disk wear?

[Bill]

Hi All,

I have an `88 R100 with dual front disks and gave the brakes a safety 
check today.

Pads were fine but the disks were under spec, 3.7mm.  Clymer says they 
should not be less than 4mm.

My questions are:

1. Does that sound like normal wear for 43k miles?  (I know "depends", 
but generally?)

2. What is the thickness of a new replacement disk?  (just curious, 
outer edge of old disk reads 4.2mm)

3.  How soon should I plan on replacing the disks?  (and I assume new 
pads at same time.)

thanks,

Bill Bachman