dynaryder

I'll refrain from jumping into the disc-vs-rim fray,and just say I don't think ride quality will be seriously effected. My 'touring' bike(I've actually done everything but tour on it) is a Novara Safari;U6 alloy frame with steel fork. With 2" Marathon Supremes it rides real nice;this is the bike I default to for commuting when my carpel tunnel acts up. My old 1x1 rode nice as well,and that was with 95psi 1.3" slicks.

Steve B.

"Disc rotors don't have a larger surface area then a wheel. Even a 203mm rotor (far from the standard size) has a much smaller surface area and is a much smaller heat sink than even a small diameter rim."

Huh ?. Look at the point where the disc pad meets the rotor. Look at all that metal around it. Now look at where a rim brake pad meets the rim and tell me there's more metal in the vicinity of the pad to dissipate heat. Total nonsense.

Nonsense #2 - "Disc on mountain bikes are there for two reasons. Number one is because of suspension systems that make mounting rim brakes difficult. Mountain bikes always came equipped with discs...as do all bicycles with rim brakes."

Discs or rim brakes have nothing to do with suspension or lack of. They have been building full suspension mountain bikes for maybe 20 years using rim brakes. The only issue with FS bikes was brake induced suspension activation, but that's an issue regardless of the brake system. Mountain bikes did not always come with disc, that's recent to maybe 10 years or so. For the other 30 years, all sorts of rim brakes were used, Centerpull, Canti's, V's.

If memory serves, discs became common on downhill specific mt. bikes due to the ability of the system to handle higher speeds and to not fade after hard usage. In other words, as compared to rim brakes, the discs were better stoppers on long steep descents due to the ability to handle the heat. Rubber compounds on rim brakes do not handle heat as well and there was also the issue (as others have stated) of tire blow-outs, which were dangerous on a downhill race.

Mithrandir

I commuted in the rain for the first time yesterday. I was disappointed in the performance of my V-brakes, which up until that point, were absolutely flawless. But I can certainly see why someone would want disc brakes on a touring bike... When you go long distances, eventually you will run into rain and snow. Disc brakes will be good for that.

I told my LBS I wanted a road bike when I hit 300 pounds next year. They recommended a LHT. I might consider the disc option.

aroundoz

I was touring on dirt roads in the Snowy River area of Australia years ago and the descents were long and fast. My rims got so hot that two tubes were cut at the base. Could have been a rim issue but I had a lot of miles on the rims prior to this and never experienced this before. I swore I would make the switch to a disc brake touring bike.

Years later I now have one. I was touring last week in southern BC on dirt roads and doing some long fast descents and the discs were working great except when they heated up. Disc brakes lose a huge percentage of their braking power and become ineffective when they are too hot. Less so with larger rotors but are you really going to put 203 mm rotors on a touring bike?

My point is, disc or canti/v, you have to stop and give your brakes a breather when you doing long descents and a lot of braking.

qmsdc15

That puts the LHT on my "next bike short list". Without discs, not interested.

Six jours

I think disks are a good idea in general, but I'm not really thrilled with any available cable-activated brakes. Hydraulics work and feel much better, in my experience, but I want road levers on my bikes. Once someone comes out with a dedicated (ie. non kludge) hydraulic system with road levers, I doubt I'll ever go back to cantis.

sstorkel

Too bad Surly won't be offering disc brakes as an option on the S&S-equipped LHT Deluxe

MassiveD

Six Jour, the timing is looking like we will be seeing some new stuff for the 2012 cyclo cross season. So far nobody has been able to join the hydraulic and shifter into one package that looks like a finished project. This is an example where touring would probably be OK with a separate lever since some people use bar ends, and others use gear hubs. But nobody is going to make it for us. What racers want is really complicated.

