bendembroski

If you are looking for something that performs like disc brakes, you should probably get disc brakes. There's a reason that some folks prefer drums, others discs, and other rim brakes. All are superior to the others depending on your criteria.

Ultimate stopping power under a wide variety of conditions? Get some high quality discs. The downsides relative to rim brakes are they cost more and they are heavier. It's also more complicated to get spares for them when 'on the road', you need the appropriate mounting hardware on your bike for them, and you need disc specific hubs on your wheels. For some, these are all compromises they are willing to make for the benefit of having 'ultimate stopping power'.

People that say 'rim brakes should be good enough for most people' don't find these compromises acceptable, and prefer the lighter / simpler setup of 'conventional brakes'.

The same is true for drum brakes. They offer some distinct advantages over disc and rim brakes. They better rim brakes in the wet, they are the cleanest of all the options & they require the least maintenance. The biggest advantage they have over discs when used on a folder is there is no rotor to interfere with the fold, or to get bent when schlepping the bike about. Until you've used a folder quite a few times you won't know how much of an issue this will be for you. I'm sure it's no problem for some. For me, it would a deal breaker. I was constantly having to deal with a bent rear mech on my Swift from it being knocked around all the time, which is why I went with an IGH. I don't think disc rotors on my particular bike would last all that long. A badly bent rotor isn't going to be the highest perfoming braking system.

There is a reason that not many folders have discs fitted. It's probably a similar reason to why you don't see carbon-fiber folders.

I can't imagine you would ever be able to overheat drums from the stop-start of downtown riding. The 1000' descent? Maybe ? I've done 600 footers with mine and had no issue, but I'm not an aggressive descender either.

For what you are talking about using the bike for, you need decide if the vulnerablity of the discs are worth their improved stopping power over drums. I ride in pretty similar conditions to what you describe (aside from the monster descent) , and the SA drums on my Swift have never disappointed me with their performance wet / dry / downhill with trailer / ice / snow / 30 MPH or just pootleing along.

chucky

With folders people seem to be concerned about the rotors getting bent when the folded bike is tossed around. Whether or not this fear is founded I don't know b/c I've never had a folder with discs.

But the front suspension Downtube has been selling stock with a disc ready fork for many years now. If you're concerned about being on the bleeding edge I'd go with that (I'm upgrading mine to rigid if you're interested in buying the old one to equip a Swift)...or just make your priorities clear to Bike Friday (who I'm sure will be happy to accommodate you by overbuilding your fork...I have no doubt they're capable of getting it right the first time, just most customers don't want a 1200g fork).

Drum brakes REQUIRE road levers in order to operate properly. I believe that's half the problem with people not finding drums up to snuff; They assume they should use V-brake levers because that's what most commuter bikes use, but this is incorrect. There's also a lot of confusion among the uneducated about terminology (drum vs roller vs band vs coaster), the quality of various brands (SRAM vs Sturmey Archer), and the strength of various models (70mm vs 90mm).

But, no 70mm drums will not match the power of discs. If you don't find properly adjusted V-brakes adequate in clean, dry conditions then you won't find drums adequate either because that's how well they work all the time (dry or wet). I myself find rim brakes just fine after a tune-up on a sunny summer afternoon, but perhaps you don't.

As far as maintenance goes, drum brake pads are known to last decades. You can say it only takes 30 seconds to replace the pads on your discs, but that's after you've taken the time to periodically check the pads and purchase new (compatible) pads; Plus it's one more thing on the list of maintenance tasks which need to be performed: 30 seconds here, 30 seconds there, pack the bearings, oil the chain, replace the cables, true the wheel, rewrap the bars, fix a flat...before you know it you've spent hours or days on maintenance.

I also doubt you'll overheat the drums: Portland's very temperate and the drums have a lot more surface to dissipate heat than discs. I found the following account in the Mechanics subforum:
"Yep, I run SA Elites on my brevet bike and have had zero issues in 20+ years. While descending a very steep hill at 50+mph in France in '91 I had to grab a few handfuls of brake lever to panic stop for a red light (blowing it would have been fatal). I managed a text book, controlled stop at the signal. The guys I was riding with caught up and one asked "Who burned a clutch?" I said "Watch this" and spit on my front hub. The 'sizzle' was telling of how hot they can get."

