Mechanical Discs - Rubbish?

glasgowbhoy

I have a CX bike set up for the road. It has TRP Spyre mechancial discs. I've let them bed in, the pads are fine and the discs clean. They have hardly any power though and on downhill roads where I have to stop at lights they barely allow me to stop before I run through the junction. a the moment they are worse than rim brakes.
Any tips?

meanredspider

Well, mech discs clearly aren't rubbish and many people swear by Spyres. I've not used them but I have used BB5, BB7 and HyRds.

The only thing I can think, from what you describe, is that the pads aren't being fully applied to the discs. Have you checked that they are both square to the disc and applying full pressure? Other than that, I can only assuming that there's something wrong with the pad material (contaminated, for instance).

I have to question if you've truly bedded the pads in properly too. To have done this, you needed to have worked them so to get the disc pretty hot. With the performance you describe, that sounds unlikely that it was even possible.

glasgowbhoy

meanredspider wrote:

Well, mech discs clearly aren't rubbish and many people swear by Spyres. I've not used them but I have used BB5, BB7 and HyRds.

The only thing I can think, from what you describe, is that the pads aren't being fully applied to the discs. Have you checked that they are both square to the disc and applying full pressure? Other than that, I can only assuming that there's something wrong with the pad material (contaminated, for instance).

I have to question if you've truly bedded the pads in properly too. To have done this, you needed to have worked them so to get the disc pretty hot. With the performance you describe, that sounds unlikely that it was even possible.

Cheers, to work them I take it they need to be used quite a bit in the lead up to a hard fast stop?
I'm not sure there is anything wrong with the allingment of the pad. I had the bike shop check them. The discs have been cleaned with disc brake cleaner but there's just no 'bite' even with the levers pulled really tightly

meanredspider

Yes - the best thing is to bed them in on a long descent: get up a good pace and then brake hard (on one disc only) without ever stopping the wheel. Then back up to speed and repeat around 10x or more. The disc should get properly hot. If, as might be the case, you've glazed the surface of the pad a bit, whip them out and rough them over with some emery cloth (or sandpaper) before doing the bedding in. Discs take a little work to bed in but then they should be great and you you'll almost never need more than the front brake.

Manc33

If you're using MTB v-brake levers on road calipers, thats why.

MTB brake levers only have half the leverage of flat bar road levers.

These are the highest spec ones I know of (got them myself):
http://www.chainreactioncycles.com/shim ... lsrc=aw.ds

Those + Salmon pads + DA 7800 calipers = you're stopping in all conditions.

The R780 brake levers are useful because they are switchable between v-brake and road brake.

I know that applies to rim brakes but it has to apply to discs too because its the levers that are different.

glasgowbhoy

Manc33 wrote:

If you're using MTB v-brake levers on road calipers, thats why.

MTB brake levers only have half the leverage of flat bar road levers.

These are the highest spec ones I know of (got them myself):
http://www.chainreactioncycles.com/shim ... lsrc=aw.ds

Those + Salmon pads + DA 7800 calipers = you're stopping in all conditions.

The R780 brake levers are useful because they are switchable between v-brake and road brake.

I know that applies to rim brakes but it has to apply to discs too because its the levers that are different.

It's the 105 disc set up that the CX bike came with a few weeks ago. That wont be the problem

glasgowbhoy

meanredspider wrote:

Yes - the best thing is to bed them in on a long descent: get up a good pace and then brake hard (on one disc only) without ever stopping the wheel. Then back up to speed and repeat around 10x or more. The disc should get properly hot. If, as might be the case, you've glazed the surface of the pad a bit, whip them out and rough them over with some emery cloth (or sandpaper) before doing the bedding in. Discs take a little work to bed in but then they should be great and you you'll almost never need more than the front brake.

Great thanks, I've certianly not done that amount of brakin on them yet.

Manc33

Watch out when it suddenly does bite. :P

The ones I had years ago became a lot more powerful once that layer wore off.

earthvspace4XTuUWcX

I have TRP Spyres, absolutely fine from the off, didnt even seem to require bedding in.

ugo.santalucia

IME it takes a few sharp squeezes to build up the necessary "pad dust" on the rotors and get good action. That typically means 10 minutes in traffic or a lot more if you ride and don't brake. That said, you might have badly installed callipers.

mrdsgs

1. pads properly centred over rotors, check by eye, not just by sound, to ensure no rotor deflection.
2. compressionless outers.
3. cable inners clamped to ensure no play at all at levers, check pad movement by eye.
4. re-set calipers with wheel off by gently squeezing levers so that pads are as close as possible to rotor on wheel re-fit.

all of the above assumes rotors are true and pads are deglazed with a metal file, not just squirted with brake cleaner.

