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Discussion Starter #1 (Edited)
What brake fluid flush intervals my fellow track rats are adhering to in the Lotus world? Keep in mind I am not referring to daily drivers, but people that get to the track six weekends or more per year.

I am coming from the BMW MINI platform and after a butt puckering moment with six month old ATE 200 fluid boiling I've been playing it very conservative. I used to flush before every weekend with my MINI. Even went up to Motul RBF600.

Now that I'm with the Elise, the braking heat is more balanced between front and rear in addition to not needing to stand on the brakes since the car is so light. However, I don't want to be totally overdoing it and just wasting lots of money on fluids. What would you guys recommend?

Additional details:

-SS brake lines
-Carbotech XP8/10 pads
-Stainless brake pistons
-Motul RBF600 fluid (flushing before each weekend)
-Toyo R888
-Usually run in advanced intermediate run group
-Live in Michigan and track days range from 60-80 deg F with mild humidity

Appreciate the help:up:
 

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i'm still bleeding prior to every event. Typically one bottle of RBF600. If an 'event' is the entire weekend, i'll only bleed once. $15 is a drop in the bucket compared to the other costs of going to the track.
 

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i'm still bleeding prior to every event. Typically one bottle of RBF600. If an 'event' is the entire weekend, i'll only bleed once. $15 is a drop in the bucket compared to the other costs of going to the track.
I totally agree! Before every track day and once a year for street cars.
 

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Discussion Starter #4
In my mind there is a difference between a bleed and a complete flush. I can understand bleeding any potential bubbles, but when I say "flush" I am referring to putting a liter of new fluid in the entire system.
 

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so I put a pint through before every event... effectively a flush every other event. Full flush prior to the beginning of the season.
 

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re: Bleeding and flushing the brakes

Why would you need to bleed the brakes before/after each event. If you think air is getting into the system? Fix the brake system it should be sealed! The other and more common reason is that the break fluid gasses out i.e. has a high gas pressure and creates its own bubbles or has too much air dissolved in it and slowly lets it come out. Both are problems with break fluid i.e. a critical temperature at which the fluid does not boil but creates/releases a lot of gas is reached.

One of the solutions is to reduce the overall amount of heat going into the break fluid. The solutions are common i.e. break ducts, larger rotors, new (thicker pads), caliper pistons made from stainless or titanium (low heat conduction materials).

Boiling the break fluid is a continuation of the same problem described, above.

There is no avoiding proper set-up of the break system i.e. cooling, as described above.

However, low boiling point and break fluid gassing out has been solved!

It is called Castrol SRF. I never have to bleed the brakes. I change it every season in my race car. It is more $$, but if you are bleeding and flushing every event, SRF is much cheaper TCO! and it provides the highest wet boiling point, so it is very hard to boil!

Anton
 

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Discussion Starter #8
I forgot to add I have stainless steel caliper pistons so that helps a lot.

Yes, I'm not really concerned with air but more of moisture intrusion that reduces the wet boiling point.

What affect does extended heating of brake fluid have on the long term boiling point? I'm referring to a level of heat that will not boil the fluid from the start. Just curious if this affects the chemical composition long term. :confused:

Ageshelin, I'm assuming this is a Lotus as a race car? How frequently do you race per yer?
 

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I forgot to add I have stainless steel caliper pistons so that helps a lot.

Yes, I'm not really concerned with air but more of moisture intrusion that reduces the wet boiling point.

What affect does extended heating of brake fluid have on the long term boiling point? I'm referring to a level of heat that will not boil the fluid from the start. Just curious if this affects the chemical composition long term. :confused:

Ageshelin, I'm assuming this is a Lotus as a race car? How frequently do you race per yer?
Extended heating affecting boiling point? Essentially none.
Lowered boiling point is a function of water content, and amount of moisture in brake system is a function of time/climate not use.

I think bleeding the brakes can be a cheap insurance. If you have to flush it often, you have bigger problems than boiling of the fluid.
 

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Discussion Starter #10
Extended heating affecting boiling point? Essentially none.
Lowered boiling point is a function of water content, and amount of moisture in brake system is a function of time/climate not use.

I think bleeding the brakes can be a cheap insurance. If you have to flush it often, you have bigger problems than boiling of the fluid.
That's assuring. Whenever I do flush it I never have bubbles so I'm not braking like an idiot. Maybe just being wayyyyyyyy to conservative after a bad experience.
 

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Why would you need to bleed the brakes before/after each event. If you think air is getting into the system? ...
I do it because

- its easy
- its cheap
- it offers piece of mind

The last thing I want to do is be out on track and find out I misjudged the 'need' to put some new fluid through. It doesn't take very long to run a pint through the system. Going off OP's post on number of track weekends per year...

$15 * 6 events = $90
$15 * 12 events = $180
Stated cost of SRF = $70

$20 - $110 is peanuts compared to all the other costs. I suppose I like to over-maintain the car, but I never professed what i do is required.
 

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Like Shane, I've learned the hard way with brake fluid with the MINIs, as they were very tough on fluid..

I like to keep the bar raised with the Lotus, so IMO the minimum I've used in mine is RBF600, where I'd flush it with my Motive pressure bleeder [which rocks], and do all 4 corners plus the clutch, which many people forget it shares the same reservoir.

I've been using Castrol SRF for a couple years now and it's a superior fluid for boiling tolerance as its wet temp is higher than most others dry points, which is pretty much a theoretical number since as soon as you open the bottle it's guzzling in the atmosphere humidity.

The SRF is so good that I only flush it once a year, and I've never boiled it at a track day. If you're an easy braker then the RBF600 is good enough, slightly cheaper, and honestly has a better pedal feel than the SRF. Since the RBF600's wet boiling point is so much lower, you'll need to flush it likely 2x a year.
 

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^^^ Castrol SRF is THE best brake fluid available on the market...pricey though. you get what you pay for.

I flush mine annually, think they put a PBR product in there last time and it was brilliant. the track I go to is VERY hard on brakes, i cooked the rotors and there was no fluid boiling.

Also, whoever said Lotus has a well balanced brake bias front to rear...not true. The Elige is known for being far too forward with the bias. To counteract this im trying a higher friction compound in the rear to get them actually working.
 

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Discussion Starter #14
I think I'll give SRF a go next year some time next year after I get through these six bottles of RBF600 I have left :D

Today it took me about an hour and a half to bleed my clutch and brakes. Playing limbo with the middle aero tray is a pain in addition to being super careful not to get any drips of brake fluid on my paint. The idea of flushing once per track season is extremely attractive to me. Inspecting the car thoroughly takes up enough time.
 

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re: Water in the brake system

And how does water get into a hermetically sealed system, like the brake system? Water molecules are much bigger than air gases, so if air cannot get in, neither does water.

Therefore, the argument, above, still applies.

In fact, this is why, I love, SRF so much. It has the highest wet boiling point!
Most brake fluid absorb water during handling and pouring and from the old left-over fluid. This very small amount of water has a very negative effect on boiling point. But not with SRF!!!

Anton


Not only is flushing to get rid of air but also water.
 
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