Disc brake performance

[Falcon1]

What is it about disc brakes that gets people all enthusiastic?
I was sceptical that discs offered anything new because on my previous bike, with V brakes, I have locked the front wheel in both wet and dry. Whether coping with smidsys or braking hard just for the pleasure of it, they have been superb. How can any brake get better than that? Several months ago I bought a cross bike with discs, given the lack of number one choice.

The new brakes (mechanical Tekro single piston affairs) were utterly useless for the first few miles and it was not even possible to lock the back wheel when hauling on both. OK, maybe they needed bedding in. Eventually, after about 200 miles and much cleaning, tweaking and adjustment, the back wheel could be locked - so a basic requirement has been met but it's an undemanding one and a long way off what the front should be capable of. Finger load remains higher for given effect than rim brakes and there is no power or pleasure in them. Actually, I am more reminded of the bike with Weinman side pulls I bought 30 years ago- I ought to know, the rear one is still in regular use.

After about 1500 miles I have given in and spent £60 on a double piston TRP Spyre for the front (with new pads and rotor), in the hope of getting some improvement. Initial take up is better but finger load and ultimate performance are little changed.

People seem surprised when I say discs are rubbish but I cannot believe I have experienced two lemons. So what am I missing that could make them work as promised? (Take it that the basic things of pad clearance and cable adjustment are correct and pads and discs are clean.) Or is it actually a false promise?

[Brucey]

what model brake levers and calipers are you using?

cheers

[mattsccm]

Those old Tektro,s were crap. OK when new and perfectly set up but then dire. Did yours go " over can" and do nothing if pulled hard?
Avid Bb7s were much better. Haven't tried the double piston cable discs but hydros are a different game. In dry weather maybe not substantially better than perfectly set up calipers but in the wet a different league. My small hands mean one finger braking is better than a dirty great handful with rim brakes. Never found grip to be an issue, maybe as I also went to modern wider tyres at the same time and maybe because I am used to them, doing about 4000 miles a year on gravel and mud on my drop barred bike. Front wheel skids never happen and the back I only locks up in mud or on bouncy high speed gravel.
Needed? Nope. Nice? Yes

[hjd10]

What is it about disc brakes that gets people all enthusiastic?
I was sceptical that discs offered anything new because on my previous bike, with V brakes, I have locked the front wheel in both wet and dry. Whether coping with smidsys or braking hard just for the pleasure of it, they have been superb. How can any brake get better than that? Several months ago I bought a cross bike with discs, given the lack of number one choice.

The new brakes (mechanical Tekro single piston affairs) were utterly useless for the first few miles and it was not even possible to lock the back wheel when hauling on both. OK, maybe they needed bedding in. Eventually, after about 200 miles and much cleaning, tweaking and adjustment, the back wheel could be locked - so a basic requirement has been met but it's an undemanding one and a long way off what the front should be capable of. Finger load remains higher for given effect than rim brakes and there is no power or pleasure in them. Actually, I am more reminded of the bike with Weinman side pulls I bought 30 years ago- I ought to know, the rear one is still in regular use.

After about 1500 miles I have given in and spent £60 on a double piston TRP Spyre for the front (with new pads and rotor), in the hope of getting some improvement. Initial take up is better but finger load and ultimate performance are little changed.

People seem surprised when I say discs are rubbish but I cannot believe I have experienced two lemons. So what am I missing that could make them work as promised? (Take it that the basic things of pad clearance and cable adjustment are correct and pads and discs are clean.) Or is it actually a false promise?

I've never really liked mechanical discs and I've had a couple of bikes that came with them. In the MTB world riding without discs on any significant downhill sections and your arms will feel it especially as compared to a hydraulic setup. For me the modulation you get through a nicely setup disc brake is fantastic. My touring bike has front and back hydraulic brakes and whilst it is a little over the top, I wouldn't go back to rim brakes unless there was no other option.
I've recently tried this brake with good results as I needed an emergency cheap brake (the hoses are a bit long though).

http://www.chainreactioncycles.com/clarks-m2-hydraulic-disc-brakeset-bundle/rp-prod135593

It sounds like you need to persist a little longer and see what they bed in like.

Regards,

[[XAP]Bob]

No rim wear, far less affected by weather conditions (although not as good as a proper hub brake in that regard).

