Brake fluid - is APL Racing Formula Dot 5.1 suitable?

[RichardS]

I'm ready to fill the brake and clutch circuits.

I'm browsing the Burton catalogue and APL Racing Formula Dot 5.1 looks suitable for road use for my Elan Sprint.

Before I order would appreciate confirmation that this is the right stuff for the job.

Thanks

Richard

[Old English White]

I'm ready to fill the brake and clutch circuits.

I'm browsing the Burton catalogue and APL Racing Formula Dot 5.1 looks suitable for road use for my Elan Sprint.

Before I order would appreciate confirmation that this is the right stuff for the job.

Thanks

Richard

This ll be good .
If it has been a long time between the last change , leak could appear . The new product and its new acidity can be hard on old joints and rubbers .
Personnaly , all my cars are fitted with Automec silicon product.

Safe for paint and metal , and having no problem with humidity . Btw , 5.1 .
If on new system must be considered.
Christian.

[steveww]

I use Castrol SRF high temp racing fluid. This is fully compatible with the standard seals. Despite some serious abuse I have yet to boil the fluid even with the pads fading from the heat.

[RichardS]

Thanks for the replies.

Steve - I did look at the SRF but its pretty expensive and I suspect that I will not be driving too hard when I get my Sprint back on the road - at least not to begin with!

Christian - I thought that silicon brake fluid was not recommended, from looking through previous posts.

I also see that Miller do a Classic Brake Fluid so this may be an alternative.

Richard

[andyelan]

Hi Richard

I used a DOT 5 synthetic fluid in my motor bike and I wasn't very happy with it. After a week or so, brake lever travel would get longer and longer to such an extent that I was having to bleed the brakes every 3 to 4 weeks. Left any longer than this and I would loose the brakes altogether. This would happen even if the bike was just stood for a while. I've no explanation of why this should have happened, the fluid was new and the system was all in good condition with no leaks. On returning to normal DOT 4 fluid (Halfords own brand) I've never had a problem since.

Andy

[Old English White]

Richard ,
It has been years -15 no less- when I started to use silicone fluid for brake & clutch on my cars .
The first one was my Spitfire 1500FH , having the two pumps right on the metal of the engine bulkhead ...
The only extra precaution is to clean the whole circuit with alcool when not using a brand new one ... And not forget that you have done because you can't mix with another .
As you , I am not a racer , but good for a track day , that fluid never failed .
If some of you have a different story ... or scientific reasons ...
Christian.

[GrUmPyBoDgEr]

For what it's worth another couple of points of view:
Whilst rebuilding my Elan another owner recommended using dot 5 silicone fliud which he had used in his Elan.
So that's what I did.
When I took the car for a suspension set up at TTR, Tony was horrified when he saw the blue fluid in the reservoirs & insisted on replacing it with dot 4.
His explanation was that, as we all know, dot 4 is hygroscopic & will subsequently absorb moisture.
This causes a known gradual degradation, which can be catered for by regular fluid changes.
The silicone dot 5 fluid is not hygroscopic & therefore will not absorb moisture.
(That strangely being the sales propoganda )
Subsequently any moisture entering the system, especially at the calipers will form bubbles of water which will boil off at high temperature, causing a soft peddle or even worse.
This was, for me, a justifyable explanation & I have stuck to dot 4 since then.

Cheers
John

[andyelan]

Hi Everyone

John, that's an explanation I heard too.

Any water which gets into a brake system containing a mineral brake fluid will be absorbed into it (miscible, I think is the word) This will lower the overall boiling point of the fluid but not by a significant amount as there's alot of fluid and only a tiny amount of water. However, if the fluid cannot water, as I believe is the case with silicon fluids, then any water which does finds its way into the braking system will stay as little blobs floating around. It is then possible, under heavy breaking, that these can boil so forming pockets of steam which, being compressible, can give rise to much increased pedal travel, somtimes to a dangerous extent.

