How much brake fluid?

[blow_away]

My first experience with radial brakes.

My new (to me) track bike is a ZX636 C1H (2005). I rode it at Mallory a few weeks back and it suffered from brake fade. So I checked and deglazed the pads, cleaned up the calipers, drained the old fluid and replaced it with Motul DOT 5.1. It already has HEL lines. So far so god, job all done, lever feels fine and I'm packing away the tools when I notice that I only seem to have used about 150ml max brake fluid. I'll probably bleed them through again after running the bike, but I can't quite escape the feeling that I haven't used much fluid?

So does anyone know what the capacity of a brake system is? Roughly? There can't be much of the lines, but I have no idea how much fluid there would be in the calipers themselves. Looking at the pictures in the manual, the calipers seem to be mostly piston area, despite their chunky feel.

Obviously I'm not that bothered as the job went quite smoothly, just curious Next time I'll buy 500ml of brake fluid instead of a litre

[budda]

All i can tell you mate is that good quality dot 4 is better than 5.1, unless you refresh it very regularly I'd say every 2 months or so.

And from experience the dot 5.1 goes off in the tub........Bummer I know!!!

[lorenzo]

How big's the reservoir on your bike? 150ml sounds like shit loads to me, I bet the reservoir can't be much bigger than that.

Your calipers capacity will be hugely dependant on if the pistons are pumped out or not. How much wear have you put on the pads, I bet most of the meat on a pair of pads would get you 100ml or so from the reservoir to the calipers.

[blow_away]

Its a standard reservior Loz, I would guess it holds more than 50ml but less than 100ml. Not full right up, but to halfway between the upper and lower marks.

It might just be a problem of perception - I drained the whole system so I was expecting to use more fluid

[Tomfoolery]

I generally use a standard bathtub full.

[lorenzo]

I actually misread the entire first post. I thought that what you were saying is that since you refilled it you've used up 150ml, which sounded very fishy, ie you'd boiled off a whole systems worth. Yep, to have refilled a system from dry and having used 150ml is about right if you've not used a shit load of it just flushing it through.

[Gary]

I think you are okay, each time I replace my systems brake fluid I use less than 150ml of brake fluid, a lot depends on the tools you use and how much fluid ends up on the floor and paintwork , but if you do the job cleanly and correctly, 150ml is a good figure. I buy 250ml bottles and replace the front and rear brake fluid and have plenty left for top up over the year. When changing the fluid, be sure to force all the pistons into the callipers as much as possible so you don't have loads of old fluid sitting inside the caliper, as it often doesn't get flushed out when you pump new fluid through the system, get a small vaccum pump to pull the new fluid from the reservoir down to the caliper. It's much quicker and easier than trying to prime the system and pumping fluid with the master cylinder.