DIY: Disc jockey

Re­plac­ing your tow ve­hi­cle’s brake pads.

Motorhome & Caravan Trader - - Contents Issue 202 - Words Philip Lord

Re­plac­ing your tow ve­hi­cle’s brake pads

Disc brake pad re­place­ment is one of the eas­ier jobs to do on your tow ve­hi­cle (or car­a­van, if it’s equipped) and could save you money and the has­sle of pay­ing some­one else to do it for you.

The key thing be­fore you take on a job like this, though, is to de­cide whether or not you have the skills to do it. If you’ve never worked on your ve­hi­cle or van be­fore, it would be bet­ter to get a good me­chanic to do the job. Brakes are an im­por­tant safety item, so you don’t want to get it wrong when work­ing on them. If you do, you’ll also be li­able if things go pear­shaped on the road be­cause of your work.

This is a job that would ide­ally oc­cur with a brake fluid bleed and disc ro­tor thick­ness check (or ro­tor sur­face ma­chin­ing/re­place­ment) and, per­haps, greas­ing the slider pins (with brake grease).

You can tell if your disc pads are on their way out in a few ways. First, there’s the easy but not al­ways ac­cu­rate way – some cars have a low pad sen­sor that will il­lu­mi­nate a light on your dash to tell you the pads are ready to be re­placed. Oth­ers will squeal when the brakes are ap­plied, which tells you the fric­tion ma­te­rial is low. But the best way to tell is to have a look at them. You need to see on top (or un­der­neath) of the caliper to see how much fric­tion ma­te­rial is left. Some wheel de­signs have thin enough spokes that you can have a peek through but, for most, you’re go­ing to have to take the wheel off to have a proper look. It de­pends on the ve­hi­cle, but when the fric­tion ma­te­rial gets to around 2-5mm, it’s time to fit new pads.

GET­TING TO WORK

To be sure about min­i­mum pad thick­ness and any re­move/re­place vari­a­tions for your ve­hi­cle, you’ll need to get a work­shop man­ual for your ve­hi­cle. You’ll need a wheel brace, a jack, axle stand, a screw driver, a torque wrench and a brake caliper pis­ton tool. Aside from new pads (you re­place them as a set for both rear wheels or both fronts to help avoid un­even brak­ing per­for­mance), you’ll also need brake fluid (again, check the specs for your ve­hi­cle but, for most ve­hi­cles, DOT 4 is okay), some wire (such as coat-hanger wire) and a sy­ringe. Op­tional items in­clude brake cleaner and, if you’re bleed­ing brakes, a brake bleeder kit.

First, get the sy­ringe and (as­sum­ing the brake fluid is up to the ‘max’ mark) re­move about half the fluid in the brake reser­voir. This is so that later, when the caliper pis­ton is pushed back in (push­ing brake fluid back up the line to the mas­ter cylin­der and reser­voir), the fluid doesn’t over­flow out of the reser­voir. Dis­pose of the old brake fluid in a con­tainer that you can later take for oil re­cy­cling (avail­able at refuse col­lec­tion cen­tres).

Then it’s time to re­lease ten­sion on the wheel nuts (or bolts, if so

equipped); half a turn is usu­ally enough. Then chock a wheel on the axle you’re not work­ing on and get your jack ready to go. Find the cor­rect jack­ing point (again, the work­shop or owner’s man­ual will have this in­for­ma­tion) and jack up the cor­ner of the car you’re work­ing on. Once the wheel has lifted off the ground, get an axle stand and place it un­der the ve­hi­cle un­der a se­cure point (again, re­fer to the work­shop/owner’s man­ual) and re­lease the jack so that the axle stand is tak­ing the weight. I pre­fer to keep the jack in place, tak­ing some of the weight as a back-up.

With the wheel re­moved, you can un­bolt the caliper from the caliper car­rier. Then re­move the caliper from the car­rier and se­cure it with wire in a po­si­tion so that you can work on it. Be care­ful not to let the caliper hang on the brake hose, or twist or bend the hose ex­ces­sively.

