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Discussion Starter #1
Hi guys!

One question for track day users, which brake fluid do you use? For the moment I'm using Motul RBF600, but after some laps, I have my brake pedal like a "sponge.
 

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Use Dot 5.1 brake fluid -

It has a higher boiling point than dot 4 (which RBF600 fluid is). This will result in a prolonged stiffer feeling pedal. But not for long. I would go for steel braided lines as well. They wont expand like the stock ones will, so will again provide a better "stiff" pedal feel :)

Hope that helps
 

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Lord of JAE.....
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5,395 Posts
I'd use Dot5 silicone (tis what mine will be going soon), never needs changing, i.e. lifelong use, does not go spongy, repels water and is used by the US army, and a few racing teams. Used in conjunction with braided brake hoses, and decent pads/disks (I love my yellowstuff...), should be just fine.

Tom
 

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Lord of JAE.....
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It'll be more the hoses.... with the fluid contributing a bit...
 

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#MrGrumpy
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I'd use Dot5 silicone (tis what mine will be going soon), never needs changing, i.e. lifelong use, does not go spongy, repels water and is used by the US army, and a few racing teams.
What's the deal with Dot 5 - I've never seen it in use anywhere? Not sure I'd want to use it considering that the system is designed for Dot 4/5.1 without knowing more!

Use Dot 5.1 brake fluid -

It has a higher boiling point than dot 4 (which RBF600 fluid is).
Inexplicably, RBF600 outperforms the DOT 5.1 standards for boiling points. I don't know what other factors mean it is still only DOT 4; but it's not that!
 

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#MrGrumpy
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Just been reading about it.

It doesn't absorb water so any water in the system will pool together (unlike DOT 4/5.1 which has inhibitors and changes colour with water content). It's more compressible so will lead to a spongy feeling more quickly I would imagine. It also aerates easily meaning its much easier to get air trapped in the system.

All of which mean very regular fluid changes.

It's also corrosive to silicone rubber seals around the caliper pistons, and it also is incompatible with mechanical ABS systems in many cases.

Meaning I'd just steer clear.


However, if you can regularly maintain the braking system and change the fluid regularly it might be suitable - racing use only by the looks of it as that's what it was originally developed for.

Edit: Apparently it's also very bad to change from one to the other without thoroughly replacing/cleaning the system as otherwise blockages can occur...
 

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Lord of JAE.....
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Hmmm my friend told me to use it, Honda (runs an RX-7 with heavily modified turbo setup) uses silicone racing fluid with absolutely no problems, he recommended it.... :) Not read of any other problems either, and it is a total non change fluid, it's a whole of life product as long as your system is drain thoroughly and checked as normal it will imho outperform ordinary fluid easily.

Edit: Been checking the aeration problem can be solved by letting the fluid sit for an hour before use and pouring gently, however it does require changes unlike I was informed, but the gaps are for more infrequent. The corrosion problem is the biggest problem, but it's pros do seem to outweigh the cons..... I withdraw my approval of dot 5 if your not happy to maintain it as highly, tbh I'd be happy maintaining it, but most won't be...... I'd go dot 4 and braided lines therefore.
 

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#MrGrumpy
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Hmmm my friend told me to use it, Honda (runs an RX-7 with heavily modified turbo setup) uses silicone racing fluid with absolutely no problems, he recommended it.... :) Not read of any other problems either, and it is a total non change fluid, it's a whole of life product as long as your system is drain thoroughly and checked as normal it will imho outperform ordinary fluid easily.
I agree that it won't "go bad" like glycol based fluids due to not absorbing atmospheric water, but I can't personally see a reason to use DOT 5. However if you are, and have no issues - then can't see a reason why you shouldn't! [smilie=gt-happyup.:
 

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#MrGrumpy
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Edit: Been checking the aeration problem can be solved by letting the fluid sit for an hour before use and pouring gently, however it does require changes unlike I was informed, but the gaps are for more infrequent. The corrosion problem is the biggest problem, but it's pros do seem to outweigh the cons.....
I think my biggest concern about that would be the chances of it getting aerated over rough roads whilst in use - apparently it doesn't take much!
Just requires draining the calipers every now and again to remove any pooled water from what I can read.

Considering that I've had no issues with DOT4/5.1 I think it might be a case of better the devil I know ;)
 

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Lord of JAE.....
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I agree that it won't "go bad" like glycol based fluids due to not absorbing atmospheric water, but I can't personally see a reason to use DOT 5. However if you are, and have no issues - then can't see a reason why you shouldn't! [smilie=gt-happyup.:[/quote]

Thanks :) Tbh I'll probabyl be changing mine when I change my lines etc. but it is highest maintenance..... although Harley use it as OEM and some supercars do too (almost a requirement with ceramic brakes....).

I would however say read my caveat, as tbh it's probably too high a maintenance for everyday users and those who want plug and play, decent 4.1 fluid and braided hoses should suffice... It has it's own pros and cons, tbh they are fairly equal, but the 4.1 is better for ordinary drivers and silicone/dot5 better for racers and certain braking systems....

Tom
 

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Discussion Starter #17
I have Goodridge braided lines, Pagid RS29 pads and Pagid discs. I think I will try Castrol SRF, I bit expansive but I read it's the best brake fluid we can find.
 
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