Front disc brake not locking

Sitter

Hi, hope somebody can help here please...

My front disc brake (Tektro Novela mechanical disc) won't lock up when I squeeze on the handles like it used to. I've had a go at cleaning it with disc brake cleaner stuff but it hasn't made any difference, I can still squeeze the handle hard (back to the handle bars almost) and still peddle forwards, albeit slowly. 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, but there is nothing to go any tighter to push them closer, although the pads do come in to contact with the rotor when I squeeze the brakes. I've had the pads out to check them and they aren't worn, and they've not come in to any contact with lube/grease/anything they shouldn't have to my knowledge.

New to this bike tech malarkey, seem to be getting to grips with some of it slowly but quite tempted to take it to LBS to get looked at as I seem to be spending my very rare days off trying to get my head round everything and doing little/no riding!

Can try and get pics up if that will help?
Thanks.

supersonic

I would try new pads - sometimes can't see any contaminents. Clean the rotor again, install new pads and bed in.

There is a static pad adjuster, and the cable arm adjuster - the latter can be brought across as close as you wish by simply adding cable tension.

maringirl

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

Sitter

Looks like it might be new pads then, buffing the pads hasn't seemed to have done anything, thanks for the help. Not gonna be riding today now anyway, heavens have just opened and I got soaked to the skin just moving the bike the 2m in to the front door!

The Rookie

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

Sitter

I've already tried altering the lever travel but to no avail. Long or short travel I've still had the same result with the brakes not locking out.

Kowalski675

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.

slindborg

I had a very similar issue with the mechanical discs on my old spesh. A simple session of moving the cable in the caliper housing and then adjusting the other pad to be in the right place with the screw saw the brakes back to normal/better than ever.

If you fancy it, you could rough up the pads with some 120grit paper

MDobs

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

The Rookie

Put your own post up, yours are nothing like sitters so it would be bad to post confusing advice in his thread due to that.

Sitter

It's the pads. Put the pads from the rear brake in to the front and they work fine so it's a trip to the shops tomorrow. Thanks for the help.

Antm81

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, hence why when you put the rear pads in they work fine as they aren't as worn as the fronts. On my daughters bike it's just like a disc on the side of the caliper that can be turned winding the pads in towards or away from the disc.

Kowalski675

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

I don't think that si the reason. Unless his lever is touching the bars. If not, is the pads.

Kowalski675

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

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.

Kowalski675

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

Well he said almost ;-). No doubt it will help with evening things out, but the problem is very likely the glazed pads. Also leverage increases further into lever travel, so there should be more power here if not bottoming on the bars.

Kowalski675

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.

supersonic

Lol, I do agree on adjusting the caliper. Should be biting earlier for betetr control.

Kowalski675

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

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....

Kowalski675

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

She, not he :P

I never said there was increased lever travel (dunno where you got that from), I just said I'd tried altering it with the same response either way.

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, and not to the extent that I have. Calipers etc. have been adjusted and fiddled with etc. but resulted in no difference in braking performance from the pads.

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.

Kowalski675

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.

The Rookie

I have to adjust the mechanical disc brakes on my commuter about every 100 miles to keep them feeling sharp, a small amount of wear can give a big increase in lever trave.

stubs

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.

Kowalski675

Mine needed re-adjusting (both ends) after 15 miles round Gisburn (admittedly I probably use the brakes more than a decent rider would). They're a pain in the butt really, if I hadn't bought my new bike I would've replaced them with some Shimano hydraulics.

Sitter

My bad WRT the travel, that was after my first attempts at various adjustments, increased the travel then forgot that was why it was going that far back lol, also got myself a little confused with names of various parts of the braking system which probably didn't help either, me thinking i was adjusting one part when it was actually something else but hey, at least i've learnt! After quite a bot of fiddling and making adjustments, the front brake now locks the wheel, but only once I'd put in the new pads. Also took the opportunity to add bar end grips (I know, I know, but my wrists find it much more comfortable). Now to get out and ride!
Thanks again.

Kowalski675

And they all lived happily ever after

Sitter

For now anyway!