Viewing 40 posts - 1 through 40 (of 117 total)
  • bedding in pads – is this bollox?
  • big_n_daft
    Free Member
    rob-jackson
    Free Member

    bump

    Daffy
    Full Member

    Nope, bedding in pads in common practice. I’ve seen Shimano pads last only 2 hours of riding (changed in the car park before the ride) in the Peaks when not bedded in compared to several months when correctly cured.

    Why do you think Automotive brake pads require several short sharp stops before they perform correctly? The heat and pressure applied to the pad, forces material from the pad on to the disc and also removes any surface compounds from the pad. Finally the heat and pressure applied during those first hard stops, compacts the pad material making it slightly more dense and less prone to surface abrasion while maintaining a high friction co-efficient.

    D.

    TandemJeremy
    Free Member

    Its more of an issue with organic pads. Bedding in does 3 things – it cures the pad under heat and pressure, it conforms the pad to the disc and it deposits a microscopic layer of pad material on the disc.

    This allows adherent friction to occur which is when you get a semimolten boundary layer that in effect sheers. thus you get long pad life. If you do not have this boundary layer you get abrasive friction and short pad life.

    On the tandem the brakes get very hot indeed and are used a lot – and pads last thousands of miles not matter the conditions.

    So brakes, riding styles, pads will bed in easily in normal riding, some rtequire the deliberate bedding in. You can tell the change in feel as they bed in. At the puffer I bedded in anew set of pads simply by dragging them down the main descent

    rob-jackson
    Free Member

    daffy read the question before spouting – its about a METHOD of bedding in not whether or not TOO bed in!!

    devs
    Free Member

    Blowtorch and oven are indeed bollox. It’s all about material transfer between pad and rotor under heat and pressure. IMHO of course before I get accused of being all TJ.

    cakefacesmallblock
    Full Member

    It’s also about those pads on that disc. A new, properly cleaned rotor just ridden from the box wont feel as good as the original one, unless pads are changed and bedded.

    TandemJeremy
    Free Member

    The blowtorch and oven will only do a part of the bedding in process as above – however if you are using the same pads the layer on the disc will still be there – he also makes a good point about dragging one brake rather than using two intermittantly

    best tip tho – use hopes as they appear to have much longer pad life. i used less than a set of pads (a half worn set wore out and the replacements less than half worn) in 9 laps

    M6TTF
    Free Member

    as above – I just do 20 or so hard braking stops and ride dragging the brake slightly to build up some heat. been told to give them a quick soak with cold water after too, but didnt seem to make any difference

    TandemJeremy
    Free Member

    cold water – superstar by anychance? will do nothing to bedding in.

    mrjmt
    Free Member

    I thought the cold water thing on the superstar recommendation was so that you knew you’d achieved a decent temperature, not part of the bedding in process per se?

    vorlich
    Free Member

    daffy read the question before spouting – its about a METHOD of bedding in not whether or not TOO bed in!!

    Maybe if you actually phrased your OP unambigously rather than lazily pasting in a URL, you’d have got the response you were looking for, rather than the response you got. 🙄

    stumpy01
    Full Member

    I can’t see the tip about using your turbo trainer & fitting the pads in the rear caliper to bed them in being much good.

    You are only stopping the back wheel from rotating, there is barely any momentum there compared to doing 15mph down the road & coming to a quick stop.

    I often struggle to get heat into the back pads even when bedding in on the road & doing repeated stops. I have to do more hard stops on the rear compared to the front.

    epo-aholic
    Free Member

    Nope, always bed in my pads (where possible) however when i haven’t when they have been changed during 10under for example they didn’t last, coincidence?

    thisisnotaspoon
    Free Member

    You are only stopping the back wheel from rotating, there is barely any momentum there compared to doing 15mph down the road & coming to a quick stop.

    If you keep pedaling thats ~400watt, gets it pretty hot, especialy with a small rotor.

    thomthumb
    Free Member

    best tip tho – use hopes as they appear to have much longer pad life.

    keep trotting out the dogma 🙄

    TandemJeremy
    Free Member

    thomthumb – appear to

    I have been following this rapid pad wear issue for a long time and collecting information. while its clearly complex and multifactorial hope brakes do seem to have much longer pad life in general. Somone commented on this in the last couple of days.

    Pyro
    Full Member

    At the Kielder 100 this year, there was a bit of a consensus that the Clarks pads were the ones lasting best. This was, presumably, un-bedded, straight replacements.

    Drac
    Full Member

    Never bedded any in and never had any trouble.

    TandemJeremy
    Free Member

    Drac – you will be bedding them in or the pad will go in a short time – its just that your set up, type of riding, riding style means they bed in in normal use

    coffeeking
    Free Member

    I’m wholely for bedding and believe it’s required… however…in relation to the story, I’m not so sure about bedding of metallic sintered pads “by oven”. By definition the sintering process has taken the brake friction material to a pressure and temperature that the metal has begun to melt and fuse throughout its volume. Your oven can’t do this and the pretty rainbow coloured change is simply oxidation due to the fact that you’re re-heating them in air (they’ll have been sintered in an inert atmosphere).

    Either way, bedding is required to do the material transfer and surface conformation process, but the only good an oven is for, IMO, is burning off contaminants and saving otherwise trashed pads. I’ve run brakes without bedding them in and sometimes got away with it, sometimes (particularly in scottish mud) I’ve lost a set of pads in a couple of wet miserable rides.

    bigrich
    Full Member

    you aint melting the metal, your trying to melt the resin in which the metal is embedded. the mp. is 200C(ish), most ovens can do this. otherwise the entire mcains empire would be ruined.

