No stopping power on my disc brakes

For discussions about bikes and equipment.
mnichols
Posts: 1463
Joined: 22 Apr 2013, 4:29pm

No stopping power on my disc brakes

Postby mnichols » 3 May 2019, 9:06pm

I can't get any stopping power from my TRP Sphyre brakes with Uber Sintered Brake Pads, SRAM Rotors on 105 levers

Getting a good pull on the levers, cables are fine, pads are adjusted and locked on to the rotors, but I can still rotate the wheel by hand

Rotors have been cleaned with alcohol, new pads, cables are good. Have taken to LBS but they are having the same issue.

Any suggestions?

User avatar
RickH
Posts: 5321
Joined: 5 Mar 2012, 6:39pm
Location: Horwich, Lancs.

Re: No stopping power on my disc brakes

Postby RickH » 3 May 2019, 9:58pm

Here are a few questions & thoughts.

Has this setup been working previously?

When you say the pads are locked onto the rotors are you sure? Could it be the actuator arm is running out of travel before the pads reach the rotor? You should be able to operate the actuator directly by hand to check if it is working & bypass a cable problem.

If so then either the cable adjustment or the pad adjustment (or both) may not be right.

Are the cable outers located in their stops properly?

Does the actuator arm go all the way back to its "brakes off" end stop? If not you can end up running out of travel before the pads reach the rotor.

Are the pads new? They should still work but not be very good until you have bedded them in with some "hard as you can" braking (in a safe location).

My rule of thumb on pad adjustment (in the absence of specific information & assuming straight rotors) is to adjust them in until they just start to catch & then back them off a notch.

Can you get braking resistance by adjusting the pads in as far as you can.

Brucey
Posts: 42858
Joined: 4 Jan 2012, 6:25pm

Re: No stopping power on my disc brakes

Postby Brucey » 3 May 2019, 10:19pm

what makes you think the cables are "good/fine" ? Many times I have heard this said of cables that barely moved, and robbed at least 50% of the brake force.

You report that the wheel (singular) can be moved by hand. Does this mean you have the problem on one brake only? You say you have 105 STIs, but which model are they?

General problems could include that

- the brakes could be contaminated
- the brake pads are not centred over the brake track
- the cables could be very draggy under load (but move freely enough to seem OK when not under load)
- the pads are not yet bedded into a (slightly worn) disc

Known problems with spyres include

- the caliper thrust bearings corrode and this reduces the brake force
- if the ball bearings come displaced in the ramp mechanism (either side), the brake won't work properly
- if the ramp mechanism has no grease on it, it won't give as much brake force as it should do
- if the pad adjustment screws are not set correctly both sides, the disc can be pushed to one side when the brake is applied
- the maximum brake force is only developed when the arm is orthogonal to the cable
- the pad adjustment screws are notorious for not holding their adjustment
-

There's basically no sealing on the mechanism(s) in the caliper. IME, if you ride in the weather, and the calipers (especially the rear caliper) are not overhauled, it is practically guaranteed that the thing will be a corroded mess inside after a year or two.

If you want to see what the insides look like

https://singletrackworld.com/forum/topic/psa-trp-spyre-rebuild-guide/

https://thebottomgear.co.uk/servicing-trp-spyre-brakes/

but in the absence of any obvious problems I wouldn't bother doing anything to the calipers until I'd replaced the cables.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

mnichols
Posts: 1463
Joined: 22 Apr 2013, 4:29pm

Re: No stopping power on my disc brakes

Postby mnichols » 4 May 2019, 8:33am

Thanks. The bike is now at the LBS, and i cant get to it until after the Bank Holiday, so I'll forward this on. BTW, both front and back brakes are doing the same. Next step seems to be change cables an outers and check for corrosion.

Brucey
Posts: 42858
Joined: 4 Jan 2012, 6:25pm

Re: No stopping power on my disc brakes

Postby Brucey » 4 May 2019, 9:23am

further to the above, a close relation to the 'not yet bedded in' problem is the one of disc to caliper alignment.

