"differential" brakes?

Raph

I recently bought a pair of Chorus brakes - not the skeleton sort, the old ones. 2006 I think. The rear one is single pivot. I rang the shop to say wait a sec guys there's a c0ck-up here, but they pointed out most brakes are like that now, it saves weight and the back brake should be weaker than the front. One of the best innovations of the last 20 years is dual pivots - why the b0lux have we "progressed" to a single pivot on the rear? Single pivots are a pain to keep centred, and they've got no bite - I used them for a couple of rides and gave up and got a pair of Centaur dual pivots - both dual pivots.

I've still got a few pairs of old record and gran sport brakes from the 80s - when single pivots were all there was they were great and I was used to them, however now I've got dual pivots on everything, that's what I'm used to. I've never had a problem with rear brakes binding or skidding a rear wheel, so I don't understand why the brakes should take it on themselves to regulate the fore-aft balance, I reckon it's up to me to learn how to brake. Having to pull unnaturally hard on the back brake to get any poke out of it is disconcerting, especially down hills.

I see almost all campag brakes are now "differential" - does anyone think it's a good idea?

aracer

Yes, it's a good idea, as you inherently can't brake as hard on the back as the front (due to weight transfer). I reckon Campag have it about right - the pull required to skid the back on its own is no more than the pull required to put you over the bars if you just use the front. Meanwhile they save a little weight, and I can't say I've ever had an issue with keeping single pivots centred. I'm not convinced you gave them a fair chance, given you started off with the assumption that they were inferior.

Raph

Thanks for the reply - "I'm not convinced you gave them a fair chance, given you started off with the assumption that they were inferior."

Totally fair enough. Before dual pivot brakes I was always happy with campag single pivot brakes - I just accepted the limitations... until I tried dual pivots. I still have an 80s bike with original nuovo gear - it's enough of a change to that from other bikes with dual pivots to make the beginning of a ride feel a bit dodgy, but when the front/rear balance changes as well it gets a tad dangerous, especially in emergency braking. So the issue for me personally is the one of swapping between bikes. I realize if all my bikes were like that I'd just shut up and get used to it, after which I don't doubt having two brakes the same might well seem weird - but I can't now change everything over.

Keeping single pivots centred is not necessarily a nightmare but as they get older it gets harder as the pivots wear - it's ok while everything's new and smooth but after a few strip-downs and re-greases the mating surfaces get less and less polished and they start to wander a bit and that 13mm cone spanner comes out more and more often. Dual pivots have done away with the whole business - you centre them when you fit them and never have to think about it again.

I've never had a problem caused by a back brake being as powerful as a front. I assume dual pivtos were invented in response to the fact that even the best brakes at the time were fairly feeble, but then did lots of people complain about back brakes skidding to prompt this latest change to "differential" brakes?

It's useful to know you reckon they're fine - I might give these another go. For the moment it feels as though I'm having to pull twice as hard on the back as the front. In situations where I need to brake at the back only - e.g. round a corner down a hill over gravel, speedway-style - it feels really dodgy. Not that I do that very often, but the point is when you get an unexpected situation like that, brakes have to be predictable. I think a less powerful brake might be ok but at the moment it feels like the back brake is spongy and just cr@p, though I admit it would, if it's not what I'm used to.

aracer

Raph wrote:

but then did lots of people complain about back brakes skidding to prompt this latest change to "differential" brakes?

I doubt it - it's almost certainly a marketing thing, along with a way to save a small amount of weight - I just don't believe it is a disadvantage either.

Raph

Oh well, I'll hang onto them as a spare set and give them a(nother) go some time. Thanks!

John.T

Shimano did a similar thing by taking some of the metal out of the rear brake to make it more spongy. I think they stopped it a bit later. I agree with Raph that it is important to have similar brakes on all bikes as you don't want to be testing your modulation in an emergency situation. The Ultegra SL brakes on my new bike seem to have more bite than the 9sp ultegras on the old one. I hope they will bed in as they are a bit un-nerving at the moment.

aracer

I think it would be a struggle to make my MTB discs, road calipers, TT calipers on carbon rims, crosser cantis and tandem cantis all modulate the same - let alone the fixie with no rear brake! Somehow I manage to cope.

heavymental

Raph wrote:

Oh well, I'll hang onto them as a spare set and give them a(nother) go some time. Thanks!

