Mountain bike suspension forks I am thinking about changing out the worn suspension forks on my quite old Specialized Stumpjumper which has rim brakes. I found some forks online (RockShox 30 Silver TK Fork: 26") and some of the specs listed I don't understand...
 - Brake type: Post mount 160  ??
 - Axle to crown length:487  ??
 - Steerer tube length: 265  ??
Pretty sure it will fit, but want to be positve before I order...
Dan
Brake Type: Post mount 160 is mounting points for a disc caliper and
160mm disk (You can go to a bigger disk with adapters, but cannot go
smaller than 160 with this fork) 
Axle to Crown:487 - this is the fork length from axle to crown.
Ideally you would match the existing for within say 10 mm, as it
changes the bike geometry is the difference is too much. If
increasing the fork travel, you may want to increase the crown/axle
length to accomade more sag. 
Steerer tube length -   the length of the steerer tube - the bit the
handles bars bolt onto. This is normally cut shorter to suit the
bike, make sure the length is not short than you existing fork.


These forks do not have mounts for rim brakes, so are not suitable unless you upgrade to disk brakes, which requires a new wheel as well as brakes. 

What you must do is go for a 1/8" straight steer fork. The other thing to match as closely as practical is the axle to crown measurement, as this maintains the geometry. 

If you upgrade the wheel and front brakes to disk, you have far more options. If you  do decide to upgrade to the wheel, you need to decide axle and if to go boost or not, along with wheel size.  You could probably go to 27.5" without upsetting the geometry too much, especially if you go to a shorter travel fork. Obviously this option adds significant cost

Unfortunately replacement forks for older bikes are getting hard to come by, 26", rightly or wrongly. has been consigned to the history books. While we do not do product recommendations, you are more likely to find a compatible fork from a lower end manufacturer such as Suntour (e.g. the Paragon - short travel but will bolt straight on). 

In the end it may not be economical to do this. Consider sourcing a used fork from the late 2000's - however finding one that is not worn out will be hard.