Front Brake Problems

[Mark_h]

I have a Naked K3 SV1000. The front brake seems to have quite a lot of travel before anything much happens and then it's all a bit gooey. I've wound the reach adjuster all the way out to prevent the lever hitting the bars under "Extremely" hard lever pulling but I guess something's wrong.

In use it's actually fine. Seems to stop OK. but if you give it a heafty pull when on the drive-way it does not feel at all good.

I'm not losing any fluid.
It has braided hoses and they do not look to be split or bulging.

Is it just a case of bleeding them or likely to be more serious?

Having never bled brakes before am I likely to be involved with seized bleed screws or any other nasties not mentioned in the Haynes manual?

Off for a ride on Saturday and don;t want to make matters worse than they already are. So I'm looking for some guidance of the likelihood of me making matters far worse this evening and so scuppering the ride tomorrow. They do not seem to be getting any worse and I've tried a couple of emergency stop style hard braking stops so I'm fairly sure I'll be safe enough on the ride tomorrow if not then the RAC gets a good flexing to get me home.

Thoughts and advice greatfully recieved.

Cheers,
Mark

[yorkie_chris]

Bleeding it through for 1 or 2 reserviors full of fresh fluid would be my first action.

Bleed nipples may take a bit of a tug to get off, but if you're careful they're unlikely to snap.

[embee]

Always use a ring spanner or socket on bleed nipples. Using and open ended spanner will round them off. I always grease them before fitting, but if yours look bone dry then a drop of penetrating oil or even WD40 at the threads a day or so before trying to undo them may help. Keep oil etc away from discs/pads.

Bleeding brakes is not rocket science but if you haven't done it before it really is worth trying to find someone who has done it to show you. So many people don't achieve satisfactory results (try a search!), yet it's really only common sense and method.

Brake fluid will take paint off, so treat it with respect and have a wet rag handy to immediately wipe any spills or drops off paint. Wash it thoroughly.

Remember that when you take the reservoir lid off, you also need to remove the diaphragm underneath. More than one person has tried filling the diaphragm and wondered why the brakes wouldn't bleed.

Use a DOT4 brake fluid, there are various grades but don't worry about that, (and you can use DOT5.1 but don't use DOT5. Just stick to a DOT4)

I would run some fresh fluid though the system rather then bleed it all out first, I did this only a few months ago on a Caponard for both the clutch and rear break. Guy said they felt like they did new afterwards, but then the fluid was about 4 years old so didn't surprise me.

[Mark_h]

cheers chaps.

Ring spanner, 3in1 oil, lots of rags and a trip home via Halfords for a can of Dot4. Sorted. Perhpas a few more pleading posts tomorrow if it all goes horribly wrong and a request for someone local with a clue to come and laugh at my ineptitude.

I blame Ducati. I took an ST3 out the other day and when I got back on mine I relaised my brakes felt like they were made of marshmallow. Probably been like it for ages but had not ridden anything better to compare how bad it had got.

[Sid Squid]

Fresh fluid won't do any harm - but it probably won't do any good either.

You've got sticky piston/s.

At least one fluid seal is 'hanging' on it's piston, this causes the piston to retract further than normal when you release the brake, when you pull it again the brake has to pump up a bit before reaching the back of the pad, giving exactly the problem you describe.

[Mark_h]

Originally Posted by Sid Squid

Fresh fluid won't do any harm - but it probably won't do any good either.

You've got sticky piston/s.

At least one fluid seal is 'hanging' on it's piston, this causes the piston to retract further than normal when you release the brake, when you pull it again the brake has to pump up a bit before reaching the back of the pad, giving exactly the problem you describe.

So I guess that's a caliper strip down and not the sort of thing to do in limited time with no experience the night before a ride. Is this something that causes a critical failure (ie, no brakes) or just an annoyance to get fixed soonish rather than right now.

And is replacing the fluid just a case of drain it out the bottom while filling at the top or more to it?

Any experienced caliper sorter-outers in Fleet with nothing better to do this weekend

[yorkie_chris]

Could possibly cause dragging, but I can't see how it's likely to cause a total failure. Mr squid?

Edit: not cause dragging, but if one piston is too far back, the other dust seals may be causing other pistons to stick

Originally Posted by Sid Squid

Fresh fluid won't do any harm - but it probably won't do any good either.

You've got sticky piston/s.

At least one fluid seal is 'hanging' on it's piston, this causes the piston to retract further than normal when you release the brake, when you pull it again the brake has to pump up a bit before reaching the back of the pad, giving exactly the problem you describe.

what he said, or it could simply be your pads are getting a bit low?

Brake fluid is designed not to be overly compressible, but it is still slightly compressible ... the more of it there is in the system, the more there is to compress ...

Obviously as pads wear, pistons go out, more fluid in system.

I find mine get a little spongy/more leaver travel when old/worn pads, stick some new ones in and I am backing off the adjuster as the leaver is now too far out.

BTW I actually wedged a bit of metal in my front leaver to give it more 'span' I just didn't feel that even when on max span it gave enough clearance.

[embee]

Originally Posted by Mark_h

....is replacing the fluid just a case of drain it out the bottom while filling at the top or more to it?

Not quite, which is why I would recommend being "shown" by someone who's versed in the art.

OK, it's not difficult. The idea is to purge fresh fluid through the system to replace all the old stuff without getting air bubbles in aswell. As long as you bear this in mind it'll make more sense.

There are different approaches, but without other equipment the "pumping" method is probably for you.

You need a jar (anything) and a piece of small bore hose which is a good fit on the bleed nipple. If you haven't got anything to hand it might be worth picking up something from Halfrauds while you're in there. There is a device called "Easibleed" or similar which sort of works, and at least it'll give you some suitable hose.

Rule#1, don't completely empty the reservoir at any time during the process, you'll have to start again.

Fit ring spanner to one bleed nipple, fit the hose and run it into the jar. Rule#2 - Don't kick the jar over.
Slacken off one bleed nipple, keep the ring spanner on it so you can nip it up again when required.
Pull in the brake lever to pump fluid out of the nipple, hold the lever still, nip up the nipple. Rule#3 - don't overtighten.
Release the lever to replenish the master cylinder and repeat the exercise, co-ordinating the undo-squeeze-nipup cycle until the fluid level in the reservoir is nearly down to the bottom. Remember rule#1.

Add fresh fluid and continue.

As suggested it is worth doing a couple of fills to make sure all the old fluid is purged through.

Now go to the other caliper and repeat. Remember Rule#2......and Rule#1.....and Rule#3.

Finally top up the reservoir to near the max line, carefully refit the diaphragm and make sure it doesn't overflow (easier to add fluid than take it out). Fit the cap....admire your handiwork.