Any Votes on best racing Brake Fluid.

I just ran across endless RF-650 versus Castrol SRF vs Motul 660. What do we think for this? I race mostly small bikes Honda NSF250R KTM RC390 Aprilia RS250 etc....

 

any good quality fluid should be fine for most bikes.. price out the SRF castrol before ya decide that's what ya want. it's really expensive and in most cases, not needed.

 

Castrol is amazing. I ran motul or similar and just changed it a little more often in bike and cars. Its still cheaper than SRF.

 

Castrol SRF looks expensive because it's only sold in 1 liter sizes.

Buy two Motul RBF660 500mL bottles and you're at the same price.

Given that the SRF wet boiling point is way better than anything else (120 degrees better than RBF660), it's a no brainer for me.

 

Castrol over all else. Expensive, yes, but worth it IMO.

 

SRF

 

SRF has a wet boiling point higher than a lot of other fluid's dry point at 270C / 518F. Im not strict enough with brake fluid changes to disregard the wet boiling point.

 

How much is a 250ml can of SRF? I use motorex dot 5.1 for the ktm dirty bike. 500f boiling point doesn't say wet or dry. 12 bucks for 250ml.

 

Castrol SRF is the stuff. Only fluid I run in my Duc that doesn't degrade right away. Also saved me from having to bleed the lines all the time. It is worth the $.

 

$60-70 for 1 liter. So you'll need to split it with friends if you only want 250ml.

 

I have a bottle of all three at home.
Haven't opened the Castrol yet.

I think the advantage of Castrol is the wet boiling is so high maybe change intervals can be extended???

Rather than being hygroscopic. I read it's hydrophobic.

I just used Endless last season but because of illnesses etc didn't make it to the track except once and wasn't working it too hard to tell if there was a difference.

I would occasionally get a little fade with motul previous seasons with hard abusive braking. Probably more an issue with poor mantainence rather than fluid quality.

 

No. DOT fluids are all hygroscopic.

While absorbing water does lower the boiling point, the worse scenario is the fluid is hydrophobic, and any pooled water boils at 100C/212F.

 

There are four-wheeled teams sponsored by a different big oil company, and yet, they buy SRF for use in their cars. Must be good stuff.

 

I was going to say I got Silkolene for free (and they made great stuff) but I bought 747 and Castro brake fluid.

well, I did get the Castrol for free also for awhile but I did buy it when I had to.

 

That's not entirely true as there are a whole class of DOT fluid that is hydrophobic. DOT 5 are silicone based and hydrophobic.

Castrol SAY SRF has silicone ester but completely miscible (sp?) with 3, 4 and 5.1. But not recommended.

I'm not sure what it has in it... I'm sure some proprietary blend that acts like a DOT 5 but chemically phyically reacts with water in such as way to be compatible with the other fluids.

One thing I have read is that like silicone based DOT fluids, the feel might be slightly softer as the fluid is somewhat compressible.

 

Well, there it is. A useful thread for me on the beeb. I have used RBF600 and then RBF660 for over a decade. I had some brake fade issues with RBF600 and switched to the 660 stuff, but I care about brake performance and feel above almost all else, so I’m going to switch to the Castrol. Thanks!

 

Compressible fluid you say, interesting. Change fluid often.

 

AP Racing Radi-Cal R4 and R2,

 

Fresh is best

 

Compressibility
Unlike mineral oil, silicone fluid exhibits extremely high compressibility and does not coagulate when pressurized. Silicone fluid has much higher compressibility than petroleum-based insulating oils or synthetic lubricants, and is thus well-suited for use as damper oil.