Idiot's guide to brakes

**pzorb** · Thursday 9th March 2006, 16:08

I'm sorting out my brakes this friday, but I need a few pointers before I start! I'm replacing the fluid, pads and discs at the front (rears are fine).

1. I'm going from DOT 4 to 5.1, so I need to flush all the old stuff out first. Presumably I don't want 4 and 5.1 in the rear and front circuits, so I need to drain the *entire* system. I'm clueless on this step, any pointers very welcome!

2. When putting the pads back on, will just normal pliers do for pushing the piston back in on the inside pad?

3. Should I change the pads and discs and then refill and bleed (to flush), or in some other order?

4. I'm bleeding using on of those reserve air pressure kits, any tips?

Big thanks to Wobbly Dave and bobcat for their guides on brake changing that I'll be printing out tomorrow!

Many thanks! Before this I've only ever changed the brakes on my bicycle lol so seriously any advice is appreciated

Ovlov

**mraldonnelly** · Thursday 9th March 2006, 17:05

Originally Posted by pzorb

I'm sorting out my brakes this friday, but I need a few pointers before I start! I'm replacing the fluid, pads and discs at the front (rears are fine).

1. I'm going from DOT 4 to 5.1, so I need to flush all the old stuff out first. Presumably I don't want 4 and 5.1 in the rear and front circuits, so I need to drain the *entire* system. I'm clueless on this step, any pointers very welcome!

2. When putting the pads back on, will just normal pliers do for pushing the piston back in on the inside pad?

3. Should I change the pads and discs and then refill and bleed (to flush), or in some other order?

4. I'm bleeding using on of those reserve air pressure kits, any tips?

Big thanks to Wobbly Dave and bobcat for their guides on brake changing that I'll be printing out tomorrow!

Many thanks!!!! Before this I've only ever changed the brakes on my bicycle lol

Hi pzorb,

1. Mixing 4 and 5.1 isn't an issue. Mixing 4 and 5 is. Therefore it's not essential to flush out the entire system but it is obviously preferable so that you have fresh fluid throughout the entire system.

2. Be very careful not to damage the piston or rubber dust boot. Pliers probably won't open wide enough so you'd have to use a pipe wrench or something similar with a wide opening jaw.

3. Replace the pads and discs and then lush the system. I think you start at the back left wheel, then to the back right wheel then to the front in any order. Refer to Haynes to confirm this though.

4. The kits make it mega easy to bleed the system. The only tip I can think of is to make sure the pressure isn't too high. A few PSI is enough. Too much pressure and at best the seal between the kit and reservoir will leak.

Good luck

Regards

Andy

P.S. DOn't forget to get a 7mm hex key for the caliper pins. Most kits don't include a 7mm key.

**racer** · Thursday 9th March 2006, 17:13

All of the above and clean and re-grease your caliper pins whilst they are off.

**pzorb** · Thursday 9th March 2006, 18:03

Thanks for the help Andy and racer, by pipe wrench we're talking about:

?

I don't have much with me, so tomorrow I need to buy anything that will do the job. Halfords want £20 for their tool(!) Has anyone used a mini clamp for this, and if so which size? How much of an opening does it require, and what diameter should the end have to push the piston?

I basically need something to push back that piston without spending the earth.

Keep it coming, if I can do this job trust me *anyone* can. I really appreciate the help, I've wanted to do this job myself for a while now.

**siamblue** · Thursday 9th March 2006, 18:11

Originally Posted by pzorb

Thanks for the help Andy and racer, by pipe wrench we're talking about:

?

I don't have much with me, so tomorrow I need to buy anything that will do the job. Halfords want £20 for their tool(!) Has anyone used a mini clamp for this, and if so which size? How much of an opening does it require, and what diameter should the end have to push the piston?

I basically need something to push back that piston without spending the earth.

Keep it coming, if I can do this job trust me *anyone* can. I really appreciate the help, I've wanted to do this job myself for a while now.

I bought a 3" clamp and it was too small, so ended up using a small gemmy bar, with the rounded crook end,

Gary.

**pzorb** · Thursday 9th March 2006, 18:53

Originally Posted by siamblue

ended up using a small gemmy bar, with the rounded crook end

Cheers Gary. This might sound stupid, but what's a 'gemmy bar'?

**siamblue** · Thursday 9th March 2006, 18:58

Originally Posted by pzorb

Cheers Gary. This might sound stupid, but what's a 'gemmy bar'?

crow bar,

**pzorb** · Thursday 9th March 2006, 19:05

Ah ok. I don't have a crow bar to hand either lol. Can't I use the old pad to push against the piston?

