Brake Performance


11 replies to this topic
  • BBrown626

Posted January 07, 2008 - 08:05 AM

#1

I have not been able to maintain good braking at the front of my '04 450. I wasn't aware how bad it was until one day I hopped on my son's 2003 250F. The 250 stops much better. I have replaced the fluid, bled the brakes, new pads, etc. At one point I replaced the rotor and the brake worked much better for a while. Performance fell off though and it is back to poor. I tried brake cleaner, but that didn't help.

I am running std size, stock rotors. There are no fluid leaks and it has been bled.

I suspect the brakes are just weak on the earlier 450's and that is causing the rotor to glaze (?). I see that they put the 250's brakes on the 450 for 2008.

Any suggestions to improve the braking on an '04, short of buying a new rotor each month?

Anyone had this problem but fixed it by using a different rotor, oversized rotor or replacing the caliper with one from a 250?

thank you,

Brent

  • stroker101

Posted January 07, 2008 - 08:59 AM

#2

the front brake on my 08' YZ450F seems to be dragging. at first i thought it might be wheel bearings. after releiving the slight clamping force, i rotated the tire and it spins freely. then i took the tire off an looked at the bearings themselves just to be sure. tried bleeding the caliper several times but still drags. when pushing the bike, it feels really heavy. rotor is fine.
not sure if replacing with the 08' 250F system is the answer(?)

  • PatrickM

Posted January 07, 2008 - 09:06 AM

#3

I have a 1999 yz400f and the braking was terrible. I found that the brake line was old. I replaced the brake line and installed new pads and that fixed the problem entirely.

As a side note...... after some research, the brake line is same part number for all yz400fs, yz426fs, and yz450s (1999-2004).

The brake line is about 95 dollars and well worth the cost.


Patrick M.

  • 642MX

Posted January 07, 2008 - 09:29 AM

#4

Get a mastercylinder rebuild kit. The o-rings get worn and the pressure drops. The rebuild kits are cheap too.

My wifes mastercylinder went out, so I thought I'd rebuild both (even though mine was working) and my braking performance got a lot better. :banghead:

  • BBrown626

Posted January 07, 2008 - 10:00 AM

#5

Get a mastercylinder rebuild kit. The o-rings get worn and the pressure drops. The rebuild kits are cheap too.

My wifes mastercylinder went out, so I thought I'd rebuild both (even though mine was working) and my braking performance got a lot better. :banghead:



I'll give this a shot. It should be pretty easy and cheap.

If that isn't it, maybe a braided steel brake line?

Thank you.

  • 642MX

Posted January 07, 2008 - 10:05 AM

#6

I'll give this a shot. It should be pretty easy and cheap.

If that isn't it, maybe a braided steel brake line?

Thank you.


The steel braided line won't swell like the plastic could, but I think you'd have to be a really good (A level) rider to feel any difference.

I'm betting the rebuild kit will fix your issue. :banghead:

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  • grayracer513

Posted January 07, 2008 - 10:52 AM

#7

Let me ask this, since no one has: What specifically is wrong with the braking? Do they; 1) feel firm, but require excessive effort to produce the desired force, or 2) feel mushy?

  • BBrown626

Posted January 07, 2008 - 11:03 AM

#8

Let me ask this, since no one has: What specifically is wrong with the braking? Do they; 1) feel firm, but require excessive effort to produce the desired force, or 2) feel mushy?


Nr 1: They feel firm, but lack stopping power unless I am squeezing hard. My sons' '07 and '03 250F's grab much better with less effort.

  • grayracer513

Posted January 07, 2008 - 11:06 AM

#9

That, then, sounds like a pad friction issue. The pads may have been contaminated with oils or other fluid that have reduced their "bite". Try a new set.

  • Wes Woodin

Posted January 08, 2008 - 12:02 PM

#10

That, then, sounds like a pad friction issue. The pads may have been contaminated with oils or other fluid that have reduced their "bite". Try a new set.

Makes sense.

  • KJ790

Posted January 08, 2008 - 03:18 PM

#11

I had this issue earlier this season. First I tried brake cleaner, then changing the pads, but nothing helped. Since I had spare discs laying around I wasn't worried about ruining the disc so I tried some sand paper and then brake cleaner on the rotor. What a difference! Since then the front brake had been very strong. The rotor must have been glazed with something that the brake cleaner couldn't get off. Give it a try and see if it works.

  • tonypitcock79

Posted January 08, 2008 - 05:14 PM

#12

oversize rotor whith stainless braided line i get three finger power with one finger...and my hands dont get as tired so i can go 2 laps instead of 1





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