How Fred would this be?
 

Here's a question I could pretty much only get away with on this forum, and maybe not even here.

I'm a big guy with small, weak hands. As shameful as it is to admit, even with a properly adjusted front disc brake I have a hard time locking up the front wheel. My hands are just too small and too weak to get a lot of leverage, and it takes a lot to stop me. I can stop pretty well, but at a comfortable braking force I can still feel significant additional stopping power when I apply the front and rear brake (rear brake is cantilever, FWIW).

So....I've been toying with the idea of setting my bike up with a disc brake AND a caliper brake in front (my fork supports both), hooking the left lever up to the disc and the right lever up to the caliper, then maybe hooking the rear brake up to a cross lever. My thinking is that it would give me two different choices to modulate my stopping power and when combined should maximize braking force. My fear is that it would be too much and I'd end up throwing myself over the bars the first time I tried an emergency stop.

Anyone ever try something like this?

^ are you currently using hydraulic disc brakes? i only ask because hydraulic brakes are by far the lightest touch bicycle brakes i've ever used. they have a much, MUCH softer touch than any cable brake set-up i've ridden with and i can't imagine anyone (other than an amputee) not being able to lock up the front wheel on my hydraulic disc brake bike. the stopping power of hydraulic discs is just amazing.

No, I'm using mechanical disc brakes (BB7) with STI levers. With MTB levers I can get plenty of leverage because I can reach the end of the lever easily. The problem is that I hate flat bars. I've got some Ripcord cable waiting to be installed, and from what I hear that will give me a boost. I still think this would be a fun setup.

For normal braking, I can easily stop my bike using only my pinkies with hydraulic disc brakes.

Just about any well set-up brake should be able to put enough pressure on the rim with pretty limited hand force. The limit on braking force should really be where the rubber meets the road, not at the brake itself. In other words, you shouldn't have to go to the lengths you propose to get something that works for you. If your fingers are short, you may benefit from an adjustment of the reach of the brake, or even a smaller set of levers. I am 6'2" and can't quite palm a basketball, but I have wide palms and short fingers. On one of my bikes I switched my levers to smaller ones. That bike has bar-end shifters, though, so it was a pretty cheap fix.

I'd try a hydraulic brake first...

By the way, I'm not sure I follow this. What do you mean, exactly?

Here's the thing (trying to reset the spirit of this thread)...I have something that "works for me" now. In fact, I'm pretty happy with it. Mostly I'd be doing this for fun.

But everything you read says that the rear brake doesn't really add any stopping power, so given that with my usual braking behavior the rear brake does add stopping power then switching that lever to act on the front rim should add more stopping power, right?

As soon as an affordable hydraulic STI drop bar lever hits the market, I'm on it.

What I mean is that I'm squeezing the front brake and it's bringing me to a stop, but if while doing this I squeeze the rear brake too I feel myself being pushed to the front of the saddle. I haven't done anything scientific, but I'd bet that I can stop in a shorter distance using both brakes than just one, and "theory" says that shouldn't be possible.

You might be better off having this moved to the "bicycle mechanics" forum. Not sure you can take a brake designed to work with MTB levers and switch it over to STI? Travel lengths may be different? I'm sure someone in the know will soon chime in.

I've got the road version of the BB7, so the lever isn't wrong.

i 've read that too, but i don't necessarily believe it. on my road bike (ultegra calipers) i can definitely stop faster from the hoods when i engage both front and rear as opposed to just the front (from the drops, i can get better leverage on the brake levers and it makes less difference). simple physics tells you that the front brake does the lion's share of the braking work, but the rear brake is not useless in my experience of decades of cycling.

My guess is you aren't really likely to experience the situation where all the braking force has actually transferred to the front wheel when applying both brakes until you are just about to go over the handlebars. There is a reason you have both brakes.

You will be able to stop even faster (such as in an emergency stop) if you move your butt in back of the saddle while grabbing lots of front and rear brake. This will add more downward force on the rear tire so your rear brakes can add more stopping power than normal.

