Are cable disc brakes really this rubbish?

andyeb

Today I test rode an Arkose 3 2015, with Avid BB7 cable disc brakes. Overall I like the bike.

However, the braking performance was inferior to my summer road bike with 105 rim brakes and greatly inferior to the stopping power of my entry level hydro brakes on my 29er (Voodoo Bizango).

I also test rode the Arkose 4 2015, which has Shimano BR-RS685 brakes and I was impressed by the stopping power available.

I was perhaps expecting that cable discs would be somewhere in between cable rim brakes and entry level hydro MTB brakes.

Are all cable disc brakes really this bad? I wouldn't say the stopping power was really adequate. However the Arkose 4 is beyond budget, even in the sale .

Or are my expectations simply unrealistic?

meanredspider

Well, of course they aren't! Had they been properly adjusted and had a proper bedding in run? From what you describe (as someone who has ridden mechanical discs on road bikes for over 5 years) neither has been done. They won't be as good as hydro discs in the same application but way better than rim brakes - especially in the wet. Whenever I jumped onto my rim-braked bike, I had to entirely adjust my braking expectations.

jds_1981

No they are not. So need some maintenance to keep in good condition. I find performance drops if I don't keep my pads well adjusted.

bendertherobot

BB7's are getting on now. They are nowhere near as good as, IMO, Trp Spyre or, notably, TRP Hy Rd. But they are still good and should have loads of power when setup properly.

andyeb

Braking performance of the BB7s has steadily improved as they have bedded in. But I need to adjust to get rid of the squealing.

On_What

My BB&s scream when wet, it's embarrassing using them

ugo.santalucia

On_What wrote:

My BB&s scream when wet, it's embarrassing using them

But that's friction between the pad and the rotor, what's it got to do with the caliper? Try different pads... ultimately in the wet they all honk

tgotb

Ultimately, a disk brake is doing exactly the same as a rim brake. You have a spinning metal object, and you clamp something onto it to create friction. Why some people assume disk brakes are going to solve all their problems, and other people believe that disk brakes somehow have magic stopping powers, is beyond me.

Remember when we were all kids, rims were chrome, brake pads were leather (if you were lucky) and brakes basically didn't work in the wet? Now we all have alloy rims, fancypants SwissStop pads, and rim brakes are great; funny thing is, they're basically doing the same thing as the brakes that didn't work 30 years ago, but subtle improvements in design and materials have made them a whole lot better.

Disk brakes are the same. Some are great, some are pants. Pads are made from a huge variety of materials. Calipers all work differently. Disks all look like they're made from the same material to me, but I'm probably wrong. Some disk brakes are great, some are going to be sh*t. A good caliper brake's going to be way better than a crap disk brake. Given the fact that some caliper brakes are woeful, is it any surprise that some disk brakes are the same?

meanredspider

Ref the squealing, has anybody tried some copperslip on the BACK (that's the BACK! - don't want some muppet killing themselves) of the pad? Some cars have had terrible trouble with screaming brakes (Fiat Coupe is one) and one solution was just this - or shimming them with material between the backing and the piston.

On_What

Copperslip does work, the other thing we do on cars is to champfer the front edge of the pad. The BB7 is a good caliper but the fixed pad I think creates a lot of issues. If the caliper was floating so that the disc did not bend then it would be a far better design, obviously at extra cost. Spyres look good but I've not got the cash for a pair right now. FYI my BB7s scream over and above any others I've seen before. They have the OEM pads, and are setup correctly.

ugo.santalucia

meanredspider wrote:

Ref the squealing, has anybody tried some copperslip on the BACK (that's the BACK! - don't want some muppet killing themselves) of the pad? Some cars have had terrible trouble with screaming brakes (Fiat Coupe is one) and one solution was just this - or shimming them with material between the backing and the piston.

That removes some noises related to pad vibration, but not the honking in the wet

veronese68

What actually causes the honking in the wet? I'd have thought it's a vibration of some sort, just a different frequency. But it does vary according to pad material.

fenix

Mate isn't happy with his disks at all. To begin with they were awesome - but by the end of the first ride they were crap.

We compared last week. My crappy cantilever brake vs his, Front wheel only. Mine stopped in 1/2 the distance of his.

