Cable disc brakes question.

[Grarea]

I have some of the above on the bike.
They, I think, are just cheap ones.
They are tektro.

I haven't had a chance to look at them properly until now.
I really like my brakes set nice, but these seem to rub as soon as you bring them in a bit close.
So, for the time being they have been set loose so that they don't rub.
I was looking forward to fiddling.

Today was the day to try and achieve half decent brakes.

When I look at them when activated, they both (front and rear) seem to just push in from one side.
It even distorts the disc as it pushes the disc to one side against the other pad.

Is that right? Does that exist?
Is that how cheap disc brakes work or do I need to do some work to them?

[gloomyandy]

Yep that is pretty common and not just on "cheap" brakes, even well respected ones like the Avid BB7 make use of this single sided design.

[Mr Evil]

...I really like my brakes set nice, but these seem to rub as soon as you bring them in a bit close...

If you can't get the pads close without rubbing, then you may need to

• True the rotor
• Align the caliper with the rotor

Both are easy to do with common tools. I won't describe how, because there are plenty of guides out there that you can find via a search engine.

[Grarea]

Yep that is pretty common and not just on "cheap" brakes, even well respected ones like the Avid BB7 make use of this single sided design.

Ah, ok, thanks.
I just assumed brakes squeezed from both sides.

With that knowledge, I have just had a good look at them.
I discovered the inner pad adjuster.
It was set far from the disc.
Things are an awful lot better now.

I now see how they work and adjust.
Smashing, thanks.

[Grarea]

...I really like my brakes set nice, but these seem to rub as soon as you bring them in a bit close...

If you can't get the pads close without rubbing, then you may need to

• True the rotor
• Align the caliper with the rotor

Both are easy to do with common tools. I won't describe how, because there are plenty of guides out there that you can find via a search engine.

Yes, thanks, I was thinking about it wrong, assuming they were squeezing both sides.
I had loosened and adjusted the calipers on the frame a few times, I had made sure the rotors were true, was pretty sure the wheel was in straight etc etc.

What was happening was that the outer (pad that moves) was much closer than the inner (stationary) pad.
Now I realise how they work I can fiddle much better.

Thanks for the reply though.

[Brian73]

TRP Spyre seem to be the best cable discs at the moment

They use a dual piston operation

http://road.cc/content/review/90569-trp ... disc-brake

[Gattonero]

TRP Spyre seem to be the best cable discs at the moment

They use a dual piston operation

http://road.cc/content/review/90569-trp ... disc-brake

Yes and no, still they won't match very well the cable pull of some brake levers/shifters.
That is essential for the correct operation and power of the braking.

[Brucey]

TRP Spyre seem to be the best cable discs at the moment

They use a dual piston operation

http://road.cc/content/review/90569-trp ... disc-brake

Yes and no, still they won't match very well the cable pull of some brake levers/shifters.
That is essential for the correct operation and power of the braking.

yup, and they have some very tiny ball-bearings inside that are rather corrosion-prone. FWIW the design is predicated on the idea that flexing the disc 0.2mm to one side is a terrible thing to do and that if two pistons move they might be more powerful; basically, it isn't, and they are not.

To cap it all they lie about the weight of the things (their weights don't include things like bolts and pads, 'cause yeah, the brake really works well without those.... ). I'm far from convinced that they are a worthwhile step forward vs (say) BB7s

cheers

[Grarea]

I am pretty pleased with the ones I have as it happens.
Now I know how to adjust them.

The flex before was MUCH more than 2mm, it was not great.

I have only had a quick play and they are pretty good.
I shall see if I find their limitations, but so far on medium hills in the wet, they have been fine.

I am quite surprised.
I thought I might need to upgrade them, but I shall use them happily for now.
I will either wear them out or get some more miles (experience) with them before I look to upgrade them.

[Gattonero]

I think that the main problem is that you cannot have "one caliper for all". Ain't gonna work well, there's no escape from that.

[Brucey]

I am pretty pleased with the ones I have as it happens.
Now I know how to adjust them.

The flex before was MUCH more than 2mm, it was not great.

I have only had a quick play and they are pretty good.
I shall see if I find their limitations, but so far on medium hills in the wet, they have been fine.

I am quite surprised.
I thought I might need to upgrade them, but I shall use them happily for now.
I will either wear them out or get some more miles (experience) with them before I look to upgrade them.

some things to look out for

- that the (organic/semi-metallic) pads wear out quickly in wet conditions
- that the quality of cables/setup is not compromising brake power and feel too much
- that the amount of wear in the pads is less than you might expect; check the manufacturer's recommendations but it usual [edit, duh.. I meant unusual...] for the allowable wear to be very much more than about half the lining thickness; typically the friction material is 2.4mm thickness and you might be allowed to wear about half of that away before you should change the pads
- failure to change the pads early enough can result in degraded braking performance, loss of the remaining friction material, or even loss of the pad from the caliper body (very bad)
- that the disc is positioned properly in the caliper slot; the manufacturers typically suggest that the disc is about 1/3 across the gap, nearer the moving pad. A reasonably quick and efficient way of setting them up (with a slack cable) is to loosen the caliper mounting screws, slip a piece of thin card between the moving pad and the disc, wind the fixed pad adjuster to clamp the disc lightly, then nip the caliper mounting screws. Then back off the fixed pad adjuster (about half a turn usually), and remove the card. Check for running clearance on the disc, if all is well, fully tighten the caliper bolts, then perform final adjustments to the fixed pad adjuster and the cable.
- when you adjust the brake for wear, it is tempting to use the fixed pad adjuster and the barrel adjuster in the cable. However in many road disc calipers the brake arm has rather limited useful travel (test for this by working the arm with the wheel out; the arm should have way more travel than you would actually use and the brake should be closing all the way) . So it is good if you find out where the limit is; with many cable disc brakes there is no separate pad adjuster for the moving pad, and once the pads are a bit worn, you are in danger of running out of moving pad travel if you just use the barrel adjuster. With some models of brake it is necessary to move the caliper on its mountings slightly when the pads are half-worn else you can't wear the pads to the manufacturer's limit whilst being sure that the brake will carry on working with further wear.
- thankfully the worst road caliper designs appear no longer to be sold; I have seen brakes that ran out of travel (with a loud click sound) when the balls ran off the ends of the tracks in the ramps(through pad wear), and others where the arm stopped dead (at what looked like half-way, again through pad wear). Either issue can leave you with no brakes, without warning.

hth

cheers

[boblo]

IIRC, Brucey's last point above is what lead to the Spyre recall when they first came out. Unfortunately the more complex the braking system, the less idiot proof it is and the more you need to keep an eye on things.

[reohn2]

IIRC, Brucey's last point above is what lead to the Spyre recall when they first came out. Unfortunately the more complex the braking system, the less idiot proof it is and the more you need to keep an eye on things.

I agree,I think we were lucky in that my first experience of disc brakes was our Cannondale tandem fitted with Avid BB7's,these proved to be a complete game changer for us and the best tandem brakes we've ever had especially in the wet.
Theyre so simple to set up,adjust and service that they completely sold me on discs.

I won't say anymore as my BB7 droning is legendary on here

[Gattonero]

IIRC, Brucey's last point above is what lead to the Spyre recall when they first came out. Unfortunately the more complex the braking system, the less idiot proof it is and the more you need to keep an eye on things.

To be fair, the way a mechaincal disk brake caliper works, is quite simple. That design fault is very much a schoolboy error.