I used shimano mineral oil today in lieu of superglide. Would be the obvious choice..
I'm sure the volatiles in WD are bound to mess it up in some way or other.

I think the OP has a point… a wet gritty ride can eat a set of pads, bedded in or not. I put in a set of pads just before Easter and rode them for a hot dry week in Spain. There must be some truth in the bedding-in thing, because they were still only half worn six months later. This is a pretty good pad life for weekly riding in the South Pennine grinding paste. They were bedded in, without a doubt.

Then a wet ride round Mam Tor destroyed the rest of the pads and half the backing plate in two hours. And for most of that ride they were rubbing like cuss.

Some things I've noticed:
– In cold wet conditions the pistons do not retract as far as they do in warm dry conditions. I tried to reposition the front caliper mid-ride yesterday to stop it rubbing, but couldn't do it. This only happens in the wet.
– A pad that is rubbing constantly but lightly on the disc wears at an inordinately fast rate. It seems to me that light rubbing wears the pad faster than hard braking. Is it a heat thing? Is bedding-in a continuous process that only hardens the top layer of the pad? Or does the pressure of hard braking somehow hold the pad together and make it more resistant to wear?

OK, good point. But I had taken the same view on the mineral oil being OK then..

Memo to self to try always use the silicon instead.

Not bedding in your pads definitely causes premature wear. This was beautifully illustrated at the 'Puffer 3 years ago when some guys got through several sets of pads. It's a bit difficult to bed them in when the temperature is around zero and it's piddling down. Spare pads were in such short supply that Square Wheels stripped them off the new bikes in the shop. A lot of racing time was lost to pad replacement.

We haven't had a repeat, but that's maybe because people have learned to take spare bedded pads with them.

I run drum brakes, so no problem 🙂

OK, I'll slap in some new seals, and promise to use only silicon.

ive never consciously bedded in pads and regularly get very long lifetimes out of my hopes, mini and mono m4, with standard pads
ive never had the phenomenon of wearing a set out in a few hours of riding ???

Interesting stuff lentilshepherd

lentilshepherd – Member

………….They were bedded in, without a doubt.

Then a wet ride round Mam Tor destroyed the rest of the pads and half the backing plate in two hours. And for most of that ride they were rubbing like cuss.

another theory blown 🙁

………. It seems to me that light rubbing wears the pad faster than hard braking. Is it a heat thing? Is bedding-in a continuous process that only hardens the top layer of the pad? Or does the pressure of hard braking somehow hold the pad together and make it more resistant to wear?

Could be the heat thing. I think there is some continuous effects with teh heat effects on the pad

You get boundary layer effects and two types of friction adherent and abrasive and I guess the rubbing could destroy the boundary layer so you only get abrasive friction not adherent.

Ta – more data but another theory ruined. By my theories the pads from Spain should not have worn so quickly.

Were you using the brakes hard at all during the mam tor ride?

*scratches head and wanders off muttering*

Kimbers – hopes do seem to be far less affected by this – anyone had premature wear with hopes?

I've had hope sintered pads last fookin years. They wail like crazy in the wet so I went to organic ones and they are lasting pretty well. Will see what winter does to those. Hopes do have bigger clearance than shimangos though.

TJ, to further confound your theories how do you think the "holiness" of the rotor affects pad life? And I'm not talking about having them blessed..
More holes should clean out the gritty paste, but then could hold it on the edges of the holes to get mixed back in. Fewer holes would dry slower, but would offer a cleaner braking surface when dry. On the other hand more holes would equal less braking surface and higher pressure on the pad surface effectively shaving the top off the pad.
****.. I'm getting OCD about this now..

bikewhisperer

Its got you as well? I find puzzles like this fascinating – gawd knows how much time I have spent looking for data on it and checking engineering journals adn the like

All I would safely say about drillings is that they should help clean the surface – the first drilled discs on motorcycles was to remove the water film from the surface to reduce poor performance in the wet.

I am certain drilling pattern is a variable that affects pad life – but what is best – no data!

and there's material.. Softer steel makes for a better brake afaik. That's part of the reason why Hayes brakes actually work (that's work in the "just out of the box and not seen a winter yet" kind of way..) Their rotors are the fastest wearing I've ever come across.
I think half the time there's too many holes in rotors just to save weight. Look at any ashima rotors to see this. When the hole is half the width of the pad it's bound to offer uneven loading and excessive scraping

The seals pull the pistons back in!…..,WTF no they don't! A completely sealed hydro brake will "pull" the pistons back in mainly due to the spring in the brake lever sucking the fluid back when the lever is released.

Mountaincarrot:

Life is a delusion… god is a delusion… even atheism itself is a delusion.. we're all deluded. It's not just pad clearances. 😛

What about the newish Shimano ones with the big pad clearance? Good or not?

I'm 100% agreed with TJ here, about the bedding in. It does work.

However, to the OP, I know where you're coming from. I'm in Hampshire and when I had Hope brakes the pads lasted forever. But they have sintered pads….
I'm on Maguras now which can only be used with organic pads. I do bed them in, but they last 6-8 months. On CGs recent wet ride in Swinley there were LOTS of people getting through pads, myself included (Although mine were pretty worn and I was expecting them to go, so took spares) There certainly is something in the grit in Swinley that eats pads, for sure.

