WhyFi

What we should be able to agree on is this:

- bladed spokes are thinner than a disc
- spokes travel at higher speeds than a disc (further from the hub)

therefor:

- spokes carry far more potential for harm than discs

Who's going to save us from the spokes?


Grade school rationalization, grade school retort.

Doge

The weight difference can be greater than folks think. While a robust rim brake bike and the same model in discs may only be a few hundred grams difference, what could be done with a rim braked bike vs a disc one amounts to significantly more.

Some of the weight side of the disc comes in what must be done to support the forces.

-force on dropout is ~2X that of a rim brake.
The forks need to have more material as all the braking force is applied at the dropouts, vs rim brakes. So the forks will be stronger, stiffer and heavier. The latter two are not always appreciated.

-force on spokes is ~2X that of a rim brake.
Many ride heavier more robust wheels. Low spoke count radial laced wheels are popular light performance options too and these are not suitable for using with discs.

-Hubs need to support disc. Obviously much of this goes to the whole weight of the disc category, but 45g front hubs are not available for discs.

-cables need to travel down fork
There are after market very light cables and housings for rim brakes (power cordz - 50% the mass). Likewise I could see disc cables getting lighter too, but so far they seem pretty much what the mfg supplies. And they have farther to travel.

-rim braking surface can be lighter/no brake track needed (this favors the disc - I'm just being fair)
There can be a wee bit of savings in weigh by reducing thickness of brake track. But this is an area that is often reinforced to deal with bumps anyway. When you look at mfg specs, there is not much difference.

RJM

Good to know how you prefer to argue here. I'm done with you.

WhyFi

Lol - didn't you start off by saying that what I'd posted was the dumbest thing you'd read all week? And nice way to conveniently choose to be offended so as to ignore the rationale that doesn't comport with your fear-mongering.

TTFN.

Maelochs

Wow ... this thread turned into a normal TF debate pretty quickly.

The whole "disc danger" thing is about on par with "stranger danger." Great for hysterical folks who want to rationalize their irrational phobias.

If I crash alone it hurts. I will hit the pavement with the force of a fat many falling several feet while also traveling forward at several miles per hour. it will hurt. (Or at least, it always has so far.)

if I somehow land on the bike it will likely hurt more, because the area of impact will be smaller and the force thus concentrated. And all that is true even if I ride a no-brakes fixie.

If I am in a group and crash it will hurt more (or, it has so far.) The chances of landing on another bike are increased, and often the speed is greater. even if we All ride no-brake fixies.

if I hit a chain ring (even one which isn't spinning) it will tear me up. if I hit any part of the bike which protrudes, it may puncture me.

You think I am worrying about whether the other riders have disc brakes? You might---if you are either dishonest, or have never crashed.

here's one. I got run over by a truck. The force a semi can generate is fairly large---large enough to crumple the bike and snap every solid metal piece. I got stabbed in the leg by the spindle--a solid steel rod which the truck easily snapped.

Obviously spindles are too dangerous to have on bikes. 100 % of my collisions with semi-trailers have resulted in injuries by broken spindles.

Seems silly? No sillier than saying "I reject that test and base my argument on the result of a test which hasn't been done."

But the silliest part is that if you go down on a bike, Everything is dangerous. There is no evidence that crashes with discs lead to an increase in injury ... not even a test which is widely accepted that a spinning disc can cut flesh.

So ... any argument base don all that .... seriously, you need a bike stand and a cell phone and a chicken breast. Crank the pedals, jam on the brakes, over and over, until the disc gets hot. crank the pedals, jam the chicken breast onto the disc. Do it ... or stop talking about what would happen if it were done.

I would laugh like a madman if the person doing the test got his finger cut by the spokes while inserting the chicken breast.

Anyway .... There are a lot of reasons to use discs, and a lot of reasons not to. I suppose irrational fear is as a good a reason as any.

mstateglfr 

But you didnt originally say 'most'. Your initial post, the one that I questioned, said this-
"For a pure road bike, it's really not a big deal but for a gravel/adventure bike, it's a necessity for the ability to run wider than a 28mm tire."
There is no 'most' or 'typically' or 'much of the time' or anything like that. You claim disc brakes are a necessity for gravel bikes due to the ability to run tires wider than 28s.

Pretty justified in my initial post asking why its necessary...since it isnt.

Lets sum it up, shall we?
- Disc brakes are often found on gravel bikes now because they are trendy and they are advertised/sold as stopping better. It isnt at all because a wider tire can be run with disc brakes since the same tires can be run with rim brakes.

Good deal- thats an accurate statement which hopefully both of us agree on since is actually accurate.

JohnJ80

And recall that I then clarified that statement, to which you then took exception again (and claimed I said something for which I did not say). The sentence to which you refer did need clarification (adding "for me") and is why I clarified it. That's why these are "forums" and why we have "dialog." It's customary to take the latest clarification as the current position.

One has much wider choice of wheel selection with disc brakes to which those same tires can be applied since rim width doesn't really factor into it anymore. But, yes, your statement is accurate.

I personally have a cross bike with cantilever brakes on the back and V-brakes on the front that I ride on gravel. That all said, the brakes are a pain and I'd rather they were disc brakes. That all said, for the reasons I listed earlier, I'm not switching just yet. A few more years will be interesting to see if they get the weight under control, find better ways to route hydro tubing, etc....

dabac

Kinda-sorta.
My - Admittedly limited - research showed that long reach caliper brakes tended to extend the arms instead of lowering the pivot points. If that trend holds true, then you can indeed fit longer reach caliper brakes to deal with quite wide tires - fork and frame allowing.
But brake force will be reduced.
Canti and V-brakes don't have this issue as pronounced.

