Disc Brake Pads -- Longevity ?

[tykeboy2003]

I have Avid bb-5s on my tourer which have had some criticism on here and until I discovered the technique (thanks to YouTube) I was forever adjusting them and they were often noisy.

Now, however, they very seldom need adjusting and are virtually silent. Their stopping power is much better than any rim brakes I've ever had, so much so that I have to be careful when applying them.

As for mileage, I've done just under 6000 miles on the bike since September 2012 and I'm on my second set of pads, the original ones still had over 1mm on them when I replaced them.

I do mostly road riding with the occasional railway bike path (in the summer).

[foxyrider]

I actually have found i'm replacing pads at least as often on my discs as on rim brakes, i'm using TRP HyRd in the Pennine and pre Pennines for the most part, not generally heavily laden, i'm @ 87kg and the bike is 10.5kg with the rack, dynohub, guards etc. I don't think its entirely terrain - i rode through a set of rear pads on a tour of the low countries in the summer!

I've tried different pads, sintered/organic Shimano/TRP/35bikes and whilst noise/performance varies life doesn't!

And its not just pads i get through, i'm on my second front rotor, i replaced the original when it developed a distinct 'step' - on measuring it had lost @ 1/3rd of its thickness.

[Antan1]

8000 km of hard use and still working well on my Cannondale Sl4 MTB, I have gone through 4 bottom brackets in this time though

[gregoryoftours]

I have Avid bb-5s on my tourer which have had some criticism on here and until I discovered the technique (thanks to YouTube) I was forever adjusting them and they were often noisy.

Can you remember the link? I'd be interested in watching the video.

[Moodyman1]

About 1000 miles on the stock pads - Shimano Deore mechanical and hydraulic and also Avid BB7. About 8k miles on replacements from EBC. But I am heavy and commute in a hilly and urban area.

[Brucey]

Just googled for how to adjust disc brakes, and it looks anything but easy..

http://www.bikeradar.com/mtb/news/artic ... deo-40573/

just in case you missed it the first time; -read the instructions for your brakes. They vary; you don't need to know about every sort of brake, just yours!

cheers

[tykeboy2003]

Can you remember the link? I'd be interested in watching the video.

Can't remember it, and YouTube is banned here at work, I'll see if I can find it tonight.

However, I can describe how to do it:-

1. loosen the two bolts which hold the caliper on the mounting bracket (not the two which hold the bracket in the frame/fork).
2. insert thin piece of card or equivalent (I use a 25 thou feeler gauge) between the moving pad and the disk
3. tighten the fixed pad adjuster till the card/feeler gauge is gripped tightly
4. tighten the bolts loosened in step 1
5. loosen the fixed pad adjuster till the card/feeler gauge can be removed.

That's it.

The first time I did this, it didn't work at all and I was tearing my hair out as the caliper always moved back into its original position. I found that this was because the convex washer had bitten into the face of the caliper mounting point and it always went back into the groove it had created. I had to use a file to take out the groove and turned the washers round the other way to stop the washer damaging it again. Since then no problems at all.

The convex washers are shown in the attached image, sandwiched between the caliper and the fat concave washers. This was the original arrangement on my brakes and I swapped it round so the flat side of the fat concave washer is next to the caliper.

[andrewjoseph]

I also expect to replace discs every 3 or 4 pad replacements.

Why?

i've had the same rotors on my mtb for... about 8 years. gone through probably 20+ pairs of (mostly sintered) pads and the rotor thickness is still within limits.

touring bike rotors are 7 years old and gone through several pairs of pads. only changed the rotors due to warping.

[phil parker]

I also expect to replace discs every 3 or 4 pad replacements.

Why?

i've had the same rotors on my mtb for... about 8 years. gone through probably 20+ pairs of (mostly sintered) pads and the rotor thickness is still within limits.

touring bike rotors are 7 years old and gone through several pairs of pads. only changed the rotors due to warping.

Does that mean everybody else's should be the same as yours?

Like-wise, my mountain bike is on the same set of rotors for a similar time and I don't expect they will need changing for another few years.