Shimano pads are generally organic ones. My tip would be to get some (Wait for it…) Superstar sintered pads. IMO when I had my XTs on a VERY VERY wet TransWales that they are better then the Shimano pads in every way for about 1/4 of the price.
Anyway, whatever you get, just get some sintered pads. 🙂

lookmanohands – Member

The seals pull the pistons back in!…..,WTF no they don't! A completely sealed hydro brake will "pull" the pistons back in mainly due to the spring in the brake lever sucking the fluid back when the lever is released.

Rubbish – it is the deformation and rebound in the seals. go read up on it, Have a look at the link I posted on this thread

Regarding the original issue of pad clearance, current XT and SLX have a two-stage actuation (that Shimano call 'servo-wave') that moves the pad quickly at the start of the lever stroke and slowly at the end. This supposedly gives greater pad clearance.

re the bedding in argument, I repeatedly bedded in some new disco sintered pads a couple of weeks ago.
Two more rides since and already the backing has started to come off one of them.
and they were bedded in comprehensively.

Sometimes I really think it is just the luck of the draw.

TJ, re your diagram showing the sliding square cut seal,

Is this not the case? – if not then why?

Mountaincarrot. the seal deforms first – then if more movement is possible the piston slides thru the seal but the deformation remains. Release the pressure and the seal rebounds to its original shape retracting the piston. That is how they work in all brakes I have seen. I don't know if the servo wave ones mentioned above are different but every caliper I have seen, and I have dismantled a few,(cycle, motorbike and car) work like that.

OK, so this relies on the surface sticktion (for want of a better word) and young's modulus of the seal being just right. Am I correct in thinking that if the seal "hardens", it would be more likely to first slide on the piston at initial braking, and provide no deformation, and then provide no return?

Bedding in defo works because the material needs to wear to the minute surface differences of the disc & the material needs to cure – my old C2s never worked so well as the first time I got them proper hot in the Alps, nice brown tinge to the disc as pad material was deposited on it, I could litterally feel them getting better through the decent.
TJ – I, like you have never got less than 1000's of miles out of pads (genuine Hope or EBC) & I'm sure some of this 'I got through a set of pads in 3 rides' is down to not bedding & hardening the friction material correctly leaving it soft & easily worn.

Then a wet ride round Mam Tor destroyed the rest of the pads and half the backing plate in two hours. And for most of that ride they were rubbing like cuss.

I had this last year doing the test valley hot challange a set of well used but not really worn pads disappeared in less than 35k.

Shimano pads are generally organic ones. My tip would be to get some (Wait for it…) Superstar sintered pads. IMO when I had my XTs on a VERY VERY wet TransWales that they are better then the Shimano pads in every way for about 1/4 of the price

I would also recomend these for winter. I found them to hard for summer/dry use as they set up vibrations throught the frame and forks but after a wet ride at afan recently the rear looked the same at hte end as it did at the start.
I am about to order some for my tektro brake on my HT before the hampshire grit eats them.

that seems plausible but I could not be sure. I think its not just stiction but the shape of the seal edge – as it deforms it grips the piston. The defrmation is one by the fluid pressure as wella s the piston moving

remember the clearance is tiny – fractions of a mm

If you look at your brakes as you pull and release the lever does the piston not move away from the disc at all?

Oh and i have found that the pad cleance on my XT servowaves to be more than the Juicy's they replaced.

I'm one of those guys who can get through a brand new set of properly bedded in, sintered pads in about 10 or 15 miles.

I do think it's a heat issue.

Once the pads are hot, they work. The issue is getting them hot in the first place. If you're riding somewhere flattish, or with long fast descents, or with short sharp downs, and you're light, then in the cold and the wet, especially when the pads and rotors are sopping wet,and covered in grit its actually really quite difficult to get them hot – a typical descent for me may only involve 4 or 5 seconds worth of serious braking, and that's simply not enough to get things hot.

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.

I solve the problem very easily to be honest.
I moved to the south of France 😉

Hi TJ If you look at your brakes as you pull and release the lever does the piston not move away from the disc at all?
Yes, almost not at all. I can see some movement with springiness of the calipers relaxing, but I can't say there is any visible gap. This is with everything spotless and newly cleaned. There is however no rubbing contact (ie wheel spins with clearance), until the grit gets in.

I have only once not bothered to bed a set of pads in & I did go through them very quickly.
Now I always do 15-20 sprints up the road and then hard on the brake (front or rear). I do them individually, although it's hard to get enough heat into the rear so have to hang right back off the bike.

When I bed the pads in, the first few stops are generally rubbish and then I can feel the brake performance improve over the next few stops.

On my Juicy 7's, you can see the pads being pulled back very slightly as you release the lever.

I struggle understand how the grit/water mix that sits between your pads and rotor on a wet ride, when not braking can wear the pads significantly, as there is no pressure there to accelerate the wear. If there was sufficient wearing action on the pads, I would expect the brakes to be really draggy too.
But, quite a few people do experience very rapid pad wear in certain conditions, so I'm not saying there isn't something causing this.

So does the bed in temperature and pressure have more effect than that of the sintering process in manufacture?

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!

JonEdwards – Member

……………..
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.

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)

What is the official line of the brake manufacturers regarding bedding in? E.g. Shimano, SRAM/Avid

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.

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.

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.

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?

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.