MC13

My greatest fears while riding are, in order:
1. Cars
2. Other riders
3. The pavement
4. Bike parts: chains/teeth, then spokes, then protruding bits
5. Animals


In the few times I've fallen (or have observed falls), #1 or 2 are almost always the cause, #3 results in the most damage, and fortunately I've mostly avoided #4. Interestingly, with #5 I saw a chipmunk get decapitated earlier this spring by Ksyrium SLs...very messy.


I guess my point is that if I can at all avoid problems with #1 or 2, I'm going to do whatever I can to decrease the harm of #3 & 4, and in most cases better braking could probably have helped avoid the falls or at least the severity of the damage.


If discs are more reliable all-around, I can't see any reason, apart from cost, why the majority of all riders wouldn't make them a strong consideration when buying a new bike as it really hasn't been proven they pose any credible risk greater than other factors. I assume the industry has done significant research on this since discs have been around so long and manufactures wouldn't knowingly introduce anything that increases the risk of severe injury (apart from faster, lighter bikes). Maybe I'm naïve. Practically speaking though, I would think the combo of spinning spokes and forks/stays present a far greater danger to any body parts in the vicinity of the rotors. Just ask the poor chipmunk!


Just my opinion and I respect all others.

Paradaz

I'm more than happy with the performance of both hydro/disc and caliper/rim brakes........what gives the edge to the hydro brakes for me is spending £100s on a nice wheelset and knowing they aren't slowly getting worn out over time.

merlinextraligh

When was the last time you wore out the brake track on a rim on a road bike?

Personally in 45 years of riding and racing bikes I have never replaced a rim because the brake track wore out.

In my experience the rim has always gotten hopelessy bent, out of round, spoke holes cracked, or the wheel just obsolete before the brake track wore out.

Paradaz

I've worn out plenty of rims, I'd say they typically last a few years but I guess it obviously depends what sort of terrain you're riding on and how much you have to use your brakes.

I live in the Lake District in the UK, a 40-50 mile ride will typically include 3000-4000 feet of elevation with some downhill speeds over 50mph...longer rides up to 100miles may have anything up to 10,000feet of elevation and my point is that if you're doing that amount of climbing then you're also doing the same amount of descending and it's rare that you can open it up and pedal downhill like a maniac. Even reaching 40-50mph you're then regularly slowing down to 10mph to take tight corners. The brakes/rims get a good beating.

Fred Whitton Challenge route: This takes in some of the best climbs in that area: https://www.strava.com/routes/19518?hl=en-GB

If you're from Jacksonville, then I can appreciate that the elevation is on a different scale. I've seen some Strava entries from guys in Florida that have done 40+ mile rides and got something like 30feet of elevation in total...absolutely insane.

Dean V

Off topic, but no way are you climbing 10,000m in a 100 mile ride. Even if it was all up and down with no flat land that would mean 10,000m climbed over 80km. Average gradient over 10%.
Post a strava ride link to prove us doubters wrong.

gregf83 

You live in a warm flat place so it's not surprising you don't wear out rims. I get about 2 seasons in the winter out of a rim. On my summer bike I agree I would likely never wear it out using rim brakes.

Marcus_Ti

Don't make me break out dimensional analysis on you.

Paradaz

There are just over 3 feet in a metre (I did erronously write metres rather than feet in my post!)

Maelochs

Ummm .... wow. I Really don't get the metric system.

I would have thought 100 miles would be 160 km. Sorry ... I am American. The metric system is just too hard.

Maybe meters get shorter when braking with discs?

Jpayer1

GCN just did some science.

Dean V

If the ride is a circuit rather than a one way trip up a mountain you go down as much as you go up, hence you are going up only half the time/distance.

Maelochs

as I recall they used CF rims on both bikes ... but had they used Al rims they might have found dry stopping to be even closer.

As recall, the result was: In the dry, pretty even and in the wet, discs.

But that just considers braking distances. It ignores weight, and wheel changes. It ignored heat, which gives discs a huge advantage in mountainous terrain.

Pretty much ... the science confirms what the honest people already knew.

Buy whichever brake system best suits your riding situation. For basic dry-weather road riding on flats, the differences are so minuscule as to be nonexistent.

Marcus_Ti

IMHO, were it not for the hordes of legacy equipment in use...and the fact that the industry basically spent the last 10-20 years blowing their credibility regarding what constitutes an actual "improvement" with ridiculous made-up percentages...roadies probably would have just accepted discs like MTB and CX. It is almost like trying to get the world to get over the Windows XP days.


My Bigfoot with hydro discs stops better in any condition than my Seven with Campag Skeleton calipers and Koolstop pads/holders. Braking is better modulated, it has more power. It is just better. Not going to replace my Seven, because it is a nice frameset...but the braking performance with alloy rims just isn't a contest.

Maelochs

You have managed to totally ignore everything you don't agree with to support your position with irrelevant information. I am in awe of your skill.

Marcus_Ti

My personal experience with my equipment in my personal conditions is irrelevant information? I note how you cropped your quote to do some ignoring yourself.

DrIsotope

To legitimize the GCN tests (which they admit from the outset are Mythbusters-level "science") you'd have to use a robot on a bike on a homogenous surface of known grade, upon which repeated braking cycles under different conditions are executed. Dry ground with dry braking surface, wet ground, wet ground with wet braking surface, etc. The most salient point of these tests would be stopping distance relative to lever force. If both braking systems stop in the exact same distance under all circumstances, but one takes half the lever force, that system is superior. Objectively.

Maelochs

The phrase "Choose the tool which will best help you do the job" comes to mind. But apparently a lot of people freak out when they realize that each and every one of us are trying to do different jobs.