hukapits

Hi there,

I see that most of touring bikes uses rim brakes and I can't imagine how you guys handled your bike when you have to roll down on your loaded bike the long descending road. Would some of you that ever experienced this conditions share your knowledge on how to brake your bike during long descending.? I'm talking about (maybe) tens of kilometers you have to roll down on your loaded bike from top of the hill you just passed. This kind of descending will wear out our brakes and rims almost instantly and lead ourselves to accident or bike troubles at minimum if we don't know how to do it but eventually we must descend that road anyway. Pls share your experience and knowledge here they will be very useful to newbees I bet.

stephenjubb

easy, freewheel, use brakes where appropriate i.e. approaching corners.

if have applied brakes continously for several minutes use intermitent braking or failing that stop to let them cool down.

missjean

Feathering the brakes & alternating between front and back, which helps with hand fatigue too.

Derailed

Oddly, I've heard people talk about this for years (that is, how to brake a touring bike on a long descent), but in my experience it has never been an issue: I hardly brake at all, and I've never felt out of control.

I find that wind resistance generally keeps me at a speed for which I feel comfortable, and the only braking I do is coming into sharp corners or if, of course, I really want to come to a complete stop. For the most part, however, I just let the bike go as fast as it wants, perhaps standing up occasionally to increase drag.

Of course the grade, curviness and road conditions matter a great deal in this, and I don't doubt that there are hills I've never experienced that would cause me to change my tune.

But, at the same time, I consider myself to be reasonably experienced: I rode the Northern Tier in 2010 from WA to ME, for example, and worries about braking never crossed my mind. And, I'm certainly no dare devil.

Anyway, just in case this post comes across otherwise: I do not mean to trivialize your concerns, and I'm certainly not trying to promote myself as having nerves of steal or exceptional bike-handling skills. Rather, I'm sincerely perplexed that braking is such an issue for some... am I alone on this?

Jim Kukula

Often I will stop at the top of a big hill to add a layer or two of clothing. A loose fitting shirt or jacket can flop around a lot and help slow down a descent!

One big factor in descents is visibility. If you can see what's ahead, then you can allow yourself to go quite fast, because you'll be able to give yourself the time to slow down when approaching an obstacle. A curvy road in the woods is a whole other thing!

If I am coming down a big hill where I can easily get going too fast, I watch my speedometer and just get braking to keep myself in the 20 mph zone, or anyway below 25 mph. On a really long hill, the temperature of the brakes will come up enough so the heat dissipation rate matches the energy absorbed by slowing the descent. Of course, upright posture and baggy clothes help! But a big load on the big means more energy to dissipate. The slower you descend, the lower the rate of energy dissipation, and the cooler you'll keep your brakes.

A friend of mine some years back was training to race and putting in a lot of fast mileage. He was coming down a hill when an oil delivery truck backed out from a house. My friend lived through the experience, but barely. I saw him walking slowly on the street after six weeks in the hospital. He had no desire to get on a bike ever again. Riding out of control is not a good idea. You don't want to ride faster than your ability to avoid obstacles.

There is a nice discussion of braking in the third edition of Wilson's Bicycling Science .

Dan The Man

On downhills I try not to be faster than 5 mph above the yellow speed recommendation at the curves.

wiiiim

its pretty much a non issue imo, doing the death road (and below) in Bolivia all the way up from la cumbre above La Paz (about a full day of decent coming from 4700m) was just fine with V brakes
we did make regular stops there, but mostly because of the view, and perhaps to give the wrists some rest :-)

cyccommute 

I, too, think people get way to wigged out on downhills for no reason. It's not just touring bike either. Roadies will get all wigged about it too. Even some mountain bikers, and downhills are the fun part of mountain biking.

Wind resistance can play quite a role in slowing you down. At 50 mph (a stupid speed on a bicycle) simply sitting up can drop 3 to 10 mph off of your speed. The speed change is less at lower speeds but it can still have an effect.

