Author Topic: Front brake caliper rebuild. (Read 17176 times)

tex1507 · « **on:** 25 October 2011, 12:07:42 am »

Ok i stripped my front brakes down to clean them as i have been getting a squeal from the front from starting about 40ish, when i noticed that on both sides i am getting uneven pad wear.

So have ordered some replacement seals of the internet and i am going to attemp to strip and replace all the relevant seals on both brake calipers, soooooo i have been reading my haynes manual and was wondering if anyone had any hints / tips that they found helped when do their brakes.

Reason for asking there is a small section that is a bit grey to me, basically the manual says to clamp a bit of wood over one side to prevent the pistons on one side from moving, then to apply pressure to the brake lever until the oter side "pop" out, it then says to remove the seals and replace the pistons, clamp the wood on this side and repeat to get the other pistons out.

the grey area for me is once i get the first set of pistons out what stops air getting back into the system........and yes i intend to replace the brake fluid with fresh stuff.

Cheers

Stu

griff86 · « **Reply #1 on:** 25 October 2011, 07:41:00 am »

Alrite Stu.
Like you've worked out, there isn't a way to stop air getting in the system after taking one of the pistons out.
I did mine by taking off the calipers and using a footpump to push each piston out. I cut an old inner tube valve out and sealed it into where you screw the banjo bolt, you can use compressed air if your carefull because the pistons do seem to shoot out at 100mph!
Take your time with it, clean out all the grooves where the seals sit and red rubber grease the pistons when you put them back in.
Simon

Deefer666 · « **Reply #2 on:** 25 October 2011, 08:16:58 am »

I use a compressor with a blow gun with a section of rubber tube on the nozzle to form a seal but if that fails I use one of these:

Kenny Dave · « **Reply #3 on:** 25 October 2011, 06:38:24 pm »

You can take one side out, clean the stuff in there, put them back in and then pop the other side and clean under there.

Or, if you use clamps to get both sides of the piston near the middle, then you can usually get one side out then just jiggle the other side with your fingers to get all out at once. If they are very stiff then that won't work.

Gnasher · « **Reply #4 on:** 26 October 2011, 03:34:28 pm »

Quote from: Deefer666 on 25 October 2011, 08:16:58 am

I use a compressor with a blow gun with a section of rubber tube on the nozzle to form a seal but if that fails I use one of these:

Thats the way to do it.

DryRob · « **Reply #5 on:** 26 October 2011, 05:34:44 pm »

Quote from: Deefer666 on 25 October 2011, 08:16:58 am

I use a compressor with a blow gun with a section of rubber tube on the nozzle to form a seal but if that fails I use one of these:

I used a pair of these and they were great until I got to the seized pots. Don't be tempted to do what I did and use mole grips, they make a right mess of the caliper pots. Looking back I should have pushed the pots out as far as possible using clamps and wood before I took the caliper off the brake line (was replacing them at the time). I don't know if they're cheap/common but conventional pliers with gripping faces made of a softer metal might help if this happens to you.

tex1507 · « **Reply #6 on:** 27 October 2011, 09:01:17 pm »

Quote from: Kenny Dave on 25 October 2011, 06:38:24 pm

You can take one side out, clean the stuff in there, put them back in and then pop the other side and clean under there.

Or, if you use clamps to get both sides of the piston near the middle, then you can usually get one side out then just jiggle the other side with your fingers to get all out at once. If they are very stiff then that won't work.

Excuse me for being thick but what are these? they look like some sort of reverse pliers that whould clamp on the inside of the piston.............if i am right where would i get something like this?

oh and is it an easy enough job to replace the seals or is it a right git

Fazerider · « **Reply #7 on:** 27 October 2011, 09:47:05 pm »

Could have done with a pair of those today... in the end a set of circlip pliers did the job (just).
Toolbox.co.uk have a nice looking pair made by Sealey for £16.35, cheaper Draper ones are also listed.

tex1507 · « **Reply #8 on:** 29 October 2011, 10:31:12 pm »

ooooooook pliers ordered, planning on clamping the brake pipe when they come and taking the caliper to pieces on my work bench
as the pistons aren't seized i guess they will come out ok with the pliers, going to repeat that on the otherside once that is done
going to get both calipers back on the bike and then change the brake fluid (after removing the clamps).

His Dudeness · « **Reply #9 on:** 29 October 2011, 11:36:54 pm »

i'd clamp one side and pump the other side out nearly all the way. then swap the clamp over to the side that is nearly out and pump the other side out. then just pull out the side thats left

Fazerider · « **Reply #10 on:** 30 October 2011, 12:27:01 am »

Never liked the idea of clamping the brake lines.. seems like it can't do them much good. Instead, I wrap a big elastic band round the brake lever and grip (closes off the flow through the master cylinder).
The outer dust seals on the calipers can be picked out easily with a fingernail. The main seal is a bit trickier as it's deeper in the cylinder and much thicker, you can lever it out with a small jeweller's screwdriver, but take care not to damage the outer face of the slot the ring is seated in. If you've a suitable bit of steel wire about a millimetre in diameter then flatten and bend the tip you can hook the ring out from the back. Diagram might make the idea clearer:

limax2 · « **Reply #11 on:** 30 October 2011, 08:39:45 am »

Nice diagram Fazerider

.

jumpnut · « **Reply #12 on:** 02 November 2011, 01:02:24 am »

sorry to hijack but is it not possible to split the caliper in any way? Last I looked it seemed almost like you need some sort of magical yamaha tool to fit inside the bluespots on the outside.

limax2 · « **Reply #13 on:** 02 November 2011, 08:32:28 pm »

Quote from: jumpnut on 02 November 2011, 01:02:24 am

sorry to hijack but is it not possible to split the caliper in any way? Last I looked it seemed almost like you need some sort of magical yamaha tool to fit inside the bluespots on the outside.