He's looking into it - but its a whole new area to explore - after using rim brakes for decades - its possibly easier staying with rim brakes than having to faff with discs and learning what works or what pads to use etc...

6wheels

meanredspider wrote:

Ref the squealing, has anybody tried some copperslip on the BACK (that's the BACK! - don't want some muppet killing themselves) of the pad? Some cars have had terrible trouble with screaming brakes (Fiat Coupe is one) and one solution was just this - or shimming them with material between the backing and the piston.

Might be worth putting some on the back face of the disc as well, or use baking paper.

bendertherobot

Fenix wrote:

Mate isn't happy with his disks at all. To begin with they were awesome - but by the end of the first ride they were crap.

We compared last week. My crappy cantilever brake vs his, Front wheel only. Mine stopped in 1/2 the distance of his.

He's looking into it - but its a whole new area to explore - after using rim brakes for decades - its possibly easier staying with rim brakes than having to faff with discs and learning what works or what pads to use etc...

What are they?

Slightly off topic but, since swapping my wheels, sticking new pads on, cleaning the rotors etc, my Deore Hydraulics have gone from very good to really bloody amazing.

ugo.santalucia

Veronese68 wrote:

What actually causes the honking in the wet? I'd have thought it's a vibration of some sort, just a different frequency. But it does vary according to pad material.

Possibly thermal expansion of the water embedded in the pads as they heat up during braking... It's just a guess, don't crucify me

tgotb

ugo.santalucia wrote:

Veronese68 wrote:

What actually causes the honking in the wet? I'd have thought it's a vibration of some sort, just a different frequency. But it does vary according to pad material.

Possibly thermal expansion of the water embedded in the pads as they heat up during braking... It's just a guess, don't crucify me

Ooh, I'd never thought of that. Does sound plausible...

On_What

lol heard it all now

roger_merriman

TGOTB wrote:

ugo.santalucia wrote:

Veronese68 wrote:

What actually causes the honking in the wet? I'd have thought it's a vibration of some sort, just a different frequency. But it does vary according to pad material.

Possibly thermal expansion of the water embedded in the pads as they heat up during braking... It's just a guess, don't crucify me

Ooh, I'd never thought of that. Does sound plausible...

Not my experance with disks, on a wet MTB ride the gears sound grittier than the disks. My old commute MTB might on a wet day make one honk but that's it, though in fairness neither of my bikes honk often.

Yesterday plenty of the bridleways where more stream than path, plus down hill etc, so disks where getting wet, plus fair bit braking etc. Only times I get a lot of noise is when I have new pads briefly. The trance did that for 30s going down a very steep old tram line, could hear water from vegetation sizzling on the disks after that but no honking!

97th choice

I have found properly set up cable disks to be superior to rim brakes, however both bikes I purchased with discs had been poorly set up which was the single reason for initial poor performance. The trp spyres on my latest bike required a centering and pad adjustment before they worked properly.

fenix

Oh Bender - mate has 105 cable discs. He's seriously unimpressed with them. He can fettle a bike to perfection normally but these are defeating him.

And whats the deal with the advice of 'first you must bed them in by doing some hard braking' how is that allowed ?

If you buy a bike - the brakes should work straight off. You'd not accept a car that didn't have working brakes ?

roger_merriman

Fenix wrote:

Oh Bender - mate has 105 cable discs. He's seriously unimpressed with them. He can fettle a bike to perfection normally but these are defeating him.

And whats the deal with the advice of 'first you must bed them in by doing some hard braking' how is that allowed ?

If you buy a bike - the brakes should work straight off. You'd not accept a car that didn't have working brakes ?

"first you must bed them in by doing some hard braking' is the same advice you'll get with new pads for a car and has been well since cars have had disks.

Ouija

Think about it. You've got a smooth, hard, non-sticky, material (the pad) pushing against another smooth, hard, non-sticky material (the rotor). In theory this should generate the least amount of friction and, therefore, braking possible. And it does.... at first.

