jrd Posted July 12, 2006 Share Posted July 12, 2006 Hi all, Had a bit of a scary ride this morning. As some of you may know, I have set up my 1970 240Z with thermocouples on the caliper pistons so that I can use the car to test the effectiveness of the Fade Stop Brake Coolers. I put a pair of coolers on the drivers side caliper and leave the passengers side stock, then I drive down Hwy 2 from Mt Wilson into Glendale (Los Angeles). It is an altitude change of more than 3500 feet. While I did this before with the prototypes, I am now using the manufactured brake coolers and some Hawk HB Plus pads. These pads are capable of much higher temperatures than the Sumitomo pads I was using with the prototype. While I drive down the mountain, I record the temperature data on a data loger from the two sides while I descend...I get on the brakes A LOT so that I can get them nice and hot. The data logger has a screen that shows me the data while it is being recorded. Here is what happened: as I hit the bottom of the mountain, the passengers side caliper piston (no cooler) hit a temperature of around 420C while the drivers side (w cooler) was somewhere around 250C. What was going through my brain at the time is "this is GREAT data!" What should have been going through my brain is "WAIT, DOT 3 brake fluid boils at around 210C!" Luckily, I was actually going quite slow at this point, 'cause when I stepped on the brakes, my foot went to the floor. If you have never had this happen to you then be thankfull - it is NOT a pleasant sensation. I frantically PUMPED the brakes many, many times and still nothing - I had REALLY boiled the fluid in that passengers side caliper. I then grabbed the O-Crap handle and pulled...the emergency brake did what it was supposed to do and I used it to limp over to the empty parking lot of a nearby strip mall. I then slowly drove around a shopping area until my brakes returned - it took over 20 minutes! Those cast iron calipers retain the heat for a long time. I then drove into work without any trouble. What is next? Well, I need to do it again. For the data to be complete I need to put the coolers on the passengers side and leave the drivers side stock and retake the data and then average the results. I think that I will replace the DOT 3 with a racing fluid at this point though. It shouldn't affect the data at the piston/brake pad interface and there are some pretty significant drops along Hwy 2. Once I am done, I will put the data on the fourproducts website - it looks like it will show some significant differences. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 12, 2006 Share Posted July 12, 2006 My suggestion would be ATE Super Blue fluid. Not too expensive, available at most European repair or parts shops, and has a nice high boiling point. Here's some more info: http://forums.hybridz.org/showthread.php?t=103862 Quote Link to comment Share on other sites More sharing options...
jrd Posted July 12, 2006 Author Share Posted July 12, 2006 Jon, do I need to replace the seals to do this? I assume that I need to flush out the DOT 3 completely before the upgrade. Thanks, Joe Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 12, 2006 Share Posted July 12, 2006 It mixes fine, it's not silicone or anything weird like that, so you don't need to flush it. The Super Blue is as the name suggests. So you can just keep bleeding until the fluid coming out of the bleeders is "super blue" and you'll be fine. You can save some time by sucking the fluid out of the reservoirs with a turkey baster. Quote Link to comment Share on other sites More sharing options...
bjhines Posted July 12, 2006 Share Posted July 12, 2006 Hey... I was using the non vented Toyota calipers on track for a season... they would overheat and cause problems with sticking pistons... even though the pads and fluid were fine... Just an FYI.... if you start to feel like the car pulls to one side... or is heating one wheel more than the other going down the highway wihtout using brakes.... then in all likelyhood you have burned the seals... I run em till they stick... or I do a major overhaul... I usually end up replacing the seals every season.... Quote Link to comment Share on other sites More sharing options...
tube80z Posted July 12, 2006 Share Posted July 12, 2006 Hey... I was using the non vented Toyota calipers on track for a season... they would overheat and cause problems with sticking pistons... even though the pads and fluid were fine. I ran those for about a year and had similar problems. I found that if you flip the pads each session (or event for an autoxer) and use spacers to keep the pistons from coming out too far it will help. But you can cook the seals. Then there's that issue with how to cool the brakes properly. Cary Quote Link to comment Share on other sites More sharing options...
johnc Posted July 13, 2006 Share Posted July 13, 2006 I typically throw away the rubber dust seals around the caliper piston and periodically remove the pistons and replace the actual piston seals every few months when racing. As John recommended, ATE Super Blue is great when doing a complete fluid replacement. The color makes it easy to know when you've flushed the old stuff out. Castrol SRF has the best wet boiling point but its stupid expensive. Quote Link to comment Share on other sites More sharing options...
