GULAMAN

I've seen a couple of the threads regarding brake fluid boil. Sounds like some folks have gone out to HPDE and did OK on the stock fluid (&pads). I'm taking my car on its first track day at Sears Point on the 29th (NASA), and wanted to ask if anyone's done this track before in their RX8.
I don't plan on pushing it too hard this time around, want to get used to the car. And in my one past event @ Sears, I don't recall it being particularly hard on the brakes in my previous car(which had aftermarket DOT4 and pads)

I def. plan on upgrading to DOT 4 and getting better pads for *future* track events....but will I be OK on pure stock for just the one event? (car will have ~4000 miles on it at that time, FWIW).

Gulaman

BlueRenesis82

How comfortable are you rolling the dice on a 30k sports car for $30 worth of brake fluid?

willhave8

I can only tell you my experience and it was not on Sears Point. I did 2 days at Virginia International last year and my OEM fluid was cooked by the middle of the second day. Since moving to DOT 4 fluid, my brakes are as strong after as they are before.

Many of made it through on the OEM fluid with no problems, the track and how hard you drive are the real determinant but IMHO, I would bleed them and replace with a DOT 4 fluid - it doesn't have to be fancy. FORD DOT 4 fluid, Castrol LMA DOT 4 are fine. There are others that 'kick it up a knotch' like ATE Super Blue etc.

It is a pretty easy job for a DIY with a buddy or is not that costly to have a garage do. Worth doing.

TeamRX8

iTrader: (25)

lol, kicking it up a notch is doing an Emeril "BAM!" with Castrol SRF

willhave8

Okay, you got me. I guess I was thinking from a cost standpoint and narrowly...

TeamRX8

iTrader: (25)

just joking as usual ...

Paul_in_DC

Similar experience here. I had OEM fluid last fall at Shenandoah Circuit and got serious brake fade as they heated up (but Shenandoah Circuit is hard on brakes). At VIR a couple weeks ago, I had DOT-4 fluid and the OEM brakes worked like a champ.

ZoomZoomH

iTrader: (1)

so i guess the consensus is to change to DOT4 brake fluid just to be safe... which i concur as well... stock pads should be fine for one event

DRIVINSIDEWAYS

How do you change the fluid? Is there a write-up somewhere?

Paul_in_DC

See https://www.rx8club.com/showthread.p...ht=brake+fluid

Punksux

sorry for the newbie question, but is it ok to use a dot 4 brake fluid for the streets, or is it the same thing as brake pads. Where they work at some optimum temperature.

tomfree

Brake fluid does not have to get up to a "working temperature" Dot4 is fine for the street.

Check this out for a primer on how brakes work as a whole:
http://auto.howstuffworks.com/brake.htm

Punksux

thanks....... I was reading up a little and found that dot 3 & 4 are much different than dot 5 due to water absorption. But wasnt sure about the difference of 3 and 4, except for boiling temps.

Winning 8

I will do the brake line, dot 4 fluid and better brake pad for any track event. At sears point there is two long straight one is from turn six to seven and one is from ten to eleven. Both of them is from fourth gear into second.
I run sears point before, and it is a very difficult track, tell you the truth I will rather get more brakes then more power running at sears.
If you need help changing fluide just pm me or something.

yiksing

So DOT4 doesn't absorb moisture like DOT5?

Paul_in_DC

DOT 5 is silicon-based, and has problems with compressibility. The rest are glycol-based, and aren't compressible. The differences are in the ability to resist high temperatures before the fluid starts to boil. DOT 4 can withstand higher temperatures than DOT 3.

I found a good overview and FAQ about brake fluids at Quadriga Motorsports. Start with Brake Fluid Explained then see the other links of the left edge of the page.

GULAMAN

Thanks. I will probably go ahead and change the fluid, I actually do have some unused ATE fluid already, purchased for my previous car, so I don't really have much of an excuse not to do it! When I posted this originally I was thinking that this first time in the RX8 would be a good time to 'use up' the OEM fluid, then get fresh new DOT4 in there in time for its 2nd event, where I will likely be pushing the car harder.

At Sears, I found T11 to be the severest braking area, even more than T7 (which is a bit uphill). But half the time, even the severity of T11 was reduced, because I ended up right behind 2-3 cars out of T10 that I didn't have enough HP to pass before T11; so, the braking zone was inevitably 'stretched'.

What I'm most anxious about is keeping the car stable in the Esses!! it's so tempting to go fast on those, but they can bite back. even in my AWD Audi, I got squirrely a couple of times. How did the RX8 feel on the esses for you?

Speedtoys

It Depend(s)

I was at Sears this last weekend in my bone stock 04 base model 6spd, on OEM tires (25k miles old) oem brake fluid..and was running 1:57-58s and not having any fluid issues.

Although, experience WRT braking is important I suppose too.

GULAMAN

Hey are you talking about this weekend Oct 7? I was there on Saturday. I'm very happy about the OEM brakes on this car, and yes I do have DOT4 now. no fade at all. BTW, 1:57 is damn good for a bone stock car! you must be up in Grp 4 or TT level, huh??

Speedtoys

Ok..a few things.

The OEM braking system is OK. I didnt go for another few seconds a lap, because the OEM pads will barf on me in 4 and 11 in about 1.5 laps if I want them to.

Ive been helping instruct Gp4 with Butterfield for a while, but the last couple years racing in Pro7.

I would stay FAR AWAY from just saying "DOT4" is better, there are many manufacturers for DOT4 fluid, the stamp on the bottle can cause you a LOT of pain.

Valvoline DOT4 fluid aint the same as Motul RBF600 DOT4 fluid....many have found tire barriers who thought that it was all the same.

Also, DOT5 is a good fluid for LONG service times, and for that alone. Its not hygroscopic whatsoever, and therefore can live in hydraulic systems for years without degrading or losing its boiling point as its always dry.


1:57 is only 3s a lap faster than say..an well driven 1983ish RX7 on no motor mods, 185 tires (albeit race) and setup very very loose in the rear end can do around Sears. I was turning 2:01 at the end of 2005, this year its been bad motor, then bad carbs, then separated subframe, then this..that..the other. 7yrs of racing in that chassis and its literally coming apart. Im waiting for the rear glass to explode in a hard fast turn someday, like T10 at Thunderhill.

Speedtoys

The S's felt great, after settling in for the turnin to 8, I could maintain WOT thru 8a, catching fuel cut heading downhill towards 9..but holding it thru 10, no sense in shifting to 4th, cuz you have no time to settle the car AND downshift to 3rd to exit 10 hard.

The S's are all about the entry, there is no alternate entry to 8, which is 100% dependant on the exit of 7.

Choking the exit of 7 will put you into the wall in 10 if youre not willing to pull out of it and slow WAY down to readjust.

Of course, being able to put 2 off into the dust over 8a because you -know- where it's at is pretty important as well.

Paul_in_DC

DOT 5 fluid is silicon-based versus glycol-based. While it has a higher boiling point than DOT 3 or 4, it's already more compressible, so it's no use for performance driving.

John V

iTrader: (1)

Just to be clear, the factory fill Mazda fluid *IS* DOT4 already. I always recommend a fluid flush prior to track days with a quality fluid.

willhave8

Eh? didn't know that but I can tell that it is easily cooked by a newbie and VIR Grand East.

ATE Superblue takes a licking and keeps on ticking though.

BlueRenesis82

i had no idea