noimagination

Yes, but in poor traction conditions when slowing is mandatory (actually, in any conditions), skidding the rear wheel is often controllable, but a skidding front wheel is generally not - you're going down. Hence the disagreement in this thread with the postulate that rear brakes are superfluous.

tyrion

Using both front and rear brakes (properly, with less pressure on the rear brake) is simply safer. 90% of the time it's perfectly safe to just use the front brake, but when things get tricky it's good to have the both-brakes habit well practiced.

Eric F 

I agree that sometimes **** happens, and we have no choice. However, I've found that having a braking plan has reduced the number of "oh, ****!" moments I have. A big step forward for me was an improved understanding of how my body can contribute. Not just how I'm weighting contact points, but also my body position over the bike.

terrymorse 

More: Braking on hard pavement so much that the front wheel slides is next to impossible. (1) You'll flip over the bars first (which is also rather difficult).

1 - Exception is a tight turn on wet pavement (BTDT, have the repaired hip to show for it).

Ironfish653

Yes, and no; Cycco touched on this, that the CG is much higher on a velo, and the rider is a much higher proportion, and able to affect the weight distribution more dramatically. Rider weight might only be 20-25% on a moto, as compared to 80%+ on a bike, but actively managing that mass can still make a considerable contribution.

I think where it gets lost in translation is accounting for the effects of suspension. On a bike with front suspension, whether it's a moto or MTB, grab a bunch of front brake and you get "dive", the suspension compresses, the bars shift down, the rear wheel unweighted, everything shifts forward. This happens at a far lower braking threshold than what it takes to OTB on a rigid velo. You can't feel how hard a given tire is pressing on the road, but Dive tells you that weight shift is happening
On a rigid velo, you only have the deflection of the tire sidewall, so you don't experience the shifts in front end geometry, that tells you that weight shifts are happening, (and how significantly) so everything seems fine until you give it enough brake, hard enough to either lock a wheel or pitch you off.

tomato coupe

You've given some good examples of the 'yes' part. What's the 'no' part?

Daniel4

Just a short while ago in the middle of a ride, I had lost my rear brakes. I thought to myself that I could handle that because most of the braking was in the front anyways.

Well, at an intersection while I was turning right, I almost ran into a pedestrian crossing the street because my rear brake wasn't there.

Kontact 

A car pulled out.

Eric F 

In those kind of situations, all you can do is react instinctively, and try to save your own @$$ any way you can.

Claude.fr

The dynamics aren’t that different and laws of physics in relation to the energy dissipated in brakes applies equally to both, converting rotational motion into heat energy.

Double front disks brakes on motorbikes assisted by a smallish drum brake at the rear still existed not so long ago.
That wasn’t a sluggish rear drum brake stopping your motorbike.

Not much change, on modern bikes, Dirt bikes are a case in point, there is a considerable difference in diameter between Front and rear disc.
Even on dirt, you rely on your front
brake, principally.
Then, brakes are for losers.... but that’s another conversation.

Ironfish653

Sure, if I think I understand what you're asking for.
The big difference is in the CG, and how the rider can affect it.
So, taking away variables like suspension, a bicycle has a far shorter wheelbase, and since the rider is the major component of the mass 80-90% , the CG of the system is roughly the CG of the rider's body (the navel, give or take)
A moto (let's call it a 500# 650-class 'sport standard ') is the majority of the mass (60-75%, depending on the rider). The CG of the bike itself is farther forward, but lower, appx between the rider's knees, when mounted. Combined, the CG is somewhere between the rider's lap and the saddle, depending, but the triangle of the wheelbase and CG is lower and wider for the moto than the velo.

Applying front-wheel-only braking (because that's the thread, here) and Newton's 3rd, the force that tries to stop the wheel is opposed by a force trying to rotate the bike forward around that wheel
In both cases, the resistance to that force trying to flip you over is the weight of the rider and the bike.
​​​​​​On the velo, (call it a typical road bike ) the triangle of the CG and the wheelbase is taller and narrower, and would more easily reach it's tipping point with less rotation than the moto. Now, since the rider is the majority of the mass in the system, if they move back an behind the saddle, they can affect both the amount of resistance (longer lever, farther from the front axle) and by getting low, the amount of rotation before the CG approaches the tip over point. Conversely, if you're already leaning over the bars, or slump forward under braking, you'll make it easier for the back wheel to come up.

To the Moto; while the CG is generally a lot more forward, it's also lower and the wheelbase triangle is longer at the base, so the bike would have to rotate a lot farther to get to the tip over point. Given the rotation force equalized for the different masses of moto or velo, you would have more time to react and release the brakes before you go over. Because the moto is the majority of the mass, the rider can't affect the CG triangle as much. Plus the shape of moto saddles generally is designed to keep the rider from sliding back under acceleration, so getting back on the saddle also means standing up, so it may not be effective, depending on the specific bike.

TLDR: Velo is more likely to flip over front wheel under braking, but rider can do more to counter it by hanging off the back.
Moto more likely to lift rear wheel but not go over, rider weight shift not as significant factor


* I'm writing this in bits between tasks at work, so I hope it makes sense

tomato coupe

My statement was that many people ignore the differences between rider-to-bike weight ratios for bikes and motorcycles when discussing bike handling, to which you replied "yes and no". What's the 'no' about people ignoring the differences?

Claude.fr

On a moto, the rider can affect the rear triangle significantly, just like on bicycle you move your hips backwards.


