Bedding in disc brakes

[quixoticgeek]

If I understand correctly, my shiny new TRP spyre disk brakes need bedding in. I've had a bit of a google, and from what I can tell this means that I need to basically heat the brakes up to Hot™ a few times to deposit a layer of pad on the disc rotor. Is this correct?

Several of the guides/posts I've found on the subject suggest using a down hill stretch to get enough speed to really put some heat into the brakes. Alas this is Noord Holland, the idea of a hill is a bit of a foreign concept...

Does anyone have any advice on how to bed in disc brakes (if indeed I need to?)

J

[Cudzoziemiec]

My Spyres definitely improved after a few days or so use. I do live on a hill though. But I expect you don't really need to do anything other than bear in mind that the first day or two they will be a bit weak. And it's not terribly weak. It's not like a 1950s rod brake roadster or even a 1980s steel rim brake in the wet!

[bobb]

With the lack of a hill, you could just find somewhere that isn't too busy, then do lots of sprints before ramming on the brakes to get the heat up.

Whatever you do, make sure it's a dry day! If you do it in the wet you can trash the new pads very quickly*

*This perhaps applies more to MTB where wet mud is involved more

[Aushiker]

I have TRP Spykes on my fatbike and Giant Connect brakes which I am pretty sure are TRP/Tektro brakes on my Giant Defy Advanced 2. With both bikes I simply rode them, being aware that the brakes where new and hence doing my best to avoid any emergency stops. Within a day or so they were both bedded just fine. 

I didn't bother with any special bedding procedures.


Giant Conduct Front Hydraulic Disc Brake by Andrew Priest (Aushiker), on Flickr

[andrew_s]

Basically, get up to 20-25 mph (30-40 kph) and (almost) stop, braking as hard as you can safely, maybe a dozen times for each brake.
Do front and back brakes separately.

The back brake is best done on the flat, hanging your bum off the back of the saddle to add weight to the back wheel. A gentle downhill saves effort for the front brake, but if it's too steep your braking is limited by the requirement to keep the back wheel on the ground.

Best done whilst the brake pads are new, on clean, dry tarmac.

You should find that braking noticeably improves during the process.

[Brucey]

it depends on what pads you have.

There are several effects at work

1) simple wear allows the pads to contact fully and intimately against the disc

2) the friction couple is conditioned at the interface (which may involve transfer of material onto the disc, and will involve small changes in the finish of the discs and pad faces)

3) the heat cycles will condition the pads.

The last of these applies mainly to so-called 'organic' pads (which includes semi-metallic and Kevlar, etc; basically anything that isn't described as a sintered pad). Basically all these pads use a resin binder to hold the many pad ingredients together, and this resin will degrade at temperature. This degradation alters the friction properties of the pad, and whilst it is occurring the pad is often outgassing and this will be accompanied by a temporary  reduction in braking efficiency, i.e. the brakes may appear to 'fade'.

Deliberately taking the brake through an aggressive heat cycle will condition the pads so that they will subsequently work consistently in normal use. Obviously this should be repeated whenever new pads are fitted.

'Organic' brake pad compositions are complex (up to 200 ingredients are used) and can vary enormously. Some of the ingredients are normally considered to be lubricants at high temperatures and are there to mitigate the natural increase of friction coefficients that might otherwise arise as the temperature increases.  This means that the exact behaviour of different pads will vary during conditioning, and some pads need every little conditioning by comparison with others. However it falls into the 'won't do any harm, and might do some good' category so it is good practice to condition the brakes whenever new pads are fitted. If nothing else it gives one confidence that the brakes will work properly when called upon to do so.

With sintered pads points 1& 2 above still apply but point 3 doesn't really. The only effect of point 3 with sintered pads is that any slight traces of oil (eg from fngerprints) might be burnt off the brakes.

cheers

[quixoticgeek]

Thanks everyone.

Will I have to bed in again if I swap a disk rotor at any point? My Dyno hub when it's ready will have a centre lock rotor, so I can't just transfer my existing rotor to that wheel.

Was Also planning on having one set of wheels with spikes on for the winter and one set with marathons on for when it's not icy. I've got 5 rotors in stock (due to a purchasing error with a double click...) plus the 2 currently installed

J

[Brucey]

if the disc rotors are of the same type and are essentially unworn, only minimal bedding in is required when swapping wheelsets or discs.

If the discs are of a different type or are worn, some more bedding in is required.

cheers

[Brucey]

a bedding in procedure that can be carried out on flat roads is described on the final page of this manual

http://cdn.sram.com/sites/default/files/techdocs/gen.0000000003513_rev_b_2012_bb7_bb5_service_manual_english.pdf

it is meant for BB5 and BB7 models but the same thing will apply to pretty much any disc brake fitted with organic-type pads.  Slightly less bedding in is required with some sintered pads on new discs.

BTW I didn't mention this before but the point about getting uniform contact between the disc and the pads is important (and becomes more important when installing the second set of pads on used/slightly worn discs). If the contact is not uniform, the disc is heated unevenly which, in extremis, can cause problems.

cheers