    IHN
    Full Member

    Who was it that TJ used to have the big rows with about bedding in pads?

    I’m in the ‘bedding in’ camp by the way. A few hard stops to do so.

    coogan
    Free Member

    I’ve never ‘bedded’ pads in. Slap them in and just ride with them. Always worked for me and have lasted fine.

    thisisnotaspoon
    Free Member

    I agree with TJ on this.

    My hopes always outlast the pads in my shimano (OK) and avid (the worst) brakes, the power goes the opposite way though. with the avids outperforming the shimano and hope.

    Small rotors = more heat = longer life, and theres no need for 8″ disks in mud anyway.

    I usualy take loadsa spares on holliday and run new pads each day, big hills + sunshine = hot brakes and pads that last for months.

    coogan
    Free Member

    Really? You change pads each day? Done two weeks in Canada and never changed pads. Only changed a set in the Alps once as the first set were older anyhow.

    CaptJon
    Free Member

    coffeeking – Member

    Either way, bedding is required to do the material transfer and surface conformation process, but the only good an oven is for, IMO, is burning off contaminants and saving otherwise trashed pads. I’ve run brakes without bedding them in and sometimes got away with it, sometimes (particularly in scottish mud) I’ve lost a set of pads in a couple of wet miserable rides.

    Genuine question… if the bedding in isn’t about getting heat into the pads, but is about getting some pad material on the discs, why wasn’t there a transfer at the start of your wet miserable rides?

    bigjim
    Full Member

    The pad material on rotor argument falls down the moment you get some mud on the rotor or caliper, as its essentially like using valve grinding paste and will remove anything that has built up on the rotor.

    simons_nicolai-uk
    Free Member

    I think it depends on the pads. Hope pads don’t seem to need to specific bedding in (though i find throwing some sandy mud at them helps – also a good cure for slight contamination with brake fluid). Magura have some very specific bed in instructions.

    My attempts to save pads that had got fluid on them in the oven/blowtorch/setting fire to them always resulted in me completely destroying the pads or having no effect.

    joolsburger
    Free Member

    I put new sintered pads in ride up and down my street full tilt and brake with the front until I can endo then brake with the back until it locks up easily. I suppose that’s bedding in and then they seem to last for months. In the Alps this year I changed a set of fronts for Kevlars at the top of the lift and they had gone by the bottom of the first descent (20 minutes or so) so I won’t be using them again.

    thisisnotaspoon
    Free Member

    coogan – Member
    Really? You change pads each day? Done two weeks in Canada and never changed pads. Only changed a set in the Alps once as the first set were older anyhow.

    Read the post, I just do that to bed them in, I’ve never worn pads apreciably in Spain, forgot spares the first time and came back with the same ~1mm of pad I went out with. Had problems glazing them though.

    M6TTF
    Free Member

    cold water – superstar by anychance? will do nothing to bedding in.

    no it was another chap i ride with from time to time, no idea where he got that jewel from

    TandemJeremy
    Free Member

    Genuine question… if the bedding in isn’t about getting heat into the pads, but is about getting some pad material on the discs, why wasn’t there a transfer at the start of your wet miserable rides?

    It is about heat as well

    bigjim – Member

    The pad material on rotor argument falls down the moment you get some mud on the rotor or caliper, as its essentially like using valve grinding paste and will remove anything that has built up on the rotor.
    One turn of the wheel and the disc is clean – a part of the reason for the drillings in it. Its only with the layer of pad material on the disc you get adherent friction. if you don’t have it you get abrasive friction and rapid wear. Its a very hard and thin layer

    My theory for the very fast wear that some folk get in some conditions is that the layer on the disc is abraded away faster than it can be replenished thus leading to abrasive friction and rapid wear

    devs
    Free Member

    In crude terms. Rotor = cheese grater. Pad = cheese. Melt cheese over surface of crater and hey presto no gratey, just grippy. Don’t melt cheese over grater and cheese get grated away. Ken.
    If your disks are too big for you = no heat = pad wear.
    If it’s really wet and miserable and you don’t find a hill big enough to clean and heat brakes = pad wear. In bad cases you seem to wear pads without even braking, just with the paste rubbing against them. Simples.
    Hopes are betterer because there is more surface in teh first place. Nae great science rocketry.

    lumberjack
    Free Member

    As an engineer involved in braking (aerospace and rail), I’ve spent a fair amount of time with friction materials, testing them and developing them.

    Bedding in is definitely required to condition the surfaces and the heat forces out any moisture which may have become entrained within the material. As has been stated above, it’s all about setting up a stable interface layer, once it’s established, there is very little abrasive wear.

    We spend a long time explaining to aircraft operators that a series of low speed taxi stops cause far more wear than a landing which gets the brake up to temperature quickly, thats probably more specific to carbon brakes though!

    sugdenr
    Free Member

    I like the cheese analogy, clear as cheddar now.

    *skulks off to re-place smaller brake discs and bed new pads all fitted yesterday*

    Baldysquirt
    Full Member

    Coogan, I think he’s saying that he uses the alps riding to bed lots of sets of pads in for the rest of the year…

    bigyinn
    Free Member

    For something like the puffer, I’d suggest getting a number of sets of spare pads (all same make as ones in the brake already if poss) and go through the bedding in process with each set before you need to use them in anger.
    That way you should be using similar compounds on the discs, you’re also bedding them in and hardening them up. Then put them back in the packets until you need them.
    Not ideal and a bit of a PITA, but it means they should last a lot longer.

    kimbers
    Full Member

    fwiw ive never (consciously) bedded in a set of pads and yet they seem to last ages

    (i use standard hope pads on both dh and xc bikes)

Viewing 40 posts - 1 through 40 (of 117 total)

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