So does the bed in temperature and pressure have more effect than that of the sintering process in manufacture?
Bike Forum
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Is Pad Clearance a delusion?
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Posted 2 years ago #
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Hi Jon. re "cold and wet and 4/5 seconds of braking". Yep that's me. And I'm using Superstar sintered.
BTW the pair I put on the woodburner last night DID change colour! I'll test the edges against a new pair with a metal file to see if they feel any harder!
Posted 2 years ago # -
JonEdwards - Member
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The bedding in process/getting properly hot. How much depth of the pad does it actually affect? I wonder if its simply a very thin layer. In the summer/heavy usage that hard, heat affected layer gets maintained as the pad wears down. In the wet & cold, the brakes never get that hot, so once the hard bit is worn away,it doesn't get replenished, leaving soft material that just falls to bits.Seems logical but I have no data on this. There certainly are boundary effects but how deep the heat curing goes into the pad I don't know. Do you use big discs? They run cooler.
Posted 2 years ago # -
I'm not sure the woodburner idea is a good one, you've no idea of the temperature they are getting to, they might warp or crack & they'll wear at the high spots of disc to pad contact points more when you put them in the caliper (this will still happen when bedding in with the pads on the bike but the material will be softer so the wear will be more uniform)
Posted 2 years ago # -
What is the official line of the brake manufacturers regarding bedding in? E.g. Shimano, SRAM/Avid
Posted 2 years ago # -
Biggish.180 front on my XC bikes, 200s on my bigger ones.
I'm 10 stone dead, but do like my stoppies, and don't believe there's such a thing as being overbraked.
Posted 2 years ago # -
I think Jedward has it
Here's a thought...
The bedding in process/getting properly hot. How much depth of the pad does it actually affect? I wonder if its simply a very thin layer. In the summer/heavy usage that hard, heat affected layer gets maintained as the pad wears down. In the wet & cold, the brakes never get that hot, so once the hard bit is worn away,it doesn't get replenished, leaving soft material that just falls to bits.Posted 2 years ago # -
Twice last winter I had to cut rides really short due to almost complete loss of front brake - boths times it turned out that brake fluid had squeezed past the seals. Both days were sub-zero.
Googling showed this has happpened to other riders in cold weather.I cleaned everything and replaced the pads both times - I'm still using the same seals with no further problems.
So I think shimano seals are adversley affected by the ambient temperature, perhaps they pull back the pistons better when its a warm day, but get more brittle/rigid when its cold, thus leaving our pads rub-rub-rubbing away at the disc.
Posted 2 years ago # -
Shimano seals will be a different material with them being mineral oil rather than dot fluid
JonEdwards - Member
Biggish.180 front on my XC bikes, 200s on my bigger ones.
I'm 10 stone dead, but do like my stoppies, and don't believe there's such a thing as being overbraked.
Jon - this could be an issue in that bigger discs run cooler - so might never be getting up to temperature. Brakes have a temp range in which they work best. Try smaller discs?
Posted 2 years ago # -
The reading I've done off the back of TJ's theory suggests that curing of a pad, and, more importantly, the transfer of pad material to the disc is something that needs to be done throughout the life of the pads/brake system under normal use.
A few microns of pad material on the disc is easily ground off in foul conditions, and if the brake isn't brought to a high enough temperature to transfer additional pad material to the disc, braking performance is diminished and the braking action changes from adhesive friction (low wear rates) to mechanical friction (high wear rates).
You therefore simultaneously lose braking power and increase pad wear rates.
Managing this in practice would seem to mean running a braking system that has more heat in it, allowing more braking events through a ride to get the heat up. The trade off of course, will be an increased propensity to over-cook the brakes on the more extreme braking events.
Posted 2 years ago # -
Scienceofficer - Member
The reading I've done off the back of TJ's theory suggests that curing of a pad, and, more importantly, the transfer of pad material to the disc is something that needs to be done throughout the life of the pads/brake system under normal use.A few microns of pad material on the disc is easily ground off in foul conditions, and if the brake isn't brought to a high enough temperature to transfer additional pad material to the disc, braking performance is diminished and the braking action changes from adhesive friction (low wear rates) to mechanical friction (high wear rates).
You therefore simultaneously lose braking power and increase pad wear rates.
That seems a reasonable explanation for something that has been puzzling me.So basically we should run the smallest disk we can, and not the other way round. I've been running large disks for the weight of my bike & self, and suffered high pad wear in the wet. Looks like I should have been running small disks instead.
This bedding in business is a flaming nuisance though.
Posted 2 years ago # -
Coming into this somewhat late, but:
"TJ, if it's just heat that cures them, why don't they run them through a kiln as part of the production process? If it's works as well as you're convinced it does, wouldn't mfrs be selling pads as "oven baked for 20x durability" or something similar?"
Hope, EBC and Carbon Lorraine all do
There was a nice feature in one of the rags a while back from the Hope factory- possibly last year's Dirt 100- that showed them going in the oven. But as TJ says, it's only a part of the process.
Posted 2 years ago # -
I can understand why exposing the pads to heat might feasibly make them last longer, but why should mating/conforming them to the disc surface make them last longer?
Posted 2 years ago # -
Poppa - I don't think it does.
It looks like the crucial factor may be as explained by science officer above as well as the curing of the pad under heat and pressure
Posted 2 years ago #
Topic Closed
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