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  1. #1
    Senior Member BigBlueToe's Avatar
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    Efficacy of front discs only?

    I was just reading a thread about the Kona Sutra. There was some controversy about the disc brakes on a tourer, and the problems they pose for mounting a rear rack.

    I got to thinking - since the front brakes do most of the braking (read Sheldon's article on braking if you haven't), why not put a disc on the front and canti's or V-brakes in the back? My old motorcycle has a disc in front and a drum in back.

    Just a thought. Any reactions?

  2. #2
    Forever CLYDE ! cyberpep's Avatar
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    I think that front disc's are a great idea. The front Canti's on my Cannondale T2000 suck most of the time. Even with salmon Kool-Stop pads they will not stop me when it is wet plus I have constant fork shutter as I am just about stopped. A friend has a Giant OCR Touring bike with disc brakes front and rear and can pretty much stop in any type of weather, loaded or unloaded.
    I think that any rack mounting problem can be worked out with disc brakes. You can always seem to find a mechanically handy fellow who will take on the challenge to modify your racks to fit any bike.
    2003 Giant Cypress R
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  3. #3
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    Why don't manufaturers just start putting the calipers on the chain stay like god intended?

    -Rob.

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    Quote Originally Posted by robcycle View Post
    Why don't manufaturers just start putting the calipers on the chain stay like god intended?

    -Rob.
    This is such a no-brainer for rack-able bikes Im astounded that only boutique bikemakers such as Gunnar use the chainstay mount. Is there some advantage to putting them on the seatstay ?.
    My boss just got a new Scott hybrid and I was very impressed to find a chainstay ISO mount from a fairly mainstream brand.

  5. #5
    cyclopath vik's Avatar
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    I'd stick with rim brakes or discs...carrying parts and dealing with 2 different brake systems on a touring bike doesn't make a lot of sense.

    Having toured with discs and v-brakes I prefer v-brakes for a host of reasons spelled out in detail on previous posts in this forum discussing the disc vs. v-brake/canti question.

    There are quite a few racks [old man mountain] that work with disc brakes so if you really want to run discs I'd just get compatible racks and use two discs.
    safe riding - Vik
    VikApproved

  6. #6
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    There are racks that will work with disc brakes and plenty of ways to get a rack to work - even with BB7s.

  7. #7
    VOTE FOR KEN WIND Ken Wind's Avatar
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    I agree that it sounds like more trouble than it's worth having a different type of brake front and rear. There are bikes that come stock that way though, such as the Kona Ute.

  8. #8
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    I've used discs on front only, rear only, both, none.

    Discs brakes brake the same or only slightly better than a great V brake setup in dry weather. They do tend to modulate better - that is, you can control intermediate braking force easier. Rim brakes are more likely to be either slightly engaged or nearly fully engaged (or locked up). Not much gradient in-between.

    In wet weather, discs are superior, from a little (drizzle) to a lot (downpour). Rim brakes require more wheel revolutions and pressure to remove the water on the braking surface before they start to actually brake. In heavy rain, where rain puddles and splashes rim constantly, you never get them dried off to actually brake worth a darn. Disc has advantage or keeping braking surface (the disc itself) up out of the collecting rainwater. So, the wetter it is, the more advantageous disc brakes become. I've had a few scares when my in-dry-weather-super avid rim brakes would not stop me rolling down a hill in a downpour at only 5mph heading into a busy intersection. Had to employ emergency Fred Flintstone braking manuever.

    Disc on front only is cheapest way to experiment - you just need brake, wheel and fork. Disc adds at least 250g per wheel over rim brake. They just weigh more between caliper+pads+mount, hub+disc+mount, full housing run, heavier fork, heavier rear frame triangle and heavier wheel build. Switching from full rim brakes to full disc brakes will add 2 lbs weight minimum to your bike. This is mostly hypothetical since few touring framesets give the option of switching from rim to disc. This is an equipment decision you make when buying a new bike, because the total conversion cost is cost prohibitive.

    You can go a long way on Avid SD7s or SLs with good pads, adjusted properly. Combine with Tektro 520 levers (or Cane Creek version) to keep road brake levers. If I were running cantis, I'd try Vs first before taking plunge to disc.

