If you're getting a bad vibration every time you apply the brakes, there's a good chance you've got a warped disc. But before you order [expensive] new ones, carry out some basic checks first.
- Lift the front end of your bike and turn the steering from lock-to-lock slowly, feeling for any roughness or looseness in the steering head bearings. Any play, or harsh movement, and it's time for new bearings. Get that sorted first.
- Are the brakes binding at all? Spin the wheel. You'll hear the pads rubbing the disc, but it should spin freely, not stop as soon as you let go of the wheel. If they're binding, you need to free up the pistons or overhaul the calipers. Binding brakes run hot and can lead to warped discs.
- Is there any play in the fork stanchions/sliders? There is always a minute amount of play to allow for easy movement but, if excessive, could cause a juddering through the handlebars. In fairness, this isn't so common and points one and two should be checked out first.
It's not always necessary to use a dial test indicator to check for runout. Sometimes you can see by eye how bad the disc is. Check out Bryan's CBR here.
No need for any measuring equipment here. The only aspect letting this bike down was the brakes, and after failing scrutineering on worn pads, he decided to splash out and get the wobble fixed too.
Metal Gear Brake Discs - seem pretty good.
Support the lower side of the wheel on blocks so that the disc doesn't get damaged. Tighten the bolts up evenly, and a little at a time. All 12 bolts holding the original discs on were actually quite loose. Hardly any pressure was needed on the ratchet to undo them. Well worth doing a bolt check on your bike every now and again.
Now's a good time to clean up the pistons with soapy water and blow out any dirty residue. I always pump them out slightly first to make sure no dirt is forced back past the seals. Once you can see a clean section on the piston, hold it and force the others out. (Don't keep pumping them until one drops out!)
Wheel back in and tightened, calipers refitted, all that's left is to flush the brake fluid. Good job too, the stuff in there looked like Scrumpy Cider.
All finished, time to check it again.
What a difference on the road; the brakes are superb now. No judder, and much stronger than before as a result of discs that are completely flat/square, and brake fluid that is moisture-free. I want to get it back on the track and see if I can knock another second off!
Metal Gear - an opinion.
Pretty bloody good in fairness. A lot cheaper than buying OEM, and they look good too. Only time will tell for sure but, with a years warranty, any issues should come to light in time.
I've never been a fan of aftermarket stuff for bikes - there's just too much ropey shit out there - but I'm happy to say these seem to be the real deal.