If you are going to sit up to take advantage of wind resistance, don't do it while you are braking. I believe that many people's problem with brakes have to do with not knowing how to use them effectively. If you are sitting up and forward, your deceleration is severely limited. Sitting normally on a bike you can develop about 0.5g of deceleration before you go over the handlebars. If you shift you weight back and down (back about 4" and down about 2" which isn't a lot of movement), you can double that deceleration. That means you stop in less distance with the equivalent brake force. It's easier on the brakes and much more effective at slowing the vehicle. So sit up before the corner, then drop down as you brake.

djb

edit

but yes, I agree with all of the points given by all of you. Its not a real issue.

professorbob

I did a 12 mile descent up in Vermont (credit card tour) with stretches of about 10%. I had to do the front to back feathering as the road was rough, curvy and some construction trucks would appear from time to time. It worked fine for me in that I was always in control and the brakes/rims never got very hot. But that night, my wrists were pretty tired, feeling almost like I had carpal tunnel. In retrospect, I'd do it again the same way. It worked.

Big Lew

I am with "Derailed" and "cyccommute" on this issue. Other than visibility or high traffic concerns, I've found that a fully loaded bike properly balanced and equipped (appropriate tires and proper brake pads)has enough wind resistance that excessive, hard, long term braking isn't an issue. The only times I've had braking problems while touring with 230-240 lb. set-ups has been when I was using under-sized brake pads, or once while racing down a extremely steep and long detour road not meant for normal vehicle travel. Both times I developed brake fade, and also melted or burned 50% or more off the pads, but was never concerned that I couldn't stop.

Booger1

I don't have any braking issues,rim brakes work fine.I know people that trash brakes on their cars in one trip to the mountains,same holds true for bicycles.

mtnbud

As others have said, it's not a problem on most roads. You can sit up straighter causing more wind resistance which will slow you down some. (There have been times I haven't been able to get over 38mph due to wind resistance.) I did hit 56 mph once when I was on a smooth road with a long grade and a tail wind. With rough roads or roads with lots of sharp corners you do have to use the breaks more often.

I was on a decline last summer that was not safe without using the brakes. I was able to keep my speed slow enough without heating the rims by breaking hard and then laying off - also modulating between the front and the back. My buddy is not as much of a daredevil and was using his brakes more. I stopped once to check on him and his rims were too hot to touch with a bare hand. He continued to stop every once in awhile to let his brakes cool. I waited for him at the bottom of the hill.

I'm not sure what would happen if your rims got too hot. Maybe a blowout? An out of true rim? Has anyone reading this had a bad experience from allowing their rims to get too hot?

Cyclebum

Braking on long decents is mostly common sense. With rim or disc, best to switch back and forth, front to back, few seconds each. This helps prevent too much heat buildup. If disc, no need to stop to check temp. If rim, stop occasionally to make sure rims aren't getting too hot.

Used this technique on 7 mile steep decent into Death Valley from the west. Worked just fine with rim brakes. Stopped three times as a precaution, and to prolong the free ride. One of best down hills I've experienced.

imi

Was that coming down from Towne Pass? I rode OUT of Death Valley that way... but all that goes down, must come up... uh, or something like that
My descent a few days before from the other side was beautiful, but cold... I had to brake a lot so as not to freeze from the cold air, but wasn't worried about brakes overheating.

pdlamb

Starting with the right brake pads helps, too. Kool-stop Salmon pads don't accumulate the grit that softer (Shimano) pads will, and thus you don't grind the rims down.

It helps, too, that a longer downhill means a lower grade, and usually better engineering. Some of the worst downhills are the "fall off the ridge" type of roads. I'm thinking of the descent from the Blue Ridge Parkway into Vesuvius -- only 3 miles, but a 10% average grade, and I don't know how many curves. Compared to that, 15 miles down from Washington / Rainy Passes was easy; average grade I'd guess at 5-6%, long sight lines, plenty of space to alternate brief, hard braking with coasting. Just don't drag your brakes!

Worst case, if you do drag the brakes all the way down, is the wheel will overheat and blow the tire off. Met a guy who'd done that with his mountain bike, and taco'd the wheel as a result.

paul2432

Agree with others that this is not a big concern. I've done 10+ mile descents on twisty mountain roads fully loaded and not had issues. Of course the typical touring bike is not very aerodynamic (fenders, beefy wheels, bags, etc) and that helps keep the speed in check. I alternate front and back brakes and never let the speed get out of control.

Paul

Jim Kukula

My local hill

https://www.mapmyride.com/routes/view/51584600

isn't quite that tough. It drops 1000 feet in 2 miles, which is a 9.5% grade. Quite often when walking in town, at the bottom of the hill, I will smell the overheated brakes on some car that just came down.

