can't lock front brakes

[Old Colt]

Actually I look at it a bit different. On my 550ES I could always pull the lever to the grip. With the anti dive on the bike I could never get a firm lever.
Are you sure that all the pistons in the calipers are moving free?
Sounds like the bike might be fitted with EBC Green pads. They are about as far from a liner gripping pad as I have encountered.

The first thing I would do is make sure you do not have any stuck pistons up front. You pull the lever that hard you should either lock the front or more likely lift the rear wheel.

Keep in mind when doing this type or riding, be it training or testing, wear all the gear all the time. You are more likely to go down at lower speeds and you will hit hard if you do. I have done it.

 

[80GS1000]

I'm kind of looking for people to say this:

"I have a GS with a soft modern tire and stock braking system and I can lock the front."

If I should be able to lock it, then I'll look into different pads and then sanding the rotors. It's not clear to me whether or not 1985 brakes (with stainless lines) should lock modern rubber.

Your front tire will only lock when the available braking force exceeds the available front tire traction. Modern tires have an amazing amount of grip. So with modern rubber and an older brake system, you are unlikely to lock up the front wheel on dry/clean pavement. Even a modern sportbike with sticky radials and race-bred brakes will generally stoppie before skidding the front tire.

You don't want to lock up the brakes, ever. It's a loss of control at that point. The trick to good braking on any bike is to be smooth and steady as you apply the brakes - no stabbing at the lever. Instead, pull the brake lever like the trigger of a rifle - smooth and steady.

It takes a bit of practice to learn how to be smooth on the brakes at the grip limit in a panic situation so practice, practice, practice in an empty parking lot. Speed up to 10 MPH, stop as hard as you can with the front brake with 1-3 fingers, being smooth on the lever. If you feel the front tire slip or skid, immediately back off the lever a touch. Do this a few times, then depending on how big the parking lot is move onto 20, 30, 40, and 50 MPH. The idea is to find the braking limit so you instinctually know how hard you can pull on that lever before the front tire skids in an emergency situation.

 

[tkent02]

I have a few GSes with soft modern tires and stock braking systems and I could lock the fronts if I chose to.

I choose not to.

 

[argonsagas]

I have had the front tire on the GK show a trace of smoke on braking from high speed.....on a new Metzeler. No lock-up, but that is about as hard as I ever want to be braking.

Front wheel lock-ups are never desirable.

 

[p_s]

I looked at a few pictures and I think I have Vesrah organic pads. I'll try scuffing the pads and rotors tonight (and check that the pistons move properly), but it may be too wet here for a few days to test them. Mostly I'd like to get more braking with less force.

I'm not looking to do stoppies in traffic, just to learn the limits of braking. I've been riding for about 3 years and never really gone to a parking lot to practice braking, so I thought I should start.

 

[p_s]

It takes a bit of practice to learn how to be smooth on the brakes at the grip limit in a panic situation so practice, practice, practice in an empty parking lot. Speed up to 10 MPH, stop as hard as you can with the front brake with 1-3 fingers, being smooth on the lever. If you feel the front tire slip or skid, immediately back off the lever a touch. Do this a few times, then depending on how big the parking lot is move onto 20, 30, 40, and 50 MPH. The idea is to find the braking limit so you instinctually know how hard you can pull on that lever before the front tire skids in an emergency situation.

That's pretty much what I was doing. (Well, up to 30.) I just couldn't get the tire to howl or slip at any speed.

 

[Griffin]

I looked at a few pictures and I think I have Vesrah organic pads. I'll try scuffing the pads and rotors tonight (and check that the pistons move properly), but it may be too wet here for a few days to test them. Mostly I'd like to get more braking with less force.

I'm not looking to do stoppies in traffic, just to learn the limits of braking. I've been riding for about 3 years and never really gone to a parking lot to practice braking, so I thought I should start.

Those are what you have. That is my "standard" replacement pad on every old bike I refurbish.

Be very careful if you try sintered bronze pads. Those rotors are not as hard as rotors on modern bikes. Many older rotors have been badly scored by sintered bronze pads.

I don't think I've ever been able to lock up the front tire on my 700ES, even when new with OEM rubber and after an extremely thorough bleeding with an industrial vacuum pump. I've gotten it to the point where the front end was just about to let go and left a little rubber on the road, but never a full lockup, even from speeds well in excess of 80 mph.

If'n I were you and the braking symptoms bothered me, I'd try new pads (maybe a different brand organic like EBC or something) and see what happens.

 

[MelodicMetalGod]

Before worrying about lock up ability/potential, it would be a good idea to simply measure how quickly you CAN stop the bike. Simply set a "braking line" in your practice area, approach that line at the speed of your choice, begin braking at that line and then measure the distance from the line to determine braking distance.

If, after analyzing your results, you determine a need for greater braking force, THEN pursue appropriate mods.

Best of luck!

 

[Colin Green]

I'm kind of looking for people to say this:

"I have a GS with a soft modern tire and stock braking system and I can lock the front."

If I should be able to lock it, then I'll look into different pads and then sanding the rotors. It's not clear to me whether or not 1985 brakes (with stainless lines) should lock modern rubber.

Ahem!

Just to add to the mystery.. back in 80-81 I had a 78 GS1000 which when I tested, would lock (only briefly, as I'd ease lever pressure). It had the older (no hole) disks.

I now have a 85 (same as your 82 models) GS1100G and was also wondering about the lack of feedback. So I grabbed a quick handful (when in a straight line) at about 40-45 mph and the front let go for the fraction of a second it took to register and release the lever. That was a hard and fast test and I've only done it the once.

When riding I have had occasion [ http://www.thegsresources.com/_forum/showthread.php?t=134357&page=3 ] to have to increase braking fairly quickly and have heard (and dare I say 'felt') the front tyre moaning without locking up (but neither was the lever bottomed out). I think it would if I squeezed harder.

Have also heard her moaning at me a few times while braking in corners

All on stock disk/rotors, calipers and lines.

I have new braided lines to install soon as I get off my a@%e

Isn't that close enough?

 

[p_s]

Isn't that close enough?

You win.:-&
I don't really know what glazed pads look like, but they were kind of shiny, so I lightly sanded them and the rotors. The pistons all move when I squeeze the lever--no problems there. I won't be able to practice again for a little while, since the roads are an ice rink.

 

[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%20White%20Paper%20A1-The%20Physics%20of%20Braking%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.