Wednesday, March 04, 2015

Disc Brakes For Gravel Bikes- The Good And The Bad

Bleeding brakes? What's that?
NOTE: Large doses of "my opinion" will be handed out in gloppy dollops today. You've been forewarned.....

Disc brake road bikes, disc brake cyclo cross bikes, and disc brake equipped gravel road bikes. You need them, right? Why? Well.......because disc brakes work better in poor conditions, have more power, and are "better". 

Are they really better though?

I'm going to say "NO", and I use disc brakes a lot, so it isn't like I am being all "retro-grouchy" here. No, I get why disc brakes are good for a lot of things. However; I am still not convinced of their necessity on road bikes and gravel/dirt/back road type rigs. They work okay, of course, and as stated, I have used them extensively. That said, I know I probably really "needed" to have disc brakes on any of those gravel road rides over the years once. Maybe. I'm allowing for the odd chance I may have forgotten a time there.

I'm thinking disc brakes on most gravel road rides are over kill, are heavier than alternative cable actuated cantilevers, and due to the loose surfaces on most gravel roads, disc brake "power" is never able to be utilized effectively. So........does any of this matter? Certainly not anything I am saying will mean a thing, since - like it or no- disc brake road bikes, gravel bikes, and cyclo cross bikes are what manufacturers need to create demand and make old bike designs "new" again.
Putting disc brakes on chain stays has prompted design innovations.

Then again, disc brake design has created some innovative ideas. Mounting disc brakes on the chain stays has freed up seat stay design to be a part that supports the rider with more forgiving attributes. Moving the brakes down nearer to the axle on the fork has removed the mud catching cable across the top of the front tires and opened up that area for mud clearances. Perhaps in some cases disc brake bike set ups are easier to operate, due to their increased power and efficiency compared to cantilevers.

However; I am pretty sure had disc brakes never come over from mountain bikes we wouldn't miss them. The thing is, road and cyclo cross designs have been homogenized and indistinguishable from year to year, brand to brand. Well.......that is until disc brakes came along. Then suddenly the old was new again. Especially in cyclo cross where it was perceived that disc brakes just had to be good like mountain bike disc brakes are. I'm not going to comment about that, since I do not cross race, but as for gravel roads? It is overkill, and not necessarily the advantage one might think. Road racing Pros seem to have ambivalent feelings about their use, although certain media darlings swear they will eventually overcome and be accepted as "better" than caliper brakes.

But in the end, I don't think disc brakes are "better" than cantilever brakes or caliper brakes. I do think they are different which is really why they will appear on road, cyclo cross, and gravel/all road bikes in the coming years. It's marketable, it is what consumers perceive to be "better", and it makes a visual difference in new product versus old. Sometimes I wonder when I listen to this chatter and marketing babble on disc brake road bikes. I mean, how the heck did they manage to stop with those old cantilever brakes and caliper brakes 50 or even ten years ago? It must have been magic or something. Weird.

27 comments:

Brian said...

I think the advantage of disc brakes, on any bike, really, is the separation of the 'stop' part from the 'go' part. The obvious separation is mud/water, which definitely causes a not-insignificant decrease in braking ability, but in my experience, the more important separation is that of a wobbly rim from a brake pad. Hit a pothole hard or break a spoke (or just get lazy for a while and don't true your wheels) with any kind of rim brake and you're in for a bummer time. With a disc brake, you can limp just about anything home.

Jason said...

I'm glad I got a BMC MC with cantilever brakes. Also, I bought my road bike in 2001 and don't think I have changed brake pads more than once (Campy equipped)

Guitar Ted said...

@Brian: I'll grant you your broken spoke point and will note that in all my years of gravel grinding, I've never broken a spoke. As far as poor braking- Bunk. I rode a canti equipped bike for years and the only time I ever had poor braking performance was when the rims got ice on them. Otherwise rain, mud, snow- Not a big deal.

Finally, and I was waiting for a comment like this- Disc brake pads and canti pads both are not impervious to accellerated wear in poor conditions. You can find stories all over the internet of disc brake pads getting eaten away down to the backing plates in a matter of miles if conditions are right. We saw this at Trans Iowa V6, as a matter of fact, and in that instance, having cantilever brakes was an advantage due to having more braking material than their disc brake counterparts.

The bottom line here is that the commonly heard "party line" on disc brakes being "better in poor conditions" is not a maxim to be held to. The reality is that both types have their advantages and disadvantages. It doesn't dictate that we shouldn't have cantilever equipped bicycles. But that's public perception, and that's "9/10ths" of the law" so to speak.

jeff said...