+1 I'm not out the convince GlowBoy he should switch from discs (after hearing him out I think that's what he should get)...I'm just trying to clear up some of the misinformation that's out there about bicycle drum brakes.

GlowBoy

Good to know! That might explain quite a bit, since V levers have only about half the leverage of road levers.

I'll plead ignorance on these differences myself. If I were to go with drums I'd have a lot of research and learning to do. I'm not completely ruling out the possibility of going with a REAR drum at this point. Not saying I'm convinced it will work as well as discs for me, but I'm not totally dismissing it either.

No, I do find them just fine under the ideal conditions you describe. It's the worst conditions where they let me down (and discs don't).

You make a good point about certain maintenance items being more bothersome to some than others. I find it a non-issue on discs; I don't "periodically check" the pads either: they warn me by starting to sound "crunchy" well before they're fully worn out, and they're still somewhat functional even with the pads completely shot. But I despise the maintenance associated with rim brakes, having to clean rims and/or pads every week or two during the worst of the riding season when the last thing I want to do is work on my bike.

Just to be clear, the 1200g fork weight I was referring to was with 468mm legs. Even an overbuilt rigid 20" fork would be much lighter than that. (And unfortunately the Downtube fork is quite a LOT more than 1200g, so definitely not my first choice).

True, we don't have day in and day out of heat, but we do occasionally get very hot days. I have done that big descent in 106 degree heat, and as a year-round commuter my folder still needs to be able to handle it. Not saying drums aren't up to the task, just saying.

vik 

If you have trouble stopping a bike with v-brakes there is something wrong with your bike.

My Mtn bike has discs and if you replaced them with v-brakes you know what would happen?...nothing I'd be riding the same trails and stopping in similar fashion.

chucky

Personally I don't like drums for the rear because it's too heavy for something that's not going to be doing much braking (as are discs). In fact some of my bikes don't even have rear brakes (which saves on weight AND maintenance)...but that's just me.

In my opinion there are two things on a bike where every little bit helps (weight and maintenance) and when I upgrade my bikes these are the things I chip away at...a few grams here, one less brake pad to change there, etc. Mile per mile, bicycles are pretty piss poor on maintenance compared to just about any other vehicle you can imagine. That's why I try to be vigilant about reducing maintenance in any way I possibly can.

I wouldn't be so sure about that because economies of scale are working against you. I just bought two forks for around $100 each which weigh ~300g and ~500g, respectively. Guess which one is 700c and which one is 20" and guess which one has a higher weight limit?

BTW someone said they weighed the DT fork at 1600g...so maybe it's not quite 4.5lbs and remember it is also a suspension fork.

GlowBoy

Yeah, there is no way in hell I'm going without a rear brake. But I can see how those who are comfortable with 30% less braking power (that is, on bare pavement -- on snow and ice you're giving up MOST of it!) might not consider discs too relevant.

Ain't that the truth! One of the tough sells in getting people out of cars and onto bikes is getting used to the idea that periodically you WILL need to stop by the side of the road and work on your vehicle, at least to change a tire. (And reducing maintenance is a big part of why I prefer discs to rim brakes, though I now recognize drums would be even lower as long as I did not abuse them).

No, that's not outrageous for a suspension fork [even a 20" one ]. I'd dismissed it based on a presumed 2000+g weight, but at 1600 it's not a ridiculous choice. Too bad that isn't an option on the Swift (with its unusual A-C length and tapered steerer) or combined with the Xootr frame (and comfort with a rear drum/roller -- not completely ruled out) it would be a nice, low-cost option.

chucky

I don't think I lose 30% braking power. I don't think I lose any. I think wikipedia puts it best when it says, "The skidding of the rear wheel can serve as a signal to reduce force on the front brake; a skillful cyclist in effect becomes a human anti-lock braking machine, thus they must use both front and back brakes". IMO that's all the rear brake does...more of a convenience than an actual stopping device.

Also in really slippery snow and ice I find the only strategy that really works is to ride slowly and avoid braking as much as possible because rear braking leads to fishtailing and front braking leads to the entire bike slipping over. If anything I use more front brake to give feedback because bicycles need traction to balance and steer, so if you don't have enough front wheel traction to brake you probably don't have enough front wheel traction to balance and steer either. IMO in the worst conditions you need to go slow enough to Fred Flintstone, which will provide the most braking and control under such extremes.

