Cowboy01

Lots of people talk about replacing their brake fluid with some type of DOT 4 fluid, but the manual for my car (2008) says use only DOT 3. Does anyone know the scoop on these fluids.

parchisi

I don't THINK it will hurt anything to put in DOT 4 fluid, it just boils at a higher temperature.

shanec

I think that's it. If you upgrade your pads without going to drilled and/or slotted rotors you can boil your DOT3 brake fluid if you were to slam on the brakes for high speed. Its the drilled holes and slots that help with heat dissipation. Having bigger rotors helps as well. I'm not sure that even with those upgrades that you'd be guaranteed never to boil your fluid. Probably something that auto-x'ers would be more concerned with than me.

(Bigger rotors don't stop faster. Only the pads make the car stop faster)

I'm all up for upgrading my pads and putting in DOT4 - EXCEPT...the brake fluid is also used by the hydraulic clutch in our cars. Bleeding brakes is pretty easy but there is no way to bleed the clutch.

They say the clutch is self bleeding. In reality there is no way to drain the fluid out of there and put new stuff in.

I think anybody that tries putting DOT4 in their car ends up with a mixture of DOT3 and DOT4. I'm not sure what all the ramifications of that are.

...which is why I'm not going to do it.

But I am game for a marginal brake upgrade at some point. Just some kind of somewhat-better-than-stock Hawk pads. Not the super duper stuff though.

Sleeper_08

Those who track their cars regularly and hard normally use DOT 4 fluid. Motul and ATE seem to be the most common. The higher boiling poinyt of the DdOT 4 reduces the chances of boiling the fluid and getting brake fade.

If you run DOT 4 then it should be flushed at least once a year as it absorbs moisture more quickly than DOT 3 fluid.

Argonaut

Dot 3 and 4 are compatible, you can use either one. For the most part Dot 4 is more expensive and unless you need it for its higher boiling temps there is little point in using it. If you are doing performance driving, especially Tack Days, its a no brainer and practically mandatory. If you are street only there is no point. As mentioned above, for the garage mechanic it is practically impossible to get all of the old fluid out during replacement due to the clutch and ABS. Thats ok however - you want the DOT 4 down near the caliper, where the majority of heat is and a normal bleeding takes care of that. Besides, us track guys bleed our brakes so regularly that any remanents of DOT 3 are long since gone.

One of the posts above implies that upgrading pads also requires drilled/slotted rotors when sticking with Dot 3 fluid. I disagree, it really comes down to how you use the car. There are lots of guys using pads like Hawk HPS and HP+, solid rotors and Dot 3 fluid without issue. Also - there are many, many factors that go into determining stopping distances but by far the most important one is where the rubber meets the road - thats right, its your tires. Stickier tires stop in shorter distances. Any caliper, rotor, pad combo that is capable of inducing ABS will stop the car in nearly identical distances. Repeating that stop over and over again in a short time frame however is a different story and thats why we go to Dot 4 fluid, brake cooling systems, track pads that produce their best Cf at high temps, better rotors (sometimes bigger), better calipers and SS lines.

Cowboy01

Thanks for the replies.

irishpwr46

please ignore everything this guy said. he is WRONG.

ill make this simple
upgraded fluid is needed when you are on the brakes so much that the fluid gets too hot to work. you are not going to boil your fluid on the street unless you drive like a bat out of hell constantly

drilled and slotted rotors are not necessary when upgrading pads. the are more of a show piece than anything when it comes to racing. you look at the real road racers, and 90% will have solid rotors seeing as they are less likely to warp than the drilled/ slotted rotors. you arent getting real racing rotors unless your paying $500+ per rotor

and bigger rotors not stopping faster has to be one of the stupidest things i have ever heard. why do you think they are called BIG brake kits? do you think they come with bigger pads? so you mean to tell me that a honda civic with some high temp track pads on 10 inch rotors and stock calipers is going to stop faster than a super snake with 14 inch rotors, 6 piston calipers and stock pads?

if you dont know what you are talking about, just keep quiet. it is better to remain silent and be thought a fool than to open your mouth and remove all doubt.

ShaneM

As long as we are talkign brake fluid, how much do you need when you swap to DOT4? I think i migh tdo soem brake work this month. SS lines, motul, and HPS pads unless someone has a better recomendation on pads. I need something that will latst for the street and work well with stock rotors. I plan on doing a track day later this month. It;s a driving school actually at texas motor speedway. If the track do goes like my first autocross, it will be a regualr deal for me.

Argonaut

Where do some of you guys get your information from. You are over simplifying this. While an increase in rotor size, resulting in higher braking torque can slightly reduce stopping distances on some cars*, to make a blanket statment like this is incorrect. There are many more factors than rotor diameter, and even # of pistons, in play. The biggest factor in stopping distance is the friction between the tire and surface. The weight of the car is also a huge factor. The proper rotor size is the smallest one that gets the job done and no more. On the race track the primary reason we use bigger rotors has to do with their ability to absorb and handle more heat, not anything to do with stopping distances. Perhaps you didn't know that Sprint Cup cars have 15" diameter wheels and weigh in the 3500 lb range..you ain't going to get any BBK under those rims and yet they seem to stop just fine...i.e. its not the rotor size.

* Don't believe me - Zeckhausen is one of the top brake suppliers in the country for high performance and racing cars. Here is a link to some testing they did with Stop Tech (Brake Test). Look at the bottom of the page, at the chart that shows stopping distances. The difference in stopping distance between the baseline single piston caliper with 11.6 in rotor and the StopTech BBK with its 14in rotor (and better tires to boot) from 100MPH is a stunning...7 feet over a 300+ ft distance..wow! If I bought that BBK because I thought it would stop better/shorter I'd be pretty disappointed.

Argonaut

Get 2 liters to have a safety margin. Personally I wouldn't use HPS in a 3600lb car on a track. But it depends a lot on how hard you push it, what tires you have and how hard the track is on brakes (how many stops from triple digit speeds per lap and how much cooling time inbetween). With street tires, if you don't push too hard and keep an eye on them you will probably be fine. The safer thing IMO would be to get HT-10 for the front and HP+ for the rear. You can drive them on the street but they are noisy and dusty so many guys just swap them the day before.

Edit: Another pad to look into is the Carbotech. The XP8 front and XP8 or AX6 rear would be a sweet setup for a novice track pad that can still be street driven. I really like Carbotech pads - they are a bit fussy to bed in but they reward you with good pedal feel, nice bite, no fade. I've used XP10/XP8 on the street and had no issues with them other than the dust. They are reasonably quiet (Hawk track pads are noisy) and the dust cleans up well (unlike some other pads)