Disk brakes work not by any friction between the pad and the rotor but between the pad and a layer of deposited pad material on the rotor. In other words, it's the pad material molecularly bonding with pad material that's been left on the rotor. But first you have get some pad material onto the rotor. A few short, sharp braking maneuver's usually helps with that.

bendertherobot

Fenix wrote:

Oh Bender - mate has 105 cable discs. He's seriously unimpressed with them. He can fettle a bike to perfection normally but these are defeating him.

And whats the deal with the advice of 'first you must bed them in by doing some hard braking' how is that allowed ?

If you buy a bike - the brakes should work straight off. You'd not accept a car that didn't have working brakes ?

Is that these things?

http://www.evanscycles.com/products/shi ... r-ec057443

I've never used then, and never seen them on many bikes.

meanredspider

Fenix wrote:

Oh Bender - mate has 105 cable discs. He's seriously unimpressed with them. He can fettle a bike to perfection normally but these are defeating him.

And whats the deal with the advice of 'first you must bed them in by doing some hard braking' how is that allowed ?

If you buy a bike - the brakes should work straight off. You'd not accept a car that didn't have working brakes ?

I'd say your mate needs to become a better fettler - he's clearly not that good.

And, yes, bedding in brake pads is exactly what you do with cars. In fact, more often than not, brakes that are described as "warped" on cars isn't anything of the sort but pick-up on the disc from the pad because they weren't bedded in properly. Your mate probably isn't a good car fettler either.

fenix

LOL - oh his road bike is immaculate. He's excellent at that - but I guess discs are a new kettle of fish. He doesn't do his own car fettling - he has people for that...

Thanks.

tgotb

MRS won't hear a bad word said against disk brakes. Any issues must be the user's fault.

Meanwhile, in the real world, there seem to be a whole lot of people who have trouble setting them up correctly; it seems that rim brakes that have been set up by average cyclists often outperform disk brakes that have been set up by average cyclists.

Maybe the answer is that, if you posess MRS's legendary fettling skills, you should put disk brakes on everything. For those of you who don't posess his fettling skills - maybe, just maybe, you might be better off with rim brakes in some cases.

For what it's worth, I have four bikes with disk brakes, four and a half with rim brakes and one with no brakes at all. All the brakes work pretty effectively; the cantis on my pub bike are probably the worst, and the calipers on my road bike are undoubtedly the best. The disks on my cross bikes are less prone to clogging, and the disks on my commuter don't wear out the rims. The disk brakes were more finicky to set up properly than the rim brakes, but require less ongoing maintenance. Hydraulic disks are more finicky to set up than cable disks, but require less ongoing maintenance. Horses for courses.

meanredspider

You do need some basic fettling skills for disc brakes (especially mechanical ones - hydraulic are the proverbial piece of pi55 (else MTBers would go nowhere)) and not much of biking needs much mechanical ability at all. But you just need to follow some simple instructions.
It's probably a good job that not many people fettle their own cars!!

Monty Dog

IME if the brakes get wet, they howl a bit - a bit of downhill braking usually sorts it out. Also, decent quality brake outers make a big difference to how cable discs perform. I've been runnin BB7s on various bikes since 2002, not the lightest but they work.

meanredspider

Yes - I have Gore Ride-On cables - they're really nice. I've also found that Shimano 105 brifters were better than SRAM Apex. It's important to remember that brakes, like gears, are a system: crappy parts in it will affect the way it all works.

antsmithmk

meanredspider wrote:

Fenix wrote:

Oh Bender - mate has 105 cable discs. He's seriously unimpressed with them. He can fettle a bike to perfection normally but these are defeating him.

And whats the deal with the advice of 'first you must bed them in by doing some hard braking' how is that allowed ?

If you buy a bike - the brakes should work straight off. You'd not accept a car that didn't have working brakes ?

I'd say your mate needs to become a better fettler - he's clearly not that good.

And, yes, bedding in brake pads is exactly what you do with cars. In fact, more often than not, brakes that are described as "warped" on cars isn't anything of the sort but pick-up on the disc from the pad because they weren't bedded in properly. Your mate probably isn't a good car fettler either.

Agreed with this. When installing new pads or rotors the last step of the instructions is always to go and do 5-6 hard stops somewhere safe to get some material off the pad and on the rotor. No point in polishing the disc, you've got to really brake hard. A garage( for a car) would do this for you