can't lock front brakes

[rphillips]

BE CAREFUL, If you've never been there, you won't beleive how fast you will be in trouble.

[82Shafty]

See that I have always loved the common sense of physics I will explain this in general terms.

And for those who like to educated themselves, feel free to read in depth.

http://www.centricparts.com/Centric%...%20Systems.pdf


You would have to look at potential vs. kinetic energy between your bike and the bike you are comparing it to.

One, if we used the same input what would be the (net) potential output of both bikes? What's lost along the way in movement, heat, multiplication at the master and again at the calipers.

Then you get to factor in:

Effective radius of the rotor does make a huge difference... Think about a torque arm, longer the arm, the more effective the same. He probably has bigger rotors.

Note: we are leaving out a ton of wasted energy here and pretending we have a perfect system, just factoring in the very, very basics.

Friction forces between your pad/rotor relationship and his pad/rotor relationship. Less loss to heat, higher frictional forces, then multiplied by the invisible torque arm..phew it all adds up very quickly.

Weight:

Transfer of each bike and energy in motion in regards to deceleration. SD

Fork rake:

Angles play a difference when transferring cycle weight.




Look, as you can see and read up on your own time, there are too many factors to evaluate when comparing a new bike verse an old bike.

As far as a master in concerned:

You would want to ensure you could create more force per given throw. A bigger piston requires less throw given the torque angle is the same on both masters. Or have a machinist build brackets to take on a different caliper, but don't forget that the greater volume of fluid that you're displacing in the calipers, you will most likely need a larger pistoned master to displace more fluid during a given throw/stroke.

I think the easiest thing for you is to run a newer pad designed to work with an older rotor. Do your homework, some pads require less heat to bring them up to their maximum coefficient, and as Griffin noted, sintered chews up old rotors.

I know how you are, you can't sleep until you feel your performance level is at least where it needs to be.

Measure out the distance, find stock stopping feet from 60-0 mph and do some test runs. Make sure you put some miles on new pads and deglazed rotors before you go and throw the anchor out.

Good luck and be safe.

[silverhorse47]

This thread is interesting, for sure. I am curious as to what people mean when they say 'modern rubber'. The way I am thinking about it, the softer and 'grippier' the tire rubber, the more feedback should be delivered to the brake lever. The harder and stiffer the tire rubber, the more liklihood there is of a sudden lock up.
I am not an expert, though I have run out of brakes, completely, due to line failure in a four wheeled vehicle.
However, I have talked to people who regularly ride modern bikes waaaay faster than I will ever ride, and they tell me that their brake levers 'shudder' when the tires are about to lock to the cylinders, and skid the tires. I interpret this to mean that the soft rubber of their tires is signalling them (by bending and releasing), through the brake fluid via the line and master cylinder, that they are bent to the max and need relief.
Are we talking here about lever feedback or are we talking about lock up? I call lock up when the front tire skids on the riding surface. I think this should be possible with any braking system. I think the feedback to the lever would be moderated by the tire type/softness/hardness/tread/temperature etc., as well as the braking surface.
But still, the lever, when pulled, should stop the wheel from turning.
Am I wrong?
S.

[tkent02]

This thread is interesting, for sure. I am curious as to what people mean when they say 'modern rubber'. The way I am thinking about it, the softer and 'grippier' the tire rubber, the more feedback should be delivered to the brake lever. The harder and stiffer the tire rubber, the more liklihood there is of a sudden lock up.
I am not an expert, though I have run out of brakes, completely, due to line failure in a four wheeled vehicle.
However, I have talked to people who regularly ride modern bikes waaaay faster than I will ever ride, and they tell me that their brake levers 'shudder' when the tires are about to lock to the cylinders, and skid the tires. I interpret this to mean that the soft rubber of their tires is signalling them (by bending and releasing), through the brake fluid via the line and master cylinder, that they are bent to the max and need relief.
Are we talking here about lever feedback or are we talking about lock up? I call lock up when the front tire skids on the riding surface. I think this should be possible with any braking system. I think the feedback to the lever would be moderated by the tire type/softness/hardness/tread/temperature etc., as well as the braking surface.
But still, the lever, when pulled, should stop the wheel from turning.
Am I wrong?
S.

You are wrong.
Older brake systems were designed for the tires of that day. Adequate then, but not now. Todays tires are a lot better, take a lot more braking force before they let go and skid. Early brakes don't have the capability. Switching to a good modern tire is the first upgrade and the most important one you can make to any old bike, to take advantage of this requires better brakes. The old brakes can't do it on most old bikes, even if they are working 100% as well as they ever did. Sometimes upgrading pads is enough, sometimes upgrading entire systems is required. I know my thirty year old bike will never stop as good as my newer bikes due to frame and wheel differences, but I'd like to be as close as possible to it.

Riding around like a little old lady hoping never to need a hard stop does not appeal to me.

[Dogma]

...
But still, the lever, when pulled, should stop the wheel from turning.
Am I wrong?
S.

This is my thinking too. Obviously, locking the wheels up is a bad thing. OK, maybe you can't lock them on dry pavement. What about wet? It may happen someday, and I would like to have practiced what to do with that. Yes, I know that I should immediately release pressure. I can't guarantee that's what I'll do unless I practice it though. So, I want to be able to lock them in order to practice.

When not locking, I want to get all the stopping power my tires can deliver. No stopping distance is "short enough". To get minimum stopping distance, I need to be able to lock them on dry pavement. Front brakes that can't lock are only safer if you never learn to use them fully.