YMMV

This is one reason why I also prefer 20" wheels: There's much less of a weight penalty for puncture protection.

Well, I'd expect any suspension fork to also have a large A-C length because there needs to be room for the suspension to travel. But of course the whole concept is kind of fuzzy since suspension forks really have variable A-C lengths (and variable head tube angles).

Also, the Swift's tapered steerer isn't really a big deal. It uses a normal 1-1/8" headset so all you need is a different riser to fit the 1-1/8" (vs 1") steerer top like this one:
https://www.calhouncycle.com/productc...&idproduct=978
But with the threaded DT fork there's also the whole issue with clamping the (stem) riser to the steerer threads (AHA! I just realized that's why the Swift fork is tapered...so a threaded headset can fit over the unthreaded portion of steerer).

If you're seriously considering the DT fork I'd double check the weight with downtube.com where they sell it as a spare part. It's not the best fork in the world (although the newer ones are better than mine), but that's always been the problem with suspension: good ones cost a lot of money.

GlowBoy

Well, my mileage does indeed vary. I'm certainly not going to pick a fight with you about braking technique. You and I obviously have different beliefs and philosophies about it, and that's fine. I do thank you for all the constructive advice and feedback.

bendembroski

Whatever you wind up going with, be sure to show it off. It sounds like it's going to be one of the more unusual builds on the forum.


(I mean that in a good way.)

vik 

Here is a Bike Friday with discs and canti posts - no need to choose...

GlowBoy

Still pondering the idea of a REAR drum brake. Then this evening it dawned on me that we have a bike in the house where I can test one out. Duh. My wife has a Bianchi Milano with a Nexus 8-speed hub, and I'd forgotten that it has a rear roller brake. Upon closer inspection I see that it's even hooked up for the proper cable leverage ratio. Its Nexus levers each have TWO cable attachment points with different leverage ratios: the cable to the front V-brake is in the left lever's hole marked "V", and the cable to the rear roller brake is in the right lever's hole marked "R-C" (whatever that means).

Took it out for a quick spin around the neighborhood and down some moderate hills tonight. Sure has a different feel than rim or disc brakes -- as others have mentioned it felt "mushy" and didn't develop full braking power quite instantly like other types. And its power was considerably less than that of the (dry) front V-brake, but it was more than enough to skid the rear Kenda Quest, a reasonably grippy tire.

Not sure how it will do coming down a big hill on dry pavement, but I'll try that in a few days (once things have cleared up from the snowstorm that's supposed to roll in later tonight). Didn't seem like as much power as I'd want on the front, but seems more than adequate for a rear brake as long as it doesn't fade too much on long descents - which I'll get to find out in a few days.

bendembroski

This is complete conjecture, but most of the stuff I've read where people have been complaining about drum brake's stopping power has been in relation to Shimano roller brakes.

The SAs seem to be held in higher regard.

I'm sure there is plenty of evidence to the country, but that's been the impression I've gotten from casual browsing on the subject.

GlowBoy

I don't know, I think I've seen comments from both sides on that one. You have the S-As, right? Searching through some past threads on IGHs and drum brakes, there are several comments (particularly from Batavus, who is in the Netherlands and claims to work on them a lot) saying the S-A drums are garbage, especially from a maintenance perspective as crud gets in through the seals, and that the Shimano roller brakes are better. Some people were refuting him on the contamination point though, so I'm not sure what to think.

I am toying with the idea of the S-A 5-speed IGH with drum brake. It's cheap, and a full pound lighter than a Nexus/Alfine with roller brake. The gearing range would be good enough for most of my purposes except touring (and for that rare use I could swap in a smaller chainring and shorter chain to lower the overall gear range; not a big deal). I could live with the middle 33% gear steps (I've gotten used to a SRAM 3-speed with 36% steps), and the overall range is not much less than the Shimano 8-speeds. I would still prefer the steps of the SRAM P5 to the S-A, but it looks like the drum brake P5 has been discontinued for several years. A SRAM P7 with drum would be ideal (and only 80g heavier than the S5 according to spec, still far lighter than the Shimanos), but those are equally scarce.

bendembroski

Hee.

Like I said, plenty of evidence to the contrary...

