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]

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 ....

 

[lankydoug]

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 ....

phosgene gas is nerve gas and is created when R-12 refrigerant is exposed to an open flame. Long ago it was used a propellant for things like brake clean but not any more. Mustard gas is something completely different. You are right in avoiding any fumes from burning solvents since there is no telling what the resulting mix is... I dang sure ain't fresh air.

 

[Rick]

Rear brake are as tough as nails....at least the Brembo units. I am still using that rotor...OEM.....baby!! You must have an other problem some where!

 

[HuskyDude]

phosgene gas is nerve gas and is created when R-12 refrigerant is exposed to an open flame. Long ago it was used a propellant for things like brake clean but not any more. Mustard gas is something completely different. You are right in avoiding any fumes from burning solvents since there is no telling what the resulting mix is... I dang sure ain't fresh air.

Maybe that's why I did so shitty that day...

Back in the day before R-12 was banned I remember freezing the water in a Sprinkler pipe (fire suppression) with it to extend the pipe without shutting down and draining the whole system. Today we just use Liquid Co2. A lot more environmentally friendly. I know some guy that have used Propane.

Oh sorry for the jack...

 

[Cruiser]

Change your cup seal. It's most likely leaking past. It's easy to do,, just have patience when you change it and be ready for parts/spring clips to fly. I just had to do that on my exc. the parts most likely are the same. If you find they are pm me.. I had to buy a bag of ten. I'd be happy to send you one.

 

[GMP]

The KTM Brembo rear masters are notorious for failures. The Nissins are not. Its an easy test, just lean on the pedal and see if it maintains pressure/position.

 

[Neil E.]

Phosgene gas is also created during tig welding if open solvents are present. Lacquer thinner is commonly used for degreasing parts prior to welding. Make sure it has evaporated from the parts and make sure your cleaning pan is completely cleaned out or covered or put a long ways away.

 

[bondo]

Wow! Thanks for all the replies and suggestions.

Okay, let's go through the lot.

Are you running the stock pedal? Actually, no. The stocker was all wallowed out at the pivot point for the MC plunger, so there was always slop in the pedal.
I replaced with a YZ pedal. It seems to be identical in terms of the shape, length and fulcrum between the pivot point and plunger attachment point. Plus, it has a larger tread for one's boot (and it was about 1/2 the price of an OEM replacement). Also, the problem existed with the stock pedal.

Have you carefully inspected the surface of the rotor? Absolutely. I actually have two wheels I use alternately. The stocker has a trials tire mounted and has very few hours. I also have another complete wheel which mounts a Galfer solid rotor and a knobby. Both rotors are flat with no perceptible wear.
Brake performance is the same using either wheel/rotor combo.

When you say "no leaks at the master cylinder," do you mean no external leaks? No discernible leakage. The system does not lose fluid and no sign of dirt collecting anywhere (as would happen if there were a coating of hydraulic fluid weeping from somewhere),

Make sure the the brake cylinder plunger is also adjusted correctly.
Will check this. Does the service manual describe the procedure. The owner's manual doesn't seem to even refer to the procedure.

What shape are your pins that hold your pads are they grooved?
There is a little wear in the pin, but it's minimal. The rear caliper is routinely cleaned very thoroughly and the pin is polished with emery paper whenever the pads are removed.

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.
The spring and clip that help keep the pads in position and keep them from rattling appear to be in perfect condition.

Change your cup seal. It's most likely leaking past. Are we talking about the
cup seal on the MC? I have considered rebuilding the MC, and will likely do so. However, the system seems to maintain pressure and I don't get any pedal movement if I maintain pressure on the pedal for a long period of time.

I do plan on trying some grippier brake pads. I believe the rear pads on my '08 are the same as for pre-'08 Hondas, correct? Any suggestions on a really grippy brand / compound?

 

[GMP]

Are your caliper guide pins in good shape, lubed, and does the caliper float properly? There isn't much left! I run organic pads with solid rotors, very good in all conditions.

 

[pscook]

I have always had great luck with EBC pads. DO NOT get HH pads, they glaze over very quickly if not used properly. They are intended for high temperature applications where you can properly heat the rotors and pads before using them in anger. Think road race/Supermoto. Get the regular EBC pads, they are inexpensive and you can toss them if they don't work.

It sounds to me like you have either a) glazed pads, b) glazed rotor(s), or c) both. Get some garnet sand paper, make sure that it is garnet and not aluminum oxide. AL paper will leave a residue on the rotor that contaminates the pads and interferes with the molecular properties of braking friction. Scrub your rotors with the garnet paper until it is completely dull. Doesn't matter if you swirl it, straight lines, angles, whatever, doesn't matter. You just want to get all of the old pad material off the rotor. Install new pads and bed them in according to the instructions on the pads. That should be it. I use a vibrating sander and sand away. Stainless is very, very tough, you will not warp or otherwise damage your rotor (unless you set out to, but that's another story).

I have been dealing with glazed pads for years during road racing and street riding. It's a matter of removing contaminates from the rotor before you use new pads, especially if you switch brands of pads.

Another option to garnet paper is the rotor hone. never used one, always heard great reviews, but I still have some 60 grit garnet paper in the shop. I am "fiduciarily efficient" in all matters. My wife calls me "cheap." I can live with that.

 

[Cruiser]

The cup seal I was talking about is in the mc. They are notorious for leakbuy and when you get them from Ktm they come in a multipack. They should be the same as the gg brembo. If you want on pm me your address and I'll throw a new cup seal in the mail for you. You can have it in like 2-3 days. Like I said,, I had to buy 10.. Used one,, and have a few extra.