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SpaceRacer

Braking question

10 posts in this topic

I just recently put new pads on my 08 Yam YZ450 front brakes as well as bled and refilled the front brake fluid. I thought I did everything correctly and the bike does seem to stop adequately but I cannot lock up the front brake into a skid. And I have not had the bike long enough to compare what is "normal". Not that I want to lock up the front wheel under normal conditions but should I be able to?

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I just recently put new pads on my 08 Yam YZ450 front brakes as well as bled and refilled the front brake fluid. I thought I did everything correctly and the bike does seem to stop adequately but I cannot lock up the front brake into a skid. And I have not had the bike long enough to compare what is "normal". Not that I want to lock up the front wheel under normal conditions but should I be able to?

 

 

 

Depends on how firm you want the lever.  Do you have any more room on the adjusting screw at the lever?  If you're 100% certain ALL the air is bled out, and If you want it so it can lock up the wheel without the lever pulled all the way to the bar, then just open the bleed nipple on the caliper and apply slight positive pressure by injecting fluid with a syringe.  Do this with the MC lid in place.  Takes all of 3 seconds and will make a tremendous difference in firmness, and in how the brakes grab.  There are people who will advise against this, and others who claim it doesn't work, but it does.  I have had it where no amount of vacuum or reverse bleeding could get the brake to the firmness I want.  With the adjuster screw all the way in I would still have to pull the lever almost to the bar to essentially lock it up.  I like my brake a little more firm.  I like it to lock up at the point when using my index finger only, I am able pull the lever onto the knuckles of my other three fingers.  Doing as suggested above allows me to attain exactly that....

 

Also, be sure you haven't contaminated the pads with brake fluid.  Maybe give the pads and disc a shot of brake clean to be sure ;)

 

It may also just take a little while for the new pads to shape/conform to the old rotor.....so that there will be more surface area of the pads making contact with the surfaces of the rotor :thumbsup:

Edited by Fattonz
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You scuff the rotor and set the pads?

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No, I did not scuff rotor or bed pads. How is that done? Should I do this before messing with the brake fluid?

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No, I did not scuff rotor or bed pads. How is that done? Should I do this before messing with the brake fluid?

 

 

You should get into the habit of bleeding your brakes on a regular basis to keep 'em firm and to get comfortable with doing it as part of regular maintenance.  It's very easy and takes very little time.  I believe you can pick up a 60cc syringe for less than $5.  Lots of times after a little fall the brakes will go spongy and require bleeding (when inverted the air in the MC above the liquid is introduced into the line).  You might as well learn the skill...you will need it at some point :thumbsup:

 

Anyway, since you haven't cracked into the system it's likely just a matter of the pads conforming to the disc which may have small grooves worn in it.  If you drive a distance with the front brake slightly applied, the pads will quickly wear to the rotor and your brakes will dramatically improve....

Edited by Fattonz

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Fattonz, just so I am clear on your syringe technique, get a syringe (no needle), draw fresh brake fluid into it, open the bleed valve and push some fresh brake fluid into the bleed valve and then close??? Correct?

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Fattonz, just so I am clear on your syringe technique, get a syringe (no needle), draw fresh brake fluid into it, open the bleed valve and push some fresh brake fluid into the bleed valve and then close??? Correct?

Yes, that is correct no needle. Just a large syringe with a short piece of vinyl tubing attached that is the appropriate size to fit onto the bleed nipple. Extract fluid from it's container into the syringe. Be sure to turn it upside down and tap it to bring all the air to the top like a doctor would....you don't want to inject any air or you will be defeating the purpose. Do it with the MC lid off first and have someone observe the fluid in the reservoir. They will be observing for two reasons.....to watch for any air bubbles being liberated, and to notify you when to stop so you do not overflow the reservoir. You could buy a smaller second syringe and label it waste. Use it to extract the excess fluid from the reservoir. Repeat the cycle until the fluid color clears up indicating all the old fluid has been displaced with new. By now it is safe to assume the brakes are bled. You have just used the reverse bleed method.

Replace the lid on the MC reservoir and try the brake. If you still feel that you prefer a firmer brake, then proceed with the trick I suggested in my first post of injecting some fluid into the closed system under slightly positive pressure. You will be amazed at how much better your brake will perform ;)

 

Here's mine:

 

P4180458_zps1bc808d9.jpg

 

 

 

 

 

....and a look at old fluid vs new:

 

P4180457_zpsb39111f7.jpg

 

P4180465_zps8cea6eec.jpg

Edited by Fattonz

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Syringes, vacuum bleeders, etc., are frankly unnecessary.  Either brake system will gravity bleed quite nicely without any extra equipment.  There will usually be a bubble caught in the banjo fitting that can easily be bled away at the end of the process.

 

To the original question, generally, it's just about all that a YZ450 can do to lock the front wheel in decent traction.  In fact, it's usually fair to say that they won't quite do it.  That works fine for some, and not for others who like more aggressive brakes, and it's why upgrades like oversized rotors and alternative master cylinders have become popular.

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