Rear brake S***s!

[bondo]

The rear brake on my '08 DE300 is the worst. It requires lots of pedal pressure to get any stopping power, there's too much pedal travel and there's no way to lock the rear wheel. Up until recently, I've been on KTM's so this situation is doubly annoying.

A little background info: Fluid is fresh DOT 4. The system has been bled and back-bled several times - no air there (and never any debris in the fluid). No fluid leaks at the Master, at the caliper or at any of the attachment points for the hose. Rotor is smooth and clean, no grooves or pits. am using EBC sintered pads (have tried "roughing " the pads to remove any glaze).

The poor braking performance is consistent any time, under any conditions - wet or dry, hot or cold, whether at the beginning of a ride or after an hour or more of aggressive riding.

The wimpy rear brake is really a handicap and I need to get things working the way I like!

Who else has had this problem? And more important, what's the best place to start looking for a fix?

[Fred1956]

Are you running the stock pedal? I had same issue on my '06 BUT with a Mecca Systems brake pedal-turned out the Mecca pedal was so soft that it was flexxing and not getting full pressure (my theory). Problem went away with the stock pedal from my '04 so I'm shopping for a better rear brake pedal on the '06 again. Just a thought otherwise my brakes are great on both bikes

[Neil E.]

Have you carefully inspected the surface of the rotor? Is it absolutely flat? It is common for the center of the contact area to wear a few thou more than the edges. When you put new pads on they are only really pressing at the edges. Big time loss of braking force. Maybe it's time for a new rotor and/or a different pad compound?

[bchatt]

I'm running stock everything on my 07. I can easily lock the rear wheel, in fact I do more often than I would like. I don't believe there is a general problem, there is something amiss with your bike. Maybe try some different pads.

[blitz11]

When you say "no leaks at the master cylinder," do you mean no external leaks?

The M/C can leak internally, which if it occurs, won't generate any brake pressure (or diminished brake pressure).

Make sure the the brake cylinder plunger is also adjusted correctly. When we bought my daughter's KTM, all of a sudden she started to wear out her right side boot. Turns out the plunger was adjusted incorrectly, and the lever was bottoming before she had full stroke on the M/C.

It was a new bike and her first rear disc. I never rode the bike (I sprung it for a 100 pound girl), and she didn't know any differently. When I discovered her boot, i looked at the brake, and sure enough. bad adjustment.

fixed the brake, and no more boot wear. and with a rear brake, she's so far ahead, i never get to see her ride.

[HuskyDude]

I'd first try a new set of pads...If some how you accidentally got some chain lube or whatever on them even sanding them may not help.
While you have it a part inspected the surface of the rotor?

I had a problem with my back brake on my trials bike at a competition once (got chain lube on them) I ran up and down the road with the brake applied till smoken hot then hit the pads with some contact brake cleaner stuff...Big puff of white smoke a little sizzle...and all was good till I got home and put new pads in.

[ramcclure200]

What shape are your pins that hold your pads are they grooved? If so replace them with new

[GMP]

Fouled rotor/pads, internal leak, seized/binding caliper pins.

These are the same brakes used on many Japaneese MX bikes for years, there is no design flaw. Mine is more than strong enough with basic care.

[GasGas]

Aside from worn brake pad pins, I have also worn through the stainless clip in the front of the brake carrier and worn a groove in that as well. Watch those stainless clips and springs on your pads.

[skid jackson]

Originally Posted by HuskyDude

I ran up and down the road with the brake applied till smoken hot then hit the pads with some contact brake cleaner stuff...Big puff of white smoke a little sizzle...and all was good till I got home and put new pads in.

Your a lucky man ....
brake parts cleaner plus high temps equals phosgene
phosgene is also know as mustard gas, or something like that, the shiet they used during ww1 to kill and maime thousands of soldiers.

read an interesting article about a mechanic in bicycle shop who put the heat to something that had previously been sprayed with brake parts cleaner ... poof!! damn that stuff is nasty ... few days later they dude was cooked , not dead but on his way to a life on disability ....