Re­move the old brake pads from the caliper (in some cases, though, the pads are con­tained by the caliper car­rier) and put aside. The pads shown here should have been re­placed long be­fore they were – you can see where the fric­tion ma­te­rial was com­pletely worn away on one cor­ner of a pad, leav­ing the back­ing plate ex­posed.

This pad, be­ing down to metal, would have scored the ro­tor and it will re­quire ma­chin­ing or re­place­ment (again, this should be done in pairs, not

just a sin­gle ro­tor). In fact, you should con­sider mea­sur­ing the width of the ro­tors (at the mat­ing sur­faces of the pad and ro­tor, not at the edge) to en­sure the ro­tors have not worn past their spec­i­fied range.

The pis­ton(s) within the caliper are de­signed to stay hard up against the back­ing plate of the pad as the pads wear. So the pis­ton has to be re­tracted into the caliper body when new pads are fit­ted. Some will re­tract with very lit­tle pres­sure (push­ing a brake pad against the pis­ton with your hands will be enough) while oth­ers will need a brake caliper pis­ton tool or sim­i­lar to push the pis­ton back. Some ve­hi­cles’ caliper pis­tons re­tract by screw­ing them in.

FIT­TING THE NEW PADS

Now the new pads can be fit­ted to the caliper, mak­ing sure you have them in the cor­rect ori­en­ta­tion (it can be easy enough with some pads to in­stall them up­side down) and that your hands are clean when you fit them (so you’re not trans­fer­ring grease on to the pad sur­faces) and now is the time to spray brake cleaner on the pads if you did ac­ci­dently mark the pad sur­faces with grease. It is also a good idea to spray the ro­tor on both sides and the caliper and caliper car­rier with brake cleaner while they’re apart. Brake cleaner re­moves de­posits and evap­o­rates quickly (and doesn’t need wash­ing or wip­ing off).

The caliper car­rier can now be re­leased from its se­cur­ing wire and mounted back on to the caliper car­rier and, once you have checked care­fully that it is mounted in the cor­rect po­si­tion, it can be bolted back on to the caliper car­rier to the spec­i­fied torque.

Now it’s time to re­fit the wheel and wheel nuts. Then lift the ve­hi­cle on the jack enough to re­move the axle stand and then wind down or re­lease the pres­sure within the jack. Re­move the jack and tighten the wheel nuts to the spec­i­fied torque (usu­ally around 110Nm for cars and 120-130Nm for car­a­vans, but you must check with the man­u­fac­turer).

Check around the work area to en­sure ev­ery­thing has been re­fit­ted cor­rectly and that all tools are re­moved from in and around the work area. Also check you don’t have any ‘spare’ parts ly­ing around ex­cept for the used brake pads.

Now you can top up the brake fluid reser­voir, as re­quired. Start the ve­hi­cle and move for­wards and back­wards at no more than walk­ing pace, and check brake pedal feel and lis­ten out for any un­usual sounds from the brake area. Fi­nally, take the ve­hi­cle or van for a test run and check the brakes work as they should – but do make sure you don’t have a ve­hi­cle be­hind you be­fore do­ing a brake stop­ping test!

4 3 Jack the ve­hi­cle up and sup­port it with a sup­port stand. First, re­move some fluid from the brake fluid re­serv­ior.

1 2 Some of the ba­sic needs for a brake pad change in­clude brake fluid, new pads and a sy­ringe. First, re­move some fluid from the brake fluid re­serv­ior.

5 Re­move the wheel nuts and then re­move the wheel.

6 7 Re­move the caliper re­tain­ing bolts. With the caliper sup­ported, un­clip and re­move the old brake pads.

9 8 Push the pis­ton back into the caliper to al­low clear­ance for the new pads. Here, you can see, on the top left, that the old pad was down to the back­ing plate metal. Pads should not get to this point be­fore re­place­ment.

10 Fit the new brake pads.

11 Op­tional, but al­ways a good idea – spray the caliper and disc lib­er­ally with brake cleaner. 12 Re­fit the caliper to the bracket and tighten the re­tain­ing bolts to the spec­i­fied torque. 13 After you re­fit the wheel and nuts, re­move the stand and jack and check wheel nut ten­sion, then top up the brake fluid once again.

Newspapers in English

Newspapers from Australia

© PressReader. All rights reserved.