The Spyre brake (unlike BB5/BB7) has little in the way of allowance for any misalignment, and the pads that are supplied originally are pretty soft. This means that the brake normally beds in fairly quickly even if the caliper is slightly out of line with the disc.

However if the new pads are hard-wearing (which sintered metal ones ought to be) and the caliper is misaligned, it may take a while for the brake pads to wear at an angle that matches the caliper misalignment. Until this happens you can expect the brake to be pretty feeble.

The cure for this is to check and correct any caliper misalignment e.g. by using a disc mount facing tool.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

gregoryoftours
Posts: 1455
Joined: 22 May 2011, 7:14pm

Re: No stopping power on my disc brakes

Postby gregoryoftours » 4 May 2019, 9:36am

Brucey wrote:further to the above, a close relation to the 'not yet bedded in' problem is the one of disc to caliper alignment.

I have a set of these where the pistons are not completely parallel to each other which is very annoying as it obviously means that it takes time to get reasonable pad contact. They're still not great. I'm really not impressed with Spyres and wish that I'd bought bb7 instead.

gregoryoftours
Posts: 1455
Joined: 22 May 2011, 7:14pm

Re: No stopping power on my disc brakes

Postby gregoryoftours » 4 May 2019, 9:40am

By the way I've found using compressionless outers is needed with these brakes. If your Spyres have only stopped working properly after changing pads I would say that pad contact with the rotor is the most likely issue due to one or more of the factors mentioned in the comments above. Calipers aligned slightly off square to rotor, wonky pistons, worn brake track on rotor. Hard pads will take longer to wear down to a profile that gives greater contact area, this could potentially take a long time.

nsew
Posts: 721
Joined: 14 Dec 2017, 12:38pm

Re: No stopping power on my disc brakes

Postby nsew » 4 May 2019, 10:26am

I happened across a cyclo-tourist from the Ardennes the other day. On his way to Provence. Chap was dressed the part, road a decent trekking Gitane with a tidy pack. He had invited me to to a roadside dinner of noodles Alsace sausage and Parmesan. As he stated he was a chef I took him up on his offer. While he prepared the meal I looked over his bike, as you do. Neither brake had any purchase. I looked around at this fella and he sheepishly motioned to his feet as a means of stopping a loaded bike. So don’t worry about it.

(nb yes I fixed his brakes up though was concerned about the upcoming food)

Brucey
Posts: 42858
Joined: 4 Jan 2012, 6:25pm

Re: No stopping power on my disc brakes

Postby Brucey » 4 May 2019, 3:43pm

gregoryoftours wrote:
Brucey wrote:further to the above, a close relation to the 'not yet bedded in' problem is the one of disc to caliper alignment.

I have a set of these where the pistons are not completely parallel to each other which is very annoying as it obviously means that it takes time to get reasonable pad contact. They're still not great. I'm really not impressed with Spyres and wish that I'd bought bb7 instead.


I've not noticed that particular problem but I am not surprised that it can occur; by contrast the BB5/7 designs include

a) swivelling mounts (on the 'post mount' screws) to allow the caliper to be aligned to the disc and
b) an articulated 'foot' on the moving piston so that small variations in pad wear/parallelism are tolerated.

The flaws in the BB5/BB7 design include that the fixed pad adjuster can seize up, or crud in the threads may prevent you from screwing it in as the pads wear. The BB5 design only doesn't wear the pads to a taper if the pads are faithful copies of the OEM design, i.e. with handed pads, with asymmetric friction material, so that the piston centre is not at the centroid of the friction material.

But the great virtue of the BB5/BB7 design is that it is very simple and can be overhauled fairly easily. The mechanism contains just four ball bearings, whereas the Spyre/Spyke design contains over 40.... :shock:, isn't weatherproof and and it is isn't meant to be user-serviceable. The big selling point of the spyre is that the brake might be more powerful than a BB7 because it has two moving pistons. This is basically a COS; anyone who has used both brakes (when set up correctly) can tell you that in that regard there isn't a signficant difference between them.

