Cycling UK Forum

You have worn right through the friction material, now you are grinding away at the metal backing, and also of course the disc.

I'm a very late adopter of disc brakes, but I believe the friction material is bonded onto the backing (not riveted) and you are recommended to fit new pads while enough friction material remains to stop the heat from braking melting the bond.

i imagine the brake is coming to the end of its travel (over-camming, as before) and releasing the disc

offroader wrote: ↑3 Jan 2023, 2:19am
Note. The Avid BB calipers use the same principle but work slightly different. The balls sit in dimples machined into the caliper body. The actuator arm is directly attached to the piston which has ramps machined on the back. Operation is the same but you'll see that the actuator arm moves in and out in the caliper body as it rotates

Over camming happened in bad designs when the actuator can rotate far enough for the balls to fall off the end of the ramps

Ah! I have only ever used BB7s, and therefore only ever stripped BB7s

....I couldn't see how they could "go over" because there isn't an "end" of the ramps for the balls to fall off.! Thanks for the explanation!

Does sound like over-camming.... as Colin and others have advised.

I've had this on TRP Spyres before I realised you should use the pad adjusters to allow for pad wear rather than using the barrel adjuster and/or adjusting brake cable. Need to make sure actuator arm does not travel too far.

It's a very alarming noise, although I think yours is louder than I had on the Spyres. When watched closely, it was very obvious that one pad jumped back away from the disc when it went PING. Since using the pad adjusters ... and being mindful of brake actuator arm travel/ position when setting up/ adjusting....no more pings and brakes fine.

Good luck with sorting it.

I may have missed it, but it doesn't look like anyone has linked to the user setup manual yet:

https://s3.us-east-1.amazonaws.com/prom ... _V1_EN.pdf

As the consensus seems to be 'over camming' then the last paragraphs under 'Ongoing maintenance' look to be the most relevant. If the inboard pad has never been tightened then that would surely lead to the over camming and limited remaining movement for actuator arm problems. Given the seriousness of the problem I'd be getting the pads out to check them, and then going through the whole alignment and cable setup procedure.

531colin wrote:

slowster wrote: ↑2 Jan 2023, 4:54pm I think it may be over camming, as described in these two posts:

viewtopic.php?p=664618#p664618

viewtopic.php?p=626367#p626367

I haven't found any information on how the things actually work?

It's quite a simple system common on cable operated motorcycle clutches. My 1970s Honda had the exact same system to operate the clutch pushrod so it's certainly not something Avid invented

The actuator arm is attached to a disc with a number of ramps on it. As the actuator arm moves the disc rotates and the ramps move along.
The moving piston has a corresponding number of ball bearings sitting in dimples. The piston is not round so is held at a fixed angle in the caliper body where the balls sit at the bottom of the ramps on the actuator disc in the rest position.
When the actuator is rotated the balls effectively climb up the ramps as the piston doesn't rotate. This pushes the piston and actuator apart giving you the piston action


Note. The Avid BB calipers use the same principle but work slightly different. The balls sit in dimples machined into the caliper body. The actuator arm is directly attached to the piston which has ramps machined on the back. Operation is the same but you'll see that the actuator arm moves in and out in the caliper body as it rotates

Over camming happened in bad designs when the actuator can rotate far enough for the balls to fall off the end of the ramps

531colin wrote: ↑2 Jan 2023, 5:18pm

slowster wrote: ↑2 Jan 2023, 4:54pm I think it may be over camming, as described in these two posts:

viewtopic.php?p=664618#p664618

viewtopic.php?p=626367#p626367

I haven't found any information on how the things actually work?

It has never happened to me and I don't have the experience of having dismantled a caliper. From the descriptions I have read I take it that with some designs of caliper there is a point at which the ball bearings on the ramp which push the piston, reach the design limit of their movement/range, and any further movement as a result of excessive cable pull/overly worn pads will result in a *loss* of pressure/force against the piston, and the piston springing back.

slowster wrote: ↑2 Jan 2023, 4:54pm I think it may be over camming, as described in these two posts:

viewtopic.php?p=664618#p664618

viewtopic.php?p=626367#p626367

I haven't found any information on how the things actually work?

I think it may be over camming, as described in these two posts:

viewtopic.php?p=664618#p664618

viewtopic.php?p=626367#p626367

slowster wrote: ↑17 Sep 2022, 11:06pm

Cugel wrote: ↑17 Sep 2022, 6:00pm One tool at a time, then ....

