Terrifying brake fade (SLX, brand new)

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  • Terrifying brake fade (SLX, brand new)
  • I’ve just fitted a set of brand new SLX brakes. First ride out yesterday, and after an initial great start (lots of power, good modulation) on the second descent of the day the rear started to fade a bit (ie pulled back with no power, pumping the lever made it work ok) and by the last descent I pulled both brakes hard and they just pulled to the bar – nothing. Again fortunately pumping them got some power back and slowed me down.

    I’m fairly heavy (around 85 kg) and I was cracking on (last descent was Gores in the Peak down to the reservoir if anyone knows it) but I wasn’t brake dragging much if at all.

    Just in need of a bleed or something more sinister? I need to shorten the hoses so bleeding is no problem.

    Running UberBike sintered pads if that makes any difference.

    Premier Icon Yak
    Subscriber

    pumping the lever made it work ok

    sounds like it needs a bleed

    That’s what I thought. I’ll do that and see how it goes…

    amedias
    Member

    (ie pulled back with no power, pumping the lever made it work ok) and by the last descent I pulled both brakes hard and they just pulled to the bar – nothing. Again fortunately pumping them got some power back and slowed me down.

    ^ thats not really fade, that’s a fluid/bleed issue.

    It sounds like you have air in the system somewhere, get it properly bled and it should be fine.

    cokie
    Member

    What rotors are you running?
    +1 on needing a bleed.

    what size disc? but it does sound like it needs a bleed.

    Erm, 203 on the front and I think 160 on the back.

    Bleed it is – fingers crossed.

    agree with all the above but where did you get them?

    Bit poor to be supplied like this, but the last shimano brakes I bought came in bits which was actually my preference as the hoses needed tinkering

    Merlin, but they were boxed and sealed so I don’t think it’s really their fault. Guess they could have been sat in a warehouse for months or something, who knows?

    JonEdwards
    Member

    What state were the pads in post-ride? Given what the ground conditions would be like round there, it would be entirely possible (IME) for cheap non-OE and/or soft compound pads to simply disintegrate, leading to a similar sensation.

    Does sound more like a bleed issue though…

    Pads were ok – plenty of meat left both front and rear, that was my first thought. But it was only a short 11 mile ride and the problem started after the first descent so even with organic pads I’d not expect them to die *that* quickly and sintered ones tend to last a bit longer.

    If it was a 30 mile ride with lots of brake dragging then I reckon it’d be almost a guaranteed answer!

    Premier Icon zilog6128
    Subscriber

    Exactly the same symptoms with my XTs last year. Bleed sorted it out.

    Premier Icon brassneck
    Subscriber

    Exactly the same symptoms with my XTs last year. Bleed sorted it out.

    Plus one. It was my ham fisted shortening though that introduced the issue.

    Ironically I didn’t shorten them as I was worried I’d bork it up and really wanted to ride yesterday.

    Sigh. On the plus side I got a load of PRs on Strava… Turns out I can brake a lot later than I thought 😉

    Pigface
    Member

    Take top off reservoir and just flick the brake lever in and out that will often really help before you do a full bleed. You can often see a few tiny bubbles.

    Could it be that air in the reservoir has migrated into the hose and callipers? Maybe just leave it over night with an elastic band round the lever to hold it back to the bars, I’ve done this in the past to spare me a bleed and it works pretty well.

    Premier Icon vondally
    Subscriber

    Mine were from Merlin and needed two bleeds at merrlin before settled down I am 95 kg do was less than impressed

    Premier Icon Russell96
    Subscriber

    Over the years I’ve had multiple brands and models of brakes from various online retailers and I have yet to receive any that haven’t needed a bleed, even if it’s just the elastic band trick as 13th floor describes.

    Premier Icon gelert
    Subscriber

    A mini bleed will sort this. Just the funnel on the leaver bleed port, some oil in the funnel and pull the plunger out and put it back several times until bubbles stop coming up and press the leaver several times too. The plunger acts as a bubble puller and the oil switches places with each bubble. Dead easy quick fix in 5 minutes. If you get discoloured oil coming up though… full flush bleed time.

    My XT rear feels like this after being left hanging vertically for a couple of weeks after a race and that probably made some trapped air come up to the leaver so when I went out for a quick spin it felt crap and needed pumping a bit to work. It’ll be back to normal when I get a minute to do this little trick.

    GMBN video on Shimano Brake Bleed has this trick mentioned at the very end. Worth a watch.

    Mmm, bought some slx from merlin the other week as well and they’re sat on my winter (unfinished) build. Better get the thing finished, out there and tested.

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