Merci, G. *NM*

Me: about every 4 years.

On my track 944 Turbo, after every DE weekend. On my street cars (non Porsche) it's every other brake job, probably every 4 years on average but I will likely move to doing this every brake service since it's easy with my Motive bleeder. I haven't touched the brakes on my Boxster yet but I am planning to swap fluid every time I do any brake related service. I cannot recall ever getting a soft pedal on my street cars so it's more a matter of getting rid of any moisture that has been absorbed by the fluid.

Since brake fluid attracts moisture, my concern is the damage that moisture could do to the innards of the brake system.

... so probably twice per month.
Happy Boxstering
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

Flush once per year and bleed before every track event (3-4 per year).

As the clutch became harder to engage smoothly and as shifting became harder to accomplish smoothly and assuming with nearly 280K miles the original clutch and tranny were nearing the end of their life I found out it had been 2.5 years since I last had the brake/clutch fluid flushed and bled.

I had the brake/clutch fluid flush/bleed done and afterwards while I could feel no change in the braking at all the clutch action was much improved and the shifting once again became like a hot knife through butter smooth. Given the transformation of the clutch action I would have to believe braking is being affected in some way if only by exposure to old fluid that is past its change by date.

Based on my experience my advice is to follow Porsche on this and have this service done at least every two years regardless of miles covered.

Oh, normally I try to have this service done every 2 years, but I lost track of time on when I last had this done on the Boxster.



Edited 1 time(s). Last edit at 01/02/2015 01:25PM by MarcW. (view changes)

A complete flush, not just a bleed, is good insurance both for safety but also to avoid corrosion of the brake system.

So for street driven cars, roughly every two years is smart. But understand that most brake fluid formulations are a trade off - typically the higher the boiling point ( racing fluid) the more hygroscopic it is, meaning it must be flushed more often. So for street machines i suggest a fluid like Castrol GT-LMA ( low moisture absorption). Its plenty hgih BP for normal use and absorbs less water. Yes, its DOT-4, borderline 5.1.

For track cars ( true track use, not autocross in which brakes are used for only very brief periods), i flush twice a year and bleed (about 25-50 ml per caliper) after each event. if i see signs of discoloration i bleed more or do a complete flush. Burned/abused brake fluid changes color and has flotsam in it, for want of a better word.

note that Porsche specifies two years regardless of mileage.

Also note that PCA requires a complete flush within one year of any track event (DE).

But track use aside, its cheap insurance to ward off failures or sticking of expensive components. Especially with a pressure bleeder ( about $70) its fairly easy.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

that's taking an un-necessary risk with your brake system, especially in a car that you may wish to keep for twenty or more years.

Two years.

If you stretch it at least move to the most low-water-absorption fluid you can get your hands one - and that is NOT factory fluid (whcih is ate super 200).

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

The more i drive the less i brake and the less i heat my brakes. Brake wear is going down as tire wear goes up.

And it never looks the slightest bit off-color.

On the other hand i have friends who push the heck out of modern cars ( e.g.: 987 Cayman S/R) with stability control (which cannot be turned off without also turning off ABS) that not only cook their brake fluid, but also cook their calipers, and indirectly, the CV grease.

That's hot.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Quote
grant
The more i drive the less i brake and the less i heat my brakes. Brake wear is going down as tire wear goes up.

And it never looks the slightest bit off-color.

On the other hand i have friends who push the heck out of modern cars ( e.g.: 987 Cayman S/R) with stability control (which cannot be turned off without also turning off ABS) that not only cook their brake fluid, but also cook their calipers, and indirectly, the CV grease.

That's hot.

Grant

Interesting that Porsche equipped performance cars with a PSM system that is either on or "off" ( with ABS or the various other sensors lurking the the background if things seem amiss or about to end badly).In theory, I think PSM is great to have on the street but at the track you want to get the car to slide or the rear to rotate a bit to get around the track faster; the PSM can really get in your way, especially on the newer cars.
Our 986 had no PSM so you went around a corner without any nannys; the 987 had SC and I always had it on sport, so intervention was minimal and when it did come on it was very "helpful". The 981 PSM has no in between setting--unless you pay the $2K for the SC package-- so it can come back on in a bumpy braking zone despite having been turned off.
I think a better approach might have been what GM did on the C6/C7 active handling setup with mutiple settings--from full in (wet) to full out (race)--5 settings IIRC--which gives you a lot of options and still provide help if you want it.