So here's where I'm geeking out a bit. You both seem to agree with my experiential conclusion that using both rear brakes does, in practice, shorten stopping distances. This has perplexed me for a while because of the stature of the people saying it shouldn't be so. I studied the force equations involved and mathematically there is no question that the absolute minimum possible braking distance is indeed achieved when the amount of force applied is sufficient to raise the rear wheel off the ground, and it does look like with proper weight distribution that leaves room for a safe stop before you go over the bars. Hence my theory that it must be possible to reduce my braking distance by adding more braking force to the front wheel.

FWIW, I have gone over the handlebars twice in recent years. The first time was when I was a rookie commuter 5 years ago, using V-brakes and an ill-fitting flat bar bike. I believe weight distribution was to blame in that case. The other incident was a crash in a cyclocross race where I was braking hard while going down hill. I know for a fact that that one was rider error.

Just to confirm that you have the right levers for the disc up front-- is the rear a canti or a v-brake and are you using a BB7 road?

Yeah, there are 2 BB7 brakes, one is set up for normal mountain pull and the other is set up for road pull. Since you're using STI, you need to make sure the brakes are BB7-ROAD not just BB7. This matters a *lot*.

"Everything you read" about using only the front brake is based upon a flawed interpretation of the physics of braking by road riders...who know very little about braking as a rule. While the maximum amount of deceleration you can realize is limited by the front brake, it's actually a trick of the math. If you are up on the front wheel without contact from the rear wheel on the ground and actually about to pivot around the front hub, that is the 'maximum' deceleration you can possibly realize from any brake. Most people don't want to brake that way.

When the rear wheel is still in contact with the ground, you haven't reached the maximum deceleration but you aren't about to experience asphalt dentistry either. But you are damned close to the maximum deceleration that you can achieve. The difference is minimal. The rear wheel, as long as it is in contact with the ground, is contributing something to the deceleration of the bike. If you are seated in a 'normal' riding position, the amount that the rear wheel contributes is around 0.1g. But the overall deceleration of the bike in that position is 0.5g. If you don't use your rear brake, you are giving up 20% of your braking power.

The deceleration ability of any bike can be improved pretty simply, however. Move the center of gravity, i.e. you, back and down even a little and the deceleration that you can squeeze out of the brakes doubles. A shift of your body by around 4" back and 2" down, increases the deceleration you can develop from 0.5g to around 1g. Watch a mountain biker brake. They throw themselves off the back of the saddle to increase their braking power and to keep the rear of the bike in contact with the ground longer. The last thing you want on a mountain bike is a nose wheelie.

Counteract that tendency of being pushed towards the front of the saddle by pushing off the back, you'll see dramatic improvements to braking.

Front is Avid BB7 road, rear is Avid Shorty 4, levers are Shimano Ultegra ST-6600.

Thanks! Your explanation accords very well with my experience. I'll play around with the weight shift.

But surely there is a champion of the almighty front brake on this forum who will come to its defense.

Meanwhile, I guess I'll need to find a different way to fredify my bike. ;)

The shortest stopping distance for straight line braking on dry, smooth roads is weight back, full on front brake, to the point that the rear wheel would just lift off the ground. This requires tremendous force on the front brake, flawlesss modulating, and excellent balance. However, this is not within the ability of most riders, and does not account for brake fade due to overheating, which is reduced when using two brakes. Also does not include wet or rough roads, where front wheel lock up is more likely, and turning when braking, which increases the likelihood of the front wheel locking and skidding out from under you.

Parallel Universes aside, would be a miracle of theoretical physics
to have the mechanical brifter
and the hydraulic master cylinder occupying the same, limited space .. BUT..

TRP now sells a cable to hydraulic kit so you can use your Mechanical Brifters,
which brake by pulling a cable.
they include the slave cylinder for both wheels hose and a dual master cylinder
that fits under your stem.

or...
I hope you Got the road BB7, if you got the Mountain caliper ,
that is your problem .. wrong part bought.

even with the road caliper, you could use the inline travel agent..
that bolts onto your cantilever boss. with housing on both ends.
and you can set up the amount of travel increase ..

then get the adapter to install a 210mm disc, rather than a 160mm ..

How new are these brakes? They take a while to "bed in", even longer for slow/easy commutes. SRAM recommends you do 20 hard stops to accelerate the process.

See:http://www.bikeradar.com/gear/catego...-parabox-45423