Before even buying one tool, for tools like cassette/Centrelock disc lockring tools and bottom bracket tools I suggest you consider the pros and cons of tools with integral handles vs. those designed to be used with torque wrenches, large sockets and/or large adjustable spanners.

I would not get tools with handles because:

- they don't allow a torque wrench to be used
- it's usually possible to choose separate tools which can be firmly held in place with a QR skewer to stop them camming out
- separate tools give better options with a stuck or seized BB or lockring, e.g. adjustable spanners with a longer handle (or handle extended with a metal tube) or a breaker bar.

If you get separate tools, it makes sense where possible to choose ones which use the same drive and eternal hex sizes, so that you do not need multiple sockets, adapters, or both 3/8" and 1/2" torque wrenches, breaker bars etc. .......

That all sounds like very good advice. Those tools I have for bike work that have built-in handles rarely have those handles well-designed for their task of applying the necessary forces. They aren't offset so foul the gubbins in which the part is on when trying to loosen or tighten; they have a shape or edge that digs into the hand so that applied force is restricted by resultant discomfort in using them. And so forth.

These days, the issue of torque is more prominent, with lightweight or minimal-material designs needing careful spannering if the part isn't to break. I do have small and large torque wrenches that come with various included driving-socket sizes so I suppose the obvious thing is to look for tooling to fit them, as you and Jonathan suggest.

*********
One issue with such tools is that they come designed for use on a particular kind of bike part but their interface (of splines or other shape) to the bike part to be loosened or tightened is adopted for other kinds of bike parts. One must be careful, if both kinds of parts need working on, to make sure the tool will fit both.

For example, I have 20-spline tool with a 1/2" drive socket that's designed to loosen square taper bottom bracket cups but which, in theory, can also be used to loosen a 20-spline spider used between a Fazua FSA ISIS splined axle and various chaintings of different OLN dimensions. But the tool can't be used to loosen these spiders because the inner recess isn't large enough to take the ISIS axle end. It only has space to take a smaller square-taper axle end.

So I need a different version of this 20-spline driver with a much larger inner recess so it'll go over an ISIS axle end and still engage with the splines of the FSA-Fazua spiders. Happily Icetoolz seem to have one.

*********
Next tool for consideration - the chain whip.

I have a cheap one from the 30-quid bike toolbox and it does work .... but .... the chain links are fat (for 6 or 7-speed sprockets, probably) and the thing has an uncomfortable handle that's also difficult to hold on to the cassette properly. It's one of those where it becomes all too easy to slip and get a sprocket-tooth bite on your knuckles. I'm wondering if this differently-designed item is any better?
I have a matching splined tool for the cassette lock ring but this too has a "bad" handle so perhaps I should also get a handleless version for use with the torque wrench?

Cugel

Chain Whip

I needed to buy a new one this year because I damaged the old one attempting to remove a Rohloff sprocket carrier (I found out the hard way that there is a specific technique which needs to be followed).

I bought a Park Tool SR-2.3 because it was generally well regarded, e.g. by Brucey (viewtopic.php?p=1179796#p1179796), and is a similar design to the one 531colin has - viewtopic.php?p=1572648#p1572648.

Pedal Spanner

I also bought a Park Tool PW-4 pedal spanner, specifically because it has two spanner openings at different angles. It makes a big difference to be able to vary the angle of the grip to the crank. Obviously it only makes sense to get such a spanner if you use pedals with spanner flats.

Cassette Lockring Tool

Between them Shimano and Park Tool offer various different types, i.e. with and without guide pins, with a handle, with a 3/4" socket fitting etc. Which is best depends upon what components your bikes have. NB Some Centrelock brake discs use a similarly splined lockring, and I think that not all cassette lockring tools are a good fit on the Centrelock lockrings, and that those suited to the Centrelock lockrings may be less than ideal for the cassette lockrings.

My preference is for the basic Park Tool version (FR-5.2) without a guide pin, through which a quick release skewer can be passed to hold the tool in place and prevent it camming out. I also have a deep socket which I can use with a 3/4" drive torque wrench to tighten the lockring:

https://www.lawson-his.co.uk/iss-0616l- ... ct-p160217

Cugel wrote: ↑17 Sep 2022, 1:47pm That TOBE chainring slotted bolt tool looks good. I hate the wee spanner-like things with two prongs, that slip out as soon as you try to seperate the front and back chainring bolts.

Having tried that type, I prefer the old fashioned type. That is because I have found that with cranks like Spa's TD2, the flat tool can usuallly be positioned so that it is held in place and stopped from rotating by part of the inside face of the crank, with just my thumb lightly over it. With the nut thus held in place, it is easy to undo or tighten the bolt with an allen key.