If you are struggling to lock the rear wheel then you're doing something wrong (assuming a solo DF bike of reasonably conventional geometry).

[The utility cyclist]

Discs are simply not needed, people need to learn to brake properly, learn to understand their surroundings/hazards, need to understand how much traction their tyres have. Until tyres are able to have vastly more grip than current tech disc brakes are a technology step that are for the lazy, those that elect not to learn, the simple minded and frankly dangerous.

Safety, don't make me laugh, those choosing discs will think they can brake later then when it comes down to it find out that the brakes are not the be all by any stretch. Modulation, as above, learn to brake properly.

They make bikes look ugly in any case.

[[XAP]Bob]

Ugly, as with beauty, is in the eye of the beer-holder (and on this forum that's me )

I have discs on my trike - because the SA hub brake stub axle dynamo didn't exist when I was kitting it out.
I've got the hub, rotor and calliper to upgrade the front end of the raptobike as well - and based on my experience of brakes I do believe it will be a significant upgrade over the V brake that is currently in use - upgrading the rear isn't needed in terms of performance, but will be useful in terms of having spares on the bike, and in terms of freeing up the V brake mounting holes for other things...

On the MTB (which to my shame I still haven't built back up) I will have a disc at the front and a coaster at the rear.
On the Dawes I have rim brakes, and they are fine for what use it for...

In terms of safety - I'd rather have a brake that doesn't get clogged with mud and snow and that doesn't destroy structural elements of the wheel whilst braking...
Of course that's all possible with a number of different technologies - discs are just one of those...

[meic]

I have locked the front wheel in both wet and dry.

But how long did they take to bite?

To me that is the big advantage of disks over rims, the wet weather braking. That is the one thing I miss since removing it.

Yes they do need time to bed in, first fitted they are less use than putting your feet down!
Add to that they overheat quicker than rims do. They weigh more and often mess up rack and mudguard fitting.

So I am not a great fan of disk brakes but in heavy rain they have you stopped before your friends' rim brakes have started to bite.

[blackbike]

Disc brakes are heavier, more expensive to buy and maintain, and make DIY maintenance more difficult.

I cycle as fast as most people, and faster than many, and have always found rim brakes to be very good indeed, especially since dual caliper brakes and V brakes were introduced.

As for the problem of rim wear, that only affects front wheels for me as I almost never use my rear brake. Front rims last for years and I have never had one break. In many years of cycling I've found that front wheel replacement is nearly always because of dents to the rim, the wheel going out of true or a crash rather than the rim being worn away.

If professional road riders don't want or need disc brakes to slow down as they zoom down mountains at high speed I'm sure I don't.

I think disc brakes on road going bikes are unnecessary and mainly a triumph of marketing over utility.

[Brucey]

re rim destruction with rim brakes; in very muddy conditions this is unavoidable. But outside of this it seems to me that folk who are careful with rim brakes get them to last and those that are not will wreck anything. In fact they might be more likely to wreck disc brakes.

A case in point; recently an LBS (who know I have a interest in how stuff gets wrecked) presented me with a collection of bits and pieces that had come off a typical midrange hybrid bike. The bike was equipped with centrelock discs ('use resin pads only') and had some hydraulic brakes (not shimano) fitted. The brakes were self-adjusting, and had self-adjusted until the pads were so worn that three out of four of the pads (which were not fitted with retaining pins of any kind in this caliper design) had dropped out altogether.... They had then carried on self-adjusting until the (steel) caliper pistons were bearing on the disc, and the bike was still being ridden. Needless to say the discs were trashed, the calipers were trashed... it wasn't a pretty sight.

The bike itself hadn't been completely neglected; the chain had some oil on it for example; however the rider hadn't appreciated that the brakes might wear in such a way that it wasn't obvious at a glance (like it is with rim brakes), and there was no hint (such as the lever coming back to the bar) that some adjustment or maintenance might be required. Even so the noise must have been incredible! The LBS in question fitted some cable discs instead. With these, hopefully the owner will realise that when the lever comes back to the bar, he might need new pads, instead of leaving it until he needs new brakes....