How Far is too Far

I have in the past found brake cleaner to leave a residue. I now dont bother with it and just give both the pads and rotors a quick rub over with some fine sand paper and I have not had a problem since. Also be carefully if you are using GT85 near the rotors and callipers it can take a while to burn of any contamination.

veronese68

As in the above post I'd worry about what disc brake cleaner was used. Car disc brake cleaner leaves an oily residue that will knacker your pads. Only use isopropyl alcohol if you really need to clean your discs.
I used to have BB7 with 105 levers and they worked a treat. If you can physically pull the lever back to the bar there may be some improvement in adjustment to be had.

Semantik

Veronese68 wrote:

As in the above post I'd worry about what disc brake cleaner was used. Car disc brake cleaner leaves an oily residue that will knacker your pads. Only use isopropyl alcohol if you really need to clean your discs.
.

Really? So it leaves an oily residue on car discs, pads and calipers?

Who would ever buy the stuff then?

veronese68

Cars are much heavier with much more powerful brakes so they can burn it off quickly. Car discs are cast iron and will rust very quickly. Bicycle brakes are far more susceptible to contamination.

ravey1981

I have bb5s and they work brilliantly for what they are. They are on a cx bike that goes off road as well as on road though so bedded in very quickly. One tip from bedding in MTB brakes over the years is take a waterbottle and wet the disc, then brake hard a few times, doesn't have to be at high speed but as hard as you can without locking the wheel. Do this a few times and braking should be much better. Also, actually put mud onto the disc and then brake (yes I have mixed up mud in a tub and done this, sand works a treat!) and do the same. Wash off with clean water afterwards obviously.

luv2ride

I had the exact same issue with my TRP Spyes a few weeks ago, made for some scary descents (and sore hands from pulling the levers so hard to get any kind of braking at all). Had been careful to bed them in and thought I'd been careful in not contaminating the discs or pads. Have now changed the discs to these:
http://www.chainreactioncycles.com/sram ... prod120149
and the pads to these:
http://www.chainreactioncycles.com/nuke ... -prod42157

Things are now improved but still not to the point that they seem worthy of all the praise they get - they've been pretty fiddly to set up and seem to require frequent adjustment. By comparison, was out on my carbon roadie today with SRAM Force rim brakes which seemed much better, lighter lever feel and with great modulation :?

New cables and outers will be my next move but, whilst they're okay, mine aren't great.

glasgowbhoy

I washed the discs in hot soapy water then gave the discs and pad a light sanding with paper.
Tried them out on Saturday morning and the braking has improved dramatically.
I think my liberal application of GT85 on the moving parts, especially in the winter, has got on to the discs and left a Greasy residue which meant no grip for the pads.
Cheers

veronese68

Pleased to hear it, they may improve further as they wear and clean up more. If you read the MTB Workshoo section people are almost evangelical about not using things like GT85 as even if you are careful it's hard to avoid contaminating discs. If you must use it take the wheels off and cover the caliper a or remove the pads first.

ugo.santalucia

WD40 and GT85 should never get close to a bicycle... they are not products for cycling

cycleclinic

Here her Ugo well said. Car disc brake cleaner in my experience does not affect braking performance although I do find disc rotors don't need cleaning much but I had too on my hyrd when they squealed on the first ride, cleaned and sanded the disc and pads and all is fine now.

Compressionless brake outer like jagwires road pro xL set is a very good idea.

Manc33

ugo.santalucia wrote:

WD40 and GT85 should never get close to a bicycle... they are not products for cycling

Funny you mention that because I saw a guy from "Global Cycling Network" spraying that stuff near his rim brakes on a cleaning video only yesterday. The same guy degreased the chain while it was on the bike because he doesn't like breaking the chain too many times. I thought degreaser getting inside the bottom bracket shell would be worse but what do I know.

darkhairedlord

Manc33 wrote:

....... but what do I know.

:shock: