New disc brakes - zero bite

Ned Flanders

I have just built up a new bike and fitted disc brakes. It's my first time with discs and I could use some advice.

The rears seem OK but the fronts I can't get to bite at all. Held in the workstand I can pull the lever fully to the bar and move the wheel with my hand. It's touching and scraping but there is no bite at all.

The calipers are CX77 with Ice Tech rotors and they're cabled up to 105 shifters so compatibility should be fine. All brand new components. I've given the rotors and pads a good clean to see if I'd got any oil but there is no change.

I took it to a hill to go down and see if they just need to bed in but frankly it was terrifying because there really is no bite at all. Holding the brake lever down made no difference to my speed whatsoever.

Is this normal for new discs/pads? Any tips?

timothyw

You probably need to adjust the static/inboard pad.

Most mechanical disk brakes have one side that moves, one that doesn't - the moving caliper presses the disc against the static one by bending it.

It sounds like you are getting the bending but it isn't meeting the static pad.

You'll need to regularly adjust the static pad to account for wear.

robertpb

Sounds like there is air in the system, you need to bleed them.

arlowood

robertpb wrote:

Sounds like there is air in the system, you need to bleed them.

They are mechanical (cable) disc brakes not hydraulic

Ned Flanders

TimothyW wrote:

You probably need to adjust the static/inboard pad.

I'll have a look but to my eye they're spot on. Same distance as the rear.

veronese68

Ned Flanders wrote:

TimothyW wrote:

You probably need to adjust the static/inboard pad.

I'll have a look but to my eye they're spot on. Same distance as the rear.

If the caliper is not parallel to the disc it may look like it's the same distance but it's not over the whole contact area. Set it all up very carefully ensuring that everything is lined up as it should be. Once it is set up you will have to adjust them periodically but that should be about it, keep all chemicals away from discs and pads. If you wash the bike don't let any spray cleaners onto them, either remove the wheels and cover the calipers or don't use a spray on cleaner just a bit of soapy water. Discs need to run very close to the pads.

svetty

Ned Flanders wrote:

TimothyW wrote:

You probably need to adjust the static/inboard pad.

I'll have a look but to my eye they're spot on. Same distance as the rear.

If you can pull the lever all the way to the bar either the cable isn't tight enough or the pads are too far away from the disc

Ned Flanders

I'm wondering if it's the cable tbh. I'll take it all apart and start again.

veronese68

Ned Flanders wrote:

I'm wondering if it's the cable tbh. I'll take it all apart and start again.

compressionless cables help, but only a little.

timothyw

Veronese68 wrote:

Ned Flanders wrote:

I'm wondering if it's the cable tbh. I'll take it all apart and start again.

compressionless cables help, but only a little.

And if that were the issue you'd expect the rear to be crap, not the front (where cable run is short...)

veronese68

TimothyW wrote:

Veronese68 wrote:

Ned Flanders wrote:

I'm wondering if it's the cable tbh. I'll take it all apart and start again.

compressionless cables help, but only a little.

And if that were the issue you'd expect the rear to be crap, not the front (where cable run is short...)

Yes, that's obvious now you say it. :oops:
I'd forgotten it was the front brake.

crankycrank

It's possible the pads or disks had some contamination on them that didn't get completely removed. Take the pads out and run them over some sandpaper on a flat surface until you have a completely fresh surface. Shouldn't take much sanding. Clean the disks again and go over with some rubbing alcohol or any cleaner that doesn't leave any residue. Start with this and if no luck let us know.

svetty

crankycrank wrote:

It's possible the pads or disks had some contamination on them that didn't get completely removed. Take the pads out and run them over some sandpaper on a flat surface until you have a completely fresh surface. Shouldn't take much sanding. Clean the disks again and go over with some rubbing alcohol or any cleaner that doesn't leave any residue. Start with this and if no luck let us know.

If that were the issue the levers wouldn't go to the bars - it's a new build so I doubt contamination is the problem and sanding away at the pads will only increase the gap between pads and rotor......

crankycrank

Ah, I missed that, agreed.

zefs

Svetty wrote:

Ned Flanders wrote:

TimothyW wrote:

You probably need to adjust the static/inboard pad.

I'll have a look but to my eye they're spot on. Same distance as the rear.