The spyre has (accidentally) one significant advantage; if the rear caliper is seatstay mounted, it is less likely to interfere with a rack mounting, because it sticks out less.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

mnichols
Posts: 1463
Joined: 22 Apr 2013, 4:29pm

Re: No stopping power on my disc brakes

Postby mnichols » 4 May 2019, 9:04pm

Brucey wrote:
gregoryoftours wrote:
Brucey wrote:further to the above, a close relation to the 'not yet bedded in' problem is the one of disc to caliper alignment.

I have a set of these where the pistons are not completely parallel to each other which is very annoying as it obviously means that it takes time to get reasonable pad contact. They're still not great. I'm really not impressed with Spyres and wish that I'd bought bb7 instead.


I've not noticed that particular problem but I am not surprised that it can occur; by contrast the BB5/7 designs include

a) swivelling mounts (on the 'post mount' screws) to allow the caliper to be aligned to the disc and
b) an articulated 'foot' on the moving piston so that small variations in pad wear/parallelism are tolerated.

The flaws in the BB5/BB7 design include that the fixed pad adjuster can seize up, or crud in the threads may prevent you from screwing it in as the pads wear. The BB5 design only doesn't wear the pads to a taper if the pads are faithful copies of the OEM design, i.e. with handed pads, with asymmetric friction material, so that the piston centre is not at the centroid of the friction material.

But the great virtue of the BB5/BB7 design is that it is very simple and can be overhauled fairly easily. The mechanism contains just four ball bearings, whereas the Spyre/Spyke design contains over 40.... :shock:, isn't weatherproof and and it is isn't meant to be user-serviceable. The big selling point of the spyre is that the brake might be more powerful than a BB7 because it has two moving pistons. This is basically a COS; anyone who has used both brakes (when set up correctly) can tell you that in that regard there isn't a signficant difference between them.

The spyre has (accidentally) one significant advantage; if the rear caliper is seatstay mounted, it is less likely to interfere with a rack mounting, because it sticks out less.

cheers


If they aren't weather proof or serviceable do i need to replace them?


PH
Posts: 9948
Joined: 21 Jan 2007, 12:31am
Location: Derby
Contact:

Re: No stopping power on my disc brakes

Postby PH » 4 May 2019, 11:22pm

mnichols wrote:
These seem cheap

They are, but you'll need the road version to work with your levers, Ebay is still a good place to search for them, but they are usually a bit dearer.

Brucey
Posts: 42858
Joined: 4 Jan 2012, 6:25pm

Re: No stopping power on my disc brakes

Postby Brucey » 4 May 2019, 11:23pm

mnichols wrote:
If they aren't weather proof or serviceable do i need to replace them?


if the weather hasn't yet penetrated the workings there is arguably no necessity to change.

If you do change I think you would be better off with 'road' calipers to use with road levers, not MTB versions.

FWIW Paul's klampers are made with three different MA values to suit different levers; NSSLR ratio levers really need a caliper MA that is between the usual 'road' and MTB ones.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Eyebrox
Posts: 356
Joined: 5 Aug 2015, 8:56pm
Location: Ayrshire

Re: No stopping power on my disc brakes

Postby Eyebrox » 4 May 2019, 11:34pm

You can get 2 x Spyre calipers for £70. I have used both Spyre and BB7 on the same bike. The Avid caliper lasted twice as long - three years - as the TRP one. The crud eventually got to the Avid rear brake and it stopped working. The Spyre rear brake seized on one side then on the other side. Both pistons wouldn't move with a 3mm hex key. I renewed the cables (changing to compressionless) and fitted a new caliper. The brake now works perfectly ... but for how long? I fear I might get through the winter then have to replace the caliper again. I reckon the BB7 has the edge because the caliper body allows you to get in about it to clean out the workings. Plus you only have one piston to worry about. The cabling certainly helped.

pyruse
Posts: 55
Joined: 6 May 2011, 5:35pm

Re: No stopping power on my disc brakes

Postby pyruse » 9 May 2019, 10:50am

The more I read about disc brakes the more I wonder what is wrong with rim brakes! They always seem to work fine and are easy to fix.