Front brake


14 replies to this topic
  • yammx

Posted December 04, 2007 - 02:08 AM

#1

Hi Guys,

i am new as a XR650R rider and joind this forum today.
Now i like to start with a first question.
Last time i played a bit like supermoto on a hughe parking area and after
5min. of hard braking to the turns, i lost the complete pressure of the front brake.
Yes, the brake disc, the pads and the caliper where very hot, but is this
a reason to loose the complete braking power?
After 20min. of cooling down the pressure came back and i was able to ride home.
Ist this a problem of unproper bleeding (air in the system) or is the front brake simply to weak for aggressiv road riding.
Whats your experience?

Thanks in advance!

  • sploogemonkey

Posted December 04, 2007 - 04:44 AM

#2

Welcome to the board yammx.

I'm not exactly qualified to respond from experince as I do not own a 650R, but I've been riding for many years and have logged countless miles of agressive street miles in the canyons of SoCal.

I've experienced brake fade before, but never a total loss of braking ability.

You might want to install a steel brake line (I run Galfer) and flush your brake fluid and run some quality DOT 4 grade fluid (I run Motul). Properly bleed the system and inspect all the connections for potential leaks. Strap your bike down and compress the front suspension, now inspect the front brake cable and check for binding or kinking (do this even if you run the stock brake line).

If you ride hard enough to over heat your braking system in 5 minutes, you should be doing these mods anyway.

I'm sure that a 650R owner will be along to offer some more insight before too long.

Good luck and hope you get it sorted.

  • Blacksamwell

Posted December 04, 2007 - 05:08 AM

#3

Wecome!

With the stock caliper/disc settup you're probably going to see your brakes heat up a great deal when you start chucking your sumo pig hard into the corners. The caliper body gets overwhelmed with the heat that you are generating. That heat then finds its way to the brake fluid and will cause problems.

Most brake fluids are hydroscopic, meaning they absorb water very effectively. This will happen right through the rubber hoses over time. When the water heats up it boils and you get water vapor bubbles in your brake system. Bubbles make a very poor brake fluid medium. That would explain your total loss of braking until the system cools down. :busted:

The ultimate fix will likely be an upgraded caliper and disc. The larger caliper will manage the heat and keep it out of your fluid, not to mention give you better bite. In the meantime make certain you flush your brake system with fluid from a brand new unopened container of brake fluid to get rid of any water that's been absorbed into the old stuff.

Check out the Supermoto forums for all the details. :thumbsup:

  • HawkGT

Posted December 04, 2007 - 09:11 AM

#4

The front brake is fine for off-road but it can not get the job done for aggressive braking on pavement. I went with an EBC oversized rotor. The price was reasonable (by brake upgrade standards) and the performance was enough of an improvement to satisfy my needs. I also installed a steel braided line. Can't actually recall if that made a difference or not. On other bikes I have sometimes found that a brand new OEM rubber line works 99% as well as a steel line. It's only when that rubber line starts getting a little old that a braded line can make a really big difference.

FWIW, I also found my fork brace really helped settle down the front end under hard braking on pavement. It felt pretty "squishy" and unpredictable before and the brace helped on my bike. Dunno--maybe it's cause of my knobbies or something. Just felt a lot more planted with the brace.

  • yammx

Posted December 04, 2007 - 10:53 PM

#5

Thanks Guys,

for your informations. I guess it makes sence, to do first a
proper bleeding with DOT4 brakefluid.
After that I will try it again and let you know.
But I am still a bit disappointed that Honda is equipping a
160kph fast bike with a that much worse brake :thumbsup:

  • BWB63

Posted December 05, 2007 - 03:10 PM

#6

The stock brake line is kavilar reinforced and does expand more then it should. I went with Galfer S/S lines front and back and EBC 280mm front rotor on both of my setups but, for sumo BRP I would use the 320mm rotors. New DOT4 and vacuum bleeding helps alot.

  • yammx

Posted January 06, 2008 - 03:36 AM

#7

Wecome!

With the stock caliper/disc settup you're probably going to see your brakes heat up a great deal when you start chucking your sumo pig hard into the corners. The caliper body gets overwhelmed with the heat that you are generating. That heat then finds its way to the brake fluid and will cause problems.

Most brake fluids are hydroscopic, meaning they absorb water very effectively. This will happen right through the rubber hoses over time. When the water heats up it boils and you get water vapor bubbles in your brake system. Bubbles make a very poor brake fluid medium. That would explain your total loss of braking until the system cools down. :busted:

The ultimate fix will likely be an upgraded caliper and disc. The larger caliper will manage the heat and keep it out of your fluid, not to mention give you better bite. In the meantime make certain you flush your brake system with fluid from a brand new unopened container of brake fluid to get rid of any water that's been absorbed into the old stuff.

Check out the Supermoto forums for all the details. :banghead:


I tryed now the bleeding 3 times but it is still the same.
I believe the only solution is an upgrade to 320mm disc.

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  • creeky

Posted January 06, 2008 - 08:29 AM

#8

The heat generated from the constant heavy braking is boiling the brake fluid. When this happens, as you already know, no brake. Brake fluid is hygroscopic and will absorb a small amount of water over time, lowering the boiling point significantly, a complete fluid flush will most likely help. If you can get some Castrol SRF racing brake fluid which has a boiling point of 590 degrees, this will help. A larger rotor and kevlar brake pads will also improve brake performance.

  • Juxxtin

Posted January 06, 2008 - 08:33 AM

#9

320mm :banghead:

  • cleonard

Posted January 06, 2008 - 09:43 AM

#10

You really need to go with the larger rotor. The larger rotor helps dissipate the heat.

Having good fresh brake fluid will help some. However, the high heat will burn up your pads in no time. Your best bet is some DOT 5.1 fluid. It has the best heat resistance and is compatible with DOT 3 and 4. Uncontaminated DOT 3 is superior to DOT 4 from a heat perspective. When some water gets in there then DOT 4 is better than DOT 3.

For an instant "fix" pour some water on your caliper and brake rotor.

  • Maroast

Posted January 06, 2008 - 12:33 PM

#11

For an instant "fix" pour some water on your caliper and brake rotor.


I dont think that is a very good thing to do... I believe that if you pour cool water over a very hot rotor you may warp it. Furthermore, cool water on the very hot aluminum caliper could fracture the aluminum casting... just an idea.

  • Juxxtin

Posted January 06, 2008 - 07:28 PM

#12

320mm example, but be careful in the dirt, it's VERY effective, too effective for someone who isn't used to it.

http://lh5.google.co...00/DSC06308.JPG"

  • yammx

Posted January 06, 2008 - 09:26 PM

#13

320mm example, but be careful in the dirt, it's VERY effective, too effective for someone who isn't used to it.

http://lh5.google.co...00/DSC06308.JPG"



How much do I have to spent for this upgrade?

  • Juxxtin

Posted January 07, 2008 - 05:01 AM

#14

How much do I have to spent for this upgrade?


I've seen:
Used, between $100-150 USD.
New, between $150-220 USD.

And don't forget you'll need that caliper relocator bracket also.

  • Denn10

Posted January 07, 2008 - 11:17 AM

#15

I dont think that is a very good thing to do... I believe that if you pour cool water over a very hot rotor you may warp it. Furthermore, cool water on the very hot aluminum caliper could fracture the aluminum casting... just an idea.


i think he meant that as an excuse to have to get a new setup LOL not literally

Get the oversized anykind of rotor they are awesome upgrades.





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