As for disc brake tools, I am somewhat sceptical of some of them, and have held off buying any. Although Park Tool make a specific tool to push pistons back, in at least one of their videos I've seen them using the blue plastic coated handle of a cone spanner to push the pistons back.

There are a lot more threads and posts on disc brake tools for truing discs and aligning the calipers on Singletrackworld, so I suggest you search for those threads and weigh up the competing recommendations on there before making a purchase.

De Sisti wrote:Would you recommend this one?
https://www.ebay.co.uk/itm/Bottom-Brack ... SwTkVeNTba

I wouldn't. I have the VAR tool upon which the workshop one is based (image below). It only engages for 1mm-2mm depth in a new UN55 cup, because the tool's splines are slightly too wide. I think that may be because Shimano might have changed the dimensions of the cup splines at some point over the last 25 years. Other BB manufacturers also use the Shimano pattern, and I suspect there may be slight variations between them all, such that the VAR tool might be a perfect fit for one or more non-Shimano BBs.

My VAR tool is over 20 years old, and I would hope that by now VAR had changed the dimensions of their tools to be a better fit for Shimano cups, but I see no point in spending more of my money on a second VAR tool to find out, when I can buy a tool made by Shimano themselves and given that Shimano's tools have a reputation for being good quality. That is why I bought the Shimano TL-UN54 tool and a Pedros holder.

The TL-UN54 goes into a UN55 cup to the full depth of the cup's splines, and there is no noticeable play or slop. I suggest that before attempting to use the FWE tool again in the damaged cup (with or without the Pedros tool), you insert it in the cups of your Dolan and/or Spa Audax to assess the depth and quality of engagement: if there seemed to be anything less than good engagement, I would stop using it and buy a TL-UN54. If however the engagement is good, that would suggest that the damage to the cup was caused by camming out, which the Pedros holder tool should prevent happening in future.

De Sisti wrote:I'm just about to order one. I'll have to learn how to use it 'on the job'

All that it does is hold the BB tool in place firmly and squarely, preventing camming out. The tool looks complicated because it is double ended: the end with an M15(?) thread fits Octalink/ISIS BBs and the other end fits square taper.

Incidentally, the hole in my TL-UN54 tool is 22mm in diameter, because it is sized to fit over Octalink axles as well as square taper axles, and the outside diameter of the round nut on my holder tool is 20mm, so a large washer is still needed with that particular combination for the nut to bear on the tool.

Brucey wrote:apologies if this is obvious but the tool I pictured above doesn't need a centre piece to stop it from camming out; once fitted with an extension of some kind in the 1/2" drive, the tool becomes symmetric and doesn't want to cam out
cheers

That tool is just about within the limits of what I'd be prepared to pay for a decent ht2 tool if I needed one to remove difficult bbs. I really like the unior but can't imagine ever shelling out £65 for one. I do like a lot of Unior tools though, I think many are better designed and nicer to use than Park. They are designed and made in Slovenia, I recently found out! In USA they can't use blue handles because of Park, so they're orange and red over there!

Thanks for this most helpful post, Grahm I found this board when searching for this info, and used it to fix my sticking brake. It is now working better than when new! Like you, I initially exacerbated the problem by trying to disassemble the brake without removing the star washer. I was able to bend the spring with a pair of channel-lock pliers (not sure what they are called on your side of the pond...these: http://www.northerntool.com/images/prod ... 888_lg.jpg ) and restore tension. Here are some notes others may find helpful:

After removing the star washer on the pivot, the top shoe will come off the pivot. Slide that shoe down off and past the cam which will de-tension the spring. Then you can easily remove the other shoe. Reverse this to re-assemble. When re-assembling, leave the cam followers off the shoes intially, which will help avoid over stretching the spring. After the shoes are in position and the star washer is installed, you can carefully slip the cam followers into place, and lube the camming surfaces. I lubed the cam shaft bearing with my favorite Phil Wood waterproof bicycle grease. On the pivot and cam surfaces I sparingly used Hondalube-60. This is a 60% molybdenum-disulphide extreme pressure grease available from Honda motorcycle shops...perfect for brakes and splined shafts. Very low migration and still provides low friction after it eventually dries out. I also used a tiny dab of the HL60 on the ends of the spring...likely pointless, but can't hurt.

THE CAM Is the motion not the mecanical lock .. the camming action leads to an over centre lock situation.. feel it as you push the wheel spindle lever .. a rise in force..camming action, .. then a drop in force as the over centre lock happens...