Rear bakes were good when I had the fluid changed and new pads but now 3,000 miles later it’s pretty non existent. I’ve read that the cat boils the fluid so I plan to change it for racing spec. Do I need to spend £45 on Castro’s React or does Motul RBF660 for £13 work just as well
Bleeding is an easy enough process to repeat every now and then. Check the boiling point of the brake fluid and buy the highest dot 4 you can find
I was advised to use Motul 660 in my track bikes and was so impressed, I now use it in my road bikes as well. Andy
Bleed the brakes by removing the calliper and holding it above the seat . Any dot 4 brake fluid will work. There is a tread all about the poor rear brakes. Using this method takes the spongy feel and excess travel away for about 3000 miles.
Did the above a while back. Changed to Motul's highest rated fluid and removed the rear caliper and held it at its highest possible point and as I pumped the fluid, kept twisting the caliper to ensure all bubbles came out. Been brill ever since.
Castrol React and Motul 660 are similar enough as to make no difference in a road bike. The Motul bottle as priced however is only 500ml whereas Castrol’s is 1litre so you’ll need 2x the amount of Motul bottles but even still it’s a saving. You say you had the fluid & pads changed 3000 miles ago but you don’t say how long ago it was. Brake fluid is hygroscopic and thus attracts & holds individual water molecules within itself. Over time this reduces, dramatically, the effect of the brake fluid in its ability to be pressurised and thus force the pads against the disk. Hence the generally accepted practice is to change brake fluid every 24 months. Although Id do it annually on a high performance bike. How long ago was 3000 miles? Regardless of how long it was, if I were experiencing what you describe I’d bleed the brake system and make sure I got every last air bubble out, which takes time and patience. I’d use twice as much fluid as the system can hold to make sure the old stuff is fully flushed through and as @hill100 ssys above, any dot4 fluid will work ( you can get 5ltrs of it in Halfords for £20) and be as good as you’ll need unless you plan on using the bike on a track day, in which case use one of your 2 choices.
Found this, https://scanneranswers.com/best-brake-fluids-for-superior-stopping-and-braking-power/ which although I guess is a US based article, has some interesting basic information simply explained. Andy
I am perfectly happy with my Motul 600/660 fluid. The brake is still horrible in feel but it works. Even after almost two years.
Thanks Paul 3000 miles was early Sept 18 followed by a 2k blast around France and the Swiss alps. I shall go for 660 and spend time bleeding it thoroughly