So, for maximum safety, I want to be able to lock the front on dry pavement in order to minimize stopping distance, and to be able to train myself on handling a front wheel lock-up. Anything less is not as safe as I could be. I see no reason to tolerate that.

[Pete Logan]

Next time I might find a spare MC cap and plumb it to compressed air and pressure bleed the brakes.

The Gunson system that works this way specifies no more than 10 psi.

I had one, and it worked fine except didn't have an adapter for a US M/C. Maybe they do now.

I use a Phoenix reverse bleeder now, which works fine on bikes and cars.

[waterman]

How many miles do you have on your bike? I had a similar situation with the brakes on my brother's 1000g that I worked on. His brakes were horrible compared to any of my gs's. But at the same time, his bike has roughly 65,000 miles while none of mine have more than 20,000. I wonder if the brake rotor themselves are worn to a point where they no longer generate as much friction as before. It may have been different pads and I didn't fix them since it was his bike and he was used to them.

I also have a difference between my two 650g. One has great brakes; if it wasn't so cold and wet, I would go out and test whether I could lock them up. I bet that I can since I could make them chirp and howl with only a couple of fingers in the fall. The other 650g that I am fixing, the brakes just don't seem to generate nearly the same braking power. I can make it howl, but the lever is to the grip. I have recently purchased a set of Kawasaki binders and will upgrade to see how much better they can be.

My dual sport had better brakes years ago, but as of lately generally stink, high lever force, lotta fade. I mostly blame tires, have gone more dirt orientated. Even so, they will lock and slide on dry pavement if really overzealous with lever. These are sintered type and have tried several different pads hoping to get back some of the lost stopping power.

[p_s]

How many miles do you have on your bike?

Which part? I'd guess 25k on the rotors. The brake lines and seals and brake pistons and all are new as of May. It looks like this weekend will be fine to go to a parking lot and practice, so I'll see if anything has changed since scuffing the rotors and pads.

[argonsagas]

However, I have talked to people who regularly ride modern bikes waaaay faster than I will ever ride, and they tell me that their brake levers 'shudder' when the tires are about to lock to the cylinders, and skid the tires. I interpret this to mean that the soft rubber of their tires is signalling them (by bending and releasing), through the brake fluid via the line and master cylinder, that they are bent to the max and need relief.

S.

I can grab quit a bit of brake with the Bandit (braided lines), and it lifted the rear tire just a wee bit, once, but it never gave me a shuddering of the lever.

Maybe their bikes are different, or perhaps they have ABS?

What you are describing is not uncommon with ABS.

[Billy Ricks]

I can grab quit a bit of brake with the Bandit (braided lines), and it lifted the rear tire just a wee bit, once, but it never gave me a shuddering of the lever.

Maybe their bikes are different, or perhaps they have ABS?

What you are describing is what usually occurs with ABS.

Or warped rotors. On my bike the back end gets very light with enough front brake applied. I'd probably be doing a stoppie before the front locked up. That's with 4 pot calipers, GSXR master, PFM iron rotors, and a Dunlop radial on a 3.5" wheel up front.

[GQROD]

Don't know if there is one for bikes or if it's practical but you could always install a brake bias proportioning valve to fine tune the point at which you lock up.

I installed one on my porsche when i raced it at club events and it was a street car.

Good braking performance is definetly important. But you will never be truly prepared for when something happens and instinctively you lock your front brakes.

After years of riding perhaps you get better, but it can happen so fast honestly you will lock your front brakes and drop the bike before you realize what just happened.

I have the road rash to prove it.

Bring the brakes up to standard and more than anything protect yourself, good gear, and safety practices.

just my .02 cents.

[tkent02]

Don't know if there is one for bikes or if it's practical but you could always install a brake bias proportioning valve to fine tune the point at which you lock up.

To adjust bias between front and rear brakes?
Good idea on a car.

[MelodicMetalGod]

This is my thinking too. Obviously, locking the wheels up is a bad thing. OK, maybe you can't lock them on dry pavement. What about wet? It may happen someday, and I would like to have practiced what to do with that. Yes, I know that I should immediately release pressure. I can't guarantee that's what I'll do unless I practice it though. So, I want to be able to lock them in order to practice.

When not locking, I want to get all the stopping power my tires can deliver. No stopping distance is "short enough". To get minimum stopping distance, I need to be able to lock them on dry pavement. Front brakes that can't lock are only safer if you never learn to use them fully.

So, for maximum safety, I want to be able to lock the front on dry pavement in order to minimize stopping distance, and to be able to train myself on handling a front wheel lock-up. Anything less is not as safe as I could be. I see no reason to tolerate that.

Actually, I believe that locking up a tire actually INCREASES stopping distances. Shortest stopping distances are achieved by getting as close to lockup as possible without actually locking up.

Also, a front wheel lockup is a loss of control which is the last thing you want to lose.

[GQROD]

Preach on brother PREACH ON !!!

[waterman]

Actually, I believe that locking up a tire actually INCREASES stopping distances. Shortest stopping distances are achieved by getting as close to lockup as possible without actually locking up.

Also, a front wheel lockup is a loss of control which is the last thing you want to lose.

How about just laying it on the side, isn't that what your supposed to do in a panic braking situation? *

All kidding aside, you are correct in getting the wheel to almost lockup. Work great in almost all situations. My cage with antilocks is good the vast majority of the time, but in snow and mud at slow speeds, a locked tire will stop quicker than a rolling tire. Many times I have wanted to put a toggle switch on the dash to disable the antilocks as the bumper of the car in front of me gets larger and closer.