I've got wonderful brakes on my bike, XTR with ceramic impregnated rims. I have never had any complaint from them yet on any hill. But I have certainly had a tougher time with the cantilever brakes on my 1996 Trek 520.

fietsbob

OP in a Hot tropical country may feel differently than I in a colder temperate one.

I seem to control my speed on downhills, memory of broken bones does that.

Oregon made Kool Stop Salmon compound are 'Rim Friendly' (their term).
so they don't seem to speed rim wear noticeably.
Brakes used, various : Campag single pivot, a CLB single pivot, on the Brompton,
Mafac cantilevers, Magura HS33, on the IG hub tourer,
Scott-Peterson SE cantilevers on the Derailleur tourer,
a KS pad of some sort on each..

Big Lew

When in the workforce before retiring, I was involved in commercial truck driver training, safety, and accident investigation. We had an on-going argument amongst drivers about steadily applying light brake pressure, or applying increased pressure for short intervals and allowing the brakes to cool a bit between applications. We did our own testing, and produced the same results as literature in our books....there is no appreciative difference while traveling at the same speed. I'm not sure if the same would apply to our bikes though, because we didn't apply brakes to different axles at a time on the tested trucks. Food for thought though, as it all relies on physics.

Jim Kukula

Thanks for this report - I have always wondered. These days I alternate front and rear brake, as much to reduce stress on my hands. But I tend to pump the brakes on my car, too. Somewhere along the line I heard that was good to do, but it's a bit hard to figure from a physics perspective. Could well be just an old wive's tale!

My best theory has been that releasing the brakes gets some more air onto the brake pad surfaces and lets them cool better.

But experiment certainly trumps theory!

fietsbob

There are run out gravel pits in the Sierras down from NV, in case what ever braking management
techniques used are not working, when hauling tons and coming off the mountain .

only analogy may be a touring tandem rig, they have long added a 3rd drag brake to control
their speed.. hub mounted, + the rim brakes.

Bekologist

I'm a big fan of high speed descents, and I'm a fan of the 'increased pressure" alternated with free rolling.

these two videos were shot one hand on the bars......



and







In my experience, I've found a loaded touring bike can handle severe deacceleration without loss of stability or control. YMMV, always use your better judgement.

However, I will advance that coming to a complete stop and admiring the view for a couple minutes is sometimes the BEST breaking technique for long descents.

Carbonfiberboy 

Our touring tandem has an all-up weight of about 400 lbs. We've done a couple of difficult descents with just V-brakes, Kool Stop pads. Alternate brakes. Hit them hard and let them go. Do not drag the brakes. Sit up and keep your knees out. Let the bike run as much as you can. We're a lot heavier and more aero than a touring single, so we hit 50 sometimes. Your rims won't overheat unless you cook your pads. You'll know your cooking your pads if you hear a sort of crackling/popping sound and lever effort increases noticeably. If that happens, stop while you still can and let the rims cool. Stopping to admire the scenery is never a bad idea when touring. Your cooked pads will fix themselves with a few hard brake applications soon after your stop.

AFAIK the only tires to blow off overheated rims have been wire-beaded. The supposition is that the wire retains heat and eventually melts the bead. Tires do not seem to blow off rims from pressure alone. For complicated reasons involving physics, too complicated to explain in a short post, large lower pressure tires are not less likely to blow off than smaller, higher pressure tires. The opposite may be the case.

We have added a drum brake for additional control when touring in areas in which we have no good data on gradients. For those of you who use alcohol stoves, we have noticed much improved braking performance after wiping the rims with alcohol. We recommend it.

Jim Kukula

I have been trying to work through this sort of thing lately. Here's where I'm at so far: At a fixed pressure, the tension in the tire increases linearly with the tire width. But the recommended/optimal pressure decreases with the -3/2 power of the tire width. So the tension on the tire should decrease as the inverse square root of the width, when pressure is reduced to those levels.

Another factor is the width of the rim. For a fixed rim width, a wider tire will be pulling more out to the sides, parallel with the wheel axis. Narrower tires on a wider rim will pull more centrifugally. I suspect it is this sideways pull of the fatter tire that is the big risk in a tire blowing off the rim. That problem should be much less on a wider rim.

I run 50mm wide tires on a 19mm wide (inner well width) rim. I think I would be better off with wider rims... maybe someday!