Chorus brakes as a spare set? I'd get them up on the classifieds. They'll sell like hot cakes.

Rob Sallnow

Heavymental wrote:

Raph wrote:

Oh well, I'll hang onto them as a spare set and give them a(nother) go some time. Thanks!

Chorus brakes as a spare set? I'd get them up on the classifieds. They'll sell like hot cakes.

Indeed they will....'old' Chorus brakes have all the style (hidden pivots) of the 'old' Record brakes but less than half the price....they simply lack a few Ti bolts and ball bearings.

As for the original point....differential brakes were introduced with two major selling points...reduced weight and 'improved safety'.....the former was the biggest reason with Campag being able to claim they had shed over 10% of the calipers weight without compromising performance and the latter was to hook the people that are not weight weenies.

Although the reintroduction of a single pivot also briought back the centreing issue it does mean that the rear brake can better track a slightly untrue rim far better than a dual pivot.

Raph

"a struggle to make my MTB discs, road calipers, TT calipers on carbon rims, crosser cantis and tandem cantis all modulate the same"

I've got a way to go before I've got that much of a problem! E.g I don't have tandem cantis or carbon rims on any of my road bikes, they're all good old rubber blocks on alu rims, and though some are shimano*** and some are campag, all respond in a roughly similar way. Between bikes of similar type it's an issue - I have one MTB but it's so different and handles so differently in every way that there's no chance of confusion on the spur of the moment, I'm used to how it brakes and the reflexes aren't going to try and pretend it's a road bike when that brain-dead driver pulls out in front of me or someone's ever-so-friendly pooch jumps out of a hedge and snarls. If I'm on any sort of road bike I'll have a generic road bike response. If the brakes are not as I'm expecting it takes that extra fraction of a second to realize I'm either lifting the back wheel, or gliding along smoothly as if I hadn't bothered to brake. Basically you get used to anything, and braking with no input from the brain isn 't a good idea anyway, but a bit of consistency goes a long way to helping avoid nasty surprises. There's enough variables to think about as it is with wet/dry/oily/icy roads. On the whole though I think aracer's point that I didn't really give them enough of a go is pretty valid.


"They'll sell like hot cakes." - yes, but undoubtedly for a lot less than I paid for them, and when I next need a pair I'll have to buy those skeleton things, and they're more expensive and "differnetial" anyway... so I might as well stash these away till needed. Every few years I have a blitz on the bikes and end up having to buy stuff to replace what I've sold or given away meanwhile. A little bit of hoarding isn't too bad...


"rear brake can better track a slightly untrue rim far better than a dual pivot" - yes, that's true, though I've only found that relevant on one occasion in 30-odd years (and it was a front!).


***I'd rather use shimano than walk.... but only just!

John.T

The pair of brakes on all my bikes, including MTB discs have the same modulation at the front and the rear. This means that balancing front to rear is much the same and is now almost automatic. Adding different braking efficiency to front and rear on some bikes would complicate this. This may suit some but it is not for me.

Rob Sallnow

John.T wrote:

The pair of brakes on all my bikes, including MTB discs have the same modulation at the front and the rear. This means that balancing front to rear is much the same and is now almost automatic. Adding different braking efficiency to front and rear on some bikes would complicate this. This may suit some but it is not for me.

I think your reading too much in to the effect on the brake balance with Diff brakes because if the calipers are the same front and rear the braking is still more effecient on the front anyway.

John.T

No. The braking efficiency to the wheel is the same. It is the friction between the tyre and the road that differs due to road surface and weight transfer. I need to feel this and differing brakes would get in the way of this especially if not all my bikes had the same differential. I see no advantage of Diff brakes as I can brake as hard as possible on the front and hold the rear just short of skidding with the brakes I have at the moment. This gives the maximum retardation possible limited only by tyre/road friction.
If you like Diff brakes by all means use them. They will do the job just as well but will feel different. This is my reason for not wanting to use them.

