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XR400 Brakes - freshen 'em up


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I rode a friends XR4 and realized my brakes just aren't stopping like they should. Everything is within tolerances, but probably glazed from many miles. Do machine shops resurface these rotors? How much of the assembly do you give them? Would some new semimet pads bite right in?

Thanks

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I've not heard of anybody resurfacing dirt bike rotors like you would a car rotor. I don't think they are thick enough to work with.

Pads are fairly inexpensive, worth putting a new set in and then seat them with the rotor properly.

Also, brake fluid is hygroscopic which means that it absorbs water, even in a sealed system so changing fluid if it hasn't been done in the last few years is a good idea too.

You can always go with a SS brake line too.

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I agree with all of that.

You need to check the thickness of your rotors. I think they are stamped with a 3mm minimum thickness spec. When mine got near that limit, it's like my brakes disappeared, with everything else being in good shape. Replaced the rotor with new and got my brakes back.

I've not heard of anybody resurfacing dirt bike rotors like you would a car rotor. I don't think they are thick enough to work with.

Pads are fairly inexpensive, worth putting a new set in and then seat them with the rotor properly.

Also, brake fluid is hygroscopic which means that it absorbs water, even in a sealed system so changing fluid if it hasn't been done in the last few years is a good idea too.

You can always go with a SS brake line too.

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If you have checked all the suggestions above and everything seems in good order but the brakes are still not working like they should, maybe it is the glazed surfaces of the rotors/pads... try scuffing them up with some sandpaper. Anything between 200-800 grit should work fine. Don't go crazy, just sand enough so that the rotor and the pad have an even layer of scuffed surface. I have done this before with significant and lasting results.

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If you change all the brake fluid, you will notice a difference. I was amazed and it had barely been a year since the last time I had changed it.

Bingo!

When I recently did my fork upgrade, I put brakes from a CRF450R on the XR4. But the brakes on the 450R were nothing to scream about. However, once I bled out the brake fluid and replaced it with some fresh DOT4... and used my "Mighty Vac" to bleed the brakes, it's amazing the difference. So much so, I did my other bikes as well with good results.

Also, using the upgraded pads (CM46) from BRAKING help (Careful, they are tough on rotors. Or use the standard CM44)... or, stock (OEM) pads. I stay clear of anything other.

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Bingo!

When I recently did my fork upgrade, I put brakes from a CRF450R on the XR4. But the brakes on the 450R were nothing to scream about. However, once I bled out the brake fluid and replaced it with some fresh DOT4... and used my "Mighty Vac" to bleed the brakes, it's amazing the difference. So much so, I did my other bikes as well with good results.

Also, using the upgraded pads (CM46) from BRAKING help (Careful, they are tough on rotors. Or use the standard CM44)... or, stock (OEM) pads. I stay clear of anything other.

I've NEVER seen this discussed: are the CR(F) calipers any better than XR's??

Are they "high performance" in any relevant way? Most folks assume they are, but i"ve never seen any claim that they are better/stronger/ more pistons, whatever.

????????

Anyone?

Bueller??? 👍

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I've NEVER seen this discussed: are the CR(F) calipers any better than XR's??

Are they "high performance" in any relevant way? Most folks assume they are, but i"ve never seen any claim that they are better/stronger/ more pistons, whatever.

????????

Anyone?

Bueller??? 👍

I don't know... I only used the 450R calipers and MasterCylinder since I sold my barely used stockers (by mistake). I've got 250R calipers and master cylinder on their way now... to go back on the bike (as I again had to remove the 450R units and sell them with a bike being parted out).

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I've NEVER seen this discussed: are the CR(F) calipers any better than XR's??

Are they "high performance" in any relevant way? Most folks assume they are, but i"ve never seen any claim that they are better/stronger/ more pistons, whatever.

????????

Anyone?

Bueller??? 👍

when i did my swap, I used my xr caliper and master cylinder. they were exactly (#'s matching) the same as the 2001 cr250 caliper and master cylinder that had come off of it. The xr400 was advertised as having CR style brakes.this is true for the front but not the for the back. The rear i know uses a different master cylinder, but i don't know about the rear caliper.

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