BTW the reason I enquired of the OP about the exact model of caliper and lever is that this can alter how well the brakes work. If the brake levers are 'the new type' (NSSLR, as found on newly launched models of shimano road STI, 2008 onwards) you will lose about 20% braking power vs older brake levers (for standard DP calipers ~1993 onwards). This alone is enough to make for horrible brakes if the calipers are designed with the older cable pull in mind. If the cables are a bit crap, you can lose about 30-50% of your braking effort there, too. Brake pads can vary in friction coefficient +/- 30% or so (more when they are wet), and any contamination can render them permanently useless, without this being obvious.

Between all these things you can see that an averagely bad setup could easily be less than half as good as it could be, and if everything works against you, your brakes could be less than 1/4 as good as they might be with a decent setup.

I am no great fan of disc brakes ( I think they have their place, workaday bicycles not being it), but I would certainly check the spec, lube the cables (and/or fit better ones) and fit new pads etc before condemning the entire breed!

cheers

[Falcon1]

Those old Tektro,s were crap. OK when new and perfectly set up but then dire. Did yours go " over can" and do nothing if pulled hard?

No. Unless something breaks there is nothing that can "go off". The result is about mechanical advantage in the mechanism and friction between pad and rotor. Design, quality & setup only affect feel. The feel improved by fitting the TRP. The result did not change.

There is a minor difference between the Tekro and TRP. Whereas Tekro put the screw between piston and body so the piston rotates against pad, TRP put the screw between lever and pistons so the pistons don't rotate against the pads. A material difference? I greased the backs of the Tekro pads but I doubt it is of any consequence.

If you are struggling to lock the rear wheel then you're doing something wrong (assuming a solo DF bike of reasonably conventional geometry).

It's not about struggling to lock the rear - it could not lock the rear when new. A brake should be able to develop something like 3 to 4 times the force that the rear tyre can put down on the road. Given the two brakes are identical, apart from rotor size (which can only contribute to a 15% difference in finger load), I only mentioned it to show how poor the front is.

The back brake is otherwise not important. The front brake is important and I am struggling to understand why two different brands only produce a fraction of the braking I expect. The shortfall is so significant it is impossible to be about cable/hydraulic differences.

[blackbike]

I think disc brakes appeal to those who like to have 'high tech' things and not ordinary, old things.

When mountain bikes became popular in the early to mid 90s a new breed of cyclist emerged. These were affluent men, mostly new to cycling, who road high quality, high priced mountain bikes on the road for commuting.

The fact that these bikes were slower and more expensive than more suitable commuting bikes didn't worry the riders. Fashion was the main issue.

These days I think disc brakes are a fashion item than anything else.

I think it is a good thing if manufacturers tempt people into cycling by introducing 'high tech' things, even if they are not needed.

[foxyrider]

The only thing that has made the discs on my CX bike even remotely useable is the 180 rotor I fitted up front.

There is no feel, I have to use different pad compounds front and rear to get anything like a lock up - I don't think i've ever managed it to be honest. (even the barely adequate Shimano long DP's can do that!)

The dirt/rim wear thing is a red herring too - okay the rear rim gets dirty. But so does the rotor. Up front the actual rim doesn't actually get much dirt so a reasonable cleaning regime keeps the front rim brake in action - the only difference is where the dirt is - IME there is at least as much off the disc as the rim.

There is a place for discs - mountain bikes

(most CX racers still use rim brakes including our own Weltmeister Mr Pidcock!)

[TYKE]

TISH TOSH PISH POSH !!

Discs are the way ahead. As technology improves they have become lighter, more efficient and are a doddle to service and set up. Anyone with an ounce of spannering experience can sort them out ....

And as for not knowing when your pads wear out ??? Lazy poor maintenance !! Do you wait until your cars brakes fail or the light comes on to put a new set of pads in ???

The whinging pros who claim they have been burned or had their shoes cut through by a rotor are talking cobblers ....and If disc brakes are so terrible then why are ALL the main manufactures making bikes with discs ???hmmmm??

Or should we go back to cable operated cantilevers with rubber brake blocks and do away with all " this new fangled technology"??


But if the Luddites prefer old tech rim
brakes then so be it - but get off the case of those who prefer improved stopping power

[meic]

Or should we go back to cable operated cantilevers with rubber brake blocks and do away with all " this new fangled technology"??

When they are doing the job of stopping the wheel turning, why not?