Raph

"the braking is still more effecient on the front anyway"

Until you skid the rear, the braking is the same on both. The only issue is that as you increase braking the rear tyre loses contact first, so you get most efficient braking from the front brake but only beyond the point where the rear would have skidded, therefore some of the power of the rear brake is wasted so it might as well be weaker. It makes sense, but after a lifetime of compensating naturally by braking sensibly and never having a problem with the rear brake skidding, it's strange to find that the left hand's got to re-learn its response, and if anything is now struggling to get enough useful braking, worse than it used to when single pivots were the norm and we just had stronger hands! If I only had one bike I'd just get used to it. ... er ..... wait a sec ...EUREKA that's the answer! - chuck out my other bikes!

Anyway, I think I've been persuaded that it's not a "bad idea", merely one that I won't bother to convert to for the moment.

Coyote

If there are any folks out there who have enough skill to be trusted with a dual pivot on the back without locking up the back wheel then IMHO you can't beat the Mavic SSC. An excellent, underrated set of calipers and good value at £110 at Parkers. No "block to rim" adjusters so work best with campag Ergo's.

Raph

Whoops - John T snuck in meanwhile with similar answer to mine.

I resisted the change from single to dual pivots until I could convert a few bikes at once, so I wouldn't have some with pokey brakes and some that needed far more pull on the levers and have to remember which was which in the fraction of a second of an emergency stop. I can see that in a few years when diff brakes are the norm and my current ones are shagged out, I'll probably do the same again - change a few bikes at once. Meanwhile I'm Mr luddite.

Another point is that the change to dual pivots was an obvious improvement - the change of just one of them back to single seems a retrograde move.

Thanks for the tip coyote - I'm sorted for now but if I never get into the "diff thing" it's good to know some people are still making normal brakes.

Rob Sallnow

Raph wrote:

"the braking is still more effecient on the front anyway"

Until you skid the rear, the braking is the same on both. The only issue is that as you increase braking the rear tyre loses contact first, so you get most efficient braking from the front brake but only beyond the point where the rear would have skidded, therefore some of the power of the rear brake is wasted so it might as well be weaker. .

That's exactly what I meant...admittedly it's only more efficient at a certain point but it's still more effective.

Anyway as I said the main 'advantage' according to Campag is the shedding of unrequired weight for people that buy them....that doesn't mean people with dual pivots front and rear should feel compelled to 'upgrade' to the latest thinking.

Raph

"That's exactly what I meant"

Yes, it jumped out at me as seeming inaccurate, but in effect I only ended up saying pretty much what you'd said!


"that doesn't mean people with dual pivots front and rear should feel compelled to 'upgrade' to the latest thinking."

Quite! But it's now difficult to find campag brakes that aren't differential. Some of the cheapies are still "equal" but I know cheap campag gear is sometimes not all that great. At the bottom end of the range, I actually prefer shimano! I got £15's worth of Tiagra rear brake to replace the single pivot rear chorus and actually it wasn't bad. Ok ok, so I should be strung up with a firecracker up my @rse for blaspheming, but it matched the front better than the original chorus brake did. Oh no, I'm really digging myself into a hole here aren't I! :oops:

aracer

John.T wrote:

The pair of brakes on all my bikes, including MTB discs have the same modulation at the front and the rear. This means that balancing front to rear is much the same and is now almost automatic. Adding different braking efficiency to front and rear on some bikes would complicate this. This may suit some but it is not for me.

Maybe the case for you, but certainly on the tandem and to a lesser extent on the other bikes rear cable stretch and friction means the back brake works slightly less well anyway. Meanwhile whilst the MTB discs should work the same front and rear being hydraulic, the smaller back disc means they don't. The thing is, in an emergency stop situation, or just normal going downhill braking on the MTB you do have to modulate the front and back differently to avoid locking the rear up / going over the bars, so I really don't see how it makes a difference if the front and back brakes work nominally the same or slightly differently - you've still got to adjust the braking pressure to each hand in a different way (and I'll note that apart from the MTB, all my bikes have much the same bars / brake levers). As I said before, somehow I cope.

Raph

"rear cable stretch and friction means the back brake works slightly less well anyway"

Two points - a) why exacerbate the effect which already weakens the rear brake? ...and b) I find the single-pivot makes more difference by itself than the cable issues of stretch and friction added up.

Ultimately this is all academic, since you either get used to it or you don't. If you like them, you like them, if you don't you don't. If all brakes go that way in the future, I'll get used to it and never look back. At the moment it feels like having to pull twice as hard to get any braking at the rear wheel.