[Closed] Total mechanical disc brake failure on CX bike

Sounds like the cables slipped through the retaining bolt

hmm. You aren't very specific as to how the failure occurred.

If they are cable discs you need to adjust the pads to account for wear

both brake levers went straight to the handle bars and gave no purchase

all of a sudden having been fine minutes before?

need more info....

I had that on my tcx,brakes ok in normal use but when lots of pressure applied on a steep downhill they were terrible. All assembled correctly and adjusted properly,the problem was the extra effort disappeared into cable compression. I fitted compressionless cable and it was better but nothing like hydros.

My money is on the cable bolts not being tight. Never ever trust a bike shop to inspect a bike properly before you collect it.

Failure would be different. Is OP saying that both brakes failed as in the either something in the lever snapped or both calipers snapped.

OP learn to maintain your bike!

I'm guessing they still don't work? Cable pulling through the pinch bolt would be my guess.

Oh and hydraulic brakes are expensive because its new technology and because the hydraulics and particularly reservoir fits in a shifter, some thing that isn't required on an MTB. Mtb brakes don't come with a shifter. They'll come down in price though...

The pads need a quick fettle every now and then to account for wear. One of the main reasons I changed to hydraulics for my new bike. I had the shimanos on my TCX. I mistakenly adjusted the cable pull, felt fine initially then the back would not stop the wheel. The arm on the calipers was hitting the body before the pads had any effect

My money is on the cable bolts not being tight. Never ever trust a bike shop to inspect a bike properly before you collect it.

After 10 weeks both suddenly went together? I'm dubious.

Pad wear

Troll or bullshit.

I doubt it'd be pad wear.. Yes mech brakes need adjusting now and then as they wear but you'd notice the lever travel slowly increase over time.

My money is on damaged cable or the bolts that hold the cable were not tight.

Does anyone have a grudge against you?

Could be sabotage.. But with the bike being so new I'd still guess the bolts on the calipers that clamp the cable weren't quite nipped up tight enough.

The brakes were becoming spongy while out on the ride, but giving sufficient power given the conditions. Then all of a sudden the brake levers went to the handlebars all of a sudden. And the there was no purchase.

When I stopped to check them, the wheels would spin with the brakes on full. I adjusted the cable adjuster slightly and this was enough to get some purchase, but after another 5 miles, there was another complete failure and I had to walk the downhills on the way home.

Yes they have had no maintenance, but they are only 10 weeks old and all my other road and mountain bike brakes don't need adjusting that regularly!!

Sounds scary

Had this on an older MTB last weekend, if they are the type of mechanical brakes that have a fixed side and a single 'piston' that activates a moving pad..... The fixed pad side is adjusted using a kind of threaded barrel and this is locked in position using a grub screw through the calliper.

What had happened (investigated once we got home) is that the locking grub screw hadn't been tightened and that meant that the barrel adjuster had gradually worked out so there was no contact possible = no brakes, front or rear, simultaneously.

Very strange that they would both degrade by the same amount and fail at the same, its very rare for front and back brakes to wear equally.

Does sound like pad wear if some adjustment brought them briefly back, did you check all the cables to make sure nothing had slipped?

Tell us what model the brakes are too, something with 2 moving pistons or 1 moving and a fixed side? have you checked the pad condition since?

but they are only 10 weeks old

weeks is a terrible measurement, is that 10 weeks = 200miles of road, or 10 weeks = 1000miles and offroad mud and grit?

Well the clamp screw may still be just loose enough to allow slight slippage.. Also the caliper mounts on mech brakes need to be set so both pads are as close as possible to the disks without rub or there will be excessive pad and consequently cable and lever travel.. I'd guess the shop didn't set the brakes up at all before purchase.. They probably gave them a quick test without riding it, got some purchase and assumed all was ok.

You need to keep on top of the pad wear and wear adjustment (cable side and other side) or they can fail if the cam runs out of movement.

Typicall they need adjustment every few rides, takes seconds though.

More like 200 miles of 50% road (all very wet) and 50% off serious mud!

Had it with BB5's that scared me quite a bit - downhill in traffic; being used to hydro's where you don't need to fiddle, but - soon learnt with cable on the cx you need to keep a feel on the lever travel and adjust frequently. Now with BB7's that are better and easier to adjust, but it's become a common check to do for me.

You need to learn how to adjust mech brakes.. But first port of call is remove pads and inspect, and check the cables and caliper mounts properly clamped.

Take it back to your dealer to have a look anyway. Has it been for a checkup since you bought it? Many dealers offer that as a free service.

Then look up the manual for your brakes and learn how to look after them.

We had a guy come into the shop last summer who'd managed to complete the Great Glen Way with no brakes because he had no idea how to adjust them. I mean it's only your brakes, right? 🙄

Wasn't there an issue with some make of cable brakes where you could pull the calliper arm over the top of the actuating lobe* which resulted in the harder you pulled the less braking action took place.
* May not be the correct technical term.