... claim to "program it off". Yet none work 100%. Even when you turn it off, it comes back on when certain parameters ( mostly yaw) exceed X. Now, it IS possible to pull the fuse, but then the ABS is also gone, and no one seems to think that's a good trade off.

By the way, the biggest rear brake roaster is - to protect anonymity - mags.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Wasn't it you who said carbon fiber wheels are a bad idea because of poor heat transfer from hot tires?

S that's where the heat is. In fact, you may find that on many new cars, the rear brakes wear faster than the fronts.

Same reason.

That said, yes there are also issues with the CV/axle angle on Cayman S models and also proximity issues with the catalytic converters. They pose many challenges to the truly fast track drivers.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

I was aware of PTV working the rear brakes more, but didn't know PSM (I take it that's what you're alluding to) favored the rear brakes. Also, do you mean the Cayman S axle geometry is different from the base (understandable: different engine mass and other handling vs. ride considerations) or is there also a difference between say, the S Boxster and the S Cayman? Still, what's the issue with "mags?"

Quote
Laz
I was aware of PTV working the rear brakes more, but didn't know PSM (I take it that's what you're alluding to) favored the rear brakes. Also, do you mean the Cayman S axle geometry is different from the base (understandable: different engine mass and other handling vs. ride considerations) or is there also a difference between say, the S Boxster and the S Cayman? Still, what's the issue with "mags?"

PSM operation as per the 2006 Boxster manual. So I believe that PTV is more of an extension of PSM, with the addition of the rear differential lock helping to stabilize the car. specially on irregular surfaces. rather than entirely different system from PSM.

1. PSM is porsche's name for stability control, so yes.
2. yes, the cayman S has a more acute angle where the final drive connects to the drive-shafts due to motor/tranny size differences
3. mags is the nickname of a person, who's identity is being obfuscated but is known to track junkies like Mike. Sorry, thought that was clear for phrasing.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com



Edited 1 time(s). Last edit at 01/03/2015 08:01PM by grant. (view changes)

"Mad Meg"
[upload.wikimedia.org]

I believe the difference in rear axle angles stems from the difference in transmissions.

With the 5 speed in earlier Boxsters, the rear axles come out from the engine at a straighter angle than those on the 6 speed manual which has always been standard on the S.

I don't think there's a rear axle angle difference with newer Boxsters between the base and S as they all have the 6 speed manual.

With the increased angle on 6 speed transmissioned cars, there's more wear on the CV boots, so they have a tendency to wear out faster.

.. and therefore heat. At pre-tech i have seen (where) liquid grease dripped out of Mag's car.

He now uses race grease and it still liquifies

Grant

Grant

gee-lenahan-at-gee-mail-dot-com



Edited 1 time(s). Last edit at 01/03/2015 08:03PM by grant. (view changes)

Not sure if the 981's manual is the same as earlier 6 speeds. It sure feels more definite and smoother than the 5 speed my 06 had.

No idea about the PDK drive shaft angles, but it does share parts with the 7 speed manual in tbe 991. So those two transmissions might have similar angles.

actuation mechanisms and clutches

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

The 981 has a 6 speed manual, while the PDK is a 7 speed.

The 991's manual 7 speed gear box, according to this C&D article, however, shares about 1/3 of it's inner parts with the PDK. Apparently the outer castings are similar, but not interchangeable. There are also good cutaway pictures of the two transmissions showing the common parts.

[www.caranddriver.com]

..east with the factory guys. Yes, there are differences, but the archietcture and main components are the same.

Some differences in actuation (obviously), clutch(obviously), ratios (obviously), lock-out arch (obviously) .... but they are built on the same architecture and major components. this is from the horse's mouth. I have not had them open, but did ask at a local race shop who exchanges them due to penalties in spec racing.

So i'm pretty confident.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com