Brake Fluid Swap

[type26owner]

Going to drain the DOT5 silicone brake fluid with DOT3 glycol stuff because the compressibility of the DOT5 when heated makes it unsafe for the racetrack. (My one outing on this particular track I heat warped the rotors on my wife's C5 Corvette in about 15 laps so I know the brakes are essential there for me. Geesh, the bummer is she won't let me borrow her car anymore. ) Anyway I've been looking into the issues involved in switching them and the only one I see as a real limitation is the density difference. DOT5 floats on top of the DOT3 stuff. Since the caliper bleed valves are located on the top this presents no problem going this way. Once filled with DOT3 though it's now impossible to displace it out the top valves with the lighter DOT5 fluid. That swap direction requires the bleed valve be located on the bottom of the calipers or the calipers have to be loosened and turned upside down to drain out the DOT3.

Since I've used both the DOT3 and 5 stuff with these calipers seals I know for a fact there is no seal degradation that takes place. The caliper seals are fresh as of about six months ago. Going to monitor the temps and if the calipers get real hot I'll rebuild them straight away.

BTW, tested my brakes the other day while resolving handling issues and succeeded in melting the pads after three consecutive threshhold braking tests from 70 to 20 mph. They then glazed after cooling back down. Bought a set of blue KFP Magnum pads after talking to Lee Chapman about performance stopping the Elan. Anyone try these before? Opinions?
-Keith

[1964 S1]

Downshift more, brake less? Heel-toe?

[type26owner]

Can't. Trying to reduce the performance gap to my younger brother's Super7.

[1964 S1]

Sell the Corvette and type 26 and buy a Super Seven? ps; whadya mean "can't"?

[patrics]

Hi Keith,
I would remove the calipers and take out pistons and seals, clean inside the bores with IPA. For what it costs fit new seals, but before fitting soak them overnight in brake fluid. I would also do the same with the m/cyl

On the car pump fluid through the pipes and hoses without the calipers fitted. I would use a banjo bolt, inline fitting, bleed screw and a couple of copper washers to seal off the hoses whilst bleeding.

Regarding the rubber bits there can be a problem where the two types of fluid meet. Try it by putting both fluids in a jar and suspending a caliper seal between the two seperated fluids. Haven't seen this done for many years but seal should turn into chewing gum at the join.

If your using the car on the track then use a Dot 5 or Dot 5.1 fluid. Dot 5.1 is a lower spec than Dot 5 but has the same high temperature properties. Can you still buy dot 3 in the US?

Regards
Steve

[type26owner]

Hi Steve,
EPDM is used almost exclusively for brake system elastomers. If you research the literature I think you'll find EPDM is the recommended type to use for ALL the types of DOT fluids. Also are you aware the DOT has a federal statute that bans the manufacture or sale of any brake fliud which is not totally compatible with the existing ones. It's to prevent the very situation which you've said exists.

Would be most interested if you could find one single credible reference which describes the problem mixing DOT3 and DOT5 fluids and it affecting the EPDM. Most brake fliud manufactures recommend not mixing different fliuds but none that I can find explain why. The density layering effect I believe is why they issue that recommendation. Okay, that could cause a problem for anyone not familiar with hydraulics.

I have done that test before though. Noted no change to the EPDM even after several years. However I did notice the glycol did extract all the blue dye from the silicone fliud overnight. Try it yourself.

Recently overheated the silicone brake fluid in my Elan while being towed on a short rope by mistake. When this happens the brake pedal goes to the floor and no matter how many times it's pumped it does not help it stop any better.

DOT3 must be used in about 90% of the vehicles on the road still today. I hate the high maintenance aspect from it being hydroscopic. Fear having no brakes when I really need on them on the racetrack even more though.

Regards,
-Keith

[type26owner]

Sell the Corvette and type 26 and buy a Super Seven? ps; whadya mean "can't"?

Can't, because I already own the perfect sports car for road and track. Anything else is trading down including a Super7.

