Bleeding brakes

[Morris]

[Splat]

Yup. That’s the one.

[Westfield 129]

I use a $45 pressure bleeder from "Motive Power" to bleed the brakes. This quickly bleeds the brakes, removes all the air form the lines using air pressure at the reservoir to force fluid through the individual lines. It never misses, doesn't require any pumping and does a perfect job, single handed, every F'n time. I also have a Vacula vacuum bleeder, that also does a good job, and I still use it, but for the 11, and just about any other car, the Motive Power bleeder is best. It also makes flushing the brake system easy, but remember to keep the reservoir topped (though the system will auto fill the reservoir if so desired).

But... For years, I had a problem with inconsistent braking, using the standard single master cylinder. It was even keeping me from really enjoying the car in the canyons as I was always second guessing the brake response. And then... I read an article in one of the UK magazines that included an article about the Noble M400, which I was representing here in the US.
The article complained about the brake feel... "Like stepping on a dead animal, squishy with hard bits"... YES! That described my 11s brake problem precisely! I was thinking that there was a mismatch between the tandem master cylinder that the factory included with the kits, replacing the old style Girling single cylinder. So, what to do... I talked to the nice people down the road at Wilwood, the brake caliper and component manufacturer. They recommended a new pedal quadrant, but that didn't make sense to me. So, I decided that the problem might be pad "knock back", the pads being hammered back into the caliper by disc runout. I measured the runout at the rotors, but didn't find anything unusual. Still, THAT had to be the problem.

I replaced the ball wheel bearings with a $180 set of Timken tapered wheel bearings, with the shims to properly adjust the hub torque (yes, they are torqued into position, and not torqued by "feel"). PROBLEM SOLVED. What I got immediately was stable, predictable braking, with a solid pedal every time.
Then, I went to one of my friend's cars with the same silly brake feel problem, with the tandem master installed. I installed the taper wheel bearings, and again, perfection. The ball bearings don't hold their tolerances well, and after a couple of hundred miles, the runout returns. Maybe this is OK on a Spridget, but on the W11, well... Not so good.

If you want to get a good brake bleed, every time, get the Motive Power pressure bleeder (the standard European cap fits both the single and tandem master cylinders) and install a set of the Timken wheel bearings, and properly shim them. Speedwell Engineering in California has the kits. Worth every penny. I am sure that there must be someone in the UK that also has the same parts.

[Morris]

All interesting points, thank you Jan.

I'm beginning to think that my issue isn't related to air in the system so I'll be having a closer look once I've completed some other jobs.

I did try an 'Easybleed' type system, but after having the cap blow off the M/C a couple of times and causing a terrible mess I reverted back to the traditional pedal pushing method.

Hopefully once I get onto the road the feel should be ok as I've already fitted tapered roller bearings.

[Westfield 129]

You can also try a vacuum brake bleeder that attaches to the bleeder at the brake. The best are driven by your compressor. They also work quite well, though they appear to draw air bubbles into the bleed line. Not a problem, but it looks as though you are not bleeding the brakes fully. These bleeders are also useful for removing fluid from small reservoirs.

The best is still a pressure bleeder, and probably the least expensive way to single handed bleed brakes without pumping, and do a proper job.