Braking It Off Polite

Many years ago I once read something funny in Easyriders. Genuinely amusing it was too, not your usual low-brow-thick-as-two-short-planks-bum-and-fart jokes but a witty and intelligent piece on social relations between the sexes. If I remember correctly it was written by one J.J. Solari (who also, I am told, made an appearance playing the part of "hitch-hiker no.3" in the movie "Two-Lane Blacktop", trivia lovers).

A brake caliper yesterday

This twin piston Honda caliper slides on these two bolts. You should be able to feel a little sideways movement with the brake off, if not you'll need to remove the caliper to service the sliding bits.

The thrust of Solari's piece was this; life goes much easier for all concerned when an unsuccessful relationship is wound up with care, tact and consideration. It was called "Breaking It Off Polite", and consisted of a number of bullet points to be used as an etiquette guide when things have reached that inevitable stage of relationship termination. Item one read; "bring the bike to a halt". Good advice; if you ditch her in the middle of the desert somewhere miles from anywhere, her chances of survival are much improved if she suffers no broken bones during the initial spilt. It's only polite. Solari went on to advise that it constituted good etiquette to indicate the rough direction and distance to the nearest town before roaring off in a cloud of dust, and if the relationship had been a particularly good one you might even leave her a knife so she could hunt for food.

As we aren't in the business of relationship counselling here at bikerworld I don't propose to dwell too much on Solari's other points, but the ability to bring your bike to a halt may be useful under a number of circumstances, even if you're happily married.

The lower sliding mount is a steel tube which fits through this lug on the caliper body. Make sure it slides freely and lubricate it well with Copper Slip before re-fitting the rubber boots. These must be in good condition and not split.

The upper sliding pin engages in this hole. Smear the pin with Copper Slip before fitting and make sure this rubber boot is in good nick to keep the Copper Slip in and road filth out. Never be tempted to use ordinary grease here as it will melt from the high temperatures under heavy braking, and could get onto the pads.

Hydraulic disc brakes have been around long enough for the manufacturers to have sorted out all the research and development work that made riders of the late sixties/early seventies such human guinea pigs. Early motorcycle disc brakes were pretty crude affairs that seized up regularly and didn't work in the rain. The modern brake caliper is, by comparison, a sophisticated and effective gadget, but might still need a little TLC to keep in top order.

The principle is simple enough; the disc (or "rotor" to our colonial cousins) bolts to the wheel and rotates with it. Squeeze the brake pads against the disc and your bike slows down. The job of the caliper is to hold the pads and squeeze them together when required. Sounds simple eh? Let's complicate it then...

With the sliding bolts removed, pull the caliper away from the disc and release the pads by first removing this lockplate...

...which will then allow you to pull out the two retaining pins and remove the pads. This caliper, helpfully, is fitted with stainless pins which come out relatively easily. Ordinary steel pins frequently seize in place and can require serious persuasion to shift. (Top tip for Superdream owners; you can split the caliper body and slide the pads off the pins when they're corroded in.)

First off any self respecting brake caliper these days is hydraulic, which means it has brake fluid inside it. The brake fluid is fed down a hose from the master cylinder on your right handlebar. Squeezing the brake lever shifts fluid in the hose, and forces pistons outwards from the caliper body toward the disc, squeezing the brake pads against it. How many pistons you have depends on the sophistication of the design, but it's convenient to divide hydraulic calipers into two types. First, an opposed piston caliper will have pistons either side of the disc. Squeezing the brake lever makes them both move. You'll find this type of caliper on lots of old Brits. It can work very well, but tends toward the big and heavy.

Lighter and more modern calipers will have their pistons on one side only, and achieve their required task of squeezing both pads together by allowing the caliper body to move sideways when the brake is applied. This type of design is known as a floating caliper and is likely to be what most of us will have these days. The opposed piston caliper isn't dead and gone yet though, and you'll still find them on the back of some modern Jap bikes.

The pistons in all their cacked-up glory. Watch for pitting on the pistons and be prepared to budget for replacements on high mileage bikes. Fortunately these just needed a clean up. If you're planning a complete caliper strip, this is the time to pump out the pistons. Otherwise don't touch that brake lever!

When fitting new pads you'll need to push the pistons fully home to make room for the thicker pads. I used a good, solid British Made G-Clamp for this job. You may need to remove the master cylinder cap to make this part of the job easier and be careful as the fluid level in the cylinder could rise high enough to spill onto your tank and damage your paint.