Disc run out

[kiwiz]

Hi,
trying to improve the braking on the front of the J someone suggested I measure the disc run out.

One disc has run out (wobble from one extreme to another?) of .13mm the other .25mm. According to Clymer they are scrap at .3mm. Doing this measurement was a bit tricker than I imagined as finding a circumference which did not have a intersecting hole was challenging

Would this explain the amount of ineffective lever travel before the pads bite? What are the chances of fixing or getting replacements for the rotors?can these be machined flat?

[Iain marshall]

just a quick question have you had the discs off wheels for any reason as i have came across a problem with dirt/paint between wheel and the disc causing a run out,in my case all i had to do was clean up the wheel where the disc mounts.Hope yours is as easy as that

[kiwiz]

Nope they have never been off the wheel

[Rich]

Rotate them around one hole at a time to see if runout improves. Check all bolts are tightened correctly and to the correct torque.Minimum disk thickness is 4.5mm. Yes you can have them skimmed down to that BUT as the thickness is reduced they will warp easier. Evaluate the cost of having them skinmmed to the cost of new disks.

0.3mm max runout is Kawa figure as well. How much ineffective travel - I would expect this will not be the sole cause of your problems.

[Pigford]

kiwiz, take a look at my "Bleedin brake problem solved" thread on page 2 of Bike Help!
This may help

[kiwiz]

Does anyone know the function of the plastic sleeves which are on the lower caliper sliding pins on the J front brake calipers?

I have been suspicious for some time that these were causing the excess lever movement on my J. Rather than sliding freely they seem to bind as evidenced by the need to use pliers to get the sliders out!

I assumed they were some anti rattle mechanism so I have removed them and the brakes feel much more solid with free lever travel much reduced. However I am quite reluctant to take things off my bike the function of which I am unsure. The Japs must have put them there for a reason. Should I replace them or leave out as now?

Whilst the brakes feel much better I now have have a mystery click click click noise from the brakes as the wheel rotates, so maybe these were the anti click sleeves!? This noise was not there before.