brake fluid

Random13 · Scooby Slapper Joined: 12 May 2013 Karma :

Hi,

Just seen my fluid level going down for the front brakes. it was on max not is is 3/4 or slightly below.

Looked around and no leak so is it pad wear pushing the calipers in ?

many thanks

pdg · World Chat Champion Joined: 15 Sep 2012 Karma :

No.

If the fluid was on max with new pads, it's more than likely that pistons are further out due to pad wear.......

Wink

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Taught2BCauti... · World Chat Champion Joined: 12 Jan 2012 Karma :

That sounds spooky!

You actually watched as the fluid level went down by 1/4?

I would guess that one of your piston seals has failed, and the fluid is being retained by the dust seal.

I would definitely not ride it again until you have it checked out.
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Random13 · Scooby Slapper Joined: 12 May 2013 Karma :

no , it wasn't as me seeing it go down rather suddenly notice. it could have happened over the past few or possibly weeks.

I rebuild both caliper and install it with new pads so maybe it is the pad wear. it has only done 2-3k

Fizzer Thou · World Chat Champion Joined: 06 Aug 2011 Karma :

If the new pads were a soft compound then they may well have worn out quite quickly.

Does the front wheel freely rotate and do quite a few rotations before stopping?
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Random13 · Scooby Slapper Joined: 12 May 2013 Karma :

yes but you can hear the scrubbing sound which i guess is due to rain ?

it was ebc sintered which I think do wear quickly but provide a good braking performance

Fizzer Thou · World Chat Champion Joined: 06 Aug 2011 Karma :

Why would you think that the pads wear more due to the rain?

If the pads are binding slightly when the discs are cold,then they will wear the pads quicker as they will not stop binding as you ride along.

I had this problem with the calipers on my Exup1000.But it was because the pistons were binding in the bores of the calipers that caused the problem.But I only found this problem after I had rebuilt the calipers with new OEM seals.The 6 piston calipers from a YZF750R cured this problem and my front wheel will now rotate freely for about fifteen revolutions until it will slow.

Make sure that the pads move freely in the caliper.If they are a tight fit then the pads will not move away from the disc surface when you stop braking.A slight dressing down with a file and some copaslip will help Thumbs Up

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Random13 · Scooby Slapper Joined: 12 May 2013 Karma :

if mine is rotating few turns and you can feel the resistance or hear the scrubbing sound , is that seen as binding or rather ok as the pad don't usually get pushed back all the way .

would the slight scrubbing impact speed or shorten the disc life ?

how would i know the pistons are faulty . I changed the seals and there was no issues there and could see the pistons moving in and out freely

Taught2BCauti... · World Chat Champion Joined: 12 Jan 2012 Karma :

Visual signs of damage, rusting or pitting on the cylindrical surfaces of the piston - you would have noticed when changing the seals.

It's not unusual for the pads to skim the surface of the discs, but the disc itself will tend to amplify the noise.

When fitting new pads, I usually fit them into the caliper with the pistons fully retracted and with the pin(s) but without the retaining spring first, to make sure they are free to move in and out.

I don't remember ever fitting new pads, without having to dress the edges of the steel backing plate, so they are not too tight.

You will know if you have a problem, if you can ride for a few miles without using that brake, and the disc is excessively hot.
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Random13 · Scooby Slapper Joined: 12 May 2013 Karma :

why would not having the retaining clips make a difference ?

i suppose you but it back in after few pump of the brake before riding , right ?

Taught2BCauti... · World Chat Champion Joined: 12 Jan 2012 Karma :

Yes - of course, I should have mentioned that!

Just leave out the retaining spring to make sure the pads are free to move in the caliper when the pistons are fully retracted, otherwise it's hard to tell.

When you are happy with the fit, put the retaining spring back in and re-fit the pads, etc.

Once the caliper is fitted and tightened-up, pump the brake a few times to take out the slack, and test at low speed before tearing off Smile

I find that most makes of bike and car disc pads are quite rough on the edges - like they have been punched out of a sheet of metal - and almost always need dressing with a file before they can be used.
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Random13 · Scooby Slapper Joined: 12 May 2013 Karma :

ok , so does the disc not push the pads back enough?

why would you have to do it manually ?

isn't that a manufacture fault in design ?

Taught2BCauti... · World Chat Champion Joined: 12 Jan 2012 Karma :

The disc doesn't push anything - it's the piston seals that cause the pads to back-off when you release hydraulic pressure in the brake system.

See This Video for an explanation.

If the pads are a tight fit in the caliper, they get stuck and remain in contact with the disc.

If the slider pins are sticking, one of the pads could remain in contact with the disc.

You might be lucky and find the pads are the correct fit in the calipers straight out of the box.

Mainly a quality issue though - I find for the Merc, Brembo pads are better than EBC, Bosch are better than Pagid, etc. but they all need the edges dressing with a fine file before they fit in the caliper properly.
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Honda Varadero XL125(V8)
www.TheFutureIsHere.eu