cyccommute 

A bit of simple math. Area of a circle = 3.1415*r^2. A 700C wheel is 622mm in diameter. Assuming a brake track of 10mm, the inside of the wheel would be 612mm. Area of the outer disc - area of the inner disc = area of the brake track. For a 700C wheel, that area is 9691 sq. mm - for one side. Since there are two sides to the rim that are widely spaced, the surface area is a bit over 19,000 sq. mm. Applying the same formula to a hub mounted disc of 203mm diameter assuming the same brake track - which is very generous - gives an area of 3110 sq. mm or about 6000 sq mm for both sides. Thus the surface area of the rim is 3 times that of a disc. A larger surface area means greater heat dissipation and the larger mass of metal (surface area is related to metal mass) means that the rim is a larger heat sink.

But wait, what about the rest of the rim? First the disc is relatively one dimensional. It has little width. But a wheel has a wide width relative to the hub mounted disc. That gives it even more surface area. Assuming a 612mm diameter and a 22mm rim width, that give an additional 42,000 sq. mm of surface area. Now we are up to roughly 62000 mm of surface area, or about 10 times that of a large disc, which can be used to dissipate the heat.

But wait, there's more. The tire and the tube can absorb heat too. Using a 700C tire that is 32mm wide that's an additional 206000 sq. mm of area that is available for heat dissipation. Granted the tire doesn't dissipate heat as well as metal does but it does serve as a massive heat sink. So now we are up to 268,000 sq. mm of surface area. Which is massively more surface area than even a very large hub mounted disc rotor.

Completely missed the point. A rim brake is a disc brake. It just happens to have a larger rotor than modern hub mounted disc brakes have. Yes they use rubber pads but the rim is still a spinning rotor for the brake track and the brakes are called...well...calipers. All hub mounted discs have done is move the braking surface out of muck...only an issue if you happen to ride where there's muck about...and make the rotor smaller.

Hub mounted disc brakes didn't hit popularity until the mid2000s. I have a 2004 Specialized S-Works Epic that is equipped with both rim and hub mounted disc brake bosses. I have a 1998 Moots YBB that doesn't have disc tabs at all. Both bikes were on the high end of any mountain bike scale for their time.

Hub mounted discs do solve some of the cable routing issues that occur with full suspension designs and rim mounted brakes. Rims mounted brakes, especially on rear wheels, were very mushy and required extra cable and weird mounting positions for the brakes and weird cable routing. Front rim mounted brakes and suspension has never been a problem but the rear mounts were always a bit funky.

Extreme conditions. But those aren't likely to be encountered on a touring bike nor, for that matter, in most mountain bike situations. I've been riding loaded touring bikes in Colorado and other places in the US for 30+ years. I've been off-road riding mountain bikes in Colorado as well as other places for 25+ years. I've ridden tandems and mountain bikes pulling trailers with kids both on- and off-road. I've ridden some very hairy stuff in very hairy conditions from steep downhills during downpours off-road to 50+mph miles long descents on loaded touring bikes from 12,000 feet and not once have I felt that my rims were going to overheat or my tires were going to blow out. Nor have I ever thought that I was going to run out of brakes and needed something more powerful. It's about how you use them, not the mechanism that you use.

Gus Riley

I invite you to ride down HWY 56 from the Blue Ridge Parkway to Vesuvius on a fully loaded tourer, or even better a tandem...if your rims don't get hot, and you make it all the way down without stopping, then you sir will have to publish your braking techniques.

cyccommute 

The route doesn't much different than the Oklahoma side of Talmena Scenic Highway that I did as part of a tour in Arkansas last spring. Both start at similar altitudes and drop about the same over the same distance. But I've done longer, albeit less steep, loaded downhills like Loveland Pass to Georgetown, including the last 1.5 miles of white knuckle terror on the I-70 shoulder from Silver Plume to Georgetown, without stopping or overheating my brakes.

I've also done loaded tours off-road like Alpine Tunnel/Hancock Pass pulling a trailer, including this little section of loveliness that was filled with rocks and which was steep enough that my trailer kept lifting my rear wheel.

