250-500cc Smoked my rear brake

Hi all,

I got my rear brake so hot today the pads were smoking. I was riding and had been going down a hill and was on them for a bit, off and on pretty quick. As I was riding it felt like I was loosing power to the point that I thought I had sucked in dirt and scored the cylinder. I looked down and the pads were literally smoking and I could barely turn the rear wheel by hand once I laid the bike over. I had to bleed the rear brake a bit to get it to release. I thought it had maybe too much fluid and thought it would be ok but it did it a couple more times. By the end of the day I guess I didn't have enough fluid left to have any rear brake.

OK, I've done a search and have read several threads so I know I'm not the only one with smoking rear brakes.

I see where several people have the shark fin from zipty racing on their bike and a larger rotor. The sharkfin I see says it's for a Pre 03 KTM/Husky. Mine is a '14 WR300. Also, What rotor are you guys using and will this for sure fix my issue?

Thanks in advance.

I would first off find out why they were dragging to the point the wheel would not move freely

I've had my rear brake totally lockup before and not roll. It was due to old fluid that had be boiled numerous, numerous times by me.

The fix was just change the fluid. One way to do this is to use the bleeder valve to pump new fluid through the system. Be-careful not to run the system too low of fluid and you will avoid getting air in the system. Just use whatever is on the master-cylinder cap for fluid.

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I got freggin' tired of buying pads so I had to learn to ride and keep my foot off the rear brake pedal. You don't really need to drag the brake so much and besides, braking slows you down

Ray is on the right track to replace the fluid as it gets hot it expands
A higher dot number raises the boiling point it probably gas dot4 now as drtdame says different brand more specific to our needs also helps

my mostly dry weather bullet proof set up is EBC red pads (carbon X) that dont transfer as much heat AmPro Racings Randy Hawkins' choice., Motul 660 race fluid, a zipty reservoir extender for more volume and on one of my bikes a Slavens end of hose caliper heat sink (I dont use this anymore but it was a must on my TXC450).

key items for rear brake bullet proofing
http://www.motul.com/system/product...ts/2636/rbf_660_factory_line_8472_(gb)_1_.pdf

http://ebcbrakes.com/product/carbon-x-or-tt-brakes/


note dont use xx pads up front they feel mushy

I had a finned heat disapator on my 92 360 it helped with high temp cooling

you can see the red pads XX carbon EBC, the Slavens heat sink, and the reservoir extender, the Motul RBF 660 is in there

Myself, I was just over braking lots and boiling my brakes to the point of no petal action, too often. It was just bad riding technique and over a period of the time of overheating, cooling, overheading, my brakes totally locked one day and I started to see the light. There is very little fluid in those system and depending on your riding, changing that fluid 2-3 times a yr does not cost alot. Just be careful not to introduce air to the system because that can be a problem by itself.

The different oil and parts will help, but sorry Charlie, its the rider unless you actually have a mechanical issue with that bike.

To my knowledge, I wasn't dragging the brakes unintentionally. I did use them quite a bit for a little span and that probably is what did it. I have some dot 4 fluid to put in it but I would still like to maybe look at putting a bigger vented rotor on it as I have never smoked brakes in 30 years of riding.

Does anyone have a link to a rotor that would fit?

30 yrs? I smoke'em every day if I'm not careful. I was to the point I was gonna take the brake petal off my bike to force myself to learn to ride and stop with all the over braking ... I constantly was killing off all my speed by over-braking. (Mostly on my 4t bike.. that sweet 2t bikes just roll when the throttle is shut)

I think the WR system holds less fluid than newer bikes and causes this boiling to happen ~more often than the newer brake system. If your fluid is the issue on a new bike, they just might be using fish oil for fluid.

you can hash this over all day and go bling crazy or use the oem stock rear rotor, make sure your brake is mechanically sound and adjusted properly, use Motul RBF 660 and EBC carbon X pads and see how it works. 99% it will be issue closed. PS related only to rear brake not heat but a shark fin is a good thing to have for off road

Brand new '14 WR300.... Flush your fluid, put some fresh pads in, but check the free play in your rear brake pedal and the cam for the height adjustment. Is your pedal really low?

I locked up the rear on my 13' 300 once at the start of last year. The oil in the res looked new but when I flushed the system all the oil in the brake line was black! I tend to drag rear brakes a bit but do a lot of braking with the front, I found the faster I get the more important my braking technique is and using both brakes at the same time! I run stock solid rotor and pads and flush the oil a couple times a season and no troubles with very little fade over a long race.

There is an argument out there that solid rotors dissipate heat better than slotted, more surface area...FYI. The only way I would change the rotor is if you go with an over sized rotor set up, just my 2 cents.

I find it difficult to accept even very heavy use of rear brake will cause everything to lock up without there being an underlying cause. The only time this has happened to me has been on a Sherco trials bike, and every time (3) it has been a sticking piston. I just remove the wheel and pads, spray a load of WD40 on the pistons and exercise them full in/ full out (careful, not too farl) several times and that has always freed them up.

As a long time Wr 250 and Wr 300 rider There is ONLY ONE WAY to fix the problem


Contact Zip Ty Racing or Jeff at Halls and order the Zip Ty Racing Shark Fin that has the caliper extender. Then you can use the same size rotor as ALL the other Husky use. Even the light weight 125 comes with a bigger rotor then a WR 250/300. The new rotor will also bolt direct to your hub. That will also end your rattling, small does not work stock rotor.
Motol hi temp fluid works best You do this and you will be just like all the rest of the Husky and you will not have the problem again. Since I have done this I have never had a rear brake problem again
The kit is cheap so it is a easy fix

I agree that purging the brake fluid should be done front and rear to keep things working the way they started. Now we need a little brake education here. Solid rotors are great for sloppy conditions and greatly extend brake pad life. Solid rotors can also hold more heat than a vented rotor but once they are hod they can not get rid of the heat so they like to boil brakes in hot conditions. Vented rotors will run a lot cooler. There really isn't a need to change to the larger rotor just the correct rotor for what you are doing. My brother had this problem on his WR 250 and the rotor switch was the solution. I even have a spare one if you are interested in it. It is also the solid mount type so no more rattling as well. Just a little more info KTM uses the same size rear rotor on all of their dirt bikes as the WR 250/300 so that configuration does work well.

I even tried the Cr vented rotor and Motol fluid did not really help much

I then went the Zip Ty shark fin and rotor like all the rest of the husky and it is all good

Is there an issue with your brake linkage or brake lever stop (eccentric adjuster under pedal)? Im a heavy rear brake steerer and during most races I hear all the KTMs around my squeek squeekin into every tight corner in the woods.
Motul high temp fluid and EBC Red pads as mentioned above. I feel there is plenty of braking power with the floating disc that comes standard on the WR but other riders like more brake power. If I was riding it supermoto Id definitely upgrade. The few times I boiled out my fluid on my KTM 250SX, I hade NO brake power. It didnt lock up, it didnt even slow me down.

Any KTM dirt model from say 00+ on?