can't lock front brakes

[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.

 

[tkent02]

How about just laying it on the side, isn't that what your supposed to do in a panic braking situation? * but in snow and mud at slow speeds, a locked tire will stop quicker than a rolling tire.

You must have different snow than us.
Anti skid rocks in snow on a car.
A locked wheel slides forever in snow.
Even farther than a Harley will slide on it's side.

 

[MelodicMetalGod]

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.

ONLY lay the bike down if you're riding a Harley. That way you can total it, collect the insurance and buy a GS.

Well, I must say that I was making the assumption that we were working with dry pavement, possibly wet pavement. Figured that if you're riding in mud or snow on a GS that using brakes probably isn't a big part of your plan anyway.

 

[Shaughn]

You must have different snow than us.
Anti skid rocks in snow on a car.
A locked wheel slides forever in snow.
Even farther than a Harley will slide on it's side.

You must have a different set of physics than the rest of the world.
Anti-Lock Brakes improve STEERING not braking. This confusion
leads to many accidents as people stand on their brakes and plow straight ahead not recognising that with the ABS pump running it takes longer to stop.

They function by pulsing the brakes so that the wheel remains in traction
with the road (versus a skid) which allows you to turn while panic stopping (that is, stopping hard enough to skid (WRT road surface) while holding the pedal down). If the tire is in a skid, the contact patch is not rolling, and the shape is pretty much the same whether the wheel is angled straight or maxed out, which is why on old cars, if you stood on the brake pedal, and then tried to steer, you'd skid straight ahead. ABS generally adds 30% to straight stopping distance vs ABS disabled, however it gives you the ability to steer to avoid collision.

ABS is activated when the ABS computer notices a difference in wheel or axle speeds, and interprets this as a skid if the difference is great enough. Modern Traction Control (TSC, RSC, ASC) systems also use these wheel sensors to adaptively pulse the brakes per the individual wheels to stabilize the vehicle. This works great in snow, my work '09 F150 will not let you kick the ass end out with the system enabled. Still not made to shorten braking distance, but again adds control and stability.

Also, passive TPMS (tire pressure monitoring system) used the wheel speed sensors to determine when a tire is low without requiring a sensor in the wheel. This is simply done by noting that a soft tire has a smaller effective diameter, and therefor will spin at a lower rpm than the other tires.

All this neatness is a child of ABS's requirement of wheel/axle speed sensors, but none are designed to stop in a shorter distance.

Cheers!

 

[Shaughn]

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 don't want to speculate on the handle shudder, but maybe that's from the pads starting to lose grip and stuttering across the rotor?

As far as modern tires not allowing lock up, let me try to simplify the physics another poster laid out before.

With a Bike coasting across the screen Left to Right ----->

Inertia is driving the bike right ---->
The tire's traction is trying to keep the tire stationary, which is like
a force pushing against the bottom of the tread to the left <-----
This force is what causes the tire to rotate, which is the force
the brakes are trying to stop.

The more force via traction going <------, the more force needed to
stop it. When you upgrage your tires, you are increasing the force against
the brakes, but not increasing the brake force. This makes the brake more effective, as the increased traction can now use all of the force the brakes apply but does not mean that you can necessarily OVERCOME the traction of the tire. (which leads to stoppies, whee) If you can skid your tires, then that is wasted brake force.

Savvy?

 

[Shaughn]

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.

I've never seen a modern car without some sort of proportioning valve, but this is not to say that there aren't aftermarket improvements out there to alter the front/rear balance. I'm also no porsche tech, so who knows. I suppose having overpowered front brakes and severly underpowered rears would have the same effect as a proportioning valve, but why would they do that?

On a bike, you have two brake system, so you the rider are the proportioning valve, adjusting front/rear balance, at least on our old bikes. I assume there could be modern bikes with only one brake pedal, like a car, but hell, I wouldn't want to ride one. But if such a beast existed, yes, it better damn well have a proportioning valve to aid against the rear locking up before the front.

Of note, ABS (afaik) was first used in trucks to prevent the rear axle from locking up (due to no load in trunk/bed/box/rack) before the fronts.

 

[GQROD]

My club was dedicated to the older porsches which were not as refined and needed better brake tuning, after modifying.

Modern cars of course have this valve.

 

[silverhorse47]

You may be right about the ABS. That would make sense, and their bikes are definitely different...dual sport...different animal. The warped rotor thing also would pulse the lever, but they describe it as a shudder.
S.