If you can pull the lever all the way to the bar either the cable isn't tight enough or the pads are too far away from the disc

This, on my TRP Spyre's I couldn't get them to bite, until I adjusted the cable. TRP recommends working with the pad adjustment only but that wasn't giving enough braking performance.
Also, find a quiet place and perform some hard braking to bed in the pads since they are new.

bbrap

Wind the adjusters in until the wheel is locked solid, then tug on the brake levers, that will ensure all the slack in the system has gone. Now back off the adjusters until the wheel is able to move, sight down between the pads and disc to ensure they are parallel. Adjust caliper as necessary until they are. Then use adjuster so there is minimal gap between each pad and disc. Job done. Then take bike out and do a few hard braking sessions to bed the pads in properly (may have to readjust after).

Ned Flanders

That’s another thing. The LBS did the cabling for me but it wasn’t until I got home that I realised they hadn’t fitted any adjusters.

I’ve got them on my other bikes but ridden for years without ever needing to use them so I figured I’d be be fine without.

nappyrash

http://si.shimano.com/pdfs/dm/DM-BR0009-00-ENG.pdf

The pdf does recommend an inline adjuster, without that you will just have to pull the cable at the caliper as tight as possible while doing the clamp bolt up. You might then be able to take some of the slack out by using the brake arm adjustment screw to move the pad closer to the disc rather than the pad adjuster.

I would take it back to the LBS and tell them to do it correctly, didn't the 105 kit come with adjusters.

darkhairedlord

Sounds like you need n+1

timothyw

Ned Flanders wrote:

That’s another thing. The LBS did the cabling for me but it wasn’t until I got home that I realised they hadn’t fitted any adjusters.

I’ve got them on my other bikes but ridden for years without ever needing to use them so I figured I’d be be fine without.

If the LBS did the cabling surely it is on them to make the brakes work? Take it back in.

Inline adjusters are not necessary, but they are very handy if you want to replace the brake cable/outer without unwrapping your bar tape. Or if the adjuster at the caliper seizes.

trekvet

Apart from everything fitting and working correctly, it does leave, as a couple of guys have mentioned, that the brakes need bedding in. When you are sure the pads prevent you turning the wheel by hand, find a safe place and make repeated heavy stops, yes you'll sweat by number 10, but that is what I did and now mine stop me a sixpence / 5p.

Ned Flanders

TimothyW wrote:

If the LBS did the cabling surely it is on them to make the brakes work? Take it back in.

They fitted the cables for but for the BB7 I'd bought. I hadn't realised they weren't compatible with the Shimano rotors but they did the cables anyway and I fitted the CX77 myself. Badly, it seems.

I've had another fiddle with them today but something definitely isn't right so I'll take it to the LBS and ask them to have a play.

Vino'sGhost

Local bike shops are a pain in the arse. Do the job yourself and save hours of tooing and froing

Ned Flanders

Vino'sGhost wrote:

Local bike shops are a pain in the ars*. Do the job yourself and save hours of tooing and froing

The reason I'm here asking the questions is that I've wasted time failing to do it myself. Also the L in LBS means I don't waste hours tooing or froing.

Ned Flanders

darkhairedlord wrote:

Sounds like you need n+1

This bike is my n+1. Got a summer road, winter/turbo, MTB and now this do-it-all gravel bike.



I took everything apart earlier and gave everything a good clean down and tightened everything I could. It seems to have done the job and I have a workable front brake. I took it for a brief spin and hopefully they'll get better as they bed in because compared to the rim brakes on my roadie they're godawful in terms of stopping power.

cougie

I see this a lot. Disc brakes seem much more variable than the good old rim brakes. Is it a learning curve ? Rim brakes invariably just work.

penguin_of_death

I have the same brakes with no inline adjusters and compressionless cables and I could put myself over the handlebars if I wanted.
Things to remember - make sure the brake arm is under some tension before clamping the cable and that both pads are independently adjustable with Allen keys

Ned Flanders

Penguin of Death wrote:

Things to remember - make sure the brake arm is under some tension before clamping the cable

I worked that bit out myself from experience with regular rim brakes. The instructions specifically say not to but I ignored it..

cycleclinic

getting disc brakes to work is very simple. For mechanical it invoice the TRP Spyre or Spyke, compressionless casing and EBC pads to replace the Tektro ones.

Every other mechanical disc brake is the one piston kind and not so great as adjusting for pad wear is less simple. Although it will be possible to get your CX77 brakes to work well.

The pads need to be very close to the rotors if they catch that fine so long as the rotor spins freely. This is the case with all mechanical disc brakes and the cable cannot be slack at all. it must be under tension or it will be useless.

vegasfoster

If using adapters, I would double check if they are correct adapters and oriented correctly.

Ned Flanders

Adapters?