Front disc brake not locking

Glazed pads - buff off with emery. The adjust as above

Get them adjusted first, long lever travel on those brakes looses you mechanical advantage.

Sitter wrote:

The brake used to lock the wheel fully (as the back one still does). The pads don't seem to be as close to the rotor as the back one when depressed,

From that description (and the increase in lever travel) it sounds like the front just needs adjusting to bring them closer to the disc (fronts will wear faster than rears). Mechanical disc brakes are a pain in the ass (since the pads don't self adjust to account for wear, like they do in a hydraulic brake) - the Tektros on my Kraken are always needing adjusting. Contaminated pads wouldn't cause an increase in lever travel.

apologies for hijacking but i just came on to raise a very similar issue...

my front brake (avid x0) stopped locking up under load at the weekend. a bike mech on the same ride as me suggested that it was down to the pads glazing and suggested buffing them and the discs with emery/sand paper. I tried that and it still didn't work. So i tried switching the pads front to back (back brake works perfectly) but this didn't do anything either, front still didn't work and back did.

therefore I'm thinking it's not the pads. but if it's not the pad what can it be? disc needs cleaning or buffing more??

thanks

Antm81 wrote:

Your pads will need advancing by adjusting them on the caliper, not the lever, mechanical discs don't self adjust to the wear on your pads,

Which is what I said a week ago, lol. As you've just said, I'll bet a pound to a penny that the reason his rear pads work better than the front pads when he's swapped them rounnd is just because the rears are less worn. Save the money (and a trip to the shop) and just adjust the caliper.

supersonic wrote:

I don't think that si the reason.

It's the only possible reason. It's a cable brake, not a hydraulic. The only thing that can cause an increase in lever travel is an increase in the distance the pads are moving. It's a simple case of the caliper needing adjusting to take up the pad wear. The rear pads are only alleviating the problem when switched to the front is because they'll be less worn, and therefore obviosuly thicker, so reducing the gap between pads and disc.

If his Tektros are as much of apain in the ass as mine they'll need constant adjustment (and a good two fingered squeeze, even when properly adjusted).

supersonic wrote:

It is the reason for increased lever travel yes. But not the reason for why the brake is not creating enough friction! Two different things.

Two symptoms of the same problem - his lever's coming back to the bars, so the pads aren't gripping the disc with enough pressure.

supersonic wrote:

Also leverage increases further into lever travel, so there should be more power here if not bottoming on the bars.

That depends on the design of the pivot. Not worth getting into an argument about though. Costs nothing to adjust the caliper first before going to the shop for new pads to see if that remedies the problem, especially given that it's obviously something he needs to learn how to do (given how often it needs doing to keep those Tektros sharp). Here endeth my tuppence worth, lol.

Aye, it's a routine task he obviously needs to learn how to do - mechanical disc brakes are a pain in the butt. I have mine adjusted so that they have very little lever travel (less than my Elixir 3s), but they need a good firm two finger squeeze to bite with any enthusiasm, and frequent re-adjustment (even with the low mileages I've done).

The Rookie wrote:

As I said above, most (emphasis on most) mechanical discs lose you mechanical advantage if you have long lever travel so the brake force is poor, I get the same on my commuter, can lock up the back dead easy with them correctly adjusted, if the lever is long they need a massive heave....

Which supports my diagnosis :P

Adjusted for minimal travel I can lock either end of my Carrera, but it requires a two fingered squeeze (I have dainty hands though, lol).

Sitter wrote:

She, not he :P

My apologies, I'm sure I would've spotted the difference if we'd met, lol.

I never said there was increased lever travel (dunno where you got that from)

Your description in your original post - " I can still squeeze the handle hard (back to the handle bars almost". If the brake was properly adjusted you shouldn't be able to pull it back anywhere near the bar - the cable disc Tektros on my Kraken, adjusted correctly, have a very short lever travel, you'd need to snap the lever to get it back to the bar, lol.

Have only done about 200km on the bike, and nothing that was too heavy on the brakes so wouldn't expect the pads to have worn that much that there is a significant difference in performance

After 200km they'll definitely need adjustment (and the OE pads may not be the most durable of things). The difference between a mechanical disc brake and a hydraulic one (and again, my apologies if you already know this - I'm not suggesting for one moment that just 'cos you're a member of the fairer sex you won't know about such things) is that with a hydraulic brake it self adjusts as the pads wear (so the pads remain a constant distance from the discs), but with a mechanical (cable pull) disc brake it doesn't - so as the pads wear their braking surface moves further away from the disc, causing an increase in lever travel and reduction in braking power.

Like I said, trying to get my head round the tech stuff so I can sort everything myself, not the quickest of ways of getting things sorted when you only have 1 day off a week.

I wasn't being offensive when I said that adjusting them was something that you needed to learn, just that with mechanical disc brakes it is something that needs doing regularly and often (they're a ballache, really) if you're going to keep them sharp, so it is a routine task that you need to know how to do (even if you weren't bothered about labour charges you'd spend half your life going down to the bike shop otherwise), so apologies (again) if you inferred any insult from it.

It can't hurt to try adjustment before paying for new pads, and it's simple (if a bit fiddly) to do. Flip the bike upside down (don't do this bit while riding - I tried that a couple of weeks ago and it hurts quite a lot, lol...) Back the cable adjuster off completely at the caliper end, then wind it out a couple of turns (so that you've got a bit of adjustment available either way). Then loosen the caliper mounting bolts enough so that the caliper can slide on its mount. Next move the caliper so that the outboard pad is just clear of the disc (and parallel to it) and then retighten the caliper mounting bolts. Spin the wheel to check the disc's not rubbing (readjust if necessary). Then, to finish off, use the adjuster screw on the back of the inboard pad (5mm allen key) to set that pad so that it too is just clear of the disc (again, spin the wheel and check for rubbing). That should give you a correctly adjusted brake with a short lever travel and firm feel (even if there's any glazing on the pads). If the brake's still not effective after that then try the new pads, but from your description I think it just needs adjusting correctly.

I had a set of Hayes mechanical brakes that literally needed adjustment every ride sometimes even during a ride. They were shocking things designed by someone who had probably never seen mud or a rough trail and had never needed to use 2 sizes of Allen key to adjust the stupid things. This was in the early days of disc brakes though and designs have improved beyond all recognition.