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purplehaze	Silicon brake fluid		Lead	[-]
Registered Member Posts: 10 Mon, 8-Jun-2009 21:07	Tags : None Does anyone have the definitive answer on this? Does it affect any of the rubber cylinder seals? I can't find any authoritative written comment. I want to use silicon brake fluid partly because mineral is such a nasty product and partly for performance reasons. I had boiled fluid on a track day which led to an interesting moment! The car is nearly back together. All brake lines and cylinders have been able to drain over a long period but I have not rebuilt the cylinders.
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Gary Harman		#1	[url]	[-]
Registered Member Posts: 1852 Mon, 8-Jun-2009 22:25 Guru mechanic	I asked my garage about this last week and they said refer to the part manufacturer for your car as they know of incidents where it has affected the seals, but it was fine on an E-type they were working on.
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MarcosMantula		#2	[url]	[-]
Registered Member Posts: 34 Tue, 9-Jun-2009 07:39	When I rebuilt my Mantula 8 years ago I went to silicon fluid. Everything except the clutch slave cylinder was replaced (master cylinders, calipers, brake lines) and the only thing to have failed is the clutch slave cylinder. It took 5 years, and may have gone anyway, but it does make you think there might be something in it.
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dparslow		#3	[url]	[-]
Registered Member Posts: 663 Thu, 11-Jun-2009 14:04 Chief mechanic	purplehaze wrote: Does anyone have the definitive answer on this? Does it affect any of the rubber cylinder seals? I can't find any authoritative written comment. I want to use silicon brake fluid partly because mineral is such a nasty product and partly for performance reasons. I had boiled fluid on a track day which led to an interesting moment! The car is nearly back together. All brake lines and cylinders have been able to drain over a long period but I have not rebuilt the cylinders. If you are managing to boil the brake fluid you may find you need to uprate the brakes and get more cold air to them rather than just change the fluid, standard Mantula brakes are not really upto serious trackday punishment. I have always used normal DOT 4 brake fluid which is generally used in most cars, it has a boiling point of 268 degees C and I have never had any problems. The disc pads have a working heat range upto 450 degrees C, but most of that is dissapated through the alloy callipers, alloy disc bells and wheels which have a good supply of cold air. It`s not more power you need, it`s less weight and a few subtle mods and some not so subtle!
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purplehaze		#4	[url]	[-]
Registered Member Posts: 11 Thu, 11-Jun-2009 17:02	Hi Dave It is not the same car that boiled the fluid, that was standard but this one has an upgrade including vented discs. I only had the problem once but it was quite a shock! I always used to do the final lap without using the brakes to cool them down. On this occasion I had been driving an instructor around Goodwood circuit and he asked me to pull in to the pit lane straight off a hot lap. He gave me a few tips and then we were off again. On the out lap you don't need brakes until you get round the back of the circuit (St Marys I think) which I always found the most difficult corner anyway. When I did tread on the brakes - nothing - or very little! At my loud expletive the instructor would have jumped out had he not been belted in! I put it down to that short stop in the pits with very hot brakes, would you agree? From what you say, now that I have the upgraded front brakes, maybe it is not worth the risk of changing fluid.
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OldNoccer	Boiled fluid	#5	[url]	[-]
Registered Member Posts: 614 Thu, 11-Jun-2009 20:16	I have had this once, but not in the Mantula. I put it down to a slightly sticky caliper getting hot, but mainly due to old brake fluid. It soaks up water from the air, and what boils is not the fluid but the water in it. It is very exciting when it happens ! On my Mantula I have the standard calipers, with the vented disks, and two gurt big hoses that connect the spotlight apertures (now fitted with large air scoops) to the hose, and duct air to the brake. The brakes aren't sensational, but I have not had problems. I don't know if the previous owner did this for any particular reason. Steve There's a lot of talk these days about green transport. Well, I am ahead of the game, I already have green transport ... British racing green.
