2052006 10 Posted October 6, 2009 Did my first proper trackday yesterday and overall was quite pleased (mainly as my car survived after all the work I've done on it ). One issue that was highlighted, perhaps not surprisingly, were the brakes (or lack of them). Current set up is as follows: Refurbished 1.9 calipers Mintex 1144 pads Brembo Max discs Goodridge hoses front and rear New master cylinder Rears are still drums, but with new standard shoes Initially, the brakes weren't bad, but after a couple of laps, if I really stood on them (which I was), the pedal would eventually go "soft" as if it couldn't provide any more force on the calipers. The wheels never locked up either. I have never really driven a car hard enough for long enough to experience proper brake "fade" as have never done a track day before. I'm presuming this is what the car was suffering from on this occasion?! My initial thoughts are a problem with the fluid - it's new but only standard DOT 4. So my question is, would DOT 5.1 (is that right or is it just 5??) solve my issues OR is my setup as it is just not up to track work, considering I've still got the drums and standard calipers etc? Thanks for any advice Pete Share this post Link to post Share on other sites
projectpug 0 Posted October 6, 2009 Hi, Try some AP racing 551 brake fluid it is very good. Also you will probably overheat the m1144, could try a more dedicated track/race pad like a ds3000 etc. You will be surprised at how well you can make the standard(calipers/brake disc size) car stop:) Share this post Link to post Share on other sites
pablo 0 Posted October 6, 2009 DS2500s would be adequate, and a really good pad. you want 5.1 fluid btw, not 5 (its a funny one noone uses). Share this post Link to post Share on other sites
Galifrey 1 Posted October 6, 2009 (edited) DS2500s would be adequate, and a really good pad. you want 5.1 fluid btw, not 5 (its a funny one noone uses). AP551 is very good, exceeds 5.1 spec 270 deg C boiling point They do A 600 spec as well which is 300 degrees+ boiling point DOT 3,4,5.1 are Mineral Based and DOT 5 is Silicone based so is really for specific types of systems. Edited October 6, 2009 by Porsche911r101 Share this post Link to post Share on other sites
James_R 3 Posted October 6, 2009 I'm not a fan of 1144's I killed them on my 306, but it sounds much more like fluid being weak, I'd get some god dot4 like super blue racing (15quid a litre at GSF) looks awesome and does the trick. AP600/Motul RBF600 and castrol SRF are all DOT4's so can't be bad. Share this post Link to post Share on other sites
2052006 10 Posted October 6, 2009 What is the actual difference between a dot 4 and 5.1 fluid? My car is mainly a road car too, if that makes a difference to what I should use. Share this post Link to post Share on other sites
Galifrey 1 Posted October 6, 2009 (edited) What is the actual difference between a dot 4 and 5.1 fluid? My car is mainly a road car too, if that makes a difference to what I should use. 40 degrees celsius in boiling point. Dot 5.1 is generally more expensive so is only specified/used where brake fluid boiling becomes an issue. Brake fluid is Hygroscopic and absorbs moisture from the atmosphere, the more moisture the fluid contains, the lower the boiling point. There is no reason not to use 5.1 if you are suffering brake boiling as far as I am aware, maybe somebody else knows an answer to this? Edited October 6, 2009 by Porsche911r101 Share this post Link to post Share on other sites
Baz 421 Posted October 6, 2009 Initially i'd just try some 5.1 from halfords etc, works fine for me in a fast road/track car, without the mega expence of the other suggestions. Share this post Link to post Share on other sites
pablo 0 Posted October 6, 2009 always found halfords stuff ok myself. cheap too with a trade card. Share this post Link to post Share on other sites
Batfink 201 Posted October 6, 2009 dot 4 or 5.1 - just pick one with a good wet boiling point for track use. Kev Share this post Link to post Share on other sites
James_R 3 Posted October 6, 2009 40 degrees celsius in boiling point. Dot 5.1 is generally more expensive so is only specified/used where brake fluid boiling becomes an issue. Dot 4 can have a higher boiling point than 5.1 though. Just try 5.1 as said and see how you go, if you then get a stiff peddle and no brakes then think about a pad change, or bigger brakes. Share this post Link to post Share on other sites
Galifrey 1 Posted October 6, 2009 Dot 4 can have a higher boiling point than 5.1 though. Of course, the Dot number is a minimum spec, many brake fluids outperform this spec, but once wet they drop to the minimum performance (around 50 degrees lower boiling point than the dry rating). The only brake fluid not to suffer this is DOT5 and that isnt suitable or recommended for most brakes. Personally I would use 5.1 as you say, but AP DOT 4 will exceed a lot of 5.1's Share this post Link to post Share on other sites
2052006 10 Posted October 6, 2009 I have Halfords Dot 4 in there now as it was cheap with the trade card like someone said. They have some 5.1 stuff and also some "racing" fluid which is about twice the price. Anyone tried this so-called "racing" stuff. It was the only one to list the boiling temps on the bottle - over 300 for dry I think. Share this post Link to post Share on other sites
Anthony 1,002 Posted October 6, 2009 Whilst I don't do as many trackdays as some people on here, I've never personally had any issue with Halfords DOT5.1 fluid Share this post Link to post Share on other sites
James_R 3 Posted October 6, 2009 But you don't brake Share this post Link to post Share on other sites
Batfink 201 Posted October 6, 2009 carbone lorraine race fluid is DOT 4, synthetic - 325 Deg C Dry, 195 Deg C wet Thats one example as I have a box of them under my desk... Share this post Link to post Share on other sites
Galifrey 1 Posted October 6, 2009 carbone lorraine race fluid is DOT 4, synthetic - 325 Deg C Dry, 195 Deg C wetThats one example as I have a box of them under my desk... That's some nice numbers Share this post Link to post Share on other sites
