Yonks since I’ve had to do so...GMBN vid suggested short sharp stops and use water. Other vids suggest less aggressive and more draggy slow downs without stopping.
Which one for rear XT 180mm disc and new Shimano metallic pads? This will be a works car park job tomorrow lunchtime.
BPW on Sat so early glazing not an option?
Get up to a decent speed, brake firmly to a slow speed (do not stop!), repeat many times. You're aiming to get the pads and disc hot enough to transfer pad material from the pads onto the disc. If you stop however you run the risk of allowing more material to transfer in those spots which can cause vibration issues as the pads grip more where there is more pad transfer.
It's exactly the same process for any disc brake, you want a nice even transfer of the pat material onto the disc. Don't bother with water or anything else, just let them cool naturally.
Also - are you going from the same pads as the new ones? if not, give the discs a clean with a scotchbrite pad and some brae cleaner first.
This video is the best one I've seen that describes it.
I put them in the caliper and go for a ride. Is it that complicated?
It's fine if you want no brakes for the first few runs of the day...
never really had a problem, what do you mean by first few runs of the day? How many? Maybe organic is much better but even with sintered I've changed mid way trough a day and been fine
With new (same type) pads and old discs you'd already have a layer of the pad material on the disc so you're correct in that they'd already be bedded in pretty much, with just the pad and rotor surface maybe not making 100% contact, but that's much less an issue on MTB brakes, more an issue on car/motorbike brakes with larger rotor areas.
So yeah, if you're only swapping pads then there shouldn't need to be much done. If you're on brand new pads AND discs though, that's when you'll have no braking! 🙂 Better to be safe than sorry though.
Yes.
New discs are the "real" problem. A new disc needs some time to bed in. At least a "couple days" biking?
New pads, old disc: I get them really hot / working hard on the first rides (easy but steep and fast trail). Quick thing.
The "not stopping thing", above: didn't know that. Makes sense.
Agree with the above, a few sprint up to speed and firm almost stops. Don't stop like the GMBN video says.
As for being necessary...... I've swapped pads and not been able to lock up even the rear brake until I'd done a few (usually do about 5-6 per brake) bedding 'stops'. Maybe I just have weedy little fingers. Get reasonable brake life and haven't suffered glazing.
I tend to do the second water one as i can do it in my garden.
I let my neighbour borrow the SS for summer, hopefully by the time he returns it the pads will be bedded in. Job done.
Other than that, a few decent stops will do it, or a bit of dragging and pedalling hard but not for too long to get heat in/material transferred. I'm not sure if it's a bit obsessive but I too try to avoid stopping completely.
I've once had real issues with bedding in, but that was on a car - first trip after fitting new pads (possibly with discs too) and fully laden car, got to a roundabout after enjoying a twisty section and had to really press quite heavily to get worryingly little braking. The problem on a car is that if the pads aren't keyed in you have a small area getting hotter and can get fade from not working them all that hard. It's not really an issue with bikes as the disc area is so much smaller, so any heat will be transmitted across it faster, and the pads will key in a lot faster (in an equivalent ot the above situation they would certainly have fully bedded in prior to the stop at the roundabout).
You will feel a distinct increase in braking sensitivity once they're bedded in. They feel a bit wooden up to that point.
with the pads off run them under the tap, and grind them together a bit(don't touch the contact surfaces with your fingers), then fire them on the bike, find a hill, drag the brakes a bit then do a few high speed stops, job jobbed.
Got the run them under water and grind them together tip from GMBN when they interviewed one of the mechanics up in fort william btw(can't mind which team), works a treat, grind them a good bit that way. Pads then worked brilliant on a new rear rotor as well as an old front rotor.
Was the Syndicate fella - "https://www.youtube.com/watch?v=piWBVDh1pTE"
Tried it with some new pads the other week. Worked well.
That was the vid! not GMBN then, my memory failed me there!
Water is really not a good idea - all you are doing is grinding away the surface of the disc and pad with grinding paste effectivly
Bedding in is 3 things. depositing a layer of pad material on the disc, conforming the pad to the disc and curing the pad with heat and pressure
Water is really not a good idea – all you are doing is grinding away the surface of the disc and pad with grinding paste effectivly
I don’t get how a paste that is made up of brake pad material and water could be anymore abrasive than the pads itself
I do 4 crash stops and they are done.
Adding water just makes them squeal
That syndicate video, he's not bedding in the pads (and doesn't need to as it's new pads going onto already bedded in discs), he's just rubbing off the outer coating on the pads. You'd do that with a couple of stops when riding but it does stop any crap that is on the pads getting onto the disc.
Rubbing pads together with water won't help on a new disc as you're doing nothing to transfer pad material to the disc.
Bedding in is 3 things. depositing a layer of pad material on the disc, conforming the pad to the disc and curing the pad with heat and pressure
Exactly this. Although the conforming the pads to the disc bit isn't really needed on push bikes as the rotor area is so small, the undulations in the disc surface are tiny.