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dparslow		#6	[url]	[-]
Registered Member Posts: 664 Fri, 12-Jun-2009 10:50 Chief mechanic	purplehaze wrote: Hi Dave It is not the same car that boiled the fluid, that was standard but this one has an upgrade including vented discs. I only had the problem once but it was quite a shock! I always used to do the final lap without using the brakes to cool them down. On this occasion I had been driving an instructor around Goodwood circuit and he asked me to pull in to the pit lane straight off a hot lap. He gave me a few tips and then we were off again. On the out lap you don't need brakes until you get round the back of the circuit (St Marys I think) which I always found the most difficult corner anyway. When I did tread on the brakes - nothing - or very little! At my loud expletive the instructor would have jumped out had he not been belted in! I put it down to that short stop in the pits with very hot brakes, would you agree? From what you say, now that I have the upgraded front brakes, maybe it is not worth the risk of changing fluid. Under those circumstances without the cool down laps, all the heat in the discs/pads will get absorbed into the calipers, fluid and also the hubs so not that good for the bearing grease also. If you have the vented discs you probably have the alloy hubs too, get some cold air to the brakes as Steve has and it will help them cool down quicker when on the move. These were the brakes on my Mantula Spyder and were the original fitment 260mm x 20mm vented discs, alloy hubs and cast iron 2 pot calipers. http://picasaweb.google.com/lh/photo/pVwQUmSi-PkfKcBjIQ58Pg?feat=directlink The brakes on NCM 109H 300mm x 28mm discs, alloy bells, hubs and 4 pot alloy calipers. http://picasaweb.google.com/lh/photo/S5m5KXC_Th4b3Zxhyn18lA?feat=directlink It`s not more power you need, it`s less weight and a few subtle mods and some not so subtle!
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OldNoccer		#7	[url]	[-]
Registered Member Posts: 621 Wed, 17-Jun-2009 08:15	When I said I 'have not had problems' I think I spoke too soon. The problem I have is getting the adjustment of the wheel bearings right so that the expansion of the aluminium hubs doesn't cause the bearings to nip. I stripped out a hub last night tracking down some play, and it looks like at some stage the bearings have nipped and the inner race spun on the stub axle. I adjusted it up a tad last year after the MOT man didn't like the play, I think I should have un-adjusted it afterwards. Does anyone know how much end float I should have with a correctly adjusted aluminium hub ? So there is another reason for air ducts - its to stop the hubs getting too hot and thermal expansion nipping the bearings (or loosening them turn in the hub). There's a lot of talk these days about green transport. Well, I am ahead of the game, I already have green transport ... British racing green.
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dparslow		#8	[url]	[-]
Registered Member Posts: 667 Wed, 17-Jun-2009 11:52 Chief mechanic	The Herald/GT6 always had lots of endfloat, the problem with a lot of younger MOT testers is that most modern cars have no play in the bearings and they assume thats how they should all be. I tighten my bearings up enough for you can still feel the free play in the wheel easily and usually you can get the nut tight enough by hand for this. As always it`s down to checking everything on a regular basis with these cars, they are not your typical reliable for years boring eurobox. It`s not more power you need, it`s less weight and a few subtle mods and some not so subtle!
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OldNoccer		#9	[url]	[-]
Registered Member Posts: 622 Wed, 17-Jun-2009 20:07	I think the tricky thing is that with worn bearings a little back off gives you a lot of slop, whereas with new ones it gives you less - so the problem is how to measure whether it is the former or the latter. I can calculate the expansion of the aluminium if I can guess just how hot it might get (150C?), maybe the trick is to get new bearings, hand tighten the nut, then back-off that amount (calculated from the thread pitch - or a dial gauge for end-float) and then measure the slop at the rim with a dial gauge. That way we have a way of diagnosing if the play is normal - or too much. After all "if you aren't measuring you are guessing" - as someone famous once said. But my little green meanie got its MOT today (as did my Ducati) - so at least the paperwork is in order, even if I am not happy with the mechanicals ! Break out the wine !! There's a lot of talk these days about green transport. Well, I am ahead of the game, I already have green transport ... British racing green.
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