Brake caliper screws & wheel bearings

[xerxes]

Those instructions you link to are fine, but are given for a specific type of brake caliper which may not be the same as your vehicle's.

What vehicle are you working on? Designs can vary a lot.

The C clamp for compressing pistons only works if you have clearance to put the clamp in place. Otherwise you'll probably need a purpose-made tool.

In my experience, the L-shaped lever type works quite well within its limits: insert the blade of the tool, twist the handle to move the piston. The width of the blade limits the extent to which the piston will move. My tool is made by Girling; I'm not sure if they still list it.

Sykes Pickavant (and others) make a tool with two plates; one bears against the caliper, the other against the piston. Winding the handle turns a screw which forces the plates apart. If you have a stubborn piston, the plates can bend without the piston budging.

A better tool is an air-powered piston compressor; an air-powered ram is used to push the caliper piston. To use one of these you may need adaptors to fit your calipers. And of course you'll need an air compressor, so not really a recommended course of action if you're just starting.

Be aware that some pistons have to be turned while they are being pushed; for this, you will definitely need special tooling appropriate to your brakes.

One thing your on-line instructions don't mention is the need to loosen the bleed screw to allow fluid out directly. It's possible to damage ABS components if you don't do this properly. And of course, retighten and top up fluid levels when you've finished.

I recommend getting the Haynes Brake Manual which has fairly good coverage of a number of different braking systems, and plenty of sound general advice. After all, you want to be sure that you've done everything properly and that the brakes will work when you put the car back on the road.

 

[Hitachimad]

I wouldnt worry about a dead blow, your obviously on a budget, so a hammer and block of wood will suffice.

I would be looking at replacing pads/discs both sides, otherwise you may end up with a problem come MOT time.

 

[pretzelz]

mm, so much to consider. No wonder people just take their cars to the garage. There's a lot to learn about auto repairs.

My car is a little Daihatsu Cuore+ 850cc
http://www.caranddriving.com/pix/Udaihcuore.jpg

Shame the about.com guide missed out talking about the brake fluids but luckily I don't have ABS breaking. My car is so simple I'm surprised I'm not required to stick my foot out the door onto the ground to slow it down. "Everyone ready?"

Thank you for the advice about Pistons. I'll try a c-clamp first then other methods if there isn't clearance.

I've ordered most of the basic tools off ebay, so may now have to wait about a week before I can test things out. Although within the next few days I will have another go at the calliper nuts (they are tough to get off, as in my first post) before trying the impact wrench with reducer. And of course now I have to order new sockets too, as indeed I was using silver ones without realising.

Depending on the success I have with this, I'll for sure address both front wheels so I don't run into problems.

I'll upload a picture of my car sometime. It's got two sets of 10metre led lights drilled into it all around the underneith perimeter and interior.

 

[pretzelz]

>> loosen the bleed screw to allow fluid out directly. It's possible to damage ABS components if you don't do this properly. And of course, retighten and top up fluid levels when you've finished.


Which one is the bleed screw? And is it necessary if I don't have ABS breaking?

Today I got the calliper off! I hammered at the wrench to put pressure on the nuts and off they gradually came.

I've uploaded a picture of my brake disc and pads if anyone cares to evaluate the rust! -- Then I ran out of daylight so will continue from that point tomorrow hopefully.

http://www.wikiupload.com/download_page.php?id=84740 - image of my brake disc and pads.

By the way, of the two brake pad replacement articles I've read, neither specify that you should use grease on the back of the pads, yet other places on the internet mention it. Why have they missed out two things important? (draining brake fluid and pad grease)

Thanks.

 

[pretzelz]

-Can I also just check something. I am supposed to insert the new brake pads into the calliper BEFORE compressing the piston? Isn't the aim to compress the piston first, so that you have enough room to put in the new pads?

On this picture here from the about.com guide, the guy is compressing the piston without any pads in there, or is that just to demonstrate?

http://z.about.com/d/autorepair/1/0/M/-/-/-/brkpads-clamp.jpg

 

[Stivino]

You'll need to press the piston back before the pads will go in.
You might only need to remove the bottom bolt from the caliper. Sometimes the caliper will swing up out of the way with the top bolt in place.
If you get one pad out, you'll probably be able to push the piston back in with a flat lever or big screwdriver.

 

[xerxes]

To judge from the rust pattern, it looks as if the car has been standing for a while.

It's probably better to slacken off the bleed screw in any case. If you're working on the brakes, you must be able to locate it, on the back of each caliper. Clean the area around it, take off the dust cap and use a well-fitting ring spanner to slacken it off. Use a tube and a container to catch the corrosive brake fluid; dispose of it safely.