I suspect this is another one of those steel / aluminium arguments. All I can offer is that I'm perfectly happy with my S-A's, but they are the only drum brakes I've used regularly. I'd be curious if you have any links that might shed light on the subject.

chucky

According to the manual C is for cantilever brake and R is for roller brake. Also according to the manual, the Shimano "Roller Brake" achieves braking by pressing two metal surfaces together with grease to create friction (like a coaster brake!); Not very good at all compared to the type of drum brake used on cars with friction pads/shoes.

My Sturmey Archer front drums are sharp. Can you imagine how poorly your disc brakes would work if you had thick grease instead of pads? Although with all that grease I have no doubt that the Shimano Roller Brakes are very well sealed.

Shimano "Roller Brake":


Sturmey Archer Drum Brake (70 and 90 mm versions):


Even apart from the metal brake pads, the Shimano just looks anemic.

If you're going for a full bore practical vehicle with an IGH then might I also suggest a dynamo? Here's an article from a fellow Portlander suggesting that all bikes sold throughout the entire country should be equipped with them:
https://bikeportland.org/2008/10/21/t...t-problem-9660

Towards that end, you could spend $400-$500 on a disc brake setup (including disc fork, dynohub, and disc brake) or you could get the Sturmey Archer X-FDD combined drum/dynamo front hub built into a complete wheel for <$100.

atman

I feel compelled to respond here, because no one has correctly identified the physics involved.

A rim brake works better on a smaller wheel. The common suggestion is that because the rim is moving faster on a larger wheel, disk brakes should be more effective. This is simply not correct; the amount of rim passing a rim-mounted brake is a function of speed and is independent of wheel size. Think about it: the wheel is where the rubber meet the road. How could one rim be moving faster than another if the two wheels are going at the same speed?

However, there's less rim in total. In wet weather, this means a faster clearing of the moisture and grime on the wheel, because the wheel will take less time for a given speed to complete the first revolution, which is essentially windshield wiping. The brake bites down noticeably faster.

Similarly, a smaller rim stores less grime and dirt, therefore the pads pick up less schmutz per use and have to be cleaned less often.

I can lock up the wheels on my Brompton, effectively instantly. For the first couple days I thought it was mushy, then realized it was merely the handlebars flexing: feels alarming until one is used to it but harmless to my stopping speed.

That all said, disks work great, you like them, why not get them?

bendembroski

A smaller rim makes more revolutions to travel the same distance. Speed is a measure of distance traveled in a given time frame. So, a small wheeled bike's wheels will be making more revolutions per minute than a large wheeled bike at any given speed. More revolutions, more brake wear. Of course, discs on a small wheeled bike will be rotating faster too.

chucky

Yeah, but like atman said, for a tireless wheel the total amount of rim sliding across the brake pad is the same because more revolutions x smaller rim = same total rim "development" (as in "meters of development"). So the brake pad wear will be the same, although rim wear and heating will be increased. However, what atman neglected to recognize (apart from the extra rim heating) is that since the tire is proportionally larger on a smaller wheel it actually is moving slightly faster because it's proportionally closer to the hub. So rim brakes on a small wheel are a bit like using caliper levers and rim pads on a disc brake...which doesn't work well because the leverage is slightly off and the pads are too soft to handle such intense friction (which completes the double whammy of compromised pads + rim). Also, the brake pads themselves are closer to the muck, so even if the rims squeegee faster the squeegee is much dirtier.

On the other hand, hub brakes (discs and drums) really are moving much faster on a smaller wheel because more revolutions x same hub = more total hub "development". Moreover, unlike soft rim brake pads, disc and drum pads are capable of handling the extra friction and heat of the more intense braking because they're optimized for braking as opposed to rim preservation.

All in all the effects are subtle and can be compensated by using brake system components of otherwise excellent quality.

atman

Neglected to mention is more accurate than neglected to realize; the proportional difference you're talking about is extremely subtle, and unless you get different bite for the same brakes when you change from fat tires to skinny ones, forget about it.

Rim heating, on the other hand, should definitely have been mentioned, because it can be a big deal on a smaller rim if one has long descents while braking. Although if anyone has ever popped a tire on a folder by overheating in this way, I haven't heard about it.

The fact that the brake pads on a small-wheel bike are closer to the muck is canceled by the fact that the brake pads on a disk brake would also be closer to the muck. Bottom line: small wheels are different enough from big ones that both disk brakes and rim brakes benefit quite a bit from being specifically designed around the smaller wheel.

