My front discs have a tiny warble when applied hard. Can these discs be machined? Mine are 4.45mm and minimum thickness is 3.5mm. I'm putting in new EBC pads, and would prefer to machine versus replacing ( pricey!). Thanks for your help.

 

First, let me qualify, my comments. If you are using this for a track-bike
and warpage is the issue, imo, replacement is the proper course. The bike
is being run constantly too close to tolerances, to be marginal on such an
important system. Mass also equates to ability to absorb/dissipate heat.

Street riding doesn't put nearly the constant stress/load on the system.
So it should be a reasonable choice for that type application.
That said...

You've got the tolerance, as far as thickness. However, you need to use a dial-mic
and check the run-out, as well. That will tell you'll still have enough left after you
have them milled flat. If the run-out is greater than .5mm, then you'll be wasting
your time/money, because the final result will be less than the OEM spec'ed 3.5mm.

Checking the run-out will also tell you if that IS the problem. The most common cause
of brake flutter, in my experience, is the calipers being frozen on the hanger-pins.
Not rotor-disc warpage.

Warpage is usually a function of running worn-out brake-pads and/or frozen pistons.
So if that doesn't apply in your case, you probably want inspect the rest of the
system, before shelling out for the machining.

Good luck, Ern

 

I appreciate the well thought response! She's a street rider only, brake pins etc. are good as well as fork bushings ( fork guts and headset new). I don't have a dial-mic so will check for warpage when the wheels come off. Likely this week when the new rubber gets fitted, I'll keep you posted.

 

If you have a large plate of granite/glass, lay the rotor on that and run a feeler-guage
around the rim. the biggest one that will fit ANYWHERE under the disk is one half of
the run-out. So if you double the dimension of that feeler-guage, it will give you your
run-out. it's half because you have to mill both side of the disk, one side to get rid of the high, one side to get rid of the low.

One other possibility...the wheel bearings themselves. The braking may just be
getting them to exhibit the first signs. But I'm reaching on that one, I just like to
cover the bases.

Good luck, Ern

 

Good afternoon sea.., it was know of the 87-88 disks to warp when approching 4.5, this is why they changed the thickness on gen 2 and 3. I got myself gen2-3 brakes on mine, fitted no problem, better go that way then trying, you can get a cheap pair on ebay.

Alsoas song as you are taking off the wheels change the bearing as well, since the original ones where sensitive to water , especially if you clean your wheel with a high pressure system.