Yes, you must compress the pistons to make room for the much thicker replacement pads. Use copper grease on the backs of the pads to reduce/prevent squealing, and a thin smear on the edges so that they slide in the caliper properly. Don't get any grease on the friction material.

When you've reassembled everything, you must pump the brake pedal until the pads are seated properly. If necessary, bleed the brakes. Don't drive it until you're sure that the brakes are working correctly.

Why are the instructions you've read incomplete? Because nothing you ever read on the internet is necessarily complete or reliable. (That includes this post.) Get a decent manual and read it carefully.

 

[pretzelz]

Thanks Stivino and Xerxes for your insight. I'll look into these points. Also I've found the service guide available to buy on a website for £15. Unfortunately they send it on a CD rather than a download, but I guess it will be of some use.

 

[pretzelz]

Hi, whilst I'm waiting for my car service manual to arrive, could someone look at this picture of my calliper piston and let me know if I should g-clamp onto it to push it in? It's hollow and doesn't look like its even out very far. The old pads have been removed but normally grip inside it.

Thanks.

Piston picture:
http://www.wikiupload.com/download_page.php?id=85324

 

[Stivino]

First of all I'd put it back on and, put one pad in and try to lever it back with a flat tyre lever or big screwdriver. If I had to use a G clamp to push a piston back in, then the piston would probably be seized. And I wouldn't put the clamp inside the piston as it shows in the picture. I'd put an old pad on it and put the clamp on that. But as I said, if I had to use a G clamp then I'd be more inclined to fit a new caliper.

 

[tommydickfinger]

hi pretz, i cant help but think im reading loads of **** to confuse you and make your life hard work, youve made some valid posts about levering the piston back- can you get any one to help you that has any underpinning knowledge about brakes??? i dont think any1 in the world has undone bleed nipples to change the pads- my advice dude is jus get stuck in- it'll sort itself if you persist- then afterwards you'll be wandering y you took so much time reading all this thread for a real easy task!!! it looks like youve removed the pad carrier aswell-only do this if youre changing the discs, unless they feel like a vinyl recored when you run youre finger across, or theyres a massive lip then dont bother. with the bottom bolt removed only, prize the piston back with large screwdriver or prybar, cock the caliper over, you'll be checking the slides move at this point- the things the bolts go thru and screw into the carrier. clean the carrier of crap where the pads sit, place new pads in, bolt back up, repeat other side, pump the peddle out without it going to the floor, them check reservoir, and your ready to roll. a conversant chap with decent tools would crack this with ease in 30 mins- if youre on youre gravel drive, with chocolate spanners and checking and rechecking just to make sure youve cocked up- then look at 90 mins-but it would pay to have a mate theyre to make sure you dont snap anything 1st time round
kind regards

 

[xerxes]

For the benefit of the OP, or anyone else reading this, how does running your finger across a disc check:


- that the disc thickness is still within tolerance

- that the disc runout is within the allowed limits

- that it is free from cracks?

 

[pretzelz]

Thanks Tommy for your post : ) It's good to hear everyone's insight. The fact at the moment is, this job is taking way more than 90 minutes. Firstly because I didn't even know much about sockets and nuts before I started out on this task, so my progress has been real slow, and I've had to order each new tool bit everytime I've realised I need it. For example, yesterday I ordered a 14mm Impact Socket because I figured it would do a better job getting the nuts off my rotor than I could by hand.

Also I think probably many car's differ in how they are assembled, so I'm waiting on the service manual to arrive for my car too, then I can (hopefully) be sure of how to go about certain things. For instance, on my car, the brake pads are clamped into the piston and the whole caliper is one assembly. There's nothing else seperate that stays on the wheel for the pads to slide in and out of. It's a very cheap car so they probably cut corners where possible.

I'm know at the end of this once I've followed all the procedures and learnt my lessons, and aquired the right tools, I'll be able to look back on it and repeat future auto-changes quickly and direclty. For now though I'm sure I'll have many more questions pop up.

My latest question for example is -- when I simply take a wheel off the hub, just how freely-rotating should the hub be? When I try to turn my wheel (with caliper still assembled etc) it seems quite stiff to rotate it, and that's with the brake pedal not down. Is this because the handbrake is on? Or is my old brake set just too clamped in already for some reason? If so is it always like that when I've been driving? Fuel economy must have been very impared.

Many thanks.

 

[Stivino]

It's nothing to do with the handbrake because in the main handbrakes only work on the rear wheel. Your disc looks a bit rusty and brake pads always make a little contact with the disc so that'll be why it's a bit stiff.

 

[^neo^]

id be wondering why the disc has a rusty patch on it if i was standing in front of that.
Looks to me like the disc could be warped.