEgL74fD_BwE