I know I will always stick to DOT 4 or at least a "Road" rather than "Racing" fluid for normal road use

Andy

[paddy]

How is the water supposed to enter the system?

If there are leaks at the extremities of the system, you have a problem whether there is water there or not.

The only part of the system exposed to air (containing moisture) is the reservoir. If DOT5, which is incapable of absorbing moisture, then presumably the water will stay in the air and cannot enter the system.

I don't understand how this is supposed to happen, and I have to imagine that someone thought about it before DOT5 was introduced

Paddy

[cabc26b]

Thank you Paddy ! the phobic/philic nature angle was not jiving with me either.

I now use Motul RBF 600 , "Dot 4" fully synthetic , works for me under all conditions including full race, I try to stay on top of hydrolic sytem - getting this wrong takes the joy out of the driving experience..


George

[GrUmPyBoDgEr]

How is the water supposed to enter the system?

If there are leaks at the extremities of the system, you have a problem whether there is water there or not.

The only part of the system exposed to air (containing moisture) is the reservoir. If DOT5, which is incapable of absorbing moisture, then presumably the water will stay in the air and cannot enter the system.

I don't understand how this is supposed to happen, and I have to imagine that someone thought about it before DOT5 was introduced

Paddy

Paddy,

I must disagree here.
The calipers, read here pistons, are exposed to the elements more so than the reservoir. there is water all over the place in damp or wet conditions. There are also massive temperature changes there, causing expansion & contraction.
In theory that contraction could cause moisture to be drawn into the caliper.
In turn if that moisture forms bubbles rather than being absorbed into the fluid it will ,at the next strong application of the brakes, boil off causing the aformentioned "soft peddle".
I'm not certain about the "thinking" when dot 5 was introduced but I did hear that it was considered highly suitable for historic cars that stood in museums storage etc. for extended periods.
I'm sure that there are better qualified people on here that can probe deeper into the science of these brake fluids & offer a definitiive explanation for the thinking behind dot 5.
To conclude, why is it that todays car makers all use dot 4 & not dot 5?
I don't think money comes into the equation here because every effort is made to cut servicing costs to the customers benefit & so called "long life" dot 5 fluid would offer a considerable saving.

Cheers
John

[andyelan]

Hi Everyone

As I understand thing, under ideal conditions, DOT 5 has a higher boiling point and performes better under extreme conditions, which is why it's uesed in racing cars (ever seen carbon discs glowing red hot). However, racing cars are stripped and rebuilt, and the fluids changed much more frequently than on road cars. For a road car the brakes are worked nothing like so hard so absolute performance is not necessary. What's more important here is that fluid will last along time and be accommodating of extreme wet and dirty environments.

Finally, on most of the literature for race spec. fluids I've seen, it specifically states "not for road use"

Andy

[paddy]

Hey, I'm just asking the questions, I don't know the answers

Paddy

[memini55]

I have used silicon fluid, dot 5 in three or four of my british cars now and would like to add a few comments from my usage. The cars include two old mini's, a morris pickup and a +2 Elan. All of these have had full rebuilds from fresh parts all the way through the system. To date all four of these have worked extremly well with no issues and no softening of pedal. The +2 has been done the longest of the bunch and going on 4 years. This car is driven only from spring to late fall as we get too much snow in the winter. It is a 72 non fed car which had a booster, but that was removed at the time of rework. This is my son's car and he drives it hard most of the time and has done several solo events and no issues.

I think the very important point in this has been starting from fresh bits which included SS pistons in all calipers. Can't say much to the technical but can say we have been very happy with the results.

Mark

[cabc26b]

Check out this link for more on the subject

http://www.stoptech.com/tech_info/wp_brakefluid_1a.shtml
- confirms what John has been saying about dot 5, however points out how DOT 5.1 avoids the pitfalls, also illuminates other factors that may be helpful to the original post ( and others on bleeding with pressure bleeders)

G