Some cables discs go "over cam". Tektro Lyras are very good at this. I ditched mine years ago for that reason and a clubmate totally lost his brakes without warning a few weeks ago. It seems to involve the cable adjustment, especially if this is used to close the brakes up rather than do it properly. Having said that today my BB7s seemed to have no bite whereas yesterday they were great. Not enough miles to affect near new pads.

Sounds like pad wear to me. You need to move the pads closer to the rotor (not using the barrel adjuster but by using whatever mechanism your particular brake uses to move the pads)

TRP Spyres? I have these on my Giant TCX. Same thing on the rear brake. The brake levers pulls to a point, jams as if the brake is full on (it isn't, it's dragging on the disc, not gripping it) and then suddenly pulls back all the way to the bar. I'm guessing it's a cable snagging in the outer. New cables and pads, front and rear tomorrow to fix it once and for all or the calipers are going in the bin and I'll be getting BB7.

Doesn't sound anything like pad wear to me! They suddenly failed, they didn't get gradually worse.

I used to have this all the time with Hayes Sole's. Same deal as with mechanical disc brakes: one moving pad and one fixed and you needed to adjust for pad wear.

All would appear fine, until all of a sudden neither brake would work.

In reality, what would be happening is the back would have worn to point it provided no useful activity unnoticed some time earlier. Only until the front went too would it become apparent there was a problem.

This would happen to a few of us with the same poor brakes / early superstar pads on muddy / wet rides, when braking was always a bit "loose"!

Spyre mechanical's have both pistons moving. Mine are 100 miles old and have done it since new.

Sounds like cables slipping the anchors, not pad wear.

It's easy to check which it is: just pull the levers and watch the caliper arm. If the arm moves immediately you pull on the levers, your problem is pad wear. If you can pull the levers partway back before the caliper arm moves, your problem is cable slip.

Pad wear on 10 weeks, nope.

Has OP checked the tightness of the bolts securing the cable? Just sounds like cable slipping through to me as said before

Come on OP, how much lever travel were you getting before it suddenly failed?

Didn't TRP Spyres have a recall because of this fault about a year ago . The newer ones have been redesigned to prevent this from happening .

I am guessing the pads/cables had a lot of give and the bearings that generate the pressure (the ball bearing cam) ran past the end of the ramp.

What were the brakes?

Didn't TRP Spyres have a recall because of this fault about a year ago . The newer ones have been redesigned to prevent this from happening .

I have a set of the newer ones and can confirm they do not do this anymore. I wore a set of the stock organic pads down to nowt on a wet ride before Christmas. The lever travel increased so I adjusted the cable but even with max cable pulled through they didn't bite but still worked and didn't fail totally as the older ones could.

I can sort of imagine the OPs situation - you could be riding round the woods using a bit of brake to scrub speed off. Hit the road and get up to much higher speeds and go to grab the brake and find they have no grab at all at higher speed.

Pad wear after 10 weeks? Yes, definitely possible.
I wore a set out on my cx bike within 2 weeks & a friend did the same, new & bedded in ( I bedded them in for him) & they wore to the backing plate in two races, so less than 2 hours.
Genuine pads & yes I do know how to bed them in properly-I do it for a living.

in the wet pad wear can be quite noticeable on cable systems, but you must adjust for it AT THE CALIPER not the cable adjustment.

all the cable adjuster is there for is initial setup and accommodating the cable/outer bedding in NOT pad wear.

if you do adjust at the cable you're giving away mechanical advantage.

i've had hydro brakes go through a set of pads in two rides when the conditions have been bad. hydros are better at dealing with this, though often you'll still find the bite point changes at the lever under those conditions. and then the ****ing things don't stay fully back out when you put new pads in, so you end up starting the next ride with new pads climbing with the brakes on....

like my bb7s i do.

user error.

I adjusted the cable adjuster slightly and this was enough to get some purchase, but after another 5 miles, there was another complete failure

all the cable adjuster is there for is initial setup and accommodating the cable/outer bedding in NOT pad wear.

There should be adjustment mechanism (red dials on BB7s) on the caliper for proper adjustment of pad-rotor gaps

Also agre with the comment up there that your rear probably failed a while before the front, but wasn't a big deal while the front was still OK

Pad wear after 10 weeks? Yes, definitely possible.

a consistently wet (with dirty gritty roads) Festive 500 did for mine in a week, and I had a similar 'failure' to the OP's, and as explained above. Unadjusted-for wear meant the pads could move so far that the caliper arm had gone beyond applying any meaningful force to the pads (the closer the arm gets to the cable mount the shorter the effective lever, the less the mechanical advantage). Net result a complete "brake failure" whilst still having some pad friction material left, and nothing broken or actually failed within the caliper.

In short, user error/neglect for both me and the OP. High mileages in crap conditions means nearly daily adjustment for mechanical discs.

I went through half a set of sintered pads halfway though one 50min race last sunday, to the point I switched bikes at 30 mins to have the lever pull where i wanted it. Wettest CX season I cam remember!

I'm in the pad wear camp, my BB7's could do a set of pads in a couple of rides down to virtually nothing on the stopping power. As has been said they don't self just so you do have to keep and eye on them, but even so I found they would only last so long.