Humour me here, I just want to be sure I know what I'm doing before I start

(what can I say, I work with mathematical proofs every day)

**mikej** · Thursday 9th March 2006, 20:01

This might sound stupid, but what's a 'gemmy bar'?

Bloody hell mate surely there is someone close that can give you a hand , i would just say take it to a garage but it ain't a difficult job and its the only way you'll learn lol.Come on gents must be someone close who can stand and watch and talk him through it

**nobananas** · Thursday 9th March 2006, 21:13

To be honest al you need to do to push the piston back into the caliper is wedge a screwdriver between the disc and the pad before you remove the calipers and lever against it which will press the piston back into the caliper. As you are replacing the discs and pads anyway damage won't be a issue. I changed my 850 to 5.1 a while ago and found the easiest way was to first suck out all the fluid from the resevoir using a syringe (or as I do an old turkey baister !), refill with fresh fluid then bleed each caliper in turn topping up the fluid as you go.

**nobananas** · Thursday 9th March 2006, 21:24

Oh, one other thing, if you're changing the discs you will have to remove the caliper carriers as well which I think are held on with 15mm bolts, remember to use thread-lock on them on re-assembly.

**mikej** · Thursday 9th March 2006, 21:36

Pzorb on a serious note mate you should not have to buy anything really to send the pistons back if you do then they are proberly sticking anyway and need sorting.Like already mentioned if you are changing disks and pads then use a large screwdriver or anything you can fit between old disk and pad and force it back prior to removing caliper it may creep back slightly before you fit your new ones but just use the old pad again However i would recommend you use a 7mm hex in a socket and i think a 15mm on a long wrench/bar as the caliper mountings can be tight.Personally i would always change the pad/disks before bleeding but that is my own preference .Finally be careful when forcing pistons back you dont push the brake fluid out of the master cylinder ie keep an eye on the level during the job and dont connect your easy bleed up before you have changed the pads or you'll never get the bloody pistons back.

**pzorb** · Friday 10th March 2006, 00:32

Thank you Gary, mikej and nobananas - I'll have a crack at it this morning. Finger's crossed

**pzorb** · Friday 10th March 2006, 21:00

Right got everything stripped off today, no problems at all. Would have put the new stuff back on, but I'm certianly needing new lines at the front.
Now I know that brakes lines are a serious pain in the ass getting the unions to come undone, and I'm prepared to have to cut and reflare them if I need to. I'm going to douse the connections for the next few days with WD40 in the hope of freeing them up and getting lucky.
Question is, when I eventually do get seperation (be it luck or cut) will the brake fluid stream out and need catching or will the vacuum pressure in the master cylinder keep it in? (I don't want to get too much air in there incase I kill the ABS).

Can someone tell me what I should expect given I get the lines to come off?

Many thanks!

**iGGy** · Friday 10th March 2006, 21:12

If you can keep as good seal on the reservoir top as possible, then this will lead to probably a very slow drip. I think that's as good as you can expect.

Minimizing the flexing and vibrations of the open line will also help in retaining the fluid.

**racer** · Friday 10th March 2006, 23:29

Ye fluid is going to dribble out. There are various things you can do to slow it down (cling film and rubber band seal over the reservoir for example), but it will get out.

If you are going to change the front hoses, get the two sizes of brake pipe spanner required to undo the unions. If you have these, your chances of getting the unions undone increase dramatically.

Oh, and when your fitting the new ones, fit the pipe to the caliper before you put the caliper back on. Much easier!

**Wobbly Dave** · Saturday 11th March 2006, 01:19

I found that the plastic G clamps with the trigger type action or big water pliers are best for retraction of calipers

**pzorb** · Saturday 11th March 2006, 11:25

Originally Posted by racer

If you are going to change the front hoses, get the two sizes of brake pipe spanner required to undo the unions. If you have these, your chances of getting the unions undone increase dramatically

Cheers racer, I will do; does anyone knows what sizes these are? I've measured 14mm at both ends of the line, but I'm double checking as I've heard some people talk about 13mm (and 11mm but surely not). I don't want to buy a 14mm to find that it's actually a 13mm end with 1mm of crap stuck to it.

**racer** · Saturday 11th March 2006, 21:22

I can tell you tomorrow evening, after I've had the car and my brake spanners in the same place at the same time. Sorry I can't remember off the top of my head. I think it's 13mm and 11mm for those inboard unions that cause so much grief, but I'll check tomorrow.