Another loaded mountain bike tour (with cantilever brakes) that I did was this one. It included this little cliff off the Rampart Range which I have done both loaded and unloaded. It's fun. It's fast. And I've never had a brake problem.

Although I haven't done it with a loaded bike, I have also done this downhill on a cantilever equipped mountain bike which, again, I did without overheating anything or experiencing any brake fade. The profile on the left (6.3 miles of it) shows what the road is like while the profile on the left gives you some indication of what it traverses.

I've never melted pads or experienced any kind of brake failure on any bike and I don't hold back when it comes to downhills. Even with a loaded touring bike, if it goes down I let gravity take over. But I never - never ever, ever - ride my brakes all the way down something. I always pulse my brakes, i.e. brake hard to scrub speed and then let the bike run. I also throw my weight off the back of the bike...even loaded...to get the most out of the rear brake as I can.

Your nightmare section of the Blue Ridge looks like a fun, fast short bit of heaven.

MassiveD

You can't melt brakes that you don't use, If your top speed is 50, it's different than if it's 25. I think we are on the verge of that thread on parachute drag brakes. But really if one wants a drag brake, get a drag brake. Niether current rim or disc brakes are drag brakes.

Gotte

There's also the whole "I cut off my fingertip with my disc brakes" thing. Not too common, if you're careful, but common enough to come up with 192000 results on on google.

njkayaker

The mass of the rotor is much less than the mass of the rim. The total mass serves as the heat sink.

motobecane69

i will be buying this new frame but i'm pissed that its going to take them til next february to get it to market. earlier this year I built a commuting bike with the nashbar touring frame (aluminum) and nashbar carbon cyclocross fork and I did it because I wanted wet weather stopping power without having to worry about it. That bike recently got stolen but i loved it so much i'm going to build up another. I will probably build on the same platform and when this frame comes out I will go ahead and swap everything over. Either that or I will find out if a simple fork swap can be done if I buy the current LHT and want the disc fork later.

To answer the original question, how can anyone have a problem with this. Surly is simply giving us an additional OPTION, you can choose it if you want and if you don't, then you don't. I don't see how anyone can look down on someone giving them an additional option such as this.

Six jours

I regularly ride on dirt paths in the mountains. The roads are often steep, but usually quite smooth, so a mountain bike is overkill. But if you don't ride the brakes on the way down, you go 70 MPH. So I usually find my valve stems going crooked at the end of a long day, and I won't be at all surprised if one gets torn right off someday. Disk brakes would be a welcome addition, at least for me.

Gus Riley

It's not a nightmare, really, it is quite pretty but you won't be flying down it, you see, you must slow way down for the switchbacks. Pulsing the brakes (as I mentioned in an earlier reply) isn't enough on this descent with a full load tourer, or tandem, especially if you let gravity do it's thing.

The invitation remains. I think you will find you have hot rims about a quarter of the way down.

sstorkel

Really? Did cyccommute post the wrong route? His version appears to drop 1600 ft over about 3.5 miles with a -5.6% grade. That's pretty much par for the course where I live, and not something I'd think twice about...

Gus Riley

I'm not sure I understand your reply. cyccommute mentioned some rides out west. My reference is on the Blue Ridge Parkway in the east. Mapmyride lists it as 9.9% over 2.5 miles, with a drop of 1330ft give or take. The same program cyccommute uses lists the Vesuvius descent at 11.1% avg. Nice program BTW.

I have no idea where you live, so I cannot agree if it is "par" or not. I do know that no one is going to come off of the Vesuvius drop and not heat their rims (disc equipped wheels excepted) ...I guess it can be done if one walks his bike down. This drop is steep, and has several tight switchbacks, there is no way you can just let it go, it is "not" a straight shot down a hill.

Go ride it, then come back and debate it.