A year or so ago on here some well respected guy said on no account try to remove those blue plug things. I can't remember why not but I wouldn't try it if I were you. (If you do please let us know the result

)
You can split the rear caliper but unfortunately Yamaha don't sell a replacement seal that goes between the two halves. However from this site I believe a Suzuki seal part no. 6910734200 does the job. Never used it myself.

Deefer666 · « **Reply #14 on:** 03 November 2011, 07:17:29 am »

DO NOT attempt to remove the blue plug! They are bonded in and if you take them out then the caliper is effectively fucked. The tools should not be availabe to the public and are a wase of money.

oldmotherfoccer · « **Reply #15 on:** 03 November 2011, 07:53:18 am »

clamping brake lines - OMFG - just remind me never to have you work on my bike

tex1507 · « **Reply #16 on:** 03 November 2011, 09:47:05 pm »

clamping the brake line was what i used to do on cars and as the material looked similar i thought i could used
the brake hose clamps i have

oldmotherfoccer · « **Reply #17 on:** 06 November 2011, 12:26:06 pm »

cars and bike - big difference - and if you get it wrong with a car at least you have a seat belt and the car as protection when it goes wrong. always amazes me that people will play with brakes - play with the exhaust, lights, paint whatever - but to play with the brakes when you dont know 110% what you are doing, would seem to be one of the reasons why the EU might be looking to change the rules lol

Slimted · « **Reply #18 on:** 06 November 2011, 08:06:35 pm »

I replaced all the seals on my front calipers last year. Dont save a couple of quid by getting pattern parts. I had a mare and ended up buying a set of genuine Yamaha seals. The pattern ones did not seem to fit correctly, maybe inferior rubber.....

deenybean · « **Reply #19 on:** 13 November 2011, 04:46:21 pm »

I have a similair problem to those mentioned here. I replaced the piston seals on the front caliper after the bike failed it's MOT. The MOT tester said the brakes were binding and suggested replacing the seals. After doing that I bled the brakes following the instructions in the Haynes manual, but the brakes still feel spongy and I can pull the brake lever right back to the handle bar. Does anyone have any ideas what I've done wrong or suggestions for what else I can try?

I also noticed that when operating the brake lever once, the pistons don't all move equally, the small piston on one side of the caliper and the large piston on the other side moved out while the other two pistons hardly moved at all. Cause for concern?

Fazerider · « **Reply #20 on:** 13 November 2011, 05:20:08 pm »

Deenybean: With the caliper off, pump the lever until all 4 cylinders are as full as you dare get them (checking the level in the master cylinder as you're doing this, no point in pumping more air in!). If you don't have any fancy tools to limit the movement of the pistons, offcuts of wood or even a pair of old brake pads will act as suitable spacers.
Now tap the caliper gently to try to dislodge any stubborn little bubbles of air up towards the bleed nipple, loosen the nipple until you get no more air out then tighten it back up.
The next stage involves pushing the pistons back in, a couple of small G-clamps helps here, and the idea is to force the fluid back up the brake lines carrying any bubbles that have got stuck in the lines up to the reservoir. Have the top of the reservoir on loosely while you're doing this, a brisk flow is what you're aiming for and you don't want it squirting over the paintwork. If it's a bike with twin discs, turn the steering to the left to avoid getting air trapped in the assembly that splits the brake lines.
Mind the reservoir doesn't overflow as you shove the pistons back, let some more out of the bleed nipple if it's getting close to the top.
You might need to repeat the process for both sides, but it eventually gets the brakes good and firm.

His Dudeness · « **Reply #21 on:** 13 November 2011, 10:30:57 pm »

Quote from: deenybean on 13 November 2011, 04:46:21 pm

I have a similair problem to those mentioned here. I replaced the piston seals on the front caliper after the bike failed it's MOT. The MOT tester said the brakes were binding and suggested replacing the seals. After doing that I bled the brakes following the instructions in the Haynes manual, but the brakes still feel spongy and I can pull the brake lever right back to the handle bar. Does anyone have any ideas what I've done wrong or suggestions for what else I can try?

I also noticed that when operating the brake lever once, the pistons don't all move equally, the small piston on one side of the caliper and the large piston on the other side moved out while the other two pistons hardly moved at all. Cause for concern?

you can also try to bleed the brakes at the banjo bolts.

Deefer666 · « **Reply #22 on:** 14 November 2011, 09:16:17 am »

If the you have really stubborn calipers that refuse to bleed up either take the top off the reservoir and cable tie the lever back to the bar and leave over night.

or

remove the calipers and hang them so that they are above the master cylinder and then bleed them that way as the air bubbles will travel upwards naturally..... But this is normally a last resort.

born to be mild · « **Reply #23 on:** 14 November 2011, 04:26:45 pm »

You must have a lot of air in the system for the lever to go that far back, deenybean. are you sure that your master cylinder seals arent shot?

deenybean · « **Reply #24 on:** 20 November 2011, 09:38:28 pm »

Read all the coments from above, ref bleeding brakes... Changed seals, cleaned pistons,bleed the system,taped the calipers 2 get rid of stuburn trapped air bubbles, took calipers off & raised them above master cylinder & bleed them, but still have spungy brakes. now i have clamped brake lever open 2 leave over night, failing that. im going 2 scrap the f%$kin thing. well pissed off......