Question about dragging brakes?

L

le coq géant

New member
I have a 08 1098 and for those that do not read in the 1098 section I had a crash last week. I was riding down the road and I felt the front end diving down as if I was grabbing the brake lever and pulsing the brakes but I was not touching the lever.

My question is what would happen if the front brakes were dragging a bit?

I would expect that they would get hot, smell and become kinda useless like on a car when riding the brakes down a hill.

I think what happend in my accident is the front brakes were grabbing and then got to a point that they locked up. This all happend in the matter of about 3 seconds driving at 35-45 straight not increasing or decreasing my speed.
 
3 seconds isn't too long and shouldn't overheat the brake system. You should have noticed an inordinate amount of throttle to maintain speed if they were dragging.

Theories:

Brakes were continually riding rotor, rotor warped and locked up. (unlikely, but plausible)

Foreign object in caliper. (By your description, you may have picked up a rock (or some road "crap") and it jammed into your caliper, binding the disc. Then, when it had eroded after a few seconds, it wedged itself in between the pad and rotor and locked up.)

HORNETDRIVER
 
I drove the bike about 2 miles and all seemed just fine. Then imagine driving and someone grabbing the front brake about 80% of max then releasing it to about 60%. So much like a pulsing feeling. There were a few firm pulses at which point I recall trying to add throttle because I had no idea what was wrong (out of gas, or what...).

Then I recall wanting to move over to the right to get off the road and then is when it washed out from under me. There are distinct skid marks on the front tire that show a lock up in my opinion.

The bike goes into the dealer tomorrow and then I am sure it will be a week or two before they know anything.
 
Hi Jketron.
I have a KTM dirt bike that has had occasional problems with the front caliper dragging and heating up to the point that it lock on causing a crash.

I have yet to get to the bottom of why it does this. It is a floating caliper, and it appears to cock and bind on the pins. On a dirt bike you really don't notice any difference in the amount of throttle it takes to kepp going or accellerate. But the steering feels really loose like you are riding in dirt and the next thing you know you have a mouth full of dirt.

I have also caused the brakes to drag on my Pantah once by doing up the fork clamping pinch bolt on the front axle B4 I tightened the axle nut. This caused the fork legs to be pulled together slightly and load up the brake pad in the caliper.

A quick ride around the block and it didn't feel right. Disc was VERY hot.
Didn't crash though.

Did you have your front wheel out recently.

hope this helps.

AB.
 
Have you changed the levers? Sometimes aftermarket parts will not let the master cylinder fully retract. This will allow some pressure retention and therefore the pads will be energized by pad and fluid expansion. As the pads heat up they expand and create more clamping pressure.

Master cylinders have two internal ports in them. One admits fluid from the reservoir. The other is a tiny pressure bleed hole which will be uncovered by the piston when the cylinder is normally fully retracted. If this is covered by the piston being slightly pushed in, the system is now technically energized and you'll get the pressure rise and braking effort scenario.

Another thing to check, (I'm not familiar with the 1098) is that on some levers there is an adjustment bolt that does the pushing on the cylinder piston. Adjusting this incorrectly will also not let the piston fully retract.

Check these things first ! Especially if you have aftermarket levers installed. Front brake, rear brake, clutch, and your car, a master need to be allowed to fully retract. There should be some freeplay before the lever hits the master piston.
 
if the brakes were slightly dragging shouldn't they have just gotten "soft" like the when you road race and use them too much..they get soft on you and not work as well?

The same theory of when a truck rides the brakes down a hill they become useless because they over heated.

If they did expand...they did it without any warning or early warning. The bike felt and drove fine then like magic. PULSE..PULSE..Lock up!
 
If the calipers are being energized by hydraulic pressure they will logically create stopping force.
On the bike it is easy to feel the effects of unintended braking. As a result we come to a stop. Hopefully under control. Going down a long grade hill we rarely need brakes as the engine will hold it. Big trucks have engine braking but often need the wheel brakes to hold speed.

Yes, if you were on any bike and ride the brakes eventually they would heat up to a point of fade. But on a Duc this takes quite a bit of heavy brake effort to really heat them up anywhere near a fade inducing event. For example you can run the bike up to 150, do a max effort stop, back up to 150 and do it again. They won't fade.

As the components on a bike are small as compared to a car they cool down very fast upon stopping. Look at the rotor thickness of a bike. ~5mm Look at the thickness of a car rotor. ~25mm. There is a lot of mass to cool down on car/truck parts compared to a bike.

I'm not saying that the blocked master holding system pressure is 100% your problem. But does the lever let the master fully return? Stock levers? Aftermarket? Adjusted correctly? I've seen this wrong fit up scenario before on numerous bikes.

If you feel this happening again, I'd not ride it and cart it on a trailer rather than risking a crash.
 
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