BTW, if you've ever gone through driver's school you'd know this. Usually one of the first things they teach you is the brakes are for slowing down and you should not use the gearbox for that purpose. The chance of breaking the rearend loose after turning in makes this a foolish practice while at the limit in the traction circle.
Regards,
-Keith

[1964 S1]

I've been through school and raced, set track records, never had a brake problem, will stick by my heel toe suggestion. I don't think the Elan will catch the Seven tho' I also find the Elan a superior car.

[patrics]

Hi Keith,
I think you are correct about the compatibility with EPDM, the test I referred to was probably with SBR type seals.
No manufacture is going to recommend mixing fluids - think of all the tests that would have to be carried out and at what % mix?
Dot 3 hasn't been used in Europe for a long time.
Being hygroscopic might be a good quality in that being compatible with water the hot or cold performance isn't greatly reduced.
High maintenance with brakes that work or low with ones that don't - Tuff one that!
I would still recommend changing the fluids over in the same way even if you decide to keep the seals and dot 3 isn't good enough for a race track.
Regards
Steve

[steveww]

Most road cars do not have good enough brakes for the race track including those models with a sports bias. Even with the mighty Porsche GT3 you can soon cook the brakes after a couple of laps, same with the Turbo too. Their ceramic disks do not do much better with track use, OK so they stay the course during the day but after a number of track session they start to crack. Here in the UK BMW say that their warrenty is void if you tack the car on the track. Hmm Utlimate Driving Machine


Performance Friction do very good disk upgrades for the Porsche, they might do a kit for the C5, if you are allowed out in it again

For the Elan I have fitted the front disk/calipers from the +2. I use EBC green pads front & rear and their performance disks front only, not managed to cook these yet.

[type26owner]

Hey Steve,

For the Elan I have fitted the front disk/calipers from the +2. I use EBC green pads front & rear and their performance disks front only, not managed to cook these yet.

Heard that the green ones are okay from several sources so your opinion is well supported. Just in case I didn't like KFP's I also purchased a set of the EBC green ones so I had options. Brakes are one of those important things I never skrimp on.

Other then maybe doing a Diablo Valley Corvette parade my wife's C5 is not going back on the track. To wierd dealing with the handling consequences of the automatic tranny computer deciding which gear I would be allowed to use at the critcal moment apexing. I got into trouble (high pucker factor stuff) a couple of times because it chose poorly. Never did figure how to drive around those issues before the black flag came out and I was done for that day.
Regards,
-Keith

[1964 S1]

Hello Steve W,
are you saying the Porsche brakes are so poorly made they malfunction after a few laps of competition driving? Is it because it weighs so much or is it a lack of quality materials? How much does a mighty GT3 cost?

[steveww]

Not that they malfunction it is just that they get too hot and fade. I do not think you could ever get this to happen on the road. I had it happen to me at Donnington after about 10 fast laps there was serious brake fade and I had to do a cooling down lap then go in to the pits. Donnington is a hard circuit on the brakes with 2 really big stops every lap they never really get a chance to cool.

However I have taken my elan around Donnington with no problems at all. Ah the joys of light weight 700kg vs 1400kg Oh and 100mph vs 150mph down the main straight

[davidholroyd]

castrol racing brake fluid and 2" air ducks from under the front nose to the front brakes ... no fade ( hoover pipe ! ) ..

[elandoc]

<!--QuoteBegin-davidholroyd+Oct 15 2004, 01:40 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (davidholroyd @ Oct 15 2004, 01:40 PM)</td></tr><tr><td id='QUOTE'><!--QuoteEBegin--> castrol racing brake fluid and 2" air ducks from under the front nose to the front brakes ... no fade ( hoover pipe ! ) .. [/quote]
Interesting, David.
I removed the indicators and ducted through the holes. It worked well (+2 calipers and discs with Cool Carbon pads), but had to put them back in for class reasons. Just for an experiment, I changed the brakes to Wilwood 4 pot DL with custom (read bloody expensive) brackets in 7075 T6 alloy and Ferodo DS 3000 pads. Now when I press the brake pedal, I go backwards in time.
Patrick