    The hard part of a front disc only conversion is trying to find an affordable, disc-capable fork with axle-to-crown distance to approximate that of your current bike. Most MTB disc-capable rigid forks are 410-450mm a-t-c. The Kona Sutra uses a 390mm p2 fork with rack mounts. I have one, it's OK - not as nice as a $35 Tange fork IMO. Weighs exactly 1045g uncut. 980g after cutting off 65 mm. Nashbar has a carbon disc fork (made by Aprebic, exact same fork as Winwood, a QBP brand) with 385mm a-t-c.

    Maintenance wise, disc are easier than Vs. After initial setup you turn a knob or two 1 click once every couple months. My disc pads have lasted longer than rim pads - probably twice as long (but they cost twice as much, so its a break-even deal). Pads just drop into caliper, turn 2 knobs. Skip the whole "I need 3 hands to setup brake pads with proper toe-in, while hunched over for 20 minutes" ordeal.

    I recommend Avid mechanical disc brakes. You can get them for 50 bucks. No fluid to bleed, leak or spill. No special lever required (works with all rim brake mtb levers). For drop bars you'll want the harder-to-find avid road disc, or just get tektro 520 levers (probably better idea).

    For a dedicated touring bike, I prefer V brakes as they offer best braking for least cost, weight and complications. For a dedicated commuter bike, I prefer disc. Good brakes are essential in the rain, especially when there's traffic nearby.
    Last edited by seeker333; 09-23-08 at 05:52 PM.

  9. #9
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    I'm building a bike with disc brakes and cantis on the front wheel, and cantis on the rear wheel. This is one of those, "I had an experience builds", which are always a lot of fun. I could certainly see having a mix of brakes on a touring bike. There are plenty of advantage, and I really don't see the parts problem. The BB7 brake has less maintenance issues than my straddle cables that require two wrenches. Different brake systems are a comon idea on bikes, as are three brake systems. It's a sad fact that my touring bike is trotting along with as much weight abord as the average tanden, so some redundant braking makes sense.

    I think that discs on the back make sense on MTBs where stuff like mud is a main motivation. But that isn't a problem on my touring bike, and rim brakes will hold the rear wheel easily. Were the front wheel needs extra braking power, having two different systems on the bike allows stopping power redundency, a blend of performance and wheel loading. Sure it is a little heavy, but a lot less so than Rohloff or Big Dummy.

    My own build is sorta stuck since while I have the hub, brake, and fork, there are other options that don't call for a dished front XT wheel build. Probably will happen, but not certain to make the cut. Another option is two rim brakes up front.

  10. #10
    40 yrs bike touring
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    After all these years my favorite brakes are still the WTB/Cunningham Roller Cam Brakes on the fork and under the chain stays on our Fat Chance Mountain Tandem and single MTBs. Too bad they no longer make them.

  11. #11
    Golden Member JR97's Avatar
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    I've got disc on the front v's on the rear of my mtb. Works just fine. My tourer build will be setup that way. I've got full disc on my road with the rear caliper on the chain stay. No rack issues whatsoever.

    Now that I've had discs on two bikes and V's on one, I like the simplicity and hastle free nature of mechanical discs. Turn a knob to adjust every once in a while. Wheels plop in and out with ease. Performance wise, they work well in any condition. I've never tried the kool stop V's, but even the stock V's on my bikes have worked just as well if not better in the dry. I can see how a hot warped rotor would be much cheaper/easier to deal with than a hot warped rim. A warped rotor can still be functional although it would be annoying and inefficient when not being braked on.

    Also, you can go with a fork that has mounts for both disc and v/canti's. Try both. Adjust to taste.

  12. #12
    Videre non videri
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    Quote Originally Posted by seeker333 View Post
    I recommend Avid mechanical disc brakes. You can get them for 50 bucks. No fluid to bleed, leak or spill. No special lever required (works with all rim brake mtb levers). For drop bars you'll want the harder-to-find avid road disc, or just get tektro 520 levers (probably better idea).
    Or the Dia-Compe 287-V levers.