My touring bike gets some abuse in awful weather, fully laden and lots of big hills - I expect them to get warped to the point of annoyance before they will wear too thin to warrant changing. I have a DTI kit and can straighten them to an acceptable level after a long tour, but eventually they will get annoying. For people's bikes that don't get the same amount of abuse as mine - I don't expect the rotors will need changing as often, but for me, I expect I will!

[Redvee]

The fasctory fitted pads in my TRP Hy:Rd lasted 900 miles the replacements, Nukeproof semi metallic are now over 1800 miles old and should last well into 2016 though I do already have spare pads ready to fit when the time comes.

[andrewjoseph]

I also expect to replace discs every 3 or 4 pad replacements.

Why?

i've had the same rotors on my mtb for... about 8 years. gone through probably 20+ pairs of (mostly sintered) pads and the rotor thickness is still within limits.

touring bike rotors are 7 years old and gone through several pairs of pads. only changed the rotors due to warping.

Does that mean everybody else's should be the same as yours?

Well no, and i haven't suggested otherwise. i asked why?

the way you worded the original quote was you expect to replace discs every 3-4 replacements. this sounded to to me you would replace disks regardless of condition or use.

my road bike is also my tourer, used for two week long camping tours in the uk. the only reason i have changed the disk is because the original avid rotors were constantly warping. the shimano rotors have been on there for a few changes of pad and i have no intention of changing them for a few more years.

[phil parker]

the only reason i have changed the disk is because the original avid rotors were constantly warping. the shimano rotors have been on there for a few changes of pad and i have no intention of changing them for a few more years.

Ironically, it is also my Avid rotors that are warping to the point of annoyance, over time, and I will seek different makes and options when I replace them next. Perhaps then I won't be considering to change them as often!

[Brucey]

I think that some brake discs warp because the material they are made from is full of residual stresses, and when the disc gets hot, the residual stresses alter and this warps the disc.

Another mechanism for warping is to do with the uniformity of wear/pressure on the working part of the disc. If the pads bear on the disc unevenly for some reason or just sweep a narrow track on the working part of the disc then the periphery of the disc will heat unevenly; I think this can warp the disc too.

So ideally the disc is stress-relieved during manufacture, and in service the full disc is swept by the pads. I think that Hope discs are manufactured using a process that includes a stress-relief heat treatment, and are certainly meant to be swept fully in use, but I'm not at all sure that others are designed/treated similarly.

BTW a common cause of disc brake 'warping' in cars etc is actually what is called runout-induced DTV. DTV (disc thickness variation) causes sever judder even when it is unmeasurably small. If the disc runs out slightly and just kisses the pads each turn of the wheel, this can soon produce enough DTV to cause judder and then folk will scrap the disc saying that 'it is warped'. Well, it might be, but that is only indirectly related to the judder; if the disc had a larger running clearance then that amount of 'warping' would be no problem.

Obviously a mechanical disc system (and the now less common 'closed' hydraulic type) has the running clearance set by the component combination and the user; normally some kind of acceptable compromise can be found. But in an 'open' (self-adjusting) hydraulic system you more or less 'get what you are given' in terms of running clearance. If one caliper piston starts going a bit sticky, you can lose running clearance and end up in an evil spiral of rubbing, DTV, and scrapping discs off.

cheers

[pedalsheep]

Redvee wrote
The fasctory fitted pads in my TRP Hy:Rd lasted 900 miles the replacements, Nukeproof semi metallic are now over 1800 miles old and should last well into 2016 though I do already have spare pads ready to fit when the time comes.

Is this normal? At that rate the pads on my new Croix de Fer with TRP Hy:Rd will need replacing very shortly. I've only had it about a month and certainly wasn't expecting to need to replace them so quickly.

[Brucey]

Redvee wrote
The fasctory fitted pads in my TRP Hy:Rd lasted 900 miles the replacements, Nukeproof semi metallic are now over 1800 miles old and should last well into 2016 though I do already have spare pads ready to fit when the time comes.

Is this normal?

if you live anywhere hilly, ride in all weathers, use organic-based pads...... then yes, that is pretty 'normal'.

In some places you can destroy a set of such pads in a day's mucky MTBing, easy.

cheers