Similar issue to you in the way home from a ride pulled brakes and kept going towards a round about! 😯 foot down and luckily I stopped!!

Got a hope system later that week! Now really reliable, and the pads last much longer. The advantage being I didn't need to change my running gear as my preferred stuff is Campag.

I can't see the pads being worn out in such a short time unless racing or in similarly intensive and arduous dirty gritty conditions.

Also you'd know they were wearing by gradually increasing lever travel and gradually worse brake power , a sudden failure suggests somethings not screwed in tight enough or somethings broken.

This is essentially a brand new bike don't forget, with the owner apparently never doing any adjustments.

Brand new bikes do need fettling though.
Combine some cable stretch with the outers settling into their ferrules, the pads wearing even if only slightly and there's plenty of scope for the brake to come to the end of its travel before stopping the bike. Plus we don't know how well they were adjusted out of the box.
Either way, there's not enough information from the op to be sure but there is scope for it to be down to adjustment, wear or incorrect fitting.
Scary stuff, but it just goes to show that it pays to have a good understanding of the parts fitted to your bike, and the need to check them, especially brakes!

in the wet pad wear can be quite noticeable on cable systems, but you must adjust for it AT THE CALIPER not the cable adjustment.
all the cable adjuster is there for is initial setup and accommodating the cable/outer bedding in NOT pad wear.
if you do adjust at the cable you're giving away mechanical advantage.

Not quite right. The necessary adjustment for pad wear depends on the system. Avids are designed such that it requires adjustment of the piston wheels, but Spyres are designed such that it is adjusted with a cable barrel.

And the reason for not adjusting for pad wear on an Avid by adjusting the cable is AIUI not that you don't lose mechanical advantage (AFAIK you don't, and a falling-advantage design would seem rather odd), it's so that you don't risk hitting a hard stop and being unable to apply more force.

Not so , Spyres are adjusted by an allen adjuster key on each side of the caliper , each one winds one of the pads in or out .

Spyres are designed such that it is adjusted with a cable barrel.

I've found with mine that you can get away with using the barrel to adjust for wear (on a long muddy ride, say), but you get much better performance if you sort it out with the pad adjusters (3mm allen key). Dunno why, that's just my experience of them. Great brakes if set up right, can be a bit horrible if not. Quite easy to bugger up if you're not mechanically minded too I suspect...

Spyres are designed such that it is adjusted with a cable barrel.

I'm pretty damn sure the instructions on mine said adjust for pad wear with the barrel. Willing to stand corrected but I've chucked the paperwork away now.

Edit: Aye, here we are: "Thread the barrel adjuster out to take up cable slack or compensate for pad wear."

TRPBRAKES.COM "https://www.trpbrakes.com/userfiles/file/SPYRE_Final_053113(1).pdf"

(To be fair the next line says you can use the outboard pad adjuster, too, but unsurprisingly you need to then re-align the caliper.)

I'm pretty damn sure the instructions on mine said adjust for pad wear with the barrel

I'm 99.9% certain they say NOT to adjust them using cable tension.

http://singletrackmag.com/forum/topic/trp-spyre-replacement-pads

Suspect they were organic or similar pads, which is this weather will last minutes rather than ride........
Should be sintered in these conditions

Read half way down about the compound they supply.

https://www.trpbrakes.com/category.php?productid=1199&catid=206

Having read the instructions for the Spyres they give the option of using EITHER the barrel adjuster or using the pad adjusters.
I found using cable tension to adjust for pad wear didn't work very well.

Yeah, I can believe it's not quite the same as adjusting the pistons. Easier, though 🙂

Bought a bike from Wheelies a couple of years back, had the mechanical discs upgraded.

First time I ever had clipless pedals as well, riding around my housing estate, first go on the bike, pedalled up the small hill, and rolled down the road, pulled the brakes on coming up to the junction, to have them pull through, with me clipped in for the first time.

Managed to avoid being hit by my neighbour, and bounce onto the grass verge.

Friday afternoon bike.

Coming from a shop mechanics point of view
at this 10week point have you had a first free service on the bike? At this point cable strech should be adjusted and brakes reset
how often to you do a bolt check on the bike?
how many times in this 10 weeks have you used you brakes? (Probably more than you think)
Id have a word with original retailer or local shop if was an online store and have them inspect the bike.
it seems odd that both would go at the same time

First time I ever had clipless pedals as well, riding around my housing estate, first go on the bike, pedalled up the small hill, and rolled down the road, pulled the brakes on coming up to the junction, to have them pull through, with me clipped in for the first time.

For the OP however when things like brakes start to go wrong stop and check 🙂

This is essentially a brand new bike don't forget, with the owner apparently never doing any adjustments

10 weeks old, so depends hugely on rider mileage and conditions. I'm doing ~150 miles a week (commuting + recreational); the pads had lasted the best part of a year with minimal adjustment, then a wet December killed them in short order.

Could be pad wear depending on conditions.
He says mud and the pads in Spyres don't last long.
Rode my TCX for a few months and then one muddy training session in October killed the pads in an hour!
Rode home with no brakes!
Swapped to Swiss Stop sintered and no issues since.
Max