I largely agree that this is a 'want' vs 'need' situation interjected with large doses of 'sales and marketing'. That said, having ridden disc brakes on multi-surface applications (Fargo, Boone and many mtbs) I wouldn't want to go back to rim brakes. The power is great, but as you wrote..when the surface will allow you go take advantage of that extra power. But that same situation allows the disc to shine..delivery of power or modulation. Plus as Brian noted, no worries about a tweaked rim (or wearing one out). I guess I'm looking at it as there aren't really any deal breakers to having discs on a bike, but there are some advantages. Keep up the good work!

Mike said...

Ted- if you lived someplace with 3-5 mile long descents, do you think your opinion would be different?
For me, that's why I want my next bike to have disc brakes...more stopping power at 30-plus mph descents, plus less hand fatigue...but my opinion is, as you point out, based on mountain bike experience.
Thanks.

Z said...

My biggest reason for preferring disc over rim brakes is rim wear. On my daily commuter, I was routinely wearing the braking surface on the rims (Velocity Deep V) out and rebuilding wheels.

BluesDawg said...

Couldn't agree more. Disc brakes are fine, but so are rim brakes. I also think the crop of semi-gravelish road bikes with room for tires under 40mm would be just as good with mid reach caliper brakes. What used to be called standard reach.

Guitar Ted said...

@jeff @Mike: Remember, I am taking the viewpoint of gravel riding, for the most part. I generally split my time between a disc brake equipped bike, (Tamland) and my Black Mountain Cycles canti equipped rig. In back to back rides on the same courses, I see no advantages to disc brakes over cantis, and vice versa. (Keeping in mind that one must compare to a well set up canti, not your average canti set up that I typically see. many don't know how to properly set up cantis anymore. Advantage disc? maybe.)

But gravel is the equalizer. Power in braking must be applied carefully, and typically we do not brake hard into corners, so that facet is lost on gravel road riders.

So hand fatigue isn't really ever a problem. Scrubbing speed with disc or cantis, (again- well set up ones), is about equal here.

I feel much the same is true for road riders. The amount of road riding taking place in mountainous areas pales in comparison to road riding done everywhere else. Multiple mile descents may benefit from disc brake bikes, so let's have them. However; do "all" road bikes need them?

And the rim wear through point is again probably much more rare than you might think. Sure- some folks have that issue- but do "all" road bikes and gravel/all road bikes need disc brakes?

The answer is yes if you want to actually sell bikes tomorrow due to reasons separated from reality.

Ari said...

I completely wore out my Avid brake pads in about 55 miles during Trans Iowa V6. The wet gravel just ate away at all the material and left my brakes metal to metal. My friend Dan was running cantis. HE popped them open, cleaned them and kept riding. WE should also mention that Disc brakes need a stouter fork to handle the stress thus losing some of the "feel" of the fork. I vote for cantis on gravel bikes. Disc brakes are for me overkill.
Ari

Souleur Jo said...

GTed: I wholeheartedly agree, and really appreciate your thoughts there. Most are caught up with the fad of it all, and for now its 'in', faddish if you will to show up on your ride w/disc. Living in missouri, there are sharp hills, 20+% is routine, some short, some long. I started off with canti's and found I did want something stronger. I finally jumped over to the disc set up, and was rather disappointed. The weight difference was very real. I dropped from the front of the group to dragging an anvil after 50miles with discs. The only difference was the hoops. I weighed them and they were 9+lb for the pair.

I agree with you guys who ride them in that they are stronger, and rim wear and wet conditions, they would be worthy, yet that seems to be the exception overall in our riding, I find.

So in thinking about the trade offs, Ted: I have gone with a short-mini linear pull brake. They are stronger than canti, and lighter. I think over all they will be very adequate.

I will keep my disc in the drawer for now, as the hoops need to get down to the 1500-1600gm range for the utility to be a fair trade, without breaking the bank, and I do think they will get there, but will be a few years, then I am sure I will be back.

Til then, I agree ted, going grouchy is ok...

all/bjl said...

GT-you mentioned that a chainstay-mounted disc caliper allows for some clever manipulations of the seatstays which, in turn, can create a smoother-riding frame. Conversely, I'm given to understand (rightly or wrongly) that additional beef has to be added to a fork leg to accommodate the forces created by a front brake caliper, which compromises a fork's "smoothness." If that kind of asymmetry could allow the best of both worlds, though, is it a purely aesthetic reason that prevents a frame from being designed with rim brakes in the front and disc brakes in the rear?
Bryan

Michael Lemberger said...

I'm mostly in agreement that disks just aren't necessary for gravel, and I'm patiently waiting for a Tamland-style bike with rim brakes (though the Space Horse is pretty close.)

The memory of at least three riders coming in to the Heck of the North 2013 finish line with no disk brake pad left will remain with me always. Sure, part of that may be on those guys for not checking pad wear before the ride, but I didn't check my cantilever shoes either despite having ridden the same ones all season. Thing is, that though the Kool Stop Salmons may have looked like hell, there was plenty of shoe left.

