Lost Rear Brakes coming down a Mountain

**94XT600~757** · #1 5 Sep 2009

Checked the search feature and found info on bleeding brakes but not my problem. Today rode off tarmac up a ski hill near town. Gained about 500m in altitude in very short time. Upon turning around and heading down mtn I was on the rear brake constantly. About half way down the brake pedal went all the way to the bottom and there was no pressure.

There is fluid in the brake reservoir. What else should I check? Right now it is raining and getting dark so I will have to deal with it tomorrow. But, I want to have a list of items to check. Anyone have this problem or have suggestions? Brakes worked fine before descending.

thanks
757

**bacardi23** · #2 5 Sep 2009

possibly, there is too much air in the brake hose... happened to me once because my brake pads were almost metal to metal....

Vando

**Gawain** · #3 5 Sep 2009

Sounds like water contamination, heat makes it boil then you have no brakes. New fluid may be a good idea.

**BlackDogZulu** · #4 5 Sep 2009

Quote:

Originally Posted by Gawain

Sounds like water contamination, heat makes it boil then you have no brakes. New fluid may be a good idea.

Definitely. Brake fluid/water - not compressible. Steam/water vapour - very compressible. When the water in the fluid boils - hey ho, no brakes. Brake fluid is hygroscopic, i.e. it absorbs water from the atmosphere, which is why manufacturers recommend it is changed every two years.

Change fluid, job done.

**Jens Eskildsen** · #5 5 Sep 2009

I've once lost both of my brake pads.

Mare sure they are there, and that they are not worn down.

Try the front brake too, next time. It's actually quite functional =)

**94XT600~757** · #6 6 Sep 2009

thanks I will try to change the fluid tomorrow. hopefully that will fix it.

I was using both brakes, very very steep. lucky only the back ones went out.

thanks again

**bacardi23** · #7 6 Sep 2009

Next time don't forget about engine braking...

Vando

**farqhuar** · #8 7 Sep 2009

It's happened to me before coming down the switchbacks form Mt Hotham to Harrietville.

My problem was that the rear pads were close to worn out and as a result they transmitted too much heat through the backing plates to the pistons which in turn boiled the fluid.

Check your pads, if they are thin then replace them and at the same time replace the brake fluid - once i't has boiled it is never the same again.

**desert dweller** · #9 7 Sep 2009

skillful riding will get you there.
oh and a bit of regular maintenance. every year or so for the fluid, like it says in the manual. pads when they're at their wear limit.
it's a motorbike, after all.

**RogerM** · #10 7 Sep 2009

Ever wondered why on long steep downhills there are signs "Trucks engage low gear". Constant application of the brakes causes the brakes to heat and ultimately fail - even disk brakes. Once cool the brakes return to their pre heated effectivenes - as long as the pads have not been burnt or the disk badly glazed or softened. Try going down a couple of gears and letting the engine do the braking for you - just as trucks do.

It has something to do with friction and heat, and as things get hotter their friction properties decline, no doubt a physicist could explain it thoroughly.