Brake pulsing/biting after disc machine/new pads

[NinjaBaby]

Hi All,

Took my front discs off the zxr250 today and got them machined and also put new EBC pads in and on the first run it is a complete disgrace. Really bad “pedal” (lever) pulse and looking at the discs and judging by the frequency of the pulse it appears that the pad is biting either on or off the cross drilled sections … looking at the discs it appears to be worse on one side since there is a different wear (or deposit of pad material) around the cross drill holes. Anyway, I couldn’t really do a proper bed in since it was wet and it would have chucked the bike with all the vibration if I had tried to stop hard.

I guess one possibility is that the dudes f%cked one or both the rotors when they machined them (also one of them is now slightly under spec … 3.4 when min is 3.5mm even though I asked him not to go passed min thickness). Personally, I wouldn’t have thought this would be a prob myself unless braking really hard thus leading to quicker fade.

Basically wondering if anyone has any suggestions … here are some of the courses of action I am considering tomorrow:

1. Try to bed them in a bit more and hope it gets better.
2. Get a dial gauge and check the runout of the rotors.
3. Pull off one of the calipers and secure it to see if it is just one of the rotors
4. Take it to the brake shop who did the machine (it is a car shop not sure they can do much with the rotors on the bike)
5. Take it to a bike mechanic and get them to check it out

Also wondering if anyone has had similar experience? Wishful thinking is it will just go away

Thx

NBH

[chameleon]

2. Get a dial gauge and check the runout of the rotors.
would be where i would start.

[bonester]

Check your headbearings too. Hopefully just them. (cheaper!)

[Glen]

What town are you in Ninjababy. If you're in Sydney there used to be an old guy at Picnic Point who operated out of his garage but was really good and cheap. I think he's still there.

I'd say the guys that did them have stuffed them for you.

[NinjaBaby]

Checked the head bearings, steering and wheel bearings when the wheel was off to remove the discs and everything seemed pretty tight.

Am in Melb so will grab a dial gauige today and check runout but also have a sneaking suspicion it is a dodgy caliper.

Thx,

NBH

[Gosling1]

sounds like a slightly warped disc to me.........you are only *slightly* under min. thickness, so this shouldn't be a problem ...yet.

If you go too far under minimum thickness, you start to run into problems with the 'piston' coming out too far, and not returning properly....

isn't this bike a single-disc front ??

[NinjaBaby]

I got put onto someone called Max at Planet Disc in Wantirna South who is apparently one of the few people who can machine floating discs properly and he thinks he might be able to salvage them and said no major problem even if they go down to 3.2mm so I am going to keep my fingers crossed and take the discs plus the pads down to him tomorrow morning.

Otherwise it is $240 per disc if they are cactus

Interesting comment about the piston coming out too far but the pads are new so if it is a prob at least wont show up for a while

P.S All zxr250's are twin disc AFAIK

Cheers,

NBH

[Gosling1]

sorry mate, your first post said 'xr250', I thought you had a chookchaser....

piston coming out is only a problem with too-skinny discs and really worn pads (seen it happen a couple of times......its not *that* common, just a bad combination to have at the same time...)

[NinjaBaby]

your first post said 'xr250', I thought you had a chookchaser....

Oops, didn't notice, have edited it now to avoid further confusion!