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Thread: Front Brakes

  1. #1
    Junior Member
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    Front Brakes

    The front brakes on the tracer always felt a bit spongy and didn't really inspire.. At all! I could easily pull the lever almost all the way in to the grip on all but the widest setting.. Being a new bike I never really though much of it, they worked well enough to bring it to a halt quick sharp so I just rode on, I assumed it was just the way the Tracer was!

    Recently I changed the front tyre, a simple enough job with the right tools. Some soapy water, a Givi S450 repair kit (for the CO2 bottles) and a pair of motion pro bead breakers/levers (which are really worth the investment). 15 Minutes later tyre all changed, bead popped on, inflated to 30 lb good enough to ride to the nearest petrol station. I reassemble the front end and pump the brakes back up (take up the clear space twixt the pads and discs), scoot off across the car park but when I brake the lever pulls all the way in to the grip and no braking occurs. A couple of pumps gets them working again but a tad bit further down the road the same shit happens again.. This is proper scary.. After a bit of messing around I whip the calipers back off and squish the pads and pistons all the way in then pump them back out, in, out, in, out, in, out... About 5 or 10 times each side..

    This is the best part!

    Now the brakes feel like I expected them to feel.. They actually grab quick and I can stop in half the distance! The front end dive is a bit harsh and I've never noticed that before because the brakes have NEVER worked properly! This basically means the pistons in the calipers have ALWAYS been like this since I first got the bike! I'll be stripping and cleaning them over this weekend.

    This is the level of service I have come to expect from dealers these days.. Can't even PRI and road test a bike properly. Thinking about this the back brake feels a bit weak too, I really have to stomp on it to have any effect, could this be suffering the same "sticky piston" problem!

    Anyway, a question! 4 pot calipers are supposed to move in unison aren't they? IE; all 4 pots should move in and out when you brake?
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  2. #2
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    Yes. All together!

  3. #3
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    It sounds as if they were never bled properly.

    The old tip of tying the lever back to the bar with a strong rubber band overnight can get rid of some air and restore a firmer feel to the lever (works on the back brake too - just use a weight tied on the pedal).

  4. #4
    Senior Member Unfazed's Avatar
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    My brakes always felt a bit spongy and when I mentioned this to the dealer he said it was the ABS and it's the same on the other MT's he had. I checked a couple of other new bikes and they were spongy as well.

    The brakes I had on my previous VFR12 (ABS) would have stopped the titanic and felt really firm... Wonder what Yamaha UK would think of this?

  5. #5
    Junior Member kdimitris's Avatar
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    Go to a specialist brake mechanic to do a bleed or do it by yourself.
    Even better , if your bike is about 2 years old change brake fluid.


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  6. #6
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    I suspect (well, actually, I know) ABS systems are not so easy to bleed as the old ones were. So it seems that neither Yamaha nor their dealers are prepared to spend time on getting them spot on during the PDI.

    As a matter of interest, I help at our local IAM's advanced braking course, where we do scrutineer all the bikes before they take part. I was surprised to find a couple of virtually new bikes (not Yams, but including a BMW with Brembos) where the front brakes were very spongy. Of course the owners hadn't realised that anything was amiss, as they'd been like that from new.

  7. #7
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    Quote Originally Posted by bobh View Post
    I suspect (well, actually, I know) ABS systems are not so easy to bleed as the old ones were.
    What makes you say that? As far as I know and ABS system doesn't act within the fluid aside from the piston/valve faces.. Not sure how to explain it but the pistons/valves literally drop the pressure in the system by creating a "chamber" or "void" for the fluid to drop into. Kind of like the reverse effect of a kink in a hose pipe!

    With that in mind I can't see how bleeding an ABS system would be any more or less awkward and messy to a normal braking system?

    Either way, my initial thoughts that PRI/PDI inspections are half arsed like most things these days are being confirmed by hearsay!
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  8. #8
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    It's just that there are more nooks and crannies in an ABS system where air can get trapped. So if you're bleeding from dry, it takes a bit longer. But if you're just changing the fluid in a previously-filled system, it's no more difficult.

  9. #9
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    If I do a fluid change or bleed I remove the callipers, push the pistons fully in then wedge them in, if it's just a change pump the brake until the fluid is almost gone then top up and repeat, that way no air enters the system.

  10. #10
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    Quote Originally Posted by kev View Post
    If I do a fluid change or bleed I remove the callipers, push the pistons fully in then wedge them in, if it's just a change pump the brake until the fluid is almost gone then top up and repeat, that way no air enters the system.
    Agreed. I have a selection of wooden blocks to hold the pistons back right in, so there's minimum volume on the cylinders to flush out.

 

 

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