You are, of course, right, there are significant differences vélo vs moto i.e. mass, CG, suspension makes a huge difference but the good body position, which few cyclists adopt, when braking hard is very similar.

PaulH

When I'm riding on ice or snow, I never touch my front brake. This has worked well for me in 60 years of winter cycling. In contrast, weight transfer allows the front brake to do almost all of the work in summer conditions.

icemilkcoffee 

If you are riding in a straight line on level ground, this is correct. If you are leaned over in the middle of a turn and you grab a handful of front brake you will slide the front.
I know some people don't want to hear it, but this is yet another lesson from motorcycling- the traction budget- turning and braking both use up some of this budget. So if you are braking hard, don't be turning. If you are turning hard, don't touch the brakes.
Motorcycles are different from bicycles of course. But in my experience, the faster you go on your bicycle, the more motorcycle-like it becomes.

wolfchild

I wasn't talking about track specific bikes ridden on track...I am talking about " urban fixies" and fixie conversions which majority of them come with both front and rear brakes. But some people remove the rear brake for no other reason then make to a statement....There is not one good, legitimate or practical reason for removing a perfectly functional rear brake and riding only with one front brake especially on a bike which isn't a fixed gear...Bonus points for stupidity to all those who ride completely brakeless in traffic.

wolfchild

In that scenario two brakes will stop you more effectively than just one brake.

wolfchild

When i ride on ice I would much rather have my rear wheel skid than my front wheel, way easier to recover.... Even when I ride with studded winter tires I am extremely careful about using the front brake and majority of the braking is done with the rear wheel.

redshift1

I also ride a motorcycle ( many years, many miles ) and have done a few track days, and off-road training as well. The idea behind what is often recommended in books, with applying this brake then, and then do this later on, in an emergency stop, is...................rubbish.

You will resort instantly to what you have practiced without any spare mental capacity to "think things through" in the heat of an emergency and supposedly be doing this and then that.

If you don't get on that front brake fast ( progressively to load the tyre and then much harder, but fast ), you won't be stopping in time....

If bicycles can endo, that means 100 % weight transfer. The hardest stop will occur at 100 % weight transfer, which means front brake use only.

Yes, I am talking emergency stops on dry roads, good tyres. Not riding on ice, oil on the surface, braking in turns, doing wheelies, etc.

Almost certainly because of motorcycling, I feel extremely confident when hard on the front brake and going over the handlebars is not remotely an issue for me. That is almost certainly what happens to an inexperienced rider who panics. Someone who doesn't know how to modulate the brake lever, feel what the tyre is doing, shift body mass backward / low, brace against handlebars, etc. And actually, this also applies to wet, sandy, etc. roads. People who grab a handful of front brake and go down with a wheel lock are inexperienced brakers who can't read the road.

Motorcycle racers ( road ) do not use their rear brakes to slow down - maybe to set the bike up here and there, tweak the suspension height at a particular point, etc., but not to aid in slowing down. That's because of weight transfer. Motorcycles (road bikes) will usually be set-up to offer different braking leverages front to back, to help dissuade rear wheel lock-up, but bicycles seem set-up not to do that ( conventional rim brakes ) at all.

Just two weeks ago, I had a car pull out in front of me when I was travelling downhill at some pace, so absolutely an emergency situation. Front brake only.

I have seen many times the ease with which a rear tyre locks in a hard stop ( weight transfer ) and since there is minimal rear tyre traction as the rear wheel unloads ( increasing to none as the rear wheel completely unloads ), I don't see the point of rear brake use, under these circumstances.

To those who ( like me ) have done genuine emergency stops on a road bicycle, surely you are not saying you apply both brakes hard, and then in the midst of stopping hard, you progressively release the rear brake lever while increasing the front to allow for the changing weight transfer, all the while with no wheel lock-ups ???

To those who have suggested some other uses of rear brakes ( e.g. back-up system in case of front brake failure ), thanks I take those on board. I can also see using the rear brake as well under gentle brake conditions to share the wear around rims and pads, etc.

But for emergency braking, I will be using front brake only and betting I outstop many "rear brake also" brakers .

p.s. I just thought to add this : I am not advocating for people to do what I do. I do not want you to hurt yourself. Please do what you feel is best for you.

wolfchild

Whatever man, you're free to imagine whatever you want about me...I stand by what i said, two brakes are better than one and there is no legitimate reason for riding with just one brake.

Eric F 

In an emergency stop, using both brakes means that the rear brake is contributing to deceleration. If it starts skidding, the friction of the rear tire dragging across the pavement is also contributing to deceleration. I'm not a fan of burning through expensive road ties by skidding them, but an emergency stop is just that - an emergency. Stop in whatever way is fastest, which includes using both brakes.

tomato coupe

I've definitely done emergency stops with both brakes but, as you stated, you have to get off that rear brake as soon as the rear wheel starts to let go. And it takes very little time for that to happen.

Rolla

And you're free to prove my point over and over again, as you no doubt will.

The hallmark of your immaturity/insecurity is thinking that you get to decide the legitimacy of others' reasons.

BillyD

Let’s tone down the hostilities in here, please.

rsbob 

Road biking: usually 60% front and 40% rear. (guesstimate)
MTB: 40% front and 60% rear or more if sliding the rear.

Road: always brake/scrub off speed before the turn and set up line through the curve, and accelerate out at the apex.
MTB: Always depends on terrain and conditions