S1 Exige Brakes

[PJI]

Just got back from an evening track day at Donnington. Great afternoon apart from one frightening moment when I was approaching Redgate and the breaks went soft. Parked car for ten minutes and they were ok to drive home. In fact they felt pretty good. What's the reason for this does anyone have an idea? The brakes are standard S1. All the pads look ok.

Anyones advice would be appreciated.

[Paul RN]

Heat fade?

[moles]

Fluid has boiled I think and as it cools the feel comes back?.

[S Works]

Yep, how many laps had you done at that point. Donny is hard on brakes.

[bogie]

when was the last time you changed the fluid?

also what pads and discs you running? ...you can upgrade them so they are fade resistant - AP discs and Pagid RS4-2s are a good combo

[PJI]

Thanks for the info.

i had done about 30 odd laps at thart point and it was on the GP circuit which is hard on the brakes.

i have owned the car for three months. Bought it from B&C after they had just done a C service so i'm thinking that they would have changed the fluid then!

I'm running standard pads and discs.

[bogie]

that explains it then ...30 laps of Donny on the std discs n pads !

you probably want to replace them sooner rather than later if you intend to track it a lot

[hbaumhardt]

If the brake pedal went long then you need to change the fluid http://wiki.seloc.org/a/Brake_fluid

If the pedal was OK but the brakes simply didnt work as well you either have pad or disk fade, take a look at the brakes section of http://wiki.seloc.org/a/S2_Track_Modifications

[PJI]

It's booked in for Pagid pads, braided hoses and Castrol srf fluid.

Thanks for your opinions and advice.

[Cuzza]

PJI said:

Castrol srf fluid.

Don't bother with that bit, mega expensive and mega overkill - normal DOT4 Castrol Response will be fine or AP600 if you want something a little more exotic.

[hbaumhardt]

Yes SRF takes on more water than normal fluid over time (it is more hygroscopic) so you may well have to change it even more regulary than annually for a 300 degree DOT4 plus its twice the price. If you aren't racing and budgeting for regular fluid chnages avoid.

[Cuzza]

hbaumhardt said:

Yes SRF takes on more water than normal fluid over time (it is more hygroscopic).

Didn't know that - I did know it's f*cking expensive and not worth it tho

[hbaumhardt]

Therein lies the dilemma, it has a higher wet boilng point than normal but gets wet quicker over time. Fantastic if changing fluid every race but not so good for annual or less frequent changes. I run AP600 equivalent and bleed out the front calipers before every race weekend.

[Paul RN]

PJI said:

Bought it from B&C after they had just done a C service so i'm thinking that they would have changed the fluid then!

Nope. You have to ask, service manual recommends brake fluid should be changed every 12 mths with normal use.

Edited by Paul RN on Tuesday 21st August 20:24

[Pesky]

Cuzza said:

Didn't know that - I did know it's f*cking expensive and not worth it tho

I use SRF, & have done for 6 years. Normally change it every 18 months - as a routine,& certainly not because it's "gone off". Annual mileage of around 10K miles, including 20 trackdays per year, in a lardy Honda'd Exige S1. Personally, I don't take chances with my brakes, so spending £45 on fluid every 18 months is not an issue. Perhaps I am being ripped off, & could save myself £30, but I don't care

Edited by Pesky on Tuesday 21st August 21:19

[Cuzza]

Pesky said:

I use SRF, & have done for 6 years. Normally change it every 18 months - as a routine,& certainly not because it's "gone off". Annual mileage of around 10K miles, including 20 trackdays per year, in a lardy Honda'd Exige S1. Personally, I don't take chances with my brakes, so spending £45 on fluid every 18 months is not an issue. Perhaps I am being ripped off, & could save myself £30, but I don't care

Edited by Pesky on Tuesday 21st August 21:19

Good for you. If you're happy using SRF then fill your boots - it is overkill though and is designed for extreme conditions with carbon brakes and the like and as Hans says, needs changing more often.

I don't take chances with my brakes either - seems a bit daft in a racing car and nor I doubt do the guys I race with or the LoT guys and I don't know anyone who uses SRF (including the Honda crowd).

[Pesky]

Cuzza said:

or the LoT guys and I don't know anyone who uses SRF (including the Honda crowd).

Perhaps your're not looking hard enough then - plenty of the Exige racers/trackdayers do in fact use SRF. Fortunately, I've only got little feet, so my boots don't need much filling

[Pesky]

For anyone who is interested, see the final paragraph in particular:

"Following exhaustive laboratory tests at Castrol's International Technology Centre in the UK, the final formulation for Castrol SRF was subjected to an extensive road-test programme on the Gross Glockner and Stelvio passes high in the Austrian and Italian Alps. It then underwent an independent track test program conducted by a famous Formula One racing team. Their assessment was that "Castrol SRF is the best racing brake fluid we have ever used."

Race Proven - Ultimate Racing Brake Fluid!

All conventional brake fluids used in cars and motor cycles are hygroscopic, that is, they absorb water from their surroundings. Strange though it may seem, the flexible hoses incorporated in braking systems are permeable to water and in time enough, water can find its way into the system via the hoses, and seriously affect the brake fluid's performance. This water reduces the boiling point of the fluid (ie, it lowers the temperature at which gas bubbles begin to form). When these bubbles form, they turn a virtually incompressible liquid into a mixture of gas and liquid which can be compressed quite considerably, thus severely reducing the efficiency of the brakes. In this situation, a driver finds that the brakes feel spongy. Brake-pedal travel will increase and it may be necessary to 'pump' the pedal to get the brakes to function effectively. However, when the brake fluid reaches a temperature at which the water in the fluid causes gas to be produced, which is equal to the volume swept by the piston in the rake master-cylinder, vapor-lock occurs and the brakes become inoperative. When this happens, the first indication the driver has that something is wrong is when he applies the brakes. The pedal goes down to the floor and the car carries on at undiminished - and possibly fatal speed.

The silicon ester technology in Castrol SRF addresses this problem in two ways. Firstly, Castrol SRF is less hygroscopic than conventional brake fluids - it absorbs less water in a given time. Secondly, unlike conventional glycol ether fluids, Castrol SRF reacts chemically with the absorbed water to reduce its adverse effects, thus preventing the fluid's high temperature performance and safety margins from deteriorating as rapidly as they would otherwise do."

[Cuzza]

Pesky said:

Cuzza said:

or the LoT guys and I don't know anyone who uses SRF (including the Honda crowd).

Perhaps your're not looking hard enough then - plenty of the Exige racers/trackdayers do in fact use SRF. Fortunately, I've only got little feet, so my boots don't need much filling

At the price, that's probably a good thing

[Pesky]

Cuzza said:

At the price, that's probably a good thing

Can't argue with that