Cycling UK Forum

I'm looking into the idea of having a tourer made to measure and I've been thinking about having braze-on mountings for disc brakes as well as V-brakes added to the frame and forks. It seems that there are more racks available to fit tourers with disc brakes now.

Any advice on this topic..........?

(There's probably a discussion somewhere on here about this...)

Woody: this doesn't help you in your search for discs but as far as I understand, rim brakes (cantilever or V) are still superior to discs in that they use the whole diameter of the wheel in braking (think levers). They also have the whole circumference of the rim to dissipate heat. This means that they should be better when it comes to stopping heavy touring loads. Disc brakes on the other hand are restricted to a small diameter "wheel". Tandems still use rim and drag brakes but not discs for this reason.

MTBs have disc brakes for quick stopping without a load and to avoid the problem of mud on the rim. 700c rims should presumably be even more effective than 26".

I am not an expert on this but am persuaded by these arguments (if they hold true). Disc brakes may look the business but may not be the best solution for a touring bike. I am sure others may disagree.

Woody
As a follow up on Horizon's coments why would you want disc brakes?as you would already have them with rim brakes.

Only problem with rim brakes is that they wear out rims!

I was also going to use my tourer for a little rough stuff now and then so there is a possibility that the rim could get caked in mud.

Isn't an advantage that they won't transfer braking heat to the tyre and avoid the risk of tyre damage/blow-out under extreme braking conditions (whether this is a real issue I don't know). Also the disc surface area can be greater than the rim surface area.

Another good reason for running discs is to reduce the amount of road-sludge that is thrown up onto wheels/panniers when braking in the wet. All that horrible grey grit generated by rim brakes is removed and (call me vain) that makes it easier to keep your bike-and-joy clean and shiny.

The main problem with discs is that they lack the mass to soak up lots of heat by comparison with a nice big rim. So they get VERY hot which ten glazes the pads and causes fade. In extreme cases it also warps the disc.

That's not to say that wear isn't an issue, but with even my MTB rims lasting three or four years then it's not a big consideration for me.

I notice that with the various Rohloff models being sold by SJSC, only the atb models seem to come with discs - the tourers all seem to have V brakes. I had assumed this was to do with pannier fitting, but these points about heat build up are very interesting.

On a solo without too much cargo weight, a good disc will hold out long after a rim brake has heated the tyre enough to blow it. Tandems and very heavily loaded tourers are different because of the extra momentum.

Disc fade is not a common occurance with normal riding, otherwise they'd not be so popular with MTBs who tend to go down hill at speed quite often.

However, you'll probably end up with MTB hubs if you go the disc route, thus meaning you'll have to have the back end spaced to 135.

I'd quite happily run a cable disc on a road bike, thus allowing good braking with drop bar levers (just check that your chosen disc does have the correct cable pull for drops). However, I think that it may be a little over kill for my needs!

Coming to this with no experience of cycle disc brakes, I immediately make what might be inappropriate comparisons with other forms of transport. Most obviously, disc brakes seem more than adequate for cars and motorcycles, and the bigger and more powerful they are, the more they are likely to have all-round disc systems. I do not suppose any motor vehicle has had rim operated brakes for a hundred years at least.

Then, the friction surfaces of brakes must eventually wear. It seems more logical that this should affect brake parts - discs and pads, rather than wheel parts as well as brake parts - shoes and rims.

Obviously weight comes into this, especially for racing, but discs do seem to be the way things are going for everything else.

thirdcrank: discs are intrinsically heavy - there's the disc for a start unlike rims which are there anyway. Motorbikes and cars can carry that weight without a problem. Then there's the fact that a rim is simply bigger than discs can ever be and will thus exert more leverage force than a disc. Component wear is a reflection of the design of the different surfaces - Shimano pads are too hard for most rims, so we use some other make so that the pads wear but not the rim - this would be the same for discs. I have also heard that discs operate too strongly on one side with attendant effects on the forks. MTBs reap the advantage of mud free braking but touring bikes would just carry extra weight. However, in practice there might not be much difference (except for tandems) but then why bother with them? Are they a fashion item? (and what's wrong with that if they are, I hear people asking).

horizon wrote:thirdcrank: discs are intrinsically heavy - there's the disc for a start unlike rims which are there anyway. Motorbikes and cars can carry that weight without a problem. Then there's the fact that a rim is simply bigger than discs can ever be and will thus exert more leverage force than a disc. Component wear is a reflection of the design of the different surfaces - Shimano pads are too hard for most rims, so we use some other make so that the pads wear but not the rim - this would be the same for discs. I have also heard that discs operate too strongly on one side with attendant effects on the forks. MTBs reap the advantage of mud free braking but touring bikes would just carry extra weight. However, in practice there might not be much difference (except for tandems) but then why bother with them? Are they a fashion item? (and what's wrong with that if they are, I hear people asking).

I agree whole heartedly except of course for fashion,fashion is a cruel master one only has to look at the bulging midriffs of ladies of more 'ahem' ample proportions wearing hipster trousers or tight leggings.Worse still get out old photos of the 70's (and everyone over 50 is guilty)to examine one's own fashion'statement'of yore.Not a pretty site.
Worse still Zandra Rhodes???????who always for some reason looks to me like a coal miner who's just struck a candy floss seam!
No,fashion is for the rich and foolish,cool dudes that they are
Disc brakes are for cars and motorcycles.

Just after my previous post the word Lycra sprang to mind and I almost removed my own 'fashion statement'but I think I can live with it......just

I am a very poor forecaster of which way bikes will develop. I bought a frame in 1980 and decided 5 speed spacing and 27" x 1 1/4" would do. More recently I persisted (twice) with threaded headsets. I'd like to think I will be still around in a few years to reflect on this latest 'flash in the pan'. In the meantime, where did I put those plus fours..........?

I have run Hope hydraulic disc brakes on my mtb for several years. I have to say that braking performance is in a different league to either v-brakes or calliper brakes - one finger braking whatever the conditions. However, the most noticeable advantage is in the wet and mud, so if you only ride in dry weather, they are probably not worth the money. I also note that weight is not a huge issue - if you add the combined weight of levers & cantilevers, they are only a little less than a complete disc setup, which is around 400g each end. There's also the opportunity to re-design the rim as there is no requirement to include a braking surface, and many MTB wheels do just that. Pads also seem to last far longer than the ones on my road bike.