The cost of replacing a worn rim is a salient point, though that savings might get eaten up with the repeated replacement of disk pads. A lot depends on conditions and braking habits, but it would be an interesting comparison.

Fear rothar said...

I think your observations, again, with respect, have a regional basis. Per @Mike's comment, throw in a succession of long descents and, even more to the point, some bad weather, and the goalposts move.

The key points, from my point of view, regarding brake choice, are related to tyre size and the conditions, both terrain and weather, that you ride in. To run wide tyres (for the purposes of gravel riding, let's say that "wide" means 40mm) with rim brakes, that limits you to cantilevers, centre-pulls or 70+mm reach dual pivot brakes. Relative to twenty years ago, cantilever boss spacing is much wider than it was (80mm being standard today versus as low as 50mm back in the day) while centerpulls, by virtue (or not) of their location, have always had widely spaced pivots. In both cases, what that means is, as the pads wear - and this can happen very rapidly given big descents and bad weather - they will tend to either dive under the rim (in the case of cantilevers) or rise into the tyre sidewall (in the case of centrepulls). Neither is desireable behaviour, to say the least, but it can be ameliorated by the use of a rim with a deep brake track, like Salsa's Delgado Cross model. I haven't used 70mm reach dual pivot, but some reviews suggest they are too flexible for demanding use.

To give an example, during one edition of the Green Mountain Double [in Vermont], we had day long rain. Using rim brakes, I wore out the sidewalls of an almost brand new Velocity A23 rim, and I'm not one renowned for over-use of brakes. A friend, using centre-pulls, blew out the sidewall of a tyre. On other occasions, I have dented rims on big descents (bizarrely, without getting a pinch flat!) badly enough that braking control was severely affected.

Disc brakes are certainly not without their own issues but, for much of the riding I like to do, their compromises are better suited to my needs. I can use the tyres sizes I want (indeed, I can swap wheels sizes too, as I trade between 700C and 650B wheels depending on what I'm doing). Braking response time and modulation is effectively independent of the weather and road conditions. The wear surfaces (the rotor) are easily replaceable and, given the correct pad choice (sintered metallic), brake pad life is good too.

Have I done and can I do the same rides with rim brakes? Yes, of course. However, I don't think that precludes me from concluding that disc brakes are a better choice.

R said...

another advantage for canti/linear is that even mechanical novices such as myself can manage to adjust or tinker with them if/when debris manages to get fudged up in there... if my disc brakes start giving me troubles - i'm SOL until i can get some help. i do love the stopping power discs give on single track... but i concur it's not a controversial statement to say gravel rigs don't require discs... (my $0.02) -R-

Guitar Ted said...

Again- I'm NOT against disc brakes, but I am saying that the rush to eliminate cantilever equipped bicycles is driven by something other than the "advantages" of disc brakes vs cantilevers.

Just reading through these various comments, you can easily pick up that for some one way is good, for others the opposite, and for some, (like myself), either way is as good as the other.

I will agree that there may be something to the ride quality argument against disc brakes, especially in the area of the fork.

Many bring up the rim side wall issues, but I think this is an exception, and so is the disc pad wear through. Point is, that argument probably is a wash, excepting that perhaps rim replacement is more costly.

Also, I haven't seen this mentioned, but disc brakes do cause a different sort of stress on wheels, typically manifesting itself in broken spokes. Again, rare, but worth bringing up.

Paul and Anna said...

Totally cosmetic, but I love that disc brakes allow me to have blacked out rims without needing to drop $2k on carbon.

Fear rothar said...

Speaking of stress on wheels, we have had three Velocity rims (Blunt and Blunt SL) split down the middle on our disc-brake equipped tandem. Mind you, my brother suffered a similar failure on a rim-braked Aerohead OC, so the jury is still out (except that my opinion of Velocity rims is very low).

Patrick said...

As a rider of all things two-wheeled (CX, Mtb, Road, Moto) and a current frame designer I feel the need to weigh in here. All points above are valid in regard to disc vs canti vs rim. Simple physics calculations shoe that a rim brake is the 'strongest' as that is the largest disc available. However, control can be a factor and heat mitigation is generally not good. Cantis are the 'weakest' option as currently designed , but can be increased with a one cable re-design to simulate newer style direct pulls. The bonus is lots of clearance and similar attributes to the rim brake. Discs are a very separate beast. Braking power of discs is actually less than rim brakes due to the distance to the surface contact patch. Also, spoke tensioning can create imbalance issues and further degrade handling. Most current road riders don't want to see a 3x front wheel and radial lacing to a disc hub is a tragic accident waiting to happen. Lastly heat (long thought of as a rim problem) is much more so a hub problem. Friction (heat) that cannot dissipate gets transmitted through the rotor into the flange, the oil (or cable), and ultimately into the hub. If this occurs, catastrophic damage is imminent. Don't get me wrong, I use discs on most of my designs but I prefer larger rotors (180 rear and 203 front) with hydraulic oil systems. F=ma cannot be avoided and the numbers don't lie. Whether gravel or road, a bicycle with rider total weighing 175 pounds moving at 30 mph creates a much larger force than the same person on an mtb at 15 mph. Increase the speed to 50 mph on a good road descent and the equation becomes very serious.