mom'sZ Posted July 13, 2006 Share Posted July 13, 2006 In the process of preparing a road racing car (78 280Z for SCCA ITS) I had planned on using the DOT5 silicone based brake fluid for higher boiling point. I was going to replace the entire system with new components including new master, calipers, rear cylinders, hard lines and S/S flex lines, so compatibilty with the old fluid would not be an issue. After reading this thread and also the thread linked in Jon's Post #2, I'm not so sure it's a good idea. I was under the impression (probably incorrectly) that the DOT5 was superior for track use. Would anybody like to comment on what they think is best? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 13, 2006 Share Posted July 13, 2006 Don't use silicone on a track car (I wouldn't use it on any car). I like the Super Blue because it is cheap and isn't as sensitive as some of the other racing fluids that have a higher dry boiling point, and it's pretty easy to find too. Quote Link to comment Share on other sites More sharing options...
johnc Posted July 13, 2006 Share Posted July 13, 2006 There's a lot of confusion regarding silicone brake fluid (DOT 5) and a new specification that's not silicone (DOT 5.1). As Jon said above, silicone based brake fluid is not for performance use. It boils easily and any water contamination ruins it. Stick with a good DOT 4 brake fluid. Quote Link to comment Share on other sites More sharing options...
mom'sZ Posted July 13, 2006 Share Posted July 13, 2006 Jon, I value your opinion greatly, and if you say not to use it, I would take that as gospel. But just out of curiosity... why not? compressability? (softer pedal)? Anyhow, super blue it is. ATE is the manufacturer? Any online source? You know, guys at the local part stores are morons, and if you can't find it on the shelf they stare at you like you have three heads, so for me a lot of times it's easier to order stuff online and I'm going to need a lot. I forsee many fluid changes in my future. I'll google Quote Link to comment Share on other sites More sharing options...
jrd Posted July 13, 2006 Author Share Posted July 13, 2006 For all those interested here is the raw data from testing. Red is the passenger's side without a cooler and black is the drivers side with the cooler. Unfortunately, something happens to the passengers side thermocouple after it hits 440C and it becomes very noisy - I haven't had a chance to look at the car yet, but it appears that I will have to take the data again - but not until I am running some Super Blue. Quote Link to comment Share on other sites More sharing options...
mom'sZ Posted July 13, 2006 Share Posted July 13, 2006 Thanks JohnC, I believe you just answered my question Quote Link to comment Share on other sites More sharing options...
Darrel Posted July 13, 2006 Share Posted July 13, 2006 Is there ducting going to the calipers for the tests? Quote Link to comment Share on other sites More sharing options...
jrd Posted July 13, 2006 Author Share Posted July 13, 2006 Yes, both calipers have the same ducting. With the side without the coolers I try to aim th air at the pads. I have to take some photos of the ducting for a gentleman who bought some FSBCs - I will post the photos Quote Link to comment Share on other sites More sharing options...
jrd Posted July 13, 2006 Author Share Posted July 13, 2006 By the way - the ducting is attached to a BRE spoiler up front that I just installed. Having my Z as a test vehicle makes all these accessories a write-off. I think that my accountant even said something about research tax credits. How great is that???? Of course write-offs are no stinking good if you aren't making any money! HAHAHA JRD Quote Link to comment Share on other sites More sharing options...
olie05 Posted July 14, 2006 Share Posted July 14, 2006 Isn't there a safer way to test than to run a cooler on one side and nothing on the other side? when I first read the sentence where you described how you were only using ONE cooler, I thought horrible things were to come at the end of the post. then again, im a compulsive symmetrist... is that even a word? Quote Link to comment Share on other sites More sharing options...
stony Posted July 14, 2006 Share Posted July 14, 2006 Here's what not to do......... This is an actual story I over heard while at my friends shop. This guy walks in. he drives a 350Z. Real mouth to. He says hey I want to do something to keep my brakes cool. My friend replies what do you want to do. He says and I quote " I'm thinking of setting up some type of Co2 nozzles about 1/2 from the rotor and every time I hit the brakes it sprays C02 straight on the rotors" It was all I could do but not laugh. I turned around and walked away. Now am I the idiot or does this sound really stupid. I’m thinking hot rotors and extremely cold C02 sprayed on the rotor surface will be explosive???? Quote Link to comment Share on other sites More sharing options...
1 tuff z Posted July 14, 2006 Share Posted July 14, 2006 stony, i believe you've already id'd the real idiot. unfortunately he's driving a z...a 350z. i'm no engineer but it wouldn't surprise me if his rotors cracked pretty quick with the first spray. he's probably the same type who would hose off his engine to cool it down after a hard run. Quote Link to comment Share on other sites More sharing options...
jrd Posted July 14, 2006 Author Share Posted July 14, 2006 Having a cooler on one side, but not the other and then switching them and repeating is the best way to take accurate data. The "safety" issue comes from me pushing the car hard on a mountain road. The proper way to do it is to spend $2k and get Buttonwillow Raceway for a day. Now, jsut so all are aware, I am not speeding through corners on this mountain road, just the opposite. I am just waiting late to brake and then I am braking pretty hard. I don't think that I ever go over the speed limit and I have yet to squeal the tires in a turn. I am actually taking the turns pretty slow...you know, setting up properly for them. Slow in, fast out. JRD Quote Link to comment Share on other sites More sharing options...
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