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Brake Fluid Day - What DOT?
http://www.gt4dc.co.uk/forum/viewtopic.php?f=1&t=4892		 Page 1 of 2
Author:  emicen [ Fri Apr 29, 2011 8:17 pm ]
Post subject:  Brake Fluid Day - What DOT?
So chaps, what's best for a track and fast road ST205 on standard calipers running yellow pads?

Ran RBF600 in the Mini with good results but dunno if that's suitable for the ST205's older spec seals etc.
Author:  Sunny [ Fri Apr 29, 2011 9:04 pm ]
Post subject: 
Hi,

DOT4 is perfect

greetz
Author:  Nibbles [ Fri Apr 29, 2011 9:40 pm ]
Post subject: 
or 5.1

avoid dot 5 as it's not compatible.

I'm sure oilman did a write up on brake fluids somewhere.
Author:  Sunny [ Sat Apr 30, 2011 10:20 am ]
Post subject: 
Hi,

DOT5 is a silicone bases brake fluid just for race use (do not allow the water to bond with itself)

DOT5.1 is like the other specifications a glycol bases fluid for road use (water will bond with it), the issue is they higher the specification they more aggressiv is the fluid which can occur damages seals, rust and non working brake pistons
(a friend of mine and mechanic confirm this to me)

the system of our cars is build for DOT4
i will go for millers oils racing brake fluid 300 plus (DOT4) if it helps


greetz
Author:  two_OH_five [ Sat Apr 30, 2011 11:52 am ]
Post subject: 
Hannibal has been running DOT5 for years now with no ill effects

TBH I just run generic 5.1 in the black car and I've never experienced any issues on track with it even when rurnning hard enough to blue the disks. Maybe over the course of a full distance race differences would become apparent but for the real world I personally find no difference between race spec dot5 and halfords spec dot5.1
Author:  Nibbles [ Sat Apr 30, 2011 12:08 pm ]
Post subject: 
My understanding is that dot 5 was developed for high performance road use with the silicone base to avoid the rust problems. The downside is that it is more compressable and leads to a spongy pedal, hence why it has never taken off.

Never tried the stuff, just going by what I've been told.
Author:  two_OH_five [ Sat Apr 30, 2011 12:43 pm ]
Post subject: 
Hard to comment on that one

Both mine are equipped with ABS and I find the pedal (In common with every gt4 i've driven) about as firm as Bella Emberg's butt. There's no lack of power but a distinct lack of genuine pedal feel
If anything Hannibal is slightly better on dot5. Both are rock solid unservod though
Author:  emicen [ Sat Apr 30, 2011 1:24 pm ]
Post subject: 
two_OH_five wrote:
Hard to comment on that one

Both mine are equipped with ABS and I find the pedal (In common with every gt4 i've driven) about as firm as Bella Emberg's butt. There's no lack of power but a distinct lack of genuine pedal feel
If anything Hannibal is slightly better on dot5. Both are rock solid unservod though


I drove one with a very solid brake once, but nowhere seems to make brake master cylinder braces anymore ;)

If you watch the servo and brake cylinder when getting someone to mash the pedal its ridiculous how much they flex.

Think I'll go with some Halfrauds special 5.1 for ease and cheapness (tradecard ftw!)

I would throw in some RBF I still have sitting around but I remember hearing there's a compatibility issue of some sort with this and other fluids so you sometimes have to flush the system fully which is more hassle than I'm after for a marginal gain in performance. Also my RBF600 sucked in water and crap at an annoyingly high rate.
Author:  Sunny [ Sat Apr 30, 2011 2:43 pm ]
Post subject: 
Hi,

two_OH_five wrote:
Hannibal has been running DOT5 for years now with no ill effects

TBH I just run generic 5.1 in the black car and I've never experienced any issues on track with it even when rurnning hard enough to blue the disks. Maybe over the course of a full distance race differences would become apparent but for the real world I personally find no difference between race spec dot5 and halfords spec dot5.1


great and underline the quatity of toyota parts

the issue is when water don't bond with the fluid that there is a chance of water vaporisation when hot which means braking is not 100% safe

(the fluid becomes hot while braking -> you put off the food from the brake pedal -> pressure lowers -> water vaporises [boiling point ~100°C at atmospheric pressure] -> you pull the pedal again -> now the damp becomes compressed -> no brake power)

race cars do not have the problem as they become the fluid changed every race, i would not advise to use DOT5 for road cars with long changing intervals even it works

greetz
Author:  two_OH_five [ Sat Apr 30, 2011 5:59 pm ]
Post subject: 
Similarly, one of the issues with dot5 is it's not hydroscopic. In fact I believe it's hydrophobic. This means any water that does get in (condensation on the mcyl cap for eg) pools in the lowest point or wherever it gets stuck. typically wheel cylinders and abs pumps :(
Author:  Sirius [ Sun May 01, 2011 8:36 pm ]
Post subject: 
I use Castrol SuperResponse DOT 4 in my car, seems fine, been using it for about 6 years now.
Author:  whitie_bear [ Wed May 11, 2011 9:32 pm ]
Post subject: 
factory spec is dot 3, however i swapped mine out for a generic dot 4...great feel


check the st205 specs, youll see that dot 3 is called for (but as stated, put in the dot 4 for intense duty)
Author:  Sirius [ Wed May 11, 2011 10:11 pm ]
Post subject: 
Thats true Whitie - although I am not sure if you can even buy DOT3 anymore?! I don't recall seeing it for a long time.
Author:  Jon9985 [ Wed Sep 26, 2012 3:26 pm ]
Post subject: 
I know this post hasn't been touched for a while but I was checking my brake fluid yestaday and it needs topping up and as stated above, it takes dot 3. Is it ok just to top up with some halfords universal brake and clutch fluid dot 4..... ?
Author:  Nibbles [ Wed Sep 26, 2012 4:47 pm ]
Post subject: 
yes.
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