    I'm suprised that after you took your time to explain all the advantages of a disc brake over rim brakes, you still recommended rim brakes for a tourer.

    Later this year, or next year, I'll be rebuilding my road bike, and I will put a front disc (BB7 road) on it then. I'm getting a new frame and fork anyway, so I'll just make sure the fork has disc brake tabs. I had already planned to upgrade the rim brakes, so getting a front disc instead is actually slightly cheaper. But I will need a new front wheel, so that'll set me back a bit more...

    The reason for this is that I had a very scary moment in June, when I had been riding in light rain for maybe 15 minutes and I had to brake hard to avoid a collision. Braking power was close to zero at that point, so I had to steer off the road into a grass field!

  13. #13
    weirdo
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    Quote Originally Posted by vik View Post
    I'd stick with rim brakes or discs...carrying parts and dealing with 2 different brake systems on a touring bike doesn't make a lot of sense.
    Aren`t the cables and levers the same for mech discs as for Vs? If so, that only leaves one more set of pads to carry. And that`s only if you want to. As for me, I`m sticking with V brakes or side pulls on all my bikes just `cause that`s what I already know.

  14. #14
    __________ seeker333's Avatar
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    Quote Originally Posted by CdCf View Post
    Or the Dia-Compe 287-V levers.

    I'm suprised that after you took your time to explain all the advantages of a disc brake over rim brakes, you still recommended rim brakes for a tourer.

    ````````````
    The reason for this is that I had a very scary moment in June, when I had been riding in light rain for maybe 15 minutes and I had to brake hard to avoid a collision. Braking power was close to zero at that point, so I had to steer off the road into a grass field!
    Yes, my writing needs improvement. My post was intended as a reply to the OP.

    What I meant was - if you're intent on getting disc brake, then i can recommend the avid mechanical bb7, as it's simpler to use and maintain, inexpensive and effective, compared to other discs, especially hydraulics.

    For a tourer, disc brakes are something of a liability. They add weight, expense, unusual equipment that would be more difficult to replace if needed, complications for attaching racks, and just one more reason for someone to covet an unattended bike.

    For commuting, it's more important to be able to stop quickly in the rain. You're far more likely to be riding on busy highways during rush hour on a commute, than on a tour. So this is a more valid case for disc brakes.

    To add further confusion, I'll recommend to you in Sweden, that if you operate in a wet, sub-freezing environment regularly, you may want to consider the extra cost/trouble of hydraulic disc brakes. The reason is that water can get into the brake cable housing and freeze, rendering a cable-actuated brake inoperative. This is nearly impossible in a hydraulic brake system. Something to think about.

    I had a similar frightening experience which served as final impetus in converting to disc brakes, where I nearly rolled into highway traffic in pouring rain because my rim brakes wouldn't bring me to a stop. Thus my allusion to Fred Flintstone. Perhaps you weren't watching American television on Saturday mornings in the 1960s, so here's a visual aid (note propulsion and braking by operator's feet, which is also how I had to stop on these aforementioned frightening "rain stops"):
    Attached Images Attached Images

  15. #15
    Golden Member JR97's Avatar
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    Quote Originally Posted by rodar y rodar View Post
    Aren`t the cables and levers the same for mech discs as for Vs? If so, that only leaves one more set of pads to carry. And that`s only if you want to.
    They are the same. And that extra set of pads is a real back breaker to carry. Might have to leave behind something vital. Like a tooth brush or something.

  16. #16
    Videre non videri
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    seeker, where and when you tour is a factor as well. A tour through Northern Europe, for example, would not be an issue with mechanical discs. Spare parts would be available almost anywhere there's a bike shop.

    And I would never recommend hydraulic discs for anyone outside of the various mountain biking riding styles. For a commuter or a tourer, mechanical would be the only sane choice. I've never had a problem with cables freezing, and I don't know anyone who has, apart from the cyclists who never take care of their bikes (pump the tyres 2-3 times a year, never clean/oil the chain - you know the kind).

    If you have a tourer, you could set it up to be able to use both mechanical disc brakes and V brakes. That way, continuing on a tour would only require buying a cheap set of V brakes, which can be had for almost no money in larger department stores and every bike shop there is around here.

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