I ride all my bikes in all kinds of conditions and where they aren't supposed to go. Regardless of everything out there, ride your bike as you love to and for your own reasons. The best bike out there is the one you are riding.

Cheers.

Guitar Ted said...

@Patrick: Thank you for those comments. I was aware that Magura and some others had brought up the heat absorption issues with disc brakes and long descents for road, (and subsequently, gravel/back road bicycles), and this was a reason why they were not rushing to market with product for this category.

Of course, as stated, both types of designs have disadvantages/advantages, and I feel that your commentary is what is getting lost in the haze of marketing and consumer perceptions here.

Disc brakes can be wonderful in terms of modulation, power, and technical features, but I still have to wonder if they are perhaps a solution for specific issues and that they should not be seen as "simply better" than cantilevers. At least in the realm of road/gravel/all-road cycling.

youcancallmeAl said...

Very good points.And as a believer in Keep It Simple Stupid design and a fan of relatively flat, low speed rides, I find cantilevers to be more than adequate. Their simplicity and affordability is holds great appeal. I hope manufacturers will continue to offer both designs on quality bikes.

Gus said...

So, would you pick canti over disc if given the choice on an otherwise similar bike? (a Midwestern all-roads bike)

Let's say you are picking between a LHT and a Disc Trucker, or having a frame built.

Guitar Ted said...

@Gus: I've had an idea for a steel frame utilizing Paul Racer brakes for a long time. I should get that going.

That should give you an idea where I am coming from personally.....

Todd Tillinger said...

I made a conscious choice to go cantilevers on my Soma touring bike that gets used on mountain passes, loaded and unloaded, gravel and paved. I wanted tried and true, simple, reliable brakes, and the wheel is already a big ol' disc. They work great, and if they don't I clean them or swap the pads or adjust with a simple Allan key. In the 80's I went from perfectly reliable and simple cantilevers to rollercams, to U-brakes, and finally (90's) back to cantilevers. Drank the kool-aid, slept it off, and saw the light. I am just practical (and an engineer) not a retro-grouch. Disc brakes on cross, and touring, and gravel, will pass. Maybe.....

Todd Tillinger said...

Oh yeah, I had a brief and unsuccessful relationship with V-brakes, too!

Adam Van Dyke said...

I'm still on canti brakes myself, even in Western WA where we do get rain. One reason, it's what I already have and works well, on a custom steel cross bike I've had for about 10 years, and a older bean green cross check I've had a little longer. I have worn through rim sidewalls before, even once on a ride, but the wheels were pretty old, and I rode them in the rain and some cross races a lot, and probably didn't clean my rims and brake pads very often. On gravel rides even with some pretty big hills where I go I don't use my brakes a lot. I do have to be a little more cautious on some of the steeper downhills, but I can often make up for it on the uphills.
Also Canti brakes allow me to ride a nice steel bike with fairly nice parts, even if the wheels are not particularly light, and still be as light as some of the somewhat spendy carbon gravel/cross bikes with disc. The cross check with reasonably light wheels/fairly nice parts and a inexpensive carbon fork was only about 20.5# with pedals when I did a 85 mile gravel ride/event last summer, the nicer cross bike , which I'll be ridding more gravel on this year since I swapped back to a double, a little lighter then that, even with heavier wheels. And to get real close or under 20# on a cross/gravel bike size 56CM W 57CM TT with Disc will be a spendy bike. Guess I'll keep ridding what I have.

jeff said...

And I agree...no need to elimnate cantilever brakes on MOST types of bikes. And I also agree that the push for discs on roadbikes is largely driven by sales and marketing. I have a very strong dislike of internally routed cables, integrated headsets and bottom brackets (pressfit included). In my job as a mechanic, I've just seen too many issues that could have been avoided with a nod towards more traditional methods of construction. Brake choice, in the bigger picture, is pretty small potatoes.

Rhen Nicey said...

Brakes are one of those touchy things in a vehicle that just can't be messed around with. You need brakes for a very important reason: stopping. If they fail, your vehicle won't stop. It's that simple. This makes brakes very, very important.