DVC45

Hello all,

I am converting my commuter bike to disc brakes. I ordered the BB7 road disc brake because, I am thinking of converting it to dropbars in the future.
I am just wondering if my current brake levers (for V brake) will work. Do I need to buy a different brake lever?

Thanks in advance!

JiveTurkey

As you mentioned, your supposed to use short-pull levers (for caliper, cantilever, and road discs), not your current long-pull levers (for V and MTB disc).

This should give you an idea on what using your current lever with those brakes may feel like: https://sheldonbrown.com/gloss_bo-z.html#brakelever

Are your current levers integrated with the shifters? If not, you should be able to pick up a pair of short-pull levers fairly cheaply until you convert to drops.

Retro Grouch 

If it was my bike I wouldn't hesitate to use long pull brake levers with short pull brakes. Unless you're a real wimp I doubt you'll even notice the hand strength issue.

The opposite, however, doesn't work because the levers bottom out against the handlebar..

ultraman6970

Hmm... depending on the lever you can change them to short pull. My best guess is that you will have to press too much the lever to get the discs to actually stop decently.

HillRider

I know what you mean but I think you have it phrased misleadingly. If the OP keeps the V-brake levers with the road discs he will have to press harder than usual to stop the bike. Lever travel will be quite short.

ultraman6970

Thanks. The other option is to use travel agents but dont know if its better to get new/used brake levers than get a travel agent.

AEO

as far as I can recall, shimano, sram and tektro all offer a flat bar lever for road brakes.

Metaluna

I was running BB7 roads for a while with short pull levers, and it always felt to me like they really "wanted" a bit more cable pull than the road levers could provide. Maybe it was just my inexperience setting up disc calipers, but it always seemed like the road levers were bottoming out before reaching full braking force. Conversely, if you set the pad clearance close enough to get good braking, the pads would sometimes rub against the rotor when the brakes were not applied.

I'm tempted now to try the road calipers out on my current bike that uses Tektro long-pull drop levers. That should allow more pad clearance for the same lever travel.

Retro Grouch 

Try using compressionless brake housing, like Jagwire Ripcord. That might be enough to make the difference.

LarDasse74

A bicycle brake is a mechanical device that transfers the force your hand puts into the levers into a cable tension that in turn creates a force at the wheel causing friction to work against the rotation of the wheels. Built into this system there is a certain amount of leverage that makes the relatively small force your hand can generate into a much larger force necessary to create enough friction to easily stop the bike. Long pull levers create much less (approximately half) cable tension than short pull levers do for the same hand force at the lever. The result is that you have to put approximately twice as much force into a long pull brake lever to get the same amount of cable tension you would get from a short pull lever. Now maybe you are Popeye and you just had a can of spinach, but most people - even non-wimps - do not want to have to double the hand force necessary to make the bike stop. I made this mistake years ago on an old 10 speed that had adequate brakes until I installed a long-pull brake lever - the brakes became a little bit stiffer feeling (like you said, you couldn't really notice) except that the brakes were entirely inadequate for actually stopping the bike unless you put waaa-aaaay more force into the lever than before.

All of this is just to say you are wrong and that long-pull levers should definitely not be used with brakes designed for short pull levers. If you don't mind a little brake rub, and you have good quality cables, short pull levers can actually be set up to work semi OK with brakes designed for long pull levers... but IMHO, even this setup should only be used to ride to the LBS to buy the proper brake levers.

fietsbob

If the caliper only requires a portion of the cable pull ,
you can leave some slack in the cable
to have the caliper grip the disc in the desired part of the lever range of motion..
of the lever,
If you haven purchased any levers, the speed dial Avid lever ..
adjusts a bit in that regard, or get cantilever mountain levers..

Retro Grouch 

That's a pretty long post and you've obviously researched this. Maybe you can answer a couple of questions for me.

1. How much hand squeeze does it take? 10 pounds is twice as much as 5 pounds, but 10 pounds still isn't very much.
2. What's the limiting factor in bicycle brake stopping power? My scariest experiences have been riding with chromed steel rims in the rain and riding a mountain bike down a snowy hill in really cold temperatures. I'm thinking that it's things other than hand strength.

fietsbob

Any how, older, cable out the top, road brake levers
have a middling cable pull.

not as much MA as aero road levers, but more than V brake levers ..

V brakes the MA is on the caliper end of the combination..

LarDasse74

My 'research' was more my physics and engineering education and knowledge of how the components work.

1. I don't know that exact amount of force required or commonly available from a person's hand for braking, but there is definitely a 'sweet spot' - an amount of force most people think is acceptable and are able to produce, and which also gives adequate clearance between the brake pads and braking surface, and provides enough friction to stop the bike in a reasonable distance. A brake that deviates from the 'sweet spot' generally takes too much hand force to stop the bike, or leaves the brake pads too close to the braking surface or bottoms out the lever. Generally speaking, most long-pull levers used with brakes designed for long pull levers (vs, most cable discs) fall inside this range, as do short pull levers with brakes designed for short levers (cantis (when set up properly), road calipers, road cable discs, calipers, centrepulls, mini Vs, etc.)

2. Two limiting factors are friction between the braking surface and the brake pads, and the position of the centre of mass of the bike/rider combo in relation to the front wheel and how this can make endoos or or less likely.
If eveything is working well (cables, levers, calipers) and you have a wet chromed steel rim, the friction between the brakes and the braking surface is the limiting factor. Riding mountain bikes inn cold temps has given my a few scary moments, too - when I tried to stop and had not noticed my rims were iced over and/or calipers were frozen solid. I wold expect that rubber brake pads in the extreme cold will also tend to be harder and have different friction properties than when warm.
If everything is working well in good conditions (say, a dry ride with well set up hydraulic discs with 8" rotors)) then the limiting factor is how much deceleration can occur before the bike and rider begin to endo.

DVC45

Thanks for all the info.

I decided to just use cantilever at the back, so I can use my brifters. But now, I have to order a cable hanger.

Retro Grouch 

I wish that I would have thought about tandems yesterday. It's a better example of the hand strength issue.

For general brakeing, tandems have for years used the same components as single bikes yet they have twice the weight and so require twice the stopping power. I never heard a tandem captain complain about lack of grip strength.

Even more, before disc brakes became common a typical tandem brake set up was to cable both canty brakes to one brake lever and use the left brake lever for a hub brake that was generally only used to dissapate heat on long downhills. I rode a tandem that was set up that way for a while and never had second thoughts.

DVC45

I still can't wrap my head around it. I'm not sure why long pull brake levers can't work with short pull brakes. But I'll read thoroughly the above posts and do some searches. But so far the canti is working great.

Thanks again everyone!

HillRider

The do work. What they require is a lot more hand pressure to achieve a given level of braking since their leverage (aka mechanical advantage) is smaller. It like trying to pick up a weight with a lever. The longer the lever you have, the easier it is to lift the weight but the farther you have to move your end to move the weight a given distance. A short lever moves the weight further but requires more effort.

AEO

imagine this:


If the lever was where the weights on the crane were and the crane pivoted with the cable in its current position, then the cable will not move much, but it will have a lot of leverage.
If the cable was moved all the way to the end, it will move a lot, but with decreased leverage.
Now imagine trying to lift the truck at the base with the hook. If the truck is further out, you have to add more weight on the opposite side to keep the crane from toppling.

DVC45

Aaaah, okay. It all make sense now.
I truly appreciate all the effort for educating me on the subject.

Thanks to all!

Man, I love this forum.