can't lock front brakes

[Colin Green]

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...=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

[silverhorse47]

Thanks for the clarification. The shims would have to flex as they are transmitting the movement of the piston to the pad.
Since the brakes are working we know the pistons are moving.
The first question I would have is 'why aren't the pistons moving far enough to fully compress the pads against the disks'? The second would be 'is catastrophic failure around the corner'?
S.

[Shaughn]

Ya kno', If you described those symptoms to me on a car,
and I trusted your abilities as a tech, I'd suggest that the
rotors were glazed. Excessive/improper (i.e. draggging) pads
can overheat the rotor over time, and while may not be enough
to warp the rotor (that pulsation at speed) it may be enough
to harden rotor making it glaze, and not grab the pads correctly.

This is a subtle thing in appearance, but you'll definitely notice
it in performance. I'd take a rotary tool with a brown 3M roloc
and burnish the rotor, or if you have a brake lathe, skim cut it. If the
rotor chips out, well, you're out a rotor, but you confirmed the
rotor was glazed and better that it happened on the brake lathe
than on the road.

Just my .03

[tkent02]

Locking front brakes... not generally a good idea, as the resulting pavement contact hurts.
Fingers need to know to let off some pressure instantly. Stopping hard requires practice.
The ability to lock the brakes is very important. Newer bikes have better brakes to make it easier to stop hard, less pressure required from less fingers. If a few pounds of force from two fingers will result in maximum braking possible from your tires, it is much more controllable stop than trying to get the same braking by pulling as hard as you can with all four fingers, it becomes much easier to modulate the pressure, much more accurate. Any GS would have been able to lock the wheel when it was new, now tires have gotten a lot better so some of the early single disc bikes may not be able to lock the front wheel with the best tires available today.
The dual disc ones should be able to, but not nearly as easily as it would with with newer bigger brakes.
Brake pads can get old and hard, losing some of their grip. New pads are available now which greatly increase braking effort with less finger pressure.
Discs can be glazed, hoses can be partially blocked, lots of things need to be checked.

If your brakes are not right fix them.

[p_s]

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.

[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...=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.