GlowBoy

OK, NOW you guys have done it. Not only am I really leaning towards the Sturmey XRD5 (5-speed IGH with 70mm drum) ... ehhh, I hate to admit it, but ...

You've got me considering a front drum. Dammit. I've spent a lot of time the last couple days researching old threads here and elsewhere, and the more I read the more I'm intrigued. Like I said, even the Shimano roller brake seems more than adequate as a rearbrake, and by all reports the S-A drums (with actual brake pads in them) are far, far better. As in, probably good enough for the front too. There are reports on the yahoo IGH group that the 90mm XL-FD hubs are as powerful as the Avid BB7s, and of course with the same advantages in terms of weather resistance, though about 400g extra weight vs a front disc setup. The 70mm X-FD would have about a 200g penalty, and might even be sufficient. The 90mm's flange height is only a couple mm bigger than the 70mm, so presumably it too can be built into a 406 wheel -- though I'm not sure if it's overkill yet. A front drum would still subject the fork to the same bending loads as a disc brake, though if the Swift fork is as beefy as folks are saying it should be up to the task.

Bendembroski, you're running 70mm front and rear on a Xootr Swift, right? How much does the fork flex under hard braking? Also, I just read your "smoother Xootr" post from last year -- can I assume you've got the brake and shifter cable routed as they are because the hub requires chainstay routing? Actually looks a lot nicer and more symmetrical than I would have expected. I wonder if anti-turn washers intended for semi-vertical dropouts (if Sturmey offers them), facing forward in the horizontals, would result in a good orientation for seatstay routing? Just thinking out loud.

As for the rear hub, the reports on the Sturmey 5-speeds seem to be that they are very solid (unlike the VERY mixed reports on their 8-speeds), and as I mentioned above the gearing is about perfect. For 6 of the last 7 winters I've commuted on a 3-speed IGH (SRAM DualDrive Disc with a single cog), and for big hills I've always wished for one or two more gears, which is exactly what this would give me. In fact, the overall range would be almost identical to my fair-weather derailer commuting setup. Quite a bit lighter than the (overkill for me) 7 and 8 speed hubs; at 1630g with a 70mm drum, I up with almost exactly the same total drivetrain+braking system weight as with a rear cassette+disc arrangement. Since I hate grip shifts, fortunately for me Sturmey is also offering a wide range of 5-speed compatible shifters including both bar-end and trigger options.

Dynocoaster 

I had my wheel built by this outfit and shipping was free, I had a Duomatic built but this 8 speed is nice https://www.treefortbikes.com/home#na...22358456___716

SesameCrunch

I can give you a specific case. My Downtube Mini, descending Alpe d'Huez on the Tour de France route. Heated rims, blown tire. I had loaned my Mini to a friend, and he and his girl rode up Alpe d'Huez. Full story here:
https://www.bikeforums.net/showthread...ht=europe+trip

Teaser picture here:



Blown tire here:
[/QUOTE]

chucky

I've been thinking about this and I wondering if a drum:
-concentrates the force more at the dropouts
-distributes the force across the axle and more evenly between the fork legs
-is more likely to "fail" by flexing the reaction arm fixture rather than snapping the leg off altogether

In any case as a light rider I welcome the opportunity to have a good practical bike that isn't overbuilt. All the discs forks out there are way stronger than I need them to be (knock on wood).

jrecoi

The drum brake pads are attached through the backplate to the reaction arm, which in my own X-FDD was pretty long, something around 5-6 inches, and was rather thick and solid. The braking forces are thus transmitted from the pads to the tip of the reaction arm where it contacts the fork. Compared to a disc brake where the "reaction arm" is quite short, the stresses the fork experiences with a drum brake are lesser.

Some builders of custom hubs like Wrath-Sharman made the reaction arms for their drums very long, all the way up to the fork crown in front hubs.

https://www.63xc.com/dws/hubbrake.htm

chucky

Thanks for sharing your knowledge!

I was also thinking that since the reaction arm "contacts the fork" via a clamp or braze on, worst come to worst the clamp will break, letting loose the reaction arm, and ceasing brake operation. Not a good situation, but better than snapping a fork leg like we've seen with disc brakes.