In keeping to the spirit of the thread, Disc brakes would be an asset on the Vesuvius descent.

sstorkel

Re-read his post: his first link appears to be for the same ride you're talking about. It doesn't appear to be especially steep, or challenging so I'm wondering why you're making such a big fuss about it? I guess it could be an issue for a heavy tandem team, but I routinely ride my touring bike down similar routes and don't think twice about it. Never experienced any brake fade, so it didn't occur to me that the rims would be over-heating, as you suggest. To be fair: I always ditch the stock pads and replace them with KoolStop or another high-performance pad.

Gus Riley

I read it properly. cyccommute is attempting to compare the Vesuvius descents with some rides he has experienced. But from what I gather he has not ridden down it.

That section of Talamena Scenic Drive is impressive...but it is nothing similar to the Vesuvius drop. Talamena (just the ascent, no run out flats) is 3.7 miles long or so. It sports an average grade of 7.1%, with a max grade of about 14.7% close to the bottom where there is a good straight section to let it go. Everything above it is of a lesser grade with about a 9% section on top. https://ridewithgps.com/routes/671781

Now, map the Vesuvuis drop...just the drop...I usually don't heat my brakes on a flat straight either. The drop is 2.2 miles long, it's average grade is 11.1%, 20.6 is the max grade and that among several includes a switchback. Most of the rest of descent is in double digits. https://ridewithgps.com/routes/673251

The fuss comes into the picture when a debate turns to a question of integrity, and or capability. I am a experienced rider, I have been down this descent, I did experience hot rims where a cool down stop was required halfway down. I have also in an earlier post provided several testimonials concerning the Vesuvius descent, and can post many more. It is steep, it will heat rims (KoolStops or not), and it is the perfect descent to show the advantages of a good disc brake system. But it is the only descent that I have been on (so far) where I wished my LHT was disc equipped.

Go ride it with a loaded tour bike or tandem...that appears to be the only way you're going to accept my point. Better yet, I'll be going down it again with a fully loaded LHT (non-disc) around 7 May...I'd love to ride down it with you and cyccomute with heavy tour bikes, or even more awesome, both of you on a tandem (you decide who the captain is). It would be interesting to see your run to the bottom.

cyccommute 

Crooked valve stems are usually an indicator of low tire pressure which allows the tube to move around in the tire rather than high pressure you'd expect from over heated tires.

Secondly, it's damned difficult to go 70mph on a bike. I've tried.

Six jours

It's not pressure, it's heat slightly melting the bead and allowing the tire to creep.

cyccommute 

No, I haven't ridden down that route. But I've ridden down plenty of others routes that are comparable. Talimena may not be exactly like the Vesuvius drop but it's close enough. Similar distance with a similar overall drop in altitude 1240 ft over 2.6 miles vs 1290' over 2.4 miles. Not enough differences to quibble over.


I, too, am an experienced rider. The fuss comes from what I consider to be no need for a fuss. Personally, I'd ride down that route from top to bottom going as fast as I could and not worry about heated rims, brakes or tires. It's 2.4 miles at an average of around 40 mph, you'd cover the distance in about 4 minutes. If the route continued like that for 30+ miles, I'd think about stopping half way for a brake cool down but I certainly wouldn't stop after 2 minutes of riding.

Now if you were trying to keep your speed down to 15 mph over the same distance, that would take about 9 minutes and would build up lots of heat on the rims. I might start to worry by the time I hit the bottom but I wouldn't stop in the middle.

People who are reporting melted brakes on a 2.4 mile ride are probably trying to go even slower than 15 mph. It's not the fault of the brakes but a failing of technique. A hub mounted disc brake isn't any better when use improperly. They get hot too.

Gus Riley

I have tried to show that Talimena does not compare at all. I failed. Good luck riding Vesuvius at 40 mph. My opinion, concerning Vesuvius, you have no idea what you're talking about. In all fairness, please do not take me up on my invitation because you will kill yourself.

'Nuff on this subject here. Off subject long enough...see new thread.

https://www.bikeforums.net/showthread...6#post13144396